JNK-dependent release of mitochondrial protein, SMAC during apoptosis in multiple myeloma (MM) cells

Authors:
Chauhan D, Li G, Hideshima T, Podar K, Mitsiades C, Midsiades N, Munshi N, Kharbanda S and Anderson KC
In:
Source: J Biol Chem
Publication Date: (2003)
Issue: 278(20): 17593-17596
Research Area:
Cancer Research/Cell Biology
Cells used in publication:
MM.1S
Species: human
Tissue Origin: blood
Platform:
Nucleofectorâ„¢ I/II/2b
Experiment
Smac (second mitochondria-derived activator of caspases) promotes apoptosis via activation of caspases. Also JNK (c-Jun NH2-terminal kinase) has been linked to apoptosis. However, the role of JNK in the release of mitochondrial Smac is unknown. To address this question the authors blocked JNK by nucleofecting MM.1S (multiple myeloma) cells with a dominant negative version of JNK (DN-JNK) or control vector. Transfected cells were treated with 2ME2 (to induce apoptosis) and analyzed for accumulation of Smac in the cytosol and cell viability. DN-JNF transfectants showed an abolished release of Smac to the cytosol and survived longer than cells transfected with the vector alone.
Abstract
Smac, second mitochondria-derived activator of caspases, promotes apoptosis via activation of caspases. Previous studies have shown that c-Jun NH(2)-terminal kinase (JNK) is involved in regulating another mitochondrial protein, cytochrome c during apoptosis; however, the role of JNK in the release of mitochondrial Smac is unknown. Here we show that induction of apoptosis in multiple myeloma (MM) cells is associated with activation of JNK, translocation of JNK from cytosol to mitochondria, and release of Smac from mitochondria to cytosol. Blocking JNK either by dominant-negative mutant (DN-JNK) or cotreatment with a specific JNK inhibitor, SP600125, abrogates both stress-induced release of Smac and induction of apoptosis. These findings demonstrate that activation of JNK is an obligatory event for the release of Smac during stress-induced apoptosis in MM cells.