Azpiazu Inaki, Akgoz Muslum, Kalyanaraman Vani, Gautam N
Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Cell Signal. 2006 Aug;18(8):1190-200. doi: 10.1016/j.cellsig.2005.09.007. Epub 2005 Oct 19.
G protein activation by Gi/Go coupling M2 muscarinic receptors, Gq coupling M3 receptors and Gs coupling beta2 adrenergic receptors causes rapid reversible translocation of the G protein gamma11 subunit from the plasma membrane to the Golgi complex. Co-translocation of the beta1 subunit suggests that gamma11 translocates as a betagamma complex. Pertussis toxin ADP ribosylation of the alphai subunit type or substitution of the C terminal domain of alphao with the corresponding region of alphas inhibits gamma11 translocation demonstrating that alpha subunit interaction with a receptor and its activation are requirements for the translocation. The rate of gamma11 translocation is sensitive to the rate of activation of the G protein alpha subunit. alpha subunit types that show high receptor activated rates of guanine nucleotide exchange in vitro support high rates of gamma11 translocation compared to alpha subunit types that have a relatively lower rate of guanine nucleotide exchange. The results suggest that the receptor induced translocation of gamma11 is controlled by the rate of cycling of the G protein through active and inactive forms. They also demonstrate that imaging of gamma11 translocation can be used as a non-invasive tool to measure the relative activities of wild type or mutant receptor and alpha subunit types in a live cell.
通过Gi/Go偶联M2毒蕈碱受体、Gq偶联M3受体和Gs偶联β2肾上腺素能受体激活G蛋白,会导致G蛋白γ11亚基从质膜快速可逆地转运至高尔基体复合体。β1亚基的共转运表明γ11是以βγ复合体的形式转运的。百日咳毒素对αi亚基类型进行ADP核糖基化修饰,或将αo的C末端结构域替换为αs的相应区域,可抑制γ11转运,这表明α亚基与受体的相互作用及其激活是转运的必要条件。γ11转运的速率对G蛋白α亚基的激活速率敏感。与鸟嘌呤核苷酸交换速率相对较低的α亚基类型相比,在体外显示出高受体激活鸟嘌呤核苷酸交换速率的α亚基类型支持更高的γ11转运速率。结果表明,受体诱导的γ11转运受G蛋白通过活性和非活性形式循环速率的控制。它们还证明,γ11转运成像可作为一种非侵入性工具,用于测量活细胞中野生型或突变型受体及α亚基类型的相对活性。