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

Protein kinase C (PKC) exhibits both negative and positive cross-talk with multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) in PC12 cells. PKC effects negative cross-talk by inhibiting the mobilization of intracellular Ca2+ stores and by inhibiting Ca2+ influx through voltage-sensitive Ca2+ channels. In the absence of cross-talk, Ca2+ influx induced by depolarization with 56 mM K+ stimulates CaM kinase and its autophosphorylation and converts up to 50% of the enzyme to a Ca(2+)-independent or autonomous species. Acute treatment with phorbol myristate acetate (PMA) elicits a parallel reduction in depolarization-induced Ca2+ influx and in generation of autonomous CaM kinase. Negative cross-talk also occurs during stimulation of the phosphatidylinositol signaling system with bradykinin, which activates both PKC and CaM kinase. The extent of CaM kinase activation is attenuated by the simultaneous activation of PKC; it is enhanced by prior down-regulation of PKC. PKC also exhibits positive cross-talk with CaM kinase. Submaximal activation of CaM kinase by ionomycin is potentiated by concurrent activation of PKC with PMA. Such PMA treatment is found to increase the level of cytosolic calmodulin. Enhanced activation of CaM kinase by PKC may result from PKC-mediated phosphorylation of calmodulin-binding proteins, such as neuromodulin and MARCKS, and the subsequent increase in the availability of previously bound calmodulin for activation of CaM kinase.
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PMID:Cross-talk between protein kinase C and multifunctional Ca2+/calmodulin-dependent protein kinase. 131 12

Calmodulin (CaM) mediates the Ca(2+)-dependent activation of many enzyme systems in accordance with its cellular localization. We have described previously a muscarinic receptor-mediated translocation of CaM from membranes into the cytosol of SK-N-SH human neuroblastoma cells. To explore the potential targets (CaM-binding proteins, CaMBP) for CaM upon translocation, a photoreactive CaM derivative was introduced into living SK-N-SH cells using a scrape-loading technique. Scrape-loading incorporated rhodamine isothiocyanate-labeled CaM with an efficiency of 38%. CaM-diazopyruvamide (CaM-DAP), a Ca(2+)-dependent and CaM-specific probe, was also introduced into the cells. The muscarinic agonist carbachol stimulated a translocation of CaM from membranes into cytosol in CaM-DAP-loaded SK-N-SH cells. Upon photochemical cross-linking, cross-linked adducts of CaM-CaMBP were detected by immunoblotting with anti-CaM antibody. Carbachol stimulated increased photoaffinity labeling of three proteins with relative adduct molecular masses of 70, 120, and 180 kDa. The time course of labeling for the 70- and 120-kDa adducts showed maximal increased by 15-30 min. The 180-kDa adduct displayed a slower time course of maximal labeling, with increases maintained for 2-4 h. Subtracting the molecular mass of CaM, carbachol stimulated binding to CaMBPs of 55, 105, and 163 kDa. Predominant cellular CaMBP were identified using a biotinylated CaM overlay procedure. Western blot analysis indicated the expression of specific CaM-dependent enzymes such as calcineurin, phosphodiesterase, the beta-isoform (rat brain) of CaM kinase II, and Ca(2+)-ATPase. Numerous cytoskeletal CaMBP were expressed such as microtubule-associated protein-2, spectrin, tubulin, caldesmon, adducin, and neuromodulin. Of the CaMBP expressed, phosphodiesterase, calcineurin, caldesmon, and adducin cross-linked with CaM-DAP in the loaded SK-N-SH cells. Carbachol stimulated the time-dependent CaM-DAP labeling of calcineurin and adducin. This study demonstrates the novel incorporation of a photoreactive CaM derivative into living cells, as well as muscarinic receptor-activated CaM-DAP interaction with several cellular CaMBP. We postulate that carbachol-stimulated CaM translocation in SK-N-SH cells may affect the activity of CaM-dependent enzymes and may alter aspects of cytoskeletal function.
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PMID:Carbachol stimulates binding of a photoreactive calmodulin derivative to calmodulin-binding proteins in intact SK-N-SH human neuroblastoma cells. 155 1

Previous findings suggest: (1) that altering protein kinase C (PKC) activity alters the persistence of long-term potentiation (LTP) in the intact hippocampal formation; and (2) that PKC activity is directly correlated with persistence of LTP in vivo as measured by the in vitro phosphorylation of two major PKC substrates in adult hippocampus, protein F1 and 80k. Using quantitative analysis of two-dimensional gels, we report here two additional phosphoproteins of 72 and 55 kDa which were directly correlated to persistence of LTP induced in the intact dorsal hippocampal formation. The phosphorylation of both proteins in response to addition of different kinase stimulators was distinct from that of protein F1 and 80k. Moreover, neither protein was a substrate for exogenous PKC. The physicochemical properties of these phosphoproteins suggest they are identical to the previously described synaptic vesicle proteins IIIa and IIIb, and as such are immunologically indistinguishable. Because proteins IIIa and IIIb are known to be phosphorylated by a Ca2+/calmodulin (CaM)-stimulated kinase, and protein F1 is known to be a plasma membrane-associated protein (P-57) which releases bound CaM in response to phosphorylation by PKC, the present findings suggest a potential mechanism in which PKC-mediated changes in plasma membrane proteins produce CaM kinase-mediated changes in synaptic vesicle proteins through a phosphorylation cascade. These membrane/vesicle alterations are postulated to underlie the increased synaptic efficacy which marks persistent LTP.
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PMID:Phosphoproteins localized to presynaptic terminal linked to persistence of long-term potentiation (LTP): quantitative analysis of two-dimensional gels. 279 Apr 56

The formation of spinules at the terminal dendrites of retinal horizontal cells with the onset of light and their subsequent retraction during darkness is a remarkable example of synaptic plasticity where sensory experience modifies reversibly, and on a time scale of minutes the ultrastructure of synaptic connectivity. The signals and the subsequent intracellular cascades underlying the prominent morphological alterations are only partially understood. We show here that lowering the external calcium concentration did prevent dark- and AMPA-induced retraction of spinules in a eyecup preparation. Furthermore, spinule retraction was prevented in vivo by the injection of calmidazolium, an inhibitor of calmodulin, into the eyeball, and also by the injection of KN-62, an inhibitor of Ca2+/calmodulin-dependent protein kinase (CaMkII). We conclude that local Ca2+ influx through AMPA-gated channels followed by activation of CaMkII is an important step for spinule retraction during dark adaptation. The phosphorylation patterns of phosphoproteins derived from purified horizontal cells was affected by the inhibitors of calmodulin and CaMkII respectively. Some of the affected phosphoproteins appeared to be cytoskeleton-associated proteins, including GAP-43. Based on these observations, a putative scenario for the retraction of spinules is proposed.
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PMID:Retraction of spinule-type neurites from carp retinal horizontal cell dendrites during dark adaptation involves the activation of Ca2+/calmodulin-dependent protein kinase II. 852 66

The nervous tissue-specific protein B-50 (GAP-43), which has been implicated in the regulation of neurotransmitter release, is a member of a family of atypical calmodulin-binding proteins. To investigate to what extent calmodulin and the interaction between B-50 and calmodulin are involved in the mechanism of Ca(2+)-induced noradrenaline release, we introduced polyclonal anti-calmodulin antibodies, calmodulin, and the calmodulin antagonists trifluoperazine, W-7, calmidazolium, and polymyxin B into streptolysin-O-permeated synaptosomes prepared from rat cerebral cortex. Anti-calmodulin antibodies, which inhibited Ca2+/calmodulin-dependent protein kinase II autophosphorylation and calcineurin phosphatase activity, decreased Ca(2+)-induced nor-adrenaline release from permeated synaptosomes. Exogenous calmodulin failed to modulate release, indicating that if calmodulin is required for vesicle fusion it is still present in sufficient amounts in permeated synaptosomes. Although trifluoperazine, W-7, and calmidazolium inhibited Ca(2+)-induced release, they also strongly increased basal release. Polymyxin B potently inhibited Ca(2+)-induced noradrenaline release without affecting basal release. It is interesting that polymyxin B was also the only antagonist affecting the interaction between B-50 and calmodulin, thus lending further support to the hypothesis that B-50 serves as a local Ca(2+)-sensitive calmodulin store underneath the plasma membrane in the mechanism of neurotransmitter release. We conclude that calmodulin plays an important role in vesicular noradrenaline release, probably by activating Ca2+/calmodulin-dependent enzymes involved in the regulation of one or more steps in the release mechanism.
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PMID:Evidence for a role of calmodulin in calcium-induced noradrenaline release from permeated synaptosomes: effects of calmodulin antibodies and antagonists. 878 20

The aim of the present study was to characterize the second messenger activated protein kinase and phosphatase systems in chick ciliary ganglion using biochemical and immunochemical techniques. Using synthetic peptide substrates cyclic-AMP-, cyclic-GMP-, Ca2+/calmodulin- and Ca2+/phospholipid-dependent protein kinase activities were detected in homogenates of ciliary ganglion dissected from 15-16-day-old embryos. Autophosphorylation of the alpha and beta subunits of Ca2+/calmodulin-dependent protein kinase II in the presence of Ca2+/calmodulin or 5 mM ZnSO4 was detected by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and autoradiography. Protein kinase C was shown to be present using a monoclonal antibody. Two cyclic-AMP binding proteins whose molecular weights corresponded to the regulatory subunits of cyclic AMP-dependent protein kinase (RI and RII) were detected in ciliary ganglia using 8-azido-cyclic-AMP. The most heavily labelled band following incubation with [gamma-32P]ATP under most conditions had an apparent molecular weight of 65,000 which corresponds to the chicken form of myristoylated alanine-rich C kinase substrate, a known substrate of protein kinase C. Another substrate for protein kinase C was a 45,000 molecular weight protein which was tentatively identified as neuromodulin (B-50/GAP-43). Although no endogenous substrate proteins for cyclic-GMP-dependent protein kinase were detected, protein kinase A strongly labelled a 40,000 molecular weight protein. Using 32P(i)-labelled glycogen phosphorylase, protein phosphatases 1 and 2A were identified in ciliary ganglia homogenates at levels which were indistinguishable from forebrain at the same age. The major endogenous protein substrates in ciliary ganglion homogenates from 15-16-day-old embryos were also labelled to a similar extent in homogenates of ciliary ganglia from newly hatched chickens. Intact ciliary ganglia remained viable for several hours after dissection and, after incubation with 32P(i), responded to phorbol ester stimulation by an increased endogenous phosphorylation of several proteins, but especially myristoylated alanine-rich C kinase substrate. These results represent the first systematic characterization of the protein phosphorylation systems in chicken ciliary ganglion and provide a basis for future studies on the biochemical mechanisms responsible for regulating synaptic transmission in this tissue.
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PMID:Characterization of protein kinase and phosphatase systems in chick ciliary ganglion. 884 61

Amphetamine is taken up through the dopamine transporter in nerve terminals and enhances the release of dopamine. We previously found that incubation of rat striatal synaptosomes increases phosphorylation of the presynaptic neural-specific protein, neuromodulin (Gnegy et al., Mol. Brain Res. 20:289-293, 1993). Using a state-specific antibody, we now demonstrate that incubation of rat striatal synaptosomes with amphetamine increases levels of neuromodulin phosphorylated at ser41, the protein kinase C substrate site. Phosphorylation was maximal at 5 min at 37 degrees C at concentrations from 100 nM to 10 microM amphetamine. The effect of amphetamine on the phosphorylation of synapsin I at a site specifically phosphorylated by Ca2+/calmodulin-dependent protein kinase II (site 3), was examined using a state-specific antibody for site 3-phosphosynapsin I. Incubation with concentrations of amphetamine from 1 to 100 nM increased the level of site 3-phospho-synapsin I at times from 30 sec to 2 min. The effect of amphetamine on synapsin I phosphorylation was blocked by nomifensine. The presence of calcium in the incubating buffer was required for amphetamine to increase the level of site 3-phospho-synapsin I. The amphetamine-mediated increase in the content of phosphoser41-neuromodulin was less sensitive to extrasynaptosomal calcium. The amphetamine-mediated increase in the content of site 3-phospho-synapsin I persisted in the presence of 10 microM okadaic acid and was not significantly altered by D1 or D2 dopamine receptor antagonists. Preincubation of striatal synaptosomes with 10 microM of the protein kinase C inhibitor, Ro-31-8220, blocked the amphetamine-mediated increases in the levels of both phosphoser41-neuromodulin and site 3-phospho-synapsin I. Our results demonstrate that amphetamine can alter phosphorylation-related second messenger activities in the synaptosome.
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PMID:Amphetamine increases the phosphorylation of neuromodulin and synapsin I in rat striatal synaptosomes. 918 17

In this review, we attempt to cover the descriptive, biochemical and molecular biological work that has contributed to our current knowledge about RC3/neurogranin function and its role in dendritic spine development, long-term potentiation, long-term depression, learning, and memory. Based on the data reviewed here, we propose that RC3, GAP-43, and the small cerebellum-enriched peptide, PEP-19, belong to a protein family that we have named the calpacitins. Membership in this family is based on sequence homology and, we believe, a common biochemical function. We propose a model wherein RC3 and GAP-43 regulate calmodulin availability in dendritic spines and axons, respectively, and calmodulin regulates their ability to amplify the mobilization of Ca2+ in response to metabotropic glutamate receptor stimulation. PEP-19 may serve a similar function in the cerebellum, although biochemical characterization of this molecule has lagged behind that of RC3 and GAP-43. We suggest that these molecules release CaM rapidly in response to large influxes of Ca2+ and slowly in response to small increases. This nonlinear response is analogous to the behavior of a capacitor, hence the name calpacitin. Since CaM regulates the ability of RC3 to amplify the effects of metabotropic glutamate receptor agonists, this activity must, necessarily, exhibit nonlinear kinetics as well. The capacitance of the system is regulated by phosphorylation by protein kinase C, which abrogates interactions between calmodulin and RC3 or GAP-43. We further propose that the ratio of phosphorylated to unphosphorylated RC3 determines the sliding LTP/LTD threshold in concept with Ca2+/ calmodulin-dependent kinase II. Finally, we suggest that the close association between RC3 and a subset of mitochondria serves to couple energy production with the synthetic events that accompany dendritic spine development and remodeling.
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PMID:RC3/neurogranin, a postsynaptic calpacitin for setting the response threshold to calcium influxes. 939 8

Repeated, intermittent treatment of rats with amphetamine followed by a withdrawal period leads to an enhancement in amphetamine-induced dopamine release. We previously reported an increased stoichiometry of site 3-phospho-synapsin I and increased levels of phospho-Ser41-neuromodulin in striatum after repeated amphetamine. In this study, we examined whether the enhanced amphetamine-induced dopamine release and increased levels of these phosphoproteins would be detected in synaptosomes from rats pretreated and withdrawn from repeated amphetamine. Enhanced amphetamine-induced dopamine release was detected in striatal synaptosomes from rats treated with repeated amphetamine compared with controls. The enhanced dopamine release was Ca++ dependent. State-specific antibodies were used to measure the levels of site 3-phospho-synapsin I, phosphorylated by CaM kinase II, and phospho-Ser41-neuromodulin, phosphorylated by protein kinase C, in incubated striatal S1 fractions and synaptosomes. The levels of site 3-phospho-synapsin I and phospho-Ser41-neuromodulin were increased by 40% and 30%, respectively, in amphetamine-pretreated rats compared with controls. Total neuromodulin and synapsin I was not altered. There was a significant 26% increase in CaM kinase II activity in the synaptosomes from amphetamine-pretreated rats but no change in content. No change in protein kinase C activity or content of the alpha-isozyme was detected after repeated amphetamine. Our results demonstrate that the enhanced amphetamine-induced dopamine release and occurring after repeated amphetamine can be detected in synaptosome preparations. Repeated amphetamine leads to alterations in phosphorylation/dephosphorylation activities that can be detected in the incubated synaptosomes. Because the enhanced amphetamine-induced dopamine release after repeated amphetamine appears to be Ca++ sensitive, it is possible that the altered phosphorylation systems, and perhaps site 3-phospho-synapsin I and phospho-Ser41-neuromodulin, play a role in the enhanced dopamine release.
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PMID:Enhanced dopamine release and phosphorylation of synapsin I and neuromodulin in striatal synaptosomes after repeated amphetamine. 940 20

Synaptic plasticity in CA1 hippocampal neurons depends on Ca2+ elevation and the resulting activation of calmodulin-dependent enzymes. Induction of long-term depression (LTD) depends on calcineurin, whereas long-term potentiation (LTP) depends on Ca2+/calmodulin-dependent protein kinase II (CaMKII). The concentration of calmodulin in neurons is considerably less than the total concentration of the apocalmodulin-binding proteins neurogranin and GAP-43, resulting in a low level of free calmodulin in the resting state. Neurogranin is highly concentrated in dendritic spines. To elucidate the role of neurogranin in synaptic plasticity, we constructed a computational model with emphasis on the interaction of calmodulin with neurogranin, calcineurin, and CaMKII. The model shows how the Ca2+ transients that occur during LTD or LTP induction affect calmodulin and how the resulting activation of calcineurin and CaMKII affects AMPA receptor-mediated transmission. In the model, knockout of neurogranin strongly diminishes the LTP induced by a single 100 Hz, 1 s tetanus and slightly enhances LTD, in accord with experimental data. Our simulations show that exchange of calmodulin between a spine and its parent dendrite is limited. Therefore, inducing LTP with a short tetanus requires calmodulin stored in spines in the form of rapidly dissociating calmodulin-neurogranin complexes.
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PMID:Role of the neurogranin concentrated in spines in the induction of long-term potentiation. 1683 80


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