Src-dependent phosphorylation of the EGF receptor Tyr-845 mediates Stat-p21waf1 pathway in A431 cells.
BACKGROUND
Cell surface receptor for the epidermal growth factor (EGFR) and cytoplasmic tyrosine kinase c-Src co-operate in several cellular functions such as proliferation and apoptosis. Our previous studies have shown that ectopic expression of the adaptor protein p52shc or p66shc, but not p46shc, and EGF stimulation lead to the activation of c-Src that is accompanied by phosphorylation of signal transducers and activators of transcription (Stat) in A431 cells.


RESULTS
Here, we show that by using A431 cells as a model system, expression of p52shc, or cell stimulation with EGF or H2O2 leads to phosphorylation of EGFR on Tyr 845 that is located to the activation segment of the catalytic domain. The phosphorylation of Tyr 845 can be inhibited by PP2, but not by AG1478, and is associated with Src activation and Stat 3/5 phosphorylation, but not with MAP (mitogen-activated protein) kinase phosphorylation. Phosphorylation of Stat 3/5 in response to p52shc expression, EGF or H2O2 could also be inhibited by introduction into cells of phospho-Tyr 845-specific antibody or by expression of dominant-negative version of c-Src. Co-incubation of purified c-Src and EGFR results in phosphorylation of Tyr 845 in vitro, indicating that c-Src can directly phosphorylate EGFR on Tyr 845.


CONCLUSIONS
These results indicate that multiple signals for c-Src activation can promote Stat 3/5 phosphorylations through Src-dependent phosphorylation of EGFR on Tyr 845.
Sato
Ken-ichi
K
Research Centre for Environmental Genomics, Department of Biology, Faculty of Science, Kobe University, Nada, Kobe 657-8501, Japan. kksato@kobe-u.ac.jp
Nagao
Tomomi
T
Iwasaki
Tetsushi
T
Nishihira
Yusuke
Y
Fukami
Yasuo
Y
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000906:Antibodies / Q000494:pharmacology; D000081247:CSK Tyrosine-Protein Kinase; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D066246:ErbB Receptors / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008894:Milk Proteins; D009154:Mutation; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000037:antagonists & inhibitors / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D015534:Trans-Activators / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000906:Antibodies; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D008894:Milk Proteins; C528024:SHC1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D015534:Trans-Activators; D019000:Phosphotyrosine; D014443:Tyrosine; D006861:Hydrogen Peroxide; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human