background:
GTP-binding proteins (G-proteins)are a family of heterotrimeric proteins that play a critical role in signal transduction by coupling cell surface, 7-transmembrane domain receptors to intracellular signaling pathways including second messenger generation (such as cyclic AMP, calcium and diacylglycerol), protein phosphorylation, ion channel activation, gene induction, cell growth and differentiation. Receptor activation catalyzes the exchange of GTP for GDP bound to the inactive G protein alpha subunit resulting in a conformational change and dissociation of the complex. The G protein alpha and beta-gamma subunits are capable of regulating various cellular effectors. Activation is terminated by a GTPase intrinsic to the G-alpha subunit.
Function:
Guanine nucleotide-binding proteins (G proteins) areinvolved as modulators or transducers in various transmembranesignaling systems. The G(s) protein is involved in hormonalregulation of adenylate cyclase: it activates the cyclase inresponse to beta-adrenergic stimuli. XLas isoforms interact withthe same set of receptors as Gnas isoforms (By similarity).
Subunit:
G proteins are composed of 3 units; alpha, beta andgamma. The alpha chain contains the guanine nucleotide bindingsite. Interacts through its N-terminal region with ALEX which isproduced from the same locus in a different open reading frame.This interaction may inhibit its adenylyl cyclase-stimulatingactivity (By similarity).
Subcellular Location:
Cell membrane; Peripheral membrane protein(By similarity).
DISEASE:
Defects in GNAS are the cause of GNAS hyperfunction(GNASHYP) [MIM:13964]. This condition is characterized byincreased trauma-related bleeding tendency, prolonged bleedingtime, brachydactyly and mental retardation. Both the XLas isoformsand the ALEX protein are mutated which strongly reduces theinteraction between them and this may allow unimpeded activation ofthe XLas isoforms.
Defects in GNAS are a cause of ACTH-independentmacronodular adrenal hyperplasia (AIMAH) [MIM:219080]; also knownas adrenal Cushing syndrome due to AIMAH. A rare adrenal defectcharacterized by multiple, bilateral, non-pigmented, benign,adrenocortical nodules. It results in excessive production ofcortisol leading to ACTH-independent Cushing syndrome. Clinicalmanifestations of Cushing syndrome include facial and trunkalobesity, abdominal striae, muscular weakness, osteoporosis,arterial hypertension, diabetes.
Genetic variations in GNAS are the cause ofpseudohypoparathyroidism type 1B (PHP1B) [MIM:603233]. PHP1B ischaracterized by parathyroid hormone (PTH)-resistant hypocalcemiaand hyperphosphatemia. Patients affected with PHP1B have normalactivity of the product of GNAS, lack developmental defectscharacteristic of AHO, and typically show no other endocrineabnormalities besides resistance to PTH. Note=Most affectedindividuals have defects in methylation of the gene. In some casesmicrodeletions involving the STX16 appear to cause loss ofmethylation at exon A/B of GNAS, resulting in PHP1B. Paternaluniparental isodisomy have also been observed.
Defects in GNAS are the cause of pseudohypoparathyroidismtype 1C (PHP1C) [MIM:612462]. It is a disorder characterized byend-organ resistance to parathyroid hormone, hypocalcemia andhyperphosphatemia. It is commonly associated with Albrighthereditary osteodystrophy whose features are short stature,obesity, round facies, short metacarpals and ectopic calcification.
Similarity:
Belongs to the G-alpha family. G(s) subfamily.
Database links:
UniProtKB/Swiss-Prot: Q5JWF2.2
Important Note:
This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications.
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