| Modification Notes |
Adenylyl cyclases function to convert ATP to cyclic AMP in response to activation by a variety of hormones, neurotransmitters and other regulatory molecules. Adenylyl cyclases respond to receptor-initiated signals, mediated by the Gs and Gi heterotrimeric G proteins. The binding of an agonist to a Gs-coupled receptor catalyzes the exchange of GDP (bound to Ga s) for GTP, dissociation of GTP-Ga s from Gb g and Ga s-mediated activation of adenylyl cyclase. Adenylyl cyclase type VII (A cyclase VII) is expressed in specific nephron segments and renal proximal tubules. All of the A cyclase isoforms, except VIII, are expressed in glomeruli. Ca2+/calmodulin-independent isoform VII is localized to sites in position to the basolateral extensions of marginal cells and exhibits moderate staining in type II and type IV fibrocytes in rat cochlea. Sustained activation of cAMP system increases expression of A cyclase I, III, VI, VII and IV, whereas the level of A cyclase II is decreased, and results in increase of cAMP accumulation. Acute activation of the D2 dopaminergic and m4 muscarinic receptors stimulates A cyclase VII, whereas chronic receptor activation leads to a reduction in A cyclase VII activity. |
