The mechanism of cleavage of EGFR ligands induced by inflammatory cytokines in gastric epithelial cells ; ADAM10 mediates IL-8-induced EGFR transactivation

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The epidermal growth factor receptor (EGFR) can be transactivated by many factors including G-protein-coupled receptor (GPCR) agonists and cytokines. EGFR transactivation requires a disintegrin and metalloproteinase (ADAM), which sheds EGFR ligands. In order to investigate the mechanism of EGFR transactivation induced by IL-8 (GPCR agonist) and IL-1β(non-GPCR agonist) which play critical roles in Helicobacter pylori-associated gastritis, we assessed IL-8-and IL-1β-dependent ectodomain shedding of EGFR-ligand using KATO III cell transfectants stably expressing alkaline phosphatase (AP)-tagged heparin-binding EGF-like growth factor (HB-EGF), TGF-α, or amphiregulin (AR) precursors as well as siRNA against ADAM10, 12, or 17. IL-8 dose-dependently released the EGFR ligands (HB-EGF>AR>TGF-α), and transiently phosphorylated EGFR with a peak at 15 min after stimulation. A metalloproteinase inhibitor, KB-R7785, completely blocked shedding of the ligands and EGFR transactivation. Depletion of ADAM10 by siRNA significantly reduced the EGFR transactivation, but those of ADAM12 and 17 did not. IL-1β dose-dependently enhanced shedding of HB-EGF, which was not inhibited by KB-R7785 in the early phase. The EGFR transactivation in the late phase was, however, blocked by KB-R7785 and abrogated by anti-IL-8 neutralizing antibody. These results indicate that IL-8 induces shedding of EGFR ligands due to an ADAM 10-dependent pathway in gastric epithelial cells, while IL-1β acts principally by an ADAM-independent pathway. Both cytokines transactivate EGFR, and IL-1β-dependent prolonged EGFR transactivation involves multiple pathways, including an IL-8-dependent pathway.