title: Critical role of S1PR1 and integrin β4 in HGF/c-Met-mediated increases in vascular integrity.
abstract: Vascular endothelial cell (EC) barrier integrity is critical to vessel homeostasis whereas barrier dysfunction is a key feature of inflammatory disorders and tumor angiogenesis. We previously reported that hepatocyte growth factor (HGF)-mediated increases in EC barrier integrity are signaled through a dynamic complex present in lipid rafts involving its receptor, c-Met. We extended these observations to confirm that S1PR1 (sphingosine 1-phosphate receptor 1) and integrin β4 (ITGB4) are essential participants in HGF-induced EC barrier enhancement. Immunoprecipitation experiments demonstrated HGF-mediated recruitment of c-Met, ITGB4 and S1PR1 to caveolin-enriched lipid rafts in human lung EC with direct interactions of c-Met with both S1PR1 and ITGB4 accompanied by c-Met-dependent S1PR1 and ITGB4 transactivation. Reduced S1PR1 expression (siRNA) attenuated both ITGB4 and Rac1 activation as well as c-Met/ITGB4 interaction and resulted in decreased transendothelial electrical resistance. Furthermore, reduced ITGB4 expression attenuated HGF-induced c-Met activation, c-Met/S1PR1 interaction, and effected decreases in S1P- and HGF-induced EC barrier enhancement. Finally, the c-Met inhibitor, XL880, suppressed HGF-induced c-Met activation as well as S1PR1 and ITGB4 transactivation. These results support a critical role for S1PR1 and ITGB4 transactivation as rate-limiting events in the transduction of HGF signals via a dynamic c-Met complex resulting in enhanced EC barrier integrity.
authors.affiliation: Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, and Sleep Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Ephstein
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Singleton
authors.forename: Weiguo
authors.initials: W
authors.lastname: Chen
authors.forename: Lichun
authors.initials: L
authors.lastname: Wang
authors.forename: Ravi
authors.initials: R
authors.lastname: Salgia
authors.forename: Prasad
authors.initials: P
authors.lastname: Kanteti
authors.forename: Steven M
authors.initials: SM
authors.lastname: Dudek
authors.forename: Joe G N
authors.initials: JG
authors.lastname: Garcia
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Jacobson
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004594:Electrophysiology; D042783:Endothelial Cells / Q000166:cytology*; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006801:Humans; D039663:Integrin beta4 / Q000378:metabolism*; D008168:Lung / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism; D008833:Microcirculation; D008954:Models, Biological; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D049349:Receptors, Lysosphingolipid / Q000378:metabolism*; D000081025:Sphingosine-1-Phosphate Receptors; D013912:Threonine / Q000737:chemistry; D015533:Transcriptional Activation; D014443:Tyrosine / Q000737:chemistry; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: C059834:ITGB4 protein, human; D039663:Integrin beta4; C107953:RAC1 protein, human; D034741:RNA, Small Interfering; D049349:Receptors, Lysosphingolipid; C477362:S1PR1 protein, human; D000081025:Sphingosine-1-Phosphate Receptors; D013912:Threonine; D014443:Tyrosine; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D020830:rac1 GTP-Binding Protein