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EGFR plays a pivotal role in the regulation of apoptosis in intestinal epithelial cells
Author(s) -
Bhattacharya Sujoy,
Ray Ramesh M.,
Johnson Leonard R.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1315-b
Subject(s) - phosphorylation , polyamine , microbiology and biotechnology , proto oncogene tyrosine protein kinase src , tyrosine phosphorylation , tyrosine kinase , apoptosis , kinase , egfr inhibitors , biology , ornithine decarboxylase , chemistry , spermine , cancer research , signal transduction , epidermal growth factor receptor , biochemistry , receptor , enzyme
Intracellular polyamine synthesis is regulated by the enzyme ornithine decarboxylase (ODC), and its inhibition by α‐difluromethylornithine (DFMO), confers resistance to apoptosis. We have previously shown that DFMO leads to the inhibition of de novo polyamine synthesis, which in turn rapidly activates ERKs, Src, STAT3 and NF‐κB via integrin‐β3 in intestinal epithelial cells. We hypothesized that EGFR phosphorylation regulates the early response to polyamine‐depletion. DFMO increased EGFR phosphorylation on tyrosine residues 845 and 1173 within 5min. Phosphorylation declined after 10min and was prevented by the addition of exogenous putrescine to DFMO‐containing medium. Subsequently, phosphorylation of the 145‐Kd cytoplasmic tail of the EGFR at residue 845 gradually increased in a time‐dependent manner. Pre‐treatment with either DFMO or EGF for 1h protected cells from TNF‐α/CHX‐induced apoptosis. Exogenous addition of polyamines prevented the protective effect of DFMO. In addition, inhibition of integrin beta‐3 activity (with RGDS), Src activity (with PP2), or EGFR kinase activity (with AG1478), increased basal apoptosis and prevented protection conferred by either DFMO or EGF. Polyamine‐depletion failed to protect B82L fibroblasts, lacking the EGFR, or transfectants expressing either kinase dead EGFR(K721A) or an EGFR(Y845F) mutant that lacked the Src phosphorylation site. Conversely, introduction of the wild type EGFR into B82L fibroblasts restored the protective effect of polyamine depletion. Fibronectin activated the EGFR, Src, ERKs and protected cells from apoptosis. Taken together, our data indicate an essential role of EGFR kinase activity in protective responses in polyamine‐depleted cells. Supported by NIDDK grant DK‐16505.