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

C2结构域首次在一种常规类型的蛋白激酶c中被发现，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激活至关重要。蛋白激酶C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有关。这些包括synaptotagmin， Munc13， rabphilin-3A和Doc2。其中rabphilin-3A和Doc2是在我们实验室发现的。1997 - 1998年，我们重点研究rabphilin-3A和Doc2在神经递质释放中的功能和作用方式。结果表明：(1)鱿鱼巨轴突系统电生理研究表明rabphilin-3A参与Ca^<2+>依赖性神经递质释放。(2)我们发现Doc2直接与Munc13相互作用，Munc13定位于突触前质膜，参与Ca^<2+>依赖的神经递质释放。我们发现位于Doc2的n端附近的区域，称为Mid (Munc13-interacting domain)，直接结合到Munc13的两个c2样结构域之间的区域，称为Did （Doc2-interacting domain）。Doc2-Munc13的相互作用通过二酰基甘油或酚酯与Munc13的c1样结构域的结合而增强。(3)培养大鼠颈上神经节神经元电生理研究表明Doc2-Munc13相互作用参与Ca^<2+>依赖的神经递质释放。利用Doc2缺失突变小鼠海马CA1区域的电生理研究表明，Doc2在基础神经传递中不是必需的，但参与了短期可塑性和长期增强。

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.