title: Direct interaction between surface β1,4-galactosyltransferase 1 and epidermal growth factor receptor (EGFR) inhibits EGFR activation in hepatocellular carcinoma.
abstract: Our previous studies showed that cell surface β1,4-galactosyltransferase 1 (β1,4GT1) negatively regulated cell survival through inhibition and modulation of the epidermal growth factor receptor (EGFR) signaling pathway in human hepatocellular carcinoma (HCC) SMMC-7721 cells. However, the underlying mechanism remains unclear. Here we demonstrated that β1,4-galactosyltransferase 1 (β1,4GT1) interacted with EGFR in vitro by GST pull-down analysis. Furthermore, we demonstrated that β1,4GT1 bound to EGFR in vivo by co-immunoprecipitation and determined the co-localization of β1,4GT1 and EGFR on the cell surface via confocal laser scanning microscopy analysis. Finally, using (125)I-EGF binding experiments and Western blot analysis, we found that overexpression of β1,4GT1 inhibited (125)I-EGF binding to EGFR, and consequently reduced the levels of EGFR dimerization and phosphorylation. In contrast, RNAi-mediated knockdown of β1,4GT1 increased the levels of EGFR dimerization and phosphorylation. These data suggest that cell surface β1,4GT1 interacts with EGFR and inhibits EGFR activation.
authors.affiliation: Department of Gastroenterology and Hepatology of Zhongshan Hospital, Fudan University, Shanghai 200032, China.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Tang
authors.forename: Shuqiang
authors.initials: S
authors.lastname: Weng
authors.forename: Si
authors.initials: S
authors.lastname: Zhang
authors.forename: Weibing
authors.initials: W
authors.lastname: Wu
authors.forename: Ling
authors.initials: L
authors.lastname: Dong
authors.forename: Xizhong
authors.initials: X
authors.lastname: Shen
authors.forename: Songwen
authors.initials: S
authors.lastname: Zhang
authors.forename: Jianxin
authors.initials: J
authors.lastname: Gu
authors.forename: Ruyi
authors.initials: R
authors.lastname: Xue
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D017931:DNA Primers; D066246:ErbB Receptors / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D008113:Liver Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D018613:Microscopy, Confocal; D009237:N-Acetyllactosamine Synthase; D011485:Protein Binding
chemical_list: D017931:DNA Primers; D009237:N-Acetyllactosamine Synthase; D066246:ErbB Receptors