The ocular albinism type 1 gene product is a membrane glycoprotein localized to melanosomes

M. Vittoria Schiaffino, Cinzia Baschirotto, Graziella Pellegrini, Simona Montalti, Carlo Tacchetti, Michele De Luca, Andrea Ballabio

Research output: Contribution to journalArticle

Abstract

Ocular albinism type 1 (OA1) is an inherited disorder characterized by severe reduction of visual acuity, photophobia, and retinal hypopigmentation. Ultrastructural examination of skin melanocytes and of the retinal pigment epithelium reveals the presence of macromelanosomes, suggesting a defect in melanosome biogenesis. The gene responsible for OA1 is exclusively expressed in pigment cells and encodes a predicted protein of 404 aa displaying several putative transmembrane domains and sharing no similarities with previously identified molecules. Using polyclonal antibodies we have identified the endogenous OA1 protein in retinal pigment epithelial cells, in normal human melanocytes and in various melanoma cell lines. Two forms of the OA1 protein were identified by Western analysis, a 60-kDa glycoprotein and a doublet of 48 and 45 kDa probably corresponding to unglycosylated precursor polypeptides. Upon subcellular fractionation and phase separation with the nonionic detergent Triton X-114, the OA1 protein segregated into the melanosome-rich fraction and behaved as an authentic integral membrane protein. Immunofluorescence and immunogold analyses on normal human melanocytes confirmed the melanosomal membrane localization of the endogenous OA1 protein, consistent with its possible involvement in melanosome biogenesis. The identification of a novel melanosomal membrane protein involved in a human disease will provide insights into the mechanisms that control the cell-specific pathways of subcellular morphogenesis.

Original languageEnglish
Pages (from-to)9055-9060
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume93
Issue number17
DOIs
Publication statusPublished - Aug 20 1996

ASJC Scopus subject areas

  • Genetics
  • General

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