Re-expression of glucuronyl C5-epimerase in the mutant MEF cells increases heparan sulfate epimerization but has no influence on the Golgi localization and enzymatic activity of 2-O-sulfotransferase

Heparan sulfate (HS) is a linear and complex polysaccharide that modulates the biological activities through protein recognition and interaction. Evidence indicates that protein-binding properties of HS are largely dependent on distinctive sulfation and epimerization patterns that are modified by a series of Golgi-localized enzymes. In particular, the glucuronyl C5-epimerase (Hsepi) converts D-glucuronic acid (GlcA) residues to L-iduronic acid (IdoA) and 2-O-sulfotransferase (2OST) catalyzes sulfation at C2 position of IdoA and rarely GlcA residues. Mice lacking both Hsepi and 2OST display multiple development defects, indicating the importance of IdoA in HS. Here, to gain greater insights of HS structure-function relationships, as well as a better understanding of the regulatory mechanisms of Hsepi and 2OST, the fine structure and cellular signaling functions of HS were investigated after restoration of Hsepi in the mutant mouse embryonic fibroblast (MEF) cells. Introduction of Hsepi into the Hsepi mutant MEF cells led to robustly increased proportion of IdoA residues, which rescued the cell signaling in response to fibroblast growth factor 2. However, we found that Hsepi knockout had no influence on either cellular transport or enzymatic activity of 2OST in the MEF cells, which is not in accord with the findings suggesting that the enzymatic activity and cellular transport of 2OST and Hsepi might be differently regulated.

Automated summary

The translation explores the role of Heparan sulfate (HS) in protein recognition and interaction, highlighting the importance of specific sulfation and epimerization patterns modulated by Golgi-localized enzymes. The study investigates the effects of restoring Hsepi in mutant MEF cells, showing increased IdoA residues and rescued cell signaling, although Hsepi knockout did not influence cellular transport or enzymatic activity of 2OST. These findings suggest potential differences in regulatory mechanisms for 2OST and Hsepi.