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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]

Non-technical summary Ca2+-regulated axon terminal exocytosis is essential for neuronal communication in the CNS. Besides, the somata may also undergo Ca2+-dependent exocytosis in some neurons in the brain. In the present work we recorded activity/Ca2+-dependent secretion in somata of the mesencephalic trigeminal nucleus (MeV). Following nerve activity, somatic secretion signals are recorded as changes in membrane surface area, as measured by the membrane capacitance. The depolarization-induced somatic exocytosis correlates with transient reduction in the GABA-mediated postsynaptic currents. These results implicated that the somatic secretion may play a role in bidirectional communication between pre- and post-connected neurons in the sensory MeV brain slice neurons. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2011) 119, 342-353. Abstract Action potential (AP) patterns and dopamine (DA) release are known to correlate with rewarding behaviors, but how codes of AP bursts translate into DA release in vivo remains elusive. Here, a given AP pattern was defined by four codes, termed total AP number, frequency, number of AP bursts, and interburst time [ N, f, b, i].. The 'burst effect' was calculated by the ratio (γ) of DA overflow by multiple bursts to that of a single burst when total AP number was fixed. By stimulating the medial forebrain bundle using AP codes at either physiological (20 Hz) or supraphysiological (80 Hz) frequencies, we found that DA was released from two kinetically distinct vesicle pools, the fast-releasable pool (FRP) and prolonged-releasable pool (PRP), in striatal dopaminergic terminals in vivo. We examined the effects of vesicle pools on AP-pattern dependent DA overflow and found, with given 'burst codes' [ b = 8, i = 0.5 s], a large total AP number [ N = 768, f = 80 Hz] produced a facilitating burst-effect (γ[ b8/ b1] = 126 ± 3%), while a small total AP number [ N = 96, 80 Hz] triggered a depressing-burst-effect (γ[ b8/ b1] = 29 ± 4%). Furthermore, we found that the PRP (but not the FRP) predominantly contributed to the facilitating-burst-effect and the FRP played an important role in the depressing-burst effect. Thus, our results suggest that striatal DA release captures pre-synaptic AP pattern information through different releasable pools. [ABSTRACT FROM AUTHOR]

The article discusses the findings of a study to determine the separability of two types of exocytosis. It notes the function of Ca2+-regulated exocytosis the somata of dorsal root ganglions (DRG) in neurotransmitter and hormone release. The experiment cites the use of electrical stimulation to confirm the presence of distinct exocytosis and vesicle pools within DRG neurons without any effect on Ca2+ -independent but voltage-dependent secretion (CVIDS) exocytosis.