Research Projects

Mammalian cell surface proteins are glycoproteins, carrying both N-linked and O-linked glycans attached to Asn-X-Ser/Thr and Ser/Thr residues. CD antigens, such as CD43, CD162/PSGL-1, CD93, CD45, and CD148, are heavily glycosylated with 50-80% of molecular mass arising from glycans. CD43 is estimated to carry 80-90 O-glycans on its extracellular domain. CD43 knockout in mice resulted in elevated T-cell activation and induction of homotypic clumping, suggesting it is critical for resolution of inflammatory responses and a negative regulator of T-cell activation. CD43 is specifically excluded from immune synapse between antigen-presenting cells (APC) and T-cells. The glycosylation of CD43 is cell-type dependent, with resting T-cells expressing 115 kDa glycoforms carrying tetrasaccharides and activated T-cells expressing 130 kDa glycoforms carrying hexasaccharide moieties. CD43 glycans act as ligands for Siglec-7, acting as an immune check-point for immune suppression. The extracellular domain (CD43ex) contains 93 Ser/Thr, which are potential O-glycan sites. Recent studies have shown efficient inhibition of O-glycosylation by the N-acetyl-D-galactosamine analogue, Ac5GalNTGc, both in vivo and in vitro. This proposal aims to apply state-of-the-art mass spectrometry and glycoproteomics methodologies to enumerate site occupancy and micro-/macro-heterogeneity of glycan structures on CD43, their inhibition, and modulation of immunological processes.