title: Membrane cholesterol modulates the hyaluronan-binding ability of CD44 in T lymphocytes and controls rolling under shear flow.
abstract: The adhesion of circulating lymphocytes to the surface of vascular endothelial cells is important for their recruitment from blood to secondary lymphoid organs and to inflammatory sites. CD44 is a key adhesion molecule for this interaction and its ligand-binding ability is tightly regulated. Here we show that the hyaluronan-binding ability of CD44 in T cells is upregulated by the depletion of membrane cholesterol with methyl-β-cyclodextrin (MβCD), which disintegrates lipid rafts, i.e. cholesterol- and sphingolipid-enriched membrane microdomains. Increasing concentrations of MβCD led to a dose-dependent decrease in cellular cholesterol content and to upregulation of hyaluronan binding. Additionally, a cholesterol-binding agent filipin also increased hyaluronan binding. Cholesterol depletion caused CD44 to be dispersed from cholesterol-enriched membrane microdomains. Cholesterol depletion also increased the number of cells undergoing rolling adhesion under physiological flow conditions. Our results suggest that the ligand-binding ability of CD44 is governed by its cholesterol-dependent allocation to membrane microdomains at the cell surface. These findings provide novel insight into the regulation of T cell adhesion under blood flow.
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan. murai@orgctl.med.osaka-u.ac.jp
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Murai
authors.forename: Chikara
authors.initials: C
authors.lastname: Sato
authors.forename: Mari
authors.initials: M
authors.lastname: Sato
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Nishiyama
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Suga
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mio
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kawashima
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D018960:Hyaluronan Receptors / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*
chemical_list: C476399:Cd44 protein, mouse; D018960:Hyaluronan Receptors; D006820:Hyaluronic Acid; D002784:Cholesterol
keywords: Adhesion molecule; Cholesterol; Hyaluronan; Lipid raft