High-throughput sequencing of hematologic malignancies and other cancers has revealed recurrent mis-sense mutations of genes encoding pre-mRNA splicing factors. The essential splicing factor U2AF2 recognizes a polypyrimidine-tract splice-site signal and initiates spliceosome assembly. Here, we investigate representative, acquired U2AF2 mutations, namely N196K or G301D amino acid substitutions associated with leukemia or solid tumors, respectively. We determined crystal structures of the wild-type (WT) compared with N196K- or G301D-substituted U2AF2 proteins, each bound to a prototypical AdML polypyrimidine tract, at 1.5, 1.4, or 1.7 Å resolutions. The N196K residue appears to stabilize the open conformation of U2AF2 with an inter-RNA recognition motif hydrogen bond, in agreement with an increased apparent RNA-binding affinity of the N196K-substituted protein. The G301D residue remains in a similar position as the WT residue, where unfavorable proximity to the RNA phosphodiester could explain the decreased RNA-binding affinity of the G301D-substituted protein. We found that expression of the G301D-substituted U2AF2 protein reduces splicing of a minigene transcript carrying prototypical splice sites. We further show that expression of either N196K- or G301D-substituted U2AF2 can subtly alter splicing of representative endogenous transcripts, despite the presence of endogenous, WT U2AF2 such as would be present in cancer cells. Altogether, our results demonstrate that acquired U2AF2 mutations such as N196K and G301D are capable of dysregulating gene expression for neoplastic transformation.

The bacterial enhancer-binding protein (bEBP) FlrC, controls motility and colonization of Vibrio cholerae by regulating the transcription of class-III flagellar genes in σ54-dependent manner. However, the mechanism by which FlrC regulates transcription is not fully elucidated. Although, most bEBPs require nucleotides to stimulate the oligomerization necessary for function, our previous study showed that the central domain of FlrC (FlrCC) forms heptamer in a nucleotide-independent manner. Furthermore, heptameric FlrCC binds ATP in “cis-mediated” style without any contribution from sensor I motif 285REDXXYR291 of the trans protomer. This atypical ATP binding raises the question of whether heptamerization of FlrC is solely required for transcription regulation, or if it is also critical for ATPase activity. ATPase assays and size exclusion chromatography of the trans-variants FlrCC-Y290A and FlrCC-R291A showed destabilization of heptameric assembly with concomitant abrogation of ATPase activity. Crystal structures showed that in the cis-variant FlrCC-R349A drastic shift of Walker A encroached ATP-binding site, whereas the site remained occupied by ADP in FlrCC-Y290A. We postulated that FlrCC heptamerizes through concentration-dependent cooperativity for maximal ATPase activity and upon heptamerization, packing of trans-acting Tyr290 against cis-acting Arg349 compels Arg349 to maintain proper conformation of Walker A. Finally, a Trp quenching study revealed binding of cyclic-di-GMP with FlrCC. Excess cyclic-di-GMP repressed ATPase activity of FlrCC through destabilization of heptameric assembly, especially at low concentration of protein. Systematic phylogenetic analysis allowed us to propose similar regulatory mechanisms for FlrCs of several Vibrio species and a set of monotrichous Gram-negative bacteria.

Investigations of bacterial resistance strategies can aid in the development of new antimicrobial drugs as a countermeasure to the increasing worldwide prevalence of bacterial antibiotic resistance. One such strategy involves the TipA class of transcription factors, which constitute minimal autoregulated multidrug resistance (MDR) systems against diverse antibiotics. However, we have insufficient information regarding how antibiotic binding induces transcriptional activation to design molecules that could interfere with this process. To learn more, we determined the crystal structure of SkgA from Caulobacter crescentus as a representative TipA protein. We identified an unexpected spatial orientation and location of the antibiotic-binding TipAS effector domain in the apo state. We observed that the α6–α7 region of the TipAS domain, which is canonically responsible for forming the lid of antibiotic-binding cleft to tightly enclose the bound antibiotic, is involved in the dimeric interface and stabilized via interaction with the DNA-binding domain in the apo state. Further structural and biochemical analyses demonstrated that the unliganded TipAS domain sterically hinders promoter DNA binding but undergoes a remarkable conformational shift upon antibiotic binding to release this autoinhibition via a switch of its α6–α7 region. Hence, the promoters for MDR genes including tipA and RNA polymerases become available for transcription, enabling efficient antibiotic resistance. These insights into the molecular mechanism of activation of TipA proteins advance our understanding of TipA proteins, as well as bacterial MDR systems, and may provide important clues to block bacterial resistance.

Aspergillus terreus is an allergenic fungus, in addition to causing infections in both humans and plants. However, the allergens in this fungus are still unknown, limiting the development of diagnostic and therapeutic strategies. We used a proteomic approach to search for allergens, identifying 16 allergens based on two-dimensional immunoblotting with A. terreus susceptible patient sera. We further characterized triose-phosphate isomerase (Asp t 36), one of the dominant IgE (IgE)-reactive proteins. The gene was cloned and expressed in Escherichia coli. Phylogenetic analysis showed Asp t 36 to be highly conserved with close similarity to the triose-phosphate isomerase protein sequence from Dermatophagoides farinae, an allergenic dust mite. We identified four immunodominant epitopes using synthetic peptides, and mapped them on a homology-based model of the tertiary structure of Asp t 36. Among these, two were found to create a continuous surface patch on the 3D structure, rendering it an IgE-binding hotspot. Biophysical analysis indicated that Asp t 36 shows similar secondary structure content and temperature sensitivity with other reported triose-phosphate isomerase allergens. In vivo studies using a murine model displayed that the recombinant Asp t 36 was able to stimulate airway inflammation, as demonstrated by an influx of eosinophils, goblet cell hyperplasia, elevated serum Igs, and induction of Th2 cytokines. Collectively, our results reveal the immunogenic property of Asp t 36, a major allergen from A. terreus, and define a new fungal allergen more broadly. This allergen could serve as a potent candidate for investigating component resolved diagnosis and immunotherapy.

Bacterial low-copy-number plasmids require partition (par) systems to ensure their stable inheritance by daughter cells. In general, these systems consist of three components: a centromeric DNA sequence, a centromere-binding protein and a nucleotide hydrolase that polymerizes and functions as a motor. Type III systems, however, segregate plasmids using three proteins: the FtsZ/tubulin-like GTPase TubZ, the centromere-binding protein TubR and the MerR-like transcriptional regulator TubY. Although the TubZ filament is sufficient to transport the TubR-centromere complex in vitro, TubY is still necessary for the stable maintenance of the plasmid. TubY contains an N-terminal DNA-binding helix-turn-helix motif and a C-terminal coiled-coil followed by a cluster of lysine residues. This study determined the crystal structure of the C-terminal domain of TubY from the Bacillus cereus pXO1-like plasmid and showed that it forms a tetrameric parallel four-helix bundle that differs from the typical MerR family proteins with a dimeric anti-parallel coiled-coil. Biochemical analyses revealed that the C-terminal tail with the conserved lysine cluster helps TubY to stably associate with the TubR-centromere complex as well as to nonspecifically bind DNA. Furthermore, this C-terminal tail forms an amphipathic helix in the presence of lipids but must oligomerize to localize the protein to the membrane in vivo. Taken together, these data suggest that TubY is a component of the nucleoprotein complex within the partitioning machinery, and that lipid membranes act as mediators of type III systems.

Broad-specificity glycoside hydrolases (GHs) contribute to plant biomass hydrolysis by degrading a diverse range of polysaccharides, making them useful catalysts for renewable energy and biocommodity production. Discovery of new GHs with improved kinetic parameters or more tolerant substrate-binding sites could increase the efficiency of renewable bioenergy production even further. GH5 has over 50 subfamilies exhibiting selectivities for reaction with β-(1,4)–linked oligo- and polysaccharides. Among these, subfamily 4 (GH5_4) contains numerous broad-selectivity endoglucanases that hydrolyze cellulose, xyloglucan, and mixed-linkage glucans. We previously surveyed the whole subfamily and found over 100 new broad-specificity endoglucanases, although the structural origins of broad specificity remained unclear. A mechanistic understanding of GH5_4 substrate specificity would help inform the best protein design strategies and the most appropriate industrial application of broad-specificity endoglucanases. Here we report structures of 10 new GH5_4 enzymes from cellulolytic microbes and characterize their substrate selectivity using normalized reducing sugar assays and MS. We found that GH5_4 enzymes have the highest catalytic efficiency for hydrolysis of xyloglucan, glucomannan, and soluble β-glucans, with opportunistic secondary reactions on cellulose, mannan, and xylan. The positions of key aromatic residues determine the overall reaction rate and breadth of substrate tolerance, and they contribute to differences in oligosaccharide cleavage patterns. Our new composite model identifies several critical structural features that confer broad specificity and may be readily engineered into existing industrial enzymes. We demonstrate that GH5_4 endoglucanases can have broad specificity without sacrificing high activity, making them a valuable addition to the biomass deconstruction toolset.

Highly engineered phytases, which sequentially hydrolyze the hexakisphosphate ester of inositol known as phytic acid, are routinely added to the feeds of monogastric animals to improve phosphate bioavailability. New phytases are sought as starting points to further optimize the rate and extent of dephosphorylation of phytate in the animal digestive tract. Multiple inositol polyphosphate phosphatases (MINPPs) are clade 2 histidine phosphatases (HP2P) able to carry out the stepwise hydrolysis of phytate. MINPPs are not restricted by a strong positional specificity making them attractive targets for development as feed enzymes. Here, we describe the characterization of a MINPP from the Gram-positive bacterium Bifidobacterium longum (BlMINPP). BlMINPP has a typical HP2P-fold but, unusually, possesses a large α-domain polypeptide insertion relative to other MINPPs. This insertion, termed the U-loop, spans the active site and contributes to substrate specificity pockets underpopulated in other HP2Ps. Mutagenesis of U-loop residues reveals its contribution to enzyme kinetics and thermostability. Moreover, four crystal structures of the protein along the catalytic cycle capture, for the first time in an HP2P, a large ligand-driven α-domain motion essential to allow substrate access to the active site. This motion recruits residues both downstream of a molecular hinge and on the U-loop to participate in specificity subsites, and mutagenesis identified a mobile lysine residue as a key determinant of positional specificity of the enzyme. Taken together, these data provide important new insights to the factors determining stability, substrate recognition, and the structural mechanism of hydrolysis in this industrially important group of enzymes.

Identification of antibody-binding epitopes is crucial to understand immunological mechanisms. It is of particular interest for allergenic proteins with high cross-reactivity as observed in the lipid transfer protein (LTP) syndrome, which is characterized by severe allergic reactions. Art v 3, a pollen LTP from mugwort, is frequently involved in this cross-reactivity, but no antibody-binding epitopes have been determined so far. To reveal human IgE-binding regions of Art v 3, we produced three murine high-affinity mAbs, which showed 70–90% coverage of the allergenic epitopes from mugwort pollen–allergic patients. As reliable methods to determine structural epitopes with tightly interacting intact antibodies under native conditions are lacking, we developed a straightforward NMR approach termed hydrogen/deuterium exchange memory (HDXMEM). It relies on the slow exchange between the invisible antigen-mAb complex and the free 15N-labeled antigen whose 1H-15N correlations are detected. Due to a memory effect, changes of NH protection during antibody binding are measured. Differences in H/D exchange rates and analyses of mAb reactivity to homologous LTPs revealed three structural epitopes: two partially cross-reactive regions around α-helices 2 and 4 as well as a novel Art v 3–specific epitope at the C terminus. Protein variants with exchanged epitope residues confirmed the antibody-binding sites and revealed strongly reduced IgE reactivity. Using the novel HDXMEM for NMR epitope mapping allowed identification of the first structural epitopes of an allergenic pollen LTP. This knowledge enables improved cross-reactivity prediction for patients suffering from LTP allergy and facilitates design of therapeutics.

Systemic antibody light chains (AL) amyloidosis is characterized by deposition of amyloid fibrils derived from a particular antibody light chain. Cardiac involvement is a major risk factor for mortality. Using MAS solid-state NMR, we studied the fibril structure of a recombinant light chain fragment corresponding to the fibril protein from patient FOR005, together with fibrils formed by protein sequence variants that are derived from the closest germline (GL) sequence. Both analyzed fibril structures were seeded with ex-vivo amyloid fibrils purified from the explanted heart of this patient. We find that residues 11-42 and 69-102 adopt β-sheet conformation in patient protein fibrils. We identify arginine-49 as a key residue that forms a salt bridge to aspartate-25 in the patient protein fibril structure. In the germline sequence, this residue is replaced by a glycine. Fibrils from the GL protein and from the patient protein harboring the single point mutation R49G can be both heterologously seeded using patient ex-vivo fibrils. Seeded R49G fibrils show an increased heterogeneity in the C-terminal residues 80-102, which is reflected by the disappearance of all resonances of these residues. By contrast, residues 11-42 and 69-77, which are visible in the MAS solid-state NMR spectra, show 13Cα chemical shifts that are highly like patient fibrils. The mutation R49G thus induces a conformational heterogeneity at the C terminus in the fibril state, whereas the overall fibril topology is retained. These findings imply that patient mutations in FOR005 can stabilize the fibril structure.

Replication protein A (RPA) is a eukaryotic ssDNA-binding protein and contains three subunits: RPA70, RPA32, and RPA14. Phosphorylation of the N-terminal region of the RPA32 subunit plays an essential role in DNA metabolism in processes such as replication and damage response. Phosphorylated RPA32 (pRPA32) binds to RPA70 and possibly regulates the transient RPA70-Bloom syndrome helicase (BLM) interaction to inhibit DNA resection. However, the structural details and determinants of the phosphorylated RPA32–RPA70 interaction are still unknown. In this study, we provide molecular details of the interaction between RPA70 and a mimic of phosphorylated RPA32 (pmRPA32) using fluorescence polarization and NMR analysis. We show that the N-terminal domain of RPA70 (RPA70N) specifically participates in pmRPA32 binding, whereas the unphosphorylated RPA32 does not bind to RPA70N. Our NMR data revealed that RPA70N binds pmRPA32 using a basic cleft region. We also show that at least 6 negatively charged residues of pmRPA32 are required for RPA70N binding. By introducing alanine mutations into hydrophobic positions of pmRPA32, we found potential points of contact between RPA70N and the N-terminal half of pmRPA32. We used this information to guide docking simulations that suggest the orientation of pmRPA32 in complex with RPA70N. Our study demonstrates detailed features of the domain-domain interaction between RPA70 and RPA32 upon phosphorylation. This result provides insight into how phosphorylation tunes transient bindings between RPA and its partners in DNA resection.

The dimeric ectonucleotidase CD73 catalyzes the hydrolysis of AMP at the cell surface to form adenosine, a potent suppressor of the immune response. Blocking CD73 activity in the tumor microenvironment can have a beneficial effect on tumor eradication and is a promising approach for cancer therapy. Biparatopic antibodies binding different regions of CD73 may be a means to antagonize its enzymatic activity. A panel of biparatopic antibodies representing the pairwise combination of 11 parental monoclonal antibodies against CD73 was generated by Fab-arm exchange. Nine variants vastly exceeded the potency of their parental antibodies with ≥90% inhibition of activity and subnanomolar EC50 values. Pairing the Fabs of parents with nonoverlapping epitopes was both sufficient and necessary whereas monovalent antibodies were poor inhibitors. Some parental antibodies yielded potent biparatopics with multiple partners, one of which (TB19) producing the most potent. The structure of the TB19 Fab with CD73 reveals that it blocks alignment of the N- and C-terminal CD73 domains necessary for catalysis. A separate structure of CD73 with a Fab (TB38) which complements TB19 in a particularly potent biparatopic shows its binding to a nonoverlapping site on the CD73 N-terminal domain. Structural modeling demonstrates a TB19/TB38 biparatopic antibody would be unable to bind the CD73 dimer in a bivalent manner, implicating crosslinking of separate CD73 dimers in its mechanism of action. This ability of a biparatopic antibody to both crosslink CD73 dimers and fix them in an inactive conformation thus represents a highly effective mechanism for the inhibition of CD73 activity.

Sirtuin 6, SIRT6, is critical for both glucose and lipid homeostasis and is involved in maintaining genomic stability under conditions of oxidative DNA damage such as those observed in age-related diseases. There is an intense search for modulators of SIRT6 activity, however, not many specific activators have been reported. Long acyl-chain fatty acids have been shown to increase the weak in vitro deacetylase activity of SIRT6 but this effect is modest at best. Herein we report that electrophilic nitro-fatty acids (nitro-oleic acid and nitro-conjugated linoleic acid) potently activate SIRT6. Binding of the nitro-fatty acid to the hydrophobic crevice of the SIRT6 active site exerted a moderate activation (2-fold at 20 μm), similar to that previously reported for non-nitrated fatty acids. However, covalent Michael adduct formation with Cys-18, a residue present at the N terminus of SIRT6 but absent from other isoforms, induced a conformational change that resulted in a much stronger activation (40-fold at 20 μm). Molecular modeling of the resulting Michael adduct suggested stabilization of the co-substrate and acyl-binding loops as a possible additional mechanism of SIRT6 activation by the nitro-fatty acid. Importantly, treatment of cells with nitro-oleic acid promoted H3K9 deacetylation, whereas oleic acid had no effect. Altogether, our results show that nitrated fatty acids can be considered a valuable tool for specific SIRT6 activation, and that SIRT6 should be considered as a molecular target for in vivo actions of these anti-inflammatory nitro-lipids.

Members of the B-cell lymphoma (BCL-2) protein family regulate mitochondrial outer membrane permeabilization (MOMP), a phenomenon in which mitochondria become porous and release death-propagating complexes during the early stages of apoptosis. Pro-apoptotic BCL-2 proteins oligomerize at the mitochondrial outer membrane during MOMP, inducing pore formation. Of current interest are endogenous factors that can inhibit pro-apoptotic BCL-2 mitochondrial outer membrane translocation and oligomerization. A mitochondrial-derived peptide, Humanin (HN), was reported being expressed from an alternate ORF in the mitochondrial genome and inhibiting apoptosis through interactions with the pro-apoptotic BCL-2 proteins. Specifically, it is known to complex with BAX and BID. We recently reported the fibrillation of HN and BAX into β-sheets. Here, we detail the fibrillation between HN and BID. These fibers were characterized using several spectroscopic techniques, protease fragmentation with mass analysis, and EM. Enhanced fibrillation rates were detected with rising temperatures or pH values and the presence of a detergent. BID fibers are similar to those produced using BAX; however, the structures differ in final conformations of the BCL-2 proteins. BID fibers display both types of secondary structure in the fiber, whereas BAX was converted entirely to β-sheets. The data show that two distinct segments of BID are incorporated into the fiber structure, whereas other portions of BID remain solvent-exposed and retain helical structure. Similar analyses show that anti-apoptotic BCL-xL does not form fibers with humanin. These results support a general mechanism of sequestration of pro-apoptotic BCL-2 proteins into fibers by HN to inhibit MOMP.

Abnormal changes of neuronal Tau protein, such as phosphorylation and aggregation, are considered hallmarks of cognitive deficits in Alzheimer's disease. Abnormal phosphorylation is thought to precede aggregation and therefore to promote aggregation, but the nature and extent of phosphorylation remain ill-defined. Tau contains ∼85 potential phosphorylation sites, which can be phosphorylated by various kinases because the unfolded structure of Tau makes them accessible. However, methodological limitations (e.g. in MS of phosphopeptides, or antibodies against phosphoepitopes) led to conflicting results regarding the extent of Tau phosphorylation in cells. Here we present results from a new approach based on native MS of intact Tau expressed in eukaryotic cells (Sf9). The extent of phosphorylation is heterogeneous, up to ∼20 phosphates per molecule distributed over 51 sites. The medium phosphorylated fraction Pm showed overall occupancies of ∼8 Pi (± 5) with a bell-shaped distribution; the highly phosphorylated fraction Ph had 14 Pi (± 6). The distribution of sites was highly asymmetric (with 71% of all P-sites in the C-terminal half of Tau). All sites were on Ser or Thr residues, but none were on Tyr. Other known posttranslational modifications were near or below our detection limit (e.g. acetylation, ubiquitination). These findings suggest that normal cellular Tau shows a remarkably high extent of phosphorylation, whereas other modifications are nearly absent. This implies that abnormal phosphorylations at certain sites may not affect the extent of phosphorylation significantly and do not represent hyperphosphorylation. By implication, the pathological aggregation of Tau is not likely a consequence of high phosphorylation.

Programmed ribosomal frameshifting (PRF) is a mechanism used by arteriviruses like porcine reproductive and respiratory syndrome virus (PRRSV) to generate multiple proteins from overlapping reading frames within its RNA genome. PRRSV employs −1 PRF directed by RNA secondary and tertiary structures within its viral genome (canonical PRF), as well as a noncanonical −1 and −2 PRF that are stimulated by the interactions of PRRSV nonstructural protein 1β (nsp1β) and host protein poly(C)-binding protein (PCBP) 1 or 2 with the viral genome. Together, nsp1β and one of the PCBPs act as transactivators that bind a C-rich motif near the shift site to stimulate −1 and −2 PRF, thereby enabling the ribosome to generate two frameshift products that are implicated in viral immune evasion. How nsp1β and PCBP associate with the viral RNA genome remains unclear. Here, we describe the purification of the nsp1β:PCBP2:viral RNA complex on a scale sufficient for structural analysis using small-angle X-ray scattering and stochiometric analysis by analytical ultracentrifugation. The proteins associate with the RNA C-rich motif as a 1:1:1 complex. The monomeric form of nsp1β within the complex differs from previously reported homodimer identified by X-ray crystallography. Functional analysis of the complex via mutational analysis combined with RNA-binding assays and cell-based frameshifting reporter assays reveal a number of key residues within nsp1β and PCBP2 that are involved in complex formation and function. Our results suggest that nsp1β and PCBP2 both interact directly with viral RNA during formation of the complex to coordinate this unusual PRF mechanism.

The life cycle of malaria parasites in both their mammalian host and mosquito vector consists of multiple developmental stages that ensure proper replication and progeny survival. The transition between these stages is fueled by nutrients scavenged from the host and fed into specialized metabolic pathways of the parasite. One such pathway is used by Plasmodium falciparum, which causes the most severe form of human malaria, to synthesize its major phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. Much is known about the enzymes involved in the synthesis of these phospholipids, and recent advances in genetic engineering, single-cell RNA-Seq analyses, and drug screening have provided new perspectives on the importance of some of these enzymes in parasite development and sexual differentiation and have identified targets for the development of new antimalarial drugs. This Minireview focuses on two phospholipid biosynthesis enzymes of P. falciparum that catalyze phosphoethanolamine transmethylation (PfPMT) and phosphatidylserine decarboxylation (PfPSD) during the blood stages of the parasite. We also discuss our current understanding of the biochemical, structural, and biological functions of these enzymes and highlight efforts to use them as antimalarial drug targets.

Zinc is a critical element for insulin storage in the secretory granules of pancreatic beta cells. The islet-specific zinc transporter ZnT8 mediates granular sequestration of zinc ions. A genetic variant of human ZnT8 arising from a single nonsynonymous nucleotide change contributes to increased susceptibility to type-2 diabetes (T2D), but it remains unclear how the high risk variant (Arg-325), which is also a higher frequency (>50%) allele, is correlated with zinc transport activity. Here, we compared the activity of Arg-325 with that of a low risk ZnT8 variant (Trp-325). The Arg-325 variant was found to be more active than the Trp-325 form following induced expression in HEK293 cells. We further examined the functional consequences of changing lipid conditions to mimic the impact of lipid remodeling on ZnT8 activity during insulin granule biogenesis. Purified ZnT8 variants in proteoliposomes exhibited more than 4-fold functional tunability by the anionic phospholipids, lysophosphatidylcholine and cholesterol. Over a broad range of permissive lipid compositions, the Arg-325 variant consistently exhibited accelerated zinc transport kinetics versus the Trp-form. In agreement with the human genetic finding that rare loss-of-function mutations in ZnT8 are associated with reduced T2D risk, our results suggested that the common high risk Arg-325 variant is hyperactive, and thus may be targeted for inhibition to reduce T2D risk in the general populations.

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Viral infection is one environmental factor that may contribute to the initiation of pancreatic β-cell destruction during the development of autoimmune diabetes. Picornaviruses, such as encephalomyocarditis virus (EMCV), induce a pro-inflammatory response in islets leading to local production of cytokines, such as IL-1, by resident islet leukocytes. Furthermore, IL-1 is known to stimulate β-cell expression of iNOS and production of the free radical nitric oxide. The purpose of this study was to determine whether nitric oxide contributes to the β-cell response to viral infection. We show that nitric oxide protects β-cells against virally mediated lysis by limiting EMCV replication. This protection requires low micromolar, or iNOS-derived, levels of nitric oxide. At these concentrations nitric oxide inhibits the Krebs enzyme aconitase and complex IV of the electron transport chain. Like nitric oxide, pharmacological inhibition of mitochondrial oxidative metabolism attenuates EMCV-mediated β-cell lysis by inhibiting viral replication. These findings provide novel evidence that cytokine signaling in β-cells functions to limit viral replication and subsequent β-cell lysis by attenuating mitochondrial oxidative metabolism in a nitric oxide–dependent manner.

The synthesis of cholesterol requires more than 20 enzymes, many of which are intricately regulated. Post-translational control of these enzymes provides a rapid means for modifying flux through the pathway. So far, several enzymes have been shown to be rapidly degraded through the ubiquitin–proteasome pathway in response to cholesterol and other sterol intermediates. Additionally, several enzymes have their activity altered through phosphorylation mechanisms. Most work has focused on the two rate-limiting enzymes: 3-hydroxy-3-methylglutaryl CoA reductase and squalene monooxygenase. Here, we review current literature in the area to define some common themes in the regulation of the entire cholesterol synthesis pathway. We highlight the rich variety of inputs controlling each enzyme, discuss the interplay that exists between regulatory mechanisms, and summarize findings that reveal an intricately coordinated network of regulation along the cholesterol synthesis pathway. We provide a roadmap for future research into the post-translational control of cholesterol synthesis, and no doubt the road ahead will reveal further twists and turns for this fascinating pathway crucial for human health and disease.

The development of a chronic, low-grade inflammation originating from adipose tissue in obese subjects is widely recognized to induce insulin resistance, leading to the development of type 2 diabetes. The adipose tissue microenvironment drives specific metabolic reprogramming of adipose tissue macrophages, contributing to the induction of tissue inflammation. Uncoupling protein 2 (UCP2), a mitochondrial anion carrier, is thought to separately modulate inflammatory and metabolic processes in macrophages and is up-regulated in macrophages in the context of obesity and diabetes. Here, we investigate the role of UCP2 in macrophage activation in the context of obesity-induced adipose tissue inflammation and insulin resistance. Using a myeloid-specific knockout of UCP2 (Ucp2ΔLysM), we found that UCP2 deficiency significantly increases glycolysis and oxidative respiration, both unstimulated and after inflammatory conditions. Strikingly, fatty acid loading abolished the metabolic differences between Ucp2ΔLysM macrophages and their floxed controls. Furthermore, Ucp2ΔLysM macrophages show attenuated pro-inflammatory responses toward Toll-like receptor-2 and -4 stimulation. To test the relevance of macrophage-specific Ucp2 deletion in vivo, Ucp2ΔLysM and Ucp2fl/fl mice were rendered obese and insulin resistant through high-fat feeding. Although no differences in adipose tissue inflammation or insulin resistance was found between the two genotypes, adipose tissue macrophages isolated from diet-induced obese Ucp2ΔLysM mice showed decreased TNFα secretion after ex vivo lipopolysaccharide stimulation compared with their Ucp2fl/fl littermates. Together, these results demonstrate that although UCP2 regulates both metabolism and the inflammatory response of macrophages, its activity is not crucial in shaping macrophage activation in the adipose tissue during obesity-induced insulin resistance.

Pectins are a major dietary nutrient source for the human gut microbiota. The prominent gut microbe Bacteroides thetaiotaomicron was recently shown to encode the founding member (BT1017) of a new family of pectin methylesterases essential for the metabolism of the complex pectin rhamnogalacturonan-II (RG-II). However, biochemical and structural knowledge of this family is lacking. Here, we showed that BT1017 is critical for the metabolism of an RG-II–derived oligosaccharide ΔBT1017oligoB generated by a BT1017 deletion mutant (ΔBT1017) during growth on carbohydrate extract from apple juice. Structural analyses of ΔBT1017oligoB using a combination of enzymatic, mass spectrometric, and NMR approaches revealed that it is a bimethylated nonaoligosaccharide (GlcA-β1,4-(2-O-Me-Xyl-α1,3)-Fuc-α1,4-(GalA-β1,3)-Rha-α1,3-Api-β1,2-(Araf-α1,3)-(GalA-α1,4)-GalA) containing components of the RG-II backbone and its side chains. We showed that the catalytic module of BT1017 adopts an α/β-hydrolase fold, consisting of a central twisted 10-stranded β-sheet sandwiched by several α-helices. This constitutes a new fold for pectin methylesterases, which are predominantly right-handed β-helical proteins. Bioinformatic analyses revealed that the family is dominated by sequences from prominent genera of the human gut microbiota, including Bacteroides and Prevotella. Our re-sults not only highlight the critical role played by this family of enzymes in pectin metabolism but also provide new insights into the molecular basis of the adaptation of B. thetaiotaomicron to the human gut.

Pyrroline-5-carboxylate reductase 1 (PYCR1) catalyzes the biosynthetic half-reaction of the proline cycle by reducing Δ1-pyrroline-5-carboxylate (P5C) to proline through the oxidation of NAD(P)H. Many cancers alter their proline metabolism by up-regulating the proline cycle and proline biosynthesis, and knockdowns of PYCR1 lead to decreased cell proliferation. Thus, evidence is growing for PYCR1 as a potential cancer therapy target. Inhibitors of cancer targets are useful as chemical probes for studying cancer mechanisms and starting compounds for drug discovery; however, there is a notable lack of validated inhibitors for PYCR1. To fill this gap, we performed a small-scale focused screen of proline analogs using X-ray crystallography. Five inhibitors of human PYCR1 were discovered: l-tetrahydro-2-furoic acid, cyclopentanecarboxylate, l-thiazolidine-4-carboxylate, l-thiazolidine-2-carboxylate, and N-formyl l-proline (NFLP). The most potent inhibitor was NFLP, which had a competitive (with P5C) inhibition constant of 100 μm. The structure of PYCR1 complexed with NFLP shows that inhibitor binding is accompanied by conformational changes in the active site, including the translation of an α-helix by 1 Å. These changes are unique to NFLP and enable additional hydrogen bonds with the enzyme. NFLP was also shown to phenocopy the PYCR1 knockdown in MCF10A H-RASV12 breast cancer cells by inhibiting de novo proline biosynthesis and impairing spheroidal growth. In summary, we generated the first validated chemical probe of PYCR1 and demonstrated proof-of-concept for screening proline analogs to discover inhibitors of the proline cycle.

Environmental factors, such as viral infection, are proposed to play a role in the initiation of autoimmune diabetes. In response to encephalomyocarditis virus (EMCV) infection, resident islet macrophages release the pro-inflammatory cytokine IL-1β, to levels that are sufficient to stimulate inducible nitric oxide synthase (iNOS) expression and production of micromolar levels of the free radical nitric oxide in neighboring β-cells. We have recently shown that nitric oxide inhibits EMCV replication and EMCV-mediated β-cell lysis and that this protection is associated with an inhibition of mitochondrial oxidative metabolism. Here we show that the protective actions of nitric oxide against EMCV infection are selective for β-cells and associated with the metabolic coupling of glycolysis and mitochondrial oxidation that is necessary for insulin secretion. Inhibitors of mitochondrial respiration attenuate EMCV replication in β-cells, and this inhibition is associated with a decrease in ATP levels. In mouse embryonic fibroblasts (MEFs), inhibition of mitochondrial metabolism does not modify EMCV replication or decrease ATP levels. Like most cell types, MEFs have the capacity to uncouple the glycolytic utilization of glucose from mitochondrial respiration, allowing for the maintenance of ATP levels under conditions of impaired mitochondrial respiration. It is only when MEFs are forced to use mitochondrial oxidative metabolism for ATP generation that mitochondrial inhibitors attenuate viral replication. In a β-cell selective manner, these findings indicate that nitric oxide targets the same metabolic pathways necessary for glucose stimulated insulin secretion for protection from viral lysis.

Poly(ADP-ribose) polymerase (PARP) superfamily members covalently link either a single ADP-ribose (ADPR) or a chain of ADPR units to proteins using NAD as the source of ADPR. Although the well-known poly(ADP-ribosylating) (PARylating) PARPs primarily function in the DNA damage response, many noncanonical mono(ADP-ribosylating) (MARylating) PARPs are associated with cellular antiviral responses. We recently demonstrated robust up-regulation of several PARPs following infection with murine hepatitis virus (MHV), a model coronavirus. Here we show that SARS-CoV-2 infection strikingly up-regulates MARylating PARPs and induces the expression of genes encoding enzymes for salvage NAD synthesis from nicotinamide (NAM) and nicotinamide riboside (NR), while down-regulating other NAD biosynthetic pathways. We show that overexpression of PARP10 is sufficient to depress cellular NAD and that the activities of the transcriptionally induced enzymes PARP7, PARP10, PARP12 and PARP14 are limited by cellular NAD and can be enhanced by pharmacological activation of NAD synthesis. We further demonstrate that infection with MHV induces a severe attack on host cell NAD+ and NADP+. Finally, we show that NAMPT activation, NAM, and NR dramatically decrease the replication of an MHV that is sensitive to PARP activity. These data suggest that the antiviral activities of noncanonical PARP isozyme activities are limited by the availability of NAD and that nutritional and pharmacological interventions to enhance NAD levels may boost innate immunity to coronaviruses.

How is the war in Ukraine affecting perceptions of Russia in Africa? Explainer Video NCapeling 10 June 2022

Aanu Adeoye outlines how the invasion of Ukraine is affecting perceptions of Russia across the Africa region.

He says the voting patterns at the United Nations (UN) shows that the majority of African countries are unhappy about Russia’s actions, but there is not a united voice as there is in the European Union (EU) and North America.

Certain countries are heavily influenced by historical ties with Russia going back to the Soviet era and their own struggles for liberation, while others tend to remain non-aligned whenever possible.

Enhancing the role of women in peacebuilding and politics in Ethiopia 29 June 2022 — 1:00PM TO 2:30PM Anonymous (not verified) 16 June 2022 Online

Panellists discuss the priorities for promoting the agency of women in politics and peacebuilding in Ethiopia and approaches for combatting gender-based discrimination and violence.

The war in northern Ethiopia and conflicts elsewhere have disproportionately affected women and girls – including through the infliction of physical and sexual violence, the heightened impacts of displacement and disruptions to education, and the co-option of women’s experiences in narratives by aggressors of conflict.

Hard-won political gains in women’s rights have been undermined and deep-rooted gender inequalities exacerbated. Despite this, women remain central actors in politics, as well as in conflict resolution and mediation efforts. However, more needs to be done to promote the security and inclusion of women in finding sustainable solutions for Ethiopia’s long-term recovery and to institutionalize reforms for gender equity and development.

At this public event, panellists will discuss the priorities for improving women’s participation and equality in public decision-making in Ethiopia and how to strengthen the implementation of legislation on women’s rights. They will also discuss what societal shifts and approaches are needed to combat gender-based discrimination and violence and to promote the agency of women in peacebuilding.

This webinar is part of a series of events and outputs on Ethiopia’s political transition.

This event will also be broadcast live on the Chatham House Africa Programme’s Facebook page.

What will authorizing the return of US troops mean for Somalia? Explainer Video aboudiaf.drupal 17 June 2022

Ahmed Soliman examines what the reintroduction of US military means for Somalia.

He says the strategy remains to try and reduce al-Shabaab’s threat, suppress its ability to carry out operations, and target its senior leadership.

There is more of a recognition now that the focus needs to be on restoring an effective security sector within Somalia and ensuring their forces are ready, but this also requires better coordination between the federal government and federal member states which it is hoped will happen in this new administration.

What challenges does the new president of Somalia face? Explainer Video aboudiaf.drupal 28 June 2022

Ahmed Soliman examines the challenges the new president Hassan Sheikh Mohamud faces in his first 100 days as president.

Key issues for the new administration are a deteriorating situation with regards to drought as close to half the population are facing food insecurity due to a fourth failed rainy season.

Combined with an inflation rate above ten per cent, many Somalis are at risk of famine and starvation. Many areas of the country are affected from the pastoralist regions to those which house IDP camps around the capital city and other towns, all being exacerbated by the war in Ukraine as Somalia was importing much of its wheat imports from Ukraine and Russia.

Climbing out of the Chinese debt trap The World Today mhiggins.drupal 1 August 2022

Beijing must play a pivotal role in soothing African economic distress, says Alex Vines.

Poorer countries across the world – including many in Africa – are facing $35 billion in debt-service payments in 2022. According to the World Bank, around 40 per cent of this total is owed to China.

Across the African continent, the economic impacts of the coronavirus pandemic have increased rates of extreme poverty and inequality. Since early 2022 the situation has worsened even further, due to the knock-on effects of spiking inflation and interest rates following the Russian invasion of Ukraine. Shortages of fuel and foodstuffs have caused prices to leap upwards. Urban unrest is on the rise, and African governments are having to make tough economic choices as their budgets are squeezed ever more tightly.

Across the continent, progress on the UN’s Sustainable Development Goals is being jeopardized, and non-energy-producing lower and lower-middle income African governments are struggling to repay their loans.

During the Covid pandemic, the G20 assisted 31 out of 36 eligible African countries with its Debt Service Suspension Initiative (DSSI). Established in May 2020, the DSSI helped countries concentrate their resources on fighting the pandemic and safeguarding the lives and livelihoods of millions of the most vulnerable people before it expired at the end of 2021. From 2022, it has been replaced by the G20’s Common Framework for Debt Treatments.

As the second-largest economy in the world after the United States, and the dominant lender for many African states, China has an important role to play in such initiatives. Beijing still tries to keep a low profile and renegotiate its terms on a bilateral basis – although it did support Angola’s early call for G20 action on an initiative that would fulfil what the DSSI delivered. The challenge is to encourage more consistency and trust in such initiatives, as Chinese officials consider them to be too western-oriented. 
 

China’s lending to Africa peaked in 2016

Contemporary views of Chinese lending in Africa remain coloured by the rapid expansion of Chinese finance from the early 2000s to resource-rich African states, and oil producers in particular. The reality is that much of China’s lending has evolved, and is neither intrinsically predatory nor problematic for African partners – and China increasingly prefers to do business with states it considers to be better run.

In fact, as commodity prices and growth rates declined from 2015, Chinese lending to Africa fell significantly, from a peak of $29.5 billion in 2016 to $7.6 billion in 2019. The socio-economic impact of the pandemic has made this situation worse.

That China has attracted criticism is often due to a lack of transparency in its investments, especially those in Kenya and Zambia. This reputation has not been helped by opaque lending arrangements imposed by Chinese state-owned banks, requiring borrowers to prioritize them for repayment. This could lead to cutbacks in key areas of social spending, with direct impacts on African communities.

Over the past two decades, Chinese finance has contributed to an infrastructure boom in many African countries. Angola, for example, was able to undertake a rapid post-conflict reconstruction of its infrastructure, with new roads and bridges being built across the country. New models of financing are being developed: in Kenya, the new Nairobi expressway was constructed under a $600 million Build-Operate-Transfer model that provides for ownership to revert to the national government after a 30-year concession period.

Chinese companies have helped African countries build and upgrade over 10,000km of railway, around 100,000km of highway, 1,000 bridges and 100 ports, as well as power plants, hospitals and schools.

China’s involvement in African debt has varied considerably between countries and over time. Although in recent years this involvement has been framed in the context of the Belt and Road Initiative, it has for the most part been uncoordinated and unplanned, with credit being offered by competing lenders with links to different elements of the Chinese state.

In recent years, as reports have emerged around the poor quality of some of China’s past lending, the authorities in Beijing have sought greater control over new development lending and have imposed new sustainability requirements. At the same time, African countries have sought to diversify sources of supply for infrastructure contracts beyond China. Loans are generally now on a smaller, more manageable scale.

With the introduction of its Global Development Initiative in September 2021, there are indications that China is moving to a ‘new development paradigm’, with the emphasis on providing flows of foreign direct investment rather than loans and a focus on supporting small and medium-sized enterprises, human capital investments and green development.
 

African debt distress

A paper drawing on expertise from Chatham House’s Africa, Asia and Global Economy and Finance experts will be published before the G20 summit in Bali in November 2022. It examines seven African countries that the World Bank deemed in 2020 to be in most debt distress or at risk of debt distress because of their Chinese stock – Angola, Cameroon, Republic of Congo, Djibouti, Ethiopia, Kenya and Zambia. Two countries – Côte d’Ivoire and South Africa – have received new loans from China and are not in any distress.

The paper observes that a lack of transparency over the nature of the terms agreed by these African governments has led to intense domestic criticism and international accusations that China is seeking control over strategic assets.

In fact, in Angola and Zambia, China may have accidently fallen into its own debt trap through profligate and uncoordinated lending.

Zambia became the first pandemic-era default in 2020 and is seeking relief on $17 billion of external debt. After holding general elections in August 2022, Angola and Kenya will also seek additional debt relief, but both may also seek more funds from the private commercial market because of the slow progress of the G20’s Common Framework – something flagged as a concern by China.

All seven of the countries that are most indebted to China are actively seeking to reduce this financial reliance on Beijing in the future.

China has a pivotal role to play in finding effective solutions to these and other African countries’ debt distress. Improved coordination and cooperation between creditors in China and in other parts the world could enhance the positive impact of multilateral initiatives, such as the Common Framework, which has aimed to bring China and India to the negotiating table along with the IMF, the Paris Club group of creditor nations and private creditors.

So far, Chad, Ethiopia and Zambia are the only African countries to have signed up to the framework since its launch in 2020. Although China is suspicious of the IMF, if African states collectively encouraged Beijing to engage with the Common Framework, it could be improved so as to provide debt relief to those African countries finding it difficult to repay their loans.

Review: the rise of Africa’s superwomen The World Today mhiggins.drupal 1 August 2022

From foster care in England to colonialism’s legacy in Zimbabwe, this set of essays on race, feminism and identity is searingly honest, says Masiyaleti Mbewe.

Black and Female
Tsitsi Dangarembga, Faber, £9.99

The 1988 novel Nervous Conditions by the Zimbabwean author Tsitsi Dangarembga is considered one of Africa’s finest literary exports. It won the Commonwealth Writers’ Prize and alongside The Book of Not (2006) and This Mournable Body (2018), shortlisted for the 2020 Booker Prize, forms a trilogy of semi-autobiographical novels that grapple with the gendered colonial oppression of young black girls and women from Southern Rhodesia through to Zimbabwe. 

In Black and Female, Dangarembga continues the interrogation of these intersections in an unflinchingly honest and personal, if occasionally dense, collection of essays. Along the way, she examines the sheer magnitude of colonialism’s effects on African people, and how they ripple through her early childhood in England and her formative years as a writer, filmmaker and feminist activist in post-independence Zimbabwe.

‘Writing While Black and Female’

In 1961 Dangarembga’s parents relocated from Southern Rhodesia to the UK. While they worked and studied in London, they put their two-year-old daughter, her older brother and, later, her younger sister into private foster care in Dover, Kent (as many Africans did – a fact that was new to me). The first essay, ‘Writing While Black and Female’, takes a painful look at the four years she spent with her foster parents, Mummy-Gran and Daddy Henry. 

Blackness, she learned in those years, was a consequence of her non-whiteness. So Dangarembga writes of the momentary elation she felt when a stranger addressed her as a ‘lovely little piccaninny’, giving her ‘a category I could wield against the void of no longer being’. To cope with this sort of racialization and her abandonment, the young Dangarembga turned to disassociation and self-harm. 

As she writes: ‘Blackness is a condition imposed on me, rather than being an experienced identity.’ Instead of ‘black’ people, therefore, Dangarembga prefers the term ‘highly melanated people’. It is a resonant phrase, highlighting the inherently ridiculous nature of racism.

Dangarembga’s ‘Africanness’ shifts into focus upon her return to Rhodesia in 1965. At first, other children refused to play with her and her siblings, calling them ‘varungu’ (white people). As she describes it: ‘The dance of my identities … became frenetic’. 

In ‘Black, Female and the Superwoman Black Feminist’, the second essay, Dangarembga is adamant about the urgent necessity of a black feminist practice that is centred on action to provide real, material change. Along the way, she makes a distinction – a slightly uneasy one to my mind – between the patriarchy that western colonization imposed, based on private ownership, and the patriarchy of pre-colonial African society with its foundations in kinship that devolved power to an extent.

‘Hence women could and did become rulers and warriors, and royal spirit mediums called mhondoro,’ Dangarembga writes approvingly. She is making a nuanced point; but the idea of a more accommodating sort of patriarchy jars a little nonetheless.

While independence may have arrived for Zimbabwe more than 40 years ago, Dangarembga argues strongly that the subjugation of women and feminists at the hands of the ruling Zanu-PF government continues as an extension of colonial rule. Indeed, beyond Zimbabwe, black feminists remain ‘a small, often embattled group’ across Africa, believes Dangarembga. 

As a young black feminist who is part of this ‘small, embattled group’, I should say we have been able to foster large communities digitally and otherwise to work around the hostility we are often faced with. Despite internet shutdowns and restrictions, we resist – an act Dangarembga encourages.  

Resistance, she says, starts with establishing community despite these difficulties. At the nucleus of Dangarembga’s argument is the ‘superwoman’ of the essay’s title, the African woman who doesn’t require external factors to be inspired to action but who continuously draws on what Dangarembga calls ‘internal agency’ that derives from ‘an unrelenting fight for survival and dignity’.

Pointedly, she criticizes global feminism’s greater focus on optics than activism in the practical sense. One only has to observe the performative allyship and ‘Instagram activism’ rampant on the internet today to see her point.
 

The complexities of decolonization

In the final essay, ‘Decolonization as Revolutionary Imagining’, Dangarembga turns her gaze upon the ‘highly stratified’ European societies that outsourced their violent inequality to their empires and ‘the work of decolonization’. However, decolonial discourse is complex, and it is here that the writing occasionally gets bogged down. Fewer recommendations with more elaboration perhaps would have helped.

She herself acknowledges the difficulties of decolonization. Centuries of the Enlightenment and its logic of ‘racism, slavery, genocide and colonization’ are hard to uproot ‘whatever one’s melanin concentration’, she writes.

Nevertheless, Dangarembga concludes with the radical determination to dismantle that is evident throughout this searing yet hopeful collection: ‘The trajectory of current and future generations depends on that uprooting.’

Youth innovation can help shape the future of African cities Expert comment LToremark 16 August 2022

To meet the challenges of rapid urbanization, African governments must harness the potential of young innovators to help shape the future of African cities.

It is projected that 1.3 billion people will be living in Africa’s cities by 2050, an increase of almost 1 billion from today, and largely driven by young people migrating to urban centres in search of work. As the continent’s urban population grows, cities will need to adapt by nurturing new economic ecosystems to create jobs, while managing the environmental, social and political pressures that urbanization brings.

The evolution of Africa’s cities is critical for meeting the demands of its youth population and must be co-created with them. Africa’s young innovators are already proving to be an asset in shaping the future of African cities and, if they are allowed to flourish, they could be at the forefront of finding much-needed solutions to the continent’s vast urban challenges.

Growing tech hubs

African countries are increasingly benefitting from growth in technology ecosystems, which are often clustered within cities. There are currently more than 600 tech hubs helping to incubate innovative solutions across cities in Africa. Between 2015 and 2020, the number of start-ups receiving funding grew six times faster than the global average. In 2021 alone, start-ups raised over $4billion in funding – twice as much as in 2020.

But significant challenges remain. While the number of new start-ups is an encouraging indication of the entrepreneurialism and creativity of Africa’s youth, job creation on the level required will demand that they grow and scale up to generate more and higher quality jobs. Research on scaling up in Africa is sparse but research by Endeavor suggests that in Nairobi – one of Africa’s top tech ecosystems – only 5 per cent of companies are able to sustain growth of 20 per cent or more each year, yet they created 72 per cent of new jobs in the previous three years. For Africa to fully harness the potential of digital innovation, making cities the best place for young people to launch ideas and grow them into thriving businesses must become a priority policy for African governments. 

Barriers to scale

On the most basic level, business growth needs access to the services that make cities more liveable and help both urban residents and firms become more productive, such as healthcare, transport, water and sanitation. African cities already struggle to provide their residents – in particular the poorest and most vulnerable – with equitable, reliable, affordable and quality access to these services, in a sustainable manner. And these challenges will only get more acute as urban populations rise rapidly, often without any kind of integrated planning.

For example, an estimated 70-80 per cent of municipal solid waste in Africa is recyclable, yet only about 4 per cent is currently recycled, with more than 90 per cent of waste ending up in uncontrolled dumpsites and landfills. As Africa’s urban population grows, these conditions are likely to worsen – unless there is urgent action. New technology has the potential to help by creating a positive feedback loop between innovation, service delivery and growth. For example, to bridge the waste management gap, innovators are exploring various tech-enabled circular economy models. These solutions are often ground-breaking and have the potential to leapfrog traditional waste management infrastructure. Crucially, they are also formalizing a largely informal sector and creating new jobs.

Across the continent, start-ups like Kaltani, Mr Green Africa and Freetown Waste Transformers build processing facilities to turn waste into energy or reusable products, such as construction materials. Others, like Scrapays, Regenize and Soso Care, are helping households and businesses sell off their recycled materials for cash and virtual currencies or exchange them for critical services, such as micro health insurance premiums. Such start-ups help empower informal waste pickers or agents with tech-enabled tools and target low-income urban communities that would not normally prioritize recycling.

Help or hindrance from the top?

But Africa’s young people cannot do this alone – government decision-makers must become catalysts for entrepreneurial leadership. This requires nurturing a mindset that sees young innovators as Africa’s biggest resource, not a threat. While the importance of young people to Africa’s development is acknowledged in various high-level regional treaties, patterns of inhibition and outright hostility from political ‘elites’ suggest that the disruptive nature of technology start-ups and their access to significant capital through venture capital funding models – unlike existing rent-seeking business models with government control – threatens the political establishment.

The growing use of tech solutions also leads to increased transparency and efficiency of service delivery, which in turn leads to increased demand for government accountability and pressure to adopt more liberal policies. Until there is a shift towards catalysing entrepreneurial leadership, there is a stronger incentive for political elites to leverage their powers to co-opt successful technology businesses, or otherwise try to control them for political gain, than let them flourish. This shift in mindset will be critical to unlocking the full potential of Africa’s young innovators.

The Climate Briefing: The nexus of water security and climate policy Audio NCapeling 22 August 2022

Examining the crossover between water security and climate change with the next two COPs taking place in regions with a history of being water stressed.

What should policymakers and negotiators from the Middle East and Africa working on water security focus on at COP27?

What does it mean to achieve water security? What are the main barriers or challenges? How is water security relevant to climate change?

This podcast was produced in collaboration with the UK Aid-funded Knowledge, Evidence and Learning for Development (K4D) programme which facilitates the use of evidence and learning in international development policy and programming.

Africa Aware: Drought in the Horn of Africa Audio aboudiaf.drupal 31 October 2022

This episode discusses how the Horn of Africa’s worst drought in 40 years is affecting more than 20 million people across several countries.

Abdirahman Abdishakur, Special Presidential Envoy for Drought Response for the Federal Republic of Somalia, outlines the Somali government’s planning to prevent famine.

Parvin Ngala, Regional Director at Oxfam International, highlights international efforts to respond to the drought, the importance of empowering civil society in these circumstances, and what long-term mitigation measures are necessary to avoid a return to this situation.

Purpose: The ⁶⁸Ga-PSMA PET/CT is a commonly used imaging modality in prostate cancers. However, few studies have compared the diagnostic efficiency between ⁶⁸Ga-PSMA and ¹⁸F-FDG PET/CT and evaluated whether a heterogeneous metabolic phenotype (especially PSMA-FDG+ lesions) exists in patients with castration-resistant prostate cancer (CRPC). We determined the added value of ¹⁸F-FDG PET/CT compared to ⁶⁸Ga-PSMA PET/CT in CRPC patients and identified CRPC patients who may benefit from additional ¹⁸F-FDG PET/CT. Methods: Data of 56 patients with CRPC who underwent both ⁶⁸Ga-PSMA and ¹⁸F-FDG PET/CT from May 2018 to February 2021 were retrospectively analysed. Patients were classified into two groups with or without PSMA-FDG+ lesions. The differences in patient characteristics between the two groups and predictors of patients who having at least one PSMA-FDG+ lesion were analysed. Results: Although both the detection rate (75.0% vs. 51.8%, P = 0.004) and positive lesion number (135 vs. 95) of ⁶⁸Ga-PSMA PET/CT were higher than ¹⁸F-FDG PET/CT, there were still 13/56 (23.2%) patients with at least one PSMA-FDG+ lesion. The prostate-specific antigen (PSA) and Gleason score were both higher in the patients with PSMA-FDG+ lesions than in those without PSMA-FDG+ lesions (P = 0.04 and P<0.001, respectively). Multivariate regression analysis showed that the Gleason score (≥8) and PSA (≥7.9 ng/mL) were associated with the detection rate of patients who had PSMA-FDG+ lesions (P = 0.01 and P = 0.04, respectively). The incidences of having PSMA-FDG+ lesions in low-probability (Gleason score<8 and PSA<7.9 ng/mL), medium-probability (Gleason score≥8 and PSA<7.9 ng/mL or Gleason score<8 and PSA≥7.9 ng/mL), and high-probability (Gleason score≥8 and PSA≥7.9 ng/mL) groups were 0%, 21.7%, and 61.5%, respectively (P<0.001). Conclusion: Gleason score and PSA are significant predictors for PSMA-FDG+ lesions, and CRPC patients with high Gleason score and PSA may benefit from additional ¹⁸F-FDG PET/CT.

Visual Abstract

Visual Abstract