Gastrin induces heparin-binding epidermal growth factor-like growth factor in rat gastric epithelial cells transfected with gastrin receptor.

Abstract

Parietal cells express heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF). However, it is unknown whether HB-EGF mediates the trophic action of gastrin. The purpose of this study was to determine whether gastrin modulates the expression of HB-EGF, which mediates the proliferative effects of gastrin on gastric epithelial cells. RGM1 cells, a rat gastric epithelial cell line, were transfected with a human gastrin receptor complementary DNA. Gastrin induction of messenger RNAs (mRNAs) for EGF-related polypeptides was assayed by Northern blotting. Processing of cell surface-associated proHB-EGF and secretion of HB-EGF were determined by flow cytometry and Western blotting, respectively. Tyrosine phosphorylation of the EGF receptor was assayed by immunoprecipitation and Western blotting with an antiphosphotyrosine antibody. Cell growth was evaluated by [3H]thymidine incorporation. Gastrin induced expression of HB-EGF mRNA, processing of proHB-EGF, release of HB-EGF into the medium, and tyrosine phosphorylation of the EGF receptor. The growth-stimulatory effects of gastrin were partly inhibited by anti-rat HB-EGF serum and completely blocked by AG1478, an EGF receptor-specific tyrphostin. The findings suggest that HB-EGF at least partially mediates the proliferative effects of gastrin on gastric epithelial cells.