title: Hepatocyte growth factor triggers distinct mechanisms of Asef and Tiam1 activation to induce endothelial barrier enhancement.
abstract: Previous reports described an important role of hepatocyte growth factor (HGF) in mitigation of pulmonary endothelial barrier dysfunction and cell injury induced by pathologic agonists and mechanical forces. HGF protective effects have been associated with Rac-GTPase signaling pathway activated by Rac-specific guanine nucleotide exchange factor Tiam1 and leading to enhancement of intercellular adherens junctions. This study tested involvement of a novel Rac-specific activator, Asef, in endothelial barrier enhancement by HGF and investigated a mechanism of HGF-induced Asef activation. Si-RNA-based knockdown of Tiam1 and Asef had an additive effect on attenuation of HGF-induced Rac activation and endothelial cell (EC) barrier enhancement. Tiam1 and Asef activation was abolished by pharmacologic inhibitors of HGF receptor and PI3-kinase. In contrast to Tiam1, Asef interacted with APC and associated with microtubule fraction upon HGF stimulation. EC treatment by low dose nocodazole to inhibit peripheral microtubule dynamics partially attenuated HGF-induced Asef peripheral translocation, but had negligible effect on Tiam1 translocation. These effects were associated with attenuation of HGF-induced barrier enhancement in EC pretreated with low ND dose and activation of Rac and its cytoskeletal effectors PAK1 and cortactin. These data demonstrate, that in addition to microtubule-independent Tiam1 activation, HGF engages additional microtubule- and APC-dependent pathway of Asef activation. These mechanisms may complement each other to provide the fine tuning of Rac signaling and endothelial barrier enhancement in response to various agonists.
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Higginbotham
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Gawlak
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Nurgul
authors.initials: N
authors.lastname: Moldobaeva
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Alok
authors.initials: A
authors.lastname: Shah
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA. Electronic address: abirukov@medicine.bsd.uchicago.edu.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Birukova
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D064067:Rho Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D050257:Tubulin Modulators; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C555337:APC protein, human; C576602:ARHGEF4 protein, human; D025601:Adenomatous Polyposis Coli Protein; D020662:Guanine Nucleotide Exchange Factors; C066855:HGF protein, human; D064067:Rho Guanine Nucleotide Exchange Factors; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; D050257:Tubulin Modulators; D017228:Hepatocyte Growth Factor; D019869:Phosphatidylinositol 3-Kinases; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins; D015739:Nocodazole
keywords: Cytoskeleton; Endothelium; Guanine nucleotide exchange factor; HGF; Permeability; Rac GTPase
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