title: Ferritin light chain down-modulation generates depigmentation in human metastatic melanoma cells by influencing tyrosinase maturation.
abstract: Recently, after the identification of ferritin light chain (L-ferritin) gene and protein over-expression in human metastatic melanoma cells, we engineered, starting from the LM metastatic melanoma cell line, clones in which L-ferritin gene expression was down-regulated by the stable expression of a specific antisense construct. The present investigation started from the observation that L-ferritin down-regulated LM cells displayed a less pigmented phenotype, confirmed by a major decrease of total melanin, when compared to control LM cells. This finding was accompanied by a dramatic decrease in tyrosinase activity, which was not paralleled by a concomitant reduction of the amount of tyrosinase specific mRNA. Western blot analysis of tyrosinase in control LM cells displayed a pattern, which corresponds to the progressive glycosylation of the native protein up to the 80 kDa form, considered the functional one. Tyrosinase pattern assayed in L-ferritin down-regulated LM cells showed the remarkable absence of the 80 kDa form and a prevalence of endoglycosidase H (endo H)-sensitive immature (70 kDa) tyrosinase, accumulated in the endoplasmic reticulum (ER), as confirmed by confocal microscopy analysis. These results demonstrate that, in a human metastatic melanoma cell line, the stress condition promoted by L-ferritin down-modulation, can substantially influence proper maturation of tyrosinase.
authors.affiliation: San Gallicano Dermatological Institute, Via E. Chianesi, Rome, Italy.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Maresca
authors.forename: Enrica
authors.initials: E
authors.lastname: Flori
authors.forename: Giorgia
authors.initials: G
authors.lastname: Cardinali
authors.forename: Stefania
authors.initials: S
authors.lastname: Briganti
authors.forename: Daniela
authors.initials: D
authors.lastname: Lombardi
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Mileo
authors.forename: Marco G
authors.initials: MG
authors.lastname: Paggi
authors.forename: Mauro
authors.initials: M
authors.lastname: Picardo
mesh_terms: D045744:Cell Line, Tumor; D015536:Down-Regulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005293:Ferritins / Q000235:genetics / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D017496:Hypopigmentation; D008543:Melanins / Q000378:metabolism; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D009362:Neoplasm Metastasis; D010858:Pigmentation / Q000502:physiology*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D014158:Transcription, Genetic
chemical_list: D008543:Melanins; D005293:Ferritins; D014442:Monophenol Monooxygenase