Ferritin light chain down-modulation generates depigmentation in human metastatic melanoma cells by influencing tyrosinase maturation.
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.
Maresca
Vittoria
V
San Gallicano Dermatological Institute, Via E. Chianesi, Rome, Italy.
Flori
Enrica
E
Cardinali
Giorgia
G
Briganti
Stefania
S
Lombardi
Daniela
D
Mileo
Anna Maria
AM
Paggi
Marco G
MG
Picardo
Mauro
M
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
D008543:Melanins; D005293:Ferritins; D014442:Monophenol Monooxygenase