Clustering of Tir during enteropathogenic < i > E < /i > . < i > coli < /i > infection triggers calcium influx –dependent pyroptosis in intestinal epithelial cells

by Qiyun Zhong, Theodoros I. Roumeliotis, Zuza Kozik, Massiel Cepeda-Molero, Luis Ángel Fernández, Avinash R. Shenoy, Chris Bakal, Gad Frankel, Jyoti S. Choudhary Clustering of the enteropathogenicEscherichia coli (EPEC) type III secretion system (T3SS) effector translocated intimin receptor (Tir) by intimin leads to actin polymerisation and pyroptotic cell death in macrophages. The effect of Tir clustering on the viability of EPEC-infected intestinal epithelial cells (IECs) is unknown. We show that EPEC induces pyroptosis in IECs in a Tir-dependent but actin polymerisation-independent manner, which was enhanced by priming with interferon gamma (IFN γ). Mechanistically, Tir clustering triggers rapid Ca2+ influx, which induces lipopolysaccharide (LPS) internalisation, followed by activation of caspase-4 and pyroptosis. Knockdown of caspase-4 or gasdermin D (GSDMD), translocation of NleF, which blocks caspase-4 or chelation of extracellular Ca2+, inhibited EPEC-induced cell death. IEC lines with low endogenous abundance of GSDMD were resistant to Tir-induced cell death. Conversely, ATP-induced extracellular Ca2+ influx enhanced cell death, which confirmed the key regulatory role of Ca2+ in EPEC-induced pyroptosis. We reveal a novel mechanism through which infection with an extracellular pathogen leads to pyroptosis in IECs.
Source: PLoS Biology: Archived Table of Contents - Category: Biology Authors: Source Type: research