Journal
HUMAN MUTATION
Volume 32, Issue 6, Pages 653-660Publisher
WILEY
DOI: 10.1002/humu.21489
Keywords
pseudohypoparathyroidism; PHP; Albright hereditary osteodystrophy; Gsa; GNAS
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Funding
- German Ministry for Research and Education [BMBF GMG 01GM0315]
- Fritz Thyssen Stiftung
- Piedmont Region Funds for Finalized Research [R4325]
- Cluster of Excellence Inflammation at interfaces
- National Institute of Diabetes and Digestive and Kidney Diseases [R01DK073911, R37DK46718]
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Pseudohypoparathyroidism type Ia (PHPIa) is caused by GNAS mutations leading to deficiency of the alpha-subunit of stimulatory G proteins (Gs alpha) 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 Gs alpha 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 Gs alpha wild-type and expressed in a Gs alpha-null cell line (Gnas(E2-/E2-)). To investigate receptor-mediated cAMP accumulation, we stimulated the endogenous expressed beta(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 Gs alpha deficiency and selectively affects receptor coupling functions of Gs alpha. Hum Mutat 32:653-660, 2011. (C) 2011 Wiley-Liss, Inc.
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