MOLECULAR-BIOLOGY OF ANGIOTENSIN-II RECEPTORS - AN OVERVIEW

Isoforms of angiotensin II receptors: So far, three isoforms of angiot ensin II receptors have been identified by complementary DNA cloning, all with seven transmembrane domain structures. AT(1A) and AT(1B) are the most common isoforms. They are coupled to phospholipase C through Gq/G(11) proteins and to a calcium channel, and negatively coupled to adenyl cyclase. AT(2) is only remotely related to the AT(1) family. Kn own structural details of angiotensin II receptors: Ligand-binding dom ains are being defined in the space surrounded by transmembrane helice s. Coupling to Gq seems to involve the second cytosolic loop. Receptor proteins undergo transition to a low-affinity form, which is desensit ized and internalized. Chromosome location: In the rat, AT(1A), AT(1B) and AT(2) are located on chromosomes 17, 2 and X, respectively. Signa ling pathway: Studies with receptors are revealing several different p athways of angiotensin signaling that modulate protein tyrosine phosph orylation.