Bai M, Trivedi S, Kifor O, Quinn S J, Brown E M
Endocrine-Hypertension Division, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 1999 Mar 16;96(6):2834-9. doi: 10.1073/pnas.96.6.2834.
We recently demonstrated that the G protein-coupled, extracellular calcium-sensing receptor (CaR) forms disulfide-linked dimers. The functional significance of dimerization of this receptor was suggested by our earlier observations that CaRs carrying certain point mutations exert dominant negative effects on the function of the coexpressed wild-type receptor both in vivo and when cotransfected in human embryonic kidney cells. In this study, we explored the functional consequences of CaR dimerization. Coexpression in human embryonic kidney cells of specific pairs of mutant CaRs, each with reduced or absent activity because of distinct loss-of-function mutations, results in the formation of heterodimers and partially reconstitutes extracellular calcium-dependent signaling. Moreover, our results suggest that the CaR has at least two functionally separable domains. However, the presence of an abnormal domain in each mutant monomer substantially impairs the function of the CaR heterodimer, resulting in the reconstituted CaRs having characteristics distinct from those of the wild-type CaR. Our study suggests that intermolecular interactions within the dimeric CaR are important for the receptor's function.
我们最近证明，G蛋白偶联的细胞外钙敏感受体（CaR）形成二硫键连接的二聚体。我们早期的观察结果提示了该受体二聚化的功能意义，即携带某些点突变的CaR在体内以及与人胚肾细胞共转染时，对共表达的野生型受体的功能发挥显性负效应。在本研究中，我们探究了CaR二聚化的功能后果。在人胚肾细胞中共表达特定的突变CaR对，每个突变CaR由于不同的功能丧失突变而活性降低或丧失，结果导致异二聚体的形成，并部分重建细胞外钙依赖性信号传导。此外，我们的结果提示CaR至少有两个功能可分离的结构域。然而，每个突变单体中异常结构域的存在严重损害了CaR异二聚体的功能，导致重建的CaR具有与野生型CaR不同的特性。我们的研究表明，二聚体CaR内的分子间相互作用对受体功能很重要。
