The team lead by Duarte Barral developed an in vitro uptake assay using melanocores secreted by melanocytes and further demonstrated that silencing an early endocytic regulator (Rab5b), but not the late endocytic regulators (Rab7a or Rab9a), significantly impairs melanocore uptake by keratinocytes. Moreover, the team found that, after uptake, melanin accumulates in compartments that are positive for both early and late endocytic markers but are not either highly degradative or acidic organelles. Duarte Barral and his team propose that melanocore uptake leads to storage of melanin within keratinocytes in hybrid endocytic compartments that are not highly acidic or degradative. By avoiding lysosomal degradation, these specialized endosomes may allow melanin to persist within keratinocytes for long periods.
Article available online: Melanin Transferred to Keratinocytes Resides in Nondegradative Endocytic Compartments.