As I walked into the embalming room at Jones Funeral Home and Supplies in Kingston on Sunday, I immediately felt the weight of the room. The air was thick with the scent of various chemicals used in the trade permeating the space. Tools such as...

Recent studies have suggested that innate immune responses exhibit characteristics associated with memory linked to modulations in both vertebrates and invertebrates. However, the diverse evolutionary paths taken, particularly within the invertebrate taxa, should lead to similarly diverse innate immunity memory processes. Our understanding of innate immune memory in invertebrates primarily comes from studies of the fruit fly Drosophila melanogaster, the generality of which is unclear. Caenorhabditis elegans typically inhabits soil harboring a variety of fatal microbial pathogens; for this invertebrate, the innate immune system and aversive behavior are the major defensive strategies against microbial infection. However, their characteristics of immunological memory remains infantile. Here we discovered an immunological memory that promoted avoidance and suppressed innate immunity during reinfection with bacteria, which we revealed to be specific to the previously exposed pathogens. During this trade-off switch of avoidance and innate immunity, the chemosensory neurons AWB and ADF modulated production of serotonin and dopamine, which in turn decreased expression of the innate immunity-associated genes and led to enhanced avoidance via the downstream insulin-like pathway. Therefore, our current study profiles the immune memories during C. elegans reinfected by pathogenic bacteria and further reveals that the chemosensory neurons, the neurotransmitter(s), and their associated molecular signaling pathways are responsible for a trade-off switch between the two immunological memories.

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.

Arabinogalactan proteins (AGPs) are plant proteoglycans with functions in growth and development. However, these functions are largely unexplored, mainly because of the complexity of the sugar moieties. These carbohydrate sequences are generally analyzed with the aid of glycoside hydrolases. The exo-β-1,3-galactanase is a glycoside hydrolase from the basidiomycete Phanerochaete chrysosporium (Pc1,3Gal43A), which specifically cleaves AGPs. However, its structure is not known in relation to its mechanism bypassing side chains. In this study, we solved the apo and liganded structures of Pc1,3Gal43A, which reveal a glycoside hydrolase family 43 subfamily 24 (GH43_sub24) catalytic domain together with a carbohydrate-binding module family 35 (CBM35) binding domain. GH43_sub24 is known to lack the catalytic base Asp conserved among other GH43 subfamilies. Our structure in combination with kinetic analyses reveals that the tautomerized imidic acid group of Gln263 serves as the catalytic base residue instead. Pc1,3Gal43A has three subsites that continue from the bottom of the catalytic pocket to the solvent. Subsite −1 contains a space that can accommodate the C-6 methylol of Gal, enabling the enzyme to bypass the β-1,6–linked galactan side chains of AGPs. Furthermore, the galactan-binding domain in CBM35 has a different ligand interaction mechanism from other sugar-binding CBM35s, including those that bind galactomannan. Specifically, we noted a Gly → Trp substitution, which affects pyranose stacking, and an Asp → Asn substitution in the binding pocket, which recognizes β-linked rather than α-linked Gal residues. These findings should facilitate further structural analysis of AGPs and may also be helpful in engineering designer enzymes for efficient biomass utilization.

6 July 2020

15 July 2020

7 August 2020

16 September 2020

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.

Cancer cachexia is characterized by reductions in peripheral lean muscle mass. Prior studies have primarily focused on increased protein breakdown as the driver of cancer-associated muscle wasting. Therapeutic interventions targeting catabolic pathways have, however, largely failed to preserve muscle mass in cachexia, suggesting that other mechanisms might be involved. In pursuit of novel pathways, we used untargeted metabolomics to search for metabolite signatures that may be linked with muscle atrophy. We injected 7-week–old C57/BL6 mice with LLC1 tumor cells or vehicle. After 21 days, tumor-bearing mice exhibited reduced body and muscle mass and impaired grip strength compared with controls, which was accompanied by lower synthesis rates of mixed muscle protein and the myofibrillar and sarcoplasmic muscle fractions. Reductions in protein synthesis were accompanied by mitochondrial enlargement and reduced coupling efficiency in tumor-bearing mice. To generate mechanistic insights into impaired protein synthesis, we performed untargeted metabolomic analyses of plasma and muscle and found increased concentrations of two methylarginines, asymmetric dimethylarginine (ADMA) and NG-monomethyl-l-arginine, in tumor-bearing mice compared with control mice. Compared with healthy controls, human cancer patients were also found to have higher levels of ADMA in the skeletal muscle. Treatment of C2C12 myotubes with ADMA impaired protein synthesis and reduced mitochondrial protein quality. These results suggest that increased levels of ADMA and mitochondrial changes may contribute to impaired muscle protein synthesis in cancer cachexia and could point to novel therapeutic targets by which to mitigate cancer cachexia.

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.

Climate migration: Ways ahead from the next generation The World Today rsoppelsa.drupal 25 May 2022

Ella Dennis and Mike Higgins talk to young activists seeking solutions as global warming wreaks havoc in sub-Saharan Africa

Africa has the lowest carbon emissions per capita yet the highest rate of temperature increase in the world. Rising levels of desertification, drought and flooding are already forcing millions of Africans to relocate to find more stable livelihoods. 

The continent’s youth will bear the brunt of this climate migration problem. It is estimated that by 2050, Africa will be home to 86 million internal climate migrants.

How is climate migration already affecting sub-Saharan Africa and what frameworks could tackle it? To begin to answer those questions, five young activists from across the region, who are members of Chatham House’s Common Futures Conversations, took part in a panel discussion at the world’s first youth-led Conference on Climate Migration, convened in April by the Alliance for Citizen Engagement, a nonpartisan think tank based in the US. 

The conversation and follow-up discussions focused on a common problem – climate migration brings people into conflict and puts pressure on infrastructure. 

In Kenya, droughts have left 3.5 million people hungry and the chronic flooding of several lakes in the Rift Valley has displaced hundreds of thousands, said Gerald Muchiri, 29, a social scientist from Kenya. One result has been outbreaks of violence between pastoralists such as the Orma people and the farmers of the Pokomo community, said Laura Mukhwana, 33, a PhD student in Kenya. She believes this violence is likely to worsen. ‘Inter-group conflicts will pose even larger security concerns for surrounding communities as climate migration intensifies,’ she said.

Suleman Nuhu, 24, a farmer and veterinary student from Nigeria, said farmer-herder conflicts were his country’s most significant climate-migration issue. The movement of nomadic tribes from the north had affected him personally: ‘Nomads have trespassed on [my family’s] farms many times while moving with their livestock, destroying our crops.’ 

Changes in climate also force people to move from rural to urban areas. Nigeria, for instance, struggles with the so-called ‘Lagos problem’, said Temiloluwa Lawal, 25, a lawyer and researcher from Nigeria. An estimated 22 million people, a number that is rising fast, are crammed into a city smaller than Greater London. While not on the same scale, Zimbabwe experiences comparable challenges, said Tinotenda Dube, 29, a Zimbabwean finance director. Thanks to drought, unemployed rural migrants arriving in cities ‘put excessive pressure on service delivery against a low tax base,’ he said. ‘People, including close family members of mine, are crowded in dilapidated homes because they cannot afford to pay rent for decent housing.’ 

But there is hope, say the activists. Dube believes that affordable housing is an ‘integral component of [tackling] the climate migration crisis’. 

In Zimbabwe, he has developed a low-cost home finance model that, he said, has helped more than 250 low-income households find good-quality accommodation. Alongside this initiative, Dube has co-founded a property and construction company, Solinfra Zimbabwe Private Ltd, to provide low-cost housing. 

Muchiri is taking action in Kenya, founding an NGO called Social Assistance Welfare to tackle public health issues, he said: ‘As climate migration becomes more intense, I expect preventable health issues to increase throughout the region, and thus see Social Assistance Welfare as an important mitigation.’

In Nigeria, Nuhu noted that to help reduce conflict between farmers and herders social-media campaigns are encouraging pastoralists to move from nomadic livestock farming to more efficient intensive systems, using ranching and grazing reserves. ‘As for food security problems, the best mitigation is to reduce reliance on rain-fed agriculture through irrigation schemes,’ he said. 

All five agreed that, in their experience, the youth of sub-Saharan Africa could be better informed about climate migration. But they took encouragement from the fact the young are passionate about tackling issues arising from the broader climate crisis. 

In Kenya, Mukhwana pointed to successful youth projects around agro-forestry and tree-planting. She added that there is ‘a growing movement of urban youth who are advocating for climate justice, such as the Kenyan Youth Environmental Network and Fridays for the Future Kenya’. It was pleasing too, she said, that when the Kenyan government revised its contributions to the Paris Climate Accords it staged a week-long youth conference to include their opinions.

‘Overall, I am quite hopeful about how the youth are mobilizing themselves in Kenya,’ she added.

Find out more about Chatham House’s Common Futures Conversations
 

COP27: Navigating a difficult road to Sharm El-Sheikh Expert comment NCapeling 6 July 2022

Against a backdrop of rising urgency, COP27 in Egypt will bring all aspects of climate action into the spotlight – but especially the role of the host country.

As COP26 drew to a close in Glasgow, Egyptian officials announced their priorities for COP27, emphasizing climate finance and climate adaptation – a new approach given previous COPs mainly focused on mitigation, reducing emissions to limit climate damage.

This was followed by the COP27 presidency outlining its vision at MENA Climate Week 2022 to achieve ‘substantive and equal progress’ on all aspects of the negotiations, and Egypt emphasizing its intention to focus on implementing existing carbon reduction targets rather than pushing for further carbon cuts.

Egypt argues it is hosting COP27 on behalf of African nations and that, while it is promoting the interests of the developing world, it will be an impartial arbiter. However it is also useful to consider its priorities from the Egyptian government’s perspective.

Agenda drivers

Egypt has long prioritized climate finance and adaptation because it remains in need of technical and financial support to adapt, especially in agriculture and tourism.

It plans to expand its access to climate funding and investment, an area in which Egypt has been relatively successful as it currently receives 27 per cent of all multilateral climate finance in the MENA region and has issued the region’s first sovereign green bonds.

With public debt currently 94 per cent of GDP, Egyptian officials have also called for debt relief for Egypt and other developing countries.

Egypt’s Climate Change Strategy reflects this approach, aiming to enhance Egypt’s rank on the Climate Change Performance Index in order to ‘attract more investments and acquire more climate funding’.

Limiting the mitigation scope and the focus on finance also echoes Egypt’s own reluctance to make carbon reduction commitments. The Egyptian nationally determined contribution (NDC) – its 2030 pledge under the Paris Agreement – does not include any quantifiable emission reduction targets.

Egypt is one of only a few countries which failed to submit an updated NDC in 2021 and its upcoming update will not include an economy-wide carbon reduction target.

Egypt has also never published a long-term strategy and has no decarbonization plans despite independent estimates it should cut rising emissions by one-quarter by 2030, and by two-thirds by 2050 to be aligned with the Paris Agreement. This partly explains why observers rate Egypt’s climate action as highly insufficient.

Furthermore, Egypt’s championing of ‘moving from pledges to implementation’ without having quantifiable carbon reduction pledges of its own effectively exempts it from both pledging and implementation.

As a developing country, Egypt’s negotiating position is supported by UNFCCC provisions which recognize differentiated responsibilities and respective capabilities of nations.

Its proposal to focus COP27 on the implementation of climate action and finance pledges is important in consolidating progress. But not pushing for more emission reductions at this critical moment risks derailing global decarbonization momentum and undermining global climate action.

According to optimistic estimates, if current climate pledges were implemented the world would still remain on track for 2°C of warming by the end of the century, with far worse impacts than if warming was curbed at 1.5°C.

Under a 2°C scenario, 37 per cent of the global population could regularly be exposed to extreme heat waves compared to 14 per cent in a 1.5°C warmer world, with developing countries expected to be worst-affected.

A 2°C trajectory also runs the risk of tipping points such as the melting of ice sheets in Antarctica and Greenland, triggering runaway climate change. Time to change the warming trajectory is running out as the latest IPCC assessment warns the window of opportunity is now ‘brief and rapidly closing’, and the UN Secretary General recently called for faster carbon cuts by the end of 2022 to avoid a ‘climate catastrophe’.

A different energy transition

Egypt opted not to join any of the voluntary sectoral coalitions at COP26 on reducing methane, clean energy transition, transition to zero-emissions vehicles, or moving beyond oil and gas.

This position is explained by its growing role as an exporter and advocate for fossil gas in the energy transition. Egypt is the second-largest producer of natural gas in Africa and is emerging as a fossil gas hub for the eastern Mediterranean, which is shaping its domestic energy policy.

Its 59GW electricity generation capacity is almost double the peak demand and is dominated by gas-powered electricity generation, which currently represents 42 per cent of all Africa’s gas generation.

Egypt’s climate policy is also shaped by fossil gas, and its national Climate Change Strategy encourages the expansion of gas use by promoting a transition to compressed natural gas for vehicles, the expansion of its domestic natural gas network – despite having universal access to electricity – and shifting to a gas-fuelled shipping sector.

Egypt also voiced support for other African countries to extract and deploy fossil gas and oil resources, making it one of the protagonists of the ‘great fossil gas pushback’. These advocates defend the right of developing countries to deploy fossil gas as a ‘transition fuel’ and champion its necessity to solve energy poverty.

But their position is not shared by all African and developing countries, and is rejected by some civil society groups, who argue it risks locking in greenhouse gases and local emissions for decades as well as delaying future development of low carbon energy systems.

Egypt’s huge spare generation capacity has contributed to a slowdown in renewable energy projects over the past two years. With renewables representing just 6GW, Egypt is expected to miss its renewable energy target for 2022, set at 20 per cent of generating capacity.

Engaging Egypt better

But these positions are more malleable than they seem, and Egypt is open to dialogue – not just on refining the COP27 agenda but also on reviewing its own climate priorities and leveraging its energy sector for a more ambitious transition.

A booming tech sector can unleash pan-African trade The World Today mhiggins.drupal 31 July 2022

The new African Continental Free Trade Area must embrace hyperscale data centres, cross-border digital payments and other innovations to realise its potential.

The Africa Continental Free Trade Area (AfCFTA) not only lays the groundwork for a single market across the continent, it can act as a driving force to unleash the full potential of the technology revolution that is under way across the African continent. 

To help achieve this, the AfCFTA must go beyond simply lowering barriers to the movement of goods and services, to what the World Bank calls an ‘FDI [foreign direct investment] deep scenario’. This requires harmonizing policies on investment, competition, intellectual property rights and e-commerce to encourage FDI at a greater scale. 

The World Bank estimates that the AfCFTA could increase income across the continent by 7 per cent by 2035 (an additional $445 billion), mainly by boosting intra-regional trade in manufactured goods and lifting approximately 40 million people from extreme poverty. Under an FDI deep scenario, the projected income growth jumps to 9 per cent by 2035, supporting 50 million people out of extreme poverty. 

The initial focus of the AfCFTA is on movement of goods and services and the associated financial flows through the establishment of the Pan-African Payment and Settlement System (PAPSS), a technology that enables instant local currency payment across Africa without first converting to a hard currency. In addition, harmonizing policies and easing the movement of data could enable technology to accelerate the anticipated AfCFTA income growth.

Global venture capital is pouring in

There is no doubt the African tech industry is growing. In 2021, 681 African technology companies raised $5.2 billion in equity venture funding, up from $2 billion in 2019, according to Partech Partners’ annual Africa Tech Venture Capital report. 

It is understandable why the industry has attracted global venture capital. While tech businesses are often initially focused on meeting needs in their home markets, most have a strong desire to tap into the pan-African market, with its 1.3 billion consumers across 54 countries and a combined GDP of $3.4 trillion. This in turn should attract global venture capital to invest in Africa. 

The AfCFTA has created a framework for technology-led companies to scale across the continent in a way that will impact digital infrastructure, logistics, energy and much else. For example, Africa’s hyperscale data centre capacity would benefit from the ability to locate centres in the lowest cost jurisdiction with the best energy availability and to use that to power cloud storage across the continent.

Yet various regulatory constraints, including the desire for each state to own its population’s data on local servers, prevent that. As a result, African data centres are less competitive than those in America and China. 

Similarly, logistics and other sectors would be transformed if the information on goods in transit, such as digital customs documentation, could move easily across borders while being tracked across all 54 countries. Financial services would also benefit from the ability to pay across borders in a low-cost, frictionless way.

Fintech companies should be encouraged to build technology solutions linking to PAPSS and other initiatives to accelerate the adoption-of-use cases that PAPSS supports – such as intra-Africa instant payment, embedded finance and remittances services.

AfCFTA may also unlock mergers and acquisitions (M&A) activity among African and international firms. Technology companies are using M&A to enter new markets, as the international payments platform Stripe did when it acquired the Nigerian business Paystack, and the payments business MFS Africa did when it took over the fintech start-up Baxi. 

Governments and regulators must support innovation

Given the difficulty of a country-by-country organic growth strategy across Africa, M&A is likely to increase in various technology sectors over the next few years. With the anticipated ease of doing business that the AfCFTA could facilitate, we are likely to witness further welcome consolidation, creating larger corporates that create more jobs and increase tax revenues. 

To unlock the benefits that technology will bring, governments and regulators need to play a supportive role in encouraging innovation. They will need to ensure the appropriate consumer protections are in place without stifling creativity through regulation, inefficiencies or rent-seeking. 

At the same time, governments and regulators should not permit themselves to be held to ransom by dominant incumbents, such as banks and mobile operators in the fintech space, at the expense of stifling technology companies looking to disrupt their respective industries. 

Only then will the AfCFTA allow Africa to benefit from its tech potential. 

Risana Zitha writes this article in a personal capacity

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.

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Researchers use dynamic PET imaging with target-selective tracer molecules to probe molecular processes. Kinetic models have been developed to describe these processes. The models are typically fitted to the measured PET data with the assumption that the brain is in a steady-state condition for the duration of the scan. The end results are quantitative parameters that characterize the molecular processes. The most common kinetic modeling endpoints are estimates of volume of distribution or the binding potential of a tracer. If the steady state is violated during the scanning period, the standard kinetic models may not apply. To address this issue, time-variant kinetic models have been developed for the characterization of dynamic PET data acquired while significant changes (e.g., short-lived neurotransmitter changes) are occurring in brain processes. These models are intended to extract a transient signal from data. This work in the PET field dates back at least to the 1990s. As interest has grown in imaging nonsteady events, development and refinement of time-variant models has accelerated. These new models, which we classify as belonging to the first, second, or third generation according to their innovation, have used the latest progress in mathematics, image processing, artificial intelligence, and statistics to improve the sensitivity and performance of the earliest practical time-variant models to detect and describe nonsteady phenomena. This review provides a detailed overview of the history of time-variant models in PET. It puts key advancements in the field into historical and scientific context. The sum total of the methods is an ongoing attempt to better understand the nature and implications of neurotransmitter fluctuations and other brief neurochemical phenomena.

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The Internet is full of cats—and in this case, malware-delivering fake cat websites used for very targeted search engine optimization.

Alison M. Kurimchak
Dec 1, 2020; 19:2068-2089
Research

Litong Nie
Dec 1, 2020; 19:2015-2029
Research

Weixian Deng
Dec 22, 2020; 0:RA120.002411v1-mcp.RA120.002411
Research

Juntuo Zhou
Nov 30, 2020; 0:RA120.002384v1-mcp.RA120.002384
Research

Mitochondrial dysfunction is associated with a variety of human diseases including neurodegeneration, diabetes, nonalcohol fatty liver disease (NAFLD), and cancer, but its underlying causes are incompletely understood. Using the human hepatic cell line HepG2 as a model, we show here that endoplasmic reticulum-associated degradation (ERAD), an ER protein quality control process, is critically required for mitochondrial function in mammalian cells. Pharmacological inhibition or genetic ablation of key proteins involved in ERAD increased cell death under both basal conditions and in response to proinflammatory cytokines, a situation frequently found in NAFLD. Decreased viability of ERAD-deficient HepG2 cells was traced to impaired mitochondrial functions including reduced ATP production, enhanced reactive oxygen species (ROS) accumulation, and increased mitochondrial outer membrane permeability. Transcriptome profiling revealed widespread down-regulation of genes underpinning mitochondrial functions, and up-regulation of genes associated with tumor growth and aggression. These results highlight a critical role for ERAD in maintaining mitochondrial functional and structural integrity and raise the possibility of improving cellular and organismal mitochondrial function via enhancing cellular ERAD capacity.

Autophagy plays critical roles in the maintenance of endothelial cells in response to cellular stress caused by blood flow. There is growing evidence that both cell adhesion and cell detachment can modulate autophagy, but the mechanisms responsible for this regulation remain unclear. Immunoglobulin and proline-rich receptor-1 (IGPR-1) is a cell adhesion molecule that regulates angiogenesis and endothelial barrier function. In this study, using various biochemical and cellular assays, we demonstrate that IGPR-1 is activated by autophagy-inducing stimuli, such as amino acid starvation, nutrient deprivation, rapamycin, and lipopolysaccharide. Manipulating the IκB kinase β activity coupled with in vivo and in vitro kinase assays demonstrated that IκB kinase β is a key serine/threonine kinase activated by autophagy stimuli and that it catalyzes phosphorylation of IGPR-1 at Ser220. The subsequent activation of IGPR-1, in turn, stimulates phosphorylation of AMP-activated protein kinase, which leads to phosphorylation of the major pro-autophagy proteins ULK1 and Beclin-1 (BECN1), increased LC3-II levels, and accumulation of LC3 punctum. Thus, our data demonstrate that IGPR-1 is activated by autophagy-inducing stimuli and in response regulates autophagy, connecting cell adhesion to autophagy. These findings may have important significance for autophagy-driven pathologies such cardiovascular diseases and cancer and suggest that IGPR-1 may serve as a promising therapeutic target.

Protein biosynthesis is fundamental to cellular life and requires the efficient functioning of the translational machinery. At the center of this machinery is the ribosome, a ribonucleoprotein complex that depends heavily on Mg2+ for structure. Recent work has indicated that other metal cations can substitute for Mg2+, raising questions about the role different metals may play in the maintenance of the ribosome under oxidative stress conditions. Here, we assess ribosomal integrity following oxidative stress both in vitro and in cells to elucidate details of the interactions between Fe2+ and the ribosome and identify Mn2+ as a factor capable of attenuating oxidant-induced Fe2+-mediated degradation of rRNA. We report that Fe2+ promotes degradation of all rRNA species of the yeast ribosome and that it is bound directly to RNA molecules. Furthermore, we demonstrate that Mn2+ competes with Fe2+ for rRNA-binding sites and that protection of ribosomes from Fe2+-mediated rRNA hydrolysis correlates with the restoration of cell viability. Our data, therefore, suggest a relationship between these two transition metals in controlling ribosome stability under oxidative stress.

We have observed overexpression of PACS-1, a cytosolic sorting protein in primary cervical tumors. Absence of exonic mutations and overexpression at the RNA level suggested a transcriptional and/or posttranscriptional regulation. University of California Santa Cruz genome browser analysis of PACS-1 micro RNAs (miR), revealed two 8-base target sequences at the 3' terminus for hsa-miR-34a and hsa-miR-449a. Quantitative RT-PCR and Northern blotting studies showed reduced or loss of expression of the two microRNAs in cervical cancer cell lines and primary tumors, indicating dysregulation of these two microRNAs in cervical cancer. Loss of PACS-1 with siRNA or exogenous expression of hsa-miR-34a or hsa-miR-449a in HeLa and SiHa cervical cancer cell lines resulted in DNA damage response, S-phase cell cycle arrest, and reduction in cell growth. Furthermore, the siRNA studies showed that loss of PACS-1 expression was accompanied by increased nuclear γH2AX expression, Lys382-p53 acetylation, and genomic instability. PACS-1 re-expression through LNA-hsa-anti-miR-34a or -449a or through PACS-1 cDNA transfection led to the reversal of DNA damage response and restoration of cell growth. Release of cells post 24-h serum starvation showed PACS-1 nuclear localization at G1-S phase of the cell cycle. Our results therefore indicate that the loss of hsa-miR-34a and hsa-miR-449a expression in cervical cancer leads to overexpression of PACS-1 and suppression of DNA damage response, resulting in the development of chemo-resistant tumors.

The kinesin-3 family contains the fastest and most processive motors of the three neuronal transport kinesin families, yet the sequence of states and rates of kinetic transitions that comprise the chemomechanical cycle and give rise to their unique properties are poorly understood. We used stopped-flow fluorescence spectroscopy and single-molecule motility assays to delineate the chemomechanical cycle of the kinesin-3, KIF1A. Our bacterially expressed KIF1A construct, dimerized via a kinesin-1 coiled-coil, exhibits fast velocity and superprocessivity behavior similar to WT KIF1A. We established that the KIF1A forward step is triggered by hydrolysis of ATP and not by ATP binding, meaning that KIF1A follows the same chemomechanical cycle as established for kinesin-1 and -2. The ATP-triggered half-site release rate of KIF1A was similar to the stepping rate, indicating that during stepping, rear-head detachment is an order of magnitude faster than in kinesin-1 and kinesin-2. Thus, KIF1A spends the majority of its hydrolysis cycle in a one-head-bound state. Both the ADP off-rate and the ATP on-rate at physiological ATP concentration were fast, eliminating these steps as possible rate-limiting transitions. Based on the measured run length and the relatively slow off-rate in ADP, we conclude that attachment of the tethered head is the rate-limiting transition in the KIF1A stepping cycle. Thus, KIF1A's activity can be explained by a fast rear-head detachment rate, a rate-limiting step of tethered-head attachment that follows ATP hydrolysis, and a relatively strong electrostatic interaction with the microtubule in the weakly bound post-hydrolysis state.

Astrid M. Moerman
Dec 23, 2020; 0:jlr.RA120000974v1-jlr.RA120000974
Research Articles

Genta Kakiyama
Dec 1, 2020; 61:1629-1644
Research Articles

Ying Zou
Dec 1, 2020; 61:1589-1604
Research Articles

Akemi Kakino
Nov 3, 2020; 0:jlr.RA120000767v1-jlr.RA120000767
Research Articles

Amanda D.V. MacCannell
Nov 18, 2020; 0:jlr.ILR120001204v1-jlr.ILR120001204
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