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Infection and Immunity, October 2000, p. 5502-5508, Vol. 68, No. 10
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Tripeptidyl Peptidase II Promotes Maturation of Caspase-1 in Shigella flexneri-Induced Macrophage Apoptosis

Hubert Hilbi,* Robyn J. Puro, and Arturo Zychlinsky

The Skirball Institute, Department of Microbiology and Kaplan Cancer Center, New York University School of Medicine, New York, New York 10016

Received 4 April 2000/Returned for modification 1 June 2000/Accepted 27 June 2000

The invasive enteropathogenic bacterium Shigella flexneri activates apoptosis in macrophages. Shigella-induced apoptosis requires caspase-1. We demonstrate here that tripeptidyl peptidase II (TPPII), a cytoplasmic, high-molecular-weight protease, participates in the apoptotic pathway triggered by Shigella. The TPPII inhibitor Ala-Ala-Phe-chloromethylketone (AAF-cmk) and clasto-lactacystin beta -lactone (lactacystin), an inhibitor of both TPPII and the proteasome, protected macrophages from Shigella-induced apoptosis. AAF-cmk was more potent than lactacystin and irreversibly blocked Shigella-induced apoptosis by 95% at a concentration of 1 µM. Conversely, peptide aldehyde and peptide vinylsulfone proteasome inhibitors had little effect on Shigella-mediated cytotoxicity. Both AAF-cmk and lactacystin prevented the maturation of pro-caspase-1 and its substrate pro-interleukin 1beta in Shigella-infected macrophages, indicating that TPPII is upstream of caspase-1. Neither of these compounds directly inhibited caspase-1. AAF-cmk and lactacystin did not impair macrophage phagocytosis or the ability of Shigella to escape the macrophage phagosome. TPPII was also found to be involved in apoptosis induced by ATP and the protein kinase inhibitor staurosporine. We propose that TPPII participates in apoptotic pathways.

* Corresponding author. Mailing address: Department of Microbiology, Columbia University, Hammer Health Science Center, 701 West 168th St., New York, NY 10032. Phone: (212) 305-1482. Fax: (212) 305-1468. E-mail: hilbi{at}cuccfa.ccc.columbia.edu.

Infection and Immunity, October 2000, p. 5502-5508, Vol. 68, No. 10
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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