p20BAP31 induces cell apoptosis via both ROS/JNK mitochondrial pathway and AIF caspase-independent pathway

Abstract

Abstract Background B-cell receptor associated protein 31 (BAP31) is a polytopic integral endoplasmic reticulum (ER) membrane protein. During cell apoptosis, the c-terminal of BAP31 was cleaved by caspase-8, generates the residual 20kDa proteolytic fragment (p20BAP31), which not only induces cell apoptosis, but also initiates a paraptosis-like cell death pathway when expressed ectopically. This property of inducing cell apoptosis through multiple pathways makes p20BAP31 potentially valuable in the research of anti-tumor therapy. However, the underlying mechanisms of p20Bap31 on cell apoptosis remain to be elucidated in detail. Therefore, it is very important to evaluate the efficiency of p20BAP31-induced apoptosis in different types of cells, and to investigate the molecular mechanisms of p20BAP31 on cell apoptosis. Methods Cell viability and colony formation assays were performed to examine the antigrowth effects of p20Bap31 in HCT116 cells. Wound-healing assay was conducted to assess cell migration capacity. Cell cycle and apoptosis were investigated by flow cytometry and verified by immunoblotting. AIF translocate from the mitochondria to the nuclei was verified by immunoblotting and immunofluorescence assay. Results We found that overexpression of p20BAP31 can indeed induce apoptosis, and has a much greater sensitivity in human colorectal carcinoma cell line (HCT116). Furthermore, the overexpression of p20BAP31 could inhibit cell proliferation by causing S phase arrest, the migratory ability was also obviously inhibited. The further study revealed that p20BAP31 reduced mitochondrial membrane potential (MMP) with a significant increase in reactive oxygen species (ROS) levels, accompanying with the activation of the MAPK signaling pathway. The mechanism investigation indicated that p20BAP31 could induce mitochondrial-dependent apoptosis by activating ROS/JNK signaling pathway. Importantly, we found that p20BAP31 may also induce caspase-independent apoptosis by promoting the nuclear translocation of apoptosis inducing factor (AIF). Conclusions p20BAP31 induced cell apoptosis via both ROS/JNK mitochondrial pathway and AIF caspase-independent pathway. These effects are especially pronounced in HCT116 cell line, implied that p20BAP31 may exert as a potent drug target for the prevention and treatment of colorectal cancer (CRC).