Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In cultured bovine adrenal chromaffin cells, pituitary adenylate cylase-activating polypeptide (PACAP) stimulated [14C]catecholamine synthesis from [14C]tyrosine (but not from [14C]DOPA) in a concentration-dependent manner, causing maximal stimulation at 10(-7) M. The stimulatory action of PACAP was not affected by staurosporine (an inhibitor of protein kinase C) or in the cells in which protein kinase C was down-regulated by prolonged exposure to TPA (an activator of protein kinase C), whereas it was partially attenuated in Ca(2+)-free medium. PACAP (10(-7) M) increased the formation of [3H]inositol phosphates, [Ca2+]i and 45Ca2+ uptake as well as cAMP. The peptide also stimulated the phosphorylation of tyrosine hydroxylase, the enzyme catalyzing the rate-limiting step in catecholamine synthesis. Catecholamine synthesis and tyrosine hydroxylase phosphorylation stimulated by the maximal effective concentration of dibutyryl cAMP or high K+, which activates Ca2+ uptake, were further enhanced by PACAP, suggesting that both cAMP- and Ca(2+)-dependent protein kinases may be involved in the stimulation of tyrosine hydroxylase phosphorylation and catecholamine synthesis caused by PACAP.
 ...
PMID:Stimulatory effect of pituitary adenylate cyclase-activating polypeptide on catecholamine synthesis in cultured bovine adrenal chromaffin cells: involvements of tyrosine hydroxylase phosphorylation caused by Ca2+ influx and cAMP. 786 19

Here we show that retinoic acid (RA) has the ability to alter the transmitter phenotype of cultured sympathetic neurons from newborn rats superior cervical ganglia (SCG). In the presence of RA, the level of choline acetyltransferase (ChAT) mRNA was increased, while the level of tyrosine hydroxylase (TH) mRNA was reduced in the cultured SCG neurons. Selective PCR amplification of different upstream regions of the ChAT-mRNA indicates that RA promotes the transcription of ChAT gene from R and M exons. The RA-induced upregulation of ChAT-mRNA level was significantly diminished by the chronic treatment with phorbol ester, suggesting that PKC has an important role in the induction of ChAT-mRNA in this system.
 ...
PMID:Cholinergic differentiation of cultured sympathetic neurons induced by retinoic acid. Induction of choline acetyltransferase-mRNA and suppression of tyrosine hydroxylase-mRNA levels. 790 45

The mechanism of the short-term activation by prolactin (PRL) of tyrosine hydroxylase (TH) in tuberoinfundibular dopaminergic neurons was examined in vitro on hypothalamic slices from ovariectomized rats. TH activity (determined by 3,4-dihydroxyphenylalanine accumulation in the median eminence after blockade of decarboxylase with NSD 1055) showed a dose-dependent increase within 2 h of incubation of the hypothalamic slices with PRL. To determine whether a phosphorylation process was involved in this increase in TH activity, we studied the sensitivity of the enzyme to dopamine (DA) feedback inhibition. In control median eminences, two kinetically different forms of TH coexisted, one exhibiting a Ki(DA) value of 29.92 +/- 0.49 microM, the other being approximately 15-fold more sensitive to DA inhibition with a Ki(DA) of 1.96 +/- 0.09 microM, likely corresponding to a phosphorylated and active form and to a nonphosphorylated and less active form, respectively. After PRL treatment, the TH form of low Ki(DA) remained unaffected, whereas the Ki(DA) of the purported active form of TH increased to 62.6 +/- 0.8 microM, suggesting an increase in the enzyme phosphorylation. This increase in the Ki(DA) of TH was selectively prevented by GF 109203X, a potent and selective inhibitor of protein kinase C, but not by a specific inhibitor of protein kinase A or calmodulin. Finally, this action of PRL could be mimicked by 12-O-tetradecanoylphorbol 13-acetate (a direct activator of protein kinase C). These results suggest that PRL, at the median eminence level, activates TH by increasing the enzyme phosphorylation and that this action may involve an activation of protein kinase C.
 ...
PMID:Evidence for protein kinase C involvement in the short-term activation by prolactin of tyrosine hydroxylase in tuberoinfundibular dopaminergic neurons. 790 22

The neurotoxic effect of glutamate in cultured mouse mesencephalic dopaminergic neurons was investigated. Neuron-rich cell cultures were prepared from 13-14-day-old fetal mouse ventral mesencephalic tissue. Cultures were exposed to glutamate for 10 min and evaluated for glutamate neurotoxicity (GNT) 18-24 hr later by tyrosine hydroxylase (TH) immunostaining, microtubule associated protein-2 (MAP2) immunostaining, and radiolabeled dopamine uptake assay. In glutamate-exposed cultures, the number of TH-positive neurons and the level of dopamine uptake were reduced to 40% (35-45%) and 50% (47-52%), respectively, of control cultures. The number of MAP2-positive neurons was also reduced to 47%, indicating that the GNT was not restricted or selective to dopaminergic neurons. It is concluded that GNT was mediated by the N-methyl-D-aspartic acid (NMDA) receptor from the following observations: 1) GNT was completely blocked by MK-801, an NMDA receptor antagonist; 2) NMDA itself was as toxic as glutamate; 3) 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an antagonist of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/kainate (AMPA/KA) receptor, did not block GNT; 4) kainate did not show neurotoxicity at a low concentration; and 5) two modulators of the NMDA receptor, 7-chlorokynurenic acid and magnesium, were effective in blocking GNT. Protective effects of phorbol myristate acetate, a tumor promoter, and gangliosides (GM1 and GT1b) on GNT were also demonstrated. Possible interactions between GNT and several protein kinase cascades were also investigated. Forskolin, an activator of adenyl cyclase and protein kinase A, showed some protective effect on GNT. But okadaic acid, an inhibitor of phosphatases, and genistein, a tyrosine kinase inhibitor, did not show any protective effect. These results suggest that 1) glutamate is capable of causing neuronal death in the substantia nigra; 2) GNT on dopaminergic neurons is mainly mediated by the NMDA receptor under the conditions of our study; 3) protein kinase C translocation is a key mechanism of GNT; and 4) there is an interplay of a signal transduction system in the pathomechanism of GNT.
 ...
PMID:Glutamate neurotoxicity in mesencephalic dopaminergic neurons in culture. 790 39

Activation of the tyrosine hydroxylase (TH) gene in the adrenal medulla during stress is mediated by trans-synaptic mechanisms and may involve cholinergic receptors. Stimulation of nicotinic receptors in adrenal medullary cells induces cell depolarization, influx of Ca2+ ions and increases levels of cAMP. We have shown that both cAMP and membrane depolarization produce an increase in the expression of the TH gene in cultured bovine adrenal medullary cells (BAMC). Others have proposed that transcriptional activation of the TH gene by cAMP is mediated through the sequence homologous to a cAMP responsive element (CRE) located in the proximal region of the TH gene promoter. In the present study we have examined the mechanisms by which membrane depolarization increases the TH gene activity. Treatment of serum-free BAMC cultures with the depolarizing agent, veratridine, increased the extracellular concentration of catecholamines, Met5-enkephalin, and the relative abundance of TH mRNA. Veratridine treatment also increased the levels of mRNAs for the catecholamine biosynthetic enzyme phenylethanolamine N-methyltransferase (PNMT), and proenkephalin A (PEK). Treatment for longer than 3 h was required to increase TH mRNA levels. By contrast, our previous studies indicated that cAMP stimulation for 2 h produces a maximal increase in TH mRNA levels in BAMC. The effects of veratridine and forskolin on TH mRNA levels were additive, further indicating that depolarization and cAMP activate TH gene expression via different pathways. Calmidazolium, an antagonist of calmodulin, had no effect on the veratridine-induced increase in TH mRNA levels. Similarly sphingosine treatment or preincubation with PMA, which reduce protein kinase C (PKC) activity and attenuate the induction of TH mRNA by PMA or the hormone, angiotensin II, did not affect the induction by veratridine. To identify promoter mechanisms of TH gene activation in depolarized cells we transfected BAMC with a plasmid pTHgoodLuc and treated with veratridine for 24 h. pTHgoodLUC contains a luciferase reporter gene linked to a -428/+21 bp fragment of the bovine TH gene promoter (relative to the transcription start site). Veratridine increased the expression of luciferase from the TH promoter 2.5-fold. Deletion of the -194/-54 bp promoter region containing SP-1 and POU/Oct sites reduced veratridine stimulation by 40%. Additional deletion of the -269 to -190 bp promoter segment, including an AP-1 element, further reduced veratridine stimulation to a statistically non-significant level. In conclusion, activation of TH gene expression upon depolarization is not mediated by calmodulin and PKC. Promoter sequences involved in this activation are located upstream from the CRE. Depolarization may activate TH gene transcription by acting on more than one regulatory region.
 ...
PMID:Regulation of tyrosine hydroxylase gene expression in depolarized non-transformed bovine adrenal medullary cells: second messenger systems and promoter mechanisms. 791 5

To define the precise role of cyclic AMP (cAMP)-dependent protein kinase (PKA) in transcriptional regulation of the tyrosine hydroxylase (TH) gene, we performed transient cotransfection analyses of a reporter construct containing the upstream 2,400 bp sequence of the rat TH gene with expression plasmids encoding a heat-stable specific inhibitor of PKA (PKI), a mutant regulatory subunit of PKA, or the catalytic subunit of PKA. Inhibition of PKA activity by expression of either PKI or mutant regulatory subunit blocked cAMP-stimulated induction and reduced basal transcription of the TH-reporter construct. Expression of the catalytic subunit of PKA induced the expression of the TH-reporter construct up to 50-fold in a dose-dependent manner. Primer extension analysis confirmed that PKA-mediated induction of TH-reporter expression occurred at the correct transcription initiation site. Expression of PKI did not affect induction following phorbol ester treatment, suggesting that PKA and protein kinase C (PKC) induce TH transcription by independent mechanisms. Finally, a double mutation within the cAMP response element (CRE) of TH2400-CAT diminished its basal and forskolin-stimulated transcription to the level of the promoterless plasmid, pBLCAT3, but did not alter the induction following treatment with phorbol ester, indicating that the CRE is not required for PKC-mediated transcriptional induction. Our results indicate that PKA, via the CRE, plays a crucial role for basal and cAMP-inducible transcription of the TH gene.
 ...
PMID:Cyclic AMP-dependent protein kinase regulates basal and cyclic AMP-stimulated but not phorbol ester-stimulated transcription of the tyrosine hydroxylase gene. 791 23

In the course of the purification of 14-3-3 protein (14-3-3) we found that 14-3-3 isolated from bovine forebrain activates protein kinase C (PKC), rather than the previously reported protein kinase C inhibitory activity (KCIP). We have characterized the 14-3-3 activation of PKC. The physical properties of purified PKC activator are the same as those previously reported for 14-3-3 and KCIP; i.e., (1) it is composed of subunits of molecular weight 32,000, 30,000, and 29,000; (2) it is homogeneous with respect to molecular weight, as judged by native gradient-gel electrophoresis, with a molecular weight of 53,000; and (3) it is composed of at least six isoforms when analyzed by reverse-phase HPLC. The concentration dependence of PKC activation by 14-3-3 is in the same range as that shown previously for KCIP inhibition of PKC, and as that required for 14-3-3 activation of tyrosine hydroxylase; a maximal stimulation of two- to three-fold occurs at 40-100 micrograms/ml. 14-3-3's activation of PKC is sensitive to alpha-chymotrypsin digestion but is not heat labile. Activation is specific to PKC; at least two other protein kinases, cyclic AMP- and calcium/calmodulin-dependent protein kinases, are not activated. The activation of PKC by 14-3-3 is independent of phosphatidylserine and calcium and, as such, is an alternative mechanism for the activation of PKC that obviates its translocation to membranes.
 ...
PMID:Activation of protein kinase C by purified bovine brain 14-3-3: comparison with tyrosine hydroxylase activation. 793 46

During spaceflight, alterations in blood and urinary catecholamine (CA) levels have been observed, yet the cellular/molecular mechanisms leading to these changes are not known. We used molecular, immunological, and biochemical approaches to analyze in situ the expression of catecholamine enzymes in adrenal medullary chromaffin cells of rats flown for 6 days on board Space Shuttle mission STS-54. Exposure to microgravity (10(-6) g) resulted in a 35% inhibition of both the expression and the specific activity of tyrosine hydroxylase (TH), the rate-limiting step in the cascade of CA synthesis. By contrast, the expression, specific activity, and immunoreactivity of other catecholamine-synthesizing enzymes, e.g., phenylethanolamine-N-methyl-transferase (PNMT), were not altered. The total tissue CA contents were reduced, concomitant with a decrease in the epinephrine:norepinephrine ratio. These results are in line with reports of other gravity-sensitive cellular effects and suggest that the inhibition of TH expression might be due to a direct effect of microgravity on PKC-dependent signal transduction pathways in chromaffin cells.
 ...
PMID:Microgravity decreases tyrosine hydroxylase expression in rat adrenals. 795 25

The intracellular mechanisms through which two trophic factors, ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF), regulate cholinergic development were examined in sympathetic neuron cultures. Treatment with CNTF or LIF increased levels of choline acetyltransferase (ChAT) activity by 375 and 350%, respectively. However, in neuronal cultures depleted of protein kinase C (PKC) activity by chronic phorbol ester treatment, neither CNTF nor LIF elevated ChAT activity. Further, the stimulation of ChAT due to increased cell density was not observed in PKC-depleted sympathetic neurons. The inhibition of CNTF-stimulated ChAT by phorbol ester occurred in a dose-dependent manner and chronic phorbol ester treatments did not alter the levels of the catecholamine biosynthetic enzyme tyrosine hydroxylase. Moreover, increased levels of diacylglycerol, an endogenous activator of PKC, were observed in sympathetic neurons treated with CNTF. However, neither CNTF nor LIF stimulated the hydrolysis of phosphatidylinositol 4,5-bisphosphate. These observations suggest that a common PKC-dependent pathway, which is independent of phosphatidylinositol 4,5-bisphosphate hydrolysis, mediates the cholinergic stimulating effects of CNTF, LIF, and cell-cell contact in cultured sympathetic neurons.
 ...
PMID:The cholinergic stimulating effects of ciliary neurotrophic factor and leukemia inhibitory factor are mediated by protein kinase C. 838 Jan 92

Exoenzyme S (ExoS), which has been implicated as a virulence factor of Pseudomonas aeruginosa, catalyzes transfer of the ADP-ribose moiety of NAD+ to many eukaryotic cellular proteins. Its preferred substrates include Ras and several other 21- to 25-kDa GTP-binding proteins. ExoS absolutely requires a ubiquitous eukaryotic protein factor, termed FAS (factor activating ExoS), for enzymatic activity. Here we describe the cloning and expression of a gene encoding FAS from a bovine brain cDNA library and demonstrate that purified recombinant FAS produced in Escherichia coli activates ExoS in a defined cell-free system. The deduced amino acid sequence of FAS shows that the protein (245 residues, calculated molecular mass 27,743 Da) belongs to a highly conserved, widely distributed eukaryotic protein family, collectively designated as 14-3-3 proteins. Various functions have been reported for members of the 14-3-3 family, including phospholipase A2 activity and regulation of tyrosine hydroxylase, tryptophan hydroxylase, and, possibly, protein kinase C activities. Identification of FAS as a 14-3-3 protein establishes an additional function for this family of proteins--the activation of an exogenous ADP-ribosyltransferase. Elucidation of the precise role of FAS in activating ExoS will contribute to understanding the molecular mechanisms by which P. aeruginosa causes disease.
 ...
PMID:The eukaryotic host factor that activates exoenzyme S of Pseudomonas aeruginosa is a member of the 14-3-3 protein family. 846 Jan 41


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>