LRRC8 Proteins Form Volume-Regulated Anion Channels that Sense Ionic Strength.

The volume-regulated anion channel (VRAC) is activated when a cell swells, and it plays a central role in maintaining cell volume in response to osmotic challenges. SWELL1 (LRRC8A) was recently identified as an essential component of VRAC. However, the identity of the pore-forming subunits of VRAC and how the channel is gated by cell swelling are unknown. Here, we show that SWELL1 and up to four other LRRC8 subunits assemble into heterogeneous complexes of ∼800 kDa. When reconstituted into bilayers, LRRC8 complexes are sufficient to form anion channels activated by osmolality gradients. In bilayers, as well as in cells, the single-channel conductance of the complexes depends on the LRRC8 composition. Finally, low ionic strength (Γ) in the absence of an osmotic gradient activates the complexes in bilayers. These data demonstrate that LRRC8 proteins together constitute the VRAC pore and that hypotonic stress can activate VRAC through a decrease in cytoplasmic Γ.

Assessment of fluid responsiveness in children using respiratory variations in descending aortic flow.

BACKGROUND: The primary aim of the current study was to investigate the ability of respiratory variations in descending aortic flow, measured with two-dimensional echo at the suprasternal notch (ΔVpeak dAo), to predict fluid responsiveness in anesthetized mechanically ventilated children. In addition, variations in peak descending aortic flow measured with apical transthoracic echo (ΔVpeak LVOT) were examined for the same properties. METHODS: Twenty-seven patients under general anesthesia were investigated in this prospective observational study. Cardiac output, ΔVpeak dAo, and ΔVpeak LVOT were measured at stable conditions after anesthesia induction. The measurements were repeated after a 10 mL kg-1 fluid bolus. Patients were classified as responders if stroke volume index increased by >15% after fluid bolus. The ability of each parameter to predict fluid responsiveness was assessed using receiver operating characteristic curves. RESULTS: Twenty-seven patients were analyzed, mean age and weight 43 months and 16 kg, respectively. Twelve responders and 15 non-responders were identified. ΔVpeak dAo was significantly higher in the responder group (14%, 95% confidence interval [CI]: 12%-17%) compared to the non-responder group (11%, 95% CI: 9%-13%) (p = .04) at baseline. Area under the ROC curve for ΔVpeak dAo and ΔVpeak LVOT was 0.73 (95% CI: 0.52-0.89, p = .02) and 0.56 (0.34-0.78, p = .3), respectively. A baseline level of ΔVpeak dAo of >14% predicted fluid responsiveness with a sensitivity of 58% (95% CI: 28%-85%) and specificity of 73% (95% CI: 45%-92%). CONCLUSION: In mechanically ventilated children, ΔVpeak dAo identified fluid responders with moderate diagnostic power in the current study. ΔVpeak LVOT failed to predict fluid responders in the current study.

A Randomized, Double-Blind, Placebo-Controlled Phase 2a Study of Tildrakizumab Efficacy and Safety in Patients With Active Ankylosing Spondylitis.

OBJECTIVE: Tildrakizumab is an anti-interleukin-23p19 monoclonal antibody approved to treat moderate to severe plaque psoriasis. This study evaluated the efficacy and safety of tildrakizumab in patients with ankylosing spondylitis (AS). METHODS: In this randomized, double-blind, parallel-group, multinational trial ( clinicaltrials.gov NCT02980705), patients with active AS, according to modified New York criteria and Bath Ankylosing Spondylitis Disease Activity Index Score ≥4, were randomized 1:1 to tildrakizumab 200 mg or placebo every 4 weeks until week 24. Thereafter, all patients received tildrakizumab 200 mg every 4 weeks until week 48. The primary outcome was proportion of patients achieving 20% improvement from baseline by Assessment in SpondyloArthritis International Society criteria (ASAS20) at week 24. This outcome was analyzed in subgroups defined by prior treatment experience, weight, age, and sex using the full analysis set. Safety was assessed through treatment-emergent adverse events. RESULTS: From December 5, 2017-September 3, 2019, 101 patients (76.2% male, 97% White) enrolled and were randomized to treatment. At week 24, the ASAS20 response rate was 74.0% in patients receiving tildrakizumab 200 mg (n = 50) versus 80.4% in placebo-treated patients (n = 51; treatment difference, -6.31%; 95% confidence interval, -22.34 to 9.71; p = 0.44). No difference in treatment effect by subgroups was observed. Tildrakizumab treatment was generally well tolerated, with no unexpected safety findings. The study was terminated after the week 24 interim analysis due to lack of efficacy. CONCLUSIONS: Tildrakizumab treatment was generally well tolerated but did not improve ASAS20 response rate versus placebo in patients with AS.

Resident-attending discrepancy rates for two consecutive versus nonconsecutive weeks of overnight shifts.

PURPOSE: Recent Accreditation Council for Graduate Medical Education policy changes no longer limit the number of consecutive night shifts allowed for trainees. Few studies have examined radiology resident overnight performance over time. This study aimed to compare significant resident-attending discrepancy rates for residents working 2 nonconsecutive versus consecutive weeks of overnight shifts. The authors hypothesized significantly increased week-two discrepancies in the consecutive group. METHODS: For 2020, a retrospective analysis of significant overnight resident-attending discrepancy rates over a 24-week period using database searches was performed for residents self-selecting 2 nonconsecutive versus consecutive weeks. The nonconsecutive group typically had a 7-day mix of days off and day shifts between their night shift weeks. Paired and unpaired t tests were performed with p < 0.05 considered significant. RESULTS: For the 24 sets of 2 weeks covered by two residents at a time, eight were nonconsecutive and 16 were consecutive. The nonconsecutive group had 75.0% R4 coverage compared to 37.5% for the consecutive group. There were no significant study volume differences between the groups. A total of 27,906 studies (35.3% cross-sectional [CT and MR], 54.9% radiograph plus fluoroscopy, 9.8% US) were performed with 223 discrepancies (0.80%). Overall discrepancies for the nonconsecutive versus consecutive groups were 39/4505 (0.87%) versus 59/9462 (0.62%; p = 0.32) for week one and 46/4732 (1.0%) versus 79/9207 (0.86%; p = 0.60) for week two with no significant differences between the groups by modality. CONCLUSION: Residents self-selecting 2 consecutive weeks of overnight shifts do not have increased resident-attending discrepancy rates compared to 2 nonconsecutive weeks.

Pulmonary injury and oxidative stress in rats induced by inhaled sulfur mustard is ameliorated by anti-tumor necrosis factor-α antibody.

Sulfur mustard (SM) is a bifunctional alkylating agent that causes severe injury to the respiratory tract. This is accompanied by an accumulation of macrophages in the lung and the release of the proinflammatory cytokine, tumor necrosis factor (TNF)α. In these studies, we analyzed the effects of blocking TNFα on lung injury, inflammation and oxidative stress induced by inhaled SM. Rats were treated with SM vapor (0.4 mg/kg) or air control by intratracheal inhalation. This was followed 15-30 min later by anti-TNFα antibody (15mg/kg, i.v.) or PBS control. Animals were euthanized 3 days later. Anti-TNFα antibody was found to blunt SM-induced peribronchial edema, perivascular inflammation and alveolar plasma protein and inflammatory cell accumulation in the lung; this was associated with reduced expression of PCNA in histologic sections and decreases in BAL levels of fibrinogen. SM-induced increases in inflammatory proteins including soluble receptor for glycation end products, its ligand, high mobility group box-1, and matrix metalloproteinase-9 were also reduced by anti-TNFα antibody administration, along with increases in numbers of lung macrophages expressing TNFα, cyclooxygenase-2 and inducible nitric oxide synthase. This was correlated with reduced oxidative stress as measured by expression of heme oxygenase-1 and Ym-1. Together, these data suggest that inhibiting TNFα may represent an efficacious approach to mitigating acute lung injury, inflammatory macrophage activation, and oxidative stress induced by inhaled sulfur mustard.

Appraising clinical applicability of studies: mapping and synthesis of current frameworks, and proposal of the FrACAS framework and VICORT checklist.

BACKGROUND: Not all research findings are translated to clinical practice. Reasons for lack of applicability are varied, and multiple frameworks and criteria exist to appraise the general applicability of epidemiological and clinical research. In this two-part study, we identify, map, and synthesize frameworks and criteria; we develop a framework to assist clinicians to appraise applicability specifically from a clinical perspective. METHODS: We conducted a literature search in PubMed and Embase to identify frameworks appraising applicability of study results. Conceptual thematic analysis was used to synthesize frameworks and criteria. We carried out a framework development process integrating contemporary debates in epidemiology, findings from the literature search and synthesis, iterative pilot-testing, and brainstorming and consensus discussions to propose a concise framework to appraise clinical applicability. RESULTS: Of the 4622 references retrieved, we identified 26 unique frameworks featuring 21 criteria. Frameworks and criteria varied by scope and level of aggregation of the evidence appraised, target user, and specific area of applicability (internal validity, clinical applicability, external validity, and system applicability). Our proposed Framework Appraising the Clinical Applicability of Studies (FrACAS) classifies studies in three domains (research, practice informing, and practice changing) by examining six criteria sequentially: Validity, Indication-informativeness, Clinical relevance, Originality, Risk-benefit comprehensiveness, and Transposability (VICORT checklist). CONCLUSIONS: Existing frameworks to applicability vary by scope, target user, and area of applicability. We introduce FrACAS to specifically assess applicability from a clinical perspective. Our framework can be used as a tool for the design, appraisal, and interpretation of epidemiological and clinical studies.

Methyl isocyanate inhalation induces tissue factor-dependent activation of coagulation in rats.

Methyl isocyanate (MIC) is a highly toxic industrial chemical causing acute lethality after inhalation. The objective of this study was to determine whether alterations in hemostasis also occur in the immediate hours after exposure. Male rats were exposed to MIC (125-500 ppm) by nose-only vapor inhalation for 30 min. Arterial O2 saturation was monitored prior to exposure, and hourly thereafter. Rats were euthanized at 1, 2, 4, and 8 hr and plasma analyzed for recalcification clotting time, tissue factor (TF) activity, and protein levels. Hypoxemia, as assessed by pulse oximetry, was an early feature of MIC inhalation. In contrast to sham or low (125 ppm) concentrations, 250 and 500 ppm MIC caused significant declines in blood oxygen saturation (% SpO2) at 1 hr, which remained at deficit during the postexposure period. Commensurate with hypoxemia, plasma clotting time was significantly accelerated 1 hr after MIC inhalation (sham treatment: 955 ± 62.8 s; 125 ppm MIC: 790 ± 62 s; 250 ppm: 676 ± 28.0 s; 500 ppm: 581 ± 175 s). This procoagulant effect was transient, with no difference observed between sham and all MIC groups by 8 hr. Similarly, elevated TF activity and protein were detected in plasma 1 hr after MIC inhalation, each of which showed a progressive decline back to control levels at later timepoints. This study demonstrates that MIC inhalation resulted in hypoxemia and transient hypercoagulability of blood. Accelerated clotting occurred rapidly and was likely due to intravascular TF, which initiates the extrinsic coagulation pathway.

Optimization of an Enzymatic Antibody-Drug Conjugation Approach Based on Coenzyme A Analogs.

Phosphopantetheine transferases (PPTases) can be used to efficiently prepare site-specific antibody-drug conjugates (ADCs) by enzymatically coupling coenzyme A (CoA)-linker payloads to 11-12 amino acid peptide substrates inserted into antibodies. Here, a two-step strategy is established wherein in a first step, CoA analogs with various bioorthogonal reactivities are enzymatically installed on the antibody for chemical conjugation with a cytotoxic payload in a second step. Because of the high structural similarity of these CoA analogs to the natural PPTase substrate CoA-SH, the first step proceeds very efficiently and enables the use of peptide tags as short as 6 amino acids compared to the 11-12 amino acids required for efficient one-step coupling of the payload molecule. Furthermore, two-step conjugation provides access to diverse linker chemistries and spacers of varying lengths. The potency of the ADCs was largely independent of linker architecture. In mice, proteolytic cleavage was observed for some C-terminally linked auristatin payloads. The in vivo stability of these ADCs was significantly improved by reduction of the linker length. In addition, linker stability was found to be modulated by attachment site, and this, together with linker length, provides an opportunity for maximizing ADC stability without sacrificing potency.

Positional identification of RT1-B (HLA-DQ) as susceptibility locus for autoimmune arthritis.

Rheumatoid arthritis (RA) is associated with amino acid variants in multiple MHC molecules. The association to MHC class II (MHC-II) has been studied in several animal models of RA. In most cases these models depend on T cells restricted to a single immunodominant peptide of the immunizing Ag, which does not resemble the autoreactive T cells in RA. An exception is pristane-induced arthritis (PIA) in the rat where polyclonal T cells induce chronic arthritis after being primed against endogenous Ags. In this study, we used a mixed genetic and functional approach to show that RT1-Ba and RT1-Bb (RT1-B locus), the rat orthologs of HLA-DQA and HLA-DQB, determine the onset and severity of PIA. We isolated a 0.2-Mb interval within the MHC-II locus of three MHC-congenic strains, of which two were protected from severe PIA. Comparison of sequence and expression variation, as well as in vivo blocking of RT1-B and RT1-D (HLA-DR), showed that arthritis in these strains is regulated by coding polymorphisms in the RT1-B genes. Motif prediction based on MHC-II eluted peptides and structural homology modeling suggested that variants in the RT1-B P1 pocket, which likely affect the editing capacity by RT1-DM, are important for the development of PIA.

Oxysterols direct immune cell migration via EBI2.

Epstein-Barr virus-induced gene 2 (EBI2, also known as GPR183) is a G-protein-coupled receptor that is required for humoral immune responses; polymorphisms in the receptor have been associated with inflammatory autoimmune diseases. The natural ligand for EBI2 has been unknown. Here we describe the identification of 7α,25-dihydroxycholesterol (also called 7α,25-OHC or 5-cholesten-3ß,7α,25-triol) as a potent and selective agonist of EBI2. Functional activation of human EBI2 by 7α,25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high-affinity radioligand binding. Furthermore, we find that 7α,25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A critical enzyme required for the generation of 7α,25-OHC is cholesterol 25-hydroxylase (CH25H). Similar to EBI2 receptor knockout mice, mice deficient in CH25H fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that CH25H generates EBI2 biological activity in vivo and indicates that the EBI2-oxysterol signalling pathway has an important role in the adaptive immune response.

Timing of Physical Therapy Referral in Adolescent Athletes With Acute Spondylolysis: A Retrospective Chart Review.

OBJECTIVES: The purposes of this study were (1) to determine whether the duration of rest before referral to physical therapy (PT) affects the time to make a full return to activity for patients with an acute spondylolysis, (2) to assess the safety of an early referral to PT in patients with an acute spondylolysis. STUDY DESIGN: Retrospective chart review. SETTING: Hospital-based sports medicine clinic. PATIENTS: The medical charts of 196 adolescent athletes (mean age = 14.3 ± 1.8 years) with an acute spondylolytic injury met the inclusion criteria and were reviewed. INDEPENDENT VARIABLE: Patients were subgrouped based on physician referral to PT. PATTERNS: An aggressive referral group (<10 weeks) and a conservative referral group (>10 weeks). MAIN OUTCOME MEASURES: Duration of rest before clearance to a full return to activity and the frequency of adverse reactions during the course of treatment. Safety was assessed by calculating the risk of experiencing an adverse reaction in each group. RESULTS: Median days to a full return to activity for aggressive referral group (115.5 days, interquartile range 98-150 days) and conservative referral group (140.0 days, interquartile range 114.5-168 days) were significantly different (P = 0.002). Eleven patients had adverse reactions during the course of treatment. The risk of adverse reaction was not statistically significant between groups (P = 0.509). CONCLUSIONS: Patients with acute spondylolysis in the aggressive referral group were able to make a full return activity almost 25 days sooner. No differences in the risk of adverse reactions were noted between aggressive and conservative referral groups.

Clinical progression of ocular injury following arsenical vesicant lewisite exposure.

Ocular injury by lewisite (LEW), a potential chemical warfare and terrorist agent, results in edema of eyelids, inflammation, massive corneal necrosis and blindness. To enable screening of effective therapeutics to treat ocular injury from LEW, useful clinically-relevant endpoints are essential. Hence, we designed an efficient exposure system capable of exposing up to six New-Zealand white rabbits at one time, and assessed LEW vapor-induced progression of clinical ocular lesions mainly in the cornea. The right eye of each rabbit was exposed to LEW (0.2 mg/L) vapor for 2.5, 5.0, 7.5 and 10.0 min and clinical progression of injury was observed for 28 days post-exposure (dose-response study), or exposed to same LEW dose for 2.5 and 7.5 min and clinical progression of injury was observed for up to 56 days post-exposure (time-response study); left eye served as an unexposed control. Increasing LEW exposure caused corneal opacity within 6 h post-exposure, which increased up to 3 days, slightly reduced thereafter till 3 weeks, and again increased thereafter. LEW-induced corneal ulceration peaked at 1 day post-exposure and its increase thereafter was observed in phases. LEW exposure induced neovascularization starting at 7 days which peaked at 22-35 days post-exposure, and remained persistent thereafter. In addition, LEW exposure caused corneal thickness, iris redness, and redness and swelling of the conjunctiva. Together, these findings provide clinical sequelae of ocular injury following LEW exposure and for the first time establish clinically-relevant quantitative endpoints, to enable the further identification of histopathological and molecular events involved in LEW-induced ocular injury.

Citrullination of collagen II affects integrin-mediated cell adhesion in a receptor-specific manner.

Citrullinated collagen II (CII) is a well-known autoantigen in rheumatoid arthritis (RA). However, the direct effects of CII citrullination on cell behavior have not been described. To study whether citrullination of CII could affect cellular functions, we measured the adhesion of 3 different cell types (human Saos2 osteosarcoma cells, human synovial fibroblasts, and rat mesenchymal stem cells) with impedance-based technology. The binding of different collagen receptor integrins to citrullinated collagen was studied by CHO cell lines, each overexpressing 1 of the 4 human collagen receptors on the cell surface, and with solid-phase binding assays, using the recombinant human integrin α1I, α2I, α10I, and α11I domains. Collagen citrullination decreased the adhesion of synovial fibroblasts ∼50% (P<0.05) and mesenchymal stem cells ∼40% (P<0.05) by specifically decreasing the binding of integrins α10ß1 and α11ß1 to arginine-containing motifs, such as GFOGER. In contrast, citrullination had only a minor effect on the function of α1ß1 and α2ß1 integrins, which have been reported to play a critical role in regulating leukocyte function. Molecular modeling was used to explain the detected functional differences at the structural level. Given that the integrins regulate cell metabolism, proliferation, and migration, we suggest that collagen citrullination modifies the pathogenesis of RA. Here, CII citrullination was shown to decrease the survival of mesenchymal stem cells.

A sulfated carbohydrate epitope inhibits axon regeneration after injury.

Chondroitin sulfate proteoglycans (CSPGs) represent a major barrier to regenerating axons in the central nervous system (CNS), but the structural diversity of their polysaccharides has hampered efforts to dissect the structure-activity relationships underlying their physiological activity. By taking advantage of our ability to chemically synthesize specific oligosaccharides, we demonstrate that a sugar epitope on CSPGs, chondroitin sulfate-E (CS-E), potently inhibits axon growth. Removal of the CS-E motif significantly attenuates the inhibitory activity of CSPGs on axon growth. Furthermore, CS-E functions as a protein recognition element to engage receptors including the transmembrane protein tyrosine phosphatase PTPσ, thereby triggering downstream pathways that inhibit axon growth. Finally, masking the CS-E motif using a CS-E-specific antibody reversed the inhibitory activity of CSPGs and stimulated axon regeneration in vivo. These results demonstrate that a specific sugar epitope within chondroitin sulfate polysaccharides can direct important physiological processes and provide new therapeutic strategies to regenerate axons after CNS injury.

Enhanced proteolytic clearance of plasma Aß by peripherally administered neprilysin does not result in reduced levels of brain Aß in mice.

Accumulation of ß-amyloid (Aß) in the brain is believed to contribute to the pathology of Alzheimer's Disease (AD). Aß levels are controlled by the production of Aß from amyloid precursor protein, degradation by proteases, and peripheral clearance. In this study we sought to determine whether enhancing clearance of plasma Aß with a peripherally administered Aß-degrading protease would reduce brain Aß levels through a peripheral sink. Neprilysin (NEP) is a zinc-dependent metalloprotease that is one of the key Aß-degrading enzymes in the brain. We developed a NEP fusion protein with in vitro degradation of Aß and a 10 day plasma half-life in mouse. Intravenous administration of NEP to wild-type and APP23 transgenic mice resulted in dose-dependent clearance of plasma Aß. However, this did not correspond to reduced levels of soluble brain Aß with treatment up to 5 weeks in WT mice or formic acid-extractable brain Aß with 3 month treatment in aged APP23. In contrast, intracranial injection of NEP resulted in an acute decrease in soluble brain Aß. We found no change in amyloid precursor protein gene expression in mice treated with intravenous NEP, suggesting that the lack of effects in the brain following this route of administration was not caused by compensatory upregulation of Aß production. Taken together, these results suggest a lack of a robust peripheral Aß efflux sink through which brain amyloid burdens can be therapeutically reduced.

Photoactivatable glycopolymers for the proteome-wide identification of fucose-α(1-2)-galactose binding proteins.

Although fucose-α(1-2)-galactose (Fucα(1-2)Gal)-containing glycans have been implicated in cognitive processes such as learning and memory, their precise molecular mechanisms are poorly understood. Here we employed the use of multivalent glycopolymers to enable the first proteome-wide identification of weak affinity, low abundance Fucα(1-2)Gal glycan-binding proteins (GBPs). Biotin-terminated glycopolymers containing photoactivatable cross-linking groups were designed to capture and enrich GBPs from rat brain lysates. Candidate proteins were tested for their ability to bind Fucα(1-2)Gal, and the functional significance of the interaction was investigated for the synaptic vesicle protein SV2a using a knockout mouse system. The results suggest a role for SV2a-Fucα(1-2)Gal interactions in SV2a trafficking and synaptic vesicle recycling. More broadly, our studies outline a general chemical approach for the systems-level discovery of novel GBPs.

Dynamic O-GlcNAc modification regulates CREB-mediated gene expression and memory formation.

The transcription factor cyclic AMP-response element binding protein (CREB) is a key regulator of many neuronal processes, including brain development, circadian rhythm and long-term memory. Studies of CREB have focused on its phosphorylation, although the diversity of CREB functions in the brain suggests additional forms of regulation. Here we expand on a chemoenzymatic strategy for quantifying glycosylation stoichiometries to characterize the functional roles of CREB glycosylation in neurons. We show that CREB is dynamically modified with an O-linked ß-N-acetyl-D-glucosamine sugar in response to neuronal activity and that glycosylation represses CREB-dependent transcription by impairing its association with CREB-regulated transcription coactivator (CRTC; also known as transducer of regulated CREB activity). Blocking glycosylation of CREB alters cellular function and behavioral plasticity, enhancing both axonal and dendritic growth and long-term memory consolidation. Our findings demonstrate a new role for O-glycosylation in memory formation and provide a mechanistic understanding of how glycosylation contributes to critical neuronal functions. Moreover, we identify a previously unknown mechanism for the regulation of activity-dependent gene expression, neural development and memory.

A Manifesto for transformative action on HIV among Black communities in Canada.

Black communities bear a hugely disproportionate share of Canada's HIV epidemic. Black persons annually represent up to one quarter of new diagnoses, while in contrast, diagnoses have been falling among white Canadians for the past two decades. There has been a notable lack of urgency and serious debate about why the trend persists and what to do about it. For too long, public institutions have reproduced hegemonic white supremacy and profoundly mischaracterized Black life. Consequently, Black communities suffer policies and programs that buttress systemic anti-Black racism, socio-economically disenfranchise Black communities, and in the process marginalize knowledgeable, experienced, and creative Black stakeholders. The Interim Committee on HIV among Black Canadian Communities (ICHBCC) is a group of Black researchers, service providers, and community advocates who came together in early 2022 to interject urgency to the HIV crisis facing Black communities. Specifically, the ICHBCC advocates for self-determined community leadership of research, policies, and programs, backed by access to appropriate resources, to change the trajectory of HIV among Black Canadian communities. In this article, we introduce the wider community to the Black HIV Manifesto that we developed in 2022.

RéSUMé: Les communautés noires constituent une part très disproportionnée de l'épidémie de VIH du Canada. Les personnes noires représentent annuellement jusqu'au quart des nouveaux diagnostics, tandis que les diagnostics diminuent chez les Canadiennes et les Canadiens de race blanche depuis 20 ans. Il y a une absence notable d'urgence et de débat sérieux sur la raison de la persistance de ces tendances et sur ce qu'il faudrait y faire. Pendant trop longtemps, les institutions publiques ont reproduit l'hégémonie de la suprématie blanche et extrêmement mal caractérisé les vies noires. Par conséquent, les communautés noires souffrent de politiques et de programmes qui soutiennent le racisme anti-Noirs systémique, privent les communautés noires de leurs droits socioéconomiques et marginalisent ainsi les connaissances, l'expérience et la créativité des parties prenantes noires. Le comité intérimaire sur le VIH dans les communautés noires du Canada (ICHBCC) est un groupe de chercheurs et de chercheuses, de prestataires de services et de porte-parole communautaires de race noire qui se sont regroupés au début de 2022 pour mettre l'accent sur le caractère urgent de la crise du VIH dans les communautés noires. Plus précisément, l'ICHBCC plaide en faveur d'un leadership communautaire autodéterminé de la recherche, des politiques et des programmes, appuyé par un accès aux ressources nécessaires, pour changer la trajectoire du VIH dans les communautés noires du Canada. Dans cet article, nous présentons à l'ensemble de la communauté le « manifeste noir sur le VIH ¼ que nous avons élaboré en 2022.

PMCA2 via PSD-95 controls calcium signaling by α7-containing nicotinic acetylcholine receptors on aspiny interneurons.

Local control of calcium concentration within neurons is critical for signaling and regulation of synaptic communication in neural circuits. How local control can be achieved in the absence of physical compartmentalization is poorly understood. Challenging examples are provided by nicotinic acetylcholine receptors that contain α7 nicotinic receptor subunits (α7-nAChRs). These receptors are highly permeable to calcium and are concentrated on aspiny dendrites of interneurons, which lack obvious physical compartments for constraining calcium diffusion. Using functional proteomics on rat brain, we show that α7-nAChRs are associated with plasma membrane calcium-ATPase pump isoform 2 (PMCA2). Analysis of α7-nAChR function in hippocampal interneurons in culture shows that PMCA2 activity limits the duration of calcium elevations produced by the receptors. Unexpectedly, PMCA2 inhibition triggers rapid calcium-dependent loss of α7-nAChR clusters. This extreme regulatory response is mediated by CaMKII, involves proteasome activity, depends on the second intracellular loop of α7-nAChR subunits, and is specific in that it does not alter two other classes of calcium-permeable ionotropic receptors on the same neurons. A critical link is provided by the scaffold protein PSD-95 (postsynaptic density-95), which is associated with α7-nAChRs and constrains their mobility as revealed by single-particle tracking on neurons. The PSD-95 link is required for PMCA2-mediated removal of α7-nAChR clusters. This three-component combination of PMCA2, PSD-95, and α7-nAChR offers a novel mechanism for tight control of calcium dynamics in neurons.