Direct Activation of Mitochondrial Apoptosis Machinery by c-Jun N-terminal Kinase in Adult Cardiac Myocytes

Abstract

Although oxidative stress causes activation of c-Jun N-terminal kinase (JNK) and apoptosis in many cell types, how the JNK pathway is connected to the apoptosis pathway is unclear. The molecular mechanism of JNK-mediated apoptosis was investigated in adult rat cardiac myocytes in culture as a model system that is sensitive to oxidative stress. Oxidative stress caused JNK activation, cytochrome c release, and apoptosis without new protein synthesis. Oxidative stress-induced apoptosis was abrogated by dominant negative stress-activated protein kinase/extracellular signal-regulated kinase kinase-1 (SEK1)-mediated inhibition of the JNK pathway, whereas activation of the JNK pathway by constitutively active SEK1 was sufficient to cause apoptosis. Inhibition of caspase-9, an apical caspase in the mitochondrial apoptosis pathway, suppressed oxidative stress-induced apoptosis, whereas inhibition of caspase-8 had no effect, indicating that both the JNK pathway and the mitochondrial apoptosis machinery are central to oxidative stress-induced apoptosis. Both JNK and SEK1 localized on mitochondria where JNK was activated by oxidative stress. Furthermore, active JNK caused the release of apoptogenic factors such as cytochrome c from isolated mitochondria in a cell-free assay. These findings indicate that the JNK pathway is a direct activator of mitochondrial death machinery without other cellular components and provide a molecular linkage from oxidative stress to the mitochondrial apoptosis machinery.

Lamin A/C haploinsufficiency causes dilated cardiomyopathy and apoptosis-triggered cardiac conduction system disease

“…The effects of Lmna mutations on proteins particularly important for conduction system structure or function might weaken these specialized cells and promote early apoptotic death. Activation of c-jun N-terminal kinase (JNK), a stress-activated protein kinase, has been previously implicated in the process of cardiomyopathy and cardiac conduction system disease by downregulation of the gap junction protein connexin 43 [32,33], and cardiomyocyte apoptosis [34]. However, the present study showed no c-Jun activation in hearts from Lmna +/-mice.…”

“…Activation of MAPK signaling cascade has recently been identified in hearts from mice homozygous for the LMNA mutation H222P [23], and this molecular pathway has previously been implicated in the development of cardiomyopathy, conduction defects [32,33] and apoptosis [34].…”

CRNK gene transfer improves function and reverses the myosin heavy chain isoenzyme switch during post-myocardial infarction left ventricular remodeling

“…In contrast to FAK, PYK2 appears to direct downstream signals to either pro-or anti-apoptotic signaling cascades depending on which molecules bind to the phosphorylated kinase. For instance, Melendez et al (3) previously demonstrated that overexpression of wildtype PYK2 promoted cardiomyocyte apoptosis, perhaps via the preferential activation of JNKs (3,5,6,32) and direct activation of the mitochondrial apoptotic machinery (35). PYK2-dependent apoptosis could be suppressed by prior overexpression of paxillin, which binds to the C-terminal domain of PYK2 (14,36) and prevented JNK activation (3).…”

Critical role of acidic sphingomyelinase in murine hepatic ischemia-reperfusion injury

“…In agreement with these findings, the potent activation of JNK (eightfold) by exogenous ASMase 47 has been reported in primary hepatocytes. Furthermore, the interaction of JNK with mitochondria has been reported during cell death, 48,49 opening the possibility that the role of JNK in hepatic I/R damage may be due to its interaction with mitochondria. However, the cytotoxic role of JNK may be attributable not only to its putative interaction with mitochondria but also to the activation of downstream targets, including BH3-only members of the Bcl-2 family such as Bim, which can be regulated by transcriptional and post-translational mechanisms.…”