Brain chondroitin/dermatan sulfate, from cerebral tissue to fine structure: extraction, preparation, and fully automated chip-electrospray mass spectrometric analysis

Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans (GAGs) are covalently linked to proteins, building up a wide range of proteoglycans, with a prevalent expression in the extracellular matrix (ECM). In mammalian tissues, these GAG species are often found as hybrid CS/DS chains. Their structural diversity during chain elongation is produced by variability of sulfation in the repeating disaccharide units. In central nervous system, a large proportion of the ECM is composed of proteoglycans; therefore, CS/DS play a significant role in the functional diversity of neurons, brain development, and some brain diseases. A requirement for collecting consistent data on brain proteoglycan glycosylation is the development of adequate protocols for CS/DS extraction and detailed compositional and structure analysis. This chapter will present a strategy, which combines biochemical tools for brain CS/DS extraction, purification, and fractionation, with a modern analytical platform based on chip-nanoelectrospray multistage mass spectrometry (MS) able to provide information on the essential structural elements such as epimerization, chain length, sulfate content, and sulfation sites.

Secondary storage of dermatan sulfate in Sanfilippo disease

Mucopolysaccharidoses are a group of genetically inherited disorders that result from the defective activity of lysosomal enzymes involved in glycosaminoglycan catabolism, causing their intralysosomal accumulation. Sanfilippo disease describes a subset of mucopolysaccharidoses resulting from defects in heparan sulfate catabolism. Sanfilippo disorders cause severe neuropathology in affected children. The reason for such extensive central nervous system dysfunction is unresolved, but it may be associated with the secondary accumulation of metabolites such as gangliosides. In this article, we describe the accumulation of dermatan sulfate as a novel secondary metabolite in Sanfilippo. Based on chondroitinase ABC digestion, chondroitin/dermatan sulfate levels in fibroblasts from Sanfilippo patients were elevated 2-5-fold above wild-type dermal fibroblasts. Lysosomal turnover of chondroitin/dermatan sulfate in these cell lines was significantly impaired but could be normalized by reducing heparan sulfate storage using enzyme replacement therapy. Examination of chondroitin/dermatan sulfate catabolic enzymes showed that heparan sulfate and heparin can inhibit iduronate 2-sulfatase. Analysis of the chondroitin/dermatan sulfate fraction by chondroitinase ACII digestion showed dermatan sulfate storage, consistent with inhibition of iduronate 2-sulfatase. The discovery of a novel storage metabolite in Sanfilippo patients may have important implications for diagnosis and understanding disease pathology.

Modern developments in mass spectrometry of chondroitin and dermatan sulfate glycosaminoglycans

Chondroitin sulfate (CS) and dermatan sulfate (DS) are special types of glycosaminoglycan (GAG) oligosaccharides able to regulate vital biological functions that depend on precise motifs of their constituent hexose sequences and the extent and location of their sulfation. As a result, the need for better understanding of CS/DS biological role called for the elaboration and application of straightforward strategies for their composition and structure elucidation. Due to its high sensitivity, reproducibility, and the possibility to rapidly generate data on fine CS/DS structure determinants, mass spectrometry (MS) based on either electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI) brought a major progress in the field. Here, modern developments in MS of CS/DS GAGs are gathered in a critical review covering the past 5 years. The first section is dedicated to protocols for CS/DS extraction from parent proteoglycan, digestion, and purification that are among critical prerequisites of a successful MS experiment. The second part highlights several MALDI MS aspects, the requirements, and applications of this ionization method to CS/DS investigation. An ample chapter is devoted to ESI MS strategies, which employ either capillary- or advanced chip-based sample infusion in combination with multistage MS (MS(n)) using either collision-induced (CID) or electron detachment dissociation (EDD). At last, the potential of two versatile separation techniques, capillary electrophoresis (CE), and liquid chromatography (LC) in off- and/or on-line coupling with ESI MS and MS(n), is discussed, alongside an assessment of particular buffer/solvent conditions and instrumental parameters required for CS/DS mixture separation followed by on-line mass analysis of individual components.