Lactobacillus reuteri glyceraldehyde-3-phosphate dehydrogenase functions in adhesion to intestinal epithelial cells

This study was aimed to identify key surface proteins mediating the adhesion of lactobacilli to intestinal epithelial cells. By using Caco-2 and IPEC-J2 cells labeled with sulfo-NHS-biotin in the western blotting, a protein band of an approximately 37 kDa was detected on the surface layer of Lactobacillus reuteri strains ZJ616, ZJ617, ZJ621, and ZJ623 and Lactobacillus rhamnosus GG. Mass spectrometry analysis using the adhesion-related protein from L. reuteri ZJ617 showed that it was 100% homologous to the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of L. reuteri JCM 1112 (GenBank: YP_001841377). The ability of L. reuteri ZJ617 to adhere to epithelial cells decreased significantly by treatment with LiCl or by blocking with an anti-GAPDH antibody, in comparison with the untreated strain (p < 0.05). Immunoelectron microscopic and immunofluorescence analyses confirmed that GAPDH is located on the surface layer of L. reuteri ZJ617. The results indicated that the GAPDH protein of L. reuteri ZJ617 acts as an adhesion component that plays an important role in binding to the intestinal epithelial cells.