Hepatocyte growth factor stimulates the migration of gastric epithelial cells by altering the subcellular localization of the tight junction protein ZO-1.
BACKGROUND
Hepatocyte growth factor (HGF) is essential for epithelial restitution, a process in which epithelial cells rapidly migrate to cover desquamated epithelium after mucosal injury in the gastrointestinal tract. In this study, we aimed to elucidate the molecular mechanisms of the HGF-mediated reconstitution of gastric epithelial structures by analyzing the expression and subcellular dynamics of tight junction proteins.


METHODS
We treated human gastric epithelial MKN74 cells with HGF, and examined the effects of HGF on cell migration and proliferation, and the expression and subcellular dynamics of tight junction proteins; as well, we investigated the effect of HGF on paracellular permeability to macromolecules (using fluorescein isothiocyanate [FITC]-dextran).


RESULTS
HGF significantly stimulated the migration of MKN74 cells, but not their proliferation, in a dose-dependent manner. HGF did not affect the expression of tight junction proteins, including claudin-1, -3, -4 and -7; occludin; and zonula occludens (ZO)-1. However, fluorescence immunostaining revealed that, in the cell membrane, the levels of ZO-1, but not those of occludin or claudin-4, were transiently decreased 1 h after HGF treatment. The results were further confirmed by western blotting: HGF reduced the amount of ZO-1 protein in the cell membrane fraction concomitantly with an increase in cytoplasmic ZO-1. Furthermore, HGF reduced the interaction between ZO-1 and occludin, and induced the tyrosine phosphorylation of occludin, whereas the phosphorylation status of ZO-1 was not affected by exposure to HGF. Despite a decrease in the ZO-1/occludin interaction, HGF did not affect paracellular permeability to macromolecules.


CONCLUSIONS
HGF alters the subcellular localization of ZO-1, probably through the tyrosine phosphorylation of occludin, which may induce cell dispersion during epithelial restitution.
Digestive Disease and Life-style Related Disease, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima, 890-8520, Japan.
Yuichiro
Y
Nasu
Akio
A
Ido
Shirou
S
Tanoue
Shinichi
S
Hashimoto
Fumisato
F
Sasaki
Shuji
S
Kanmura
Hitoshi
H
Setoyama
Masatsugu
M
Numata
Keita
K
Funakawa
Akihiro
A
Moriuchi
Hiroshi
H
Fujita
Toshio
T
Sakiyama
Hirofumi
H
Uto
Makoto
M
Oketani
Hirohito
H
Tsubouchi
D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D062506:Claudin-4 / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005753:Gastric Mucosa / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D062793:Occludin / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D014407:Tumor Cells, Cultured; D062826:Zonula Occludens-1 Protein / Q000378:metabolism*
D062506:Claudin-4; C568985:OCLN protein, human; D062793:Occludin; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D017228:Hepatocyte Growth Factor