Hausdorff W P, Pitcher J A, Luttrell D K, Linder M E, Kurose H, Parsons S J, Caron M G, Lefkowitz R J
Howard Hughes Medical Institute, Department of Medicine, Duke University Medical Center, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1992 Jul 1;89(13):5720-4. doi: 10.1073/pnas.89.13.5720.
A number of lines of evidence suggest that cross-talk exists between the cellular signal transduction pathways involving tyrosine phosphorylation catalyzed by members of the pp60c-src kinase family and those mediated by guanine nucleotide regulatory proteins (G proteins). In this study, we explore the possibility that direct interactions between pp60c-src and G proteins may occur with functional consequences. Preparations of pp60c-src isolated by immunoprecipitation phosphorylate on tyrosine residues the purified G-protein alpha subunits (G alpha) of several heterotrimeric G proteins. Phosphorylation is highly dependent on G-protein conformation, and G alpha(GDP) uncomplexed by beta gamma subunits appears to be the preferred substrate. In functional studies, phosphorylation of stimulatory G alpha (G alpha s) modestly increases the rate of binding of guanosine 5'-[gamma-[35S]thio]triphosphate to Gs as well as the receptor-stimulated steady-state rate of GTP hydrolysis by Gs. Heterotrimeric G proteins may represent a previously unappreciated class of potential substrates for pp60c-src.
大量证据表明，在涉及由pp60c-src激酶家族成员催化的酪氨酸磷酸化的细胞信号转导途径与由鸟嘌呤核苷酸调节蛋白（G蛋白）介导的信号转导途径之间存在相互作用。在本研究中，我们探讨了pp60c-src与G蛋白之间可能发生直接相互作用并产生功能后果的可能性。通过免疫沉淀分离的pp60c-src制剂可使几种异三聚体G蛋白的纯化G蛋白α亚基（Gα）的酪氨酸残基磷酸化。磷酸化高度依赖于G蛋白的构象，未与βγ亚基复合的Gα（GDP）似乎是首选底物。在功能研究中，刺激性Gα（Gαs）的磷酸化适度增加了鸟苷5'-[γ-[35S]硫代]三磷酸与Gs的结合速率以及受体刺激的Gs GTP水解稳态速率。异三聚体G蛋白可能代表了一类以前未被重视的pp60c-src潜在底物。
