Mitchell R, McCulloch D, Lutz E, Johnson M, MacKenzie C, Fennell M, Fink G, Zhou W, Sealfon S C
MRC Brain Metabolism Unit, Edinburgh, UK.
Nature. 1998 Mar 26;392(6674):411-4. doi: 10.1038/32937.
G-protein-coupled receptors of the rhodopsin family transduce many important neural and endocrine signals. These receptors activate heterotrimeric G proteins and in many cases also cause activation of phospholipase D, an enzyme that can be controlled by the small G proteins ARF and RhoA. Here we show that the activation of phospholipase D that is induced by many, but not all, Ca2+-mobilizing G-protein-coupled receptors is sensitive to inhibitors of ARF and of RhoA. Receptors of this type were co-immunoprecipitated with ARF or RhoA on exposure to agonists, and the effects of GTP analogues on ligand binding to the receptor changed to a profile that is characteristic of small G proteins. These receptors contain the amino-acid sequence AsnProXXTyr in their seventh transmembrane domain, whereas receptors capable of activating phospholipase D without involving ARF contain the sequence AspProXXTyr. Mutation of this latter sequence to AsnProXXTyr in the gonadotropin-releasing hormone receptor conferred sensitivity to an inhibitor of ARF, and the reciprocal mutation in the 5-HT2A receptor for 5-hydroxy-tryptamine reduced its sensitivity to the inhibitor. Receptors carrying the AsnProXXTyr motif thus seem to form functional complexes with ARF and RhoA.
视紫红质家族的G蛋白偶联受体可转导许多重要的神经和内分泌信号。这些受体激活异源三聚体G蛋白，并且在许多情况下还会导致磷脂酶D的激活，磷脂酶D是一种可由小G蛋白ARF和RhoA控制的酶。在此我们表明，许多（但不是全部）动员Ca2+的G蛋白偶联受体诱导的磷脂酶D激活对ARF和RhoA的抑制剂敏感。这类受体在暴露于激动剂时会与ARF或RhoA共同免疫沉淀，并且GTP类似物对配体与受体结合的影响会转变为小G蛋白特有的模式。这些受体在其第七跨膜结构域中含有氨基酸序列AsnProXXTyr，而能够在不涉及ARF的情况下激活磷脂酶D的受体则含有AspProXXTyr序列。促性腺激素释放激素受体中该后一序列突变为AsnProXXTyr会使其对ARF抑制剂敏感，而5-羟色胺的5-HT2A受体中的反向突变则降低了其对该抑制剂的敏感性。因此，携带AsnProXXTyr基序的受体似乎与ARF和RhoA形成功能复合物。
