'Immunosequencing' of heparan sulfate from human cell lines and rat kidney: the (GlcNS6S-IdoA2S)₃ motif, recognized by antibody NS4F5, is located towards the non-reducing end

Immunogenic Sulfated l-Idose Homo Oligosaccharides Elicit Neutralizing Antibody against Native Heparan Sulfate with Biomarker and Therapeutic Possibilities

Heparan sulfate (HS) is a non-immunogenic antigen, and developing antibodies against specific sulfated patterns in HS poses significant challenges. Herein, we employed an innovative immunization strategy that exploits the molecular mimicry of HS to generate antibodies against HS sequences. Mice were immunized with synthetic sulfated oligo-l-idose (ID49) that mimics optimum 67% of the conserved structure of HS ligands. This immunization of ID49@CRM197 with alum and Freund's adjuvant resulted in the production of robust IgG antibody responses targeting ID49 and cross-reactivity with the N-sulfated HS ligands compared to N-unsubstituted and N-acetate domain synthetic HS ligands. Such a pharmacological agent exhibited distinct staining of tissue sections and cell lines and induced complement-dependent cell cytotoxicity against SK-BR-3 cancer cells. Moreover, these antibodies inhibited heparin-mediated anticoagulation activity similar to that of protamine. These findings highlight the biomarker and possible therapeutic capability of the antibodies.

Drugs affecting glycosaminoglycan metabolism

Glycosaminoglycans (GAGs) are charged polysaccharides ubiquitously present at the cell surface and in the extracellular matrix. GAGs are crucial for cellular homeostasis, and their metabolism is altered during pathological processes. However, little consideration has been given to the regulation of the GAG milieu through pharmacological interventions. In this review, we provide a classification of small molecules affecting GAG metabolism based on their mechanism of action. Furthermore, we present evidence to show that clinically approved drugs affect GAG metabolism and that this could contribute to their therapeutic benefit.

A common sugar-nucleotide-mediated mechanism of inhibition of (glycosamino)glycan biosynthesis, as evidenced by 6F-GalNAc (Ac3)

Glycosaminoglycan (GAG) polysaccharides have been implicated in a variety of cellular processes, and alterations in their amount and structure have been associated with diseases such as cancer. In this study, we probed 11 sugar analogs for their capacity to interfere with GAG biosynthesis. One analog, with a modification not directly involved in the glycosidic bond formation, 6F-N-acetyl-d-galactosamine (GalNAc) (Ac3), was selected for further study on its metabolic and biologic effect. Treatment of human ovarian carcinoma cells with 50 μM 6F-GalNAc (Ac3) inhibited biosynthesis of GAGs (chondroitin/dermatan sulfate by ∼50-60%, heparan sulfate by ∼35%), N-acetyl-d-glucosamine (GlcNAc)/GalNAc containing glycans recognized by the lectins Datura stramonium and peanut agglutinin (by ∼74 and ∼43%, respectively), and O-GlcNAc protein modification. With respect to function, 6F-GalNAc (Ac3) treatment inhibited growth factor signaling and reduced in vivo angiogenesis by ∼33%. Although the analog was readily transformed in cells into the uridine 5'-diphosphate (UDP)-activated form, it was not incorporated into GAGs. Rather, it strongly reduced cellular UDP-GalNAc and UDP-GlcNAc pools. Together with data from the literature, these findings indicate that nucleotide sugar depletion without incorporation is a common mechanism of sugar analogs for inhibiting GAG/glycan biosynthesis.