Lymphocyte function-associated antigen 1 (LFA-1) contains sulfated N-linked oligosaccharides

The murine lymphocyte function-associated antigen 1 (LFA-1) is a glycoprotein heterodimer consisting of an Mr 180,000 α-chain and an Mr 95,000 β-chain. Although LFA-1 has been studied extensively in the past few years due to its involvement in various antigen-specific T lymphocyte responses, virtually nothing is known about its glycosylation. In this report, we have analyzed the oligosaccharide moieties of the murine LFA-1 molecule. Utilizing a T lymphoma cell line, EL-4, it was found that [³⁵S] sulfate, [³H]glucosamine, [³H]mannose, and [³H]fucose were incorporated into both the α- and β-chains of LFA-1. Isolated α- and β-chains from anti-LFA-1 immunoprecipitates of [³H]glucosamine-labeled NP-40 lysates were subjected to tryptic-chymotryptic digestion, and the resulting glycopeptides were fractionated by reverse-phase high performance liquid chromatography. Five major [³H]glucosamine-labeled glycopeptides were generated by this procedure from each of the two polypeptide chains. Treatment of the individual glycopeptides with almond emulsin peptide:N-glycosidase or Endo F demonstrated that the [³H]glucosamine label existed almost entirely in N-linked oligosaccharide structures (Mr 5000 to 10,000). By using similar techniques, the majority of the [³⁵S]sulfate moieties were also found covalently bound to N-linked oligosaccharides. In addition, both [³⁵S]sulfate-labeled α- and β-chains were susceptible to Keratanase and endo-β-galactosidase digestions, indicating the presence of sulfated N-acetyllactosamine sequences. The expression of [³⁵S]sulfate-labeled LFA-1 on various cell types was also examined. LFA-1 was found to be sulfated only on thymocytes and splenic T cells, but not on macrophages, splenic B, or bone marrow cells.