An alternate core 2 β1,6-N-acetylglucosaminyltransferase selectively contributes to P-selectin ligand formation in activated CD8 T cells

Core 2 β1,6-N-acetylglucosaminyltransferase (C2GlcNAcT) synthesizes essential core 2 O-glycans on selectin ligands, which mediate cell-cell adhesion required for lymphocyte trafficking. Although gene-deletion studies have implicated C2GlcNAcT-I in controlling selectin ligand-mediated cell trafficking, little is known about the role of the two other core 2 isoenzymes, C2GlcNAcT-II and C2GlcNAcT-III. We show that C2GlcNAcT-I-independent P-selectin ligand formation occurs in activated C2GlcNAcT-I^null CD8 T cells. These CD8 T cells were capable of rolling under shear flow on immobilized P-selectin in a P-selectin glycoprotein ligand 1-dependent manner. RT-PCR analysis identified significant levels of C2GlcNAcT-III RNA, identifying this enzyme as a possible source of core 2 enzyme activity. Up-regulation of P-selectin ligand correlated with altered cell surface binding of the core 2-sensitive mAb 1B11, indicating that CD43 and CD45 are also physiological targets for this alternate C2GlcNAcT enzyme. Furthermore, C2GlcNAcT-I-independent P-selectin ligand induction was observed in an in vivo model. HY^tg CD8 T cells from C2GlcNAcT-I ^null donors transferred into male recipients expressed P-selectin ligand in response to male Ag, although at reduced levels compared with wild-type HY^tg CD8 T cells. Our data demonstrate that multiple C2GlcNAcT enzymes can contribute to P-selectie ligand formation and may cooperate with C2GlcNAcT-I in the control of CD8 T cell trafficking.