title: Translocation of tyrosine-phosphorylated TCRzeta chain to glycolipid-enriched membrane domains upon T cell activation.
abstract: Recent studies point to glycolipid-enriched membrane (GEM) microdomains as the critical sites for TCR-mediated signal transduction. However, whether the TCR complex is localized in the GEM domain is not well-defined. In the present study, we analyzed localization of the TCR-CD3 complex in the GEM domain by isolating the GEM fraction with sucrose density gradient centrifugation. Although 10% of TCRzeta chains was localized in the GEM fraction, most of the TCR complexes were excluded from the GEM before and after T cell activation, and the amount of TCRzeta in the GEM was not increased after activation. However, the tyrosine-phosphorylated form of TCRzeta was strongly concentrated in the GEM fraction upon TCR engagement. A kinetic study revealed that tyrosine phosphorylation of TCRzeta occurred initially in the Triton X-100-soluble membrane fraction followed by the accumulation of phosphorylated TCRzeta in the GEM. Thus, these results indicate that phosphorylated TCRzeta migrates into the GEM domains on T cell activation. We speculate that the GEM microdomains may function as a reservoir of activation signals from triggered TCR.
authors.affiliation: School of Allied Health Sciences, Faculty of Medicine Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kosugi
authors.forename: S
authors.initials: S
authors.lastname: Saitoh
authors.forename: S
authors.initials: S
authors.lastname: Noda
authors.forename: K
authors.initials: K
authors.lastname: Yasuda
authors.forename: F
authors.initials: F
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Ogata
authors.forename: T
authors.initials: T
authors.lastname: Hamaoka
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D006017:Glycolipids / Q000378:metabolism*; D006825:Hybridomas; D015151:Immunoblotting; D008213:Lymphocyte Activation; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000032:analysis / Q000378:metabolism*; D013601:T-Lymphocytes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D006017:Glycolipids; D008563:Membrane Lipids; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain