AKAP79/150 Interacts with AC8 and Regulates Ca2+-dependent cAMP Synthesis in Pancreatic and Neuronal Systems

Abstract

Protein kinase A anchoring proteins (AKAPs) provide the backbone for targeted multimolecular signaling complexes that serve to localize the activities of cAMP. Evidence is accumulating of direct associations between AKAPs and specific adenylyl cyclase (AC) isoforms to facilitate the actions of protein kinase A on cAMP production. It happens that some of the AC isoforms (AC1 and AC5/6) that bind specific AKAPs are regulated by submicromolar shifts in intracellular Ca2+. However, whether AKAPs play a role in the control of AC activity by Ca2+ is unknown. Using a combination of co-immunoprecipitation and high resolution live cell imaging techniques, we reveal an association of the Ca2+-stimulable AC8 with AKAP79/150 that limits the sensitivity of AC8 to intracellular Ca2+ events. This functional interaction between AKAP79/150 and AC8 was observed in HEK293 cells overexpressing the two signaling molecules. Similar findings were made in pancreatic insulin-secreting cells and cultured hippocampal neurons that endogenously express AKAP79/150 and AC8, which suggests important physiological implications for this protein-protein interaction with respect to Ca2+-stimulated cAMP production.

Adenylyl cyclase AC8 directly controls its micro-environment by recruiting the actin cytoskeleton in a cholesterol-rich milieu

“…However, the intricacy of the relationship with the actin cytoskeleton, resulting from the effect of cAMP, is unique to AC8. The nature of the complex involved requires further investigation, and might be cell-type specific, but it potentially involves AKAP79, which binds both AC8 and actin (Willoughby et al, 2010b;Dell'Acqua et al, 2006). Alternatively, actin also binds to ezrin, which interacts with Na + /H + exchanger regulatory factor 1 and 2, which in turn, binds to NHE3 (Cha et al, 2004).…”

“…Organization of the immediate downstream targets of cAMP, namely protein kinase A (PKA), exchange protein activated by cAMP (EPAC) and cyclic nucleotide-gated (CNG) channels, offers an additional level of control. However, recent studies on the binding by adenylyl cyclases (ACs) of various regulatory proteins such as PKA, A-kinase anchoring proteins (AKAPs) (Bauman et al, 2006;Efendiev et al, 2010;Willoughby et al, 2010b), protein phosphatase 2A (PP2A) , snapin (Chou et al, 2004) and phosphodiesterases (PDEs) (Halls and Cooper, 2010) indicate that ACs can to a large extent dictate their micro-environmental milieu. Consequently, the placement and compartmentalization of ACs might provide a primary level of organization of cAMP signalling cascades.…”

A-kinase Anchoring Protein 79/150 Recruits Protein Kinase C to Phosphorylate Roundabout Receptors

“…Previous studies have shown that this segment of the anchoring protein contains three polybasic regions that participate in membrane targeting through interaction with negatively charged phospholipids (29). More recent studies have implicated the palmitoylation of conserved cysteines in the proximal and distal polybasic regions as a means to guide AKAP79/150 to lipid rafts (21,68). These latter findings raise the intriguing possibility that AKAP-Robo2 assemblies might be sequestered in specialized submembrane compartments.…”

A key phosphorylation site in AC8 mediates regulation of Ca2+-dependent cAMP dynamics by an AC8–AKAP79–PKA signalling complex

“…We recently identified a direct interaction between Ca 2+ -sensitive AC8 and plasma membrane-targeted AKAP79/150 (in cultured pancreatic insulin-secreting cells and hippocampal neurons), which attenuated the stimulation of AC8 by Ca 2+ entry (Willoughby et al, 2010). Here, we reveal that AKAP79 recruits cAMP-dependent protein kinase (PKA) to mediate the regulatory effects of AKAP79 on AC8 activity.…”