Activity-dependent modifications in synapse structure play a key role in synaptic development and plasticity, but the signaling mechanisms involved are poorly understood. We demonstrate that glutamatergic Drosophila neuromuscular junctions undergo rapid changes in synaptic structure and function in response to patterned stimulation. These changes, which depend on transcription and translation, include formation of motile presynaptic filopodia, elaboration of undifferentiated varicosities, and potentiation of spontaneous release frequency. Experiments indicate that a bidirectional Wnt/Wg signaling pathway underlies these changes. Evoked activity induces Wnt1/Wg release from synaptic boutons, which stimulates both a postsynaptic DFz2 nuclear import pathway, as well as a presynaptic pathway involving GSK-3 β/Shaggy. Our findings suggest that bidirectional Wg signaling operates downstream of synaptic activity to induce modifications in synaptic structure and function. We propose that activation of the postsynaptic Wg pathway is required for the assembly of the postsynaptic apparatus, while activation of the presynaptic Wg pathway regulates cytoskeletal dynamics.

Wnts play pivotal roles during development and in the mature nervous system. However, the mechanism by which Wnts traffic between cells has remained elusive. Here we demonstrate a novel mechanism of Wnt transmission through release of exosome-like vesicles containing the Wnt-binding protein Evenness Interrupted/Wntless/Sprinter (Evi/Wls/Srt). We show that at the Drosophila larval neuromuscular junction (NMJ), presynaptic vesicular release of Evi is required for the secretion of the Wnt, Wingless (Wg). We also show that Evi acts cell-autonomously in the postsynaptic Wnt-receiving cell to target dGRIP, a Wg-receptor-interacting protein, to postsynaptic sites. Upon Evi loss of function, dGRIP is not properly targeted to synaptic sites, interfering with postsynaptic Wnt signal transduction. These findings uncover a previously unknown cellular mechanism by which a secreted Wnt is transported across synapses by Evi-containing vesicles, and reveal novel trafficking functions of Evi in both the Wnt-producing and the Wnt-receiving cell.

Background: Although diffuse alveolar damage and respiratory failure are the key features of coronavirus disease 2019 (COVID-19), the involvement of other organs such as the kidney has also been reported. The reports of the incidence of acute kidney injury (AKI) in COVID-19 patients vary widely. In this study, we report our unique experience with AKI in COVID-19 patients in a low socioeconomic and predominantly ethnic minority group and provide its incidence, risk factors, and prognosis to expand the current understanding of this complication. Methods: In this single-center, retrospective cohort study, we analyzed the data of 469 COVID-19 patients admitted to the Brookdale University Hospital in Brooklyn, NY, from March 18 through April 23, 2020. Information regarding demographics, comorbidities, medications, clinical and laboratory data, and outcomes was collected from the electronic medical records. Both univariate and multivariate analyses were performed to determine the association of AKI with in-hospital mortality. Results: The median age was 66 years (interquartile range [IQR] 25–75; range 19–101 years), and 268 (57.14%) patients were male. Estimated glomerular filtration rate (eGFR) as determined by the Modification of Diet in Renal Disease Study Equation was low (<60 mL/min/1.73 m2) in 207 (44.1%) patients. During hospitalization, 128 (27.3%) patients developed AKI, and the incidence was significantly higher in those patients presenting with a low eGFR (N = 81, 39.1%; p < 0.001). Male sex, hypertension, the use of angiotensin-converting enzyme inhibitors and non-steroidal anti-inflammatories, hemodynamic instability, mechanical ventilation, acute respiratory distress syndrome, and admission elevated ferritin, creatinine kinase, brain natriuretic peptide, and troponin 1 were identified as the risk factors for in-hospital AKI. Ninety-seven (28.45%) patients died in the non-AKI group versus 91 (71.1%) in the AKI group (p < 0.001). The Cox proportional hazard model after adjusting for age, gender, comorbidities, hemodynamic status, and PF ratio (arterial oxygen partial pressure [PaO2]/fractional inspired oxygen [FiO2]) determined that on admission, an elevated blood urea nitrogen (hazard ratio [HR]: 1.75; 95% confidence interval [CI] 1.23–2.48), a low eGFR (HR 1.43; CI 1.1–2.03), AKI stage 1 (HR 1.14; CI 0.64–2.03), AKI stage 2 (HR 1.86; CI 1.03–3.56), and AKI stage 3 (HR 2.1; CI 1.3–2.81) were independent risk factors for in-hospital mortality. Renal replacement therapy (RRT) did not improve survival in stage III AKI. Conclusion: AKI in our hospitalized COVID-19 patients was common and carried a high mortality, especially in patients with AKI stage 3. RRT did not improve survival. Policy changes and planning for this high incidence of AKI in COVID-19 patients and its associated high mortality are necessary at the local and national levels.

Introduction: Gastrointestinal (GI) symptoms are increasingly being recognized in coronavirus disease 2019 (COVID-19). It is unclear if the presence of GI symptoms is associated with poor outcomes in COVID-19. We aim to assess if GI symptoms could be used for prognostication in hospitalized patients with COVID-19. Methods: We retrospectively analyzed patients admitted to a tertiary medical center in Brooklyn,

Actin remodeling has emerged as a critical process during synapse development and plasticity. Thus, understanding the regulatory mechanisms controlling actin organization at synapses is exceedingly important. Here we used the highly plastic Drosophila neuromuscular junction (NMJ) to understand mechanisms of actin remodeling at postsynaptic sites. Previous studies have suggested that the actiinding proteins Spectrin and Coracle play a critical role in NMJ development and the anchoring of glutamate receptors most likely through actin regulation. Here we show that an additional determinant of actin organization at the postsynaptic region is the PDZ protein Baz/Par-3. Decreasing Baz levels in postsynaptic muscles has dramatic consequences for the size of F-actin and spectrin domains at the postsynaptic region. In turn, proper localization of Baz at this site depends on both phosphorylation and dephosphorylation events. Baz phosphorylation by its binding partner, atypical Protein Kinase C (aPKC), is required for normal Baz targeting to the postsynaptic region. However, the retention of Baz at this site depends on its dephosphorylation mediated by the lipid and protein phosphatase PTEN. Misregulation of the phosphorylation state of Baz by genetic alterations in PTEN or aPKC activity has detrimental consequences for postsynaptic F-actin and spectrin localization, synaptic growth, and receptor localization. Our results provide a novel mechanism of postsynaptic actin regulation through Baz, governed by the antagonistic actions of aPKC and PTEN. Given the conservation of these proteins from worms to mammals, these results are likely to provide new insight into actin organization pathways.