Transient activation of Jun N-terminal kinases and protection from apoptosis by the insulin-like growth factor I receptor can be suppressed by dicumarol.
The insulin-like growth factor I receptor (IGF-IR) activated by its ligands insulin-like growth factor (IGF)-I or IGF-II mediates suppression of apoptosis and contributes to tumorigenesis and cell growth. Here we investigated the activation of the stress-activated protein kinases including Jun N-terminal Kinases and p38 MAPK by IGF-I in interleukin-3-dependent FL5.12 lymphocytic cells that overexpress the IGF-IR (FL5.12/WT). We have shown previously that IGF-I protects these cells from apoptosis induced by interleukin-3 withdrawal but does not promote proliferation. IGF-I induced a rapid and transient activation of JNK that peaked at 40 min that was paralleled by a transient and robust phosphorylation of c-Jun. p38 was constitutively phosphorylated in FL5.12/WT cells. Activation of the JNK pathway by IGF-I occurred in the presence of phosphatidylinositol 3-kinase inhibitors and could be enhanced by anisomycin. Analysis of a series of FL5.12 cells expressing mutated IGF-IRs and analysis of 32D/IGF-IR cells showed that neither the C terminus of the receptor nor IRS-1 and IRS-2 were required for JNK activation, although tyrosine 950 was essential for full activation. The JNK inhibitor dicumarol suppressed IGF-I-mediated activation of JNK and phosphorylation of c-Jun but did not affect p38 and IkappaB phosphorylation or activation of AKT. IGF-I-mediated protection from apoptosis in FL5.12/WT cells was completely suppressed by dicumarol and partially suppressed by a p38 inhibitor. In the breast carcinoma cell line MCF-7, treatment with dicumarol also induced apoptosis. These data indicate that transient activation of JNK by IGF-I is mediated by signals that are distinct from those leading to phosphatidylinositol 3-kinase and AKT activation. The data further suggest that the SAPK pathways contribute to suppression of apoptosis by the IGF-IR.
Cell Biology Laboratory, Department of Biochemistry, and Biosciences Research Institute, National University of Ireland, Cork, Ireland.
D
D
Krause
A
A
Lyons
C
C
Fennelly
R
R
O'Connor
D000841:Anisomycin / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D003599:Cytoskeleton / Q000378:metabolism; D001728:Dicumarol / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007377:Interleukin-3 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000737:chemistry; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D005419:Flavonoids; C526292:IRS1 protein, human; C526297:IRS2 protein, human; D007093:Imidazoles; D055504:Insulin Receptor Substrate Proteins; D007377:Interleukin-3; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011500:Protein Synthesis Inhibitors; D011725:Pyridines; D011994:Recombinant Proteins; D014443:Tyrosine; D000841:Anisomycin; D001728:Dicumarol; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one