Developmental stage-dependent expression of an  2,8-trisialic acid unit on glycoproteins in mouse brain

Abstract

The monoclonal antibody mAb.A2B5 is a marker for the detection of oligodendrocyte progenitor cells that differentiate into type-2 astrocytes and oligodendrocytes. It is also a useful antibody for separating these cells from other lineage populations. The epitope of this antibody is considered to be the gangliosides GT3 and GQ1c. In this study, we sought to define more precisely the structure of the epitope. Accordingly, we chemically synthesized defined oligosialic acid structures linked to phosphatidylethanolamine and bovine serum albumin and used these to determine the antigenic specificity. mAb.A2B5 recognized the Neu5Acalpha2-->8Neu5Acalpha2-->8Neu5Acalpha--> structure on both glycolipids and glycoproteins. We then examined whether the mAb.A2B5 epitope exists on glycoproteins in developing mouse brains. Western blot analyses revealed the expression of four glycoproteins reactive with the mAb.A2B5, and their expression was dependent on the stage of neural development. All the immunoreactivity in these glycoproteins with mAb.A2B5 disappeared after sialidase treatment and were resistant to chloroform/methanol extraction. These epitopes were also detected in brain homogenates from both GD3 synthetase-null and GD3/GD2 synthetase double null mice. These findings show that the alpha2,8-trisialic acid (triSia) unit recognized by mAb.A2B5 resides not only on gangliosides but also on glycoproteins in developing mouse brain. We postulate that the triSia structure on glycoproteins may be involved in oligodendrocyte differentiation, similar to the case with the alpha2,8-triSia structure on gangliosides. Real time polymerase chain reaction analysis of the developmental expression of all known ST8Sia genes, which are responsible for the biosynthesis of alpha2,8-linked Sia residues, showed that ST8Sia III gene expression correlated with expression of the triSia epitope. We suggest that ST8Sia III is the principal sialyltransferase responsible for synthesis of the alpha2,8-triSia units on glycoproteins.

Discovery, Primary, and Crystal Structures and Capacitation-related Properties of a Prostate-derived Heparin-binding Protein WGA16 from Boar Sperm

“…C, real-time PCR for mRNA expression of WGA16. The expression level in each organ was normalized by the expression of actin mRNA as described (27). The relative expression is shown relative to that of testis set to 1.0.…”

Rapid Trimming of Cell Surface Polysialic Acid (PolySia) by Exovesicular Sialidase Triggers Release of Preexisting Surface Neurotrophin

“…Turnover of Cell-surface PolySia Is Rapid and Mediated by an Induced Extracellular Sialidase-PolySia is known to turnover a period of days during postnatal brain development (7,34), and this is presumed to be due to internalization and lysosomal degradation. However, the possibility that polySia might turn over rapidly on the cell surface has not been previously considered.…”

Stem Cell Glycolipids

“…In fact, lysosome-associated membrane protein-1 has been identified as a major SSEA-1 carrier protein in mouse neural stem cells [112]. Furthermore, it has been recently reported that the epitope of A2B5 antigens, c-series gangliosides used as marker carbohydrates of glial precursor cells and brain cancer stem cells, was also carried by 4 glycoproteins in developing mouse brains [113]. There is a possibility that the immunoreactivity of stem cells to antibodies to SSEA-3, SSEA-4, and GD2 are also attributable to glycoproteins or proteoglycans but not to glycolipids.…”