Yomiuri: Melanin transfer process found by Japanese team
That explanation may be too technical so here it is without the jargon:The Institute of Physical and Chemical Research (Riken) has uncovered substances that transfer melanin pigment between cells, a discovery [which] could lead to the development of medicines that could help maintain skin fairness and keep hair from turning gray. .
...Riken found two substances that work together to attach melanin pigments to proteins in the transfer process. The substances are protein labeled Rab27A and Slac2-a.
..."Existing skin lightening cosmetics mainly inhibit melanin synthesis. In the future, new medicines are expected to be developed that can keep melanin pigments from being delivered to skin and hair cells," said Mitsunori Fukuda, who heads the institute's Fukuda Initiative Research Unit.
Rab27A-binding protein Slp2-a is required for peripheral melanosome distribution and elongated cell shape in melanocytes
The synaptotagmin-like protein (Slp) family is implicated in regulating Rab27A-mediated membrane transport, but how it might do this is unknown. Here we report that Slp2-a, a previously uncharacterized Rab27A-binding protein in melanocytes, controls melanosome distribution in the cell periphery and regulates the morphology of melanocytes. Slp2-a is the most abundantly expressed of the Slp- and Slac2-family proteins in melanocytes and colocalizes with Rab27A on melanosomes. Knockdown of endogenous Slp2-a protein by small-interfering RNAs (siRNAs) markedly reduced the number of melanosomes in the cell periphery of mouse melanocytes ('peripheral dilution'). Expression of siRNA-resistant Slp2-a (Slp2-aSR) rescued the peripheral dilution of melanosomes induced by Slp2-a siRNAs, but Slp2-aSR mutants, which failed to interact with either phospholipids or Rab27A, did not. Loss of Slp2-a protein also induced a change in melanocyte morphology, from their normal elongated shape to a more rounded shape, which depended on the phospholipid-binding activity of Slp2-a, but not on its Rab27A-binding activity. By contrast, knockdown of Slac2-a (also called melanophilin), another Rab27A-binding protein in melanocytes, caused perinuclear aggregation of melanosomes alone without altering cell shape. These results reveal the differential and sequential roles of Rab27A-binding proteins in melanosome transport in melanocytes.
