Streptococcal pyrogenic exotoxin B-induced apoptosis in A549 cells is mediated through alpha(v)beta(3) integrin and Fas.
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 alpha(v)beta(3) 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 alpha(v)beta(3). Anti-alpha(v)beta(3) 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-alpha(v)beta(3) 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 alpha(v)beta(3), but not of Fas, was decreased. The decreased alpha(v)beta(3) level was restored by treatment with the proteasome inhibitor MG132, suggesting a SPE B-mediated endocytosis of integrin alpha(v)beta(3) via the ubiquitin-proteasome system. Taken together, our results demonstrate that SPE B-induced apoptosis is mediated through alpha(v)beta(3) integrin and Fas in a synergistic manner.
Tsai
Wan-Hua
WH
Institute of Medical Sciences, School of Medicine, Tzu Chi University, Hualien 970, Taiwan.
Chang
Chia-Wen
CW
Lin
Yee-Shin
YS
Chuang
Woei-Jer
WJ
Wu
Jiunn-Jong
JJ
Liu
Ching-Chuan
CC
Tsai
Pei-Jane
PJ
Lin
Ming T
MT
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001426:Bacterial Proteins / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005098:Exotoxins / Q000494:pharmacology*; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D011485:Protein Binding; D019014:fas Receptor / Q000378:metabolism*
D001426:Bacterial Proteins; D005098:Exotoxins; C491901:FAS protein, human; D039302:Integrin alphaVbeta3; C027951:erythrogenic toxin; D019014:fas Receptor