title: Tight junctions contain oligomeric protein assembly critical for maintaining blood-brain barrier integrity in vivo.
abstract: Tight junctions (TJs) are major components of the blood-brain barrier (BBB) that physically obstruct the interendothelial space and restrict paracellular diffusion of blood-borne substances from the peripheral circulation to the CNS. TJs are dynamic structures whose intricate arrangement of oligomeric transmembrane and accessory proteins rapidly alters in response to external stressors to produce changes in BBB permeability. In this study, we investigate the constitutive trafficking of the TJ transmembrane proteins occludin and claudin-5 that are essential for forming the TJ seal between microvascular endothelial cells that inhibits paracellular diffusion. Using a novel, detergent-free OptiPrep density-gradient method to fractionate rat cerebral microvessels, we identify a plasma membrane lipid raft domain that contains oligomeric occludin and claudin-5. Our data suggest that oligomerization of occludin involves disulfide bond formation within transmembrane regions, and that assembly of the TJ oligomeric protein complex is facilitated by an oligomeric caveolin scaffold. This is the first time that distribution of oligomeric TJ transmembrane proteins within plasma membrane lipid rafts at the BBB has been examined in vivo. The findings reported in this study are critical to understand the mechanism of assembly of the TJ multiprotein complex that is essential for maintaining BBB integrity.
authors.affiliation: Department of Medical Pharmacology, University of Arizona College of Medicine, 1501 N. Campbell Ave, Tucson, Arizona, USA. gwenm@email.arizona.edu
authors.forename: Gwen
authors.initials: G
authors.lastname: McCaffrey
authors.forename: William D
authors.initials: WD
authors.lastname: Staatz
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Quigley
authors.forename: Nicole
authors.initials: N
authors.lastname: Nametz
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Seelbach
authors.forename: Chris R
authors.initials: CR
authors.lastname: Campos
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Brooks
authors.forename: Richard D
authors.initials: RD
authors.lastname: Egleton
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Davis
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000196:embryology* / Q000502:physiology*; D015153:Blotting, Western; D002196:Capillaries / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D062507:Claudin-5; D004220:Disulfides / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D021962:Membrane Microdomains / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000502:physiology*; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism* / Q000502:physiology*; D062826:Zonula Occludens-1 Protein
chemical_list: D062507:Claudin-5; C491510:Cldn5 protein, rat; D004220:Disulfides; D007202:Indicators and Reagents; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D062793:Occludin; C568987:Ocln protein, rat; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein