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. 2001 Jun;6(6):519-30.
doi: 10.1046/j.1365-2443.2001.00439.x.

MST1-JNK promotes apoptosis via caspase-dependent and independent pathways

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Free article

MST1-JNK promotes apoptosis via caspase-dependent and independent pathways

S Ura et al. Genes Cells. 2001 Jun.
Free article

Abstract

Background: MST1 is an upstream kinase of the JNK and p38 MAPK pathways whose expression induces apoptotic morphological changes such as nuclear condensation. During apoptosis, caspase cleavage of MST1 removes a C-terminal regulatory domain, increasing the kinase activity of the MST1 N-terminal domain. Downstream pathways of MST1 in the induction of apoptosis remain to be clarified.

Results: In this study, we found that the expression of MST1 resulted in caspase-3 activation. Therefore, MST1 is not only a target of caspases but also an activator of caspases. This caspase activation and apoptotic changes occur through JNK, since the co-expression of a dominant-negative mutant of JNK inhibited MST1-induced morphological changes as well as caspase activation. In contrast, neither a dominant-negative p38 nor the p38 inhibitor SB203580 inhibited them. MST1 induced nucleosomal DNA fragmentation, which was suppressed by caspase inhibitors or ICAD (Inhibitor of Caspase-Activated DNase). Surprisingly, however, other changes such as membrane blebbing and chromatin condensation were not inhibited by caspase inhibitors.

Conclusion: These results suggest that MST1 most likely promotes two events through JNK activation; first, MST1 induces the activation of caspases, resulting in CAD-mediated DNA fragmentation, and second, MST1 induces chromatin condensation and membrane blebbing without utilizing downstream caspases.

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