Two‐pore channel 2 is required for soluble adenylyl cyclase‐dependent regulation of melanosomal pH and melanin synthesis

Abstract

Melanosomal pH is important for the synthesis of melanin as the rate‐limiting enzyme, tyrosinase, is very pH‐sensitive. The soluble adenylyl cyclase (sAC) signaling pathway was recently identified as a regulator of melanosomal pH in melanocytes; however, the melanosomal proteins critical for sAC‐dependent regulation of melanosomal pH were undefined. We now systematically examine four well‐characterized melanosomal membrane proteins to determine whether any of them are required for sAC‐dependent regulation of melanosomal pH. We find that OA1, OCA2, and SLC45A2 are dispensable for sAC‐dependent regulation of melanosomal pH. In contrast, TPC2 activity is required for sAC‐dependent regulation of melanosomal pH and melanin synthesis. In addition, activation of TPC2 by NAADP‐AM rescues melanosomal pH alkalinization and reduces melanin synthesis following pharmacologic or genetic inhibition of sAC signaling. These studies establish TPC2 as a critical melanosomal protein for sAC‐dependent regulation of melanosomal pH and pigmentation.