Model of ion channel-mediated regulation of melanosome pH and melanogenesis.  TPC2 mediates the major melanosomal Na+ conductance to increase melanosome membrane potential (Ψm, Ψm=Vcytosol – Vlumen) and provide a counter cation to enhance vacuolar ATPase (V-ATPase) activity and increase the acidity of the melanosome lumen, thus reducing the activity of the key melanogenic enzyme tyrosinase (TYR). Additionally, the major melanosomal anion channel mediated by OCA2 expression transports Cl− into the cytoplasm to make the melanosome membrane voltage more negative, thereby decreasing V-ATPase-mediated H+ transport and luminal acidity, which enhances the activity tyrosinase and melanin production.  Oancea et al 2016.
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