Clostridium difficile is an anaerobic and spore-forming bacterium responsible for 15–25% of postantibiotic diarrhea and 95% of pseudomembranous colitis. Peptidoglycan is a crucial element of the bacterial cell wall that is exposed to the host, making it an important target for the innate immune system. The C. difficile peptidoglycan is largely N-deacetylated on its glucosamine (93% of muropeptides) through the activity of enzymes known as N-deacetylases, and this N-deacetylation modulates host–pathogen interactions, such as resistance to the bacteriolytic activity of lysozyme, virulence, and host innate immune responses. C. difficile genome analysis showed that 12 genes potentially encode N-deacetylases; however, which of these N-deacetylases are involved in peptidoglycan N-deacetylation remains unknown. Here, we report the enzymes responsible for peptidoglycan N-deacetylation and their respective regulation. Through peptidoglycan analysis of several mutants, we found that the N-deacetylases PdaV and PgdA act in synergy. Together they are responsible for the high level of peptidoglycan N-deacetylation in C. difficile and the consequent resistance to lysozyme. We also characterized a third enzyme, PgdB, as a glucosamine N-deacetylase. However, its impact on N-deacetylation and lysozyme resistance is limited, and its physiological role remains to be dissected. Finally, given the influence of peptidoglycan N-deacetylation on host defense against pathogens, we investigated the virulence and colonization ability of the mutants. Unlike what has been shown in other pathogenic bacteria, a lack of N-deacetylation in C. difficile is not linked to a decrease in virulence.

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

The actin cytoskeleton is of profound importance to cell shape, division, and intracellular force generation. Profilins bind to globular (G-)actin and regulate actin filament formation. Although profilins are well-established actin regulators, the distinct roles of the dominant profilin, profilin 1 (PFN1), versus the less abundant profilin 2 (PFN2) remain enigmatic. In this study, we use interaction proteomics to discover that PFN2 is an interaction partner of the actin N-terminal acetyltransferase NAA80, and further confirm this by analytical ultracentrifugation. Enzyme assays with NAA80 and different profilins demonstrate that PFN2 binding specifically increases the intrinsic catalytic activity of NAA80. NAA80 binds PFN2 through a proline-rich loop, deletion of which abrogates PFN2 binding. Small-angle X-ray scattering shows that NAA80, actin, and PFN2 form a ternary complex and that NAA80 has partly disordered regions in the N-terminus and the proline-rich loop, the latter of which is partly ordered upon PFN2 binding. Furthermore, binding of PFN2 to NAA80 via the proline-rich loop promotes binding between the globular domains of actin and NAA80, and thus acetylation of actin. However, the majority of cellular NAA80 is stably bound to PFN2 and not to actin, and we propose that this complex acetylates G-actin before it is incorporated into filaments. In conclusion, we reveal a functionally specific role of PFN2 as a stable interactor and regulator of the actin N-terminal acetyltransferase NAA80, and establish the modus operandi for NAA80-mediated actin N-terminal acetylation, a modification with a major impact on cytoskeletal dynamics.

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

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

Mammalian Asn-linked glycans are extensively processed as they transit the secretory pathway to generate diverse glycans on cell surface and secreted glycoproteins. Additional modification of the glycan core by α-1,6-fucose addition to the innermost GlcNAc residue (core fucosylation) is catalyzed by an α-1,6-fucosyltransferase (FUT8). The importance of core fucosylation can be seen in the complex pathological phenotypes of FUT8 null mice, which display defects in cellular signaling, development, and subsequent neonatal lethality. Elevated core fucosylation has also been identified in several human cancers. However, the structural basis for FUT8 substrate specificity remains unknown.Here, using various crystal structures of FUT8 in complex with a donor substrate analog, and with four distinct glycan acceptors, we identify the molecular basis for FUT8 specificity and activity. The ordering of three active site loops corresponds to an increased occupancy for bound GDP, suggesting an induced-fit folding of the donor-binding subsite. Structures of the various acceptor complexes were compared with kinetic data on FUT8 active site mutants and with specificity data from a library of glycan acceptors to reveal how binding site complementarity and steric hindrance can tune substrate affinity. The FUT8 structure was also compared with other known fucosyltransferases to identify conserved and divergent structural features for donor and acceptor recognition and catalysis. These data provide insights into the evolution of modular templates for donor and acceptor recognition among GT-B fold glycosyltransferases in the synthesis of diverse glycan structures in biological systems.

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

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

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.

Chorismate mutase (CM), an essential enzyme at the branch-point of the shikimate pathway, is required for the biosynthesis of phenylalanine and tyrosine in bacteria, archaea, plants, and fungi. MtCM, the CM from Mycobacterium tuberculosis, has less than 1% of the catalytic efficiency of a typical natural CM and requires complex formation with 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase for high activity. To explore the full potential of MtCM for catalyzing its native reaction, we applied diverse iterative cycles of mutagenesis and selection, thereby raising kcat/Km 270-fold to 5 × 105 m−1s−1, which is even higher than for the complex. Moreover, the evolutionarily optimized autonomous MtCM, which had 11 of its 90 amino acids exchanged, was stabilized compared with its progenitor, as indicated by a 9 °C increase in melting temperature. The 1.5 Å crystal structure of the top-evolved MtCM variant reveals the molecular underpinnings of this activity boost. Some acquired residues (e.g. Pro52 and Asp55) are conserved in naturally efficient CMs, but most of them lie beyond the active site. Our evolutionary trajectories reached a plateau at the level of the best natural enzymes, suggesting that we have exhausted the potential of MtCM. Taken together, these findings show that the scaffold of MtCM, which naturally evolved for mediocrity to enable inter-enzyme allosteric regulation of the shikimate pathway, is inherently capable of high activity.

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.

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

Aminopeptidase N (APN, CD13) is a transmembrane ectopeptidase involved in many crucial cellular functions. Besides its role as a peptidase, APN also mediates signal transduction and is involved in the activation of matrix metalloproteinases (MMPs). MMPs function in tissue remodeling within the extracellular space and are therefore involved in many human diseases, such as fibrosis, rheumatoid arthritis, tumor angiogenesis, and metastasis, as well as viral infections. However, the exact mechanism that leads to APN-driven MMP activation is unclear. It was previously shown that extracellular 14-3-3 adapter proteins bind to APN and thereby induce the transcription of MMPs. As a first step, we sought to identify potential 14-3-3–binding sites in the APN sequence. We constructed a set of phosphorylated peptides derived from APN to probe for interactions. We identified and characterized a canonical 14-3-3–binding site (site 1) within the flexible, structurally unresolved N-terminal APN region using direct binding fluorescence polarization assays and thermodynamic analysis. In addition, we identified a secondary, noncanonical binding site (site 2), which enhances the binding affinity in combination with site 1 by many orders of magnitude. Finally, we solved crystal structures of 14-3-3σ bound to mono- and bis-phosphorylated APN-derived peptides, which revealed atomic details of the binding mode of mono- and bivalent 14-3-3 interactions. Therefore, our findings shed some light on the first steps of APN-mediated MMP activation and open the field for further investigation of this important signaling pathway.

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

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

Peptidoglycan (PG) is an essential constituent of the bacterial cell wall. During cell division, the machinery responsible for PG synthesis localizes mid-cell, at the septum, under the control of a multiprotein complex called the divisome. In Escherichia coli, septal PG synthesis and cell constriction rely on the accumulation of FtsN at the division site. Interestingly, a short sequence of FtsN (Leu75–Gln93, known as EFtsN) was shown to be essential and sufficient for its functioning in vivo, but what exactly this sequence is doing remained unknown. Here, we show that EFtsN binds specifically to the major PG synthase PBP1b and is sufficient to stimulate its biosynthetic glycosyltransferase (GTase) activity. We also report the crystal structure of PBP1b in complex with EFtsN, which demonstrates that EFtsN binds at the junction between the GTase and UB2H domains of PBP1b. Interestingly, mutations to two residues (R141A/R397A) within the EFtsN-binding pocket reduced the activation of PBP1b by FtsN but not by the lipoprotein LpoB. This mutant was unable to rescue the ΔponB-ponAts strain, which lacks PBP1b and has a thermosensitive PBP1a, at nonpermissive temperature and induced a mild cell-chaining phenotype and cell lysis. Altogether, the results show that EFtsN interacts with PBP1b and that this interaction plays a role in the activation of its GTase activity by FtsN, which may contribute to the overall septal PG synthesis and regulation during cell division.

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

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

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

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

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

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

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

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

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

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

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

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

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

Black and Female
Tsitsi Dangarembga, Faber, £9.99

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

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

‘Writing While Black and Female’

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

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

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

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

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

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

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

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

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

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

The complexities of decolonization

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

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

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

Culture notes: Europe's broken promises to Africa The World Today mhiggins.drupal 1 August 2022

Europe’s ‘gas grab’ in Africa is just the latest abuse of its relationship with the continent, says Catherine Fieschi.

When Emmanuel Macron made one of his first visits to Africa as France’s recently elected young president in 2017, his speech at Ouagadougou University in Burkina Faso was designed to set the tone for a new relationship between his country and African countries. 

‘There no longer is a French policy for Africa,’ he said.

This was a signal away from ‘la Françafrique’, with its post-colonial accents and the propping up of regimes friendly to France, to something that was more strategic, equitable and transparent – more partnership and less tutelage. 

And Europe seemed to be following suit. In March 2020 the European Union and Africa decided that they would redefine their relationship. The European Commission unveiled its vision for a ‘comprehensive strategy with Africa’. The roadmap would give Africa significantly more say over the nature and extent of the relationship, more choice and more political agency.

But what, today, is left of these aspirations? Despite repeated statements, Europe seems to be saying one thing and doing another. 

Earlier this year, after the long-awaited 6th annual EU-African Union summit in Brussels, South African president Cyril Ramaphosa was frank when he summed up the gap between stated ambitions and the current relationship. The pandemic-weary Global South had reason to be wary. Ramaphosa laid out missed opportunities, disappointment and the low expectations that act as self-fulfilling prophecies. 

Europe’s changing focus in Africa 

From the apparent high point of the Ouagadougou speech, Macron has now turned to the Organization Internationale de la Francophonie (OIF) in Africa for geopolitical purposes. His primary aim is to combat the rise of Islamist militants and terrorism in the Sahel as well as to tackle the growing influence of China and Russia in the region. 

Russian inroads – via the security firm Wagner in Mali, for instance – have given France further cause to use the OIF to counter destabilization activities. Both the United Kingdom and France train African military in the Sahel, but now, with the end of France’s anti-insurgent Operation Barkhane in Mali, the subsequent withdrawal of French troops and the increasingly established presence of the Wagner group, the security situation in the region is expected to deteriorate dramatically and become increasingly impermeable to European interests and forces.

As for development aid, Britain’s Integrated Review of Security, Defence, Development and Foreign Policy makes no bones about the fact that Asia is now a priority over Africa.

The relationship between Africa and Britain is being transformed as a result, most obviously through the cuts in development aid, with African aid cut by 66 per cent in 2021. But the nature of the relationship, which has become both more conditional and more transactional, has also changed. 

The UK is emphasizing human rights and ‘free societies’, but also pushing for free market principles rather than the kind of state involvement that some African countries often prefer as a road to accelerated and more autonomous development. 

The future of energy exports and COP27

The issue of energy exports points to what will most likely trigger the greatest disappointment in the next few years – climate and climate finance. 

Green energy deals, like the $8.5 billion COP26 package from the EU, United States and UK to South Africa, look far more problematic now in the light of Europe’s African gas-grab. Indeed, Europe is importing as much African gas as it can after the invasion of Ukraine by Russia reduced supplies. Yet African countries are still being told to curb their own use of ‘dirty’ energy. 

As an illustration, Nigeria holds 3 per cent of the world’s gas reserves, but has barely tapped them, while 40 per cent of its output is exported to Europe. In April, Italy closed deals to buy gas from Angola and the Republic of Congo, while Germany did the same with Senegal.
 

At COP15 in Copenhagen in 2009, developed countries pledged an annual $100 billion in climate finance to developing countries for both adaptation and mitigation. But pledges have never really materialized. The aid agency Oxfam estimates that only about a third of the money has been delivered. Climate finance was again the main focus of COP26 – and dismissed by Greta Thunberg as more ‘blah, blah, blah’.

This series of repeated resets, pledges and disappointments tells a story – indeed, several stories. First and foremost, it is one of arrogance and betrayal. That much is obvious. But it is also a story about stories – about how the narratives elaborated by various European countries and leaders never amount to more than a sum of transactions. 

Climate change places Europe, and other rich nations, at a crossroads in its relationship with Africa: the former holds the wealth, but also some of the keys and threats to the transition. COP27, to be held in Egypt in November, will be the next chapter in the story. 

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

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

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

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

Growing tech hubs

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

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

Barriers to scale

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

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

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

Help or hindrance from the top?

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

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

Towards democracy in Sudan: Reflections on the transitional period 20 September 2022 — 2:00PM TO 4:00PM Anonymous (not verified) 31 August 2022 Online

In this webinar, panellists discuss the key outcomes of the evaluation workshop and reflect on how the experience of the transition to date should inform the realization of Sudan’s democratic aspirations going forward.

The military coup on 25 October 2021 halted Sudan’s transition to democracy and prospects for sustainable peace. Since then, members of the former regime have regained political influence, with many reinstated to senior positions.

The coup has provoked a strong reaction from the country’s pro-democracy movement and youth-led resistance committees who have led continuous peaceful protests demanding civilian democratic transition, despite a brutal crackdown by state security forces.

Those supportive of the coup have blamed the Forces of Freedom and Change (FFC), a wide coalition of pro-democracy political and civilian groups, for the mistakes of the transitional government.

However, the country’s political, security and economic situation has sharply deteriorated since the military’s action, and the progress achieved by the transitional government has been reversed, leading to an accelerating economic crisis, increased food insecurity and political instability.

The FFC, which played a key role in appointing the transitional government, has acknowledged its errors. In July 2022, it held a workshop in Khartoum, which was broadcast on social media, to evaluate its performance and identify lessons learned, in discussion with civil society actors and activists.

In this webinar, leading pro-democracy movement figures and independent experts discuss the key outcomes of the evaluation workshop and reflect on how the experience of the transition to date should inform the realization of Sudan’s democratic aspirations going forward.

This event is part of a Chatham House Africa programme project on supporting Sudan’s civilian-led democratic transition.

Independent Thinking: War in Tigray, Zaporizhzhia under fire Audio NCapeling 24 November 2022

Episode six of our new weekly podcast examines the ongoing conflict in Ethiopia and the international response to further attacks on Europe’s largest nuclear plant in Ukraine.

In Tigray, the world’s largest armed conflict rages between Ethiopian federal government troops and the Tigray Defence Forces. With estimates placing those killed in the fighting at 600,000, how did Ethiopia, one of Africa’s great success stories, descend into civil war, and what hopes are there for recent peace initiatives?

Meanwhile in Ukraine, all eyes are on Zaporizhzhia, as Europe’s largest nuclear plant continues to be occupied by Russian forces. With fresh reports of explosions near the reactors, how is the international community responding?

Finally, what role does Turkey, a middle power country with great power ambitions, play in both conflicts?

Joining guest host John Kampfner on the podcast this week are Dr Patricia Lewis, director of the International Security programme at Chatham House, Ahmed Soliman, senior research fellow with our Africa programme, and Galip Dalay, associate fellow with our Middle East and North Africa programme.

Independent Thinking: China in Africa, conflicts in 2023 Audio NCapeling 13 January 2023

Episode ten discusses Africa and the complex role China plays on the continent, and how the world should be responding to the major conflicts of 2023.

The first episode of 2023 examines Africa and the complex role China plays on the continent as a new Chatham House report highlights 22 African countries suffering from debt distress with Beijing a key creditor to many of them.

China’s new foreign minister Qin Gang is also touring several African states this week and next, with visits planned to Ethiopia, Angola, Gabon, and the headquarters of the African Union (AU).

This week Chatham House also hosted Dr Comfort Ero, president of the International Crisis Group, to discuss ten conflicts to watch in 2023. The panel examines some of the key conflicts mentioned and how the world is responding to them.

Joining Bronwen Maddox on the podcast this week from Chatham House are Dr Alex Vines, director of the Africa programme, Creon Butler, director of the Global Economy and Finance programme, Dr Yu Jie, senior fellow on the Asia-Pacific programme, and Armida van Rij, research fellow with the International Security programme.

About Independent Thinking

A weekly podcast hosted by Chatham House director Bronwen Maddox, in conversation with leading policymakers, journalists, and Chatham House experts providing insight on the latest international issues.

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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PREAMBLE

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional nonprofit medical association that facilitates communication worldwide between individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. The EANM was founded in 1985. SNMMI and EANM members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine.

The SNMMI and EANM will periodically define new guidelines for nuclear medicine practice to help advance the science of nuclear medicine and to improve the quality of service to patients throughout the world. Existing practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated.

Each practice guideline, representing a policy statement by the SNMMI/EANM, has undergone a thorough consensus process in which it has been subjected to extensive review. The SNMMI and EANM recognize that the safe and effective use of diagnostic nuclear medicine imaging requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guideline by those entities not providing these services is not authorized.

These guidelines are an educational tool designed to assist practitioners in providing appropriate care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, both the SNMMI and the EANM caution against the use of these guidelines in litigation in which the clinical decisions of a practitioner are called into question.

The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by the physician or medical physicist in light of all the circumstances presented. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the guidelines.

The practice of medicine includes both the art and the science of the prevention, diagnosis, alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment.

Therefore, it should be recognized that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.

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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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