Activation of cJun NH2-terminal kinase/stress-activated protein kinase by insulin.
One of insulin's many biological effects is the increased transcription of AP-1-regulated genes. cJun is the principal component of the AP-1 transcription complex, which is regulated by the newly discovered members of the MAPK superfamily referred to as cJun NH2-terminal kinases (JNKs) or stress-activated protein kinases (SAPKs). We show that insulin stimulates a dose- and time-dependent increase in JNK activity in Rat 1 fibroblasts overexpressing human insulin receptors (Rat 1 HIR cells). Using two different polyclonal anti-JNK antibodies, JNK activity was measured after immunoprecipitation from whole cell extracts by phosphorylation of GSTcJun(1-79). Peak activation occurred 15 min after insulin addition, resulting in a 2.5-fold increase in GSTcJun(1-79) phosphorylation over unstimulated controls. Maximal JNK activation correlated with the onset of AP-1 DNA binding activity. Both insulin-stimulated JNK activity and insulin-induced AP-1 transcriptional activity were found to be Ras-dependent. These data suggest that in Rat 1 cells, JNK activation may play a role in insulin-regulated AP-1 transcriptional activity leading to a mitogenic response.
Miller
B S
BS
Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, 29425 USA.
Shankavaram
U T
UT
Horney
M J
MJ
Gore
A C
AC
Kurtz
D T
DT
Rosenzweig
S A
SA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D015342:DNA Probes; D004789:Enzyme Activation; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011972:Receptor, Insulin / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D015342:DNA Probes; D007328:Insulin; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D011972:Receptor, Insulin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases