Nica M. Borradaile
Dec 1, 2006; 47:2726-2737
Research Articles

The Future of Investment Dispute Settlement Regimes 30 June 2020 — 2:00PM TO 3:30PM Anonymous (not verified) 9 February 2021 Online

This event is part of the Inclusive Governance Initiative, which is examining how to build more inclusive models and mechanisms of global governance fit for purpose in today’s world.

Is an ‘atomized’ approach to cross-border investment dispute resolution inevitable? Has the multiplicity of mechanisms helped or hindered inclusivity in and transparency in governance? Is there a need for, and scope to, increase the international coordination of dispute resolution mechanisms? If so, what form should it take? What could be the implications for international economic law?

Hepatocyte nuclear factor-1β (HNF-1β) is a tissue-specific transcription factor that is required for normal kidney development and renal epithelial differentiation. Mutations of HNF-1β produce congenital kidney abnormalities and inherited renal tubulopathies. Here, we show that ablation of HNF-1β in mIMCD3 renal epithelial cells results in activation of β-catenin and increased expression of lymphoid enhancer–binding factor 1 (LEF1), a downstream effector in the canonical Wnt signaling pathway. Increased expression and nuclear localization of LEF1 are also observed in cystic kidneys from Hnf1b mutant mice. Expression of dominant-negative mutant HNF-1β in mIMCD3 cells produces hyperresponsiveness to exogenous Wnt ligands, which is inhibited by siRNA-mediated knockdown of Lef1. WT HNF-1β binds to two evolutionarily conserved sites located 94 and 30 kb from the mouse Lef1 promoter. Ablation of HNF-1β decreases H3K27 trimethylation repressive marks and increases β-catenin occupancy at a site 4 kb upstream to Lef1. Mechanistically, WT HNF-1β recruits the polycomb-repressive complex 2 that catalyzes H3K27 trimethylation. Deletion of the β-catenin–binding domain of LEF1 in HNF-1β–deficient cells abolishes the increase in Lef1 transcription and decreases the expression of downstream Wnt target genes. The canonical Wnt target gene, Axin2, is also a direct transcriptional target of HNF-1β through binding to negative regulatory elements in the gene promoter. These findings demonstrate that HNF-1β regulates canonical Wnt target genes through long-range effects on histone methylation at Wnt enhancers and reveal a new mode of active transcriptional repression by HNF-1β.

Expert

In animals, the response to chronic hypoxia is mediated by prolyl hydroxylases (PHDs) that regulate the levels of hypoxia-inducible transcription factor α (HIFα). PHD homologues exist in other types of eukaryotes and prokaryotes where they act on non HIF substrates. To gain insight into the factors underlying different PHD substrates and properties, we carried out biochemical and biophysical studies on PHD homologues from the cellular slime mold, Dictyostelium discoideum, and the protozoan parasite, Toxoplasma gondii, both lacking HIF. The respective prolyl-hydroxylases (DdPhyA and TgPhyA) catalyze prolyl-hydroxylation of S-phase kinase-associated protein 1 (Skp1), a reaction enabling adaptation to different dioxygen availability. Assays with full-length Skp1 substrates reveal substantial differences in the kinetic properties of DdPhyA and TgPhyA, both with respect to each other and compared with human PHD2; consistent with cellular studies, TgPhyA is more active at low dioxygen concentrations than DdPhyA. TgSkp1 is a DdPhyA substrate and DdSkp1 is a TgPhyA substrate. No cross-reactivity was detected between DdPhyA/TgPhyA substrates and human PHD2. The human Skp1 E147P variant is a DdPhyA and TgPhyA substrate, suggesting some retention of ancestral interactions. Crystallographic analysis of DdPhyA enables comparisons with homologues from humans, Trichoplax adhaerens, and prokaryotes, informing on differences in mobile elements involved in substrate binding and catalysis. In DdPhyA, two mobile loops that enclose substrates in the PHDs are conserved, but the C-terminal helix of the PHDs is strikingly absent. The combined results support the proposal that PHD homologues have evolved kinetic and structural features suited to their specific sensing roles.

Flexible Distribution Systems: New Services, Actors and Technologies 4 September 2018 — 9:00AM TO 10:30AM Anonymous (not verified) 31 July 2018 Chatham House, London

The pace of the energy transition is accelerating. Solar and wind are dramatically falling in cost and displacing fossil fuel generators. Simultaneously, the rapid uptake of electric vehicles and battery storage systems are beginning to send shock-waves through the electricity sector.

As the proportion of distributed energy resources (DERs) connected to the distribution network grows, a significant opportunity is beginning to present itself. What if the concerns of renewable integration and associated costs could be solved by the smart integration of these DERs?

By properly valuing the services DERs can provide, actively managing the distribution system and creating new market places, might a truly renewable electricity system capable of supporting the electrification of heat and transport be possible?

During this roundtable, Andrew Scobie, CEO of Faraday Grid, will provide an overview of the challenges and opportunities faced within the distribution network and explain why the current system is no longer fit for purpose.

This is the inaugural event in the Energy Transitions Roundtable (ETR) series.

Environmental Change and Emerging Diseases 28 October 2020 — 3:00PM TO 4:00PM Anonymous (not verified) 13 October 2020 Online

Understanding how environmental changes are directly and indirectly affecting the emergence and spread of disease has assumed global importance.

There is growing awareness that deforestation and land-use conversion, urbanization, human migration, international commerce, and climate change are having significant impacts on human health, but their impact on increasing infectious disease risks has only become more evident with the coronavirus pandemic.

With climate change, and environmental change more generally, disrupting ecologies, and people interacting with wildlife in new ways, it creates the conditions for new diseases to emerge: a better understanding of the health dimensions of environmental change will be critical to managing pandemic risks in future. 

Our event will examine the relationship between environmental change and disease, how these linkages have manifested in historical outbreaks and in the coronavirus pandemic, and the role of environmental policies in minimizing the risk of future emerging diseases.  What can be done to ensure equitable action? What can we learn from our responses to previous pandemics? And will the growing recognition of the diverse risks arising from climate change motivate more climate action?

This event will launch the Energy, Environment and Resources (EER) Programme’s Environment and Society Discussion Series. This series aims to provide a platform to promote interdisciplinary knowledge sharing and policy dialogue to mitigate and adapt to the impacts that climate change, biodiversity loss and natural resource depletion are having on people and communities globally, and on geopolitics, security and international development.

Sign up to find out about more events in this series here. 

Webinar: Hong Kong: Dissent in the Age of Coronavirus 17 April 2020 — 12:00PM TO 1:00PM Anonymous (not verified) 8 April 2020

Street protests demanding greater autonomy and democratization in Hong Kong upended the city for seven months last year. However, with the outbreak of the coronavirus in China in late January, the protests quickly died out. What does this mean for the city’s protest movement?

The speaker will argue that, despite the lack of high-profile street rallies, protest in the city is continuing. It is building on and evolving from last year’s protest movement albeit in different forms. At the same time, the Hong Kong authorities, emboldened by a hard line from Beijing, have begun cracking down on activists and protesters in the city as they seek to put a lid on dissent ahead of important Legislative Council elections scheduled for this September.

In this webinar, the speaker will look at the current state of dissent in Hong Kong and prospects for Hong Kong’s future.

This event will be held on the record.

Torin Greenwood, Jonathan Kariv and Noah Williams
Math. Comp. 93 (), 2959-2983.
Abstract, references and article information

Constantin Carle and Marlis Hochbruck
Math. Comp. 93 (), 2611-2641.
Abstract, references and article information

Song Dai and Qiongling Li
Trans. Amer. Math. Soc. 377 (), 5445-5481.
Abstract, references and article information

Simone Cecchini and Rudolf Zeidler
Trans. Amer. Math. Soc. 377 (), 5271-5288.
Abstract, references and article information

AO-Koun posted a photo:

Christian Weiss
Theor. Probability and Math. Statist. 111 (), 199-209.
Abstract, references and article information

Marko Voutilainen, Lauri Viitasaari and Pauliina Ilmonen
Theor. Probability and Math. Statist. 111 (), 181-197.
Abstract, references and article information

Bero Roos
Theor. Probability and Math. Statist. 111 (), 137-151.
Abstract, references and article information

Olha Prykhodko and Kostiantyn Ralchenko
Theor. Probability and Math. Statist. 111 (), 123-135.
Abstract, references and article information

Chris A.J. Klaassen
Theor. Probability and Math. Statist. 111 (), 9-19.
Abstract, references and article information

Gabriele Benedetti, Johanna Bimmermann and Kai Zehmisch
Proc. Amer. Math. Soc. 152 (), 5367-5372.
Abstract, references and article information

N. Kuznetsov
St. Petersburg Math. J. 35 (), 467-472.
Abstract, references and article information

The two branches of the Kennedy pathways (CDP-choline and CDP-ethanolamine) are the predominant pathways responsible for the synthesis of the most abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively, in mammalian membranes. Recently, hereditary diseases associated with single gene mutations in the Kennedy pathways have been identified. Interestingly, genetic diseases within the same pathway vary greatly, ranging from muscular dystrophy to spastic paraplegia to a childhood blinding disorder to bone deformations. Indeed, different point mutations in the same gene (PCYT1; CCTα) result in at least three distinct diseases. In this review, we will summarize and review the genetic diseases associated with mutations in genes of the Kennedy pathway for phospholipid synthesis. These single-gene disorders provide insight, indeed direct genotype-phenotype relationships, into the biological functions of specific enzymes of the Kennedy pathway. We discuss potential mechanisms of how mutations within the same pathway can cause disparate disease.

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Reliable, specific polyclonal and monoclonal antibodies are important tools in research and medicine. However, the discovery of antibodies against their targets in their native forms is difficult. Here, we present a novel method for discovery of antibodies against membrane proteins in their native configuration in mammalian cells. The method involves the co-expression of an antibody library in a population of mammalian cells that express the target polypeptide within a natural membrane environment on the cell surface. Cells that secrete a single-chain fragment variable (scFv) that binds to the target membrane protein thereby become self-labeled, enabling enrichment and isolation by magnetic sorting and FRET-based flow sorting. Library sizes of up to 109 variants can be screened, thus allowing campaigns of naïve scFv libraries to be selected against membrane protein antigens in a Chinese hamster ovary cell system. We validate this method by screening a synthetic naïve human scFv library against Chinese hamster ovary cells expressing the oncogenic target epithelial cell adhesion molecule and identify a panel of three novel binders to this membrane protein, one with a dissociation constant (KD) as low as 0.8 nm. We further demonstrate that the identified antibodies have utility for killing epithelial cell adhesion molecule–positive cells when used as a targeting domain on chimeric antigen receptor T cells. Thus, we provide a new tool for identifying novel antibodies that act against membrane proteins, which could catalyze the discovery of new candidates for antibody-based therapies.

Thoracic great vessels such as the aorta and subclavian arteries are formed through dynamic remodeling of embryonic pharyngeal arch arteries (PAAs). Previous work has shown that loss of a basic helix-loop-helix transcription factor Hey1 in mice causes abnormal fourth PAA development and lethal great vessel anomalies resembling congenital malformations in humans. However, how Hey1 mediates vascular formation remains unclear. In this study, we revealed that Hey1 in vascular endothelial cells, but not in smooth muscle cells, played essential roles for PAA development and great vessel morphogenesis in mouse embryos. Tek-Cre–mediated Hey1 deletion in endothelial cells affected endothelial tube formation and smooth muscle differentiation in embryonic fourth PAAs and resulted in interruption of the aortic arch and other great vessel malformations. Cell specificity and signal responsiveness of Hey1 expression were controlled through multiple cis-regulatory regions. We found two distal genomic regions that had enhancer activity in endothelial cells and in the pharyngeal epithelium and somites, respectively. The novel endothelial enhancer was conserved across species and was specific to large-caliber arteries. Its transcriptional activity was regulated by Notch signaling in vitro and in vivo, but not by ALK1 signaling and other transcription factors implicated in endothelial cell specificity. The distal endothelial enhancer was not essential for basal Hey1 expression in mouse embryos but may likely serve for Notch-dependent transcriptional control in endothelial cells together with the proximal regulatory region. These findings help in understanding the significance and regulation of endothelial Hey1 as a mediator of multiple signaling pathways in embryonic vascular formation.

Stromal interaction molecule 1 (STIM1) plays a pivotal role in store-operated Ca2+ entry (SOCE), an essential mechanism in cellular calcium signaling and in maintaining cellular calcium balance. Because O-GlcNAcylation plays pivotal roles in various cellular function, we examined the effect of fluctuation in STIM1 O-GlcNAcylation on SOCE activity. We found that both increase and decrease in STIM1 O-GlcNAcylation impaired SOCE activity. To determine the molecular basis, we established STIM1-knockout HEK293 (STIM1-KO-HEK) cells using the CRISPR/Cas9 system and transfected STIM1 WT (STIM1-KO-WT-HEK), S621A (STIM1-KO-S621A-HEK), or T626A (STIM1-KO-T626A-HEK) cells. Using these cells, we examined the possible O-GlcNAcylation sites of STIM1 to determine whether the sites were O-GlcNAcylated. Co-immunoprecipitation analysis revealed that Ser621 and Thr626 were O-GlcNAcylated and that Thr626 was O-GlcNAcylated in the steady state but Ser621 was not. The SOCE activity in STIM1-KO-S621A-HEK and STIM1-KO-T626A-HEK cells was lower than that in STIM1-KO-WT-HEK cells because of reduced phosphorylation at Ser621. Treatment with the O-GlcNAcase inhibitor Thiamet G or O-GlcNAc transferase (OGT) transfection, which increases O-GlcNAcylation, reduced SOCE activity, whereas treatment with the OGT inhibitor ST045849 or siOGT transfection, which decreases O-GlcNAcylation, also reduced SOCE activity. Decrease in SOCE activity due to increase and decrease in O-GlcNAcylation was attributable to reduced phosphorylation at Ser621. These data suggest that both decrease in O-GlcNAcylation at Thr626 and increase in O-GlcNAcylation at Ser621 in STIM1 lead to impairment of SOCE activity through decrease in Ser621 phosphorylation. Targeting STIM1 O-GlcNAcylation could provide a promising treatment option for the related diseases, such as neurodegenerative diseases.

Myelination plays an important role in cognitive development and in demyelinating diseases like multiple sclerosis (MS), where failure of remyelination promotes permanent neuro-axonal damage. Modification of cell surface receptors with branched N-glycans coordinates cell growth and differentiation by controlling glycoprotein clustering, signaling, and endocytosis. GlcNAc is a rate-limiting metabolite for N-glycan branching. Here we report that GlcNAc and N-glycan branching trigger oligodendrogenesis from precursor cells by inhibiting platelet-derived growth factor receptor-α cell endocytosis. Supplying oral GlcNAc to lactating mice drives primary myelination in newborn pups via secretion in breast milk, whereas genetically blocking N-glycan branching markedly inhibits primary myelination. In adult mice with toxin (cuprizone)-induced demyelination, oral GlcNAc prevents neuro-axonal damage by driving myelin repair. In MS patients, endogenous serum GlcNAc levels inversely correlated with imaging measures of demyelination and microstructural damage. Our data identify N-glycan branching and GlcNAc as critical regulators of primary myelination and myelin repair and suggest that oral GlcNAc may be neuroprotective in demyelinating diseases like MS.

Infiltration of peripheral immune cells after blood-brain barrier dysfunction causes severe inflammation after a stroke. Although the endothelial glycocalyx, a network of membrane-bound glycoproteins and proteoglycans that covers the lumen of endothelial cells, functions as a barrier to circulating cells, the relationship between stroke severity and glycocalyx dysfunction remains unclear. In this study, glycosaminoglycans, a component of the endothelial glycocalyx, were studied in the context of ischemic stroke using a photochemically induced thrombosis mouse model. Decreased levels of heparan sulfate and chondroitin sulfate and increased activity of hyaluronidase 1 and heparanase (HPSE) were observed in ischemic brain tissues. HPSE expression in cerebral vessels increased after stroke onset and infarct volume greatly decreased after co-administration of N-acetylcysteine + glycosaminoglycan oligosaccharides as compared with N-acetylcysteine administration alone. These results suggest that the endothelial glycocalyx was injured after the onset of stroke. Interestingly, scission activity of proHPSE produced by immortalized endothelial cells and HEK293 cells transfected with hHPSE1 cDNA were activated by acrolein (ACR) exposure. We identified the ACR-modified amino acid residues of proHPSE using nano LC–MS/MS, suggesting that ACR modification of Lys139 (6-kDa linker), Lys107, and Lys161, located in the immediate vicinity of the 6-kDa linker, at least in part is attributed to the activation of proHPSE. Because proHPSE, but not HPSE, localizes outside cells by binding with heparan sulfate proteoglycans, ACR-modified proHPSE represents a promising target to protect the endothelial glycocalyx.

RNase J enzymes are metallohydrolases that are involved in RNA maturation and RNA recycling, govern gene expression in bacteria, and catalyze both exonuclease and endonuclease activity. The catalytic activity of RNase J is regulated by multiple mechanisms which include oligomerization, conformational changes to aid substrate recognition, and the metal cofactor at the active site. However, little is known of how RNase J paralogs differ in expression and activity. Here we describe structural and biochemical features of two Staphylococcus epidermidis RNase J paralogs, RNase J1 and RNase J2. RNase J1 is a homodimer with exonuclease activity aided by two metal cofactors at the active site. RNase J2, on the other hand, has endonuclease activity and one metal ion at the active site and is predominantly a monomer. We note that the expression levels of these enzymes vary across Staphylococcal strains. Together, these observations suggest that multiple interacting RNase J paralogs could provide a strategy for functional improvisation utilizing differences in intracellular concentration, quaternary structure, and distinct active site architecture despite overall structural similarity.

Cation diffusion facilitator (CDF) proteins are a conserved family of divalent transition metal cation transporters. CDF proteins are usually composed of two domains: the transmembrane domain, in which the metal cations are transported through, and a regulatory cytoplasmic C-terminal domain (CTD). Each CDF protein transports either one specific metal or multiple metals from the cytoplasm, and it is not known whether the CTD takes an active regulatory role in metal recognition and discrimination during cation transport. Here, the model CDF protein MamM, an iron transporter from magnetotactic bacteria, was used to probe the role of the CTD in metal recognition and selectivity. Using a combination of biophysical and structural approaches, the binding of different metals to MamM CTD was characterized. Results reveal that different metals bind distinctively to MamM CTD in terms of their binding sites, thermodynamics, and binding-dependent conformations, both in crystal form and in solution, which suggests a varying level of functional discrimination between CDF domains. Furthermore, these results provide the first direct evidence that CDF CTDs play a role in metal selectivity. We demonstrate that MamM's CTD can discriminate against Mn2+, supporting its postulated role in preventing magnetite formation poisoning in magnetotactic bacteria via Mn2+ incorporation.

Connexin (Cx) protein forms hemichannels and gap junctional channels, which play diverse and profound roles in human physiology and diseases. Gap junctions are arrays of intercellular channels formed by the docking of two hemichannels from adjacent cells. Each hexameric hemichannel contains the same or different Cx isoform. Although homomeric Cxs forms have been largely described functionally and structurally, the stoichiometry and arrangement of heteromeric Cx channels remain unknown. The latter, however, are widely expressed in human tissues and variation might have important implications on channel function. Investigating properties of heteromeric Cx channels is challenging considering the high number of potential subunit arrangements and stoichiometries, even when only combining two Cx isoforms. To tackle this problem, we engineered an HA tag onto Cx26 or Cx30 subunits and imaged hemichannels that were liganded by Fab-epitope antibody fragments via atomic force microscopy. For Cx26-HA/Cx30 or Cx30-HA/Cx26 heteromeric channels, the Fab-HA binding distribution was binomial with a maximum of three Fab-HA bound. Furthermore, imaged Cx26/Cx30-HA triple liganded by Fab-HA showed multiple arrangements that can be derived from the law of total probabilities. Atomic force microscopy imaging of ringlike structures of Cx26/Cx30-HA hemichannels confirmed these findings and also detected a polydisperse distribution of stoichiometries. Our results indicate a dominant subunit stoichiometry of 3Cx26:3Cx30 with the most abundant subunit arrangement of Cx26-Cx26-Cx30-Cx26-Cx30-Cx30. To our knowledge, this is the first time that the molecular architecture of heteromeric Cx channels has been revealed, thus providing the basis to explore the functional effect of these channels in biology.

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.

Intrinsically disordered protein domains often have multiple binding partners. It is plausible that the strength of pairing with specific partners evolves from an initial low affinity to a higher affinity. However, little is known about the molecular changes in the binding mechanism that would facilitate such a transition. We previously showed that the interaction between two intrinsically disordered domains, NCBD and CID, likely emerged in an ancestral deuterostome organism as a low-affinity interaction that subsequently evolved into a higher-affinity interaction before the radiation of modern vertebrate groups. Here we map native contacts in the transition states of the low-affinity ancestral and high-affinity human NCBD/CID interactions. We show that the coupled binding and folding mechanism is overall similar but with a higher degree of native hydrophobic contact formation in the transition state of the ancestral complex and more heterogeneous transient interactions, including electrostatic pairings, and an increased disorder for the human complex. Adaptation to new binding partners may be facilitated by this ability to exploit multiple alternative transient interactions while retaining the overall binding and folding pathway.

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.

4 September 2020

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.

Review: Decolonization and its discontents The World Today mhiggins.drupal 1 August 2022

Jenna Marshall on a lively if flawed argument to find a way forward in a debate that has descended ‘into acrimony’.

Against Decolonization: Taking African Agency Seriously
Olufemi Taiwo, Hurst, £14.99

Decolonization was once heralded as a moment of potential and possibility for the formerly imperial world to chart a new way forward no longer tied to the apparatus of empire.

It marked a period of transition to nation states – and an expansion of a rights-based international community that would dispense with the morally bankrupt regime of racism, dispossession and subjugation that characterized colonialism.  
 

The descent of the decolonization debate

Half a century later, the debate surrounding decolonization has descended into acrimony. Some factions cast the issue of decolonization as a sustained attack on British and western culture writ large; other disparate voices coalesce around related social justice issues such as inequality, climate change and education. 

Decolonization has become ubiquitous in the public domain – and its ubiquity is the problem. In Against Decolonization, Olufemi Taiwo renounces a concept he conceives as having been emptied of serious study and analytical purchase; one incapable of addressing the complexities of modern global politics and more importantly, Africa’s place in it. 

Although the book attacks the inexhaustible ways in which the ‘trope of decolonization’ has been deployed, Taiwo is less bothered by the purported failures of scholars he deems ‘decolonizers’ and focuses his attention instead on the political landscape of African countries, past and present. 

Central to the book’s argument are two distinct scholarly strands on decolonization. The first, legal focus, centres on the political and economic forces of state-building. The second essays an ‘ideology’ of decolonization that rests on ‘forcing an ex-colony to forswear on pain of being forever under the yoke of colonization any and every cultural, political, intellectual, social and linguistic artefact, idea, process, institution and practice that retains even the slightest whiff of the colonial past’. 

Whether one should characterize the latter as simply a field of study or a potential set of policy arrangements remains unclear – yet what is certain is that it is too nebulous, too elastic, too open-ended to offer any substantive model or mechanism to understand postcolonial Africa. 
 

Correcting Eurocentric narcissism

 The decolonization research agenda in Africa came to prominence during the Cold War period of national liberation struggles.

The intellectual project that followed centred on dismantling Eurocentrism as colonial subjugation through its promotion of the West as the crucible of legitimate and scientific knowledge. Since then, scholars have argued that decolonization itself has become compromised by its enduringly Eurocentric gaze at the expense of the agency of African thinkers, creatives and statesmen and women. 

Taiwo seeks to correct this narcissism – and the omissions left in its wake – by introducing lesser-known Africans and pan-African scholars and cultural figures. These voices, he hopes, will illuminate issues often ignored by ‘decolonizers’ and spark a ‘renewed interest in an appreciation of the many different ways in which African thinkers have responded to the colonial experience’.
 

The decolonization of language

Taiwo challenges the decolonization of language as an oversold promise.

Romanticizing an imagined, pristine African pre-colonial past, he says, ultimately leads to nativism and atavism. As a case in point, Taiwo highlights bureaucratic instances of ‘language policy planning’ to deploy African languages in places such as Niger, Mali, Cameroon, Senegal and Nigeria that were hindered by multilingualism, education and high rates of illiteracy.

The author goes on to confront the abstract language of decolonization, which, he says, allows western scholars to unproblematically engage with the concept without any serious consideration of their own complicity in upholding systems of exclusion. It entrenches their own institutional power within the academy, amplifies their perspectives at the expense of others, and limits the possibilities for understanding the problems of world politics with deleterious effects on policy.

It is a serious claim, but there are issues to be addressed: Taiwo assumes there is coherence among scholars of decolonization, which is not the case. 

When Taiwo approaches how to foster political systems that cater to the needs of their citizens he dismantles the binary of ‘West as modern’ v ‘Africa as traditional’. Chieftaincies as traditional African governance, he points out, were the product of colonial anthropology, not Africans themselves. From the Fanti Confederation of 1871 to the Egba United Government in what is now Nigeria, Taiwo demonstrates that there has been a sustained tradition towards demands for democratic values. 

As he concedes an intellectual neglect of African philosophers that underlies the design and operations of Africa’s political institutions, Taiwo’s initial dismissal of the significance of cultural decolonization deserves another look. How should political and economic drives toward self-determination be advanced in the absence of knowledge shaped and mediated through African lived experiences?

In this respect, the tale of two decolonizations – the legal alongside the ideological – suggest an unhelpful, if not false, binary.
 

The problem of reconciling modernity and colonialism

What resonates throughout the book is the idea that Europe cannot profess to hold an exclusive intellectual claim to modernity. Its universal aspirations are open to all of humanity, allowing those who have historically been marginalized to be worldmakers. 

The idea that modernity and colonialism are irreconcilable is problematic. For instance, Taiwo argues that the curtailment of capitalism in Africa by restricting the growth of the middle classes while limiting competition between African capitalists and the metropole is the consequence of colonialism.

Yet the celebrated cultural anthropologist Sidney Mintz established an understanding that the matter for debate is not whether non-westerners were part of the modern system, but how and to what degree they were included and able to actualise its ideals. 

The emerging capitalist world economy needed non-western lands and labour, and so they were conscripted to this end. Recent abolitionist and black radical scholarship has built on this argument to maintain that capitalism not only requires inequality for it to function but that race – as a mechanism for producing ‘difference’ – enshrines it.

Acknowledging the unacknowledged

In the end, Taiwo communicates a palpable frustration at the state of academic discourses on contemporary Africa under the guise of emancipatory and radical scholarship. He offers an alternative approach whereby African students might rid themselves of a faddism that is ‘at best unsatisfactory’ and at worst produces ‘confusion, obscurantism, if not outright distortion and falsification’.

Yet out of this irritation, Taiwo’s greatest contribution in Against Decolonization might be to urge an acknowledgement of how and to what degree decolonization has become subdued and its political possibilities curtailed. He ultimately urges us to reconsider the purpose of the decolonization academic movement as an ethics to abide by rather than a social theory of the postcolonial world. 

This requires those ‘decolonizers’ on whose careers the term is built to adopt greater intellectual humility – to resist the posture of the anarchist radical scholar armed for the ‘good fight’. Instead, they should apply a scholarly curiosity to genuinely engage with those already on the battlefield, so to speak; those ‘doing the work’ in practice, but who have been unacknowledged until now.

Visual Abstract

Jessica Y. Franco
Dec 1, 2020; 19:1936-1951
Research

Toma Keser
Dec 29, 2020; 0:RA120.002433v1-mcp.RA120.002433
Research

Ji Eun Kim
Dec 20, 2020; 0:RA120.002159v1-mcp.RA120.002159
Research

Qin Zhang
Nov 17, 2020; 0:RA120.002325v1-mcp.RA120.002325
Research

Diana Samodova
Dec 1, 2020; 19:2139-2156
Technological Innovation and Resources

Gle1 is a conserved, essential regulator of DEAD-box RNA helicases, with critical roles defined in mRNA export, translation initiation, translation termination, and stress granule formation. Mechanisms that specify which, where, and when DDXs are targeted by Gle1 are critical to understand. In addition to roles for stress-induced phosphorylation and inositol hexakisphosphate binding in specifying Gle1 function, Gle1 oligomerizes via its N-terminal domain in a phosphorylation-dependent manner. However, a thorough analysis of the role for Gle1 self-association is lacking. Here, we find that Gle1 self-association is driven by two distinct regions: a coiled-coil domain and a novel 10-amino acid aggregation-prone region, both of which are necessary for proper Gle1 oligomerization. By exogenous expression in HeLa cells, we tested the function of a series of mutations that impact the oligomerization domains of the Gle1A and Gle1B isoforms. Gle1 oligomerization is necessary for many, but not all aspects of Gle1A and Gle1B function, and the requirements for each interaction domain differ. Whereas the coiled-coil domain and aggregation-prone region additively contribute to competent mRNA export and stress granule formation, both self-association domains are independently required for regulation of translation under cellular stress. In contrast, Gle1 self-association is dispensable for phosphorylation and nonstressed translation initiation. Collectively, we reveal self-association functions as an additional mode of Gle1 regulation to ensure proper mRNA export and translation. This work also provides further insight into the mechanisms underlying human gle1 disease mutants found in prenatally lethal forms of arthrogryposis.