REGULATION BY SYNAPSIN-I AND CA2+-CALMODULIN-DEPENDENT PROTEIN-KINASE II OF TRANSMITTER RELEASE IN SQUID GIANT SYNAPSE
REGULATION BY SYNAPSIN-I AND CA2+-CALMODULIN-DEPENDENT PROTEIN-KINASE II OF TRANSMITTER RELEASE IN SQUID GIANT SYNAPSE
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DOI：
10.1113/jphysiol.1991.sp018549
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发表时间：
1991-05-01
影响因子：
5.5
通讯作者：
GREENGARD, P
中科院分区：
文献类型：
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作者：
LLINAS, R;GRUNER, JA;GREENGARD, P
1. 在鱿鱼巨突触中实施突触前或同时突触前和突触后电压钳协议，以确定突触前钙电流 (I(Ca)) 的幅度和时间过程及其与突触前注射蛋白质之前和之后递质释放的关系。 其中包括几种形式的突触蛋白 I、钙-钙调蛋白依赖性蛋白激酶 II（CaM 激酶 II）和亲和素。2。 在电生理测量过程中，通过荧光视频增强显微镜监测这些蛋白质的数量和位置。3． 突触前注射去磷酸化突触蛋白 I 抑制突触传递，其时间过程与蛋白质通过末端的扩散和在活性释放区的作用一致。 开发了一个将突触蛋白 I 扩散到末梢与递质释放相关的数学模型，以帮助解释这些结果。4． 突触蛋白I对递质释放的抑制是可逆的。5． 突触蛋白I的作用具有高度特异性，仅尾部区域或头尾区域的磷酸化可防止突触蛋白I抑制释放。6． 注射经过热处理的突触蛋白 I 或抗生物素蛋白（一种大小和等电点与突触蛋白 I 相似的蛋白质）对递质释放没有影响。7。 发现突触前注射 CaM 激酶 II 可促进递质释放。 这种促进作用可能高达对照反应的 700%，与酶沿前末端长度的渗透水平有关。 这种促进作用的数学模型表明CaM激酶II在末端的分布与促进程度之间的合理拟合。8． 突触后反应的总体形状并未因突触蛋白 I 或 CaM 激酶 II 注射而改变。9。 数据表明，除了释放递质外，钙还会渗透突触前细胞质并激活 CaM 激酶 II。 激活后，CaM 激酶 II 会使突触蛋白 I 磷酸化，从而减少其与囊泡和/或细胞骨架结构的结合，从而在突触前去极化过程中释放更多囊泡。 突触后反应的幅度将受到去极化诱导的 Ca2+ 流入的直接和间接调节。 该模型提供了突触增强的分子机制。
1. Presynaptic or simultaneous pre- and postsynaptic voltage-clamp protocols were implemented in the squid giant synapse in order to determine the magnitude and time course of the presynaptic calcium current (I(Ca)) and its relation to transmitter release before and after presynaptic injection of proteins. These included several forms of synapsin I, calcium-calmodulin-dependent protein kinase II (CaM kinase II) and avidin.2. The quantities and location of these proteins were monitored by fluorescence video-enhanced microscopy during the electrophysiological measurements.3. Presynaptic injection of dephosphorylated synapsin I inhibited synaptic transmission with a time course consistent with diffusion of the protein through the terminal and action at the active release zone. A mathematical model relating the diffusion of synapsin I into the terminal with transmitter release was developed to aid in the interpretation of these results.4. Synapsin I inhibition of transmitter release was reversible.5. The action of synapsin I was highly specific, as phosphorylation of the tail region only or head and tail regions prevented synapsin I from inhibiting release.6. Injections of heat-treated synapsin I or of avidin, a protein with a size and isoelectric point similar to those of synapsin I, had no effect on transmitter release.7. CaM kinase II injected presynaptically was found to facilitate transmitter release. This facilitation, which could be as large as 700% of the control response, was related to the level of penetration of the enzyme along the length of the preterminal. A mathematical model of this facilitation indicates a reasonable fit between the distribution of CaM kinase II within the terminal and the degree of facilitation.8. The overall shape of the postsynaptic response was not modified by either synapsin I or CaM kinase II injection.9. The data suggest that, in addition to releasing transmitter, calcium also penetrates the presynaptic cytosol and activates CaM kinase II. When activated, CaM kinase II phosphorylates synapsin I, which reduces its binding to vesicles and/or cytoskeletal structures, enabling more vesicles to be released during a presynaptic depolarization. The amplitude of the postsynaptic response will then be both directly and indirectly regulated by depolarization-induced Ca2+ influx. This model provides a molecular mechanism for synaptic potentiation.