Entamoeba histolytica Cysteine Proteinase 5 Binds Integrin on Colonic Cells and Stimulates NFκB-mediated Pro-inflammatory Responses

Integrins are important mammalian receptors involved in normal cellular functions and the pathogenesis of inflammation and disease. Entamoeba histolytica is a protozoan parasite that colonizes the gut, and in 10% of infected individuals, causes amebic colitis and liver abscess resulting in 10(5) deaths/year. E. histolytica-induced host inflammatory responses are critical in the pathogenesis of the disease, yet the host and parasite factors involved in disease are poorly defined. Here we show that pro-mature cysteine proteinase 5 (PCP5), a major virulent factor that is abundantly secreted and/or present on the surface of ameba, binds via its RGD motif to alpha(V)beta(3) integrin on Caco-2 colonic cells and stimulates NF kappa B-mediated pro-inflammatory responses. PCP5 RGD binding to alpha(V)beta(3) integrin triggered integrin-linked kinase(ILK)-mediated phosphorylation of Akt473 that bound and induced the ubiquitination of NF-kappa B essential modulator (NEMO). As NEMO is required for activation of the IKK alpha-IKK beta complex and NF kappa B signaling, these events markedly up-regulated pro-inflammatory mediator expressions in vitro in Caco-2 cells and in vivo in colonic loop studies in wild-type and Muc2(-/-) mice lacking an intact protective mucus barrier. These results have revealed that EhPCP5 RGD motif is a ligand for alpha(V)beta(3) integrin-mediated adhesion on colonic cells and represents a novel mechanism that E. histolytica trophozoites use to trigger an inflammatory response in the pathogenesis of intestinal amebiasis.