School of Physiology, University of the Witwatersrand Faculty of Health Sciences, Parktown, Johannesburg, South Africa.
Department of Physiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
Mol Cell Endocrinol. 2019 Feb 5;481:53-61. doi: 10.1016/j.mce.2018.11.009. Epub 2018 Nov 23.
GnRH receptor mutations, GluLys and GluAsp, cause congenital hypogonadotropic hypogonadism. The Glu side-chain has been proposed to form an intramolecular salt-bridge with Lys, but conserved intramolecular interaction networks in G protein-coupled receptor crystal structures predict that it interacts with Ser and Trp. We investigated interhelical interactions of Glu that stabilise GnRH receptor folding using functional analyses and computational modelling of mutant receptors. The GluAsp mutant was non-functional, but mutants with hydrophobic amino acids or Arg substituted for Glu were functional, excluding a salt-bridge interaction. The GluArg and TrpArg mutants had decreased affinity for GnRH. Models showed that congenital GluLys and GluAsp mutations disrupt interactions with Ser and Trp respectively, whereas the GluArg and TrpArg mutations preserve intramolecular contacts, but increase distance between the transmembrane helices. Our results show that disruption of interhelical contacts that are conserved in G protein-coupled receptors accounts for the effects of some disease-associated GnRH receptor mutations.
GnRH 受体突变，GluLys 和 GluAsp，导致先天性促性腺激素低下性性腺功能减退症。Glu 侧链被提议与 Lys 形成分子内盐桥，但 G 蛋白偶联受体晶体结构中保守的分子内相互作用网络预测它与 Ser 和 Trp 相互作用。我们使用功能分析和突变受体的计算建模研究了稳定 GnRH 受体折叠的 Glu 间的螺旋相互作用。GluAsp 突变体无功能，但用疏水氨基酸或 Arg 取代 Glu 的突变体具有功能，排除了盐桥相互作用。GluArg 和 TrpArg 突变体对 GnRH 的亲和力降低。模型表明，先天性 GluLys 和 GluAsp 突变分别破坏与 Ser 和 Trp 的相互作用，而 GluArg 和 TrpArg 突变保留了分子内接触，但增加了跨膜螺旋之间的距离。我们的结果表明，破坏 G 蛋白偶联受体中保守的螺旋间相互作用解释了一些与疾病相关的 GnRH 受体突变的影响。
