PT  - JOURNAL ARTICLE
AU  - Tanya A Baldwin
AU  - Yong Li
AU  - Cameron S Brand
AU  - Val J Watts
AU  - Carmen W Dessauer
TI  - Insights Into The Regulatory Properties of Human Adenylyl Cyclase Type 9
AID  - 10.1124/mol.118.114595
DP  - 2019 Jan 01
TA  - Molecular Pharmacology
PG  - mol.118.114595
4099  - http://molpharm.aspetjournals.org/content/early/2019/01/28/mol.118.114595.short
4100  - http://molpharm.aspetjournals.org/content/early/2019/01/28/mol.118.114595.full
AB  - Membrane bound adenylyl cyclase (AC) isoforms have distinct regulatory mechanisms that contribute to specificity of signaling and physiological roles. While insight into the physiological relevance of AC9 has progressed, the understanding of AC9 regulation is muddled with conflicting studies. Currently, modes of AC9 regulation include stimulation by Gαs, protein kinase C βII (PKCβII), or calcium-calmodulin kinase II (CaMKII) and inhibition by Gαi/o, novel PKC isoforms, or calcium-calcineurin. Conversely, the original cloning of human AC9 reported it insensitive to Gαi inhibition. The purpose of our study was to clarify which proposed regulators of AC9 act directly or indirectly, particularly with respect to Gαi/o. The proposed regulators were systematically evaluated, including G-proteins (Gαs, Gαi, Gαo, Gβγ), protein kinases (PKCβII, CaMKII), and forskolin using classic in vitro AC assays and cell-based cAMP accumulation assays in COS-7 cells. Our studies show AC9 is directly regulated by Gαs with weak conditionally activation by forskolin; other modes of proposed regulation occur either indirectly or possibly require additional scaffolding proteins to facilitate regulation. We also show that AC9 contributes to basal cAMP production; knockdown or knockout of endogenous AC9 reduces basal AC activity in COS-7 cells and splenocytes. Importantly, while AC9 is not directly inhibited by Gαi/o, it can heterodimerize with Gαi/o-regulated isoforms, AC5 and AC6.