Myosin light chain kinase facilitates endocytosis of synaptic vesicles at hippocampal boutons

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• 作者：Lin Li ; Xiaomei Wu ; Hai-Yuan Yue ; Yong-Chuan Zhu and Jianhua Xu
• 刊名：Journal of Neurochemistry
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：138
• 期：1
• 页码：60-73
• 全文大小：1330K
• ISSN：1471-4159

文摘

At nerve terminals, endocytosis efficiently recycles vesicle membrane to maintain synaptic transmission under different levels of neuronal activity. Ca²⁺ and its downstream signal pathways are critical for the activity-dependent regulation of endocytosis. An activity- and Ca²⁺-dependent kinase, myosin light chain kinase (MLCK) has been reported to regulate vesicle mobilization, vesicle cycling, and motility in different synapses, but whether it has a general contribution to regulation of endocytosis at nerve terminals remains unknown. We investigated this issue at rat hippocampal boutons by imaging vesicle endocytosis as the real-time retrieval of vesicular synaptophysin tagged with a pH-sensitive green fluorescence protein. We found that endocytosis induced by 200 action potentials (5–40 Hz) was slowed by acute inhibition of MLCK and down-regulation of MLCK with RNA interference, while the total amount of vesicle exocytosis and somatic Ca²⁺ channel current did not change with MLCK down-regulation. Acute inhibition of myosin II similarly impaired endocytosis. Furthermore, down-regulation of MLCK prevented depolarization-induced phosphorylation of myosin light chain, an effect shared by blockers of Ca²⁺ channels and calmodulin. These results suggest that MLCK facilitates vesicle endocytosis through activity-dependent phosphorylation of myosin downstream of Ca²⁺/calmodulin, probably as a widely existing mechanism among synapses. Our study suggests that MLCK is an important activity-dependent regulator of vesicle recycling in hippocampal neurons, which are critical for learning and memory.