Proteasome inhibitor MG132-induced apoptosis via ER stress-mediated apoptotic pathway and its potentiation by protein tyrosine kinase p56lck in human Jurkat T cells

• Published in: Biochemical pharmacology 2011-11, Vol.82 (9), p.1110-1125
• Main Authors: Park, Hae Sun, Jun, Do Youn, Han, Cho Rong, Woo, Hyun Ju, Kim, Young Ho
• Format: Article
• Language: English
• Subjects: Apoptosis; Apoptosis - drug effects; bcl-X Protein - genetics; bcl-X Protein - metabolism; Biological and medical sciences; Caspase Inhibitors; caspase-12; caspase-7; caspase-9; Caspases - genetics; Caspases - metabolism; cytochrome c; cytotoxicity; DNA fragmentation; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - physiology; ER stress; Gene Expression Regulation, Neoplastic; Humans; Jurkat Cells; Leupeptins - pharmacology; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - genetics; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - metabolism; MAP Kinase Kinase 4 - antagonists & inhibitors; Medical sciences; membrane potential; Mitochondria - metabolism; Mitochondria-dependent caspase cascade; mitochondrial membrane; p38 Mitogen-Activated Protein Kinases - antagonists & inhibitors; p56lck; pharmacology; Pharmacology. Drug treatments; proteasome endopeptidase complex; Proteasome inhibitor; Stress, Physiological - drug effects; T-lymphocytes; tyrosine
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2011.07.085

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-G1 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 p56lck-stable transfectant JCaM1.6/lck than in p56lck-deficient JCaM1.6/vector. The cytotoxicity of MG132 toward p56lck-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 p56lck enhances MG132-induced apoptosis by augmenting ER stress-mediated apoptotic events in Jurkat T cells.