Hsueh Y P, Sheng M
Howard Hughes Medical Institute and Department of Neurobiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
J Biol Chem. 1999 Jan 1;274(1):532-6. doi: 10.1074/jbc.274.1.532.
The PSD-95 family of PSD-95/Discs large/ZO-1 (PDZ) domain-containing proteins plays a role in the clustering and localization of specific ion channels and receptors at synapses. Previous studies have shown that PSD-95 forms multimers through an N-terminal region (termed the N-segment) and that the multimerization of PSD-95 is critical for its ability to cluster Shaker-type potassium channel Kv1.4 in heterologous cells. We show here that the PSD-95 N-segment functions as a multimerization domain only when located at the N-terminal end of a heterologous protein. A pair of N-terminal cysteines, Cys3 and Cys5, is essential for the ability of PSD-95 to self-associate and to form cell surface clusters with Kv1.4. However, PSD-95 mutants lacking these cysteine residues retain their ability to associate with membranes and to bind to Kv1.4. Unlike wild type PSD-95, the cysteine mutant of PSD-95 cannot form a ternary complex with Kv1.4 and the cell adhesion molecule Fasciclin II. These results suggest that the N-terminal cysteines are essential for PSD-95 multimerization and that multimerization is required for simultaneous binding of multiple membrane protein ligands by PSD-95.
包含 PSD-95/盘状大蛋白/ZO-1（PDZ）结构域的 PSD-95 家族蛋白在特定离子通道和受体于突触处的聚集及定位中发挥作用。先前的研究表明，PSD-95 通过其 N 端区域（称为 N 片段）形成多聚体，并且 PSD-95 的多聚化对于其在异源细胞中聚集 Shaker 型钾通道 Kv1.4 的能力至关重要。我们在此表明，PSD-95 的 N 片段仅位于异源蛋白的 N 端时才作为多聚化结构域发挥作用。一对 N 端半胱氨酸，即 Cys3 和 Cys5，对于 PSD-95 自我缔合以及与 Kv1.4 形成细胞表面簇的能力至关重要。然而，缺乏这些半胱氨酸残基的 PSD-95 突变体仍保留其与膜缔合以及与 Kv1.4 结合的能力。与野生型 PSD-95 不同，PSD-95 的半胱氨酸突变体无法与 Kv1.4 和细胞黏附分子 Fasciclin II 形成三元复合物。这些结果表明，N 端半胱氨酸对于 PSD-95 的多聚化至关重要，并且多聚化是 PSD-95 同时结合多个膜蛋白配体所必需的。
