Yamaguchi Yoshiaki, Katoh Hironori, Mori Kazutoshi, Negishi Manabu
Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, 606-8502, Kyoto, Japan.
Curr Biol. 2002 Aug 6;12(15):1353-8. doi: 10.1016/s0960-9822(02)01034-5.
The Galpha subunits of the G(12) family of heterotrimeric G proteins, defined by Galpha(12) and Galpha(13), are involved in many signaling pathways and diverse cellular functions. In an attempt to elucidate downstream effectors of Galpha(12) for cellular functions, we have performed a yeast two-hybrid screening of a rat brain cDNA library and revealed that Ser/Thr protein phosphatase type 5 (PP5) is a novel effector of Galpha(12) and Galpha(13). PP5 is a newly identified phosphatase and consists of a C-terminal catalytic domain and an N-terminal regulatory tetratricopeptide repeat (TPR) domain [2]. Arachidonic acid was recently shown to activate PP5 phosphatase activity by binding to its TPR domain, however the precise regulatory mechanism of PP5 phosphatase activity is not fully determined. In this study, we show that active forms of Galpha(12) and Galpha(13) specifically interact with PP5 through its TPR domain and activate its phosphatase activity about 2.5-fold. Active forms of Galpha(12) and Galpha(13) also enhance the arachidonic acid-stimulated PP5 phosphatase activity about 2.5-fold. Moreover, we demonstrate that the active form of Galpha(12) translocates PP5 to the cell periphery and colocalizes with PP5. These results propose a new signaling pathway of G(12) family G proteins.
异源三聚体G蛋白G(12)家族的Gα亚基，由Gα(12)和Gα(13)所定义，参与许多信号通路和多种细胞功能。为了阐明Gα(12)在细胞功能方面的下游效应器，我们对大鼠脑cDNA文库进行了酵母双杂交筛选，结果显示5型丝氨酸/苏氨酸蛋白磷酸酶（PP5）是Gα(12)和Gα(13)的一种新型效应器。PP5是一种新鉴定出的磷酸酶，由一个C端催化结构域和一个N端调节性四肽重复（TPR）结构域组成[2]。最近研究表明，花生四烯酸通过与PP5的TPR结构域结合来激活其磷酸酶活性，然而PP5磷酸酶活性的确切调节机制尚未完全明确。在本研究中，我们发现Gα(12)和Gα(13)的活性形式通过PP5的TPR结构域与其特异性相互作用，并使其磷酸酶活性激活约2.5倍。Gα(12)和Gα(13)的活性形式还能使花生四烯酸刺激的PP5磷酸酶活性增强约2.5倍。此外，我们证明Gα(12)的活性形式将PP5转运至细胞周边，并与PP5共定位。这些结果提出了一种新的G(12)家族G蛋白信号通路。
