Interferon-gamma activates EGF receptor and increases TGF-alpha in T84 cells: implications for chloride secretion.
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.
Uribe
Jorge M
JM
Department of Medicine, University of California San Diego School of Medicine, San Diego, California 92103-8414, USA.
McCole
Declan F
DF
Barrett
Kim E
KE
D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007163:Immunosorbent Techniques; D007371:Interferon-gamma / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000502:physiology; D007700:Kinetics; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011743:Pyrimidines / Q000493:pharmacokinetics; D011799:Quinazolines; D016211:Transforming Growth Factor alpha / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
C412373:AG 1879; D000906:Antibodies; D002712:Chlorides; D004791:Enzyme Inhibitors; D011743:Pyrimidines; D011799:Quinazolines; D016211:Transforming Growth Factor alpha; D020032:Tyrphostins; C101044:RTKI cpd; D019000:Phosphotyrosine; D007371:Interferon-gamma; D002217:Carbachol; D066246:ErbB Receptors; D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases