(A, B) WT melanocytes were treated with either 150nM thapsigargin or 10μg/mL tunicamycin and (C) mutant melanocytes with 150nM thapsigargin for 24 hours. Cells were lysed, and proteins harvested at the indicated time points. Extracts were normalized for protein concentration prior to analysis. Actin is shown as a loading control. Expression of (A) Expression of Perk and its downstream effectors Atf4, CHOP and Gadd34, as well as (B) tyrosinase were monitored by Western blot analysis in WT cells, while (C) Perk phosphorylation and CHOP expression were monitored in mutant cells.