ADENYLYL-CYCLASE-6 IS SELECTIVELY REGULATED BY PROTEIN-KINASE A PHOSPHORYLATION IN A REGION INVOLVED IN G-ALPHA(S), STIMULATION

Receptors activate adenylyl cyclases through the G alpha(s) subunit. P revious studies from our laboratory have shown in certain cell types t hat express adenylyl cyclase 6 (AC6), heterologous desensitization inc luded reduction of the capability of adenylyl cyclases to be stimulate d by G alpha(s). Here we further analyze protein kinase A (PKA) effect s on adenylyl cyclases. PKA treatment of recombinant AC6 in insect cel l membranes results in a selective loss of stimulation by high (>10 nM ) concentrations of G alpha(s). Similar treatment of AC1 or AC2 did no t affect G alpha(s) stimulation. Conversion of Ser-674 in AC6 to an Al a blocks PKA phosphorylation and PKA-mediated loss of G alpha(s) stimu lation. A peptide encoding the region 660-682 of AC6 blocks stimulatio n of AC6 and AC2 by high concentrations of G alpha(s). Substitution of Ser-674 to Asp in the peptide renders the peptide ineffective, indica ting that the region 660-682 of AC6 is involved in regulation of signa l transfer from G alpha(s). This region contains a conserved motif pre sent in most adenylyl cyclases; however, the PKA phosphorylation cite is unique to members of the AC6 family, These observations suggest a m echanism of how isoform selective regulatory diversity can be obtained within conserved regions involved in signal communication.