title: Lipopolysaccharide-induced phosphorylation of c-Met tyrosine residue 1003 regulates c-Met intracellular trafficking and lung epithelial barrier function.
abstract: c-Met, the receptor tyrosine kinase whose natural ligand is hepatocyte growth factor, is known to have a key role in cell motility. We have previously shown that lysophosphatidic acid (LPA) induced a decrease in c-Met activation via serine phosphorylation of c-Met at cell-cell contacts. Here, we demonstrate that lipopolysaccharide (LPS) treatment of human bronchial epithelial cells induced internalization of c-Met via phosphorylation at its tyrosine residue 1003. In addition, it induced epithelial barrier dysfunction as evidenced by a decrease in transepithelial resistance (TER) in a time-dependent manner. Pretreatment with a c-Met inhibitor (PHA-665752) or inhibition of protein kinase C (PKC)-α attenuated the LPS-mediated phosphorylation of c-Met and its internalization. LPS-induced c-Met tyrosine 1003 phosphorylation, activation of PKCα, and c-Met internalization were, however, reversed by pretreatment of cells with LPA, which increased c-Met accumulation at cell-cell contacts. Inhibition of LPS-mediated c-Met tyrosine (Y1003) phosphorylation and internalization by prior treatment with PHA-665752, inhibition of PKCα, or overexpression of c-MetY1003A mutant attenuated LPS-induced reduction of TER. Furthermore, we found that c-Met accumulation at cell-cell contacts contributed to LPA-enhanced epithelial barrier integrity, since downregulation of c-Met by specific small-interfering RNA attenuated LPA-increased TER. The data reveal a novel biological function of c-Met in the regulation of lung epithelial barrier integrity.
authors.affiliation: Department of Medicine and the Acute Lung Injury Center of Excellence, the University of Pittsburgh, Pittsburgh, PA 15213, USA. zhaoy3@upmc.edu
authors.forename: Yutong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.forename: Rachel K
authors.initials: RK
authors.lastname: Mialki
authors.forename: Jianxin
authors.initials: J
authors.lastname: Wei
authors.forename: Ernst W
authors.initials: EW
authors.lastname: Spannhake
authors.forename: Ravi
authors.initials: R
authors.lastname: Salgia
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Natarajan
mesh_terms: D015153:Blotting, Western; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D017097:Electric Impedance; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000378:metabolism; D021381:Protein Transport; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019859:Proto-Oncogene Proteins c-met; D051571:Protein Kinase C-alpha
keywords: lysophosphatidic acid; protein kinase C; tyrosine phosphorylation