Muscarinic receptors stimulate AC2 by novel phosphorylation sites, whereas G beta gamma subunits exert opposing effects depending on the G-protein source

作者：Shen Jia X; Wachten Sebastian; Halls Michelle L; Everett Katy L; Cooper Dermot M F^*

来源：Biochemical Journal, 2012, 447: 393-405.

DOI：10.1042/BJ20120279

• adenylyl cyclase 2 (AC2)
• protein kinase C (PKC)
• muscarinic receptor
• somatostatin receptor

Direct phosphorylation of AC2 (adenylyl cyclase 2) by PKC (protein kinase C) affords an opportunity for AC2 to integrate signals from non-canonical pathways to produce the second messenger, cyclic AMP. The present study shows that stimulation of AC2 by pharmacological activation of PKC or muscarinic receptor activation is primarily the result of phosphorylation of Ser(490) and Ser(543), as opposed to the previously proposed Thr(1057). A double phosphorylation-deficient mutant (S4901543A) of AC2 was insensitive to PMA (phorbol myristic acid) and CCh (carbachol) stimulation, whereas a double phosphomimetic mutant (S490/543D) mimicked the activity of PKC-activated AC2. Putative G beta gamma-interacting sites are in the immediate environment of these PKC phosphorylation sites (Ser(490) and Ser(543)) that are located within the Clb domain of AC2, suggesting a significant regulatory importance of this domain. Consequently, we examined the effect of both G(q)-coupled muscarinic and G(i)- coupled somatostatin receptors. Employing pharmacological and FRET (fluorescence resonance energy transfer)-based real-time single cell imaging approaches, we found that G beta gamma released from the Gq-coupled muscarinic receptor or G(i)-coupled somatostatin receptors exert inhibitory or stimulatory effects respectively. These results underline the sophisticated regulatory capacities of AC2, in not only being subject to regulation by PKC, but also and in an opposite manner to G beta gamma subunits, depending on their source.

• 出版日期2012-11-1