Keratinocyte-derived laminin-332 promotes melanin synthesis via regulation of tyrosine uptake [Cell Biology]

June 20th, 2014 by Chung, H., Jung, H., Lee, J.-h., Oh, H. Y., Kim, O. B., Han, I.-O., Oh, E.-S.

Melanocytes, which produce the pigment melanin, are known to be closely regulated by neighboring keratinocytes. However, how keratinocytes regulate melanin production is unclear. Here, we report that melanin production in melanoma cells (B16F10 and MNT-1) was markedly increased on a keratinocyte-derived extracellar matrix (ECM) compared to a melanoma cell-derived ECM. siRNA-mediated reduction of keratinocyte-derived laminin-332 expression decreased melanin synthesis in melanoma cells, and laminin-332, but not fibronectin, enhanced melanin content and α-melanocyte stimulating hormone-regulated melanin production in melanoma cells. Similar effects were observed in human melanocytes. Interestingly, however, laminin-332 did not affect the expression or activity of tyrosinase. Instead, laminin-332 promoted uptake of extracellular tyrosine and subsequently increased intracellular levels of tyrosine in both melanocytes and melanoma cells. Taken together, these data strongly suggest that keratinocyte-derived laminin-332 contributes to melanin production by regulating tyrosine uptake