title: Tiam1 and betaPIX mediate Rac-dependent endothelial barrier protective response to oxidized phospholipids.
abstract: Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC) exhibits potent barrier protective effects on pulmonary endothelium, which are mediated by small GTPases Rac and Cdc42. However, upstream mechanisms of OxPAPC-induced small GTPase activation are not known. We studied involvement of Rac/Cdc42-specific guanine nucleotide exchange factors (GEFs) Tiam1 and betaPIX in OxPAPC-induced Rac activation, cytoskeletal remodeling, and barrier protective responses in the human pulmonary endothelial cells (EC). OxPAPC induced membrane translocation of Tiam1, betaPIX, Cdc42, and Rac, but did not affect intracellular distribution of Rho and Rho-specific GEF p115-RhoGEF. Protein depletion of Tiam1 and betaPIX using siRNA approach abolished OxPAPC-induced activation of Rac and its effector PAK1. EC transfection with Tiam1-, betaPIX-, or PAK1-specific siRNA dramatically attenuated OxPAPC-induced barrier enhancement, peripheral actin cytoskeletal enhancement, and translocation of actin-binding proteins cortactin and Arp3. These results show for the first time that Tiam1 and betaPIX mediate OxPAPC-induced Rac activation, cytoskeletal remodeling, and barrier protective response in pulmonary endothelium.
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Birukova
authors.forename: Irina
authors.initials: I
authors.lastname: Malyukova
authors.forename: Arsen
authors.initials: A
authors.lastname: Mikaelyan
authors.forename: Panfeng
authors.initials: P
authors.lastname: Fu
authors.forename: Konstantin G
authors.initials: KG
authors.lastname: Birukov
mesh_terms: D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D017097:Electric Impedance; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C576600:ARHGEF1 protein, human; C576606:ARHGEF7 protein, human; D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D010713:Phosphatidylcholines; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; C472349:oxidized-L-alpha-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine; C515903:PAK1 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020559:Monomeric GTP-Binding Proteins; D020744:rac GTP-Binding Proteins