Insulin activates caspase-3 by a phosphatidylinositol 3'-kinase-dependent pathway.
Activation of the caspase proteases by c-Jun N-terminal kinase 1 (JNK1) has been proposed as a mechanism of apoptotic cell death. Here we report that insulin activates caspase-3 by a pathway requiring phosphatidylinositol 3'-kinase (PI3-kinase). JNK1 assays demonstrated that insulin treatment of myeloma cells induced 3-fold activation of JNK1. Inhibition of PI3-kinase with wortmannin and LY294002 blocked insulin-dependent activation of JNK1. Caspase assays demonstrated that insulin increased caspase-3 activity 3-fold and that inhibition of PI3-kinase blocked this effect. Cell death was doubled by insulin and was due to a 3-fold increase in apoptosis of cells in the G1/G0 phase of the cell cycle. Inhibition of PI3-kinase completely blocked this effect. Finally, inhibition of caspase-3 with benzyloxycarbonyl-Asp-2,6-dichlorobenzoyloxymethylketone blocked cell death due to insulin. Taken together, these findings indicate that insulin activates caspase-3 by a PI3-kinase-dependent pathway resulting in increased apoptosis and cell death.
Godbout
J P
JP
Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana 61801, USA.
Cengel
K A
KA
Cheng
S L
SL
Minshall
C
C
Kelley
K W
KW
Freund
G G
GG
D017209:Apoptosis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D053148:Caspase 3; D020169:Caspases; D007328:Insulin; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C505407:CASP3 protein, human