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.

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.

Human immunodeficiency virus-1 Nef protein interacts with Tat and enhances HIV-1 gene expression.

The human immunodeficiency virus (HIV-1) Nef protein is now regarded as a regulatory protein responsible not only for establishment of infection and increased pathogenesis but also for enhancement of viral replication. However, the mechanism of Nef-induced activation of viral replication remains to be clearly understood. Using transient transfection assay, co-immunoprecipitation and pull-down analysis, we demonstrate in this report that the HIV-1 Nef protein physically interacts with Tat, the principal transactivating protein of HIV-1.

Gamma-glutamyl transpeptidase and its role in melanogenesis: redox reactions and regulation of tyrosinase.

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.

Type I gamma-GT mRNA is expressed in B16 melanoma and levels correlate with pigmentation.

Gamma-glutamyl transpeptidase (gamma-GT), an ectoenzyme involved mainly in glutathione metabolism, is expressed in B16 melanoma cells. B16 melanoma cells under continuous culture conditions show a phenotypic drift from melanotic to amelanotic and re-melanotic stages. We have investigated the regulation of gamma-GT in B16 melanoma cells under such different pigmentary conditions.

Vitiligo in the Ssk Community of Bangalore (a Preliminary Report).

Vitiligo among the community Somavashan Sahasajuna Kashatriya(SSK) of Baugalore surveyed by us during February-March, 1987, was found to be characterised by an earlier age of onset and a very high (90.38%) familial incidence. This community at present is small and is believed to have migrated'from Gujarat-Maharashtra border where the incidence of vitiligo in a related community, the Khatris is already high (3.