Isolation and characterization of a gene expressed mainly in the gastric epithelium, a novel member of the ep37 family that belongs to the betagamma-crystallin superfamily.

ABSTRACT

EP37 family proteins are non-lens members of the betagamma-crystallin superfamily, of which expression is observed in integumental tissues of the Japanese newt, Cynops pyrrhogaster. In the present study, a gene was isolated that has high homology with ep37 and is transcribed mainly in the gastric epithelial cells and hence designated gep. The predicted amino acid sequence of the gep cDNA contains four betagamma-crystallin motifs in the N-terminal half, as is the case in the integumental EP37 proteins. Immunohistochemical analysis showed that GEP protein was mainly localized on the luminal content of the surface mucous cells of the gastric epithelium in both premetamorphic larvae and adults. In addition, GEP protein was also expressed in fundic glands after metamorphosis. Considering the fact that beta- and gamma-crystallins are evolutionarily related to stress-induced proteins, this localization suggests that GEP protein may have an evolutionarily conserved role in protection against physico-chemical stresses, such as physical abrasion and autodigestion, during assimilation.