JNK is associated with Bcl-2 and PP1 in mitochondria: paclitaxel induces its activation and its association with the phosphorylated form of Bcl-2.
It has been shown that the activation of JNK after paclitaxel-induced microtubule damage is parallel to Bcl-2 phosphorylation, cell cycle arrest in mitosis and apoptosis. Using subcellular fractionation and immunocytochemistry, we found here that a pool of activated JNK is located in mitochondria of HeLa cells treated with paclitaxel. Furthermore, whereas the JNK protein is present in a tripartite complex with the anti-apoptotic Bcl-2 protein and the PP1 phosphatase in mitochondria isolated from control cells, the activated form of JNK was associated with the phosphorylated form of Bcl-2, but devoid of PP1, in mitochondria isolated from paclitaxel-treated cells. Moreover, using an original cell-free system, we evidenced a direct involvement of JNK as the kinase responsible for the phosphorylation of mitochondrial Bcl-2 in mitotic arrested cells. Indeed, cytosols prepared from mitotic arrested cells led to a dose-dependent phosphorylation of mitochondrial Bcl-2. Bcl-2 phosphorylation was inhibited by CEP 11004, a JNK pathway inhibitor and by immunodepletion of JNK. Taken together, these data show that JNK activation provides a molecular linkage from microtubule damages to the mitochondrial apoptotic machinery and also point to a pivotal role for the JNK/Bcl-2/PP1 complex in the control of apoptosis following paclitaxel treatment.
Université Paul Sabatier, Toulouse, France.
Laetitia
L
Brichese
Gabrielle
G
Cazettes
Annie
A
Valette
D045744:Cell Line, Tumor; D019926:Cyclin B / Q000378:metabolism; D003600:Cytosol; D004789:Enzyme Activation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D008938:Mitosis; D008940:Mitotic Index; D008954:Models, Biological; D017239:Paclitaxel / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D013997:Time Factors
D019926:Cyclin B; D019253:Proto-Oncogene Proteins c-bcl-2; D048031:JNK Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D017239:Paclitaxel