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)

The 14-3-3 proteins are a family of acidic proteins found mainly in the brain and are suggested to have a role in monoamine synthesis based on their ability to activate tyrosine and tryptophan hydroxylases in the presence of type II Ca2+/calmodulin-dependent protein kinase. Recently, however, it has been demonstrated that a member of the 14-3-3 family, termed Exo1, stimulates Ca(2+)-dependent exocytosis in permeabilized adrenal chromaffin cells, suggesting that this protein family may influence the protein kinase C-mediated control of Ca(2+)-dependent exocytosis. Here we show that the 14-3-3 proteins activate protein kinase C at about 2-fold more than the known level of the activated protein kinase, i.e. the activity of protein kinase C in the presence of Ca2+ and phospholipids. This raises the possibility that the cellular activity of protein kinase C is regulated by diverse members of the 14-3-3 family and that the reported ability of Exo1 to reactivate Ca(2+)-dependent exocytosis is based on its stimulatory effect on protein kinase C activity. The 14-3-3 family, therefore, appears to be a multifunctional regulator of cell signalling processes mediated by two types of Ca(2+)-dependent protein kinase, protein kinase C and type II calmodulin-dependent protein kinase.
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PMID:Activation of protein kinase C by the 14-3-3 proteins homologous with Exo1 protein that stimulates calcium-dependent exocytosis. 149 18

Tyrosine and tryptophan hydroxylases are the key enzymes in the regulation of catecholamine and serotonin levels in neurons and other endocrine cells. Among the mechanisms proposed for the modulation of activity, phosphorylation of the enzyme is believed to be of functional significance with respect to the stimulus-response coupling, but the precise mechanism is unknown. Here, we show the existence of multiple, distinct forms of the 14-3-3 activator protein, a neuronal protein essential for activation of tyrosine and tryptophan hydroxylases by Ca2+/calmodulin-dependent protein kinase type II. Bovine brain 14-3-3 protein was resolved by reversed-phase chromatography into seven polypeptides (alpha to eta), all of which were active towards tryptophan hydroxylase when the renatured preparations were assayed in the presence of Ca2+, calmodulin and the protein kinase. Determination of the amino acid sequences of the beta and gamma chains and comparison of the sequences with the previously determined sequence of the eta chain revealed that these molecules are highly homologous, and share a common structural feature in containing an extremely acidic C-terminal region predicted as a domain for interaction with the phosphorylated hydroxylases. Northern blot analysis indicated that the beta, gamma and eta chain are expressed abundantly in the brain; however, these polypeptides appear to be expressed with different tissue specificities because gamma mRNA is found only in the brain, while lower levels of beta and eta mRNAs are detected in several other tissues. These findings suggest the involvement of a diverse family of the activator protein in the stimulus-coupled, Ca2(+)-dependent regulation of monoamine biosynthesis.
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PMID:Distinct forms of the protein kinase-dependent activator of tyrosine and tryptophan hydroxylases. 167 Nov 2

Retinal cytosolic Ca2+/calmodulin-dependent protein kinase II (CaM KII) was isolated from hatched 6-wk chicken retinae by ultracentrifugation and affinity chromatography using calmodulin (CaM) and anti-CaM KII-alpha columns. Samples from different fractions were examined with SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining or immunoblotting. Comparisons were made between the final antibody affinity eluates from retina and forebrain. Silver-stained gels showed that multiple proteins were present in the antibody affinity eluates from retina, including major proteins of 178, 56, and 45 kDa and several minor proteins. Immunoblots revealed that CaM KII-alpha was present in eluates from the retina and forebrain. CaM KII-beta was present in the antibody eluate from forebrain but not retina. The latter subunit was present in the crude homogenates of the retina. Regarding the antibody eluate from retina, the possibility that the major 56 kDa protein was tubulin was ruled out, but protein tau (tau) and synapsin I were present. The presence of multiple proteins in the antibody affinity eluate indicates that these proteins were coisolated in a CaM KII-alpha-associated protein complex. The finding that protein tau and synapsin I are associated with retinal CaM KII provides further insight into the mechanisms underlying the function of the kinase in this tissue. The lack of cytosolic CaM KII-beta subunit in the antibody affinity eluate from retina is indicative of a brain region-specificity in subunit composition of the kinase.
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PMID:The Ca2+/calmodulin-dependent protein kinase II-associated protein complex isolated from chicken retina. 883 78

The protection against apoptosis provided by growth factors in several cell lines is due to stimulation of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway, which results in activation of protein kinase B (PKB; also known as c-Akt and Rac) and phosphorylation and sequestration to protein 14-3-3 of the proapoptotic Bcl-2-family member BAD. A modest increase in intracellular Ca2+ concentration also promotes survival of some cultured neurons through a pathway that requires calmodulin but is independent of PI(3)K and the MAP kinases. Here we report that Ca2+/calmodulin-dependent protein kinase kinase (CaM-KK) activates PKB directly, resulting in phosphorylation of BAD on serine residue 136 and the interaction of BAD with protein 14-3-3. Serum withdrawal induced a three- to fourfold increase in cell death of NG108 neuroblastoma cells, and this apoptosis was largely blocked by increasing the intracellular Ca2+ concentration with NMDA (N-methyl-D-aspartate) or KCl or by transfection with constitutively active CaM-KK. The effect of NMDA on cell survival was blocked by transfection with dominant-negative forms of CaM-KK or PKB. These results identify a Ca2+-triggered signalling cascade in which CaM-KK activates PKB, which in turn phosphorylates BAD and protects cells from apoptosis.
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PMID:Calcium promotes cell survival through CaM-K kinase activation of the protein-kinase-B pathway. 985 94

Slob is a novel protein that binds to the carboxy-terminal domain of the Drosophila Slowpoke (dSlo) calcium-dependent potassium (K(Ca)) channel. A yeast two-hybrid screen with Slob as bait identifies the zeta isoform of 14-3-3 as a Slob-binding protein. Coimmunoprecipitation experiments from Drosophila heads and transfected cells confirm that 14-3-3 interacts with dSlo via Slob. All three proteins are colocalized presynaptically at Drosophila neuromuscular junctions. Two serine residues in Slob are required for 14-3-3 binding, and the binding is dynamically regulated in Drosophila by calcium/calmodulin-dependent kinase II (CaMKII) phosphorylation. 14-3-3 coexpression dramatically alters dSlo channel properties when wild-type Slob is present but not when a double serine mutant Slob that is incapable of binding 14-3-3 is present. The results provide evidence for a dSlo/Slob/14-3-3 regulatory protein complex.
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PMID:A dynamically regulated 14-3-3, Slob, and Slowpoke potassium channel complex in Drosophila presynaptic nerve terminals. 1023 Aug

The first step in the biosynthesis of melatonin in the pineal gland is the hydroxylation of tryptophan to 5-hydroxytryptophan. A cDNA of human tryptophan hydroxylase (TPH) was cloned from a library of human pineal gland and expressed in Escherichia coli. This cDNA sequence is identical to the cDNA sequence published from the human carcinoid tissue [1]. This human pineal hydroxylase gene encodes a protein of 444 amino acids and a molecular mass of 51 kDa estimated for the purified enzyme. Tryptophan hydroxylase from human brainstem exhibits high sequence homology (93% identity) with the human pineal hydroxylase. The recombinant tryptophan hydroxylase exists in solution as tetramers. The expressed human pineal tryptophan hydroxylase has a specific activity of 600 nmol/min/mg when measured in the presence of tetrahydrobiopterin and L-tryptophan. The enzyme catalyzes the hydroxylation of tryptophan and phenylalanine at comparable rates. Phosphorylation of the hydroxylase by protein kinase A or calmodulin-dependent kinase II results in the incorporation of 1 mol of phosphate/mol of subunit, but this degree of phosphorylation leads to only a modest (30%) increase in BH(4)-dependent activity when assayed in the presence of 14-3-3. Rapid scanning ultraviolet spectroscopy has revealed the formation of the transient intermediate compound, 4alpha-hydroxytetrahydrobiopterin, during the hydroxylation of either tryptophan or phenylalanine catalyzed by the recombinant pineal TPH.
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PMID:Cloning and expression of recombinant human pineal tryptophan hydroxylase in Escherichia coli: purification and characterization of the cloned enzyme. 1052 50

Tyrosine hydroxylase (TH) is phosphorylated by CaM kinase II and is activated in situ in response to a variety of stimuli that increase intracellular Ca(2+). We report here, using baculovirus-expressed TH, that the 14-3-3 protein binds and activates the expressed TH when the enzyme is phosphorylated at Ser-19, a site of CaM kinase II-dependent phosphorylation located in the regulatory domain of TH. Site-directed mutagenesis showed that a TH mutant in which Ser-19 was substituted by Ala retained enzymatic activity at the same level as the non-mutated enzyme, but was a poor substrate for CaM kinase II and did not bind the 14-3-3 protein. Likewise, a synthetic phosphopeptide (FRRAVpSELDA) corresponding to the part of the TH sequence, including phosphoSer-19, inhibited the interaction between the expressed TH and 14-3-3, while the phosphopeptide (GRRQpSLIED) corresponding to the site of cAMP-dependent phosphorylation (Ser-40) had little effect on complex formation. The complex was very stable with a dissociation constant of 3 nM. Furthermore, analysis of PC12nnr5 cells transfected with myc-tagged 14-3-3 showed that 14-3-3 formed a complex with endogenous TH when the cultured cells were exposed to a high K(+) concentration that increases intracellular Ca(2+) and phosphorylation of Ser-19 in TH. These findings suggest that the 14-3-3 protein participates in the stimulus-coupled regulation of catecholamine synthesis that occurs in response to depolarization-evoked, Ca(2+)-dependent phosphorylation of TH.
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PMID:Stimulus-coupled interaction of tyrosine hydroxylase with 14-3-3 proteins. 1056 54

Phototransduction is a canonical G protein-mediated cascade of retinal photoreceptor cells that transforms photons into neural responses. Phosducin (Pd) is a Gbetagamma-binding protein that is highly expressed in photoreceptors. Pd is phosphorylated in dark-adapted retina and is dephosphorylated in response to light. Dephosphorylated Pd binds Gbetagamma with high affinity and inhibits the interaction of Gbetagamma with Galpha or other effectors, whereas phosphorylated Pd does not. These results have led to the hypothesis that Pd down-regulates the light response. Consequently, it is important to understand the mechanisms of regulation of Pd phosphorylation. We have previously shown that phosphorylation of Pd by cAMP-dependent protein kinase moderately inhibits its association with Gbetagamma. In this study, we report that Pd was rapidly phosphorylated by Ca(2+)/calmodulin-dependent kinase II, resulting in 100-fold greater inhibition of Gbetagamma binding than cAMP-dependent protein kinase phosphorylation. Furthermore, Pd phosphorylation by Ca(2+)/calmodulin-dependent kinase II at Ser-54 and Ser-73 led to binding of the phosphoserine-binding protein 14-3-3. Importantly, in vivo decreases in Ca(2+) concentration blocked the interaction of Pd with 14-3-3, indicating that Ca(2+) controls the phosphorylation state of Ser-54 and Ser-73 in vivo. These results are consistent with a role for Pd in Ca(2+)-dependent light adaptation processes in photoreceptor cells and also suggest other possible physiological functions.
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PMID:Modulation of the G protein regulator phosducin by Ca2+/calmodulin-dependent protein kinase II phosphorylation and 14-3-3 protein binding. 1133 Dec 85

The class II histone deacetylases HDAC4 and HDAC5 interact specifically with the myogenic MEF2 transcription factor and repress its activity. Here we show that HDAC4 is cytoplasmic during myoblast differentiation, but relocates to the nucleus once fusion has occurred. Inappropriate nuclear entry of HDAC4 following overexpression suppresses the myogenic programme as well as MEF2-dependent transcription. Activation of the Ca(2+)/calmodulin signalling pathway via constitutively active CaMKIV prevents nuclear entry of HDAC4 and HDAC4-mediated inhibition of differentiation. Consistent with a role of phosphorylation in HDAC4 cytoplasmic localisation, HDAC4 binds to 14-3-3 proteins in a phosphorylation-dependent manner. Together these data establish a role for HDAC4 in muscle differentiation. Recently, HDAC5 has also been implicated in muscle differentiation. However, despite the functional similarities of HDAC4 and HDAC5, their intracellular localisations are opposed, suggesting a distinct role for these enzymes during muscle differentiation.
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PMID:Differential localization of HDAC4 orchestrates muscle differentiation. 1150 82

The myocyte enhancer factor-2 (MEF2) family of transcription factors regulates transcription of muscle-dependent genes in cardiac, skeletal and smooth muscle. They are activated by calcium/calmodulin (CaM)-dependent protein kinases I and IV and silenced by CaM KIIdeltaC. MEF2 is held in an inactive form by the class II histone deacetylases (HDAC) until phosphorylated by either CaM kinase I or IV. Upon phosphorylation, HDAC is transported out of the nucleus via a 14-3-3 dependent mechanism freeing MEF2 to drive transcription. The 14-3-3 chaperone protein exists as a homodimer. In the region of homodimerization, there are two canonical CaM kinase II phosphorylation sites (ser60 and ser65). In vitro phosphorylation assay results indicate that 14-3-3beta is indeed a substrate for CaM kinase II. We hypothesize that CaM kinase IIdeltaC phosphorylation of 14-3-3beta will disrupt homodimer formation resulting in the return of HDAC to the nucleus and their reassociation with MEF2. To test this, we mutated serines 60 and 65 of 14-3-3beta to aspartates to mimic the phosphorylated state. In MEF2 enhancer-reporter assays in smooth muscle cells, expression of the 14-3-3beta double mutant attenuated MEF2-enhancer activity driven by CaM kinase I or IV. The intracellular fate of HDAC4 was followed by transfection of smooth muscle cells with an HDAC4-Green Fluorescent Protein fusion hybrid. The 14-3-3beta double mutant prevented HDAC4 cytoplasmic localization in the presence of active CaM kinase I or IV. These data suggest that the mechanism of CaM kinase IIdeltaC silencing of MEF-2-dependent genes is by phosphorylation of 14-3-3beta, which allows HDAC to return to the nucleus to reform a complex with MEF2, thereby silencing MADS box-dependent gene induction in smooth muscle.
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PMID:CaM kinase IIdeltaC phosphorylation of 14-3-3beta in vascular smooth muscle cells: activation of class II HDAC repression. 1261 78


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