Apoptotic signaling in cells with L101P and R280C mutations is activated by ER stress. (A) Immunoblotting on whole cell lysates from A549 cells transfected with pEYFP-N1/ABCA3 and densitometric analyses of (B) pro-caspase 4 and (C) cleaved caspase 4 demonstrated increased caspase 4 cleavage in cells expressing L101P and R280C mutations, as well as after TNFα treatment of A549 (25 ng/ml, 16 h) in comparison to WT and untreated A549. No significant changes in the pro-caspase 4 level in transfected cells with WT, R43L, R280C and L101P mutations were detected but pro-caspase 4 was slightly increased in transfected cells compared to A549 (B). * - unknown band. Six independent experiments were used for densitometric evaluation; * p < 0.05, ** p < 0.01.