Interferon-gamma activates EGF receptor and increases TGF-alpha in T84 cells: implications for chloride secretion

Am J Physiol Gastrointest Liver Physiol. 2002 Oct;283(4):G923-31. doi: 10.1152/ajpgi.00237.2002.

Abstract

IFN-gamma inhibits intestinal Cl(-) secretion, in part via downregulation of CFTR and Na(+)-K(+)-ATPase activity and expression, but the proximal signaling events were unknown. We have shown that transforming growth factor-alpha (TGF-alpha) inhibits calcium-activated Cl(-) secretion, and effects of IFN-gamma in other systems are mediated via EGF family members. We tested whether IFN-gamma inhibits Cl(-) secretion via EGF receptor (EGFr) activation. IFN-gamma increased tyrosine phosphorylation in T84 cells at 24 h, including the EGFr. IFN-gamma also increased cell-associated pro-TGF-alpha, as well as free TGF-alpha in the bathing media. However, whereas IFN-gamma significantly inhibited carbachol-induced Cl(-) secretion, neither neutralizing antibodies to TGF-alpha nor an EGFr inhibitor (1 microM tyrphostin AG 1478) were able to reverse this inhibitory effect. AG 1478 also failed to reverse IFN-gamma-induced tyrosine phosphorylation of the EGFr, but receptor phosphorylation was attenuated by both the neutralizing antibody to TGF-alpha and PP2, a Src kinase inhibitor. Moreover, PP2 reversed the inhibitory effect of IFN-gamma on Cl(-) secretion. In total, our findings suggest an increase in functional TGF-alpha and activation of the EGFr in response to IFN-gamma. The release of TGF-alpha and intracellular Src activation likely combine to mediate EGFr phosphorylation, but only Src appears to contribute to the inhibition of transport. Nevertheless, because TGF-alpha plays a role in restitution and repair of the intestinal epithelium after injury, we speculate that these findings reflect a feedback loop whereby IFN-gamma modulates the extent of cytokine-induced intestinal damage.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies / pharmacology
  • Blotting, Western
  • Carbachol / pharmacology
  • Cell Line
  • Cell Membrane / metabolism
  • Chlorides / metabolism*
  • Colon / physiology
  • Enzyme Inhibitors / pharmacology
  • ErbB Receptors / antagonists & inhibitors
  • ErbB Receptors / metabolism
  • ErbB Receptors / physiology*
  • Humans
  • Immunosorbent Techniques
  • Interferon-gamma / pharmacology*
  • Intestinal Mucosa / metabolism*
  • Intestinal Mucosa / physiology
  • Kinetics
  • Phosphorylation
  • Phosphotyrosine / metabolism
  • Protein Tyrosine Phosphatases / antagonists & inhibitors
  • Pyrimidines / pharmacokinetics
  • Quinazolines
  • Transforming Growth Factor alpha / metabolism*
  • Tyrphostins / pharmacology
  • src-Family Kinases / antagonists & inhibitors

Substances

  • AG 1879
  • Antibodies
  • Chlorides
  • Enzyme Inhibitors
  • Pyrimidines
  • Quinazolines
  • Transforming Growth Factor alpha
  • Tyrphostins
  • RTKI cpd
  • Phosphotyrosine
  • Interferon-gamma
  • Carbachol
  • ErbB Receptors
  • src-Family Kinases
  • Protein Tyrosine Phosphatases