title: The fate of SPE B after internalization and its implication in SPEB-induced apoptosis.
abstract: 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.
authors: Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan, Taiwan.
authors: Chia-Wen
authors: CW
authors: Chang
authors: Wan-Hua
authors: WH
authors: Tsai
authors: Woei-Jer
authors: WJ
authors: Chuang
authors: Yee-Shin
authors: YS
authors: Lin
authors: Jiunn-Jong
authors: JJ
authors: Wu
authors: Ching-Chuan
authors: CC
authors: Liu
authors: Pei-Jane
authors: PJ
authors: Tsai
authors: Ming-T
authors: MT
authors: Lin
mesh_terms: 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
chemical_list: D001426:Bacterial Proteins; D005098:Exotoxins; C027951:erythrogenic toxin