Synthesis of chondroitin sulfate CC and DD tetrasaccharides and interactions with 2H6 and LY111

Quantitative, compositional, and immunohistochemical analyses of chondroitin sulfate, dermatan sulfate, and hyaluronan in internal organs of deer (Cervus nippon centralis and C. n. yesoensis) and cattle (Bos taurus)

Chondroitin sulfate (CS) + dermatan sulfate (DS) and hyaluronan (HA) concentrations and the sulfation patterns of CS-DS in the cartilaginous tissues and alimentary canals of Honshu Sika deer, Hokkaido Sika deer, and cattle were investigated in the present study. CS + DS concentrations were high in cartilaginous tissues, namely, the trachea and scapular cartilage region (5- 12 g*), and low in the alimentary canal (~0.3 g*). HA concentrations were low in cartilaginous tissues and the alimentary canal (~0.2 g*). All tissues mainly contained A-type [HexAGalNAc(4-sulfate)] and C-type [HexAGalNAc(6-sulfate)] CS + DS. The ratios of A-type/C-type CS + DS were 1.2- 3.1 and 0.9- 16.4 in cartilaginous tissues and the alimentary canal, respectively. CS + DS predominantly comprised β-D-GlcA and α-L-IdoA in cartilaginous tissues and the alimentary canal, respectively. The alimentary canal characteristically contained up to 14 % highly sulfated E-type [HexAGalNAc(4,6-disulfate)] and D-type [HexA(2-sulfate)GalNAc(6-sulfate)] CS + DS. The specific distributions of CS and DS were immunohistochemically confirmed using CS + DS-specific antibodies. Although the omasum of cattle is more likely to have higher concentrations of CS + DS and HA, no significant species differences were observed in the concentrations or sulfation patterns of CS + DS among species for Honshu Sika deer, Hokkaido Sika deer, and cattle. (*per 100 g of defatted dry tissue).

Synthesis of biotinylated chondroitin sulfate DA and AD tetrasaccharides composed of hetero-type disaccharide units, and their interactions with the mAb MO-225

Chondroitin sulfate (CS), a linear acidic polysaccharide, exhibits numerous biological activities that are dependent on sulfation patterns. CS oligosaccharides comprise repeating disaccharide units with different (hetero)-type sulfation patterns and are common in nature. We herein report the synthesis of the following biotinylated CS tetrasaccharides: CS-AD [βGalNAc4S(1-4)βGlcA(1-3)βGalNAc6S(1-4)βGlcA2S] and CS-DA [βGalNAc6S(1-4)βGlcA2S(1-3)βGalNAc4S(1-4)βGlcA], in a stereo-controlled manner. We also demonstrated that the CS-d-specific monoclonal antibody MO-225 bound more strongly to CS-DA than to CS-DD or -AD.

Immunochemical Detection and Glycosaminoglycan Disaccharide-Based Characterization of Chondroitin Sulfate Proteoglycans

Chondroitin sulfate proteoglycans (CSPGs) are polyanionic extra/pericellular matrix macromolecules that surround almost all cell types and create microenvironmental niches to support miscellaneous cellular events. In general, the multifunctional properties of CSPGs are attributable to the structural divergence of the CS glycosaminoglycan (GAG) moieties. Because the expression profiles of the GAG chains of CSPGs change with developmental stage, aging, and disease progression, characterization of the GAG chains is essential to understand the functional roles of CSPGs. This chapter describes the basic protocols for GAG moiety-based immunochemical detection of CSPGs in biological samples in conjunction with CS disaccharide composition analysis.

Liquid-Phase and Ultrahigh-Frequency-Acoustofluidics-Based Solid-Phase Synthesis of Biotin-Tagged 6′/3′-Sialyl-N-Acetylglucosamine by Sequential One-Pot Multienzyme System

6′/3′-Sialylated N-acetyllactosamine (6′/3′-SLN) is important for discrimination of the source (human or avian) of influenza virus strains. Biotinylated oligosaccharides have been widely used for analysis and quick detection. The development of efficient strategies to synthesize biotin-tagged 6′/3′-SLN have become necessary. Effective mixing is essential for enzymatic solid-phase oligosaccharide synthesis (SPOS). In the current study, newly developed technology ultrahigh-frequency-acoustofluidics (UHFA), which can provide a powerful source for efficient microfluidic mixing, solid-phase oligosaccharide synthesis and one-pot multienzyme (OPME) system, were used to develop a new strategy for oligosaccharide synthesis. Firstly, biotinylated N-acetylglucosamine was designed and chemically synthesized through traditional approaches. Secondly, biotinylated 6′- and 3′-sialyl-N-acetylglucosamines were prepared in solution through two sequential OPME modules in with a yield of ~95%. Thirdly, 6′-SLN was also prepared through UHFA-based enzymatic solid-phase synthesis on magnetic beads with a yield of 64.4%. The current strategy would be potentially used for synthesis of functional oligosaccharides.

Reconsideration of the Semaphorin-3A Binding Motif Found in Chondroitin Sulfate Using Galnac4s-6st-Knockout Mice

The chondroitin sulfate (CS)-rich dense extracellular matrix surrounding neuron cell bodies and proximal dendrites in a mesh-like structure is called a perineuronal net (PNN). CS chains in PNNs control neuronal plasticity by binding to PNN effectors, semaphorin-3A (Sema3A) and orthodenticle homeobox 2. Sema3A recognizes CS-containing type-E disaccharide units (sulfated at O-4 and O-6 of N-acetylgalactosamine). Type-E disaccharide units are synthesized by N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST). In this study, we demonstrated that Sema3A accumulates in the PNNs surrounding parvalbumin cells, even in mice deficient in GalNAc4S-6ST. In addition, there were no differences in the number and structure of PNNs visualized by Cat316 antibody and Wisteria floribunda lectin, which recognize CS chains, between wild type and GalNAc4S-6ST knockout mice. Therefore, we re-examined the Sema3A binding motif found in CS chains using chemically synthesized CS tetrasaccharides. As a result, we found that non-sulfated GalNAc residues at the non-reducing termini of CS chains are required for the binding of Sema3A.

Chemical Synthesis and Anti-Inflammatory Activity of Bikunin Associated Chondroitin Sulfate 24-mer

Bikunin, a chondroitin sulfate (CS) proteoglycan clinically used to treat acute inflammation and sepsis, contains a CS chain with more than 20 monosaccharide units. To understand the function of the CS chain of bikunin, synthesis of long CS chains is needed. After exploring multiple glycosylation approaches and protective group chemistry, we report herein the successful generation of the longest CS chain to date (24-mer) in an excellent overall yield on a multi-mg scale. The anti-inflammatory activities of both bikunin and the synthetic 24-mer were determined, and the results demonstrate that both the glycan and the core protein are important for anti-inflammatory activities of bikunin by reducing macrophage production of proinflammatory cytokines.

Spatiotemporal distribution of chondroitin sulfate proteoglycans after optic nerve injury in rodents

The accumulation of chondroitin sulfate proteoglycans (CSPGs) in the glial scar following acute damage to the central nervous system (CNS) limits the regeneration of injured axons. Given the rich diversity of CSPG core proteins and patterns of GAG sulfation, identifying the composition of these CSPGs is essential for understanding their roles in injury and repair. Differential expression of core proteins and sulfation patterns have been characterized in the brain and spinal cord of mice and rats, but a comprehensive study of these changes following optic nerve injury has not yet been performed. Here, we show that the composition of CSPGs in the optic nerve and retina following optic nerve crush (ONC) in mice and rats exhibits an increase in aggrecan, brevican, phosphacan, neurocan and versican, similar to changes following spinal cord injury. We also observe an increase in inhibitory 4-sulfated (4S) GAG chains, which suggests that the persistence of CSPGs in the glial scar opposes the growth of CNS axons, thereby contributing to the failure of regeneration and recovery of function.

Chondroitin sulfate-D promotes neurite outgrowth by acting as an extracellular ligand for neuronal integrin αVβ3

BACKGROUND

Chondroitin sulfate (CS) chains are prominent extra/pericellular matrix components in the central nervous system (CNS) and can exert positive or negative regulatory effects on neurite outgrowth, depending on the CS structure and the amount. Despite the remarkable abilities of highly sulfated forms of CS chains to enhance neurite outgrowth, the neuronal recognition systems for such promotional CS chains, including CS-D polysaccharide, remain to be fully elucidated.

METHODS

We explored the molecular basis of the CS-D-mediated neurite extension using primary hippocampal neurons cultured on substrate precoated with CS-D polysaccharides, and evaluated functional involvement of a distinct integrin heterodimer as a novel neuronal CS receptor for CS-D.

RESULTS

We identified an extracellular matrix receptor, integrin αVβ3, as a functional receptor for CS-D. CS-D, but not CS-C (a precursor form of CS-D) showed significant binding affinity toward recombinant integrin αVβ3 heterodimer and activated intracellular signaling(s) involving focal adhesion kinase (FAK) and Src/Fyn kinase. Functional blockade of the respective players for integrin signaling abrogated the promotional effects of CS-D. We also found the existence of CS-D-induced integrin activation system in neuronal stem/progenitor cell population.

CONCLUSIONS

The neuronal cell surface integrin αVβ3 can function as a CS receptor for a highly sulfated CS subtype, CS-D.

GENERAL SIGNIFICANCE

Our findings are the first to demonstrate that CS-dependent neurite outgrowth promotion is exerted via direct activation of specific integrin heterodimers on neuronal cell surfaces, providing new insights into understanding the CS-sensing machineries that regulate CNS development and regeneration.

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

Here, we present an exploratory study on the fluorous-assisted synthesis of chondroitin sulfate (CS) oligosaccharides. Following this approach, a CS tetrasaccharide was prepared. However, in contrast to our previous results, a significant loss of β-selectivity was observed in [2 + 2] glycosylations involving N-trifluoroacetyl-protected D-galactosamine donors and D-glucuronic acid (GlcA) acceptors. These results, together with those obtained from experiments employing model monosaccharide building blocks, highlight the impact of the glycosyl acceptor structure on the stereoselectivity of glycosylation reactions. Our study provides useful data about the substitution pattern of GlcA units for the efficient synthesis of CS oligomers.

Identification of a critical sulfation in chondroitin that inhibits axonal regeneration

The failure of mammalian CNS neurons to regenerate their axons derives from a combination of intrinsic deficits and extrinsic factors. Following injury, chondroitin sulfate proteoglycans (CSPGs) within the glial scar inhibit axonal regeneration, an action mediated by the sulfated glycosaminoglycan (GAG) chains of CSPGs, especially those with 4-sulfated (4S) sugars. Arylsulfatase B (ARSB) selectively cleaves 4S groups from the non-reducing ends of GAG chains without disrupting other, growth-permissive motifs. We demonstrate that ARSB is effective in reducing the inhibitory actions of CSPGs both in in vitro models of the glial scar and after optic nerve crush (ONC) in adult mice. ARSB is clinically approved for replacement therapy in patients with mucopolysaccharidosis VI and therefore represents an attractive candidate for translation to the human CNS.