The melanocytic protein Melan-A/MART-1 has a subcellular localization distinct from typical melanosomal proteins

Traffic. 2002 Sep;3(9):678-93. doi: 10.1034/j.1600-0854.2002.30909.x.


To delineate the role of the melanocyte lineage-specific protein Melan-A/MART-1 in melanogenic functions, a set of biochemical and microscopical studies was performed. Biochemical analysis revealed that Melan-A/MART-1 is post-translationally acylated and undergoes a rapid turnover in a pigmented melanoma cell line. Immunofluorescence and immunoelectron microscopy analyses indicated that Melan-A/MART-1 is mainly located in the Golgi area and only partially colocalizes with melanosomal proteins. Quantitative immunoelectron microscopy showed that the highest proportion of the cellular content of Melan-A/MART-1 was found in small vesicles and tubules throughout the cell, whereas the concentration was maximal in the Golgi region, particularly the trans-Golgi network. Substantial labeling was also present on melanosomes, endosomes, ER, nuclear envelope, and plasma membrane. In early endosomes, Melan-A was enriched in areas of the limiting membrane covered by a bi-layered coat, a structural characteristic of melanosomal precursor compartments. Upon melanosome maturation, Melan-A concentration decreased and its predominant localization shifted from the limiting membrane to internal vesicle membranes. In conjunction with its acylation, the high expression levels of Melan-A in the trans-Golgi network, in dispersed vesicles, and on the limiting membrane of premelanosomes indicate that the protein may play a role during the early stage of melanosome biogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Neoplasm
  • Electrophoresis, Polyacrylamide Gel
  • Golgi Apparatus / metabolism
  • Humans
  • MART-1 Antigen
  • Melanosomes / metabolism*
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Neoplasm Proteins / metabolism*
  • Skin / metabolism
  • Subcellular Fractions / metabolism*


  • Antigens, Neoplasm
  • MART-1 Antigen
  • MLANA protein, human
  • Neoplasm Proteins