Cephalostatin 1 inactivates Bcl-2 by hyperphosphorylation independent of M-phase arrest and DNA damage.

Abstract

Cephalostatin 1 is a marine product that induces a novel cytochrome c-independent apoptotic pathway in Jurkat leukemia T cells (Cancer Res 63:8869-8876, 2003). Here, we show that overexpression of the antiapoptotic protein Bcl-2 protects cells only partially against cephalostatin 1-induced apoptosis. The mechanism of Bcl-2 inactivation by cephalostatin 1 is based on hyperphosphorylation of Bcl-2 on Thr69 and Ser87 because Jurkat cells overexpressing a Bcl-2 protein with mutations on both phosphorylation sites were completely protected against cephalostatin 1. In search of the kinase responsible for Bcl-2 phosphorylation, c-Jun NH2-terminal kinase (JNK) was found to be activated by cephalostatin 1. Reduction of Bcl-2 phosphorylation by the specific JNK inhibitor (anthra(1,3-cd)pyrazol-6(2H)-one) SP600125 suggested a crucial role for JNK in this process. JNK activation was not a consequence of DNA damage, a known stimulus of JNK, because cephalostatin 1 did not induce DNA lesions as shown by the comet assay. Arrest in M-phase is also demonstrated to be associated with JNK activation. However, cephalostatin 1 does not evoke an arrest in M-phase as shown by flow cytometry. Together, cephalostatin 1 is shown to induce JNK activation with subsequent Bcl-2 phosphorylation and inactivation. Reported triggers, such as the induction of an M-phase arrest or DNA damage are not involved in this process, suggesting a novel mechanism for cephalostatin 1-mediated Bcl-2 hyperphosphorylation.

• Authors: Irina M Müller, Verena M Dirsch, Anita Rudy, Nancy López-Antón, George R Pettit, Angelika M Vollmar
• Journal: Molecular pharmacology (Mol Pharmacol) Vol. 67 Issue 5 Pg. 1684-9 (May 2005) ISSN: 0026-895X [Print] United States
• PMID: 15703383 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Phenazines
• Spiro Compounds
• Steroids
• cephalostatin I

Topics

• Cell Division (drug effects, genetics)
• DNA Damage (drug effects, genetics)
• Gene Silencing (drug effects)
• Genes, bcl-2 (drug effects)
• Humans
• Jurkat Cells
• Phenazines (chemistry, isolation & purification, pharmacology)
• Phosphorylation (drug effects)
• Spiro Compounds (chemistry, isolation & purification, pharmacology)
• Steroids (chemistry, isolation & purification, pharmacology)