Proteasome inhibitor MG132-induced apoptosis via ER stress-mediated apoptotic pathway and its potentiation by protein tyrosine kinase p56(lck) in human Jurkat T cells

作者：Park Hae Sun; Jun Do Youn; Han Cho Rong; Woo Hyun Ju; Kim Young Ho^*

来源：Biochemical Pharmacology, 2011, 82(9): 1110-1125.

DOI：10.1016/j.bcp.2011.07.085

• Proteasome inhibitor
• Apoptosis
• ER stress
• Mitochondria-dependent caspase cascade
• p56(lck)

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 (Delta psi m) 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, Delta psi m loss, and cleavage of procaspase-9 (47 kDa) to active form (35 kDa). 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 Delta psi m 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.

• 出版日期2011-11-1