Filopodia are conduits for melanosome transfer to keratinocytes

J Cell Sci. 2002 Apr 1;115(Pt 7):1441-51. doi: 10.1242/jcs.115.7.1441.

Abstract

Melanosomes are specialized melanin-synthesizing organelles critical for photoprotection in the skin. Melanosome transfer to keratinocytes, which involves whole organelle donation to another cell, is a unique biological process and is poorly understood. Time-lapse digital movies and electron microscopy show that filopodia from melanocyte dendrites serve as conduits for melanosome transfer to keratinocytes. Cdc42, a small GTP-binding protein, is known to mediate filopodia formation. Melanosome-enriched fractions isolated from human melanocytes expressed the Cdc42 effector proteins PAK1 and N-WASP by western blotting. Expression of constitutively active Cdc42 (Cdc42(V12)) in melanocytes co-cultured with keratinocytes induced a highly dendritic phenotype with extensive contacts between melanocytes and keratinocytes through filopodia, many of which contained melanosomes. These results suggest a unique role for filopodia in organelle transport and, in combination with our previous work showing the presence of SNARE proteins and rab3a on melanosomes, suggest a novel model system for melanosome transfer to keratinocytes.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biological Transport
  • Cells, Cultured
  • Humans
  • Image Processing, Computer-Assisted
  • Keratinocytes / metabolism*
  • Keratinocytes / ultrastructure
  • Melanosomes / metabolism*
  • Melanosomes / ultrastructure
  • Nerve Tissue Proteins / biosynthesis
  • Nerve Tissue Proteins / metabolism
  • Protein Kinases / biosynthesis
  • Protein Kinases / metabolism
  • Pseudopodia / physiology*
  • Pseudopodia / ultrastructure
  • Wiskott-Aldrich Syndrome Protein, Neuronal
  • cdc42 GTP-Binding Protein / metabolism

Substances

  • Nerve Tissue Proteins
  • WASL protein, human
  • Wiskott-Aldrich Syndrome Protein, Neuronal
  • Protein Kinases
  • protease activated kinase I
  • cdc42 GTP-Binding Protein