Roles of JAKs in activation of STATs and stimulation of c-fos gene expression by epidermal growth factor.
The tyrosine kinase JAK1 and the transcription factors STAT1 and STAT3 are phosphorylated in response to epidermal growth factor (EGF) and other growth factors. We have used EGF receptor-transfected cell lines defective in individual JAKs to assess the roles of these kinases in STAT activation and signal transduction in response to EGF. Although JAK1 is phosphorylated in response to EGF, it is not required for STAT activation or for induction of the c-fos gene. STAT activation in JAK2- and TYK2-defective cells is also normal, and the tyrosine phosphorylation of these two kinases does not increase upon EGF stimulation in wild-type or JAK1-negative cells. In cells transfected with a kinase-negative mutant EGF receptor, there is no STAT activation in response to EGF and c-fos is not induced, showing that the kinase activity of the receptor is required, directly or indirectly, for these two responses. The data do not support a role for any of the three JAK family members tested in STAT activation and are consistent with a JAK-independent pathway in which the intrinsic kinase domain of the EGF receptor is crucial. Furthermore, data from transient transfection experiments in HeLa cells, using c-fos promoters lacking the STAT regulatory element c-sis-inducible element, indicate that this element may play only a minor role in the induction of c-fos by EGF in these cells.
Department of Molecular Biology, Cleveland Clinic Foundation, Ohio 44195, USA.
D W
DW
Leaman
S
S
Pisharody
T W
TW
Flickinger
M A
MA
Commane
J
J
Schlessinger
I M
IM
Kerr
D E
DE
Levy
G R
GR
Stark
D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D006367:HeLa Cells; D006801:Humans; D053613:Janus Kinase 1; D008969:Molecular Sequence Data; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism*
D017931:DNA Primers; D004268:DNA-Binding Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; D053613:Janus Kinase 1