The Solomon H Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Proc Natl Acad Sci U S A. 2013 Aug 20;110(34):13976-81. doi: 10.1073/pnas.1312467110. Epub 2013 Aug 5.
The dynamic trafficking of AMPA receptors (AMPARs) into and out of synapses is crucial for synaptic transmission, plasticity, learning, and memory. The protein interacting with C-kinase 1 (PICK1) directly interacts with GluA2/3 subunits of the AMPARs. Although the role of PICK1 in regulating AMPAR trafficking and multiple forms of synaptic plasticity is known, the exact molecular mechanisms underlying this process remain unclear. Here, we report a unique interaction between PICK1 and all three members of the protein kinase C and casein kinase II substrate in neurons (PACSIN) family and show that they form a complex with AMPARs. Our results reveal that knockdown of the neuronal-specific protein, PACSIN1, leads to a significant reduction in AMPAR internalization following the activation of NMDA receptors in hippocampal neurons. The interaction between PICK1 and PACSIN1 is regulated by PACSIN1 phosphorylation within the variable region and is required for AMPAR endocytosis. Similarly, the binding of PICK1 to the ubiquitously expressed PACSIN2 is also regulated by the homologous phosphorylation sites within the PACSIN2-variable region. Genetic deletion of PACSIN2, which is highly expressed in Purkinje cells, eliminates cerebellar long-term depression. This deficit can be fully rescued by overexpressing wild-type PACSIN2, but not by a PACSIN2 phosphomimetic mutant, which does not bind PICK1 efficiently. Taken together, our data demonstrate that the interaction of PICK1 and PACSIN is required for the activity-dependent internalization of AMPARs and for the expression of long-term depression in the cerebellum.
AMPA 受体（AMPARs）在突触内外的动态转运对于突触传递、可塑性、学习和记忆至关重要。蛋白激酶 C 和酪蛋白激酶 II 底物在神经元中的所有三个成员（PACSIN）家族与 AMPARs 的 GluA2/3 亚基直接相互作用。尽管已知 PICK1 在调节 AMPAR 转运和多种形式的突触可塑性中的作用，但这一过程的确切分子机制仍不清楚。在这里，我们报告了 PICK1 与神经元特异性蛋白 PACSIN1 之间的独特相互作用，并表明它们与 AMPAR 形成复合物。我们的结果表明，敲低神经元特异性蛋白 PACSIN1 会导致海马神经元中 NMDA 受体激活后 AMPAR 内化显著减少。PICK1 与 PACSIN1 的相互作用受 PACSIN1 可变区内的磷酸化调节，是 AMPAR 内吞作用所必需的。同样，PICK1 与广泛表达的 PACSIN2 的结合也受 PACSIN2 可变区内同源磷酸化位点的调节。在浦肯野细胞中高度表达的 PACSIN2 的基因缺失消除了小脑长时程抑制。野生型 PACSIN2 的过表达可以完全挽救这种缺陷，但不能挽救不能有效结合 PICK1 的 PACSIN2 磷酸模拟突变体。总之，我们的数据表明，PICK1 和 PACSIN 的相互作用对于 AMPAR 的活性依赖性内化和小脑长时程抑制的表达是必需的。
