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The ST3Gal-I sialyltransferase controls CD8+ T lymphocyte homeostasis by modulating O-glycan biosynthesis
J J Priatel1, D Chui, N Hiraoka
1Howard Hughes Medical Institute, the Glycobiology Research and Training Center, and Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla 92093, USA.
Abstract:
T lymphocyte activation evokes distinct changes in cell surface O-glycans. CD8+ T cells undergo an elimination of sialic acid on core 1 O-glycans and an induction of core 2 O-glycans until either apoptotic death or differentiation into memory cells. We find that the ST3Gal-I sialyltransferase is required for core 1 O-glycan sialylation and its deficiency induces core 2 O-glycan biosynthesis. Apoptosis ensues with the loss of peripheral CD8+ T cells in the absence of immune stimulation. Cell surface ligation of the ST3Gal-I substrate CD43 recapitulates this phenotype by a caspase 3-independent mechanism. Control of core 1 O-glycan sialylation in T lymphocytes by ST3Gal-I comprises a homeostatic mechanism that eliminates CD8+ T cells by apoptosis while facilitating the production of viable CD8+ memory T cells.