Molecular modelling and endoplasmic reticulum retention of mutated TCR/CD3 complexes.
T cell receptor (TCR)/CD3 complex assembly takes place in the endoplasmic reticulum (ER). Normal TCR/CD3 complexes egress from the ER to the cis-Golgi, where the interaction with zeta2 homodimers occurs. This interaction leads to further uncontrolled transport of TCR/CD3/zeta molecules to the cell surface. The purpose of the present experiments was to determine firstly the basis for the impact of the Phe195/216 --> Val mutations on TCR/CD3 expression in Jurkat cells, and secondly why mutated J79-cell TCRalphabeta/CD3 hexamers are prevented from interacting with zeta2 homodimers. We found that Phe --> Val mutations cause serious perturbations in a so far undefined hydrophobic area formed by the two Phe195/216 on beta-strand F and aromatic/large hydrophobic amino acids on neighboring beta-strands B and A in Calpha and Cbeta domains, respectively. In addition, TCR/CD3 hexamers and zeta2 homodimers colocalize in normal Jurkat T cells, in revertant J79r58 cells, and in J79 cells transfected with wild-type TCRalpha cDNA but not in J79 mutant cells (confocal microscopy). Furthermore, mutated TCR/CD3 complexes seem to be actively retained in the ER in J79 cells but not in revertant J79r58 cells by a nondominant mechanism. We propose that a hitherto undefined ER-retention molecule controls both the protein structure and egress of TCR/CD3 complexes from the ER of alphabeta and gammadelta T cells.
Arnaud
J
J
Unité de Physiopathologie Cellulaire et Moléculaire, CNRS-UPR 2163, Institut Claude de Preval, IFR 30, CHU de PURPAN, 31059 Toulouse Cedex 03, France.
Erard
M
M
Martin
E
E
Llobera
R
R
Gouaillard
C
C
Constans
J
J
Rubin
B
B
D020126:Brefeldin A / Q000494:pharmacology; D017252:CD3 Complex / Q000378:metabolism; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008958:Models, Molecular; D009154:Mutation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D017252:CD3 Complex; C121704:CD3 antigen, zeta chain; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D020126:Brefeldin A