Figure 2.

Core signaling pathways associated with the regulation of melanogenesis in melanocytes. Genes encoding specific melanogenic enzymes, including tyrosinase and TRPs, are regulated by the MITF transcription factor, which is consequently regulated by a number of signaling pathways, including α-MSH/MC1R (orange), SCF/KIT (blue) and Wnt/frizzled (purple). Signal transduction is mediated by cAMP/PKA, RAS/MAPK and β catenin pathways. The cholinergic system is a negative regulator of melanogenesis. ACh, acetylcholine; AChE, acetylcholinesterase; AChR, acetylcholine receptor; α-MSH, α-melanocyte-stimulating hormone; cAMP, cyclic adenosine monophosphate; CREB, cAMP response element-binding protein; ERK, extracellular signal-regulated protein kinase; GSK3β, glycogen synthase kinase 3β; c-KIT, tyrosine kinase receptor; MAPK, mitogen-activated protein kinase; MC1R, melanocyte-specific melanocortin 1 receptor; MITF, microphthalmia-associated transcription factor; PKA, protein kinase A; PI3K, phosphatidylinositol 3-kinase; SCF, stem cell factor; TRPs, tyrosinase-related proteins; Wnt, wingless-related integration site.