Translocation of tyrosine-phosphorylated TCRzeta chain to glycolipid-enriched membrane domains upon T cell activation.
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.
Kosugi
A
A
School of Allied Health Sciences, Faculty of Medicine Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan.
Saitoh
S
S
Noda
S
S
Yasuda
K
K
Hayashi
F
F
Ogata
M
M
Hamaoka
T
T
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
D006017:Glycolipids; D008563:Membrane Lipids; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain