Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.17 (CaMKII)
 4,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purified P400 protein was phosphorylated by both purified Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) and the catalytic subunit of cyclic AMP-dependent protein kinase (A-kinase). Because P400 protein was suggested to function as an integral membrane protein, we investigated the phosphorylation of P400 protein using crude mitochondrial and microsomal fractions (P2/P3 fraction). Incubation of the P2/P3 fraction from mouse cerebellum with cyclic AMP or the catalytic subunit of A-kinase stimulated the phosphorylation of P400 protein. The phosphorylation of P400 protein was not observed in the P2/P3 fraction from mouse forebrain. Cyclic AMP and A-kinase enhanced the phosphorylation of several proteins, including P400 protein, suggesting that P400 protein is one of the best substrates for A-kinase in the P2/P3 fraction. Although endogenous and exogenous CaM kinase II stimulated the phosphorylation of some proteins in the P2/P3 fraction, the phosphorylation of P400 protein was weak. Immunoprecipitation with the monoclonal antibody to P400 protein confirmed that the P400 protein itself was definitely phosphorylated by the catalytic subunit of A-kinase and CaM kinase II. A-kinase phosphorylated only the seryl residue in P400 protein. Immunoblot analysis of the cells in primary culture of mouse cerebellum confirmed the expression of P400 protein, which migrated at the same position on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as that in the P2/P3 fraction. Incubation of the cultured cerebellar cells with [32P]orthophosphate resulted in the labeling of P400 protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphorylation of P400 protein by cyclic AMP-dependent protein kinase and Ca2+/calmodulin-dependent protein kinase II. 254 6

Synapsin I, a major neuron-specific substrate for cAMP-dependent and Ca2+/calmodulin-dependent protein kinases, associates in in vitro assays with brain integral membrane protein site(s) distinct from secretory vesicles and with the neurofilament Mr = 68,000 subunit. The membrane sites for synapsin involve protein(s) and are likely to have physiological relevance since the binding of 125I-labeled synapsin is abolished by digestion with chymotrypsin, is displaced by unlabeled synapsin, is of high affinity (KD = 10 nM), and has a capacity (42 pmol/mg membrane protein) that is comparable to the amount of synapsin in brain, optimal binding occurs at physiological pH (6.8-7.2) and salt concentrations (50 mM), and synapsin binding to membranes is inhibited by phosphorylation with Ca2+/calmodulin-dependent protein kinase. The brain membrane protein sites for synapsin are not due to synaptic vesicles, since synaptic vesicles do not sediment under the conditions of the binding assay. Association between synapsin and the Mr = 68,000 neurofilament subunit has also been demonstrated. The binding of synapsin with the neurofilament subunit is specific since this binding interaction is saturable, with a 1:1 stoichiometry, the binding involves only certain proteolytically derived domains of synapsin, and is therefore not a simple electrostatic interaction between the basic domains of synapsin and the acidic regions in the neurofilament subunit, and Ca2+/calmodulin-dependent phosphorylation of synapsin inhibits this interaction. Synapsin promotes cross-linking of synaptic vesicles to brain membranes, and these complexes are reduced by phosphorylation of synapsin. This interconnecting function of synapsin may be a general characteristic of synapsin binding, with a membrane (synaptic vesicle or nonsecretory vesicle)-bound synapsin associating with microtubules, neurofilaments, or spectrin.
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PMID:Nearest neighbor analysis for brain synapsin I. Evidence from in vitro reassociation assays for association with membrane protein(s) and the Mr = 68,000 neurofilament subunit. 310 May 21

VAMP/synaptobrevin (SYB), an integral membrane protein of small synaptic vesicles, is specifically cleaved by tetanus neurotoxin and botulinum neurotoxins B, D, F, and G is thought to play an important role in the docking and/or fusion of synaptic vesicles with the presynaptic membrane. Potential phosphorylation sites for various kinases are present in SYB sequence. We have studied whether SYB is a substrate for protein kinases that are present in nerve terminals and known to modulate neurotransmitter release. SYB can be phosphorylated within the same vesicle by endogenous Ca2+/calmodulin-dependent protein kinase II (CaMKII) associated with synaptic vesicles. This phosphorylation reaction occurs rapidly and involves serine and threonine residues in the cytoplasmic region of SYB. Similarly to CaMKII, a casein kinase II (CasKII) activity copurifying with synaptic vesicles is able to phosphorylate SYB selectively on serine residues of the cytoplasmic region. This phosphorylation reaction is markedly stimulated by sphingosine, a sphingolipid known to activate CasKII and to inhibit CaMKII and protein kinase C. The results show that SYB is a potential substrate for protein kinases involved in the regulation of neurotransmitter release and open the possibility that phosphorylation of SYB plays a role in modulating the molecular interactions between synaptic vesicles and the presynaptic membrane.
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PMID:Phosphorylation of VAMP/synaptobrevin in synaptic vesicles by endogenous protein kinases. 756 69

The phosphorylation of synaptophysin, a major integral membrane protein of small synaptic vesicles, was found to be regulated in a Ca(2+)-dependent manner in rat cerebrocortical slices, synaptosome preparations, and highly purified synaptic vesicles isolated from rat forebrain. K(+)-induced depolarization of slices and synaptosomes prelabeled with 32P-orthophosphate produced a rapid, transient increase in serine phosphorylation of synaptophysin. In synaptosomes, the depolarization-dependent increase in synaptophysin phosphorylation required the presence of external Ca2+ in the incubation medium. The addition of Ca2+ plus calmodulin to purified synaptic vesicles resulted in a 4-fold increase in serine phosphorylation of synaptophysin, and this phosphorylation was antagonized by a peptide inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II(. Purified rat forebrain CaM kinase II phosphorylated both purified synaptophysin and endogenous, vesicle-associated synaptophysin, and the resulting 2-dimensional chymotryptic phosphopeptide maps were similar to those derived from synaptophysin phosphorylated in cerebrocortical slices. These data demonstrate that Ca(2+)-dependent phosphorylation of synaptophysin, mediated by CaM kinase II, occurs under physiological conditions.
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PMID:Calcium-dependent serine phosphorylation of synaptophysin. 838 57

Phogrin, a 60/64 kDa integral membrane protein localized to dense-core secretory granules of neuroendocrine cells, was found to be reversibly phosphorylated in intact pancreatic beta-cells. Phosphorylation occurred in response to a variety of secretory stimuli, including glucose and depolarizing concentrations of K(+). In MIN6 cells, the glucose dose-response and time course of phogrin phosphorylation paralleled that of insulin secretion. Like secretion, glucose- or K(+)-stimulated phosphorylation required the presence of Ca(2+). The calmodulin antagonist W-7 and the Ca(2+)/calmodulin-dependent kinase II inhibitor KN-93 dose-dependently inhibited both phosphorylation and secretion, while the 'inactive' analogue KN-92 was effective only at significantly higher concentrations. Phosphorylation of phogrin was also stimulated in cells exposed to forskolin, an effect presumably mediated by protein kinase A (cAMP-dependent protein kinase). Under these conditions, phogrin phosphorylation could be dissociated from the secretory response. In MIN6 cells, as in pancreatic islets, cAMP potentiates rather than initiates insulin release. Thus our observations are consistent with a role for phogrin phosphorylation in the signal-transduction pathway at a site proximal to the exocytic event itself, possibly regulating secretory-granule mobilization and recruitment to the exocytic site.
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PMID:Secretagogue-dependent phosphorylation of phogrin, an insulin granule membrane protein tyrosine phosphatase homologue. 1041 18

Phospholamban is a small integral membrane protein of cardiac, smooth, and slow-twitch skeletal muscle sarcoplasmic reticulum that interacts with the Ca2+ pump of these organelles and inhibits Ca(2+)-pump activity while in the dephosphorylated form. Three sites of Ser/Thr phosphorylation have been identified in the primary sequence of phospholamban, at Ser-10, Ser-16, and Thr-17. In vitro studies indicate that these residues are phosphorylated by PKC (Ser-10), PKA, PKG or PKC (Ser-16), and CaM kinase II (Thr-17). Phosphorylation of Ser-16 (or Thr-17) is accompanied by an increase in Ca2+ pump activity in direct proportion to the stoichiometry of phosphorylation. Dual phosphorylation of both Ser-16 and Thr-17 does not cause any further stimulation of pump function over that achieved by stoichiometric phosphorylation of a single site. Examination of the pattern of phosphorylation in vivo has been aided by the generation of polyclonal antibodies specific for the phosphorylated forms of phospholamban. beta-Adrenergic stimulation of cardiac muscle results in phosphorylation of both Ser-16 and Thr-17. The time course of Ser-16 phosphorylation precedes Thr-17. The spatial distribution of Ser-16 and Thr-17 phosphorylated forms of phospholamban is not identical; phospholamban located in the nuclear membrane of a cardiac myocyte is phosphorylated exclusively on Ser-16, whereas phospholamban molecules in the SR membrane of the same cell are phosphorylated on Ser-16 and/or Thr-17. Finally, we have identified a novel stimulus for the phosphorylation of phospholamban. Ca2+ store depletion, achieved by exposure of myocytes to SERCA inhibitors, prompts the phosphorylation of phospholamban on Ser-16. This would be expected to increase Ca2+ uptake by the SR in an attempt to achieve the refilling of the SR.
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PMID:Phosphorylation states of phospholamban. 1060 38