The group led by Duarte Barral, Membrane Traffic in Disease lab, describes a new way of regulating melanin, elucidating the transfer of pigment between human skin cells.
The study was published in the journal JID Innovations and was fully developed at NOVA Medical School, with PhD student Luís Cabaço being the first author.
The research involves the release of melanin, in complexes called melanosomes, from the cells where melanin is produced (melanocytes), through a process called exocytosis. Melanin is then transfered to another type of cells, the keratinocytes, where the pigment will accumulate and create protection against UV radiation. The group had already described an exocytosis and transfer pathway involving the RAB11B protein but now present an alternative method that is moderated by another protein from the same family, RAB3A.
"Our work unveiled that the molecule RAB3A is recruited to melanosomes in response to keratinocyte-derived soluble molecules and stimulates melanin release from melanocytes", says Duarte Barral about this investigation, reinforcing that "this knowledge is important to better understand how the skin pigmentary system can adapt to stress conditions such as chronic ultraviolet radiation exposure or certain pathologic conditions like skin inflammatory diseases, by enhancing the production and transfer of melanin from melanocytes to keratinocytes".
Regarding the identification of soluble molecules, he claims it to be "the '1 million dollar' question. Intriguingly, none of the currently known keratinocyte-derived soluble molecules that stimulate melanin synthesis by melanocytes seems to stimulate melanin release, as observed by us in this study". But this widentification of these stimulating molecules will become the next focus of this group's investigation, so don't miss the next chapters.
The original article, "Rab3a Regulates Melanin Exocytosis and Transfer Induced By Keratinocyte-Conditioned Medium" is available online.
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