Structure and Function of UDP-GalNAc:polypeptide alpha-GalNAc transferases

National Institute Of Dental & Craniofacial Research

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Abstract

Our lab studies the structure and function of GalNAc-Ts. We published a methods paper in Glycoconjugate J. on mapping O-glycans using solid phase extraction (SPE) enrichment, protease digestion, and Electron-transfer/Higher Energy Collision Dissociation (EThcD) fragmentation. This work utilized O- protease to specifically cleave O-glycosites and studied the influence of negatively charged amino acids and sialic acids on O-glycosite localization. In collaboration with Drs. Kelly Ten Hagen, Nadine Samara, and Darryl Zeldin, we have submitted a manuscript on the O-glycoylation of the SARS CoV-2 spike protein. We demonstrated that O-glycosylation near the furin cleavage site is mediated by specific members of the GalNAc-T enzyme family and decreases furin cleavage. This O-glycosylation is dependent on the novel proline at position 681 (P681) and mutations at this site in the highly transmissible B.1.1.7 variant abrogate O-glycosylation and increase furin cleavage. These results provide mechanistic insight into the role of the P681 mutation found in the highly transmissible B.1.1.7 variant. A pre-print of this work was deposited into bioRxiv. In collaboration with Jan Albert Kuivenhoven and colleagues at the University Medical Center of Groningen, in The Netherlands we have explored the role of GalNAc-T2 in whole-body energy homeostasis. Studies in Galnt2-/- mice reveal decreased adiposity, alterations in insulin signaling, and a shift in energy substrate utilization during the day. These findings suggest that the insulin receptor is a novel GalNAc-T2 substrate and may be responsible for local rather than systemic effects. Taken together, our findings identify a novel role for GALNT2 in energy homeostasis.