The mechanism of geranylgeraniol-induced apoptosis involves activation, by a caspase-3-like protease, of a c-jun N-terminal kinase signaling cascade and differs from mechanisms of apoptosis induced by conventional chemotherapeutic drugs.
In the present study, we investigated the effects of geranylgeraniol (GGO), a potent inducer of apoptosis in various lines of human tumor cells, on signal transduction cascades involved in apoptosis in human leukemia cells. GGO strongly induced the activation of c-Jun N-terminal kinase (JNK/SAPK) within 2 h in U937 and K562 cells, while neither ERK nor p38 was activated to any considerable extent during GGO-induced apoptosis. Transient expression of a constitutively active mutant form of mitogen-activated protein kinase kinase 1 (MEKK1), deltaMEKK1, or of deltaMEKK1-green fluorescent protein (GFP) in K562 cells activated JNK, but not a caspase-3-like protease, and was insufficient to induce cell death but rendered cells susceptible to GGO-induced cell death. Stable expressions of deltaMEKK1-GFP in U937 cells gave similar results. In contrast to VP-16-induced apoptosis, GGO-induced activation of JNK was almost completely inhibited by benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone (Z-DEVD) and by benzyloxycarbonyl-Asp-CH2OC[O]-2,6,-dichlorobenzene (Z-Asp), indicating that the JNK-activation step is located downstream of the caspase signaling pathway in GGO-induced apoptosis. Moreover, apoptosis induced by GGO was significantly inhibited in two lines of cells with a dominant-negative deletion mutation in c-Jun, indicating a requirement for JNK signaling. In addition, unlike the effects on other inducers of apoptosis, the activation of JNK and of the caspase-3-like protease by GGO was significantly delayed by 12-O-tetradecanoylphorbol-13-acetate (TPA), suggesting that the site of inhibition by TPA might be located upstream of the protease and JNK in the GGO-induced apoptotic signaling pathway.
Masuda
Y
Y
Laboratory of Biological Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
Nakaya
M
M
Aiuchi
T
T
Hashimoto
S
S
Nakajo
S
S
Nakaya
K
K
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology*; D049452:Green Fluorescent Proteins; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D020014:K562 Cells; D008164:Luminescent Proteins / Q000235:genetics; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016296:Mutagenesis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D017384:Sequence Deletion; D014162:Transfection; D020298:U937 Cells
D000970:Antineoplastic Agents; D015853:Cysteine Proteinase Inhibitors; D004224:Diterpenes; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C017338:geranylgeraniol; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases