Calnexin associates with monomeric and oligomeric (disulfide-linked) CD3δ proteins in murine T lymphocytes

The antigen-binding receptor expressed on most T lymphocytes consists of disulfide-linked clonotypic alpha beta heterodimers noncovalently associated with monomeric CD3 gamma,delta,epsilon proteins and disulfide-linked xi xi homodimers, collectively referred to as the T cell antigen receptor (TCR) complex. Here, we examined and compared the disulfide linkage status of newly synthesized TCR proteins in murine CD4(+)CD8(+) thymocytes and splenic T cells. These studies demonstrate that CD3 delta proteins exist as both monomeric and oligomeric (disulfide-linked) species that differentially assemble with CD3 epsilon subunits in CD4(+)CD8(+) thymocytes and splenic T cells. Interestingly, unlike previous results on glucose trimming and TCR assembly of CD3 delta proteins ire splenic T cells (Vam Leeuwen, J. E. M., and K. P. Kearse (1996) J. Biol. Chem. 271, 9660-9665), we found that glucose residues were mot invariably removed from CD3 delta glycoproteins prior to their assembly with CD3 epsilon subunits in CD4(+)CD8(+) thymocytes. Finally, these studies show that calnexin associates with both monomeric and disulfide-linked CD3 delta proteins in murine T cells. The data in the current report demonstrate that CD3 delta proteins exist as both monomeric and disulfide-linked molecules in murine T cells that differentially associate with partner TCR chains in CD4(+)CD8(+) thymocytes and splenic T cells. These results are consistent with the concept that folding and assembly of CD3 delta proteins is a function of their oxidation state.