On the Possible Function of Coated Vesicles in Melanogenesis of the Regenerating Fowl Feather

Maul, Gerd G.; Brumbaugh, J. A.

doi:10.1083/jcb.48.1.41

Cited by 105 publications

(33 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our present results demonstrate that RACK-I on melanosomes anchors activated PKC-β, allowing the kinase to phosphorylate tyrosinase. The localization of RACK-I to melanosomes is strongly suggested by its co-localization, as demonstrated by confocal microscopy, with tyrosinase, a transmembrane protein known to be detected at the melanosome surface (Jimbow and Fitzpatrick, 1973;Maul and Brumbaugh, 1971). However, further support for this localization is provided by the readily detectable level of RACK-I in the purified melanosome preparation, as demonstrated by immunoblotting.…”

Section: Discussionmentioning

confidence: 92%

“…A subconfluent culture of melanocytes was processed for double immunostaining using a monoclonal antibody against RACK-I and a polyclonal antibody against tyrosinase (obtained from Vincent Hearing at NIH), a protein known to localize to the melanosome surface in its mature state (Jimbow and Fitzpatrick, 1974;Maul and Brumbaugh, 1971), as described under Materials and Methods. Diffuse perinuclear staining for RACK-I was observed (Fig.…”

Section: Rack-i Is Localized In Part To Melanosomesmentioning

confidence: 99%

See 1 more Smart Citation

The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-β on melanosomes

Park

Killoran

et al. 2004

Journal of Cell Science

View full text Add to dashboard Cite

Protein kinase C (PKC), a family of at least eleven isoforms, mediates numerous cell functions. In human melanocytes, α, β, δ, ϵ and ζ isoforms of PKC are expressed, but uniquely PKC-β activates tyrosinase, the key and the rate-limiting enzyme in melanogenesis, by phosphorylating specific serine residues on its cytoplasmic domain. To investigate the mechanism by which only PKC-β phosphorylates tyrosinase, we examined the expression of receptor for activated C-kinase-I (RACK-I), a receptor specific for activated PKC-β, on the surface of melanosomes, the specialized organelle in which melanogenesis occurs. Immunoblot analysis of purified melanosomes revealed that RACK-I is readily detectable. Immunoprecipitation of RACK-I from purified melanosomes, followed by immunoblot analysis using antibody against PKC-β, revealed abundant PKC-β, whereas PKC-α was not detected when immunoblot analysis was performed using antibody against PKC-α. Activation of PKC in melanocytes increased the level of PKC-β co-immunoprecipitated with RACK-I, while the level of melanosome-associated RACK-I decreased when melanocytes were treated chronically with the 12-0-tetradecanoyl-phorbol 13-Acetate (TPA), a condition known to deplete PKC and reduce tyrosinase activity. Immunoprecipitation with RACK-I antibody co-precipitated fewer PKC-β in the presence of UV-activated 1, 1′-decamethylenebis-4-aminoquinaldinium di-iodide (DECA), known to disrupt the interaction between activated PKC-β and RACK-I. Treatment of intact melanocytes with DECA also decreased tyrosinase activity. Moreover, suppression of RACK-I expression by transfecting melanocytes with siRNA against RACK-I reduced the basal tyrosinase activity and blocked TPA-induced increases in tyrosinase activity. Taken together, these results demonstrate that RACK-I anchors activated PKC-β on the melanosome membrane, allowing PKC-β to phosphorylate tyrosinase.

show abstract

Section: Discussionmentioning

confidence: 92%

Section: Rack-i Is Localized In Part To Melanosomesmentioning

confidence: 99%

The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-β on melanosomes

Park

Killoran

et al. 2004

Journal of Cell Science

View full text Add to dashboard Cite

show abstract

“…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)(2)(3)(4)(5).…”

mentioning

confidence: 99%

“…Melanogenic activities were radiometrically assayed in extracts as detailed (28, 29); briefly, the tyrosinase assay uses [3,5-3H]tyrosine (1 Ci/mmol, New England Nuclear) and measures the 3H20 released as tyrosine is hydroxylated to dihydroxyphenylalanine. The melanin formation assay uses L-[U-14C]tyrosine (100 mCi/mmol, New England Nuclear) and measures the entire melanogenic pathway; it reflects the many separate enzymatic and nonenzymatic steps required to produce melanin.…”

mentioning

confidence: 99%

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

Jiménez

Kameyama²,

Maloy³

et al. 1988

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

129

View full text Add to dashboard Cite

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...

show abstract

“…The enzyme localizations in human melanoma tissue and cultured melanoma cells were similar to those of B-16 and Harding-Passey melanoma (14), hamster melanoma cells in vitro (19), melanocyte of the fowl (3) and regenerating fowl feather (11), and human melanocytes (7,8).…”

Section: Dopa Oxidase In Cultured Melanoma Cells and Melanoma Tissuesmentioning

confidence: 68%

An Application of Electron Microscopic Cytochemistry to Human Tumors

Yokoyama

1973

Acta Histochem. Cytochem

View full text Add to dashboard Cite

On the Possible Function of Coated Vesicles in Melanogenesis of the Regenerating Fowl Feather

Cited by 105 publications

References 19 publications

The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-β on melanosomes

The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-β on melanosomes

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

An Application of Electron Microscopic Cytochemistry to Human Tumors

Contact Info

Product

Resources

About