TDAG51 overexpression mediates proximal tubule epithelial cell apoptosis through its accumulation in the nucleus

T‐cell death associated gene 51 (TDAG51) overexpression induces apoptosis in many cell types. Sequence analysis revealed that TDAG51 contains a putative nuclear export signal (NES), 78 VASLEPPVKL 87 . We hypothesize that TDAG51‐induced apoptosis is mediated through its nuclear accumulation. Leptomycin B (LMB) was employed to inhibit the nuclear export of TDAG51 in HK2 cells, a proximal tubule cell line. An EC50 of 0.8 ng/mL for LMB was calculated using the known NES of Protein Kinase A Inhibitior (PKI). Doses of 0, 1 and 5 ng/mL LMB were applied to determine any increase in TDAG51 nuclear localization. Apoptotic cell death was evaluated with TUNEL assays and nuclear to cytoplasmic ratios of TDAG51 expression were measured confocally. Both 1 and 5 ng/mL LMB induced nuclear localization of TDAG51 endogenously or ectopically expressed. The 1 ng/mL dose of LMB resulted in significantly greater apoptotic cell death in TDAG51‐transfected HK2 cells than in GFP controls. However, the 5 ng/ml dose of LMB caused an increase in apoptosis independent of TDAG51 overexpression. We assessed nuclear localization of TDAG51 under Staurosporine (STS) stimuli. Treatment with 2 μM STS showed a significant increase in apoptosis and nuclear to cytoplasmic ratios compared to vehicle‐treated controls. Our results demonstrate an increase in the nuclear accumulation of TDAG51 under apoptotic conditions. Supported by the CIHR, MOP‐67116 .