title: Leukocytes Breach Endothelial Barriers by Insertion of Nuclear Lobes and Disassembly of Endothelial Actin Filaments.
abstract: The endothelial cytoskeleton is a barrier for leukocyte transendothelial migration (TEM). Mononuclear and polymorphonuclear leukocytes generate gaps of similar micron-scale size when squeezing through inflamed endothelial barriers in vitro and in vivo. To elucidate how leukocytes squeeze through these barriers, we co-tracked the endothelial actin filaments and leukocyte nuclei in real time. Nuclear squeezing involved either preexistent or de novo-generated lobes inserted into the leukocyte lamellipodia. Leukocyte nuclei reversibly bent the endothelial actin stress fibers. Surprisingly, formation of both paracellular gaps and transcellular pores by squeezing leukocytes did not require Rho kinase or myosin II-mediated endothelial contractility. Electron-microscopic analysis suggested that nuclear squeezing displaced without condensing the endothelial actin filaments. Blocking endothelial actin turnover abolished leukocyte nuclear squeezing, whereas increasing actin filament density did not. We propose that leukocyte nuclei must disassemble the thin endothelial actin filaments interlaced between endothelial stress fibers in order to complete TEM.
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Sagi
authors.initials: S
authors.lastname: Barzilai
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Sandeep Kumar
authors.initials: SK
authors.lastname: Yadav
authors.affiliation: William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK.
authors.forename: Steven
authors.initials: S
authors.lastname: Morrell
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Francesco
authors.initials: F
authors.lastname: Roncato
authors.affiliation: The Irving and Cherna Moskowitz Center for Nano and Bio Nano Imaging, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Klein
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Liat
authors.initials: L
authors.lastname: Stoler-Barak
authors.affiliation: Life Sciences Core Facilities, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Ofra
authors.initials: O
authors.lastname: Golani
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Sara W
authors.initials: SW
authors.lastname: Feigelson
authors.affiliation: Institute of Dental Sciences and Fritz Haber Center for Molecular Dynamics, The Hebrew University of Jerusalem, Jerusalem 9190501, Israel.
authors.forename: Assaf
authors.initials: A
authors.lastname: Zemel
authors.affiliation: William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK.
authors.forename: Sussan
authors.initials: S
authors.lastname: Nourshargh
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel. Electronic address: ronen.alon@weizmann.ac.il.
authors.forename: Ronen
authors.initials: R
authors.lastname: Alon
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D000199:Actins / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology; D015703:Antigens, CD / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D024462:Myosin Type II / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism; D059008:Time-Lapse Imaging; D057705:Transendothelial and Transepithelial Migration / Q000187:drug effects / Q000502:physiology*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099152:Cadherin 5
chemical_list: D000199:Actins; D000577:Amides; D015703:Antigens, CD; D015820:Cadherins; D006576:Heterocyclic Compounds, 4 or More Rings; D053583:Interleukin-1beta; D024462:Myosin Type II; D011725:Pyridines; D054460:rho-Associated Kinases; D000099152:Cadherin 5; C108830:Y 27632; C472645:blebbistatin
keywords: adhesion; inflammation; leukocyte trafficking; migration; shear flow; vasculature