Abstract

9-O-Acetylation of sialic acid is known as a cell type-specific modification of secretory and plasma membrane glycoconjugates of higher vertebrates with important functions in modulating cell-cell recognition. Using a recombinant probe derived from influenza C virus hemagglutinin, we discovered 9-O-acetylated protein in the Golgi complex of various cell lines, most of which did not display 9-O-acetylated sialic acid on the cell surface. All cell lines expressed a sulfated glycoprotein of 50 kDa (sgp50) carrying 9-O-acetylated sialic acids, which was used as a model substrate. Like gp40, the major receptor for influenza C virus of Madin-Darby canine kidney I cells, sgp50 is 9-O-acetylated on O-linked glycans. However, gp40 was not 9-O-acetylated when expressed in Madin-Darby canine kidney II or COS-7 cells. The results demonstrate the existence of two 9-O-acetylation machineries for O-glycosylated proteins with distinct substrate specificities. The widespread occurrence of 9-O-acetylated protein in the Golgi furthermore suggests an additional intracellular role for this modification.

Highlights

  • O-Acetyl transferases for sialic acids have resisted purification or cloning far

  • We discovered that all cell lines tested, including some that were previously shown to be resistant to infection by influenza C virus and considered to lack 9-O-acetyl sialic acid, stained positive intracellularly in the Golgi apparatus

  • Intracellular 9-O-Acetylated Sialic Acid Detected with CHEFcD Fluorescence Microscopy—CHE-FcD/protein ASepharose (CHE)-Fc, the fusion protein of influenza C virus hemagglutinin-esterase with the constant region of human IgG, efficiently binds to 9-O-acetylated sialic acid if the esterase is inactivated by diisopropyl fluorophosphate treatment [20]

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Summary

Introduction

O-Acetyl transferases for sialic acids have resisted purification or cloning far. All cell lines expressed a sulfated glycoprotein of 50 kDa (sgp50) carrying 9-O-acetylated sialic acids, which was used as a model substrate.

Results
Conclusion
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