Induction of G1 arrest and apoptosis in human jurkat T cells by pentagalloylglucose through inhibiting proteasome activity and elevating p27Kip1, p21Cip1/WAF1, and Bax proteins.
Pentagalloylglucose, which is found in many medicinal plants, can arrest the cell cycle at G(1) phase through down-regulation of cyclin-dependent kinases 2 and 4 and up-regulation of the cyclin-dependent kinase inhibitors p27(Kip1) and p21(Cip1/WAF1) in human breast cancer cells. Pentagalloylglucose also induces apoptosis in human leukemic cells. However, the mechanisms by which pentagalloylglucose induces these effects is unclear. We now show that pentagalloylglucose inhibits the activities of purified 20 and 26 S proteasomes in vitro, the 26 S proteasome in Jurkat T cell lysates, and chymotrypsin-like activity of the 26 S proteasome in intact Jurkat T cells. The turnover of p27(Kip1) and p21(Cip1/WAF1), which is necessary for cell cycle progression mediated by proteasome degradation, was disrupted by treatment of human Jurkat T cells with pentagalloylglucose. This was shown by cycloheximide treatment and in vivo pulse-chase labeling experiments, and this effect correlated with the arrest of proliferation of Jurkat T cells at G(1). Inhibition of the proteasome by pentagalloylglucose and by the proteasome inhibitor MG132 caused accumulation of ubiquitin-tagged proteins in Jurkat T cells. The addition of pentagalloylglucose to Jurkat T cells enhanced the stability of the proteasome substrate Bax and increased cytochrome c release and apoptosis. Our findings suggest a mechanism for the effect of pentagalloylglucose on the cell cycle in human leukemic cells: that pentagalloylglucose down-regulates proteasome-mediated pathways because it is a proteasome inhibitor.
Chen
Wei-Jen
WJ
Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Lin
Jen-Kun
JK
D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D047348:Hydrolyzable Tannins / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D019169:Jurkat Cells; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D015415:Biomarkers; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D047348:Hydrolyzable Tannins; D009097:Multienzyme Complexes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D051028:bcl-2-Associated X Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; C435084:pentagalloylglucose; D045304:Cytochromes c; D002918:Chymotrypsin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex