Subcellular localization of caspase-3 activation correlates with changes in apoptotic morphology in MOLT-4 leukemia cells exposed to X-ray irradiation.
Caspase-3 is a critical effector caspase for apoptosis, which cleaves proteins, including cytoskeletal and associated proteins, kinases, and members of the Bcl-2 family of apoptosis-related proteins. This leads to changes in apoptotic morphology, such as membrane externalization and cytoplasm and nuclear condensation. It has been reported that pro-caspase-3 is activated in the cytosol. However, it remains obscure how caspase-3 activation correlates to serial changes in cell morphology during apoptosis. The current study was therefore undertaken to assess the relationship between caspase-3 activation and its subcellular localization and alterations in apoptotic morphology in MOLT-4 human leukemia cells exposed to X-ray irradiation. Fluorescence labeled inhibitor of caspases (FLICA) was used to detect caspase-3 activity in apoptotic cells in this project; cell morphology and caspase-3 sub-localization were determined by confocal microscopy. Our data showed that MOLT-4 cells presented typical morphological changes in apoptosis, such as membrane reversion, DNA fragmentation, and formation of apoptotic cell bodies following 10 Gray (Gy) of X-ray irradiation. Caspase-3 was activated 2 h after X-ray irradiation, and its activity increased markedly after 4-6-h exposure. Membrane reversion in MOLT-4 leukemia cells was detected by Annexin V assay at 4 h following X-ray irradiation, 2 h after the elevated caspase-3 activity was measured. Cytologically, activation of caspase-3 was first observed close to the inside surface of the cellular membrane, then transferred to the cytoplasm, and finally translocated to the nuclear region. We conclude that caspase-3 is activated in MOLT-4 cells following exposure to X-rays, and that the enhanced caspase-3 activity and its sub-localization shifting is correlated to changes in apoptotic morphology. The spatial shift of activated caspase-3 in X-ray-induced apoptotic MOLT-4 leukemia cells is a process of crucial importance for apoptosis.
Feng
Yongdong
Y
Tongji Cancer Institute, Department of Surgery, Tongji Hospital, Tongji Medical College, Central China University of Science and Technology, Wuhan, Hubei 430030, P.R. China.
Hu
Junbo
J
Xie
Daxin
D
Qin
Jichao
J
Zhong
Yisheng
Y
Li
Xiaolan
X
Xiao
Wei
W
Wu
Jianhong
J
Tao
Deding
D
Zhang
Manchao
M
Zhu
Yunfeng
Y
Song
Yuping
Y
Reed
Eddie
E
Li
Qingdi Q
QQ
Gong
Jianping
J
D017209:Apoptosis / Q000528:radiation effects*; D053148:Caspase 3; D020169:Caspases / Q000737:chemistry / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism / Q000528:radiation effects; D048430:Cell Shape / Q000528:radiation effects; D053938:DNA Fragmentation / Q000528:radiation effects; D004789:Enzyme Activation / Q000528:radiation effects; D004792:Enzyme Precursors / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D007938:Leukemia / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D013997:Time Factors; D014965:X-Rays
D004792:Enzyme Precursors; D005456:Fluorescent Dyes; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases