The fate of SPE B after internalization and its implication in SPEB-induced apoptosis.
After streptococcal pyrogenic exotoxin B (SPE B) induces apoptosis, its fate is unknown. Using confocal time-course microscopy at 37 degrees C, we detected green fluorescence 20 min after adding FITC-SPE B. Orange fluorescence, an indication of co-localization of SPE B with lysosomes which were labeled with a red fluorescent probe, was maximal at 40 min and absent by 60 min. SPE B was co-precipitated with clathrin, which is consistent with endocytotic involvement. Western blotting assay also indicated that uptake of SPE B was maximal at 40 min and disappeared after 60 min. However, in the presence of chloroquine, a lysosome inhibitor, the uptake of SPE B was not detectable. The disappearance of TCA-precipitated FITC-SPE B was parallel to the appearance of TCA soluble FITC-SPE B; in the presence of chloroquine, however, no SPE B degradation occurred. Chloroquine increased the level of SPE B-induced apoptosis by inhibiting the degradation of SPE B. These results suggest that the internalization and degradation of SPE B in cells may be a host defense system that removes toxic substances by sacrificing the exposed cells.
Chang
Chia-Wen
CW
Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan, 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
D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D001426:Bacterial Proteins / Q000378:metabolism / Q000633:toxicity*; D002478:Cells, Cultured; D005098:Exotoxins / Q000378:metabolism / Q000633:toxicity*; D006801:Humans; D013297:Streptococcus pyogenes / Q000201:enzymology / Q000276:immunology
D001426:Bacterial Proteins; D005098:Exotoxins; C027951:erythrogenic toxin