Type I γ‐GT mRNA is Expressed in B16 Melanoma and Levels Correlate with Pigmentation

Chaubal, Vaishali A.; Nair, Sujit S.; Mojamdar, Manoj

doi:10.1034/j.1600-0749.2002.02026.x

Cited by 4 publications

(2 citation statements)

References 22 publications

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“…To obtain a uniformly melanotic population of B16F10 mouse melanoma cells, the cells grown in culture were injected subcutaneously in C57BL/6J mice as described elsewhere (Chaubal et al, 2002). The protocols used have been duly approved by the Institutional (NCCS) Biosafety and Bioethics Committee.…”

Section: Tumor Induction In C57bl/6j Micementioning

confidence: 99%

Increased level of p27 subunit of proteasomes and its co-localization with tyrosinase in amelanotic melanoma cells indicate its direct role in the regulation of melanin biosynthesis

Godbole¹,

Mojamdar²,

Pal³

2006

Cell Biology International

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Proteasomes have been shown to be involved in the regulation of melanin biosynthesis in melanoma cells. Here we report on the correlation between proteasome subunits and Tyrosinase (Tyr) activity in different cell phenotypes, and thereby regulation of melanin biosynthesis in B16F10 mouse melanoma cells. Our results indicated that the quantity of proteasome subunit p27 is higher and that of the enzyme Tyr and its activity are lower in amelanotic melanoma cells, while the reverse is true in melanotic melanoma cells. Proteasome subunit p27, compared to another subunit p31, shows increased co-localization with Tyr and Tyrosinase related protein 1 (Trp1) in amelanotic cells to a greater extent than that in melanotic cells. On exposure to cycloheximide, increased Tyr degradation was seen in amelanotic cells, as indicated by increased co-localization of p27 and Tyr. Further, exposure of amelanotic melanoma cells with proteasome-specific inhibitor MG132 resulted in an increased Tyr activity, increased levels of Tyr and Trp1, leading to increased melanin synthesis. These results therefore suggest that proteasomes, particularly p27 subunit, are directly involved in the regulation of melanin biosynthesis in mouse melanoma cells.

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Section: Tumor Induction In C57bl/6j Micementioning

confidence: 99%

Increased level of p27 subunit of proteasomes and its co-localization with tyrosinase in amelanotic melanoma cells indicate its direct role in the regulation of melanin biosynthesis

Godbole¹,

Mojamdar²,

Pal³

2006

Cell Biology International

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“…The cells were harvested at various time points and tyrosinase activity was determined. γ ‐Glutamyl transpeptidase and tyrosinase assays have been described previously (14). One unit of γ ‐GT activity is defined as the amount that catalyzes the formation of 1 μ mol of p ‐nitroaniline/min.…”

Section: Stimulation Of γ‐Gt Activitymentioning

confidence: 99%

γ ‐Glutamyl Transpeptidase and its Role in Melanogenesis: Redox Reactions and Regulation of Tyrosinase

Chaubal

Nair

Ito

et al. 2002

Pigment Cell Research

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Metabolism of glutathione by gamma-glutamyl transpeptidase (gamma-GT) at the level of cell membrane has been shown to generate hydrogen peroxide in many cell types including human melanomas. gamma-GT does not appear to be involved in cysteine uptake for pheomelanin production in melanoma cells and does not contribute significantly to the pheomelanin synthesized in B16 melanoma cells. We have therefore examined the possibility of gamma-GT mediated production of prooxidant reactions and its effect, if any, on pigmentation using B16 melanoma cells. Our results indicate that in B16 melanoma cells, gamma-GT activity leads to the production of hydrogen peroxide. We further show that the nuclear levels of the redox sensitive transcription factor NF-kappa B is regulated by H2O2 formed by the action of gamma-GT: stimulation and inhibition of gamma-GT affect the levels of NF-kappa B. Tumor necrosis factor alpha, a hypopigmenting cytokine, known to activate NF-kappa B also up-regulates the gamma-GT messenger RNA and activity. Stimulation of gamma-GT generated prooxidant reactions led to a decrease in tyrosinase activity. We therefore propose that prooxidant reactions mediated by gamma-GT in turn regulate the levels of tyrosinase in pigment cells. Our findings thus introduce a new aspect in the regulation of pigmentation and ascribe a novel role for gamma-GT in pigment cells.

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Tyrosinase Degradation in Amelanotic Melanoma Cells is Mediated by Cytoplasmic Factors in Addition to Proteasome-Mediated Mechanism

Godbole

Coux

Pal

2014

Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci.

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Type I γ‐GT mRNA is Expressed in B16 Melanoma and Levels Correlate with Pigmentation

Cited by 4 publications

References 22 publications

Increased level of p27 subunit of proteasomes and its co-localization with tyrosinase in amelanotic melanoma cells indicate its direct role in the regulation of melanin biosynthesis

Increased level of p27 subunit of proteasomes and its co-localization with tyrosinase in amelanotic melanoma cells indicate its direct role in the regulation of melanin biosynthesis

γ ‐Glutamyl Transpeptidase and its Role in Melanogenesis: Redox Reactions and Regulation of Tyrosinase

Tyrosinase Degradation in Amelanotic Melanoma Cells is Mediated by Cytoplasmic Factors in Addition to Proteasome-Mediated Mechanism

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