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)

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

Tryptophan hydroxylase is activated in a crude extract by addition of ATP and Mg2+. This activation is reversible and requires in addition both Ca2+ and calmodulin. Thus, phosphorylation by an endogenous calmodulin-dependent protein kinase has long been suspected. Now that we have prepared a specific polyclonal antibody to rat brain tryptophan hydroxylase, we have been able to prove that this hypothesis is correct. After incubation of purified tryptophan hydroxylase with Ca2+/calmodulin-dependent protein kinase together with [gamma-32P]ATP, Mg2+, Ca2+, and calmodulin, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotting of the enzymes onto nitrocellulose sheets, we could label the band of tryptophan hydroxylase by the antiserum and the peroxidase technique and show by autoradiography that 32P was incorporated into this band. By measuring the radioactivity, we calculated that about 1 mol of phosphate was incorporated per 8 mol of subunits of the enzyme (2 mol of native enzyme). Because the concentration of ATP which we employed (50 microM) gives about half-maximal activation in crude extract compared to saturating ATP conditions (about 1 mM), this result indicates that the incorporation of at least 1 mol of phosphate/mol of tetramer of native tryptophan hydroxylase is required for maximal activation.
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PMID:Formal demonstration of the phosphorylation of rat brain tryptophan hydroxylase by Ca2+/calmodulin-dependent protein kinase. 254 52

The 14-3-3 protein is a family of acidic proteins present exclusively in the brain and is believed to have a function in monoamine biosynthesis because of its ability to activate tyrosine hydroxylase and tryptophan hydroxylase in the presence of Ca2+/calmodulin-dependent protein kinase type II. In this study, we resolved bovine brain 14-3-3 protein into seven polypeptide components by means of reversed-phase chromatography and determined the amino acid sequence of one of these components (eta chain) by cloning its cDNA from a bovine cerebellum cDNA library. The eta-chain mRNA is 1.8 kilobases long and encodes a polypeptide of 246 amino acids and Mr 28,221. Computer-assisted analysis of the sequence indicates that the eta chain exhibits no internal sequence repeats, nor does it have significant sequence similarity to other proteins with known amino acid sequence. However, the eta chain appears to consist of two structural regions that are distinguishable in their clearly different charge characteristics: the almost neutral amino-terminal region and the strongly acidic carboxyl-terminal region. The structural features of the eta chain and the domain organization of tyrosine and tryptophan hydroxylases suggest that the 14-3-3 protein binds to the regulatory domain of the phosphorylated hydroxylases through its acidic carboxyl-terminal region and activates the hydroxylases by inducing an active conformation.
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PMID:Molecular cloning of cDNA coding for brain-specific 14-3-3 protein, a protein kinase-dependent activator of tyrosine and tryptophan hydroxylases. 290 23

The molecular mechanism of the phosphorylation-dependent activation of tryptophan hydroxylase is studied with respect to the role of the 14-3-3 protein. Reexamination of the system reconstituted with the purified TRH and the 14-3-3 protein showed that the level of the TRH activity correlated with the extent of the Ca2+/calmodulin- or the cAMP-dependent phosphorylation in TRH. The experiment confirmed the requirement of the 14-3-3 protein for the activation, but the 14-3-3 protein added into the assay mixture did not affect either the extent nor the specificity of the phosphorylation. However, the analysis of the assay mixture on a pteridine-based affinity column indicated the formation of a complex between TRH and the 14-3-3 protein, where the complex formation depended on the phosphorylation of TRH. The complex between the phosphorylated TRH and the 14-3-3 protein could also be detected by analysis of crude brainstem extract previously phosphorylated by endogeneous Ca2+/calmodulin-dependent protein kinase. The 14-3-3 protein, therefore, appears to be a phosphorylation-dependent TRH-binding protein whose interaction causes the activation of TRH.
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PMID:Demonstration of the phosphorylation-dependent interaction of tryptophan hydroxylase with the 14-3-3 protein. 810 40

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

We previously demonstrated in mast cell lines RBL2H3 and FMA3 that tryptophan hydroxylase (TPH) undergoes very fast turnover driven by 26S-proteasomes [Kojima, M., Oguro, K., Sawabe, K., Iida, Y., Ikeda, R., Yamashita, A., Nakanishi, N. & Hasegawa, H. (2000) J. Biochem (Tokyo) 2000, 127, 121-127]. In the present study, we have examined an involvement of TPH phosphorylation in the rapid turnover, using non-neural TPH. The proteasome-driven degradation of TPH in living cells was accelerated by okadaic acid, a protein phosphatase inhibitor. Incorporation of 32P into a 53-kDa protein, which was judged to be TPH based on autoradiography and Western blot analysis using anti-TPH serum and purified TPH as the size marker, was observed in FMA3 cells only in the presence of both okadaic acid and MG132, inhibitors of protein phosphatase and proteasome, respectively. In a cell-free proteasome system constituted mainly of RBL2H3 cell extracts, degradation of exogenous TPH isolated from mastocytoma P-815 cells was inhibited by protein kinase inhibitors KN-62 and K252a but not by H89. Consistent with the inhibitor specificity, the same TPH was phosphorylated by exogenous Ca2+/calmodulin-dependent protein kinase II in the presence of Ca2+ and calmodulin but not by protein kinase A (catalytic subunit). TPH protein thus phosphorylated by Ca2+/calmodulin-dependent protein kinase II was digested more rapidly in the cell-free proteasome system than was the nonphosphorylated enzyme. These results indicated that the phosphorylation of TPH was a prerequisite for proteasome-driven TPH degradation.
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PMID:Proteasome-driven turnover of tryptophan hydroxylase is triggered by phosphorylation in RBL2H3 cells, a serotonin producing mast cell line. 1235 9

Inhibition of cAMP-dependent protein kinase (PKA) with N-[2-methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) almost completely antagonized the increase in 5-HTP accumulation and 5-HIAA/5-HT ratio in hypothalamus induced by NAS-181, a 5-HT(1B) receptor antagonist, but had no effect when the mice were treated with NAS-181 together with WAY-100,635, a selective 5-HT(1A) receptor antagonist. Inhibition of Ca(2+)-calmodulin-dependent protein kinase (CaM kinase II) with the calmodulin antagonist N-(4-aminobutyl)-5-chloro-2-naphtalenesulfonamide (W-13) did not antagonise the effect of NAS-181 alone, but counteracted that evoked by the combined treatment with NAS-181 and WAY-100,635. The results indicate that activation of tryptophan hydroxylase by reducing the tone from terminal 5-HT(1B) receptors involves PKA whereas the depolarisation-induced activation of tryptophan hydroxylase involves CaM kinase II. The increase in the 5-HIAA/5-HT ratio may under the experimental conditions used suggest CaM kinase II-induced phosphorylation of synapsin I resulting in increased 5-HT release.
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PMID:Evidence for involvement of protein kinases in the regulation of serotonin synthesis and turnover in the mouse brain in vivo. 1245 32

Serotonin (5HT) is a pivotal signaling molecule that modulates behavioral and endocrine responses to diverse chemical and physical stimuli. We report cell-specific regulation of 5HT biosynthesis by transient receptor potential V (TRPV) ion channels in C. elegans. Mutations in the TRPV genes osm-9 or ocr-2 dramatically downregulate the expression of the gene encoding the 5HT synthesis enzyme tryptophan hydroxylase (tph-1) in the serotonergic chemosensory neurons ADF, but neither the mutation nor the double mutation of both channel genes affects other types of serotonergic neurons. The TRPV genes are expressed in the ADF neurons but not in other serotonergic neurons, and act cell-autonomously to regulate a neuron-specific transcription program. Whereas in olfactory neurons OSM-9 and OCR-2 function is dependent on ODR-3 Galpha, the activity of ODR-3 or two other Galpha proteins expressed in the ADF neurons is not required for upregulating tph-1 expression, thus the TRPV ion channels in different neurons may be regulated by different mechanisms. A gain-of-function mutation in CaMKII UNC-43 partially suppresses the downregulation of tph-1 in the TRPV mutants, thus CaMKII may be an effector of the TRPV signaling. Mutations in the TRPV genes cause worms developmentally arrest at the Dauer stage. This developmental defect is due in part to reduced 5HT inputs into daf-2/insulin neuroendocrine signaling.
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PMID:Caenorhabditis elegans TRPV ion channel regulates 5HT biosynthesis in chemosensory neurons. 1499 26

Antipsychotic drugs produce acute behavioral effects through antagonism of dopamine and serotonin receptors, and long-term adaptive responses that are not well understood. The goal of the study presented here was to use Caenorhabditis elegans to investigate the molecular mechanism or mechanisms that contribute to adaptive responses produced by antipsychotic drugs. First-generation antipsychotics, trifluoperazine and fluphenazine, and second-generation drugs, clozapine and olanzapine, increased the expression of tryptophan hydroxylase-1::green fluorescent protein (TPH-1::GFP) and serotonin in the ADF neurons of C. elegans. This response was absent or diminished in mutant strains lacking the transient receptor potential vanilloid channel (TRPV; osm-9) or calcium/calmodulin-dependent protein kinase II (CaMKII; unc-43). The role of calcium signaling was further implicated by the finding that a selective antagonist of calmodulin and a calcineurin inhibitor also enhanced TPH-1::GFP expression. The ADF neurons modulate foraging behavior (turns/reversals off food) through serotonin production. We found that short-term exposure to the antipsychotic drugs altered the frequency of turns/reversals off food. This response was mediated through dopamine and serotonin receptors and was abolished in serotonin-deficient mutants (tph-1) and strains lacking the SER-1 and MOD-1 serotonin receptors. Consistent with the increase in serotonin in the ADF neurons induced by the drugs, drug withdrawal after 24-hr treatment was accompanied by a rebound in the number of turns/reversals, which demonstrates behavioral adaptation in serotonergic systems. Characterization of the cellular, molecular, and behavioral adaptations to continuous exposure to antipsychotic drugs may provide insight into the long-term clinical effects of these medications.
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PMID:Antipsychotic drugs up-regulate tryptophan hydroxylase in ADF neurons of Caenorhabditis elegans: role of calcium-calmodulin-dependent protein kinase II and transient receptor potential vanilloid channel. 1843 26

Forward genetic screening via mutagenesis is a powerful method for identifying regulatory factors in target pathways in model organisms such as the soil-dwelling free-living nematode Caenorhabditis elegans (C. elegans). Currently manual microscopy is the standard technique for conducting such screens; however, it is labor-intensive and time-consuming because screening requires imaging thousands of animals. Recently microfluidic chips have been developed to increase the throughput of some of such experiments; nonetheless, most of these chips are multilayer devices and complicated to fabricate and therefore prone to failure during fabrication and operation. In addition, most sorting decisions are made manually and the criteria used for sorting are subjective. To overcome these limitations, we developed a simple single-layer microfluidic device and an adaptive algorithm to make sorting decisions. The one-layer device greatly improves the reliability, while quantitative analysis with the adaptive algorithm allows for the identification of mutations that generate subtle changes in expression, which would have been hard to detect by eye. The screening criterion is set based on the mutagenized population, not separate control populations measured prior to actual screening experiments, to account for stochasticity and day-to-day variations of gene expression in mutagenized worms. Moreover, during each experiment, the threshold is constantly updated to reflect the balance between maximizing sorting rate and minimizing false-positive rate. Using this system, we screened for mutants that have altered expression levels of tryptophan hydroxylase, a key enzyme for serotonin synthesis in a CaMKII gain-of-function background. We found several putative mutants in this screen. Furthermore, this microfluidic system and quantitative analysis can be easily adapted to study other pathways in C. elegans.
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PMID:Quantitative screening of genes regulating tryptophan hydroxylase transcription in Caenorhabditis elegans using microfluidics and an adaptive algorithm. 2316 94


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