Receptors GCPRs

Receptors which respond to noradrenaline are called adrenoceptors (as they also respond to adrenaline). All of these receptors are slower-acting G protein-coupled receptors (GCPRs) which are located on cell membranes. It has been known for over 50 years that there are two broad classes of such receptors and these are termed a-and (3-adrenoceptors, and it has been clear since the 1970s that some adrenoceptors are located presynaptically as well as postsy-naptically. The coming of molecular biology allowed the genes for six human a-adrenoceptors to be identified (a1A, a1B, a1D and a2A, a2B and a2C).16... 

Signal transduction is initiated by the binding of a G-coupled protein receptor (GCPR) to the ligand on the exterior of the cell. Interactions with a nearby G protein inside the cell results in the exchange of bound GDP to GTP and in the release of one of its subunits in a GTP-bound form that activates an ion... 

Gastrin 17 Gastrin releasing peptide receptor, GCPR Leads to pepsin secretion... 

Two AT-II receptors, AT and AT2 are known and show wide distribution (27). The AT receptor has been cloned and predominates ia regions iavolved ia the regulation of blood pressure and water and sodium retention, eg, the aorta, Hver, adrenal cortex, and ia the CNS ia the paraventricular nucleus, area postrema, and nucleus of the soHtary tract. AT2 receptors are found primarily ia the adrenal medulla, utems, and ia the brain ia the locus coeruleus and the medial geniculate nucleus. AT receptors are GCPRs inhibiting adenylate cyclase activity and stimulating phosphoHpases C, A2, and D. AT2 receptors use phosphotyrosiae phosphatase as a transduction system. 

The phenotypic complexity noted for other GCPR diseases is true also for PTHRl mutations. Opposite clinical manifestations have been reported to result from distinct recessive mutations in the gene. These rare variants present as Eiken syndrome, a distinct entity from JMC and Blomstrand s chondrodysplasia and from enchondromatosis. The skeletal features are opposite those in Blomstrand s chondrodysplasia. The Eiken syndrome variant, resulting in a truncation at position 485, may result in a paradoxical phenotype caused by the consequences of disrupting the carboxyl tail of the receptor (60). 

G-coupled protein receptors are involved in many diseases. It is estimated that nearly one-half of prescription drugs target GCPRs, in the treatment of cancer, cardiac malfunction, inflammation, pain, and disorders of the central nervous system. 

Angiotensin II 8 Angiotensin receptor AT, GCPR, G Vasoconstriction, increased vasopressin secretion... 

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