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)

The subcellular location of the type II cAMP-dependent protein kinase is dictated by the interaction of the regulatory subunit (RII) with A-kinase anchor proteins (AKAPs). Using an interaction cloning strategy with RII alpha as a probe, we have isolated cDNAs encoding a novel 761-amino acid protein (named AKAP 95) that contains both RII- and DNA-binding domains. Deletion analysis and peptide studies revealed that the RII-binding domain of AKAP 95 is located between residues 642 and 659 and includes a predicted amphipathic helix. Zinc overlay and DNA binding studies suggest that the DNA-binding domain is composed of two CC/HH-type zinc fingers between residues 464 and 486 and residues 553 and 576. The AKAP was detected in a nuclear matrix fraction, and immunofluorescence using purified anti-AKAP 95 antibodies revealed a distinct nuclear staining in a variety of cell types. Direct overlay of fluorescein isothiocyanate-labeled RII alpha onto fixed rat embryo fibroblasts showed that high-affinity binding sites for RII exist in the nucleus and that these sites are blocked by an anchoring inhibitor peptide. Furthermore, AKAP 95 was detected in preparations of RII that were purified from cellular extracts using cAMP-agarose. The results suggest that AKAP 95 could play a role in targeting type II cAMP-dependent protein kinase for cAMP-responsive nuclear events.
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PMID:Cloning and characterization of AKAP 95, a nuclear protein that associates with the regulatory subunit of type II cAMP-dependent protein kinase. 812 92

Preferential phosphorylation of specific proteins by cAMP-dependent protein kinase (PKA) may be mediated in part by the anchoring of PKA to a family of A-kinase anchor proteins (AKAPs) positioned in close proximity to target proteins. This interaction is thought to depend on binding of the type II regulatory (RII) subunits to AKAPs and is essential for PKA-dependent modulation of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptor, the L-type Ca2+ channel, and the KCa channel. We hypothesized that the targeted disruption of the gene for the ubiquitously expressed RIIalpha subunit would reveal those tissues and signaling events that require anchored PKA. RIIalpha knockout mice appear normal and healthy. In adult skeletal muscle, RIalpha protein levels increased to partially compensate for the loss of RIIalpha. Nonetheless, a reduction in both catalytic (C) subunit protein levels and total kinase activity was observed. Surprisingly, the anchored PKA-dependent potentiation of the L-type Ca2+ channel in RIIalpha knockout skeletal muscle was unchanged compared with wild type although it was more sensitive to inhibitors of PKA-AKAP interactions. The C subunit colocalized with the L-type Ca2+ channel in transverse tubules in wild-type skeletal muscle and retained this localization in knockout muscle. The RIalpha subunit was shown to bind AKAPs, although with a 500-fold lower affinity than the RIIalpha subunit. The potentiation of the L-type Ca2+ channel in RIIalpha knockout mouse skeletal muscle suggests that, despite a lower affinity for AKAP binding, RIalpha is capable of physiologically relevant anchoring interactions.
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PMID:Type II regulatory subunits are not required for the anchoring-dependent modulation of Ca2+ channel activity by cAMP-dependent protein kinase. 938 Jul 60

A-kinase anchor protein 75 (AKAP75) binds regulatory subunits (RIIalpha and RIIbeta) of type II protein kinase A (PKAII) isoforms and targets the resulting complexes to sites in the cytoskeleton that abut the plasma membrane [1-7]. Co-localization of AKAP75-PKAII with adenylate cyclase and PKA substrate/effector proteins in cytoskeleton and plasma membrane effects a physical and functional integration of up-stream and downstream signaling proteins, thereby ensuring efficient propagation of signals carried by locally generated cyclic AMP (cAMP) [4-9]. An important, but previously untested, prediction of the AKAP model is that efficient, cyclic nucleotide-dependent liberation of diffusible PKA catalytic subunits from cytoskeleton-bound AKAP75-PKAII complexes will also enhance signaling to distal organelles, such as the nucleus. We tested this idea by suing HEK-A75 cells, in which PKAII isoforms are immobilized in cortical cytoskeleton by AKAP75. Abilities of HEK-A75 and control cells (with cytoplasmically dispersed PKAII isoforms) to respond to increases in cAMP content were compared. Cells with anchored PKAII exhibited a threefold higher level of nuclear catalytic subunit content and 4-10-fold greater increments in phosphorylation of a regulatory serine residue in cAMP response element binding protein (CREB) and in phosphoCREB-stimulated transcription of the c-fos gene. Each effect occurred more rapidly in cells containing targeted AKAP75-PKAII complexes. Thus, anchoring of PKAII in actin cortical cytoskeleton increases the rate, magnitude and sensitivity of cAMP signaling to the nucleus.
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PMID:A-kinase anchor protein 75 increases the rate and magnitude of cAMP signaling to the nucleus. 938 44

Mammalian sperm motility is regulated by a cascade of cAMP-dependent protein phosphorylation events mediated by protein kinase A. A-kinase anchor proteins (AKAPs) direct protein kinase A activity by tethering the enzyme near its physiological substrates. We have characterized a major human sperm fibrous sheath AKAP, hAKAP82, and its precursor, pro-hAKAP82, the homologues of the mouse fibrous sheath proteins mAKAP82 and pro-mAKAP82. The cDNA sequence of pro-hAKAP82 was highly homologous to the mouse sequence, and the functional domains of the pro-hAKAP82 protein, the protein kinase A binding, and the pro-hAKAP82/hAKAP82 cleavage sites were identical to those of the mouse protein. The genomic organization of mouse pro-AKAP82 was determined. Alternative splicing occurred in both the mouse and human pro-AKAP82 genes that resulted in at least two distinct transcripts and possibly two different proteins. Compared with pro-mAKAP82, considerably less pro-hAKAP82 was processed to hAKAP82 in human sperm. Although pro-mAKAP82 localizes only to the proximal portion of the principal piece of the flagellum, pro-hAKAP82 localized to the entire length of the principal piece. The pro-hAKAP82 gene mapped to human chromosome Xp11.2, indicating that defects in this gene are maternally inherited. These studies suggest several roles for hAKAP82 in sperm motility, including the regulation of signal transduction pathways.
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PMID:An X-linked gene encodes a major human sperm fibrous sheath protein, hAKAP82. Genomic organization, protein kinase A-RII binding, and distribution of the precursor in the sperm tail. 982 90

Sequence analysis of cosmid clones was instrumental to identify three genes in the region flanking the Fugu rubripes NF1 gene in the 3' direction: the AKAP84 gene (A-kinase anchor protein 84), the WSB1 gene (WD-40-repeat protein with a SOCS box) and the BAW gene of yet unknown function located between the AKAP84 and the WSB1 genes. The human homologues of these genes are not located in the immediate vicinity of the NF1 gene at 17q11.2. Although synteny of the NF1, AKAP84, BAW and WSB1 genes is conserved between Fugu and human, the gene order is not conserved, and more than a simple inversion would have been necessary to explain the difference in gene order. The mammalian homologue of the Fugu BAW gene or protein has not yet been characterized. As deduced from the respective cDNAs, the Fugu AKAP84, WSB1 and BAW proteins vary concerning the overall degree of similarity to their mammalian counterparts. Whereas the overall similarity of AKAP84 between Fugu and mouse is low, three regions of known functional importance show considerable conservation. These are the N-terminal anchoring domain mediating the insertion of AKAP84 in the outer mitochondrial membrane, the binding site of the regulatory subunit (RI or RII) of protein kinase A, and the C-terminal domain present in the alternatively spliced isoform AKAP121 with an hnRNP K homology domain involved in RNA binding. A higher overall similarity of deduced protein sequences between Fugu and mouse was observed comparing the BAW gene products (74.1%) and the WSB1 proteins (77.2%).
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PMID:Characterization of three genes, AKAP84, BAW and WSB1, located 3' to the neurofibromatosis type 1 locus in Fugu rubripes. 1041 27

Sperm motility is regulated by the cAMP-dependent protein kinase (protein kinase-A)-mediated phosphorylation of a group of largely unidentified flagellar proteins. Human AKAP82 (hAKAP82) and its precursor protein, pro-hAKAP82, are members of the A-kinase anchor protein (AKAP) family. These proteins tether protein kinase-A to the fibrous sheath of human spermatozoa and presumably localize the activity of the kinase near specific targets in the sperm flagellum. In this way, pro-hAKAP82 and hAKAP82 may be involved in regulating sperm motility. Similar to its homologues in other species, pro-hAKAP82 is proteolytically processed to hAKAP82. However, the amount of processing of pro-hAKAP82 in human spermatozoa is less than the amount of processing of the precursor in other species. We postulated that this lower extent of processing may be related to lower percentages of human sperm motility. In addition, both pro-hAKAP82 and hAKAP82 are tyrosine phosphorylated in a capacitation-dependent manner. Since capacitation is associated with hyperactivated motility, we postulated that tyrosine phosphorylation of pro-hAKAP82/hAKAP82 is associated with changes in motility. However, using a combination of immunofluorescence and immunoblotting approaches, we found no evidence for an association between either processing or tyrosine phosphorylation of pro-hAKAP82/hAKAP82 and significant differences in motility in spermatozoa from normal men.
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PMID:Relationship between sperm motility and the processing and tyrosine phosphorylation of two human sperm fibrous sheath proteins, pro-hAKAP82 and hAKAP82. 1046 Feb 19

cAMP-dependent protein kinase is anchored to discrete cellular compartments by a family of proteins, the A-kinase anchor proteins (AKAPs). We have investigated in vivo and in vitro the biological effects of the expression of a prototypic member of the family, AKAP75, on smooth muscle cells. In vitro expression of AKAP75 in smooth muscle cells stimulated cAMP-induced transcription, increased the levels of the cyclin-dependent kinase-2 inhibitor p27(kip1), and reduced cell proliferation. In vivo expression of exogenous AKAP75 in common carotid arteries, subjected to balloon injury, significantly increased the levels of p27(kip1) and inhibited neointimal hyperplasia. Both the effects in smooth muscle cells in vitro and in carotid arteries in vivo were specifically dependent on the amplification of cAMP-dependent protein kinase (PKA) signals by membrane-bound PKA, as indicated by selective loss of the AKAP75 biological effects in mutants defective in the PKA anchor domain or by suppression of AKAP effects by the PKA-specific protein kinase inhibitor. These data indicate that AKAP proteins selectively amplify cAMP-PKA signaling in vitro and in vivo and suggest a possible target for the inhibition of the neointimal hyperplasia after vascular injury.
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PMID:Membrane-bound protein kinase A inhibits smooth muscle cell proliferation in vitro and in vivo by amplifying cAMP-protein kinase A signals. 1117

A-kinase anchor proteins (AKAPs) target protein kinase A (PKA) to different subcellular locations and are thought to play important roles in the cAMP signaling pathway. The aims of this study were to determine whether T cells express AKAPs and, if so, to establish their physiological significance. CD4(+) T cells were found to express eight AKAPs. Disruption of the AKAP-PKA interaction caused high levels of IL-2, IL-4, IL-5, and IFN-gamma production in the absence of stimulation via CD3epsilon and CD28 molecules. Disruption of the AKAP-PKA interaction acted synergistically with suboptimal doses of Ag in boosting proliferative responses of T cells. Finally, disruption of the AKAP-PKA interaction rendered T cells insensitive to cAMP-elevating agents. It was concluded that AKAPs, through their association with PKA, are involved in maintaining T cell homeostasis and in regulating the sensitivity of T cells to incoming cAMP signals.
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PMID:Cutting edge: A-kinase anchor proteins are involved in maintaining resting T cells in an inactive state. 1202 30

In the mammalian oocyte, the cAMP-dependent protein kinase (PKA) has critical functions in the maintenance of meiotic arrest and oocyte maturation. Because PKA is spatially regulated, its localization was examined in developing oocytes. Both regulatory subunits (RI and RII) and the catalytic subunit (C) of PKA were found in oocytes and metaphase II-arrested eggs. In the oocyte, RI and C were predominantly localized in the cortical region, while RII showed a punctate distribution within the cytoplasm. After maturation to metaphase II, RI remained in the cortex and was also localized to the meiotic spindle, while RII was found adjacent to the spindle. C was diffuse within the cytoplasm of the egg but was enriched in the cytoplasm surrounding the metaphase spindle, much like RII. The polarized localization and redistribution of RI, RII, and C suggested that PKA might be tethered by A-kinase anchor proteins (AKAPs), proteins that tether PKA close to its physiological substrates. An AKAP, AKAP140, was identified that was developmentally regulated and phosphorylated in oocytes and eggs. AKAP140 was shown to be a dual-specific AKAP, having the ability to bind both RI and RII. By compartmentalizing PKA, AKAP140 and/or other AKAPs could spatially regulate PKA activity during oocyte development.
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PMID:A-kinase anchor proteins as potential regulators of protein kinase A function in oocytes. 1219 11

The rat pineal organ is an established model to study signal transduction cascades that are activated by norepinephrine (NE) and cause increases in cAMP levels and stimulation of protein kinase A (PKA). PKA type II catalyzes the phosphorylation of the transcription factor cAMP-response-element-binding protein (CREB) which is essential for the transcriptional induction of the arylalkylamine- N-acetyltransferase (AANAT), the rate limiting enzyme of melatonin biosynthesis. Moreover, PKA may control protein levels and enzyme activity via two PKA-dependent phosphorylation sites in the AANAT molecule. Despite the functional importance of PKA very little is known about the distribution of its isoenzymes and of A-kinase anchor proteins (AKAPs) that target the PKA to specific membrane areas and organelles by binding to the regulatory (R) subunits of PKA. We have addressed this problem by demonstrating the R subunits alpha and beta of PKA type I and II and two AKAPs (150 and 95) in NE-stimulated and untreated rat pinealocytes by immunoblot and immunocytochemistry. The immunoreactions (IR) of all four R subunits were confined to granules evenly distributed in the pinealocyte cytoplasm. Immunoreactions of RIIalpha and RIIbeta were stronger than those of RIalpha and RIbeta. AKAP 150-IR was concentrated at the cell periphery; AKAP 95-IR was restricted to the nucleus. Amount and subcellular distribution of the immunoreactions of all proteins investigated did not change upon NE stimulation. A substantial colocalization was observed between RII-subunits and AKAP 150-IR, suggesting that, in rat pinealocytes, AKAP 150 primarily anchors the R subunits of PKA II.
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PMID:Distribution of regulatory subunits of protein kinase A and A kinase anchor proteins (AKAP 95, 150) in rat pinealocytes. 1245 32


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