The fate of SPE B after internalization and its implication in SPEB-induced apoptosis |
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Authors: | Chia-Wen Chang Wan-Hua Tsai Woei-Jer Chuang Yee-Shin Lin Jiunn-Jong Wu Ching-Chuan Liu Pei-Jane Tsai Ming-T Lin |
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Institution: | (1) Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan, Taiwan;(2) Biochemistry, National Cheng Kung University Medical College, Tainan, Taiwan;(3) Microbiology and Immunology, National Cheng Kung University Medical College, Tainan, Taiwan;(4) Medical Laboratory Science and Biotechnology, National Cheng Kung University Medical College, Tainan, Taiwan;(5) Department of Pediatrics, National Cheng Kung University Medical College, Tainan, Taiwan;(6) Institute of Medical Sciences, School of Medicine, Tzu Chi University, Hualien, 97004, Taiwan |
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Abstract: | Summary After streptococcal pyrogenic exotoxin B (SPE B) induces apoptosis, its fate is unknown. Using confocal time-course microscopy
at 37 °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. |
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Keywords: | A549 cell apoptosis clathrin internalization SPE B |
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