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Membrane trafficking pathways mediate key microglial activities such as cell migration, cytokine secretion, and phagocytosis. However, the underlying molecular mechanism remains poorly understood. Previously, we found that synaptotagmin‐11 (Syt11), a non‐Ca2+‐binding Syt associated with Parkinson's disease (PD) and schizophrenia, inhibits cytokine release and phagocytosis in primary microglia. Here we reported the in vivo function of Syt11 in microglial immune responses using an inducible microglia‐specific Syt11‐conditional‐knockout (cKO) mouse strain. Syt11‐cKO resulted in activation of microglia and elevated mRNA levels of IL‐6, TNF‐α, IL‐1β, and iNOS in various brain regions under both resting state and LPS‐induced acute inflammation state in adult mice. In a PD mouse model generated by microinjection of preformed α‐synuclein fibrils into the striatum, a reduced number of microglia migrated toward the injection sites and an enhanced phagocytosis of α‐synuclein fibrils by microglia were found in Syt11‐cKO mice. To understand the molecular mechanism of Syt11 function, we identified its direct binding proteins vps10p‐tail‐interactor‐1a (vti1a) and vti1b. The linker domain of Syt11 interacted with both proteins and a peptide derived from it competitively inhibited the interaction of Syt11 with vti1a/vti1b in vitro and in cells. Importantly, application of this peptide induced more cytokine secretion in wild‐type microglia upon LPS treatment, phenocopying defects in Syt11 knockdown cells. Altogether, we propose that Syt11 inhibits microglial activation in vivo and regulates cytokine secretion through interactions with vti1a and vti1b. [ABSTRACT FROM AUTHOR]

α‐Synuclein is a central player in Parkinson's disease (PD) pathology. Various point mutations in α‐synuclein have been identified to alter the protein‐phospholipid binding behavior and cause PD. Therefore, exploration of α‐synuclein‐phospholipid interaction is important for understanding the PD pathogenesis and helping the early diagnosis of PD. Herein, a phospholipid‐decorated liquid crystal (LC)‐aqueous interface is constructed to investigate the binding between α‐synucleins (wild‐type and six familial mutant A30P, E46K, H50Q, G51D, A53E and A53T) and phospholipid. The application of deep learning analyzes and reveals distinct LC signatures generated by the binding of α‐synuclein and phospholipid. This system allows for the identification of single point mutant α‐synucleins with an average accuracy of 98.3±1.3% in a fast and efficient manner. We propose that this analytical methodology provides a new platform to understand α‐synuclein‐lipid interactions, and can be potentially developed for easy identification of α‐synuclein mutations in common clinic. [ABSTRACT FROM AUTHOR]

Recent work has revealed that spontaneous release plays critical roles in the central nervous system, but how it is regulated remains elusive. Here, we report that synaptotagmin‐11 (Syt11), a Ca2+‐independent Syt isoform associated with schizophrenia and Parkinson's disease, suppressed spontaneous release. Syt11‐knockout hippocampal neurons showed an increased frequency of miniature excitatory post‐synaptic currents while over‐expression of Syt11 inversely decreased the frequency. Neither knockout nor over‐expression of Syt11 affected the average amplitude, suggesting the pre‐synaptic regulation of spontaneous neurotransmission by Syt11. Glutathione S‐transferase pull‐down, co‐immunoprecipitation, and affinity‐purification experiments demonstrated a direct interaction of Syt11 with vps10p‐tail‐interactor‐1a (vti1a), a non‐canonical SNARE protein that maintains spontaneous release. Importantly, knockdown of vti1a reversed the phenotype of Syt11 knockout, identifying vti1a as the main target of Syt11 inhibition. Domain analysis revealed that the C2A domain of Syt11 bound vti1a with high affinity. Consistently, expression of the C2A domain alone rescued the phenotype of elevated spontaneous release in Syt11‐knockout neurons similar to the full‐length protein. Altogether, our results suggest that Syt11 inhibits vti1a‐containing vesicles during spontaneous release. [ABSTRACT FROM AUTHOR]