title: Hepatocyte growth factor-induced Asef-IQGAP1 complex controls cytoskeletal remodeling and endothelial barrier.
abstract: Hepatocyte growth factor (HGF) attenuates agonist-induced endothelial cell (EC) permeability and increases pulmonary endothelial barrier function via Rac-dependent enhancement of the peripheral actin cytoskeleton. However, the precise mechanisms of HGF effects on the peripheral cytoskeleton are not well understood. This study evaluated a role for Rac/Cdc42-specific guanine nucleotide exchange factor Asef and the multifunctional Rac effector, IQGAP1, in the mechanism of HGF-induced EC barrier enhancement. HGF induced Asef and IQGAP1 co-localization at the cell cortical area and stimulated formation of an Asef-IQGAP1 functional protein complex. siRNA-induced knockdown of Asef or IQGAP1 attenuated HGF-induced EC barrier enhancement. Asef knockdown attenuated HGF-induced Rac activation and Rac association with IQGAP1, and it abolished both IQGAP1 accumulation at the cell cortical layer and IQGAP1 interaction with actin cytoskeletal regulators cortactin and Arp3. Asef activation state was essential for Asef interaction with IQGAP1 and protein complex accumulation at the cell periphery. In addition to the previously reported role of the IQGAP1 RasGAP-related domain in the Rac-dependent IQGAP1 activation and interaction with its targets, we show that the IQGAP1 C-terminal domain is essential for HGF-induced IQGAP1/Asef interaction and Asef-Rac-dependent activation leading to IQGAP1 interaction with Arp3 and cortactin as a positive feedback mechanism of IQGAP1 activation. These results demonstrate a novel feedback mechanism of HGF-induced endothelial barrier enhancement via Asef/IQGAP1 interactions, which regulate the level of HGF-induced Rac activation and promote cortical cytoskeletal remodeling via IQGAP1-Arp3/cortactin interactions.
authors.affiliation: From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Tian
authors.affiliation: From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Gawlak
authors.affiliation: From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637.
authors.forename: Alok S
authors.initials: AS
authors.lastname: Shah
authors.affiliation: From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637.
authors.forename: Katherine
authors.initials: K
authors.lastname: Higginbotham
authors.affiliation: From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637.
authors.forename: Xinyong
authors.initials: X
authors.lastname: Tian
authors.affiliation: the Laboratory of Molecular and Genetic Information, Institute of Molecular and Cellular Biosciences, University of Tokyo, 113-8654 Tokyo, Japan, and.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawasaki
authors.affiliation: the Laboratory of Molecular and Genetic Information, Institute of Molecular and Cellular Biosciences, University of Tokyo, 113-8654 Tokyo, Japan, and.
authors.forename: Tetsu
authors.initials: T
authors.lastname: Akiyama
authors.affiliation: the Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: David B
authors.initials: DB
authors.lastname: Sacks
authors.affiliation: From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, abirukov@medicine.bsd.uchicago.edu.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Birukova
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D015153:Blotting, Western; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D047468:Immunoprecipitation; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D064067:Rho Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: C576602:ARHGEF4 protein, human; C101203:IQ motif containing GTPase activating protein 1; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors; D020703:ras GTPase-Activating Proteins; D017228:Hepatocyte Growth Factor; D020744:rac GTP-Binding Proteins
keywords: Endothelium; Lung Injury; Permeability; Rac GTPases; Signal Transduction; Vascular Biology