Large-scale glycoproteome analysis reveals inverted distribution of Neu5Gc and Neu5Ac in mouse liver tissues and cell lines.

Two common forms of sialic acid, Neu5Ac and Neu5Gc, are crucial components of mammalian glycosylation, with distinct roles in various biological processes. Despite their prevalence in mice, differences in their distribution between widely-used model systems, mouse liver tissues and cell lines, are rarely considered. In this study, we demonstrated a long-neglected phenomenon of an inversion of Neu5Gc and Neu5Ac levels between the two sample types by conducting N-glycoproteome analysis at intact glycopeptide level and independent validation assays. Additionally, we show that during the immortalization process of mouse primary liver cells, alterations in the CMAH gene drive a shift in Neu5Gc and Neu5Ac levels. These findings highlight the distinct expression patterns of the two sialic acid forms in both in vivo and in vitro models, cautioning researchers to consider the sample types when studying sialic acid biology.