Microheterogeneity of melanosome-bound tyrosinase from the harding-passey murine melanoma

Ferrini, Umberto; Mileo, Anna Maria; Hearing, Vincent J.

doi:10.1016/0020-711x(87)90025-5

Cited by 17 publications

(9 citation statements)

References 17 publications

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“…Also, intracellular melanin has been shown to reduce the formation of both CPD and 6‐4PP in cultured human melanocytes and melanoma cells 82,86 . That melanin provides epidermal photoprotection has been supported by the fact that poorly melanized skin is far more vulnerable than melanized skin to injury caused by UVR 27 …”

Section: Melanocytes In Skin and Hair Pigmentationmentioning

confidence: 99%

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The biology of melanocytes

Sulaimon

Kitchell

2003

Veterinary Dermatology

117

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In veterinary medicine, our understanding of the biology and regulation of melanocytic function is mostly based on information realized from human and murine studies. Improved understanding of the biology of melanocytes is needed to develop more effective treatment regimens for malignant melanoma and other melanocytic disorders. In vertebrates, melanocytes are well known for their role in skin pigmentation, hair and feather coloration, and for their ability to produce and distribute melanin to surrounding keratinocytes. Enzymes involved in melanin synthesis are present exclusively in melanosomes. The type of melanin synthesized by melanocytes in mammals is regulated at a genetic, biochemical and environmental level. These regulatory factors affect not only the phenotypic appearance, but also the photoprotective properties of melanin. This review addresses the biology of melanocytes, melanin synthesis and the photoprotective properties of melanin.

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Section: Melanocytes In Skin and Hair Pigmentationmentioning

confidence: 99%

“…Nascent tyrosinase is transported to the Golgi complex, where asparagine‐linked glycosylation of tyrosinase is completed before export into the melanosomes. At the Golgi complex glycosylation is essential for the normal structure and function of tyrosinase 27,28 …”

Section: Melanocytes In Skin and Hair Pigmentationmentioning

confidence: 99%

The biology of melanocytes

Sulaimon

Kitchell

2003

Veterinary Dermatology

117

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“…The other three forms (T1, T2, and T3) appear to be precursors of the T4 form of the enzyme, differing only with respect to their posttranslational modifications (9). After solubilization of melanosomes with ionic detergents or trypsin, T4 tyrosinase is dissociated into monomeric units and shows the same electrophoretic mobility as T1 tyrosinase (10, 11), with a Mr ':70,000.…”

mentioning

confidence: 92%

Mammalian tyrosinase: biosynthesis, processing, and modulation by melanocyte-stimulating hormone.

Jiménez

Kameyama²,

Maloy³

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

129

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We have examined the rate of synthesis and degradation of tyrosinase (monophenol, 3,4-dihydroxyphen-ylalanine:oxygen oxidoreductase, EC 1.14.18.1), the critical enzyme involved in mammalian pigmentation, using pulsechase metabolic labeling of murine melanoma cells and immunoprecipitation of protein extracts with antibodies directed specifically against the enzyme. We have found that tyrosinase is synthesized and glycosylated within melanocytes rapidly, since significant quantities of pulse-labeled enzyme could be detected within 30 min. Tyrosinase (monophenol, 3,4-dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1), a single-chain glycoprotein enzyme essential to pigment formation in mammals, is specifically localized in melanocytes, which occur primarily in the skin, hair bulbs, and eyes. The principal subcellular site of tyrosinase activity has been determined to be the melanosome; however, tyrosinase is demonstrable in the soluble, ribosomal, endoplasmic reticulum and Golgi apparatus fractions. Although the exact sequence of posttranslational processing is still unknown, tyrosinase appears to be synthesized on ribosomes, transferred through the endoplasmic reticulum and the Golgi apparatus, where it is glycosylated and packaged into vesicles prior to fusion with premelanosomes (1-5).Tyrosinase occurs in four distinct microheterogeneous forms as identified by PAGE (6)(7)(8); the high molecular weight membrane-bound form of tyrosinase found in melanosomes where physiologic melanin production occurs is termed T4 tyrosinase. The other three forms (T1, T2, and T3) appear to be precursors of the T4 form of the enzyme, differing only with respect to their posttranslational modifications (9). After solubilization of melanosomes with ionic detergents or trypsin, T4 tyrosinase is dissociated into monomeric units and shows the same electrophoretic mobility as T1 tyrosinase (10, 11), with a Mr ':70,000. Recently, some of us have succeeded in producing monoclonal antibodies specifically directed against the mature glycosylated T4 form of murine tyrosinase (12); these have proved to be useful in the identification and study of normal and transformed human melanocytes (13,14). In addition, specific antibodies against synthetic peptides encoded by the tyrosinase gene have been prepared (15).In this study we have examined the rate of synthesis and degradation of tyrosinase in murine melanocytes using these specific antibodies for immunoprecipitation of pulse-chase metabolically labeled cells. Further, we have used this model system to analyze the mechanisms involved in the modulation of melanogenesis in response to melanocyte-stimulating hormone (MSH), a specific differentiating stimulus that causes a dramatic increase in tyrosinase activity and pigmentation in melanocytes (16)(17)(18)(19)(20) Abbreviation: MSH, melanocyte-stimulating hormone. §To whom reprint requests should be addressed.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby m...

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“…The other three forms (T 1 , T 2 , and T 3 ) appear to be precursors of the enzyme, differing with respect of their posttranslational modifications (29). After solubilization of melanosomes with ionic detergents or trypsin, T 4 tyrosinase is dissociated into monomeric units and shows the same electrophoretic mobility as T 1 tyrosinase, with a molecular mass about 70 kDa.…”

Section: Background Tyrosinasementioning

confidence: 88%