Procaspase 8 and Bax are up-regulated by distinct pathways in Streptococcal pyrogenic exotoxin B-induced apoptosis.
We have previously identified integrin alpha(v)beta(3) and Fas as receptors for the streptococcal pyrogenic exotoxin B (SPE B), and G308S, a mutant of SPE B that binds to Fas only. In the current study we found that after binding to alpha(v)beta(3), SPE B stimulated the tyrosine phosphorylation of JAK2 and STAT1. STAT1 tyrosine phosphorylation was inhibited by a JAK2 inhibitor, AG490, short interfering RNA (siRNA) silencing of JAK2, and anti-alpha(V)beta(3) antibody. AG490 also decreased the binding of tyrosine-phosphorylated STAT1 to the procaspase 8 promoter, decreasing procaspase 8 expression, suggesting that SPE B up-regulates procaspase 8 expression via the JAK2/STAT1 pathway. Alternatively, both SPE B and G308S increased STAT1 phosphorylation at serine 727, which was inhibited by anti-Fas antibody, a p38 inhibitor, SB203580, and siRNA silencing of p38. In addition, SPE B and G308S increased binding of serine-phosphorylated STAT1 to the Bax promoter and Bax expression, which was decreased by SB203580. SPE B and G308S-stimulated Bax expression was also inhibited by anti-Fas antibody. These findings suggest that Fas mediate SPE B-induced Bax expression through p38. Silencing of JAK2 or p38 by siRNA blocked procaspase 8 expression, whereas only p38 siRNA decreased Bax expression. Furthermore, JAK2 inhibition and p38 inhibition reduced SPE B-induced apoptosis, but only p38 inhibition blocked G308S-induced apoptosis.
Chang
Chia-Wen
CW
Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan, 701 Taiwan.
Tsai
Wan-Hua
WH
Chuang
Woei-Jer
WJ
Lin
Yee-Shin
YS
Wu
Jiunn-Jong
JJ
Liu
Ching-Chuan
CC
Tsai
Pei-Jane
PJ
Lin
Ming T
MT
D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001426:Bacterial Proteins / Q000235:genetics / Q000494:pharmacology*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005098:Exotoxins / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015151:Immunoblotting; D039302:Integrin alphaVbeta3 / Q000276:immunology; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D050505:Mutant Proteins / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D034622:RNA Interference; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020032:Tyrphostins / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000276:immunology
D000906:Antibodies; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D005098:Exotoxins; D007093:Imidazoles; D039302:Integrin alphaVbeta3; D050505:Mutant Proteins; D011725:Pyridines; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D051028:bcl-2-Associated X Protein; C027951:erythrogenic toxin; D019014:fas Receptor; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D053181:Caspase 8; C093642:SB 203580