Differential regulation of caspase-1 activation, pyroptosis, and autophagy via Ipaf and ASC in Shigella-infected macrophages

作者：Suzuki Toshihiko^*; Franchi Luigi; Toma Claudia; Ashida Hiroshi; Ogawa Michinaga; Yoshikawa Yuko; Mimuro Hitomi; Inohara Naohiro; Sasakawa Chihiro; Nunez Gabriel

来源：PLoS Pathogens, 2007, 3(8): 1082-1091.

DOI：10.1371/journal.ppat.0030111

Shigella infection, the cause of bacillary dysentery, induces caspase-1 activation and cell death in macrophages, but the precise mechanisms of this activation remain poorly understood. We demonstrate here that caspase-1 activation and IL-1 beta processing induced by Shigella are mediated through Ipaf, a cytosolic pattern-recognition receptor of the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family, and the adaptor protein apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC). We also show that Ipaf was critical for pyroptosis, a specialized form of caspase-1-dependent cell death induced in macrophages by bacterial infection, whereas ASC was dispensable. Unlike that observed in Salmonella and Legionella, caspase-1 activation induced by Shigella infection was independent of flagellin. Notably, infection of macrophages with Shigella induced autophagy, which was dramatically increased by the absence of caspase-1 or Ipaf, but not ASC. Autophagy induced by Shigella required an intact bacterial type III secretion system but not VirG protein, a bacterial factor required for autophagy in epithelial-infected cells. Treatment of macrophages with 3-methyladenine, an inhibitor of autophagy, enhanced pyroptosis induced by Shigella infection, suggesting that autophagy protects infected macrophages from pyroptosis. Thus, Ipaf plays a critical role in caspase-1 activation induced by Shigella independently of flagellin. Furthermore, the absence of Ipaf or caspase-1, but not ASC, regulates pyroptosis and the induction of autophagy in Shigella-infected macrophages, providing a novel function for NLR proteins in bacterial -host interactions.

• 出版日期2007-8
• 单位河北医科大学