Kim E, Naisbitt S, Hsueh Y P, Rao A, Rothschild A, Craig A M, Sheng M
Howard Hughes Medical Institute, Department of Neurobiology, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
J Cell Biol. 1997 Feb 10;136(3):669-78. doi: 10.1083/jcb.136.3.669.
The molecular mechanisms underlying the organization of ion channels and signaling molecules at the synaptic junction are largely unknown. Recently, members of the PSD-95/SAP90 family of synaptic MAGUK (membrane-associated guanylate kinase) proteins have been shown to interact, via their NH2-terminal PDZ domains, with certain ion channels (NMDA receptors and K+ channels), thereby promoting the clustering of these proteins. Although the function of the NH2-terminal PDZ domains is relatively well characterized, the function of the Src homology 3 (SH3) domain and the guanylate kinase-like (GK) domain in the COOH-terminal half of PSD-95 has remained obscure. We now report the isolation of a novel synaptic protein, termed GKAP for guanylate kinase-associated protein, that binds directly to the GK domain of the four known members of the mammalian PSD-95 family. GKAP shows a unique domain structure and appears to be a major constituent of the postsynaptic density. GKAP colocalizes and coimmunoprecipitates with PSD-95 in vivo, and coclusters with PSD-95 and K+ channels/NMDA receptors in heterologous cells. Given their apparent lack of guanylate kinase enzymatic activity, the fact that the GK domain can act as a site for protein-protein interaction has implications for the function of diverse GK-containing proteins (such as p55, ZO-1, and LIN-2/CASK).
离子通道和信号分子在突触连接处的组织背后的分子机制在很大程度上尚不清楚。最近，突触MAGUK（膜相关鸟苷酸激酶）蛋白的PSD - 95 / SAP90家族成员已被证明通过其NH2末端的PDZ结构域与某些离子通道（NMDA受体和K +通道）相互作用，从而促进这些蛋白质的聚集。虽然NH2末端PDZ结构域的功能相对已得到较好的表征，但PSD - 95 COOH末端一半中的Src同源3（SH3）结构域和鸟苷酸激酶样（GK）结构域的功能仍然不清楚。我们现在报告分离出一种新的突触蛋白，称为鸟苷酸激酶相关蛋白（GKAP），它直接与哺乳动物PSD - 95家族四个已知成员的GK结构域结合。GKAP显示出独特的结构域结构，似乎是突触后致密物的主要成分。GKAP在体内与PSD - 95共定位并共免疫沉淀，并且在异源细胞中与PSD - 95和K +通道/ NMDA受体共聚集。鉴于它们明显缺乏鸟苷酸激酶酶活性，GK结构域可作为蛋白质 - 蛋白质相互作用位点这一事实对多种含GK的蛋白质（如p55、ZO - 1和LIN - 2 / CASK）的功能具有重要意义。
