A physical and functional link between cholesterol and tetraspanins.
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.
Charrin
Stéphanie
S
Inserm U268, Institut André Lwoff, Université Paris XI, Villejuif, France.
Manié
Serge
S
Thiele
Christoph
C
Billard
Martine
M
Gerlier
Denis
D
Boucheix
Claude
C
Rubinstein
Eric
E
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
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