Ballon Daniel R, Flanary Paul L, Gladue Douglas P, Konopka James B, Dohlman Henrik G, Thorner Jeremy
Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720, USA.
Cell. 2006 Sep 22;126(6):1079-93. doi: 10.1016/j.cell.2006.07.030.
G protein-coupled receptors (GPCRs) mediate cellular responses to a variety of stimuli, but how specific responses are regulated has been elusive, as the types of GPCRs vastly outnumber the classes of G protein heterotrimers available to initiate downstream signaling. In our analysis of signaling proteins containing DEP domains ( approximately 90 residue sequence motifs first recognized in fly Dishevelled, worm EGL-10, and mammalian Pleckstrin), we find that DEP domains are responsible for specific recognition of GPCRs. We examined the yeast regulator of G protein signaling (RGS) protein Sst2 and demonstrate that the DEP domains in Sst2 mediate binding to its cognate GPCR (Ste2). DEP-domain-mediated tethering promotes downregulation by placing the RGS protein in proximity to its substrate (receptor-activated Galpha subunit). Sst2 docks to the Ste2 cytosolic tail, but only its unphosphorylated state, allowing for release and recycling of this regulator upon receptor desensitization and internalization. DEP-domain-mediated targeting of effectors and regulators to specific GPCRs provides a means to dictate the nature, duration, and specificity of the response.
G蛋白偶联受体（GPCRs）介导细胞对多种刺激的反应，但由于GPCR的类型远远超过可用于启动下游信号传导的G蛋白异源三聚体的种类，特定反应是如何被调节的一直难以捉摸。在我们对含有DEP结构域（最初在果蝇的Dishevelled、线虫的EGL-10和哺乳动物的Pleckstrin中发现的约90个残基的序列基序）的信号蛋白的分析中，我们发现DEP结构域负责对GPCR的特异性识别。我们研究了酵母G蛋白信号调节（RGS）蛋白Sst2，并证明Sst2中的DEP结构域介导其与同源GPCR（Ste2）的结合。DEP结构域介导的拴系通过将RGS蛋白置于其底物（受体激活的Gα亚基）附近来促进下调。Sst2对接至Ste2的胞质尾部，但仅在其未磷酸化状态下，从而允许该调节因子在受体脱敏和内化时释放并循环利用。DEP结构域介导的效应器和调节因子靶向特定GPCR提供了一种决定反应性质、持续时间和特异性的方法。
