| 1304429 | Identification of an IQGAP1/AKAP79 complex in beta-cells. | Nauert JB, etal., J Cell Biochem 2003 Sep 1;90(1):97-108. | IQGAP1, is a recently discovered scaffold protein proposed to regulate membrane cytoskeleton events through protein-protein interactions with F-actin, E-cadherin, beta-catenin, and CLIP170. The binding of IQGAP1 to its partners is regulated by calcium/calmodulin (Ca(++)/CaM) and the small molecular weight guanine nucleotide triphosphatases (GTPases), Cdc42, and Rac1. Here we identify a novel IQGAP1 scaffolding function by isolating the cyclic AMP dependent kinase (PKA) with IQGAP1. IQGAP1 was co-purified with PKA using 5'-cyclic AMP (cAMP) affinity chromatography and PKA activity was co-immunoprecipitated with IQGAP1 using an anti-IQGAP1 antibody. The association of IQGAP1 with PKA was shown to occur through a direct interaction between A kinase anchoring protein 79 (AKAP79) and the carboxyl-terminal domain of IQGAP1. This suggests that cAMP/PKA may be coupled with Ca(++)/CaM and GTPases through an IQGAP1/AKAP79 complex. | 12938160 | 2003-12-01 |
| 2313223 | Contextual utilization of enzymes in discrete AKAP79/150 signalling complexes. | Hoshi N and Scott JD, Eur J Cell Biol. 2006 Jul;85(7):621-2. Epub 2006 Feb 7. | Cellular function involves the concerted action of signal transduction enzymes. Restriction of enzyme location contributes to the fidelity of each cellular response. A kinase-anchoring proteins (AKAPs) target the cAMP-dependent protein kinase and other signalling enzymes to defined subcellular locat ions. We have developed a new strategy that combines RNA interference of the endogenous protein and replacement with AKAP79/150 forms unable to anchor selected binding partners. Using this approach we show that AKAP79/150 coordinates different enzyme combinations to modulate the activity of two distinct neuronal ion channels: AMPA-type glutamate receptors and M-type potassium channels. Utilization of distinct enzyme combinations in this manner provides a means to expand the repertoire of cellular events that the same AKAP modulates. | 16460836 | 2006-09-01 |
| 13507305 | Balanced interactions of calcineurin with AKAP79 regulate Ca2+-calcineurin-NFAT signaling. | Li H, etal., Nat Struct Mol Biol. 2012 Feb 19;19(3):337-45. doi: 10.1038/nsmb.2238. | In hippocampal neurons, the scaffold protein AKAP79 recruits the phosphatase calcineurin to L-type Ca(2+) channels and couples Ca(2+) influx to activation of calcineurin and of its substrate, the transcription factor NFAT. Here we show that an IAIIIT anchoring s ite in human AKAP79 binds the same surface of calcineurin as the PxIxIT recognition peptide of NFAT, albeit more strongly. A modest decrease in calcineurin-AKAP affinity due to an altered anchoring sequence is compatible with NFAT activation, whereas a further decrease impairs activation. Counterintuitively, increasing calcineurin-AKAP affinity increases recruitment of calcineurin to the scaffold but impairs NFAT activation; this is probably due to both slower release of active calcineurin from the scaffold and sequestration of active calcineurin by 'decoy' AKAP sites. We propose that calcineurin-AKAP79 scaffolding promotes NFAT signaling by balancing strong recruitment of calcineurin with its efficient release to communicate with NFAT. | 22343722 | 2012-02-19 |
| 13800547 | A key phosphorylation site in AC8 mediates regulation of Ca(2+)-dependent cAMP dynamics by an AC8-AKAP79-PKA signalling complex. | Willoughby D, etal., J Cell Sci. 2012 Dec 1;125(Pt 23):5850-9. doi: 10.1242/jcs.111427. Epub 2012 Sep 12. | 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) B56d 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. | 22976297 | 2012-12-01 |
| 2313215 | AKAP79-mediated targeting of the cyclic AMP-dependent protein kinase to the beta1-adrenergic receptor promotes recycling and functional resensitization of the receptor. | Gardner LA, etal., J Biol Chem. 2006 Nov 3;281(44):33537-53. Epub 2006 Aug 28. | Resensitization of G protein-coupled receptors (GPCR) following prolonged agonist exposure is critical for restoring the responsiveness of the receptor to subsequent challenges by agonist. The 3'-5' cyclic AMP-dependent protein kinase (PKA) and serine 312 in the third intracellular loop of the human beta(1)-adrenergic receptor (beta(1)-AR) were both necessary for efficient recycling and resensitization of the agonist-internalized beta(1)-AR (Gardner, L. A., Delos Santos, N. M., Matta, S. G., Whitt, M. A., and Bahouth, S. W. (2004) J. Biol. Chem. 279, 21135-21143). Because PKA is compartmentalized near target substrates by interacting with protein kinase A anchoring proteins (AKAPs), the present study was undertaken to identify the AKAP involved in PKA-mediated phosphorylation of the beta(1)-AR and in its recycling and resensitization. Here, we report that Ht-31 peptide-mediated disruption of PKA/AKAP interactions prevented the recycling and functional resensitization of heterologously expressed beta(1)-AR in HEK-293 cells and endogenously expressed beta(1)-AR in SK-N-MC cells and neonatal rat cortical neurons. Whereas several endogenous AKAPs were identified in HEK-293 cells, small interfering RNA-mediated down-regulation of AKAP79 prevented the recycling of the beta(1)-AR in this cell line. Co-immunoprecipitations and fluorescence resonance energy transfer (FRET) microscopy experiments in HEK-293 cells revealed that the beta(1)-AR, AKAP79, and PKA form a ternary complex at the carboxyl terminus of the beta(1)-AR. This complex was involved in PKA-mediated phosphorylation of the third intracellular loop of the beta(1)-AR because disruption of PKA/AKAP interactions or small interfering RNA-mediated down-regulation of AKAP79 both inhibited this response. Thus, AKAP79 provides PKA to phosphorylate the beta(1)-AR and thereby dictate the recycling and resensitization itineraries of the beta(1)-AR. | 16940053 | 2006-09-01 |
| 2313203 | AKAP79/150 anchoring of calcineurin controls neuronal L-type Ca2+ channel activity and nuclear signaling. | Oliveria SF, etal., Neuron. 2007 Jul 19;55(2):261-75. | Neuronal L-type calcium channels contribute to dendritic excitability and activity-dependent changes in gene expression that influence synaptic strength. Phosphorylation-mediated enhancement of L-type channels containing the CaV1.2 pore-forming subunit is promoted by A-kinase anchoring proteins (AKA Ps) that target cAMP-dependent protein kinase (PKA) to the channel. Although PKA increases L-type channel activity in dendrites and dendritic spines, the mechanism of enhancement in neurons remains poorly understood. Here, we show that CaV1.2 interacts directly with AKAP79/150, which binds both PKA and the Ca2+/calmodulin-activated phosphatase calcineurin (CaN). Cotargeting of PKA and CaN by AKAP79/150 confers bidirectional regulation of L-type current amplitude in transfected HEK293 cells and hippocampal neurons. However, anchored CaN dominantly suppresses PKA enhancement of the channel. Additionally, activation of the transcription factor NFATc4 via local Ca2+ influx through L-type channels requires AKAP79/150, suggesting that this signaling complex promotes neuronal L channel signaling to the nucleus through NFATc4. | 17640527 | 2007-09-01 |
| 7242424 | AKAP79/150 interacts with AC8 and regulates Ca2+-dependent cAMP synthesis in pancreatic and neuronal systems. | Willoughby D, etal., J Biol Chem. 2010 Jun 25;285(26):20328-42. doi: 10.1074/jbc.M110.120725. Epub 2010 Apr 21. | 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 prote in 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 Ca(2+). However, whether AKAPs play a role in the control of AC activity by Ca(2+) is unknown. Using a combination of co-immunoprecipitation and high resolution live cell imaging techniques, we reveal an association of the Ca(2+)-stimulable AC8 with AKAP79/150 that limits the sensitivity of AC8 to intracellular Ca(2+) 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 Ca(2+)-stimulated cAMP production. | 20410303 | 2010-04-01 |
| 7349313 | Palmitoylation targets AKAP79 protein to lipid rafts and promotes its regulation of calcium-sensitive adenylyl cyclase type 8. | Delint-Ramirez I, etal., J Biol Chem. 2011 Sep 23;286(38):32962-75. doi: 10.1074/jbc.M111.243899. Epub 2011 Jul 19. | PKA anchoring proteins (AKAPs) optimize the efficiency of cAMP signaling by clustering interacting partners. Recently, AKAP79 has been reported to directly bind to adenylyl cyclase type 8 (AC8) and to regulate its responsiveness to store-operated Ca(2+) entry (S OCE). Although AKAP79 is well targeted to the plasma membrane via phospholipid associations with three N-terminal polybasic regions, recent studies suggest that AKAP79 also has the potential to be palmitoylated, which may specifically allow it to target the lipid rafts where AC8 resides and is regulated by SOCE. In this study, we have addressed the role of palmitoylation of AKAP79 using a combination of pharmacological, mutagenesis, and cell biological approaches. We reveal that AKAP79 is palmitoylated via two cysteines in its N-terminal region. This palmitoylation plays a key role in targeting the AKAP to lipid rafts in HEK-293 cells. Mutation of the two critical cysteines results in exclusion of AKAP79 from lipid rafts and alterations in its membrane diffusion behavior. This is accompanied by a loss of the ability of AKAP79 to regulate SOCE-dependent AC8 activity in intact cells and decreased PKA-dependent phosphorylation of raft proteins, including AC8. We conclude that palmitoylation plays a key role in the targeting and action of AKAP79. This novel property of AKAP79 adds an unexpected regulatory and targeting option for AKAPs, which may be exploited in the cellular context. | 21771783 | 2011-09-01 |
| 11056697 | Phosphorylation state-dependent interaction between AKAP7delta/gamma and phospholamban increases phospholamban phosphorylation. | Rigatti M, etal., Cell Signal. 2015 Sep;27(9):1807-15. doi: 10.1016/j.cellsig.2015.05.016. Epub 2015 May 28. | Changes in heart rate and contractility in response to sympathetic stimulation occur via activation of cAMP dependent protein kinase A (PKA), leading to phosphorylation of numerous substrates that alter Ca(2+) cycling. Phosphorylation of these substrates is coordinated by A-kinase anchoring proteins (AKAPs), which recruit PKA to specific substrates [1]. Phosphorylation of the PKA substrate phospholamban (PLB) is a critical determinant of Ca(2+) re-entry into the sarcoplasmic reticulum and is coordinated by AKAP7delta/gamma [2,3]. Here, we further these findings by showing that phosphorylation of PLB requires interaction with AKAP7delta/gamma and that this interaction occurs only when PLB is unphosphorylated. Additionally, we find that two mutants of PLB (R9C and Delta14), which are associated with dilated cardiomyopathy in humans, prevent association with AKAP7delta/gamma and display reduced phosphorylation in vitro. This finding implicates the AKAP7delta/gamma-PLB interaction in the pathology of the disease phenotype. Further exploration of the AKAP7delta/gamma-PLB association demonstrated a phosphorylation state-dependence of the interaction. Computational modeling revealed that this mode of interaction allows for small amounts of AKAP and PKA (100-200nM) to regulate the phosphorylation of large quantities of PLB (50muM). Our results confirm that AKAP7gamma/delta binding to PLB is important for phosphorylation of PLB, and describe a novel phosphorylation state-dependent binding mechanism that explains how phosphorylation of highly abundant PKA substrates can be regulated by AKAPs present at ~100-200 fold lower concentrations. | 26027516 | 2015-04-01 |
| 2313200 | Proinflammatory mediators modulate the heat-activated ion channel TRPV1 via the scaffolding protein AKAP79/150. | Zhang X, etal., Neuron. 2008 Aug 14;59(3):450-61. | The ability of vertebrates to detect and avoid damaging extremes of temperature depends on activation of ion channels belonging to the thermo-TRP family. Injury or inflammation causes the release of inflammatory mediators which lower the threshold for detection of painful levels of heat, a process k nown as heat hyperalgesia. These inflammatory mediators act by at least three distinct intracellular signaling pathways. Here, we show that modulation of the sensitivity of the heat-activated ion channel TRPV1 by the protein kinases PKA and PKC and by the phosphatase calcineurin depends on the formation of a signaling complex between these enzymes, the scaffolding protein AKAP79/150 and TRPV1. We identify a critical region in the TRPV1 C-terminal which mediates binding of AKAP79/150. If binding is prevented, then sensitization by both bradykinin and PGE(2) is abrogated. AKAP79/150 is therefore a final common element in heat hyperalgesia, on which the effects of multiple proinflammatory mediators converge. | 18701070 | 2008-09-01 |
| 8553331 | Sub-picomolar relaxin signalling by a pre-assembled RXFP1, AKAP79, AC2, beta-arrestin 2, PDE4D3 complex. | Halls ML and Cooper DM, EMBO J. 2010 Aug 18;29(16):2772-87. doi: 10.1038/emboj.2010.168. Epub 2010 Jul 27. | Biochemical studies suggest that G-protein-coupled receptors (GPCRs) achieve exquisite signalling specificity by forming selective complexes, termed signalosomes. Here, using cAMP biosensors in single cells, we uncover a pre-assembled, constitutively active GPCR signalosome, that couples the relaxin receptor, relaxin family peptide receptor 1 (RXFP1), to cAMP following receptor stimulation with sub-picomolar concentrations of peptide. The physiological effects of relaxin, a pleiotropic hormone with therapeutic potential in cancer metastasis and heart failure, are generally attributed to local production of the peptide, that occur in response to sub-micromolar concentrations. The highly sensitive signalosome identified here provides a regulatory mechanism for the extremely low levels of relaxin that circulate. The signalosome includes requisite Galpha(s), Gbetagamma and adenylyl cyclase 2 (AC2); AC2 is functionally coupled to RXFP1 through AKAP79 binding to helix 8 of the receptor; activation of AC2 is tonically opposed by protein kinase A (PKA)-activated PDE4D3, scaffolded through a beta-arrestin 2 interaction with Ser(704) of the receptor C-terminus. This elaborate, pre-assembled, ligand-independent GPCR signalosome represents a new paradigm in GPCR signalling and provides a mechanism for the distal actions of low circulating levels of relaxin. | 20664520 | 2010-05-01 |
| 21201275 | The palmitoyl acyltransferase DHHC2 regulates recycling endosome exocytosis and synaptic potentiation through palmitoylation of AKAP79/150. | Woolfrey KM, etal., J Neurosci. 2015 Jan 14;35(2):442-56. doi: 10.1523/JNEUROSCI.2243-14.2015. | Phosphorylation and dephosphorylation of AMPA-type ionotropic glutamate receptors (AMPARs) by kinases and phosphatases and interactions with scaffold proteins play essential roles in regulating channel biophysical properties and trafficking events that control synaptic strength during NMDA receptor- dependent synaptic plasticity, such as LTP and LTD. We previously demonstrated that palmitoylation of the AMPAR-linked scaffold protein A-kinase anchoring protein (AKAP) 79/150 is required for its targeting to recycling endosomes in dendrites, where it regulates exocytosis from these compartments that is required for LTP-stimulated enlargement of postsynaptic dendritic spines, delivery of AMPARs to the plasma membrane, and maintenance of synaptic potentiation. Here, we report that the recycling endosome-resident palmitoyl acyltransferase DHHC2 interacts with and palmitoylates AKAP79/150 to regulate these plasticity signaling mechanisms. In particular, RNAi-mediated knockdown of DHHC2 expression in rat hippocampal neurons disrupted stimulation of exocytosis from recycling endosomes, enlargement of dendritic spines, AKAP recruitment to spines, and potentiation of AMPAR-mediated synaptic currents that occur during LTP. Importantly, expression of a palmitoylation-independent lipidated AKAP mutant in DHHC2-deficient neurons largely restored normal plasticity regulation. Thus, we conclude that DHHC2-AKAP79/150 signaling is an essential regulator of dendritic recycling endosome exocytosis that controls both structural and functional plasticity at excitatory synapses. | 25589740 | 2015-01-14 |
