Search

Rapid, synapse-specific neurotransmission requires the precise alignment of presynaptic neurotransmitter release and postsynaptic receptors. How postsynaptic glutamate receptor accumulation is induced during maturation is not well understood. We find that in cultures of dissociated hippocampal neurons at 11 days in vitro (DIV) numerous synaptic contacts already exhibit pronounced accumulations of the pre- and postsynaptic markers synaptotagmin, synaptophysin, synapsin, bassoon, VGluT1, PSD-95, and Shank. The presence of an initial set of AMPARs and NMDARs is indicated by miniature excitatory postsynaptic currents (mEPSCs). However, AMPAR and NMDAR immunostainings reveal rather smooth distributions throughout dendrites and synaptic enrichment is not obvious. We found that brief periods of Ca2+ influx through NMDARs induced a surprisingly rapid accumulation of NMDARs within 1 min, followed by accumulation of CaMKII and then AMPARs within 2-5 min. Postsynaptic clustering of NMDARs and AMPARs was paralleled by an increase in their mEPSC amplitudes. A peptide that blocked the interaction of NMDAR subunits with PSD-95 prevented the NMDAR clustering. NMDAR clustering persisted for 3 days indicating that brief periods of elevated glutamate fosters permanent accumulation of NMDARs at postsynaptic sites in maturing synapses. These data support the model that strong glutamatergic stimulation of immature glutamatergic synapses results in a fast and substantial increase in postsynaptic NMDAR content that required NMDAR binding to PSD-95 or its homologues and is followed by recruitment of CaMKII and subsequently AMPARs.

Schizophrenia is a psychiatric disorder that affects over 20 million people globally. Notably, schizophrenia is associated with decreased density of dendritic spines and decreased levels of d-serine, a co-agonist required for opening of the N-methyl-d-aspartate receptor (NMDAR). We hypothesized that lowered d-serine levels associated with schizophrenia would enhance ion flux-independent signaling by the NMDAR, driving destabilization and loss of dendritic spines. We tested our hypothesis using the serine racemase knockout (SRKO) mouse model, which lacks the enzyme for d-serine production. We show that activity-dependent spine growth is impaired in SRKO mice, but can be acutely rescued by exogenous d-serine. Moreover, we find a significant bias of synaptic plasticity toward spine shrinkage in the SRKO mice as compared to wild-type littermates. Notably, we demonstrate that enhanced ion flux-independent signaling through the NMDAR contributes to this bias toward spine destabilization, which is exacerbated by an increase in synaptic NMDARs in hippocampal synapses of SRKO mice. Our results support a model in which lowered d-serine levels associated with schizophrenia enhance ion flux-independent NMDAR signaling and bias toward spine shrinkage and destabilization.

NMDA receptors play vital roles in a broad array of essential brain functions, from synaptic transmission and plasticity to learning and memory. Historically, the fundamental roles of NMDARs were attributed to their specialized properties of ion flux. More recently, it has become clear that NMDARs also signal in an ion flux-independent manner. Here, we review these non-ionotropic NMDAR signaling mechanisms that have been reported to contribute to a broad array of neuronal functions and dysfunctions including synaptic transmission and plasticity, cell death and survival, and synaptic alterations associated with neurological disorders.

Microenvironmental and molecular factors mediating the progression of Breast Ductal Carcinoma In Situ (DCIS) are not well understood, impeding the development of prevention strategies and the safe testing of treatment de-escalation. We addressed methodological barriers and characterized the mutational, transcriptional, histological, and microenvironmental landscape across 85 multiple microdissected regions from 39 cases. Most somatic alterations, including whole-genome duplications, were clonal, but genetic divergence increased with physical distance. Phenotypic and subtype heterogeneity was frequently associated with underlying genetic heterogeneity and regions with low-risk features preceded those with high-risk features according to the inferred phylogeny. B- and T-lymphocytes spatial analysis identified three immune states, including an epithelial excluded state located preferentially at DCIS regions, and characterized by histological and molecular features of immune escape, independently from molecular subtypes. Such breast pre-cancer atlas with uniquely integrated observations will help scope future expansion studies and build finer models of outcomes and progression risk.

Dynamic control of protein degradation via the ubiquitin proteasome system (UPS) is thought to play a crucial role in neuronal function and synaptic plasticity. The proteasome subunit Rpt6, an AAA ATPase subunit of the 19S regulatory particle (RP), has emerged as an important site for regulation of 26S proteasome function in neurons. Phosphorylation of Rpt6 on serine 120 (S120) can stimulate the catalytic rate of substrate degradation by the 26S proteasome and this site is targeted by the plasticity-related kinase Ca2+/calmodulin-dependent kinase II (CaMKII), making it an attractive candidate for regulation of proteasome function in neurons. Several in vitro studies have shown that altered Rpt6 S120 phosphorylation can affect the structure and function of synapses. To evaluate the importance of Rpt6 S120 phosphorylation in vivo, we created two mouse models which feature mutations at S120 that block or mimic phosphorylation at this site. We find that peptidase and ATPase activities are upregulated in the phospho-mimetic mutant and downregulated in the phospho-dead mutant [S120 mutated to aspartic acid (S120D) or alanine (S120A), respectively]. Surprisingly, these mutations had no effect on basal synaptic transmission, long-term potentiation (LTP), and dendritic spine dynamics and density in the hippocampus. Furthermore, these mutants displayed no deficits in cued and contextual fear memory. Thus, in a mouse model that blocks or mimics phosphorylation at this site, either compensatory mechanisms negate these effects, or small variations in proteasome activity are not enough to induce significant changes in synaptic structure, plasticity, or behavior.

Female entertainment and sex workers (FESW) have high rates of alcohol and amphetamine-type stimulant (ATS) use, increasing risk for HIV/sexually transmitted infections (STI), and other negative outcomes. A prospective cohort of 1,198 FESW in a HIV/ATS use prevention intervention in Cambodia was assessed for alcohol and stimulant use disorders (AUD and SUD) using the Alcohol and Substance Use Involvement (ASSIST) scale. STI history was measured by self-report at baseline and at quarterly follow-up visits. Participants were asked if they had been diagnosed with an STI by a medical provider in the past 3 months. Marginal structural models were used to estimate joint effects of AUD and SUD on recent STI. At baseline, one-in-four screened AUD positive and 7% screened positive for SUD. At 18-months, 26% reported ≥1 recent STI. Accounting for time-varying and other known confounders, the adjusted odds ratio (AOR) for recent STI associated with AUD alone and SUD alone were 2.8 (95% CI:1.5-5.1) and 3.5 (95% CI:1.1-11.3), respectively. The AOR for joint effects of AUD and SUD was 5.7 (95% CI:2.2-15.2). AUD and SUD are independently and jointly associated with greater odds of STI among Cambodian FESW. Further research is critical for understanding how AUD and SUD potentiate biological and behavioural pathways that influence STI acquisition and to inform HIV risk-reduction interventions in FESW.

Experience-dependent refinement of neuronal connections is critically important for brain development and learning. Here, we show that ion-flow-independent NMDA receptor (NMDAR) signaling is required for the long-term dendritic spine growth that is a vital component of brain circuit plasticity. We find that inhibition of p38 mitogen-activated protein kinase (p38 MAPK), which is downstream of non-ionotropic NMDAR signaling in long-term depression (LTD) and spine shrinkage, blocks long-term potentiation (LTP)-induced spine growth but not LTP. We hypothesize that non-ionotropic NMDAR signaling drives the cytoskeletal changes that support bidirectional spine structural plasticity. Indeed, we find that key signaling components downstream of non-ionotropic NMDAR function in LTD-induced spine shrinkage are also necessary for LTP-induced spine growth. Furthermore, NMDAR conformational signaling with coincident Ca2+ influx is sufficient to drive CaMKII-dependent long-term spine growth, even when Ca2+ is artificially driven through voltage-gated Ca2+ channels. Our results support a model in which non-ionotropic NMDAR signaling gates the bidirectional spine structural changes vital for brain plasticity.

Female entertainment and sex workers (FESW) are vulnerable to violence, which impedes safer sex behaviors and increases risk of HIV. FESW are also disproportionately affected by co-occurring psychosocial health conditions, including substance use, depression, and economic insecurity, which increased risk of exposure to violence. We used a syndemic framework to examine the effects of co-occurring psychosocial conditions on the risk of client-perpetrated physical and sexual violence against FESW. Data were collected among 1198 Cambodian FESW on recent client-perpetrated physical and sexual violence, and psychosocial conditions (psychological distress, alcohol consumption, amphetamine-type stimulant (ATS) use, debts, housing, and food insecurity). Bivariate and multivariate logistic regressions were conducted. Prevalence of physical and sexual violence from clients was 4.8% and 6.9%, respectively. Client-perpetrated physical violence was associated with housing insecurity, ATS use, and psychological distress. All psychosocial conditions, except ATS, were associated with exposure to sexual violence. In multivariable models, odds of client-perpetrated physical violence were twice higher among women with ≥ 4 compared to ≤ 3 psychosocial conditions. Risk of sexual violence increased with the number of psychosocial conditions. Compared to those with ≤ 1 condition, FESW with two psychosocial conditions had twice the odds (AOR = 2.08; 95% CI 1.00-4.31) and women with 5-6 psychosocial conditions had eightfold higher odds (AOR = 8.10; 95% CI 3.4-19.31) of sexual violence from clients. Our findings support a syndemic model of co-occurring psychosocial conditions among FESW that are associated with increased risk of violence. Violence prevention interventions targeting FESW should adopt comprehensive approaches that address co-occurring psychosocial conditions.

Convalescing coronavirus disease 2019 (COVID-19) patients mount robust T cell responses against SARS-CoV-2, suggesting an important role of T cells in viral clearance. To date, the phenotypes of SARS-CoV-2-specific T cells remain poorly defined. Using 38-parameter CyTOF, we phenotyped longitudinal specimens of SARS-CoV-2-specific CD4+ and CD8+ T cells from nine individuals who recovered from mild COVID-19. SARS-CoV-2-specific CD4+ T cells were exclusively Th1 cells and predominantly Tcm cells with phenotypic features of robust helper function. SARS-CoV-2-specific CD8+ T cells were predominantly Temra cells in a state of less terminal differentiation than most Temra cells. Subsets of SARS-CoV-2-specific T cells express CD127, can proliferate homeostatically, and can persist for over 2 months. Our results suggest that long-lived and robust T cell immunity is generated following natural SARS-CoV-2 infection and support an important role of SARS-CoV-2-specific T cells in host control of COVID-19.

Structural plasticity of dendritic spines is a key component of the refinement of synaptic connections during learning. Recent studies highlight a novel role for the NMDA receptor (NMDAR), independent of ion flow, in driving spine shrinkage and LTD. Yet little is known about the molecular mechanisms that link conformational changes in the NMDAR to changes in spine size and synaptic strength. Here, using two-photon glutamate uncaging to induce plasticity at individual dendritic spines on hippocampal CA1 neurons from mice and rats of both sexes, we demonstrate that p38 MAPK is generally required downstream of non-ionotropic NMDAR signaling to drive both spine shrinkage and LTD. In a series of pharmacological and molecular genetic experiments, we identify key components of the non-ionotropic NMDAR signaling pathway driving dendritic spine shrinkage, including the interaction between NOS1AP (nitric oxide synthase 1 adaptor protein) and neuronal nitric oxide synthase (nNOS), nNOS enzymatic activity, activation of MK2 (MAPK-activated protein kinase 2) and cofilin, and signaling through CaMKII. Our results represent a large step forward in delineating the molecular mechanisms of non-ionotropic NMDAR signaling that can drive shrinkage and elimination of dendritic spines during synaptic plasticity.SIGNIFICANCE STATEMENT Signaling through the NMDA receptor (NMDAR) is vitally important for the synaptic plasticity that underlies learning. Recent studies highlight a novel role for the NMDAR, independent of ion flow, in driving synaptic weakening and dendritic spine shrinkage during synaptic plasticity. Here, we delineate several key components of the molecular pathway that links conformational signaling through the NMDAR to dendritic spine shrinkage during synaptic plasticity.

Hypothetical purchase tasks are a widely used tool to determine the reinforcing value of commodities, especially commodities which are difficult to deliver experimentally. Amazon Mechanical Turk users (N = 375) completed two novel hypothetical purchase tasks (quantity of purchase and probability of purchase) and other measures to estimate how much an individual values the opportunity to exercise in a gym. We examined correlations between demand indices generated by each task and measures related to physical activity. In addition, we compared rates of systematic and nonsystematic responding between the two tasks. Exploratory analyses of demand indices and measures of physical activity suggest initial evidence of construct validity for each task. When accounting for an order effect, the probability of purchase task generated significantly lower rates of nonsystematic responding compared to the quantity of purchase task (2.87% vs. 14.6%, respectively). We discuss how these results may inform improved construction of future hypothetical purchase tasks and implications for using likelihood and quantity purchase tasks. Keywords Behavioral economics * Hypothetical purchase task * Value of physical activity * Exercise * Demand, Sedentary individuals are at increased risk of heart disease and heart attack, high blood pressure, high cholesterol, being overweight or obese, diabetes, and stroke, and are at higher risk of [...]