Nakano-Kobayashi Akiko, Yamazaki Masakazu, Unoki Takamitsu, Hongu Tsunaki, Murata Chie, Taguchi Ryo, Katada Toshiaki, Frohman Michael A, Yokozeki Takeaki, Kanaho Yasunori
Department of Physiological Chemistry, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Japan.
EMBO J. 2007 Feb 21;26(4):1105-16. doi: 10.1038/sj.emboj.7601573. Epub 2007 Feb 8.
Synaptic vesicles (SVs) are retrieved by clathrin-mediated endocytosis at the nerve terminals. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] drives this event by recruiting the components of the endocytic machinery. However, the molecular mechanisms that result in local generation of PI(4,5)P2 remain unclear. We demonstrate here that AP-2 complex directly interacts with phosphatidylinositol 4-phosphate 5-kinase gamma661 (PIP5Kgamma661), the major PI(4,5)P2-producing enzyme in the brain. The beta2 subunit of AP-2 was found to bind to the C-terminal tail of PIP5Kgamma661 and cause PIP5Kgamma661 activation. The interaction is regulated by PIP5Kgamma661 dephosphorylation, which is triggered by depolarization in mouse hippocampal neurons. Finally, overexpression of the PIP5Kgamma661 C-terminal region in hippocampal neurons suppresses depolarization-dependent SV endocytosis. These findings provide evidence for the molecular mechanism through which PIP5Kgamma661 locally generates PI(4,5)P2 in hippocampal neurons and suggest a model in which the interaction trigger SV endocytosis.
突触小泡（SVs）在神经末梢通过网格蛋白介导的内吞作用被回收。磷脂酰肌醇4,5-二磷酸[PI(4,5)P2]通过募集内吞机制的组分来驱动这一过程。然而，导致PI(4,5)P2局部生成的分子机制仍不清楚。我们在此证明，AP-2复合物直接与磷脂酰肌醇4-磷酸5-激酶γ661（PIP5Kγ661）相互作用，PIP5Kγ661是大脑中产生PI(4,5)P2的主要酶。发现AP-2的β2亚基与PIP5Kγ661的C末端尾巴结合并导致PIP5Kγ661激活。这种相互作用受PIP5Kγ661去磷酸化调节，而PIP5Kγ661去磷酸化由小鼠海马神经元的去极化触发。最后，海马神经元中PIP5Kγ661 C末端区域的过表达抑制了去极化依赖性的SV内吞作用。这些发现为PIP5Kγ661在海马神经元中局部生成PI(4,5)P2的分子机制提供了证据，并提出了一种相互作用触发SV内吞作用的模型。
