[ODP-114] A new endoplasmic stress mediator, KLHDC7B, increased Harakiri in SubAB-induced apoptosis
Recently, the incidence of LEE-negative EHEC-mediated disease is increasing globally. Subtilase cytotoxin (SubAB) is released by some LEE-negative EHEC strains. SubAB-mediated BiP cleavage induces apoptosis by ER stress. The apoptotic signaling pathway remains unknown. In this study, RNA-seq analysis demonstrated that SubAB dramatically increased the expression of Kelch domain containing 7B (KLHDC7B). We investigated the role of KLHDC7B in the SubAB-induced apoptotic pathway. SubAB-increased KLHDC7B mRNA expression was detected after 12 h of incubation with HeLa cells. KLHDC7B expression was downregulated by knockdown of ER stress senser protein PERK, and transcription factors, e.g., CHOP, ATF4, CEBPB. KLHDC7B knockdown suppressed SubAB-stimulated CHOP expression, poly(ADP-ribose) polymerase cleavage, and cytotoxicity. The over-expressed KLHDC7B was localized to the nucleus and cytosolic fractions. Further, we performed RNA-seq to analyze the effect of KLHDC7B knockdown on apoptosis induced by SubAB, and found that the gene encoding for the pro-apoptotic Bcl-2 family protein, Harakiri, was upregulated in SubAB-treated control cells. However, this effect was not observed in SubAB-treated KLHDC7B-knockdown cells. Therefore, we concluded that SubAB-induced KLHDC7B regulates HRK expression, which is an essential for apoptosis in toxin-mediated ER stress.