Journal of Cell Science 115, e705-e705 (2002)
© 2002 The Company of Biologists Limited
Melanosome transfer
Melanosomes are specialized organelles that produce the photoprotective
pigment melanin in skin. Synthesized in melanocytes, they are captured at
dendritic tips by the motor protein myosin Va and the GTPase Rab27a. These
organelles are subsequently transferred to surrounding keratinocytes - their
ultimate destination - but the mechanism involved has proved elusive. Glynis
Scott and co-workers now reveal how transfer might occur: through filopodia
(see p. 1441). Employing
time-lapse digital imaging and electron microscopy, they observe that
melanocytes extend filopodia that contact neighbouring keratinocytes and that
these filopodia act as conduits for melanosome transfer. The authors also
demonstrate that expression of Cdc42 (a GTPase known to induce filopodia)
produces a dendritic phenotype in melanocytes and more melanosome-containing
filopodia. In addition, they show that melanosome-enriched fractions from
human melanocytes contain the Cdc42 effectors PAK1 and N-WASP. Given that
Cdc42 is activated following UV-induced release of interleukin 1 and tumour
necrosis factor
, it could be part of a mechanism that upregulates
melanosome transfer in response to UV irradiation.
Related articles in JCS:
- Filopodia are conduits for melanosome transfer to keratinocytes
- Glynis Scott, Sonya Leopardi, Stacey Printup, and Brian C. Madden
JCS 2002 115: 1441-1451.
[Abstract]
[Full Text]