Mechanisms of disease: Mutations of G proteins and G-protein-coupled receptors in endocrine diseases.
G proteins and G-protein-coupled receptors (GPCRs) mediate the effects of a number of hormones. Genes that encode these molecules are subject to loss-of function or gain-of-function mutations that result in endocrine disorders. Loss-of-function mutations prevent signaling in response to the corresponding agonist and cause resistance to hormone actions, which mimics hormone deficiency. Gain-of-function mutations lead to constitutive, agonist-independent activation of signaling, which mimics hormone excess. Disease-causing mutations of GPCRs have been identified in patients with various disorders of the pituitary-thyroid, pituitary-gonadal and pituitary-adrenal axes, and in those with abnormalities in food intake, growth, water balance and mineral-ion turnover. The only mutational changes in G proteins unequivocally associated with endocrine disorders occur in GNAS (guanine nucleotide-binding protein G-stimulatory subunit alpha, or G(s)alpha). Heterozygous loss-of-function mutations of GNAS in the active, maternal allele cause resistance to hormones that act through G(s)alpha-coupled GPCRs, whereas somatic gain-of-function mutations cause proliferation of endocrine cells that recognize cyclic AMP as a mitogen. The study of mutations in G proteins and GPCRs has already had major implications for understanding the molecular basis of rare endocrine diseases, as well as susceptibility to multifactorial disorders that are associated with polymorphisms in these genes.
Lania
Andrea G
AG
Endocrine Unit, Department of Medical Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore, Policlinico, Mangiagalli, Regina Elena, Milan, Italy.
Mantovani
Giovanna
G
Spada
Anna
A
D000311:Adrenal Glands / Q000502:physiology; D004700:Endocrine System Diseases / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000235:genetics*; D006066:Gonads / Q000502:physiology; D006130:Growth Disorders / Q000209:etiology; D006801:Humans; D008903:Minerals / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D009765:Obesity / Q000209:etiology; D010902:Pituitary Gland / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D013961:Thyroid Gland / Q000502:physiology; D014131:Trace Elements / Q000172:deficiency; D014882:Water-Electrolyte Balance / Q000502:physiology; D014883:Water-Electrolyte Imbalance / Q000209:etiology
D008903:Minerals; D043562:Receptors, G-Protein-Coupled; D014131:Trace Elements; D019204:GTP-Binding Proteins