Adenylyl Cyclase 5 Regulation by G beta gamma Involves Isoform-Specific Use of Multiple Interaction Sites

作者：Brand Cameron S; Sadana Rachna; Malik Sundeep; Smrcka Alan V; Dessauer Carmen W^*

来源：Molecular Pharmacology, 2015, 88(4): 758-767.

DOI：10.1124/mol.115.099556

Adenylyl cyclase (AC) converts ATP into cyclic AMP (cAMP), an important second messenger in cell signaling. Heterotrimeric G proteins and other regulators are important for control of AC activity. Depending on the AC isoform, G beta gamma subunits can either conditionally stimulate or inhibit cAMP synthesis. We previously showed that the G alpha(s)-beta gamma heterotrimer binds to the N terminus (NT) of type 5 AC (AC5). We now show that G beta gamma binds to the NT of a wide variety of AC isoforms. We hypothesized that G beta gamma/AC5 interactions involving inactive heterotrimer and G beta gamma stimulation of AC5 were separable events. Mutations of the G beta gamma "hotspot" show that this site is necessary for AC5 stimulation but not for interactions with the first 198 aa of AC5NT, which is a G protein scaffolding site. This contrasts with AC6, where the G beta gamma hotspot is required for both interactions with AC6NT and for stimulation of AC6. Additionally, the SIGK hotspot peptide disrupts G beta gamma regulation of AC isoforms 1, 2, and 6, but not AC5. G beta gamma also binds the C1/C2 catalytic domains of AC5 and AC6. Finally, cellular interactions with full-length AC5 depend on multiple sites on G beta gamma. This suggests an isoform-specific mechanism in which bound Gbg at the AC5NT is ideally situated for spatiotemporal control of AC5. We propose G beta gamma regulation of AC involves multiple binding events, and the role of the AC NT for mechanisms of regulation by heterotrimeric G protein subunits is isoform-specific.

• 出版日期2015-10