Rapid probing of sialylated glycoproteins in vitro and in vivo via metabolic oligosaccharide engineering of a minimal cyclopropene reporter

Abstract

ManNAc analogues are important chemical tools for probing sialylation dynamically via metabolic oligosaccharide engineering (MOE). The size of N-acyl and the nature of the chemical handle are two determinants of metabolic incorporation efficiency. We demonstrated a minimal, stable, bioorthogonal, and reactive N-Cp (N-(cycloprop-2-ene-1-ylcarbonyl)) group and the imaging of sialylated glycans using Ac₄ManNCp in vitro and in vivo. The results revealed that the Cp group can efficiently be incorporated into the cellular sialic acid and detected rapidly by the reaction with FITC-Tz in different cells. The metabolic incorporation efficiency of non-cytotoxic Ac₄ManNCp is not only superior to Ac₄ManNMCp, but also superior to the widely-used Ac₄ManNAz in some cell lines. Moreover, when Ac₄ManNCp was administered to mice, a rapid and intense labelling of splenocytes as well as glycoproteins of sera and organs was observed. This is the first reported metabolic labelling of cyclopropene-modified sugars in vivo. Therefore, Ac₄ManNCp is a powerful probe for efficient and rapid MOE and it may find wide applications in the labelling of glycans.