This Article Full Text Full Text (PDF) Other Versions of this Article: IAI.01162-07v1 76/4/1349    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Tsai, W.-H. Articles by Lin, M. T. PubMed PubMed Citation Articles by Tsai, W.-H. Articles by Lin, M. T.

Streptococcal Pyrogenic Exotoxin B-Induced Apoptosis in A549 Cells Is Mediated through _vβ₃ Integrin and Fas

Institute of Basic Medical Sciences,¹ Departments of Biochemistry,² Microbiology and Immunology,³ Medical Laboratory Science and Biotechnology,⁴ Pediatrics, National Cheng Kung University Medical College, Tainan, Taiwan,⁵ National Applied Research Laboratories, National Laboratory Animal Center, Taipei, Taiwan,⁶ Institute of Medical Sciences, School of Medicine, Tzu Chi University, Hualien, Taiwan⁷

Received 21 August 2007/ Returned for modification 4 October 2007/ Accepted 13 January 2008

Our previous work suggested that streptococcal pyrogenic exotoxin (SPE) B-induced apoptosis is mediated through a receptor-like mechanism. In this study, we have identified _vβ₃ and Fas as the SPE B receptors for this function. The SPE B fragment without the RGD motif and G308S, a SPE B mutant with the RSD motif, induced less apoptosis than did native SPE B, suggesting that the RGD motif is critical for SPE B-induced apoptosis. Fluorescein isothiocyanate-SPE B binding assays and immunoprecipitation analysis showed that SPE B specifically interacted with _vβ₃. Anti-_vβ₃ antibody partially inhibited SPE B-induced apoptosis but had no effect on G308S-induced apoptosis. In addition, Fas binding to SPE B was verified in an affinity column and an immunoprecipitation analysis. Anti-Fas antibody inhibited SPE B- and G308S-induced apoptosis in a dose-dependent manner, suggesting that Fas-mediated SPE B-induced apoptosis also occurs RGD independently. Both anti-_vβ₃ and anti-Fas antibodies synergistically inhibited SPE B-induced apoptosis. The apoptotic cascades were activated by SPE B and G308S, with a little delay by the latter. After SPE B binding, the cell surface level of _vβ₃, but not of Fas, was decreased. The decreased _vβ₃ level was restored by treatment with the proteasome inhibitor MG132, suggesting a SPE B-mediated endocytosis of integrin _vβ₃ via the ubiquitin-proteasome system. Taken together, our results demonstrate that SPE B-induced apoptosis is mediated through _vβ₃ integrin and Fas in a synergistic manner.

Published ahead of print on 28 January 2008.

Editor: A. Camilli