The extracellular part of zeta is buried in the T cell antigen receptor complex.
The zeta chain is a key component of the T cell antigen receptor (TCR-CD3) complex, required for the expression of the receptor on the cell surface. It contains an extremely small extracellular (EC) part of nine amino acids. Interestingly, the length, but not the sequence, of the zeta EC has been highly conserved through evolution. Here, we examined the effect of increasing the length of human zeta EC on TCR-CD3 assembly and surface expression. Appending a 30 kDa polypeptide to the N-terminus of zeta completely abolished assembly and transport of the TCR-CD3 to the cell surface. Addition of only 17 amino acids, including the HA-tag (HAzeta), strongly reduced the efficiency of TCR-CD3 assembly and led to reduced expression on the surface, suggesting that the short zeta EC region is located within the receptor complex. In Blue Native gels (BN-PAGE) these receptors had a normal size, indicating that they have a stoichiometry of alphabetagammaepsilondeltaepsilonzetazeta. In resting TCR-CD3s the HA-tag, and thus the zeta EC region, was not accessible for anti-HA antibody binding, demonstrating that it was indeed buried in a cavity within the receptor complex. However, prolonged stimulation with antigen permitted the access of the anti-HA antibody, thus suggesting that stimulation led to architectural changes in the TCR-CD3.
Minguet
Susana
S
Max Planck Institute of Immunobiology and Faculty of Biology III, University of Freiburg, Stübeweg 51, 79108 Freiburg, Germany.
Swamy
Mahima
M
Dopfer
Elaine P
EP
Dengler
Eva
E
Alarcón
Balbino
B
Schamel
Wolfgang W A
WW
D000595:Amino Acid Sequence; D000818:Animals; D017252:CD3 Complex / Q000737:chemistry* / Q000276:immunology*; D002460:Cell Line; D005110:Extracellular Space; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000737:chemistry* / Q000276:immunology*; D016415:Sequence Alignment; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*
D017252:CD3 Complex; C121704:CD3 antigen, zeta chain; D017260:Receptor-CD3 Complex, Antigen, T-Cell