Functional studies for presynatic proteins which may control efficiency of synaptic transmission

Ca^<2+>通过电压依赖性Ca^<2+>通道进入突触前神经末梢触发神经递质释放。近年来，在突触前终末发现了多种蛋白。例如，形成核心复合物并参与突触囊泡胞外分泌的SNARE蛋白，与Ca^<2+>传感器蛋白相关的突触囊泡蛋白或突触囊泡蛋白，也形成复合物的活性区细胞基质蛋白和可能动员突触囊泡的运动蛋白，以及可能控制Ca^<2+>通道活性的Ca^<2+>通道相互作用蛋白。为了研究这些蛋白在调节突触传递效率中的可能作用，我们在长期培养中使用了大鼠颈上神经节神经元之间形成的突触。我们引入了外源性合成肽、蛋白质或转染的突触前蛋白cdna，并通过记录突触前动作电位产生的兴奋性突触后电位来监测突触传递的变化。我们揭示了Ca^<2+>/Calmodulin与syntaxin IA^<1)>结合对SNARE复合物形成的调控机制，脑中表达的三种Ca^<2+>通道的功能差异，活性区细胞基质蛋白的可能作用^<3)>，SV2结合Ca^<2+>传感器synaptotagmin^<4)>对胞外分泌的调控，g蛋白βγ亚基结合n型Ca^<2+>通道^<5)>对胞外分泌的调控。肌球蛋白IIB调节突触囊泡运输，而IIA， Va或Vb不调节（准备重新提交）。

Neurotransmitter release is triggered by Ca^<2+> entered into presynaptic nerve terminals through voltage-dependent Ca^<2+> channels activated by an action potential. Recently, various proteins were found in presynaptic terminals. For example, SNARE proteins which form a core complex and involved in synaptic vesicle exocytosis, synaptic vesicle proteins or synaptic vesicle associated with Ca^<2+>sensor proteins, active zone cytomatrix proteins that also form a complex and motor proteins that may mobilize synaptic vesicles, and Ca^<2+> channel interacting proteins which may control Ca^<2+> channel activity.To examine possible roles of these proteins in regulation of synaptic transmission efficiency, we employed synapses formed between rat superior cervical ganglion neurons in long-term culture. We introduced exogenous synthesized peptides or, protein, or transfected cDNAs of a presynaptic protein and monitored changes in synaptic transmissionby recording excitatory postsynaptic potentials generated by presynaptic action potentials. We revealed a mechanism of regulation of SNARE complex formation by binding of Ca^<2+>/Calmodulin to syntaxin IA^<1)>, functional differences between three types of Ca^<2+> channels expressed in the brain^<2)> a possible role of cytomatrix proteins at the active zone^<3)>, regulation of exocytosis by SV2 binding to a Ca^<2+> sensor synaptotagmin^<4)>, regulation of exocytosis by G-protein βγ subunit binding to N-type Ca^<2+> channel^<5)>, regulation of synaptic vesicle trafficking by myosin IIB but not by IIA, Va or Vb (preparing for re-submission).