Department of Physiological Chemistry, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, 1-1-1 Ten-nohdai, Tsukuba 305-8571, Japan.
Neuron. 2012 Jan 12;73(1):135-48. doi: 10.1016/j.neuron.2011.09.034.
NMDA receptor activation leads to clathrin-dependent endocytosis of postsynaptic AMPA receptors. Although this process controls long-term depression (LTD) induction in the hippocampus, how it is regulated by neuronal activities is not completely clear. Here, we show that Ca²⁺ influx through the NMDA receptor activates calcineurin and protein phosphatase 1 to dephosphorylate phosphatidylinositol 4-phosphate 5-kinaseγ661 (PIP5Kγ661), the major phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂)-producing enzyme in the brain. Bimolecular fluorescence complementation analysis revealed that the dephosphorylated PIP5Kγ661 became associated with the clathrin adaptor protein complex AP-2 at postsynapses in situ. NMDA-induced AMPA receptor endocytosis and low-frequency stimulation-induced LTD were completely blocked by inhibiting the association between dephosphorylated PIP5Kγ661 and AP-2 and by overexpression of a kinase-dead PIP5Kγ661 mutant in hippocampal neurons. Furthermore, knockdown of PIP5Kγ661 inhibited the NMDA-induced AMPA receptor endocytosis. Therefore, NMDA receptor activation controls AMPA receptor endocytosis during hippocampal LTD by regulating PIP5Kγ661 activity at postsynapses.
NMDA 受体的激活导致突触后 AMPA 受体的网格蛋白依赖性内吞作用。尽管这一过程控制了海马体中的长时程抑制（LTD）诱导，但神经元活动如何调节它还不完全清楚。在这里，我们表明 NMDA 受体通过钙内流激活钙调神经磷酸酶和蛋白磷酸酶 1，使磷脂酰肌醇 4,5-二磷酸 5-激酶γ661（PIP5Kγ661）去磷酸化，PIP5Kγ661 是大脑中主要的磷脂酰肌醇 4,5-二磷酸（PI（4,5）P₂）产生酶。双分子荧光互补分析显示，去磷酸化的 PIP5Kγ661 在突触后原位与网格蛋白衔接蛋白复合物 AP-2 结合。通过抑制去磷酸化的 PIP5Kγ661 与 AP-2 之间的结合，以及在海马神经元中过表达激酶失活的 PIP5Kγ661 突变体，完全阻断了 NMDA 诱导的 AMPA 受体内吞作用和低频刺激诱导的 LTD。此外，PIP5Kγ661 的敲低抑制了 NMDA 诱导的 AMPA 受体内吞作用。因此，NMDA 受体的激活通过调节突触后 PIP5Kγ661 的活性来控制海马体 LTD 期间 AMPA 受体的内吞作用。
