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Infection and Immunity, October 2000, p. 5502-5508, Vol. 68, No. 10
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
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
-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 1
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.
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