Xiangya Hospital, State Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan Province 410078, PR China; Department of Immunology, Xinjiang Medical University, Urumqi, Xinjiang Uygur Autonomous Region 830054, PR China.
Biochem Biophys Res Commun. 2013 Sep 13;439(1):12-7. doi: 10.1016/j.bbrc.2013.08.039. Epub 2013 Aug 19.
Mutations in the G-protein-coupled receptor PROKR2 have been identified in patients with idiopathic hypogonadotropic hypogonadism (IHH) and Kallmann syndrome (KS) manifesting with delayed puberty and infertility. Recently, the homozygous mutation V274D was identified in a man displaying KS with an apparent reversal of hypogonadism. The affected amino acid, valine 274, is located at the junction region of the third intracellular loop (IL3) and the sixth transmembrane domain (TM6). In this study, we first studied the effect of V274D and related mutations (V274A, V274T, and V274R) on the signaling activity and cell surface expression of PROKR2. Our data indicate that a charged amino acid substitution at residue 274 of PROKR2 results in low cell surface expression and loss-of-function. Furthermore, we studied the effects of two clusters of basic amino acids located at the proximal region of Val274 on the cell surface expression and function of PROKR2. The deletion of RRK (270-272) resulted in undetectable cell surface expression, whereas RKR (264-266)-deleted PROKR2 was expressed normally on the cell surface but showed loss-of-function due to a deficiency in G-protein coupling. Our data indicate that the distal region of the IL3 of PROKR2 may differentially influence receptor trafficking and G-protein coupling.
G 蛋白偶联受体 PROKR2 的突变已在表现为青春期延迟和不育的特发性低促性腺激素性性腺功能减退症（IHH）和 Kallmann 综合征（KS）患者中被发现。最近，在一名表现为 KS 的患者中发现了纯合突变 V274D，该患者的性腺功能减退症明显逆转。受影响的氨基酸缬氨酸 274 位于第三细胞内环（IL3）和第六跨膜域（TM6）的连接区域。在这项研究中，我们首先研究了 V274D 及其相关突变（V274A、V274T 和 V274R）对 PROKR2 信号活性和细胞表面表达的影响。我们的数据表明，PROKR2 残基 274 处带电荷的氨基酸取代导致细胞表面表达降低和功能丧失。此外，我们研究了位于 Val274 近端的两个碱性氨基酸簇对 PROKR2 细胞表面表达和功能的影响。RRK（270-272）缺失导致细胞表面表达不可检测，而 RKR（264-266）缺失的 PROKR2 正常表达在细胞表面，但由于 G 蛋白偶联不足而表现出功能丧失。我们的数据表明，PROKR2 的 IL3 远端区域可能会对受体转运和 G 蛋白偶联产生不同的影响。
