Calpain-dependent degradation of transcription factors and X-linked inhibitor of apoptosis (XIAP) in colon epithelial cells during cell death induced by Entamoeba histolytica (133.4)

Abstract

Abstract Entamoeba histolytica is a tissue-invasive protozoan parasite causing dysentery in human beings. During the infection in the colonic tissues, amoebic trophozoites have a capability to kill host cells via apoptosis or necrosis, which triggers IL-8-mediated acute inflammatory responses. However, signaling pathways involved in host cell death by E. histolytica is not fully defined. In this study, we examined whether calpain is closely involved in cleavage of transcription factors and XIAP, which are responsible for cell survival, during cell death of colon epithelial cells induced by live trophozoites of E. histolytica. Incubation with amoebic trophozoites induced PS externalization in CaCo2 cells in a time and dose-dependent manner. In addition, E. histolytica activated m-calpain and caspase-3 in CaCo2 cells. Moreover, incubation with amoeba resulted in marked degradation of STAT proteins (STAT1, 2, 3, 5, and 6), NF-¿B (p65 or p50), and XIAP in CaCo2 cells. However, I¿B, an inhibitor of NF-¿B, was not cleaved in CoCo2 cells following adherence of E. histolytica. Entamoeba-induced cleavage of STAT proteins, NF-kB, and XIAP was inhibited by pretreatment of cells with a cell permeable calpain inhibitor, calpeptin. Furthermore, calpeptin, but not z-VAD-fmk, reduced Entamoeba-induced DNA fragmentation in CoCo2 cells. These results suggest that calpain-mediated degradation of anti-apoptotic proteins, such as transcription factors and XIAP, is required for acceleration of cell death in colon epithelial cells induced by Entamoeba histolytica.