Pseudohypoparathyroidism, a novel mutation in the beta gamma-contact region of G(s)alpha impairs receptor stimulation
Pseudohypoparathyroidism, a novel mutation in the beta gamma-contact region of G(s)alpha impairs receptor stimulation
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DOI：
10.1074/jbc.271.33.19653
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发表时间：
1996-08-16
影响因子：
4.8
通讯作者：
Bourne, HR
中科院分区：
文献类型：
--
作者：
Farfel, Z;Iiri, T;Bourne, HR
假甲状腺功能减退症，IA型（PHP-IA），是一种主要遗传的内分泌疾病，其特征是对激素的抗性，这些激素是通过刺激腺苷酸环化酶来起作用的。它是由常染色体突变的遗传引起的，该突变使G（s）的α亚基（alpha（s））灭活，G（s）是腺苷酸环化酶的刺激调节剂。在一个家庭的三个成员中，PHP-IA表型与一个突变（R231H）相关，该突变（R231H）将组氨酸代替Alpha（s）的位置231的精氨酸。我们评估了在HEK293细胞中瞬时转染的α-WT与alpha（S）-R231H的信号传导函数。与表达α-wt的细胞中的cAMP积累相比，表达α-r231H的细胞中cAMP积累的激素受体依赖性刺激降低了75％。第二个突变α（S）-R201c抑制了α（S）的GTPase闭合反应，从而产生了对cAMP积累的刺激。双突变体Alpha（S）-R231H/R201C几乎与Alpha（S）-R201C本身一样刺激CAMP的积累（类似于80％），表明R231H突变选择性地损害受体依赖性信号。在G蛋白异三聚体的三维结构中，ARG-231位于开关2中，被认为与Beta Gamma亚基相互作用，而不是与激素受体相互作用。因此，R231H表型表明，开关2（也许与β伽玛）介导了G蛋白在远离受体-G蛋白接触表面的位点的G蛋白激活。
Pseudohypoparathyroidism, type Ia (PHP-Ia), is a dominantly inherited endocrine disorder characterized by resistance to hormones that act by stimulating adenylyl cyclase. It is caused by inheritance of an autosomal mutation that inactivates the alpha subunit (alpha(s)) of G(s), the stimulatory regulator of adenylyl cyclase. In three members of a family, the PHP-Ia phenotype is associated with a mutation (R231H) that substitutes histidine for an arginine at position 231 in alpha(s). We assessed signaling function of alpha(s)-WT versus alpha(s)-R231H transiently transfected in HEK293 cells. Hormone receptor-dependent stimulation of cAMP accumulation in cells expressing alpha(s)-R231H is reduced by similar to 75% in comparison to cAMP accumulation in cells expressing alpha(s)-WT. A second mutation, alpha(s)-R201C, inhibits the GTPase turnoff reaction of alpha(s), thus producing receptor-independent stimulation of cAMP accumulation. The double mutant, alpha(s)-R231H/R201C, stimulates cAMP accumulation almost as well (similar to 80%) as does alpha(s)-R201C itself, indicating that the R231H mutation selectively impairs receptor-dependent signaling. In three-dimensional structures of G protein heterotrimers, Arg-231 is located in a region, switch 2, that is thought to interact with the beta gamma subunit rather than with the hormone receptor. Thus, the R231H phenotype suggests that switch 2 (perhaps in concert with beta gamma) mediates G protein activation by receptors at a site distant from the receptor-G protein contact surface.