Hong Yun Hwa, Kim Ji Young, Lee Jeong Ho, Chae Hong Gu, Jang Sung Soo, Jeon Ju Hong, Kim Chul Hoon, Kim Jun, Kim Sang Jeong
Department of Physiology, Seoul National University College of Medicine, Seoul, Korea.
J Neurochem. 2009 Oct;111(1):61-71. doi: 10.1111/j.1471-4159.2009.06289.x. Epub 2009 Jul 17.
Agonist-induced internalization of metabotropic glutamate receptors (mGluRs) plays an important role in neuronal signaling. Although internalization of mGluRs has been reported to be mediated by clathrin-dependent pathway, studies describing clathrin-independent pathways are emerging. Here, we report that agonist-induced internalization of mGluR1alpha is mediated by caveolin. We show that two caveolin-binding motifs of mGluR1alpha interact with caveolin1/2. Using cell surface-immunoprecipitation and total internal reflection fluorescence imaging, we found that agonist-induced internalization of mGluR1alpha is regulated by caveolin-binding motifs of the receptor in heterologous cells. Moreover, in the cerebellum, group I mGluR agonist dihydroxyphenylglycol increased the interaction of phosphorylated caveolin with mGluR1alpha. This interaction was blocked by methyl-beta-cyclodextrin, known to disrupt caveolin/caveolae-dependent signaling by cholesterol depletion. Methyl-beta-cyclodextrin also blocked the agonist-induced internalization of mGluR1alpha. Thus, these findings represent the evidence for agonist-induced internalization of mGluR1alpha via caveolin and suggest that caveolin might play a role in synaptic metaplasticity by regulating internalization of mGluR1alpha in the cerebellum.
促代谢型谷氨酸受体（mGluRs）的激动剂诱导内化在神经元信号传导中起重要作用。尽管已有报道称mGluRs的内化由网格蛋白依赖性途径介导，但描述非网格蛋白依赖性途径的研究也不断涌现。在此，我们报告mGluR1α的激动剂诱导内化由小窝蛋白介导。我们发现mGluR1α的两个小窝蛋白结合基序与小窝蛋白1/2相互作用。通过细胞表面免疫沉淀和全内反射荧光成像，我们发现在异源细胞中，mGluR1α的激动剂诱导内化受该受体的小窝蛋白结合基序调控。此外，在小脑中，I组mGluR激动剂二羟基苯乙二醇增加了磷酸化小窝蛋白与mGluR1α的相互作用。这种相互作用被甲基-β-环糊精阻断，已知甲基-β-环糊精可通过消耗胆固醇破坏小窝蛋白/小窝依赖的信号传导。甲基-β-环糊精也阻断了激动剂诱导的mGluR1α内化。因此，这些发现为mGluR1α通过小窝蛋白的激动剂诱导内化提供了证据，并表明小窝蛋白可能通过调节小脑中mGluR1α的内化在突触可塑性中发挥作用。
