AKAP79 Interacts with Multiple Adenylyl Cyclase (AC) Isoforms and Scaffolds AC5 and -6 to α-Amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) Receptors

Abstract

Spatiotemporal specificity of cAMP action is best explained by targeting protein kinase A (PKA) to its substrates by A-kinase-anchoring proteins (AKAPs). At synapses in the brain, AKAP79/150 incorporates PKA and other regulatory enzymes into signal transduction networks that include ␤-adrenergic receptors, ␣-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA), and N-methyl-D-aspartic acid receptors. We previously showed that AKAP79/150 clusters PKA with type 5 adenylyl cyclase (AC5) to assemble a negative feedback loop in which the anchored kinase phosphorylates AC5 to dynamically suppress cAMP synthesis. We now show that AKAP79 can associate with multiple AC isoforms. The N-terminal regions of AC5, -6, and -9 mediate this protein-protein interaction. Localized activation of PKA 2 triggers a plethora of intracellular signaling processes (1). Precise control of these phosphorylation events is often achieved by restricted activation of PKA in discrete microenvironments. AKAPs participate in this process by tethering the kinase close to preferred substrates. AKAPs now represent a family of 43 diverse but functionally related proteins that bind the regulatory subunit dimer of the PKA holoenzyme (2).AKAPs have been identified in a range of species, tissues, and cellular compartments. The AKAP79/150 group of anchoring proteins is perhaps the best understood member of this class of signal-organizing proteins. AKAP79/150 consists of three orthologs: bovine AKAP75, human AKAP79, and murine AKAP150. Although originally identified in the postsynaptic densities of neurons, this group of anchoring proteins is also expressed in a variety of other tissues. In addition to binding PKA, AKAP79 has the ability to bind protein phosphatase 2B (3) and protein kinase C (PKC) (4, 5). By organizing these signal transduction and signal termination enzymes in the same location, AKAP79 provides a platform to facilitate the bidirectional control of cAMP-and calcium-mediated signaling events.Although anchoring of PKA with its substrates provides an efficient mechanism for the spatial regulation necessary for selectivity of cAMP signaling, it was not clear how local pools of cAMP are managed. We have shown that AC isoforms can specifically interact with three different AKAP complexes, AKAP79, Yotiao, and mAKAP, to regulate events downstream of cAMP production (6 -8). We have also demonstrated that anchoring of AC5 to an AKAP79/150 complex provides negative feedback on AC5 via PKA phosphorylation of AC5 within the complex (6).Although characterization of the AKAP79-AC5 interaction has shed some light on the advantages gained by localizing different components of cAMP signaling pathways, several key issues remain unresolved. First of all, do other AC isoforms interact with AKAP79 or other anchoring proteins? Secondly, are AC isoforms recruited into larger signaling networks via their protein-protein interactions with AKAP79? AKAP79/150 has been shown to form a multiprotein signaling complex with AMPA and NMDA receptors (9 -11), adhesion mol...

A Kinase Anchor Protein 150 (AKAP150)-associated Protein Kinase A Limits Dendritic Spine Density

“…Truncation of the PKA binding site of AKAP150 in D36 mice does not disrupt its overall expression nor its localization to postsynaptic densities (22,23). It leaves intact the identified binding sites for other binding partners including F-actin, calmodulin, PIP 2 , cadherin, adenylyl cyclase, PKC, PSD-95, and PP2B (20,28,30,(47)(48)(49)(50)(51). As the C-terminally deleted AKAP150 still binds PP2B, the phosphorylation status of postsynaptic proteins might be shifted more toward dephosphorylation in D36 than KO mice upon Ca 2ϩ influx, which activates PP2B, with KO but not D36 having lost AKAP150 as a PP2B adaptor (25).…”

“…45,46). The N terminus of AKAP150 also binds F-actin, cadherin, adenylyl cyclases, and PIP 2 and targets AKAP150 to dendritic spines and the central region binds PSD-95 and its homologues (20,(47)(48)(49)(50)(51).Bridging AMPAR, NMDAR, F-actin, PKA, PKC, and PP2B at spines, AKAP150 is an attractive candidate for correlating synaptic activity with spine morphology. We previously generated AKAP150 KO mice and mice that lack the PKA binding site at the C terminus of AKAP150 (D36 mice) (22,25,52).…”

“…45,46). The N terminus of AKAP150 also binds F-actin, cadherin, adenylyl cyclases, and PIP 2 and targets AKAP150 to dendritic spines and the central region binds PSD-95 and its homologues (20,(47)(48)(49)(50)(51).…”

G protein-coupled Receptor 30 (GPR30) Forms a Plasma Membrane Complex with Membrane-associated Guanylate Kinases (MAGUKs) and Protein Kinase A-anchoring Protein 5 (AKAP5) That Constitutively Inhibits cAMP Production

“…The timeframe in which St-Ht31 interrupted the inhibitory coupling suggests that this effect involves proteinprotein interaction and/or covalent modification. AKAP5 is known to directly interact with AC5 and AC6 and scaffold them to AMPA receptors (39), and AKAP5-bound RII causes phosphorylation and inhibition of these enzymes (40). Furthermore, AKAP9/Yotiao directly inhibits AC2 and AC3 (41).…”

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

“…Protein kinase A-anchoring proteins modulate membrane proximal signaling events, principally by tethering protein kinases and phosphatases in the vicinity of G-protein-coupled receptors, ion channels, and adenylyl cyclases (7,25,(51)(52)(53)(54). Taken together, the data in Fig.…”