Epitope mapping of the melanosomal matrix protein gp100 (PMEL17). Rapid processing in the endoplasmic reticulum and glycosylation in the early Golgi compartment

Ken Ichi Yasumoto, Hidenori Watabe, Julio C. Valencia, Tsuneto Kushimoto, Takeshi Kobayashi, Ettore Appella, Vincent J. Hearing

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)

Abstract

Melanosomes, specific organelles produced only by melanocytes, undergo a unique maturation process that involves their transition form amorphous rounded vesicles to fibrillar ellipsoid organelles, during which they move from the perinuclear to the distal areas of the cells. This depends upon the trafficking and processing of gp100 (also known as Pmel17 and the silver protein), a protein of great interest, because it elicits immune responses in melanoma patients but in which specific function(s) remains elusive. In this study, we have used biochemical and immunochemical approaches to more critically assess the synthesis, processing, glycosylation, and trafficking of gp100. We now report that gp100 is processed and sorted in a manner distinct from other melanosomal proteins (such as tyrosinase, Tyrp1 and Dct) and is predominantly delivered directly to immature melanosomes following its rapid processing in the endoplasmic reticulum and cis-Golgi. Following its arrival, gp100 is cleaved at the amino and at the carboxyl termini in a series of specific steps that result in the reorganization of immature melanosomes to the fibrillar mature melanosomes. Once this structural reorganization occurs, melanogenic enzymes begin to be targeted to the melanosomes, which are then competent to synthesize melanin pigment.

Original languageEnglish
Pages (from-to)28330-28338
Number of pages9
JournalJournal of Biological Chemistry
Volume279
Issue number27
DOIs
Publication statusPublished - 2004 Jul 2

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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