title: Proteasome inhibitor MG132-induced apoptosis via ER stress-mediated apoptotic pathway and its potentiation by protein tyrosine kinase p56lck in human Jurkat T cells.
abstract: Exposure of human Jurkat T cells to MG132 caused apoptosis along with upregulation of Grp78/BiP and CHOP/GADD153, activation of JNK and p38MAPK, activation of Bak, mitochondrial membrane potential (Δψm) loss, cytochrome c release, activation of caspase-12, -9, -3, -7, and -8, cleavage of Bid and PARP, and DNA fragmentation. However, these MG132-induced apoptotic events, with the exceptions of upregulation of Grp78/BiP and CHOP/GADD153 and activation of JNK and p38MAPK, were abrogated by overexpression of Bcl-xL. Pretreatment with the pan-caspase inhibitor z-VAD-fmk prevented MG132-induced apoptotic caspase cascade, but allowed upregulation of Grp78/BiP and CHOP/GADD153 levels, activation of JNK and p38MAPK, Δψm loss, and cleavage of procaspase-9 (47kDa) to active form (35kDa). Further analysis using selective caspase inhibitors revealed that caspase-12 activation was required for activation of caspase-9 and -3 to the sufficient level for subsequent activation of caspase-7 and -8. MG132-induced cytotoxicity, apoptotic sub-G(1) peak, Bak activation, and Δψm loss were markedly reduced by p38MAPK inhibitor, but not by JNK inhibitor. MG132-induced apoptotic changes, including upregulation of Grp78/BiP and CHOP/GADD153 levels, activation of caspase-12, p38MAPK and Bak, and mitochondria-dependent activation of caspase cascade were more significant in p56(lck)-stable transfectant JCaM1.6/lck than in p56(lck)-deficient JCaM1.6/vector. The cytotoxicity of MG132 toward p56(lck)-positive Jurkat T cell clone was not affected by the Src-like kinase inhibitor PP2. These results demonstrated that MG132-induced apoptosis was caused by ER stress and subsequent activation of mitochondria-dependent caspase cascade, and that the presence of p56(lck) enhances MG132-induced apoptosis by augmenting ER stress-mediated apoptotic events in Jurkat T cells.
authors.affiliation: Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Hae Sun
authors.initials: HS
authors.lastname: Park
authors.forename: Do Youn
authors.initials: do Y
authors.lastname: Jun
authors.forename: Cho Rong
authors.initials: CR
authors.lastname: Han
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Woo
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Kim
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000502:physiology; D000091342:Endoplasmic Reticulum Chaperone BiP; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D019169:Jurkat Cells; D007976:Leupeptins / Q000494:pharmacology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors; D008928:Mitochondria / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects*; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
chemical_list: C494811:BCL2L1 protein, human; D061945:Caspase Inhibitors; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D007976:Leupeptins; D051020:bcl-X Protein; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020169:Caspases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde