Sihra T S, Wang J K, Gorelick F S, Greengard P
Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10021.
Proc Natl Acad Sci U S A. 1989 Oct;86(20):8108-12. doi: 10.1073/pnas.86.20.8108.
Depolarization of isolated nerve terminals (synaptosomes) has been shown to stimulate neurotransmitter release and to increase the phosphorylation state of a number of proteins, including synapsin I, in a Ca2+-dependent manner. Synapsin I, a prominent nerve terminal phosphoprotein, interacts with the cytoplasmic surface of small synaptic vesicles and with cytoskeletal elements in a phosphorylation-dependent manner. In the present study we have found that depolarization of synaptosomes resulted in a rapid (2-5 sec) translocation of synapsin I from the particulate to the cytosolic (soluble) fraction. This translocation of synapsin I correlated with its phosphorylation state and was dependent on the presence of Ca2+ in the incubation medium. The stoichiometry of phosphorylation of soluble synapsin I was considerably higher than that of synapsin I in the particulate fraction, under both basal and depolarizing conditions. These data are consistent with the hypothesis that, in situ, the phosphorylation of synapsin I promotes its translocation from synaptic vesicles/cytoskeleton to the cytosol. This phosphorylation/translocation may be instrumental in regulating the release of neurotransmitter.
已表明，分离的神经末梢（突触体）去极化可刺激神经递质释放，并以钙依赖的方式增加包括突触素I在内的多种蛋白质的磷酸化状态。突触素I是一种显著的神经末梢磷蛋白，以磷酸化依赖的方式与小突触囊泡的胞质表面和细胞骨架成分相互作用。在本研究中，我们发现突触体去极化导致突触素I迅速（2 - 5秒）从颗粒部分转移至胞质（可溶性）部分。突触素I的这种转移与其磷酸化状态相关，并依赖于孵育培养基中钙的存在。在基础和去极化条件下，可溶性突触素I的磷酸化化学计量比均显著高于颗粒部分的突触素I。这些数据与以下假设一致：在原位，突触素I的磷酸化促进其从突触囊泡/细胞骨架向胞质溶胶的转移。这种磷酸化/转移可能有助于调节神经递质的释放。
