title: A physical and functional link between cholesterol and tetraspanins.
abstract: By interacting with each others, the tetraspanins are thought to assemble a network of molecular interactions, the tetraspanin web. These tetraspanin/tetraspanin interactions involve in part the palmitoylation of the proteins. We show that tetraspanins interact with cholesterol as indicated by the precipitation of tetraspanin/tetraspanin complexes by digitonin, a cholesterol-precipitating reagent, and the labeling of the tetraspanins CD9, CD81 and CD82 with a photoactivatable cholesterol in vivo. Cholesterol may participate to the interaction of tetraspanins with each other since digitonin-precipitation of tetraspanins was correlated with their mutual interaction, and because these interactions were disrupted following cholesterol depletion by methyl-beta-cyclodextrin (MbetaCD) treatment, or cholesterol sequestration by saponin. A mutant CD9 molecule lacking all palmitoylation sites was not precipitated by digitonin under conditions in which wild-type CD9 was precipitated, indicating a role of palmitoylation for the interaction with cholesterol. Finally, upon ligation of tetraspanins on the surface of a lymphoid B cell line, the tyrosine phosphorylation of several proteins, including the vav nucleotide exchange factor, was inhibited when cells were pretreated with MbetaCD, and increased when they were treated with MbetaCD/cholesterol complexes. Thus, there is a physical and functional link between tetraspanins and cholesterol.
authors.affiliation: Inserm U268, Institut André Lwoff, Université Paris XI, Villejuif, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Charrin
authors.forename: Serge
authors.initials: S
authors.lastname: Manié
authors.forename: Christoph
authors.initials: C
authors.lastname: Thiele
authors.forename: Martine
authors.initials: M
authors.lastname: Billard
authors.forename: Denis
authors.initials: D
authors.lastname: Gerlier
authors.forename: Claude
authors.initials: C
authors.lastname: Boucheix
authors.forename: Eric
authors.initials: E
authors.lastname: Rubinstein
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D004072:Digitonin / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D051567:Proto-Oncogene Proteins c-vav; D012503:Saponins / Q000378:metabolism; D060245:Tetraspanin 29; D014316:Tritium / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; C554869:CD9 protein, human; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D015513:Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D012503:Saponins; D060245:Tetraspanin 29; C496618:VAV1 protein, human; D014316:Tritium; D014443:Tyrosine; D002784:Cholesterol; D004072:Digitonin