title: Cross talk between paxillin and Rac is critical for mediation of barrier-protective effects by oxidized phospholipids.
abstract: We previously reported that the barrier-protective effects of oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) on pulmonary endothelial cells (ECs) delineate the role of Rac- and Cdc42-dependent mechanisms and described the involvement of the focal adhesion (FA) protein paxillin in enhancement of the EC barrier upon OxPAPC challenge. This study examined a potential role of paxillin in the feedback mechanism of Rac regulation by FAs in OxPAPC-stimulated ECs. Our results demonstrate that OxPAPC induced Rac-dependent, Rho-independent peripheral accumulation of paxillin-containing FAs and time-dependent paxillin phosphorylation. Molecular inhibition of Rac decreased association of paxillin with the Rac-specific guanine nucleotide exchange factor beta-PIX. Molecular inhibition of paxillin also attenuated OxPAPC-induced enhancement of adherens junctions critical for the EC barrier-protective response, accumulation of vascular endothelial cadherin in the membrane fractions, and decreased activation of Rac and its effector p21-activated kinase (PAK1). Expression of paxillin with a mutated PAK1-dependent phosphorylation site (S273A) attenuated OxPAPC-induced PAK1 activation and the EC barrier-protective response. These results suggest that PAK1-specific paxillin phosphorylation at Ser(273) is critically involved in the positive-feedback regulation of the Rac-PAK1 pathway and may contribute to sustained enhancement of the EC barrier caused by oxidized phospholipids.
authors.affiliation: Dept. of Medicine, University of Chicago, Chicago, IL 60637, USA. kbirukov@medicine.bsd.uchicago.edu
authors.forename: Anna A
authors.initials: AA
authors.lastname: Birukova
authors.forename: Elena
authors.initials: E
authors.lastname: Alekseeva
authors.forename: Ivan
authors.initials: I
authors.lastname: Cokic
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Turner
authors.forename: Konstantin G
authors.initials: KG
authors.lastname: Birukov
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D017097:Electric Impedance; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D051379:Mice; D051419:Paxillin / Q000172:deficiency / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000494:pharmacology; D010766:Phosphorylation; D021381:Protein Transport; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D054462:p21-Activated Kinases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; C496061:PXN protein, human; D051419:Paxillin; D010713:Phosphatidylcholines; C472349:oxidized-L-alpha-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins