title: Lipid rafts mediate biosynthetic transport to the T lymphocyte uropod subdomain and are necessary for uropod integrity and function.
abstract: Polarized migrating T cells possess 2 poles, the uropod protrusion at the rear and the leading edge at the front, with specific protein composition and function. The influenza virus hemagglutinin (HA) is a prototypical molecule that uses lipid rafts for biosynthetic transport to the apical surface in polarized epithelial Madin-Darby canine kidney (MDCK) cells. In this study, HA was used as a tool to investigate the role of lipid rafts in vectorial protein traffic in polarized T lymphocytes. Results show that newly synthesized HA becomes selectively targeted to the uropod subdomain in polarized T lymphoblasts. HA incorporates into rafts soon after biosynthesis, suggesting that delivery of HA to the uropod occurs through a pathway of transport reminiscent of that used for its specific targeting to the apical surface. HA and the adhesion molecules, intercellular adhesion molecule 3 (ICAM-3), CD44, and CD43, 3 endogenous uropod markers, were detected in surface rafts of T lymphoblasts. Cholesterol, a major component of lipid rafts, was predominantly located in the uropod. Disruption of lipid raft integrity by cholesterol sequestration produced unclustering of ICAM-3 and the loss of uropodia and severely impaired processes that require a polarized phenotype such as intercellular aggregation and cell migration. Collectively, these results indicate that lipid rafts constitute a route for selective targeting of proteins to the uropod and that the rafts are essential for the generation, maintenance, and functionality of T-cell anteroposterior polarity.
authors.affiliation: Severo Ochoa Center for Molecular Biology, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco 280-49 Madrid, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Millán
authors.forename: María C
authors.initials: MC
authors.lastname: Montoya
authors.forename: David
authors.initials: D
authors.lastname: Sancho
authors.forename: Francisco
authors.initials: F
authors.lastname: Sánchez-Madrid
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alonso
mesh_terms: D015703:Antigens, CD; D000943:Antigens, Differentiation; D015815:Cell Adhesion Molecules / Q000378:metabolism / Q000502:physiology; D002449:Cell Aggregation; D016764:Cell Polarity / Q000502:physiology*; D002634:Chemotaxis, Leukocyte; D003599:Cytoskeleton / Q000378:metabolism; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000378:metabolism; D006801:Humans; D021621:Imaging, Three-Dimensional; D021962:Membrane Microdomains / Q000378:metabolism / Q000502:physiology*; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D013601:T-Lymphocytes / Q000166:cytology* / Q000648:ultrastructure
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D015815:Cell Adhesion Molecules; D019267:Hemagglutinin Glycoproteins, Influenza Virus; C483616:ICAM3 protein, human