Functions and modes of action of proteins with C2 domains in Ca^<2+>-dependent

C2结构域首先在常规类型的蛋白激酶C中被鉴定。C2结构域与Ca^<2+>和磷脂相互作用。蛋白激酶C通过C2结构域与这些因子的相互作用对其活化是必需的。蛋白激酶C具有一个C2结构域，但最近发现了具有两个C2样结构域的蛋白质，越来越多的证据表明，具有两个C2样结构域的蛋白质与Ca_（+）1>依赖性神经递质释放。这些蛋白包括synaptotagmin、Munc 13、rabphilin-3A和Doc 2。其中rabphilin-3A和Doc 2是我们实验室发现的。在1997 - 1998年的资助期间，我们着重研究了rabphilin-3A和Doc 2在神经递质释放中的功能和作用方式。获得的结果如下：（1）利用鱿鱼巨轴突系统的电生理学研究表明，rabphilin-3A参与Ca^<2+>依赖性神经递质的释放。(2)我们发现Doc 2直接与Munc 13相互作用，Munc 13位于突触前质膜，并参与Ca^2+依赖性神经递质的释放，我们发现位于Doc 2 N端附近的Mid（Munc 13相互作用结构域），直接结合Munc 13的两个C2样结构域之间的区域，Doc 2-Munc 13相互作用通过二酰基甘油或佛波酯与Munc 13的C1样结构域的结合而增强。(3)利用培养的大鼠上级颈神经节神经元的电生理研究表明，Doc 2-Munc 13相互作用参与了Ca^<2+>依赖性神经递质的释放;利用Doc 2无效突变小鼠海马脑片CA 1区的电生理研究表明，Doc 2不是基础神经传递所必需的，但参与了短时程可塑性和长时程增强。

The C2 domain has first been identified in a conventional type of protein kinase C.The C2 domain interacts with Ca^<2+> and phospholipids.The interactions of protein kinase C with these factors through the C2 domain are essential for its activation.Protein kinase C has one C2 domain, but proteins having two C2-like domains have recently identified.Accumulating evidence suggests that proteins having two C2-like domains are implicated in Ca_<+1> -dependent neurotrans- mitter release.These include synaptotagmin, Munc13, rabphilin-3A, and Doc2.Of these proteins, rabphilin-3A and Doc2 were discovered in our laboratory.During this support from 1997 to 1998, we have focused on studying the functions and modes of actions of rabphilin-3A and Doc2 in neurotransmitter release.The results obtained are as follows :(1) Electrophysiological study using the squid giant axon system indicates that rabphilin-3A is involved in Ca^<2+> -dependent neurotransmitter release.(2) We have found that Doc2 directly interacts with Munc13, which is localized at the presynaptic plasma membrane and is implicated in Ca^<2+> -dependent neuro- transmitter release.We have found that the region localized near the N-terminus of Doc2, named Mid (Munc13-interacting domain), directly binds to a region between the two C2-like domains of Munc13, named Did (Doc2-interacting domain).The Doc2-Munc13 interaction is enhanced by the binding of diacylglycerol or phorbol ester to the C1-like domain of Munc13.(3) Electrophysiological study using cultured rat superior cervical ganglion neurons indicates that the Doc2-Munc13 interaction is involved in Ca^<2+> -dependent neurotransmitter release.Electrophysiological study using the CA1 region of hippocampal slices of Doc2 null mutant mice indicates that Doc2 is not essential for basal neurotransmission but is involved in short-term plasticity and long-term potentiation.