Appican, the Proteoglycan Form of the Amyloid Precursor Protein, Contains Chondroitin Sulfate E in the Repeating Disaccharide Region and 4-O-Sulfated Galactose in the Linkage Region

Abstract

Chondroitin sulfate (CS)-D and CS-E, which are characterized by oversulfated disaccharide units, have been shown to regulate neuronal adhesion, cell migration, and neurite outgrowth. CS proteoglycans (CSPGs) consist of a core protein to which one or more CS chains are attached via a serine residue. Although several brain CSPGs, including mouse DSD-1-PG/phosphacan, have been found to contain the oversulfated D disaccharide motif, no brain CSPG has been reported to contain the oversulfated E motif. Here we analyzed the CS chain of appican, the CSPG form of the Alzheimer's amyloid precursor protein. Appican is expressed almost exclusively by astrocytes and has been reported to have brain-and astrocyte-specific functions including stimulation of both neural cell adhesion and neurite outgrowth. The present findings show that the CS chain of appican has a molecular mass of 25-50 kDa. This chain contains a significant fraction (14.3%) of the oversulfated E motif GlcUA␤1-3GalNAc(4,6-O-disulfate). The rest of the chain consists of GlcUA␤1-3GalNAc(4-O-sulfate) (81.2%) and minor fractions of GlcUA␤1-3GalNAc and GlcUA␤1-3GalNAc(6-O-sulfate). We also show that the CS chain of appican contains in its linkage region the 4-O-sulfated Gal structure. Thus, appican is the first example of a specific brain CSPG that contains the E disaccharide unit in its sugar backbone and the 4-O-sulfated Gal residue in its linkage region. The presence of the E unit is consistent with and may explain the neurotrophic activities of appican.

Sulfation patterns of exogenous chondroitin sulfate affect chondrogenic differentiation of ATDC5 cells

“…Protein concentrations of the cell lysates were measured using a BCA protein assay kit. Enzyme activity is reported as units/µg protein (n = 4), *p < 0.01 rat, chicken, and bovine [7,21,22]. In this study, while the main components were 4-O-sulfated disaccharides (> 70 %), a small amount of 4,6-O-disulfated disaccharides (0.5-1.7 %) was produced by ATDC5 cells throughout the 3 weeks of the differentiation course.…”

Prion, Amyloid β-derived Cu(II) Ions, or Free Zn(II) Ions Support S-Nitroso-dependent Autocleavage of Glypican-1 Heparan Sulfate

“…Moreover, a splice variant of the amyloid precursor protein is expressed as a PG called appican (Ref. 42). As discussed previously (28), PG side chains, especially HS, can self-associate and thereby induce clustering.…”

Determination of the Glycosaminoglycan-Protein Linkage Region Oligosaccharide Structures of Proteoglycans from Drosophila melanogaster and Caenorhabditis elegans

“…The resultant precipitate was dissolved in water and subjected to gel filtration chromatography on a PD-10 column with 50 mM pyridine acetate, pH 5.0, as the eluent. The flow-through fraction was collected, dried, and treated with 0.5 M LiOH at 4°C overnight to liberate O-linked saccharides from the core proteins (27,34,35). The reaction was terminated by acidification with glacial acetic acid, and the sample was applied to a column (12 ml) of anion-exchange resin AG 50W-X2 (H ϩ form, Bio-Rad) pre-equilibrated with water.…”

“…Fractions were collected at 3-min intervals, lyophilized, and digested with chondroitinase ABC or a mixture of heparinase and heparitinase (35,36). The digests were derivatized with 2AB, then analyzed by anion-exchange HPLC on an amine-bound PA-03 column (30).…”

“…GAG chains in D. melanogaster have been detected in the tissue extracts, based on the [ 35 S]sulfate incorporation and the sensitivity of the materials to chondroitinase and nitrous acid treatments (16), whereas those in C. elegans have been detected in cross-sections of all organs using an electron-dense dye in conjunction with GAG lyase digestion (17). It was also reported, based on the sensitivity to heparitinase and nitrous acid but not to chondroitinase ABC, that a single syndecan homolog is expressed as an HS proteoglycan in D. melanogaster (18).…”