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Proteomic Analysis of Early Melanosomes: Identification of Novel Melanosomal Proteins

Venkatesha Basrur,^† Feng Yang,^‡ Tsuneto Kushimoto,^† Youichiro Higashimoto,^† Ken-ichi Yasumoto,^† Julio Valencia,^§ Jacqueline Muller, Wilfred D. Vieira,^† Hidenori Watabe,^† Jeffrey Shabanowitz,^‡ Vincent J. Hearing,^† Donald F. Hunt, and Ettore Appella*^†

Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, Maryland 20852 and Pathology Section, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892

Journal of Proteome Research, 2003, 2 (1), pp 69–79

DOI: 10.1021/pr025562r

Publication Date (Web): November 8, 2002

†

Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health.

V.B. and F.Y. contributed equally to this work.

‡

Department of Chemistry, University of Virginia.

Center for Biologics Evaluation and Research, Food and Drug Administration.

Pathology Section, National Heart, Lung and Blood Institute, National Institutes of Health.

Department of Chemistry and Pathology, University of Virginia.

To whom correspondence should be addressed. Ettore Appella, M. D., Laboratory of Cell Biology, Building 37, Room 1B03, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 USA. Phone: (301) 402−4177. Fax: (301) 496−7220. Email: appellae@pop.nci.nih.gov.

Abstract

Melanin is a heterogeneous biopolymer produced only by specific cells termed melanocytes, which synthesize and deposit the pigment in specialized membrane-bound organelles known as melanosomes. Although melanosomes have been suspected of being closely related to lysosomes and platelets, the total number of melanosomal proteins is still unknown. Thus far, six melanosome-specific proteins have been identified, and the challenge is to characterize the complete proteome of the melanosome to further understand its mechanism of biogenesis. In this report, we used mass spectrometry and subcellular fractionation to identify protein components of early melanosomes. Using this approach, we have identified all 6 of the known melanosome-specific proteins, 56 proteins that are shared with other organelles, and confirmed the presence of 6 novel melanosomal proteins using western blotting and by immunohistochemistry.

Keywords: melanoma • proteomics • melanosome

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