Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many hormones mediate their intracellular actions by triggering signal transduction pathways that alter the phosphorylation state of key regulatory proteins. Protein phosphorylation is a reversible process involving two classes of signaling enzymes: protein kinases, which catalyze the transfer of phosphate from ATP onto substrate proteins, and phosphoprotein phosphatases, which perform the dephosphorylation step. To insure tight control of hormonally initiated phosphorylation events, the activity of multifunctional kinases and phosphatases is precisely regulated and responds to fluctuations in diffusible second messengers such as Ca2+, phospholipid, and cAMP. Another mechanism that contributes to their regulation is to restrict the location of these enzymes to certain subcellular compartments. Subcellular targeting enhances the selectivity of serine/threonine phosphatases and kinases by favoring their accessibility to certain substrate proteins. Compartmentalization is achieved through a "targeting moiety," which is defined as that part of a phosphatase or kinase that directs the catalytic subunit to a certain subcellular environment. The targeting moiety restricts the location of a phosphatase or kinase through association with a "targeting locus." These are often structural membrane proteins, cytoskeletal components, or cellular organelles. Targeting subunits for the type I phosphatase and protein kinase C have been identified; however, the focus of this chapter centers around a family of anchoring proteins, called AKAPs, that localize the type II cAMP-dependent protein kinase (PKA). Structure-function analysis suggest that each anchoring protein binds to the RII dimer through a conserved amphipathic helix region and is tethered to specific subcellular sites via association of a targeting domain with structural proteins or cellular organelles. Peptides patterned after the amphipathic region have been used to probe the functional significance of PKA anchoring inside cells and have begun to be established by that disruption RII/AKAP interaction in vivo has concomitant effects on certain PKA-mediated phosphorylation events. In addition, multivalent binding proteins such as AKAP79 and AKAP250 have been characterized and appear to serve as platforms for the assembly of kinase/phosphatase signaling complexes. Collectively, these studies suggest that the AKAPs represent a growing family of regulatory proteins that provide a molecular architecture that organizes the intracellular location of a single or multiple multifunctional kinase.
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PMID:Anchoring and scaffold proteins for kinases and phosphatases. 923 61

Signals mediated by G-protein-linked receptors display agonist-induced attenuation and recovery involving both protein kinases and phosphatases. The role of protein kinases and phosphatases in agonist-induced attenuation and recovery of beta-adrenergic receptors was explored by two complementary approaches, antisense RNA suppression and co-immunoprecipitation of target elements. Protein phosphatases 2A and 2B are associated with the unstimulated receptor, the latter displaying a transient decrease followed by a 2-fold increase in the levels of association at 30 min following challenge with agonist. Protein kinase A displays a robust, agonist-induced association with beta-adrenergic receptors over the same period. Suppression of phosphatases 2A and 2B with antisense RNA or inhibition of their activity with calyculin A and FK506, respectively, blocks resensitization following agonist removal. Recycling of receptors to the plasma membrane following agonist-promoted sequestration is severely impaired by loss of either phosphatase 2B or protein kinase C. In addition, loss of protein kinase C diminishes association of phosphatase 2B with beta-adrenergic receptors. Overlay assays performed with the RII subunit of protein kinase A and co-immunoprecipitations reveal proteins of the A kinase-anchoring proteins (AKAP) family, including AKAP250 also known as gravin, associated with the beta-adrenergic receptor. Suppression of gravin expression disrupts recovery from agonist-induced desensitization, confirming the role of gravin in organization of G-protein-linked signaling complexes. The Ht31 peptide, which blocks AKAP protein-protein interactions, blocks association of beta-adrenergic receptors with protein kinase A. These data are the first to reveal dynamic complexes of beta-adrenergic receptors with protein kinases and phosphatases acting via an anchoring protein, gravin.
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PMID:Dynamic complexes of beta2-adrenergic receptors with protein kinases and phosphatases and the role of gravin. 988 May 37

Insulin stimulates a rapid phosphorylation and sequestration of the beta(2)-adrenergic receptor. Analysis of the signaling downstream of the insulin receptor with enzyme inhibitors revealed roles for both phosphatidylinositol 3-kinase and pp60Src. Inhibition of Src with PP2, like the inhibition of phosphatidylinositol 3-kinase with LY294002 [2-(4-morpholynyl)-8-phenyl-4H-1-benzopyran-4-one], blocked the activation of Src as well as insulin-stimulated sequestration of the beta(2)-adrenergic receptor. Depletion of Src with antisense morpholinos also suppressed insulin-stimulated receptor sequestration. Src is shown to be phosphorylated/activated in response to insulin in human epidermoid carcinoma A431 cells as well as in mouse 3T3-L1 adipocytes and their derivative 3T3-F422A cells, well-known models of insulin signaling. Inhibition of Src with PP2 blocks the ability of insulin to sequester beta(2)-adrenergic receptors and the translocation of the GLUT4 glucose transporters. Insulin stimulates Src to associate with the beta(2)-adrenergic receptor/AKAP250/protein kinase A/protein kinase C signaling complex. We report a novel positioning of Src, mediating signals from insulin to phosphatidylinositol 3-kinase and to beta(2)-adrenergic receptor trafficking.
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PMID:pp60Src mediates insulin-stimulated sequestration of the beta(2)-adrenergic receptor: insulin stimulates pp60Src phosphorylation and activation. 1242 37

A-kinase-anchoring protein 250 (AKAP250; gravin) acts as a scaffold that binds protein kinase A (PKA), protein kinase C and protein phosphatases, associating reversibly with the beta(2)-adrenergic receptor. The receptor-binding domain of the scaffold and the regulation of the receptor-scaffold association was revealed through mutagenesis and biochemical analyses. The AKAP domain found in other members of this superfamily is essential for the scaffold-receptor interactions. Gravin constructs lacking the AKAP domain displayed no binding to the receptor. Metabolic labeling studies in vivo demonstrate agonist-stimulated phosphorylation of gravin and enhanced gravin-receptor association. Analysis of the AKAP domain revealed two canonical PKA sites phosphorylated in response to elevated cAMP, blocked by PKA inhibitor, and essential for scaffold-receptor association and for resensitization of the receptor. The AKAP appears to provide the catalytic PKA activity responsible for phosphorylation of the scaffold in response to agonist activation of the receptor as well as for the association of the scaffold with the receptor, a step critical to receptor resensitization.
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PMID:Protein kinase A regulates AKAP250 (gravin) scaffold binding to the beta2-adrenergic receptor. 1465 15

Cell signalling mediated via GPCRs (G-protein-coupled receptors) is a major paradigm in biology, involving the assembly of receptors, G-proteins, effectors and downstream elements into complexes that approach in design 'solid-state' signalling devices. Scaffold molecules, such as the AKAPs (A-kinase anchoring proteins), were discovered more than a decade ago and represent dynamic platforms, enabling multivalent signalling. AKAP79 and AKAP250 were the first to be shown to bind to membrane-embedded GPCRs, orchestrating the interactions of various protein kinases (including tyrosine kinases), protein phosphatases (e.g. calcineurin) and cytoskeletal elements with at least one member of the superfamily of GPCRs, the prototypical beta2-adrenergic receptor. In this review, the multivalent interactions of AKAP250 with the cell membrane, receptor, cytoskeleton and constituent components are detailed, providing a working model for AKAP-based GPCR signalling complexes. Dynamic regulation of the AKAP-receptor complex is mediated by ordered protein phosphorylation.
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PMID:AKAPs (A-kinase anchoring proteins) and molecules that compose their G-protein-coupled receptor signalling complexes. 1471 81

AKAPs (A-kinase anchoring proteins) are members of a diverse family of scaffold proteins that minimally possess a characteristic binding domain for the RI/RII regulatory subunit of protein kinase A and play critical roles in establishing spatial constraints for multivalent signalling assemblies. Especially for G-protein-coupled receptors, the AKAPs provide an organizing centre about which various protein kinases and phosphatases can be assembled to create solid-state signalling devices that can signal, be modulated and trafficked within the cell. The structure of AKAP250 (also known as gravin or AKAP12), based on analyses of milligram quantities of recombinant protein expressed in Escherichia coli, suggests that the AKAP is probably an unordered scaffold, acting as a necklace on which 'jewels' of structure-function (e.g. the RII-binding domain) that provide docking sites on which signalling components can be assembled. Recent results suggest that AKAP250 provides not only a 'tool box' for assembling signalling elements, but may indeed provide a basis for spatial constraint observed for many signalling paradigms. The spatial dimension of the integration of cell signalling will probably reflect many functions performed by members of the AKAP family.
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PMID:AKAP (A-kinase anchoring protein) domains: beads of structure-function on the necklace of G-protein signalling. 1549 34

A-kinase anchoring proteins (AKAPs) define an expanding group of scaffold proteins that display a signature binding site for the RI/RII subunit of protein kinase A. AKAPs are multivalent and a subset of these scaffold proteins also display the ability to associate with the prototypic member of G-protein-coupled receptors, the beta(2)-adrenergic receptor. Both AKAP79 (also known as AKAP5) and AKAP250 (also known as gravin or AKAP12) have been shown to associate with the beta(2)-adrenergic receptor, but each directs downstream signaling events in decidedly different manners. The primary structures, common and unique protein motifs are of interest. Both proteins display largely natively unfolded primary sequences that provide a necklace on which short, structured regions of sequence are found. Membrane association appears to involve both interactions with the lipid bilayer via docking to a G-protein-coupled receptor as well as interactions of short positively charged domains with the inner leaflet of the cell membrane. Gravin, unlike AKAP79, displays a canonical site at its N-terminus that is subject to N-myristoylation. AKAP79 appears to function in switching signaling pathways of the receptor from adenylylcyclase to activation of the mitogen-activated protein kinase cascade. Gravin, in contrast, is essential for the resensitization and recycling of the receptors following agonist-induced activation, desensitization, and internalization. Each AKAP provides a template that enables space-time continuum features to G-protein-coupled signaling pathways as well as a paradigm for explaining apparent compartmentalization of cell signaling.
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PMID:G-Protein-coupled receptor-associated A-kinase anchoring proteins: AKAP79 and AKAP250 (gravin). 1644 64

The spatiotemporal regulation of cAMP can generate microdomains just beneath the plasma membrane where cAMP increases are larger and more dynamic than those seen globally. Real-time measurements of cAMP using mutant cyclic nucleotide-gated ion channel biosensors, pharmacological tools and RNA interference (RNAi) were employed to demonstrate a subplasmalemmal cAMP signaling module in living cells. Transient cAMP increases were observed upon stimulation of HEK293 cells with prostaglandin E1. However, pretreatment with selective inhibitors of type 4 phosphodiesterases (PDE4), protein kinase A (PKA) or PKA/A-kinase anchoring protein (AKAP) interaction blocked an immediate return of subplasmalemmal cAMP to basal levels. Knockdown of specific membrane-associated AKAPs using RNAi identified gravin (AKAP250) as the central organizer of the PDE4 complex. Co-immunoprecipitation confirmed that gravin maintains a signaling complex that includes PKA and PDE4D. We propose that gravin-associated PDE4D isoforms provide a means to rapidly terminate subplasmalemmal cAMP signals with concomitant effects on localized ion channels or enzyme activities.
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PMID:An anchored PKA and PDE4 complex regulates subplasmalemmal cAMP dynamics. 1664 35

Recently we identified a novel target gene of MEF2A named myospryn that encodes a large, muscle-specific, costamere-restricted alpha-actinin binding protein. Myospryn belongs to the tripartite motif (TRIM) superfamily of proteins and was independently identified as a dysbindin-interacting protein. Dysbindin is associated with alpha-dystrobrevin, a component of the dystrophin-glycoprotein complex (DGC) in muscle. Apart from these initial findings little else is known regarding the potential function of myospryn in striated muscle. Here we reveal that myospryn is an anchoring protein for protein kinase A (PKA) (or AKAP) whose closest homolog is AKAP12, also known as gravin/AKAP250/SSeCKS. We demonstrate that myospryn co-localizes with RII alpha, a type II regulatory subunit of PKA, at the peripheral Z-disc/costameric region in striated muscle. Myospryn interacts with RII alpha and this scaffolding function has been evolutionarily conserved as the zebrafish ortholog also interacts with PKA. Moreover, myospryn serves as a substrate for PKA. These findings point to localized PKA signaling at the muscle costamere.
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PMID:Identification and mapping of protein kinase A binding sites in the costameric protein myospryn. 1749 62

Differentiation of human placental mononuclear trophoblasts into a multinucleate syncytium involves up-regulation of key proteins promoting cell fusion and increased capacity for placental hormonogenesis. It is well established that the activation of adenylyl cyclase leads to increased expression of trophoblast fusogenic gene machinery and human chorionic gonadotropin (hCG) secretion. We used the forskolin-induced syncytialisation of BeWo choriocarcinoma cells as a model to characterise in detail the signalling pathway downstream of adenylyl cyclase. Forskolin treatment induced a rapid and potent ERK1/2 and p38MAPK phosphorylation; this cascade required PKA-AKAP interactions and led to downstream CREB-1/ATF-1 phosphorylation via ERK1/2-dependent but p38MAPK-independent mechanisms. Interestingly both p38MAPK and ERK1/2 were involved in forskolin-induced hCG-secretion, suggesting the presence of additional p38MAPK-dependent but CREB-1/ATF-1-independent pathways. Forskolin treatment of BeWo cells significantly up-regulated the expression of various fusogenic gene mRNAs, including syncytin-1 and -2 (by 3- and 10-fold, respectively) the transcription factors old astrocyte specifically induced substance (OASIS) and glial cells missing a (GCMa) (by 3- and 6-fold, respectively) and the syncytin-2 receptor, major facilitator superfamily domain containing 2 (MFSD2) (by 2-fold). Up-regulation of AKAP79 and AKAP250 (by 2.5- and 4-fold, respectively) was also identified in forskolin-treated BeWo cells. Forskolin effects on all these genes were suppressed by chemical inhibition of p38MAPK whereas only specific genes were sensitive to ERK1/2 inhibition. This data provide novel insights into the signalling molecules and mechanisms regulating fusogenic gene expression by the adenylyl cyclase pathway.
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PMID:Interplay of cAMP and MAPK pathways in hCG secretion and fusogenic gene expression in a trophoblast cell line. 2103 20


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