Melanosome transfer to and translocation in the keratinocyte

Authors

  • Raymond E. Boissy

    Corresponding author
    1. Department of Dermatology & Cell Biology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
      Raymond E. Boissy, Department of Dermatology & Cell Biology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0592, USA.
      Tel: +1 513 558 6242
      Fax: +1 513 558 0198
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Raymond E. Boissy, Department of Dermatology & Cell Biology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0592, USA.
Tel: +1 513 558 6242
Fax: +1 513 558 0198
E-mail: boissyre@ucmail.uc.edu

Abstract

Abstract Complexion coloration in humans is primarily regulated by the amount and type of melanin synthesized by the epidermal melanocyte. However, additional and equally contributing factors consist of (1) efficient transfer of melanin from the melanocytes to the neighboring keratinocytes and (2) distribution and degradation of the transferred melanosomes by the recipient keratinocytes. Once synthesized in the cell body of the epidermal melanocyte, pigmented melanosomes are translocated down the dendrites and captured at the dendritic tips via various cytoskeletal elements. Molecules recently identified that participate in this process consist of Rab27a, myosin-Va and melanophilin. Eventually, these peripherally localized melanosomes are transferred to keratinocytes by a presently undefined mechanism. The protease-activated receptor-2 (PAR-2) and unidentified surface lectins and glycoproteins facilitate this transfer process. Once incorporated into the keratinocytes, melanosomes are distributed individually or as clusters, aggregated towards the apical pole of the nucleus, and degraded as the keratinocytes undergo terminal differentiation and desquamation. Ultraviolet irradiation (UVR) can modulate the process of melanosome transfer from the melanocytes to the keratinocytes. UVR can upregulate expression of PAR-2 and lectin-binding receptors and increase phagocytic activity of cultured keratinocytes. Therefore, many cellular and molecular events that occur after melanogenesis contribute to skin color.

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