Peptide modulators of adenylyl cyclase signaling: modulation of receptor‐mediated Gβγ signaling (843.6)

The objective of this study was to explore the use of lipidated peptides as peptide modulators of adenylyl cyclase signaling (PMACS). The activity of several palmitoylated PMACS on adenylyl cyclase 2 (AC2) signaling was explored. AC2 is closely related to AC4 and AC7 and all of these isoforms are characterized by their ability to be conditional activated by Gβγ subunits. There are several putative Gβγ binding sites that are conserved between AC2, AC4, and AC7. The domains targeted here included the N‐terminus, a recently identified Gβγ binding region in C1a, and an uncharacterized domain in C2a. Initial studies examined the effect of each peptide on Gβγ potentiation of phorbol ester‐stimulated AC2 activity in intact cells. The peptides targeting the N‐terminus and C1a domain were inactive, however, the C2a domain peptide inhibited completely Gβγ potentiation of AC2 following activation of the D2 dopamine receptor. Additional experiments demonstrated that palmitoylation was required for activity, and that eliminating C terminal amino acids of the C2a‐targeted peptide reduced its potency. The C2a peptide also blocked Gβγ potentiation of Gαs‐stimulated cAMP accumulation of AC2, and Gβγ signaling involving μ opioid receptors. Further studies revealed that the C2a peptide attenuated Gi/o‐coupled receptor‐induced heterologous sensitization of AC2 and potentiated forskolin‐stimulated cAMP accumulation in HEK cells. These findings demonstrate that lipidated peptides can be applied to study receptor‐mediated Gβγ signaling as well as the regulatory properties of adenylyl cyclases. Grant Funding Source : Supported by NIH Research MH60397 and Purdue University Research Incentive Grant