Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
J Biol Chem. 2012 Feb 24;287(9):6928-40. doi: 10.1074/jbc.M111.298034. Epub 2012 Jan 5.
G protein-coupled receptor kinases (GRKs) are important regulators of G protein-coupled receptor function and mediate receptor desensitization, internalization, and signaling. While GRKs also interact with and/or phosphorylate many other proteins and modify their function, relatively little is known about the cellular localization of endogenous GRKs. Here we report that GRK5 co-localizes with γ-tubulin, centrin, and pericentrin in centrosomes. The centrosomal localization of GRK5 is observed predominantly at interphase and although its localization is not dependent on microtubules, it can mediate microtubule nucleation of centrosomes. Knockdown of GRK5 expression leads to G2/M arrest, characterized by a prolonged G2 phase, which can be rescued by expression of wild type but not catalytically inactive GRK5. This G2/M arrest appears to be due to increased expression of p53, reduced activity of aurora A kinase and a subsequent delay in the activation of polo-like kinase 1. Overall, these studies demonstrate that GRK5 is localized in the centrosome and regulates microtubule nucleation and normal cell cycle progression.
G 蛋白偶联受体激酶（GRKs）是 G 蛋白偶联受体功能的重要调节剂，介导受体脱敏、内化和信号转导。虽然 GRKs 也与许多其他蛋白质相互作用和/或磷酸化，并修饰它们的功能，但关于内源性 GRKs 的细胞定位知之甚少。在这里，我们报告 GRK5 与中心体中的 γ-微管蛋白、中心粒和中心体蛋白共定位。GRK5 的中心体定位主要在细胞分裂间期观察到，尽管其定位不依赖于微管，但它可以介导中心体的微管核形成。GRK5 表达的敲低导致 G2/M 期阻滞，其特征是 G2 期延长，野生型但不是无催化活性的 GRK5 的表达可以挽救这种阻滞。这种 G2/M 期阻滞似乎是由于 p53 表达增加、极光激酶 A 活性降低以及随后 polo 样激酶 1 的激活延迟所致。总的来说，这些研究表明 GRK5 定位于中心体，并调节微管核形成和正常细胞周期进程。
