title: Endothelial LSP1 Modulates Extravascular Neutrophil Chemotaxis by Regulating Nonhematopoietic Vascular PECAM-1 Expression.
abstract: During inflammation, leukocyte-endothelial cell interactions generate molecular signals that regulate cell functions. The Ca(2+)- and F-actin-binding leukocyte-specific protein 1 (LSP1) expressed in leukocytes and nonhematopoietic endothelial cells is pivotal in regulating microvascular permeability and leukocyte recruitment. However, cell-specific function of LSP1 during leukocyte recruitment remains elusive. Using intravital microscopy of cremasteric microvasculature of chimeric LSP1-deficient mice, we show that not neutrophil but endothelial LSP1 regulates neutrophil transendothelial migration and extravascular directionality without affecting the speed of neutrophil migration in tissue in response to CXCL2 chemokine gradient. The expression of PECAM-1-sensitive α6β1 integrins on the surface of transmigrated neutrophils was blunted in mice deficient in endothelial LSP1. Functional blocking studies in vivo and in vitro elucidated that α6β1 integrins orchestrated extravascular directionality but not the speed of neutrophil migration. In LSP1-deficient mice, PECAM-1 expression was reduced in endothelial cells, but not in neutrophils. Similarly, LSP1-targeted small interfering RNA silencing in murine endothelial cells mitigated mRNA and protein expression of PECAM-1, but not ICAM-1 or VCAM-1. Overexpression of LSP1 in endothelial cells upregulated PECAM-1 expression. Furthermore, the expression of transcription factor GATA-2 that regulates endothelial PECAM-1 expression was blunted in LSP1-deficient or LSP1-silenced endothelial cells. The present study unravels endothelial LSP1 as a novel cell-specific regulator of integrin α6β1-dependent neutrophil extravascular chemotactic function in vivo, effective through GATA-2-dependent transcriptional regulation of endothelial PECAM-1 expression.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada;
authors.forename: Mokarram
authors.initials: M
authors.lastname: Hossain
authors.affiliation: Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada;
authors.forename: Syed M
authors.initials: SM
authors.lastname: Qadri
authors.affiliation: Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada;
authors.forename: Najia
authors.initials: N
authors.lastname: Xu
authors.affiliation: Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada;
authors.forename: Yang
authors.initials: Y
authors.lastname: Su
authors.affiliation: Department of Surgery, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada; and.
authors.forename: Francisco S
authors.initials: FS
authors.lastname: Cayabyab
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario N6A 5C1, Canada.
authors.forename: Bryan
authors.initials: B
authors.lastname: Heit
authors.affiliation: Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada; lixin.liu@usask.ca.
authors.forename: Lixin
authors.initials: L
authors.lastname: Liu
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D002478:Cells, Cultured; D054426:Chemokine CXCL2 / Q000276:immunology / Q000494:pharmacology; D002634:Chemotaxis, Leukocyte / Q000235:genetics / Q000276:immunology*; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression / Q000276:immunology; D015151:Immunoblotting; D057507:Mice, 129 Strain; D018345:Mice, Knockout; D008840:Microfilament Proteins; D018613:Microscopy, Confocal; D020556:Neutrophil Infiltration / Q000235:genetics / Q000276:immunology; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059008:Time-Lapse Imaging / Q000379:methods; D057705:Transendothelial and Transepithelial Migration / Q000187:drug effects / Q000235:genetics / Q000276:immunology
chemical_list: D002135:Calcium-Binding Proteins; D054426:Chemokine CXCL2; C057701:Lsp1 protein, mouse; D008840:Microfilament Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1