Inhibition of apoptosis in Cryptosporidium parvum-infected intestinal epithelial cells is dependent on survivin.
Cryptosporidium parvum is an obligate intracellular protozoan capable of causing severe diarrheal disease in a wide variety of mammals, including humans. C. parvum infection has been associated with induction of apoptosis in exposed epithelial cells, and we now demonstrate that apoptosis is restricted to a subset of cells actively infected with C. parvum. Approximately 20% of the infected cells underwent apoptosis within 48 h of infection, suggesting that the majority of the infected cells are rescued from apoptosis. C. parvum infection resulted in low-level activation of multiple members of the caspase family, including caspase-2, -3, -4, -6, -8, and -9. The kinetics of caspase activation correlated with apoptosis over a 48-h time course. Pan caspase inhibitors reduced apoptosis of epithelial cells infected by C. parvum. Furthermore, C. parvum infection inhibited staurosporine-induced apoptosis and caspase-3/7 activation at 24 h and 48 h. Infection with C. parvum led to upregulation of genes encoding inhibitors of apoptosis proteins (IAPs), including c-IAP1, c-IAP2, XIAP, and survivin. Knockdown of survivin gene expression, but not that of c-IAP1, c-IAP2, or XIAP expression, increased caspase-3/7 activity as well as apoptosis of infected cells and decreased C. parvum 18S rRNA levels. These data suggest that the apoptotic response of infected intestinal epithelial cells is actively suppressed by C. parvum via upregulation of survivin, favoring parasite infection.
Liu
Jin
J
Department of Veterinary and Biomedical Sciences, University of Minnesota, 1988 Fitch Ave, no. 295, St. Paul, MN 55108, USA.
Enomoto
Shinichiro
S
Lancto
Cheryl A
CA
Abrahamsen
Mitchell S
MS
Rutherford
Mark S
MS
D000818:Animals; D017209:Apoptosis; D061945:Caspase Inhibitors; D002460:Cell Line; D016785:Cryptosporidium parvum / Q000502:physiology*; D004847:Epithelial Cells / Q000469:parasitology; D020868:Gene Silencing; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000096:biosynthesis / Q000235:genetics; D007413:Intestinal Mucosa / Q000469:parasitology*; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis* / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D000077022:Survivin
C107489:BIRC5 protein, human; D061945:Caspase Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D000077022:Survivin