The Molecular Mechanism Of The Syntaxin-1 Aggregated State Regulating Neurotransmitter Release

Nervous system,known as the most important and complex system in the organism,controls the transmission of various information and maintains the normal operation of the body.Diseases such as Alzheimer's,Autism and Parkinsonism are caused by the nervous system disorder.These diseases cause serious damage to human health.The information transmission between neurons and target cells is achieved by the binding of neurotransmitters released by the presynaptic membrane to receptors on the postsynaptic membrane.This process is based on the fusion of the vesicle membrane with the presynaptic membrane triggered by calcium ions.Among the many proteins involved in membrane fusion,syntaxin-1 plays an extremely important role in promoting vesicle secretion by participating in forming SNARE complex.Researches have found that syntaxin-1 distributes as the form of monomer and polymer on the plasma membrane.The effects of different forms of syntaxin-1 on vesicle secretion are controversial.In order to investigate whether the aggregation state of syntaxin-1 affects neurotransmitter release and normal physiological function in mice,and whether Munc18 and Munc13 interacting with syntaxin-1 are involved in regulating the aggregation of syntaxin-1,we used a combination of optogenetics,electrophysiology and behavioristics for research.In this project,we selected the blue-light sensitive protein AuLOV as the switch to artificially control the aggregation of syntaxin-1 in vitro.A series of fusion proteins were expressed in nerve cells by co-culture of neurons and lentivirus,and the electrical activities of mature neurons were recorded by whole-cell patch-clamp.In addition,we injected the AAV virus into the superior colliculus of the mouse and observed the predatory hunting behavior after a period of time.Our experimental results showed that aggregate syntaxin-1 blocked the spontaneous and evoked release of vesicles,and seriously affected the ability of predation in mice.In addition,we overexpressed AuLOV-labeled syntaxin-1 and Munc18 or Munc13 in nerve cells,respectively,and recorded their electrical activities.The experiment results showed that,overexpression of Munc18,which interacts with syntaxin-1 during vesicle secretion,can restore the ability to promote neurotransmitter release lossed due to syntaxin-1 aggregated to a certain extent.However,Munc13 is not directly involved in the regulation of the aggregation/depolymerization state change of syntaxin-1.These results strongly demonstrated that maintaining the monomer state of syntaxin-1 is the essential condition to ensure accurate and rapid release of neurotransmitters.The investigation about the effect of syntaxin-1 aggregation/depolymerization dynamic change on neurotransmitter release,and whether Munc18 and Munc 13 are involved in regulating its state changes,can further reveal and consummate the molecular mechanism model of neurotransmitter release,provide certain theoretical basis for the pathogenesis and treatment of neurological diseases,and have a certain significance for neuroscience and human development.