title: Cholesterol and sphingomyelin drive ligand-independent T-cell antigen receptor nanoclustering.
abstract: The T-cell antigen receptor (TCR) exists in monomeric and nanoclustered forms independently of antigen binding. Although the clustering is involved in the regulation of T-cell sensitivity, it is unknown how the TCR nanoclusters form. We show that cholesterol is required for TCR nanoclustering in T cells and that this clustering enhances the avidity but not the affinity of the TCR-antigen interaction. Investigating the mechanism of the nanoclustering, we found that radioactive photocholesterol specifically binds to the TCRβ chain in vivo. In order to reduce the complexity of cellular membranes, we used a synthetic biology approach and reconstituted the TCR in liposomes of defined lipid composition. Both cholesterol and sphingomyelin were required for the formation of TCR dimers in phosphatidylcholine-containing large unilamellar vesicles. Further, the TCR was localized in the liquid disordered phase in giant unilamellar vesicles. We propose a model in which cholesterol and sphingomyelin binding to the TCRβ chain causes TCR dimerization. The lipid-induced TCR nanoclustering enhances the avidity to antigen and thus might be involved in enhanced sensitivity of memory compared with naive T cells. Our work contributes to the understanding of the function of specific nonannular lipid-membrane protein interactions.
authors.affiliation: Max Planck Institute of Immunobiology and Epigenetics, 79108 Freiburg, Germany.
authors.forename: Eszter
authors.initials: E
authors.lastname: Molnár
authors.forename: Mahima
authors.initials: M
authors.lastname: Swamy
authors.forename: Martin
authors.initials: M
authors.lastname: Holzer
authors.forename: Katharina
authors.initials: K
authors.lastname: Beck-García
authors.forename: Remigiusz
authors.initials: R
authors.lastname: Worch
authors.forename: Christoph
authors.initials: C
authors.lastname: Thiele
authors.forename: Gernot
authors.initials: G
authors.lastname: Guigas
authors.forename: Kristian
authors.initials: K
authors.lastname: Boye
authors.forename: Immanuel F
authors.initials: IF
authors.lastname: Luescher
authors.forename: Petra
authors.initials: P
authors.lastname: Schwille
authors.forename: Rolf
authors.initials: R
authors.lastname: Schubert
authors.forename: Wolfgang W A
authors.initials: WW
authors.lastname: Schamel
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D002784:Cholesterol / Q000378:metabolism*; D016000:Cluster Analysis; D003432:Cross-Linking Reagents / Q000378:metabolism; D006649:Histocompatibility Antigens / Q000378:metabolism; D006801:Humans; D008024:Ligands; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry*; D010455:Peptides / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D021122:Protein Subunits / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism*; D011990:Receptors, Transferrin; D013109:Sphingomyelins / Q000378:metabolism*; D053835:Unilamellar Liposomes / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D006649:Histocompatibility Antigens; D008024:Ligands; D010455:Peptides; D010713:Phosphatidylcholines; D021122:Protein Subunits; D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D011990:Receptors, Transferrin; D013109:Sphingomyelins; D053835:Unilamellar Liposomes; D002784:Cholesterol