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)

The transsynaptic induction of the monoamine transporter present on the membrane of chromaffin granules was studied in primary cultures of dissociated bovine adrenomedullary cells submitted to a chronic secretory stimulation. The amount of the vesicular monoamine transporter was assayed by binding of the specific ligand [3H]-dihydrotetrabenazine. After several days of incubation in the presence of high potassium, the concentration of [3H]-dihydrotetrabenazine binding sites was increased by a 1.5-2.5 factor. This increase was smaller in the presence of the cholinergic agonist carbachol. The long-term inductions of the vesicular monoamine transporter, of tyrosine hydroxylase, and of acetylcholinesterase were of similar magnitude. Under the same conditions, we found no variation in either the activities of other catecholamine biosynthetic enzymes (dopamine beta-hydroxylase and DOPA decarboxylase), or in metabolic enzymes such as lactate dehydrogenase and cytochrome c oxidase, and a decrease in the cellular content of chromogranin A and cytochrome b-561. The induction of the vesicular monoamine transporter was inhibited by the calcium channel antagonists, fluspirilene and nifedipine, and was increased by the agonist Bay K 8644. It was abolished by cycloheximide and actinomycin D. These results indicate that calcium entry into chromaffin cells increases the synthesis of the vesicular monoamine transporter, presumably by transcriptional activation. Elevation of intracellular cyclic AMP concentration or activation of protein kinase C also induced an increase in the expression of the vesicular monoamine transporter. Our results confirm that components of storage vesicle membranes are differentially regulated in response to secretory stimulation, as are several cytosolic or intravesicular soluble proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of the chromaffin granule catecholamine transporter in cultured bovine adrenal medullary cells: stimulus-biosynthesis coupling. 127 22

One of the defining characteristics of neurodegenerative diseases, including Parkinson's, Alzheimer's and Huntington's diseases, is abnormal accumulations of iron, specifically in affected areas. Following injection of iron in rat brains, a relatively selective lesion of dopamine neurons, similar to parkinsonism, occurs. These observations indicate that Fe(II)-mediated generation of free radical species, by the Fenton reaction, might contribute to the pathoetiology of these diseases. Iron is known to possess multiple roles in the biosynthesis of catecholamines in dopaminergic neurons. These include, as Fe(II), facilitating the production of dopamine from phenylalanine by tyrosine hydroxylase, and as heme, assisting the recycling of ascorbate by cytochrome b-561 required for the generation of norepinephrine from dopamine by dopamine beta-hydroxylase. In this study, it is demonstrated that a human and mouse gene product, stromal cell-derived receptor 2, is a homologue of cytochrome b-561 and duodenal cytochrome b, and is thus predicted to be active as a ferric reductase. Moreover, this protein also contains a domain homologous to the N-terminal regulatory region of dopamine beta-hydroxylase. These findings from sequence analysis lead to a prediction that stromal cell-derived receptor 2 is a catecholamine-regulated ferric reductase active in the brain. Dysfunction of cytochrome b-561 or stromal cell-derived receptor 2, therefore, might predispose individuals to abnormal accumulation of Fe(III) and/or generation of cytotoxic free radicals as a consequence of a rapid cycling between Fe(III) and Fe(II). The hypothesis that aberrant ferric reductase activities are involved in the progression of neurodegenerative diseases should open up new avenues of research, and possibly therapy, for these devastating diseases.
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PMID:Domain homologues of dopamine beta-hydroxylase and ferric reductase: roles for iron metabolism in neurodegenerative disorders? 1153 94