The gene TDAG51 facilitates the phosphorylation of eIF2α in mouse embryonic fibroblasts

Unfolded protein accumulation in the endoplasmic reticulum (ER) results in ER stress. This causes the binding of GRP78 to unfolded proteins, auto‐phosphorylation of PERK and the phosphorylation of eIF2α, leading to changes in the rate and characteristics of protein synthesis, including an upregulation of CHOP/GADD153 expression. TDAG51 is an ER stress response gene and has been shown to regulate translation. We hypothesized that TDAG51 influences protein translation by mediating the phosphorylation of eIF2α. Mouse embryonic fibroblasts (MEFs) treated with ER stressors, tunicamycin (Tm; 5 μg/ml) or thapsigargin (Tg; 1 μM), or a phosphorylated eIF2α dephosphorylation inhibitor, salubrinal (30 μM), or combined treatments demonstrated an increase in eIF2α phosphorylation. TDAG51 −/− MEFs showed a decrease in eIF2α phosphorylation to drug vehicle, Tm plus salubrinal, Tg and Tg plus salubrinal treatment. It was determined that TDAG51 −/− MEFs have reduced CHOP/GADD153 expression compared to wild type cells. Therefore, TDAG51 knockout may regulate CHOP/GADD153 expression by reducing the phosphorylation of eIF2α, which in turn may lead to decreased expression of GADD34, essentially inhibiting the GADD34/PP1 dephosphorylation complex. This mechanism is also being investigated through the use of siRNA‐mediated knockdown. Supported by CIHR MOP‐67116.