Wheat germ lectin induces G2/M arrest in mouse L929 fibroblasts.
Wheat germ lectin (WGA) is a cytotoxic lectin for many cell lines [Wang et al., 2000], but its underlying mechanism is not clear. In this report, we found that incubation of synchronized mouse L929 fibroblasts with WGA resulted in a dose-dependent reduction of intracellular incorporation of 3H-thymidine and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide)-conversion activity (IC50 congruent with 0.4 microM). Fluorescein-conjugated WGA was demonstrated to transport from the cell surface into the paranuclear region of cultured L929 cells within 30 min, and subsequently evoked lipid peroxidation of plasma membrane and vacuolation in the cytoplasm of these cells. Studies with tritiated thymidine incorporation, immunofluorescence microscopy, immunoblotting analysis and flow cytometry revealed that WGA inhibited cell cycle progression after one replication, resulting in G2/M arrest and alteration of cell cycle regulatory proteins, particularly activation of p21Cip1/WAF1 and suppression of cyclin B and cdc 2. Although there was an increase of cytosolic caspase 3 and bax protein expression, no apoptotic bodies were observed by both fluorescence and transmission electron microscopy. These results suggest that WGA arrested L929 proliferation after one cell cycle in the G2/M phase through activation of the p21Cip1/WAF1 and suppression of Cyclin B-Cdc2.
Liu
W K
WK
Department of Anatomy, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong. ken-liu@cuhk.edu.hk
Sze
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Ho
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Liu
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Yu
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D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016203:CDC2 Protein Kinase; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D019926:Cyclin B / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology; D016195:G2 Phase / Q000187:drug effects* / Q000502:physiology; D015227:Lipid Peroxidation / Q000187:drug effects; D008677:Metaphase / Q000187:drug effects; D051379:Mice; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014617:Vacuoles / Q000502:physiology; D014909:Wheat Germ Agglutinins / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein; D020687:cdc25 Phosphatases / Q000378:metabolism
C494827:Bax protein, mouse; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D019926:Cyclin B; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D019253:Proto-Oncogene Proteins c-bcl-2; D014909:Wheat Germ Agglutinins; D051028:bcl-2-Associated X Protein; D004247:DNA; D016203:CDC2 Protein Kinase; C517010:Cdc25c protein, mouse; D020687:cdc25 Phosphatases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases