Submitted on September 20, 2007
Accepted on May 3, 2008
Tumor Necrosis Factor Inhibits Ligand-Stimulated EGF Receptor Activation Through A TNF Receptor 1-Dependent Mechanism
Steven J McElroy1, Mark R Frey2, Fang Yan1, Karen L Edelblum3, Jeremy A Goettel3, Sutha John3, and D. Brent Polk4*
1 Pediatrics, Vanderbilt University, Nashville, Tennessee, United States
2 Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, United States
3 Cell Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States
4 Pediatrics, Vanderbilt University, Nashville, Tennessee, United States; Cell Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States
* To whom correspondence should be addressed. E-mail: d-brent.polk{at}vanderbilt.edu.
Tumor necrosis factor (TNF) and epidermal growth factor (EGF) are key regulators in the intricate balance maintaining intestinal homeostasis. Previous work from our lab shows that TNF attenuates ligand-driven EGF receptor (R) phosphorylation in intestinal epithelial cells. To identify the mechanisms underlying this effect, we examined EGFR phosphorylation in cells lacking individual TNF receptors. TNF attenuated EGF-stimulated EGFR phosphorylation in wild-type and TNFR2-/-, but not TNFR1-/- mouse colon epithelial (MCE) cells. Re-expression of wild type TNFR1 in TNFR1-/- MCE cells rescued TNF induced EGFR inhibition, but expression of TNFR1 deletion mutant constructs lacking the death domain (DD) of TNFR1 did not, implicating this domain in EGFR downregulation. Blockade of p38 MAPK, but not MEK activation of ERK rescued EGF-stimulated phosphorylation in the presence of TNF, consistent with the ability of TNFR1 to stimulate p38 phosphorylation. TNF promoted p38-dependent EGFR internalization in MCE cells, suggesting that desensitization is achieved by reducing receptor accessible to ligand. Taken together these data indicate that TNF activates TNFR1 by DD- and p38-dependent mechanisms to promote EGFR internalization, with potential impact on EGF induced proliferation and migration key processes that promote healing in inflammatory intestinal diseases.
