Myosins generate force and motion by precisely coordinating their mechanical and chemical cycles, but the nature and timing of this coordination remains controversial. We utilized a FRET approach to examine the kinetics of structural changes in the force-generating lever arm in myosin V. We directly compared the FRET results with single-molecule mechanical events examined by optical trapping. We introduced a mutation (S217A) in the conserved switch I region of the active site to examine how myosin couples structural changes in the actin- and nucleotide-binding regions with force generation. Specifically, S217A enhanced the maximum rate of lever arm priming (recovery stroke) while slowing ATP hydrolysis, demonstrating that it uncouples these two steps. We determined that the mutation dramatically slows both actin-induced rotation of the lever arm (power stroke) and phosphate release (≥10-fold), whereas our simulations suggest that the maximum rate of both steps is unchanged by the mutation. Time-resolved FRET revealed that the structure of the pre– and post–power stroke conformations and mole fractions of these conformations were not altered by the mutation. Optical trapping results demonstrated that S217A does not dramatically alter unitary displacements or slow the working stroke rate constant, consistent with the mutation disrupting an actin-induced conformational change prior to the power stroke. We propose that communication between the actin- and nucleotide-binding regions of myosin assures a proper actin-binding interface and active site have formed before producing a power stroke. Variability in this coupling is likely crucial for mediating motor-based functions such as muscle contraction and intracellular transport.

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. 

Twenty Years After Hong Kong Handover, Does ‘One Country, Two Systems’ Still Work? Expert comment sysadmin 28 June 2017

This unique constitutional framework can endure – if Hong Kong society can reconcile its different visions of the future.

Twenty years after the handover of Hong Kong from British to Chinese sovereignty, the ‘one country, two systems’ arrangement – the main aim of which was to guarantee the continuity of Hong Kong’s open society and way of life – can be said to have worked well. Street protests remain a regular feature of Hong Kong’s political culture. Freedom of information and expression are alive and well. Hong Kong retains its ‘capitalist way of life’, its legal system based on common law and independent judiciary, and its status as an international financial centre. As a result the city remains one of the most open economies across Asia, with robust institutions and transparency which are hard to find anywhere else in the region.

Yet the 79-day ‘occupy’ protests of autumn 2014 showed that something is not quite right in the city of Hong Kong.

The protests themselves had a number of causes. Partly they reflected socioeconomic concerns, especially the rise in income inequality and lack of affordable housing. These might have been dealt with to some extent by better governance over the years, but they are also a feature of many societies in the current phase of globalization – a case, perhaps, of too much ‘capitalist way of life’.

Politically, the desire expressed by many in 2014 was for a form of ‘genuine universal suffrage’ for the selection of Hong Kong’s chief executive which went beyond a provision of Hong Kong’s mini constitution, the Basic Law, that candidates should be put forward by a ‘nominating committee’. It was on this point that the possibility of constitutional reform foundered in 2015, leaving Hong Kong no further ahead in its ‘gradual progress’ towards democracy.

But this episode also brought to the surface the tension between different visions for Hong Kong’s future. In particular, many in Hong Kong are still uncomfortable with the ‘one country’ part of the deal, rejected by some (especially young people) in the ways that they conceptualize Hong Kong identity – according to one recent survey, as little as 3.1% of Hong Kong youths identify themselves as ‘Chinese’. These issues are likely to constrain political development for some time to come.

At their sharpest, some of these visions are for some form of self-determination, or even independence, for Hong Kong. This is not just anathema to the national authorities in Beijing, but contradicts a basic tenet of Hong Kong’s handover in 1997, the return to Chinese sovereignty. This is not just something on which Beijing will never compromise, but will seek to challenge.

It is this which explains the sense in Hong Kong that the central government has been looking to become politically more involved since 2014. But the challenge of influencing Hong Kong society is great, and other than strengthening relations with the establishment camp, Beijing has not been able to tighten its grip. If anything, the centre of gravity of Hong Kong politics has continued to drift away from Beijing, not towards it.

How this will play out remains to be seen. Some amelioration of social tensions could help. But the fundamental divergence in visions of Hong Kong’s future will not be resolved so easily.

Looking forward therefore, the key to the continued success of ‘one country, two systems’ lies in Hong Kong society. If mainstream acceptance of the compromises involved can return, then this unique constitutional framework can still work for years to come.

‘Hong Kong is now in the hands of its people – they cannot rely on others to stick up for them now.’ Expert comment sysadmin 29 June 2017

Kerry Brown on ‘one country, two systems’, the UK’s diminishing influence and the territory’s future, 20 years after the handover.

1 July marks the 20th anniversary of the transfer of Hong Kong’s sovereignty from Britain to China. Kerry Brown speaks with Jason Naselli about what the future holds for the territory.

How sustainable is the ‘one country, two systems’ framework? Will the arrangement last the full 50 years (until 2047) as originally envisioned?

It is questionable whether the arrangement that exists today was the one envisioned in 1997 when the handover happened. It was always a very abstract, flexible system, granting Hong Kong a high degree of autonomy, meaning it could maintain its capitalist system. Of course, in the lead up to 1997 all these things were broadly seen as being in Beijing’s interests to preserve.

But these days, the one thing that few said in 1997 has come to pass – the People’s Republic has maintained one-party rule as a political system, but become one of the world’s great economies. It has been so far a huge success.

Hong Kong therefore has diminished in importance over the years to the point that maintaining at least some semblance of one country, two systems is almost like an act of charity. It has been nibbled at, compromised and seems to grow weaker by the day. Most in Hong Kong would say there is a system: one country, one system. That’s the deal.

The central government’s deepening involvement in the territory’s politics is a subject of growing controversy in Hong Kong. Does the Chinese government need to alter its approach?

Not particularly. It doesn’t want to see Hong Kong fail as an economy. That doesn’t suit its interests at all. But nor does it want a truculent, disobedient polity that is meant to be part of its sovereign territory.

So it has increasingly set political parameters. Hong Kong can have its unique system – as long as it is obedient. And on the whole, that is the deal that all of the city’s chief executives until now have internally understood perfectly.

As part of the 1997 handover, the UK has ‘a continuing moral and political obligation’ to Hong Kong. How will this relationship play out as Brexit shifts Britain’s place in the world?

The Foreign Office offers a six-monthly report to Parliament, updating on how the handover deal is going. As the years go on, however, it becomes increasingly illusive how the UK has any real locus to say much about the situation on Hong Kong. It did say, rightly, that the detainment of one of the booksellers taken in in 2015 was a violation of the treaty because he was British. This was the strongest wording that has ever appeared from an official British source. But with dependence on creating a new kind of relationship with China now foremost in people’s minds because of Brexit and other economic pressures, it is not surprising that the priority increasingly lies elsewhere.

With direct management of Hong Kong gone, the UK was always going to be more and more irrelevant. That has happened. And in any case, relations with China have had to become more complex and multifaceted. Hong Kong was always the tail wagging the dog for the UK relations with China. Now there has been a rebalancing, the calculation always has to be how much unilaterally supporting Hong Kong will damage relations with Beijing. This has become an increasingly asymmetrical question: in a playoff, preserving links with Beijing will always prevail. That’s just the reality of the new world we are seeing come into being.

Hong Kong has played an important financial role for China over the past 20 years, but where will it fit as markets and financial institutions on the mainland mature?

It maintains is role as a major RMB hub, and as a finance centre. But it is surrounded by competition. Singapore, and Sydney, and other places in the region have RMB deals. Shanghai and Tianjin aspire to be portals for entry to the domestic Chinese market. Hong Kong every day has to think of new ways to maintain its relevance and beat back competition. So far, it has done well. But this is an issue it can never be complacent about.

What has been the most significant change in Hong Kong society since 1997?

The rising cultural and linguistic influence of the mainland on Hong Kong. Hong Kong has maintained its difference – but it has had to change. It is clear that Hong Kong is now in the hands of Hong Kongese – they cannot rely on others to stick up for them now. The culture, identity and future of the territory are in their hands. In that sense, they have autonomy.

Climate Change and the Pacific: Impacts and Adaptation 27 November 2018 — 8:30AM TO 10:00AM Anonymous (not verified) 14 November 2018 Royal Academy of Arts

Rethinking European and Afghan policy approaches to migration 9 February 2021 — 12:30PM TO 1:30PM Anonymous (not verified) 19 January 2021 Online

Speakers argue for a more multidimensional approach to migration, and for a nuanced reassessment of policy.

Please note this is an online event. Please register using the link below to finalize your registration.

Afghanistan is a key country of origin for asylum seekers in Europe, and the prime global recipient of EU development assistance. It was one of the first nations to conclude a migration partnership agreement with the EU, in 2016.

Implementation has been thwarted, however, by war and violence, limited state capacity, entrenched economic deprivation, internal displacement and the unfolding impact of COVID-19.

The speakers argue for a more multidimensional approach to migration, and for a nuanced reassessment of policy. They underscore the strength of Afghanistan’s responses to migration, returns, reintegration, security and peace, and point to the need for synchronizing the EU’s policy approaches.

They argue that effective policy must consider the historical significance of mobility for Afghanistan and the need for coherent regional responses to migration.

This event launches the publication The EU and the Politics of Migration Management in Afghanistan.

Forty-six mathematical scientists have been named recipients of AMS-Simons Research Enhancement Grants for Primarily Undergraduate Institution (PUI) Faculty. Each awardee will receive $3,000 per year for three years. 

The grants foster and support research collaboration by full-time mid-career mathematicians at US institutions that do not offer a mathematics doctoral degree.

This year’s grant recipients hail from 42 institutions across 21 US states. The grants will support their research in several different areas, from number theory to applied mathematics.

This is the grant program’s second cohort, said Sarah Bryant, associate vice president of programs. “Over the first two years, we’ve worked with faculty from 75 different institutions, including 19 minority-serving institutions, which shows just how much this program is expanding and making an impact,” Bryant said. She noted that “in the first year, the grants supported 87 trips, helped produce 70 publications and preprints, and gave awardees the resources needed to collaborate and advance their work.”

The grant allows for any activities that will further the awardee’s research program. Expenses include but are not limited to conference participation, institute visits, collaboration travel (awardee or collaborator), computer equipment or software, family-care expenses, and teaching assistants.

Administration of the award by the grantee’s institution is required; annual discretionary funds for a grantee’s department and administrative funds for a grantee's institution will be available at the end of each grant year.

The grants are made possible through funding from the Simons Foundation and the American Mathematical Society (AMS), as well as Eve, Kirsten, Lenore, and Ada of the Menger family.

Applications for the next cohort are anticipated to open on MathPrograms.org on January 9, 2025. Visit the AMS website to view an informational PowerPoint or sign up to receive email updates about the program. Faculty who applied for but did not receive the 2023 or 2024 awards are encouraged to reapply if they are still eligible for the grant. 

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.

α1-antitrypsin (AAT) regulates the activity of multiple proteases in the lungs and liver. A mutant of AAT (E342K) called ATZ forms polymers that are present at only low levels in the serum and induce intracellular protein inclusions, causing lung emphysema and liver cirrhosis. An understanding of factors that can reduce the intracellular accumulation of ATZ is of great interest. We now show that calreticulin (CRT), an endoplasmic reticulum (ER) glycoprotein chaperone, promotes the secretory trafficking of ATZ, enhancing the media:cell ratio. This effect is more pronounced for ATZ than with AAT and is only partially dependent on the glycan-binding site of CRT, which is generally relevant to substrate recruitment and folding by CRT. The CRT-related chaperone calnexin does not enhance ATZ secretory trafficking, despite the higher cellular abundance of calnexin-ATZ complexes. CRT deficiency alters the distributions of ATZ-ER chaperone complexes, increasing ATZ-BiP binding and inclusion body formation and reducing ATZ interactions with components required for ER-Golgi trafficking, coincident with reduced levels of the protein transport protein Sec31A in CRT-deficient cells. These findings indicate a novel role for CRT in promoting the secretory trafficking of a protein that forms polymers and large intracellular inclusions. Inefficient secretory trafficking of ATZ in the absence of CRT is coincident with enhanced accumulation of ER-derived ATZ inclusion bodies. Further understanding of the factors that control the secretory trafficking of ATZ and their regulation by CRT could lead to new therapies for lung and liver diseases linked to AAT deficiency.

Proteins in the α-macroglobulin (αM) superfamily use thiol esters to form covalent conjugation products upon their proteolytic activation. αM protease inhibitors use theirs to conjugate proteases and preferentially react with primary amines (e.g. on lysine side chains), whereas those of αM complement components C3 and C4B have an increased hydroxyl reactivity that is conveyed by a conserved histidine residue and allows conjugation to cell surface glycans. Human α2-macroglobulin–like protein 1 (A2ML1) is a monomeric protease inhibitor but has the hydroxyl reactivity–conveying histidine residue. Here, we have investigated the role of hydroxyl reactivity in a protease inhibitor by comparing recombinant WT A2ML1 and the A2ML1 H1084N mutant in which this histidine is removed. Both of A2ML1s' thiol esters were reactive toward the amine substrate glycine, but only WT A2ML1 reacted with the hydroxyl substrate glycerol, demonstrating that His-1084 increases the hydroxyl reactivity of A2ML1's thiol ester. Although both A2ML1s conjugated and inhibited thermolysin, His-1084 was required for the conjugation and inhibition of acetylated thermolysin, which lacks primary amines. Using MS, we identified an ester bond formed between a thermolysin serine residue and the A2ML1 thiol ester. These results demonstrate that a histidine-enhanced hydroxyl reactivity can contribute to protease inhibition by an αM protein. His-1084 did not improve A2ML1's protease inhibition at pH 5, indicating that A2ML1's hydroxyl reactivity is not an adaption to its acidic epidermal environment.

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.

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.

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.

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.

10 September 2020

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.

The online media changing African news The World Today mhiggins.drupal 2 August 2022

Africa’s news sites are gripping audiences with digital innovation and bold directions. Helen Fitzwilliam talks to editors at three platforms.

Lydia Namubiru
News editor of ‘The Continent’ (South Africa)

At the start of the pandemic, we realized a lot of fake news was being shared on WhatsApp. So, The Continent chose to launch on that platform to insert some real journalism in a way that could easily be shared. We now have about 100,000 readers across Africa and the rest of the world, but we had to dramatically change the way we write and edit stories: to compete with the likes of Twitter and Instagram, we try to keep stories tight at 300 words. 

There’s a real variety. We can run an investigation into corruption in the Democratic Republic of the Congo a week after a front page on the fashion designer who dresses Africa’s ‘big men’ [powerful leaders]. We cover feminist issues, the backlash against LGBT people in Ghana; we’ve had the Namibian first lady talking to us about misogyny. These are not the sort of topics a typical African newspaper is going to lead with.

With a story such as Ukraine, the war’s impact on the cost of living has been the most obvious angle for us. It has driven countries such as Malawi into crisis, forcing a devaluation of the currency.
 
As for the future, we see two issues looming. Workers’ economic rights and their treatment by multinationals will be a big story. There are refugees in camps in Kenya working in data operations and being paid a pittance to help create huge, potentially multimillion-dollar systems for US companies. 

Second, Africa has the world’s youngest population and the oldest leaders, so this will likely lead to activism and protests. The young are exposed to the global village, so they want different things and have different values. They speak a completely different language their leaders do not understand. It will be an interesting conflict, but could lead to real violence. 

John Githongo
Editor of ‘The Elephant’ (Kenya)

We set up this platform four years ago. Due to political and commercial pressures, mainstream media wasn’t doing much critical reporting. We have between 30,000 and 80,000 readers a week, the majority of them in Africa. 

The digital space reaches a completely different demographic. When The Elephant started, it was 80 per cent male and over 40, but we have gained more younger people and more women. Now it is 60 per cent men, 40 per cent women and that is something we have been working at. 

Our editorial approach is that as long as a piece has a strong argument and fits into our pan-African brief, we will publish it – even if we don’t agree with it.

The conflicts in Ethiopia and parts of the Sahel make the war in Ukraine pale in comparison. So many people have died in Ethiopia or been displaced and now we have the onset of a famine after four years of failed rain. During the 1960s and 1970s, when the Cold War found its way on to African soil, millions of people died – so there is caution about getting involved in a European fight.

There is always a lot of fake news around during elections. But people are beginning to be more sceptical. We go after those who attempt to change the level of debate with reputation-laundering and try to expose their actions. 
 
The future of democracy is going to be a big issue. When Africans were watching the attack on the US Capitol last year, they were hoping it was not a Black Lives Matter protest, which could have resulted in a ‘blackbath’. As soon as they saw the white guys wearing horns, people laughed with relief. 

There is an ongoing recalibration of Africa’s geopolitical relations with the rest of the world. A poll released in June showed China has overtaken the United States as the foreign power having the biggest positive influence in Africa in the eyes of young people across the continent. The younger generation is writing its own narrative. 

Wale Lawal
Editor of ‘The Republic’ (Nigeria)

Nigerian audiences are increasingly online and tend to read both local and international publications. They also know that the issues they care about are either under-reported or reported at lower quality levels. 

At The Republic, we provide political journalism that tends to require high levels of expertise. Yet online audiences also prioritize engagement: it is not enough for an issue to be important, it also needs to be interesting.

Some topics we have covered that Western media tend not to include how people experience blackness in different parts of the world; the waves of mostly female-led and youth-led movements rising up against autocratic governments across Africa; and relationships between countries within Africa itself. In the early days of the pandemic, we launched a Covid-19 and Africa series, having noticed a glaring lack of African expert voices in global media.
 
We also cover Africa’s evolving relations with Russia. Whenever we encounter a story like Russia’s invasion of Ukraine, the first thing we always ask ourselves is what missing voice can we add to the current discussion? All we were reading about after the invasion was how neighbouring countries were opening their borders and their homes to Ukrainians. Most people saw only that. 

But we knew that around 15,000 Africans were studying in Ukraine, that Africans routinely face harsh treatment at international borders, and that clearly their voices were missing from the discussion.

With fake news and information gaps on social media, our usual approach is to develop expert-led columns and circulate these as widely as possible.

Our next mission is to think about the role that independent media can play in supporting democracies, such as by increasing voter turnout. During the last election in Nigeria, less than 35 per cent of those who registered to vote eventually did so.

A natural climate change priority for Africa Expert comment LJefferson 28 September 2022

Nature-based solutions can protect African nations’ shared natural endowment and meet the needs of their people.

Africa’s principal climate change negotiators have long understood the important contribution of ‘nature-based solutions’ (NBS) in delivering land (and sea) based options as part of the goals of the Paris Agreement. Limiting temperature rises to only 1.5°C by 2050 will demand finding innovative ways to protect Africa’s vast natural endowment that also meets the equally acute needs of its people. Nature-based solutions may do both.

The urgency for Africa cannot be overstated. At a Chatham House conference in Libreville, the Gabonese minister for the environment highlighted that if global warming surges by 2.5° or 3°C the impact would be at least 6°C for Africa. Decision-makers on the continent and across the world need to understand that ‘business as usual’ cannot be an option given the potential for loss of life, conflict and chaos.

Adaption, mitigation, or both?

Although adaptation to climate change has hitherto tended to be the continent’s main concern, there has also been growing recognition of the ways that Africa’s natural environments, from forests and grasslands, to peatlands and coastal and marine ecosystems, all also mitigate its impacts by sequestering carbon. The Congo Basin alone is said to store upwards of 4 per cent of global emissions annually.

These environments are under increasing pressure. Deforestation is a sad reality, caused mostly by unsustainable and extensive agricultural practices focused on cash crops for export more than food production to feed local populations. And arguing that African states and peoples should slow the development of their economies and infrastructure in response to a crisis born of the already-industrialized world does not find a responsive audience in a continent hungry for jobs and opportunity.

Nature-based solutions offer an answer to this conundrum. There is growing evidence that natural habitats both help avoid losses from climate change-related disasters and can drive economic growth. There is thus potential for NBS to tackle both adaptation and mitigation challenges at relatively low cost.

NBS – the rocky road from commitment to policy

It was logical therefore for Africa and like-minded countries to work to integrate NBS more strongly into the climate change agenda at COP26. The final Glasgow Climate Pact duly emphasized the importance of protecting ecosystems. The Global Forest Finance Pledge signed in the margins was also significant. African focus, with COP 27 in Egypt soon to take place, is now on domestic implementation and delivery of these pledges. The new African Union Climate Change and Resilient Development strategy (2022-2032) sets out many of the challenges and opportunities.

Choosing the right development pathway is tough, requiring political will and inclusive governance. Besides the challenge of securing alternative national revenue if a country moves away from fossil-intensive fuels – particularly acute for Africa’s resource-producing states – there is a dizzying array of policy decisions to be taken. African governments need to choose the most appropriate renewable energy sources, secure alternative livelihoods and continue to meet basic needs of the most vulnerable in the context of radical restructuring.  

Towards African solutions

There can be no one-size-fits-all answer to these questions – it is sadly still necessary to underline the enormous geographic, cultural and political diversity of the continent – but African experts have begun to draw together some emerging common themes from work already underway.  

Maintaining the ‘status quo’ in agricultural practices is no longer an option. Emphasis on sustainable agriculture is urgently needed andthat includes the elaboration of a ‘new deal’ between nature and people.  

Conservation also needs to be reframed as an economic opportunity, particularly in the elaboration and development of ecosystem services that deliver the true value of Africa’s forests, and that involve, value and reward local communities, respecting their rights and livelihoods.

Regional cooperation is likewise key, including on the management of forest, wildlife and water resources – Africa’s ecosystems do not respect arbitrary political boundaries, and accomplishing the dual feat of protecting cross-border systems at the same time as realizing their economic potential will demand effective collaboration, as well as training, education and communication at all levels.

The imperative of finance

A further imperative will be securing sufficient developed country financing – whether that be to secure value for net sequestration and effective forest management or for models of context-appropriate ‘smarter’ sustainable rural conservation and ecosystem resilience.

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.

Visual Abstract

Wenhe Zhu
Dec 29, 2020; 0:RA120.002353v1-mcp.RA120.002353
Research

Yi Liu
Dec 1, 2020; 19:1968-1985
Research

Ryan J Lumpkin
Dec 2, 2020; 0:RA120.002414v1-mcp.RA120.002414
Research

Transient receptor potential vanilloid 1 (TRPV1) channel is a multimodal receptor that is responsible for nociceptive, thermal, and mechanical sensations. However, which biomolecular partners specifically interact with TRPV1 remains to be elucidated. Here, we used cDNA library screening of genes from mouse dorsal root ganglia combined with patch-clamp electrophysiology to identify the voltage-gated potassium channel auxiliary subunit Kvβ1 physically interacting with TRPV1 channel and regulating its function. The interaction was validated in situ using endogenous dorsal root ganglia neurons, as well as a recombinant expression model in HEK 293T cells. The presence of Kvβ1 enhanced the expression stability of TRPV1 channels on the plasma membrane and the nociceptive current density. Surprisingly, Kvβ1 interaction also shifted the temperature threshold for TRPV1 thermal activation. Using site-specific mapping, we further revealed that Kvβ1 interacted with the membrane-distal domain and membrane-proximal domain of TRPV1 to regulate its membrane expression and temperature-activation threshold, respectively. Our data therefore suggest that Kvβ1 is a key element in the TRPV1 signaling complex and exerts dual regulatory effects in a site-specific manner.

Post-transcriptional modifications of pre-mRNAs expand the diversity of proteomes in higher eukaryotes. In the brain, these modifications diversify the functional output of many critical neuronal signal molecules. In this study, we identified a brain-specific A-to-I RNA editing that changed glutamine to arginine (Q/R) at exon 20 and an alternative splicing of exon 4 in Tmem63b, which encodes a ubiquitously expressed osmosensitive cation channel. The channel isoforms lacking exon 4 occurred in ∼80% of Tmem63b mRNAs in the brain but were not detected in other tissues, suggesting a brain-specific splicing. We found that the Q/R editing was catalyzed by Adar2 (Adarb1) and required an editing site complementary sequence located in the proximal 5' end of intron 20. Moreover, the Q/R editing was almost exclusively identified in the splicing isoform lacking exon 4, indicating a coupling between the editing and the splicing. Elimination of the Q/R editing in brain-specific Adar2 knockout mice did not affect the splicing efficiency of exon 4. Furthermore, transfection with the splicing isoform containing exon 4 suppressed the Q/R editing in primary cultured cerebellar granule neurons. Thus, our study revealed a coupling between an RNA editing and a distant alternative splicing in the Tmem63b pre-mRNA, in which the splicing plays a dominant role. Finally, physiological analysis showed that the splicing and the editing coordinately regulate Ca2+ permeability and osmosensitivity of channel proteins, which may contribute to their functions in the brain.

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.

Tommaso Laurenzi
Dec 2, 2020; 0:jlr.RA120000843v1-jlr.RA120000843
Research Articles

Gerhard Liebisch
Dec 1, 2020; 61:1539-1555
Special Report

In SAS Retail Space Management, it should be possible to click on any location object, then Show Properties, and change the location fill color. This can be done on the gray-filled objects. However, w

This manuscript has been withdrawn by the Author.

Lecithin:cholesterol-acyl-transferase (LCAT) plays a major role in cholesterol metabolism as it is the only extracellular enzyme able to esterify cholesterol. LCAT activity is required for lipoprotein remodelling and, most specifically, for the growth and maturation of HDLs. In fact, genetic alterations affecting LCAT func- tionality may cause a severe reduction in plasma levels of HDL-cholesterol with important clinical consequences. Although several hypotheses were formulated, the exact molecular recognition mechanism between LCAT and HDLs is still unknown. We employed a combination of structural bioinformatics procedures to deepen the insights into the HDL-LCAT interplay that promotes LCAT activation and cholesterol esterification. We have generated a data-driven model of reconstituted HDL (rHDL) and studied the dynamics of an assembled rHDL::LCAT supramolecular complex, pinpointing the conformational changes originating from the interaction between LCAT and apolipoprotein A-I (apoA-I) that are necessary for LCAT activation. Specifically, we propose a mechanism in which the anchoring of LCAT lid to apoA-I helices allows the formation of a hydrophobic hood that expands LCAT active site and shields it from the solvent, allowing the enzyme to process large hydrophobic substrates.

For three decades, the LPL–specific monoclonal antibody 5D2 has been used to investigate LPL structure/function and intravascular lipolysis. 5D2 has been used to measure LPL levels, block the triglyceride hydrolase activity of LPL, and prevent the propensity of concentrated LPL preparations to form homodimers. Two early studies on the location of the 5D2 epitope reached conflicting conclusions, but the more convincing report suggested that 5D2 binds to a tryptophan (Trp)-rich loop in the carboxyl terminus of LPL. The same loop had been implicated in lipoprotein binding. Using surface plasmon resonance, we showed that 5D2 binds with high affinity to a synthetic LPL peptide containing the Trp-rich loop of human (but not mouse) LPL. We also showed, by both fluorescence and UV resonance Raman spectroscopy, that the Trp-rich loop binds lipids. Finally, we used X-ray crystallography to solve the structure of the Trp-rich peptide bound to a 5D2 Fab fragment. The Trp-rich peptide contains a short α-helix, with two Trps projecting into the antigen recognition site. A proline substitution in the α-helix, found in mouse LPL, is expected to interfere with several hydrogen bonds, explaining why 5D2 cannot bind to mouse LPL.

N-acylethanolamines (NAEs) are endogenous lipid-signaling molecules derived from fatty acids that regulate numerous biological functions, including in the brain. Interestingly, NAEs are elevated in the absence of fatty acid amide hydrolase (FAAH) and following CO₂-induced ischemia/hypercapnia, suggesting a neuroprotective response. Tetracosahexaenoic acid (THA) is a product and precursor to DHA; however, the NAE product, tetracosahexaenoylethanolamide (THEA), has never been reported. Presently, THEA was chemically synthesized as an authentic standard to confirm THEA presence in biological tissues. Whole brains were collected and analyzed for unesterified THA, total THA, and THEA in wild-type and FAAH-KO mice that were euthanized by either head-focused microwave fixation, CO₂ + microwave, or CO₂ only. PPAR activity by transient transfection assay and ex vivo neuronal output in medium spiny neurons (MSNs) of the nucleus accumbens by patch clamp electrophysiology were determined following THEA exposure. THEA in the wild-type mice was nearly doubled (P < 0.05) following ischemia/hypercapnia (CO₂ euthanization) and up to 12 times higher (P < 0.001) in the FAAH-KO compared with wild-type. THEA did not increase (P > 0.05) transcriptional activity of PPARs relative to control, but 100 nM of THEA increased (P < 0.001) neuronal output in MSNs of the nucleus accumbens. Here were identify a novel NAE, THEA, in the brain that is elevated upon ischemia/hypercapnia and by KO of the FAAH enzyme. While THEA did not activate PPAR, it augmented the excitability of MSNs in the nucleus accumbens. Overall, our results suggest that THEA is a novel NAE that is produced in the brain upon ischemia/hypercapnia and regulates neuronal excitation.

A comprehensive and standardized system to report lipid structures analyzed by MS is essential for the communication and storage of lipidomics data. Herein, an update on both the LIPID MAPS classification system and shorthand notation of lipid structures is presented for lipid categories Fatty Acyls (FA), Glycerolipids (GL), Glycerophospholipids (GP), Sphingolipids (SP), and Sterols (ST). With its major changes, i.e., annotation of ring double bond equivalents and number of oxygens, the updated shorthand notation facilitates reporting of newly delineated oxygenated lipid species as well. For standardized reporting in lipidomics, the hierarchical architecture of shorthand notation reflects the diverse structural resolution powers provided by mass spectrometric assays. Moreover, shorthand notation is expanded beyond mammalian phyla to lipids from plant and yeast phyla. Finally, annotation of atoms is included for the use of stable isotope-labeled compounds in metabolic labeling experiments or as internal standards. This update on lipid classification, nomenclature, and shorthand annotation for lipid mass spectra is considered a standard for lipid data presentation.

S-Acylation, a reversible post-translational lipid modification of proteins, controls the properties and function of various proteins, including ion channels. Large conductance Ca2+-activated potassium (BK) channels are S-acylated at two sites that impart distinct functional effects. Whereas the enzymes that attach lipid groups are known, the enzymes mediating lipid removal (i.e. deacylation) are largely unknown. Here, McClafferty et al. identify two enzymes, ABHD17a and ABHD17c, that excise BK channel lipid groups with remarkable precision. These findings lend insights into mechanisms that orchestrate the (de)acylation that fine-tunes ion channel function in physiology and disease.

S-Acylation, the reversible post-translational lipid modification of proteins, is an important mechanism to control the properties and function of ion channels and other polytopic transmembrane proteins. However, although increasing evidence reveals the role of diverse acyl protein transferases (zDHHC) in controlling ion channel S-acylation, the acyl protein thioesterases that control ion channel deacylation are very poorly defined. Here we show that ABHD17a (α/β-hydrolase domain-containing protein 17a) deacylates the stress-regulated exon domain of large conductance voltage- and calcium-activated potassium (BK) channels inhibiting channel activity independently of effects on channel surface expression. Importantly, ABHD17a deacylates BK channels in a site-specific manner because it has no effect on the S-acylated S0–S1 domain conserved in all BK channels that controls membrane trafficking and is deacylated by the acyl protein thioesterase Lypla1. Thus, distinct S-acylated domains in the same polytopic transmembrane protein can be regulated by different acyl protein thioesterases revealing mechanisms for generating both specificity and diversity for these important enzymes to control the properties and functions of ion channels.

Voltage-gated Cav1 and Cav2 Ca2+ channels are comprised of a pore-forming α1 subunit (Cav1.1-1.4, Cav2.1-2.3) and auxiliary β (β1-4) and α2δ (α2δ−1−4) subunits. The properties of these channels vary with distinct combinations of Cav subunits and alternative splicing of the encoding transcripts. Therefore, the impact of disease-causing mutations affecting these channels may depend on the identities of Cav subunits and splice variants. Here, we analyzed the effects of a congenital stationary night blindness type 2 (CSNB2)-causing mutation, I745T (IT), in Cav1.4 channels typical of those in human retina: Cav1.4 splice variants with or without exon 47 (Cav1.4+ex47 and Cav1.4Δex47, respectively), and the auxiliary subunits, β2X13 and α2δ-4. We find that IT caused both Cav1.4 splice variants to activate at significantly more negative voltages and with slower deactivation kinetics than the corresponding WT channels. These effects of the IT mutation, along with unexpected alterations in ion selectivity, were generally larger in channels lacking exon 47. The weaker ion selectivity caused by IT led to hyperpolarizing shifts in the reversal potential and large outward currents that were evident in channels containing the auxiliary subunits β2X13 and α2δ-4 but not in those with β2A and α2δ-1. We conclude that the IT mutation stabilizes channel opening and alters ion selectivity of Cav1.4 in a manner that is strengthened by exclusion of exon 47 and inclusion of β2X13 and α2δ-4. Our results reveal complex actions of IT in modifying the properties of Cav1.4 channels, which may influence the pathological consequences of this mutation in retinal photoreceptors.

The dominant role of CaV2 voltage-gated calcium channels for driving neurotransmitter release is broadly conserved. Given the overlapping functional properties of CaV2 and CaV1 channels, and less so CaV3 channels, it is unclear why there have not been major shifts toward dependence on other CaV channels for synaptic transmission. Here, we provide a structural and functional profile of the CaV2 channel cloned from the early-diverging animal Trichoplax adhaerens, which lacks a nervous system but possesses single gene homologues for CaV1–CaV3 channels. Remarkably, the highly divergent channel possesses similar features as human CaV2.1 and other CaV2 channels, including high voltage–activated currents that are larger in external Ba2+ than in Ca2+; voltage-dependent kinetics of activation, inactivation, and deactivation; and bimodal recovery from inactivation. Altogether, the functional profile of Trichoplax CaV2 suggests that the core features of presynaptic CaV2 channels were established early during animal evolution, after CaV1 and CaV2 channels emerged via proposed gene duplication from an ancestral CaV1/2 type channel. The Trichoplax channel was relatively insensitive to mammalian CaV2 channel blockers ω-agatoxin-IVA and ω-conotoxin-GVIA and to metal cation blockers Cd2+ and Ni2+. Also absent was the capacity for voltage-dependent G-protein inhibition by co-expressed Trichoplax Gβγ subunits, which nevertheless inhibited the human CaV2.1 channel, suggesting that this modulatory capacity evolved via changes in channel sequence/structure, and not G proteins. Last, the Trichoplax channel was immunolocalized in cells that express an endomorphin-like peptide implicated in cell signaling and locomotive behavior and other likely secretory cells, suggesting contributions to regulated exocytosis.

The divalent anion sodium symporter (DASS) family (SLC13) plays critical roles in metabolic homeostasis, influencing many processes, including fatty acid synthesis, insulin resistance, and adiposity. DASS transporters catalyze the Na+-driven concentrative uptake of Krebs cycle intermediates and sulfate into cells; disrupting their function can protect against age-related metabolic diseases and can extend lifespan. An inward-facing crystal structure and an outward-facing model of a bacterial DASS family member, VcINDY from Vibrio cholerae, predict an elevator-like transport mechanism involving a large rigid body movement of the substrate-binding site. How substrate binding influences the conformational state of VcINDY is currently unknown. Here, we probe the interaction between substrate binding and protein conformation by monitoring substrate-induced solvent accessibility changes of broadly distributed positions in VcINDY using a site-specific alkylation strategy. Our findings reveal that accessibility to all positions tested is modulated by the presence of substrates, with the majority becoming less accessible in the presence of saturating concentrations of both Na+ and succinate. We also observe separable effects of Na+ and succinate binding at several positions suggesting distinct effects of the two substrates. Furthermore, accessibility changes to a solely succinate-sensitive position suggests that substrate binding is a low-affinity, ordered process. Mapping these accessibility changes onto the structures of VcINDY suggests that Na+ binding drives the transporter into an as-yet-unidentified conformational state, involving rearrangement of the substrate-binding site–associated re-entrant hairpin loops. These findings provide insight into the mechanism of VcINDY, which is currently the only structurally characterized representative of the entire DASS family.

Synaptic transmission leading to release of neurotransmitters in the nervous system is a fast and highly dynamic process. Previously, protein interaction and phosphorylation have been thought to be the main regulators of synaptic transmission. Here we show that sialylation of N-linked glycosylation is a novel potential modulator of neurotransmitter release mechanisms by investigating depolarization-dependent changes of formerly sialylated N-linked glycopeptides. We suggest that negatively charged sialic acids can be modulated, similarly to phosphorylation, by the action of sialyltransferases and sialidases thereby changing local structure and function of membrane glycoproteins. We characterized site-specific alteration in sialylation on N-linked glycoproteins in isolated rat nerve terminals after brief depolarization using quantitative sialiomics. We identified 1965 formerly sialylated N-linked glycosites in synaptic proteins and found that the abundances of 430 glycosites changed after 5 s depolarization. We observed changes on essential synaptic proteins such as synaptic vesicle proteins, ion channels and transporters, neurotransmitter receptors and cell adhesion molecules. This study is to our knowledge the first to describe ultra-fast site-specific modulation of the sialiome after brief stimulation of a biological system.

Ventilator-associated pneumonia (VAP) is a common hospital-acquired infection, leading to high morbidity and mortality. Currently, bronchoalveolar lavage (BAL) is used in hospitals for VAP diagnosis and guiding treatment options. Although BAL collection procedures are invasive, alternatives such as endotracheal aspirates (ETA) may be of diagnostic value, however, their use has not been thoroughly explored. Longitudinal ETA and BAL were collected from 16 intubated patients up to 15 days, of which 11 developed VAP. We conducted a comprehensive LC–MS/MS based proteome and metabolome characterization of longitudinal ETA and BAL to detect host and pathogen responses to VAP infection. We discovered a diverse ETA proteome of the upper airways reflective of a rich and dynamic host-microbe interface. Prior to VAP diagnosis by microbial cultures from BAL, patient ETA presented characteristic signatures of reactive oxygen species and neutrophil degranulation, indicative of neutrophil mediated pathogen processing as a key host response to the VAP infection. Along with an increase in amino acids, this is suggestive of extracellular membrane degradation resulting from proteolytic activity of neutrophil proteases. The metaproteome approach successfully allowed simultaneous detection of pathogen peptides in patients' ETA, which may have potential use in diagnosis. Our findings suggest that ETA may facilitate early mechanistic insights into host-pathogen interactions associated with VAP infection and therefore provide its diagnosis and treatment.