Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.10.3.1 (tyrosinase)
9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have cloned and sequenced mouse cDNAs corresponding to a third member of a family of melanocyte-specific mRNAs, which encode tyrosinase and related proteins. This new member, tyrosinase-related protein-2 (TRP-2), has approximately 40% amino acid identity with the two other proteins in the family and has the same structural features including two copper binding sites, two cysteine-rich regions, a signal peptide and a transmembrane domain. We now show that one of the cysteine-rich regions in this protein family is an 'EGF-like' repeat found in many extracellular and cell surface proteins. The gene encoding TRP-2 maps to mouse chromosome 14, in the region of the coat colour mutation slaty. We show that the TRP-2 of slaty mice has a single amino acid difference from wild-type TRP-2; a substitution of glutamine for arginine in the first copper binding site. TRP-2 is the much sought melanogenic enzyme DOPAchrome tautomerase (DT), which catalyses the conversion of DOPAchrome to 5,6,dihydroxyindole-2-carboxylic acid. Extracts from mice homozygous for the slaty mutation have a 3-fold or more reduction in DT activity, indicating that TRP-2/DT is encoded at the slaty locus, and the missense mutation reduces but does not abolish the enzyme activity.
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PMID:A second tyrosinase-related protein, TRP-2, maps to and is mutated at the mouse slaty locus. 153 34

There is no available monoclonal antibody which reacts specifically recognizes human tyrosinase. Employing a synthetic peptide, MEKEDYHSLYQSHL, corresponding to the carboxyl terminus of human tyrosinase as an immunogen, we produced a mouse monoclonal antibody MAT-1 of the IgG1 isotype. The epitope for MAT-1 was determined to be EDYH, the sequence of which is not present in human tyrosinase-related protein-1 (TRP-1) or tyrosinase-related protein-2 (TRP-2). By transient expression assays and immunofluorescence technique, we show that MAT-1 reacts specifically with cells expressing human tyrosinase cDNA but not with cells expressing TRP-1 or TRP-2 cDNA. The results of immunohistochemical staining also confirmed that MAT-1 reacts specifically with epidermal melanocytes in human skin sections. MAT-1 should be invaluable for studying the interaction between tyrosinase and TRPs and for detecting the changes in the levels of tyrosinase expression. In addition, MAT-1 should be useful as a sensitive immunohistochemical tool for investigation of various pigmentary disorders and possibly for the diagnosis of melanoma.
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PMID:MAT-1, a monoclonal antibody that specifically recognizes human tyrosinase. 749 Apr 69

Cultures of differentiated melanocytes can readily be grown from the dissociated epidermis of neonatal mice, and immortal cell lines often develop from these. However, the first cells that grow and transiently dominate the cultures, while similar to melanocytes, are unpigmented. These have been shown to be precursors of melanocytes and may be termed melanoblasts. Under our previous standard culture conditions, involving the use of keratinocyte feeder cells, foetal calf serum, the phorbol ester 12-O-tetradecanoyl phorbol acetate (TPA) and cholera toxin, all the melanoblasts spontaneously differentiated to pigmented melanocytes within about 3 weeks. We now describe some factors affecting the proliferation and differentiation of diploid murine melanoblasts in the presence of serum. Murine stem cell factor/steel factor (SCF), basic fibroblast growth factor (bFGF) and murine leukaemia inhibitory factor/differentiation-inhibiting activity (LIF/DIA) all increased melanoblast numbers. SCF and LIF also slightly inhibited melanoblast differentiation, while cholera toxin and TPA promoted differentiation. Using some of these findings, and by regular replacement of keratinocyte or fibroblastoid feeder cells, we have established a clonal line of immortal murine melanoblasts, 'melb-a'. These cells express tyrosinase-related protein-2 but not, in general, tyrosinase. They can be induced to differentiate irreversibly to functional melanocytes (also proliferative and immortal) by plating in the absence of feeder cells. Thus a new immortal melanocyte line, 'melan-a2', has also been produced.
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PMID:A cloned, immortal line of murine melanoblasts inducible to differentiate to melanocytes. 754 May 32

Tyrosinase, tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2, (TRP-2, dopachrome tautomerase) were shown by immunoblotting and enzyme assays to copurify from extracts of Cloudman S91 melanoma cells. Antibodies to TRP-1 and TRP-2 immunoprecipitated tyrosinase activity, suggesting a stable interaction (complex) among these proteins. The tyrosine hydroxylase activity of tyrosinase was reduced in the complexed form; treatment with Triton X-100 dissociated the complex and activated the tyrosinase present within it. To further study this complex, we employed sucrose gradient density centrifugation of extracts from cultured murine melanocytes. Tyrosinase, TRP-1, and TRP-2 all existed in high molecular weight "multimers" of approximately 200 to > 700 kilodaltons. Extraction of cells with buffers containing the detergent CHAPS preserved the high molecular weight multimers; Triton X-100 caused their dissociation into monomers. Low pH, low ionic strength, and millimolar concentrations of calcium ions favored the maintenance of multimers. The results of this study demonstrate that the participation of tyrosinase, TRP-1, and TRP-2 in a multimeric complex could have important physiologic consequences, and raise the possibility that some of the well-known interactions between coat color genes may be explained by intermolecular interactions between the gene products.
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PMID:High-molecular-weight forms of tyrosinase and the tyrosinase-related proteins: evidence for a melanogenic complex. 804 Jun 9

Retinoic acid (RA) is a hormone-like agent involved in the control of cell differentiation. The most characteristic feature of melanocyte differentiation, melanogenesis, is stimulated by UV radiations. Excessive chronic sun exposure results in irregular skin hypermelanosis that can be partially corrected by topical RA. The basic mechanisms underlying this effect of RA are unknown. To determine whether RA can directly modulate excessive melanin synthesis, we analyzed the in vitro effect of cis- and trans-RA on UVB-induced melanogenesis in S91 mouse melanoma cells and in normal human melanocytes (NHM). In both cells types, the two RA isoforms significantly decreased the UVB-stimulated melanogenesis in term of tyrosinase activity and melanin neosynthesis. To correlate changes in melanogenesis with the expression of melanogenic enzymes, we determined the neosynthesis rate of tyrosinase, tyrosinase-related protein-1 (TRP-1/gp 75) and tyrosinase-related protein-2 (TRP-2/DOPAchrome tautomerase). Here we show that UVB-induced melanogenesis in NHM is related to an increased synthesis of tyrosinase and TRP-1 and to a dramatic decrease of TRP-2 expression. RA inhibition of UVB-induced melanogenesis acts at the post-transcriptional level leading to a decreased tyrosinase and TRP-1 synthesis. We also show that in NHM, inhibition of TRP-2 following UVB-treatment is significantly reversed by RA. This demonstrates a negative correlation between melanogenesis and TRP-2 expression.
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PMID:Retinoic acid as modulator of UVB-induced melanocyte differentiation. Involvement of the melanogenic enzymes expression. 805 33

Using antibodies that recognize either tyrosinase, tyrosinase-related protein-1 (TRP1), or tyrosinase-related protein-2 (TRP2, DOPAchrome tautomerase), the quantities of those melanogenic enzymes were analyzed in five melanoma cell lines that possess various degrees of melanin production. All cells except JB/MS-W increased melanin production four to 30 times after 4 d of melanocyte-stimulating hormone (MSH) treatment. Melanin production by JB/MS-W cells was always under background, with or without MSH treatment. There was a positive correlation between quantities and synthetic rates of those melanogenic enzymes and their melanin formation or DOPAchrome tautomerase activities. The activity of a heat-resistant melanogenic inhibitory factor was also analyzed. The results showed, surprisingly, that pigmented cells showed higher levels of melanogenic inhibitors activity. Tyrosinase activity was increased dramatically whereas the level of melanogenic inhibitor was remarkably decreased following MSH treatment. Interestingly, melanogenic inhibitor derived from JB/MS-W cells suppressed not only tyrosinase but also DOPAchrome tautomerase, another enzyme functional in melanin production. These results clearly suggest that melanin production is regulated by a subtle balance between the activities of these enzymes and other factors such as the melanogenic inhibitor.
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PMID:Pigment production in murine melanoma cells is regulated by tyrosinase, tyrosinase-related protein 1 (TRP1), DOPAchrome tautomerase (TRP2), and a melanogenic inhibitor. 842 35

We have isolated the eight exons and 5' and 3' flanking regions of the mouse tyrosinase-related protein-2 (dopachrome tautomerase) gene (Tyrp2/Dct), which is mutated in slaty mice. The gene has a structure that is considerably different from those of other tyrosinase family members in both the number and the position of introns, consistent with the suggestion that the divergence of the family represents an ancient gene duplication. We also identify in the 5' flanking DNA an 11-bp element, the M-box, conserved in other tyrosinase family genes. We have characterized point mutations in two slaty alleles recently identified at the Jackson Laboratory: slaty-2J (slt2J) has a similar phenotype to the original slaty (slt) mutation, and slaty light (Sltlt), which has a more severe effect and is semidominant. We suggest that the slaty-light phenotype is a result of the failure of the enzyme to be correctly targeted to its normal location on the inner face of the melanosomal membrane.
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PMID:Structure of the mouse tyrosinase-related protein-2/dopachrome tautomerase (Tyrp2/Dct) gene and sequence of two novel slaty alleles. 853 99

Melanocytic cells can produce two types of pigment, pheomelanin or eumelanin. We used two types of human melanoma cell lines to explore the regulation of pigmentation by biochemical and enzymatic studies. These two cell lines were previously designated as either pheomelanotic or of mixed type when cultured in a medium rich in cysteine. We analyzed the effects of L-cysteine depletion on melanin synthesis and the involvement of the tyrosinase-related proteins in the production of both eumelanin and pheomelanin. Cultures were exposed to L-cysteine concentrations ranging from 206 to 2.06 microM, and the following parameters were measured: tyrosine hydroxylase activity, intracellular L-cysteine and glutathione concentrations, eumelanin and pheomelanin formation, and tyrosinase-related protein-1 and -2 mRNA levels. Extracellular L-cysteine depletion significantly increased tyrosine hydroxylase activity and promoted both eumelanogenesis and visible pigmentation in both lines. In contrast, pheomelanogenesis was increased only in the pheomelanotic cell line. Whereas eumelanogenesis was apparent upon L-cysteine depletion, tyrosinase-related protein-1 expression was not induced in the pheomelanotic cells, and tyrosinase-related protein-2 expression remained unchanged. Thus, tyrosinase-related protein-1 mRNA expression seems to be concomitant with eumelanogenesis when the L-cysteine concentration is high, but does not appear essential for eumelanogenesis at low L-cysteine concentrations. The mechanisms governing pheomelanin to eumelanin balance are dependent on L-cysteine, glutathione, and tyrosinase-related protein-1 expression, but none of these factors alone appears to be dominant in directing the synthesis of a particular type of melanin.
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PMID:Cysteine deprivation promotes eumelanogenesis in human melanoma cells. 887 52

Several laboratories are pursuing the question of whether the expression of pigment genes can be used as a useful marker for tumour progression. However, many melanoma tumours are amelanotic in vivo. The purpose of this study was to examine the relationship between the expression of tyrosinase-related genes [tyrosinase, tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2)] and pigmentation of melanoma cells. Fourteen cutaneous melanoma cell lines were examined for visible pigment, melanin content, and dopa oxidase activity and findings were related to the previously determined expression of the three tyrosinase-related genes in these cells in culture. Four of the cell lines were also stimulated with alpha-MSH, isobutylmethylxanthine, and forskolin to examine the relationship between induced pigmentation and upregulation of pigmentation genes. There was no simple correlation between pigmentation gene expression and dopa oxidase activity or total melanin content of the 14 melanoma cell lines in culture. In the majority of cells, there was no appreciable pigment, whereas, in contrast, half of the cells showed significant dopa oxidase activity. Upregulation of dopa oxidase activity was achieved by alpha-MSH in two out of four cell lines examined in detail and with IBMX in three out of four of these cell lines. IBMX increased tyrosinase gene expression in all four cell lines; alpha-MSH was without effect; and TRP-1 and TRP-2 expression were largely unaffected by IBMX or alpha-MSH. Modest changes in morphology were noted in response to IBMX. Overall, however, human melanoma cell lines were, with two exceptions, amelanotic in culture despite the fact that 10 out of the 14 lines expressed tyrosinase-related genes. We conclude that measurable pigmentation is not a necessary consequence of the expression of pigmentation genes. An implication of this work is that amelanotic tumours in vivo may nevertheless be positive for tyrosinase-related genes.
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PMID:Human melanoma cell lines show little relationship between expression of pigmentation genes and pigmentary behaviour in vitro. 973 Mar 20

In the present study we describe the in vitro transcription-translation of human melanocyte-specific protein Pmel17 cDNA and subsequent use of the resulting 35S-labelled Pmel17 in an RIA to analyse vitiligo sera for the presence of Pmel17 antibodies. Of 53 vitiligo sera examined in the assay, three (5.9%) were found to be positive for Pmel17 antibodies. In contrast, sera from 20 healthy controls, 10 patients with Hashimoto's thyroiditis and 10 patients with Graves' disease (GD) were all negative for Pmel17 antibodies. All three patients positive for Pmel17 antibodies (aged 50-63 years) had had vitiligo of the symmetrical type for > 1 year and all of them also had an associated autoimmune disorder: GD in one and autoimmune hypothyroidism in two. In addition, all three patients had antibodies to the melanogenic enzymes tyrosinase, tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2) in their serum. Absorption studies indicated that preincubation with COS-7 cell extract containing expressed Pmel17 absorbed out the immunoreactivity of the three sera positive in the RIA, confirming the anti-Pmel17 reactivity of the sera from these patients. In contrast, COS-7 cell extracts containing either expressed tyrosinase, TRP-1 or TRP-2 did not remove the anti-Pmel17 reactivity of the three sera in the RIA. This lack of cross-reactivity suggests that the humoral response to Pmel17 in these patients is specific and independent of the antibody reactivity to tyrosinase, TRP-1 and TRP-2.
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PMID:Autoantibodies to human melanocyte-specific protein pmel17 in the sera of vitiligo patients: a sensitive and quantitative radioimmunoassay (RIA). 984 40


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