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

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Item Type:	Article
Title:	A key phosphorylation site in AC8 mediates regulation of Ca2+-dependent cAMP dynamics by an AC8-AKAP79-PKA signalling complex
Creators Name:	Willoughby, D., Halls, M.L., Everett, K.L., Skroblin, P., Klussmann, E. and Cooper, D.M.F.
Abstract:	Adenylyl cyclase (AC) isoforms can participate in multimolecular signalling complexes incorporating A-kinase anchoring proteins (AKAPs). 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. Modulation by PKA is a novel means of AC8 regulation, which may modulate or apply negative feedback to the stimulation of AC8 by Ca(2+) entry. We show that the actions of PKA are not mediated indirectly via PKA-dependent activation of protein phosphatase 2A (PP2A) B56delta subunits that associate with the N-terminus of AC8. By site-directed mutagenesis we identify Ser-112 as an essential residue for direct PKA phosphorylation of AC8 (Ser-112 lies within the N-terminus of AC8, close to the site of AKAP79 association). During a series of experimentally imposed Ca(2+) oscillations, AKAP79-targeted PKA reduced the on-rate of cAMP production in wild-type but not non-phosphorylatable mutants of AC8, which suggests that the protein-protein interaction may provide a feedback mechanism to dampen the downstream consequences of AC8 activation evoked by bursts of Ca(2+) activity. This fine-tuning of Ca(2+)-dependent cAMP dynamics by targeted PKA could be highly significant for cellular events that depend on the interplay of Ca(2+) and cAMP, such as pulsatile hormone secretion and memory formation.
Keywords:	Adenylyl Cyclase, PKA, Phosphorylation, AKAP, Calcium
Source:	Journal of Cell Science
ISSN:	0021-9533
Publisher:	Company of Biologists
Volume:	125
Number:	Pt 23
Page Range:	5850-5859
Date:	1 December 2012
Official Publication:	https://doi.org/10.1242/jcs.111427
PubMed:	View item in PubMed

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