Wheeler David, Sneddon W Bruce, Wang Bin, Friedman Peter A, Romero Guillermo
Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
J Biol Chem. 2007 Aug 24;282(34):25076-87. doi: 10.1074/jbc.M701544200. Epub 2007 Jun 27.
The sodium-hydrogen exchange regulatory factor 1 (NHERF-1/EBP50) interacts with the C terminus of several G protein-coupled receptors (GPCRs). We examined the role of NHERF-1 and the cytoskeleton on the distribution, dynamics, and trafficking of the beta(2)-adrenergic receptor (beta(2)AR; a type A receptor), the parathyroid hormone receptor (PTH1R; type B), and the calcium-sensing receptor (CaSR; type C) using fluorescence recovery after photobleaching, total internal reflection fluorescence, and image correlation spectroscopy. beta(2)AR bundles were observed only in cells that expressed NHERF-1, whereas the PTH1R was localized to bundles that parallel stress fibers independently of NHERF-1. The CaSR was never observed in bundles. NHERF-1 reduced the diffusion of the beta(2)AR and the PTH1R. The addition of ligand increased the diffusion coefficient and the mobile fraction of the PTH1R. Isoproterenol decreased the immobile fraction but did not affect the diffusion coefficient of the beta(2)AR. The diffusion of the CaSR was unaffected by NHERF-1 or the addition of calcium. NHERF-1 reduced the rate of ligand-induced internalization of the PTH1R. This phenomenon was accompanied by a reduction of the rate of arrestin binding to PTH1R in ligand-exposed cells. We conclude that some GPCRs, such as the beta(2)AR, are attached to the cytoskeleton primarily via the binding of NHERF-1. Others, such as the PTH1R, bind the cytoskeleton via several interacting proteins, one of which is NHERF-1. Finally, receptors such as the CaSR do not interact with the cytoskeleton in any significant manner. These interactions, or the lack thereof, govern the dynamics and trafficking of the receptor.
钠氢交换调节因子1（NHERF-1/EBP50）与几种G蛋白偶联受体（GPCR）的C末端相互作用。我们使用光漂白后荧光恢复、全内反射荧光和图像相关光谱技术，研究了NHERF-1和细胞骨架对β2-肾上腺素能受体（β2AR；A型受体）、甲状旁腺激素受体（PTH1R；B型）和钙敏感受体（CaSR；C型）的分布、动力学和运输的作用。仅在表达NHERF-1的细胞中观察到β2AR束，而PTH1R定位于与应力纤维平行的束中，与NHERF-1无关。在束中从未观察到CaSR。NHERF-1降低了β2AR和PTH1R的扩散。配体的添加增加了PTH1R的扩散系数和移动部分。异丙肾上腺素降低了固定部分，但不影响β2AR的扩散系数。CaSR的扩散不受NHERF-1或钙添加的影响。NHERF-1降低了配体诱导的PTH1R内化速率。这种现象伴随着配体暴露细胞中抑制蛋白与PTH1R结合速率的降低。我们得出结论，一些GPCR，如β2AR，主要通过NHERF-1的结合附着于细胞骨架。其他的，如PTH1R，通过几种相互作用蛋白与细胞骨架结合，其中之一是NHERF-1。最后，像CaSR这样的受体不以任何显著方式与细胞骨架相互作用。这些相互作用或缺乏相互作用决定了受体的动力学和运输。
