Developmental regulation of the TCR zeta-chain. Differential expression and tyrosine phosphorylation of the TCR zeta-chain in resting immature and mature T lymphocytes.
The zeta subunit of the TCR complex targets receptor surface expression, is phosphorylated on tyrosine residues upon T cell activation, and is implicated in signal transduction after TCR ligation. Here we show that, although intrathymic expression of the murine TCR-associated zeta-chain relative to the other chains of the Ag receptor complex remains unchanged during early thymocyte development, there is a doubling of TCR-associated zeta-chain surface expression upon thymocyte maturation. The ratio of tyrosine-phosphorylated relative to nonphosphorylated TCR-associated zeta-chain also changes with thymocyte development. This ratio was quantified after the purification and detergent extraction of receptor complexes from freshly isolated immature or mature thymocytes. Immunoprecipitation of the zeta-chain released from the complex allowed for the isolation of the tyrosine-phosphorylated and nonphosphorylated forms of TCR-associated zeta-chain. Intracellular free zeta-chain was characterized by immunoprecipitation after clearing the cell lysate of intact TCR complexes. Densitometric analysis of immunoblots indicated that surface phosphorylated zeta-chain is more abundant in immature relative to mature T cell populations, whereas the inverse is true of intracellular phosphorylated zeta-chain. Surface phosphorylated zeta-chain also migrated at a higher m.w. than its cytoplasmic counterpart, suggesting that it is more highly modified on some or all of its available tyrosines. These findings demonstrate that the stoichiometry and post-translational modification of the TCR complex are regulated, in vivo, and may determine the functional maturation of T cell signaling, selection, and activation.
Rozdzial
M M
MM
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
Kubo
R T
RT
Turner
S L
SL
Finkel
T H
TH
D000818:Animals; D000831:Animals, Newborn / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D000954:Antigens, Surface / Q000378:metabolism; D002454:Cell Differentiation; D003593:Cytoplasm / Q000378:metabolism; D015870:Gene Expression; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D019000:Phosphotyrosine; D012333:RNA, Messenger / Q000235:genetics; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D008565:Membrane Proteins; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D019000:Phosphotyrosine; D014443:Tyrosine