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Functional characterization of GNAS mutations found in patients with pseudohypoparathyroidism type Ic defines a new subgroup of pseudohypoparathyroidism affecting selectively Gsα‐receptor interaction
Author(s) -
Thiele Susanne,
de Sanctis Luisa,
Werner Ralf,
Grötzinger Joachim,
Aydin Cumhur,
Jüppner Harald,
Bastepe Murat,
Hiort Olaf
Publication year - 2011
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.21489
Subject(s) - gnas complex locus , pseudohypoparathyroidism , gs alpha subunit , receptor , endocrinology , medicine , g protein , signal transduction , g protein coupled receptor , biology , genetics , parathyroid hormone , gene , calcium
Pseudohypoparathyroidism type Ia (PHPIa) is caused by GNAS mutations leading to deficiency of the α‐subunit of stimulatory G proteins (Gsα) that mediate signal transduction of G protein‐coupled receptors via cAMP. PHP type Ic (PHPIc) and PHPIa share clinical features of Albright hereditary osteodystrophy (AHO); however, in vitro activity of solubilized Gsα protein is normal in PHPIc but reduced in PHPIa. We screened 32 patients classified as PHPIc for GNAS mutations and identified three mutations (p.E392K, p.E392X, p.L388R) in four unrelated families. These and one novel mutation associated with PHPIa (p.L388P) were introduced into a pcDNA3.1(−) expression vector encoding Gsα wild‐type and expressed in a Gsα‐null cell line (Gnas E2−/E2− ). To investigate receptor‐mediated cAMP accumulation, we stimulated the endogenous expressed β 2 ‐adrenergic receptor, or the coexpressed PTH or TSH receptors, and measured the synthesized cAMP by RIA. The results were compared to receptor‐independent cholera toxin‐induced cAMP accumulation. Each of the mutants associated with PHPIc significantly reduced or completely disrupted receptor‐mediated activation, but displayed normal receptor‐independent activation. In contrast, PHPIa associated p.L388P disrupted both receptor‐mediated activation and receptor‐independent activation. We present a new subgroup of PHP that is caused by Gsα deficiency and selectively affects receptor coupling functions of Gsα. Hum Mutat 32:1–8, 2011. © 2011 Wiley‐Liss, Inc.