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Non‐glycosylated human B7‐1(CD80) retains the capacity to bind its counter‐receptors 1
Author(s) -
Chen Aoshuang,
Meyerson Howard J.,
Salvekar Anupama,
Tykocinski Mark L.
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00460-8
Subject(s) - tunicamycin , glycosylation , cd80 , receptor , n linked glycosylation , microbiology and biotechnology , immunoprecipitation , flow cytometry , biology , glycoprotein , recombinant dna , t cell , cd28 , cell culture , chemistry , biochemistry , in vitro , immunology , cytotoxic t cell , endoplasmic reticulum , immune system , genetics , cd40 , unfolded protein response , gene , glycan
Though the cell surface‐associated costimulator B7‐1(CD80) is known to be highly N ‐glycosylated, the functional significance of this N ‐glycosylation has not been evaluated. Two experimental approaches were taken to assess the influence of N ‐glycosylation on human B7‐1 function. First, stable K562 transfectants expressing human B7‐1 were treated with the N ‐glycosylation inhibitor tunicamycin. This treatment reduced the levels of B7‐1 at the cell surface as judged by both indirect immunofluorescence/flow cytometry and immunoprecipitation analyses. Significantly, the non‐glycosylated cell surface‐associated B7‐1 on tunicamycin‐treated cells retained the capacity to bind CTLA‐4·Ig, a soluble derivative of the CTLA‐4(CD152) counter‐receptor. Second, experiments were performed with bacterially‐produced non‐glycosylated derivatives of human B7‐1, comprising either the complete B7‐1 extracellular domain (hB7‐1·ed) or the membrane‐proximal IgC‐homologue domain of B7‐1 in isolation (hB7‐1·IgC). While the hB7‐1·IgC derivative failed to bind to CTLA‐4, the larger hB7‐1·ed derivative associated with CTLA‐4·Ig in cell‐free binding assays. Futhermore, recombinant hB7‐1·ed effectively blocked B7‐1‐mediated costimulation in an in vitro T cell proliferation assay, suggesting that this soluble non‐glycosylated B7‐1 derivative is capable of engaging CD28, the B7 counter‐receptor implicated in T cell activation. Taken together, these data indicate that the N ‐glycosylation of B7‐1 is not required for its association with counter‐receptors. Moreover, the findings pave the way for the therapeutic use of recombinant bacterial B7‐1 derivatives as competitive inhibitors of B7‐mediated signals.