Heparan Sulfate Mimicry

Abstract

Cell-associated heparan sulfate (HS) is endowed with the remarkable ability to bind numerous proteins. As such, it represents a unique system that integrates signaling from circulating ligands with cellular receptors. This polysaccharide is extraordinary complex, and examples that define the structure-function relationship of HS are limited. In particular, it remains difficult to understand the structures by which HS interact with proteins. Among them, interferon-␥ (IFN␥), a dimeric cytokine, binds to a complex oligosaccharide motif encompassing a N-acetylated glucosamine-rich domain and two highly sulfated sequences, each of which binds to one IFN␥ monomer. Based on this template, we have synthesized a set of glycoconjugate mimetics and evaluated their ability to interact with IFN␥. One of these molecules, composed of two authentic N-sulfated octasaccharides linked to each other through a 50-Å-long spacer termed 2O 10 , displays high affinity for the cytokine and inhibits IFN␥-HS binding with an IC 50 of 35-40 nM. Interestingly, this molecule also inhibits the binding of IFN␥ to its cellular receptor. Thus, in addition to its ability to delocalize the cytokine from cell surface-associated HS, this compound has direct anti-IFN␥ activity. Altogether, our results represent the first synthetic HS-like molecule that targets a cytokine, strongly validating the HS structural determinants for IFN␥ recognition, providing a new strategy to inhibit IFN␥ in a number of diseases in which the cytokine has been identified as a target, and reinforcing the view that it is possible to create "tailor-made" sequences based on the HS template to isolate therapeutic activities. Current research increasingly implicates heparan sulfate (HS),2 a highly sulfated glycosaminoglycan present in the extracellular matrix and at the cell surface, in a plethora of phenomena that include cell proliferation, cell adhesion, matrix assembly, chemoattraction, inflammation, immune response, development, lipid metabolism, angiogenesis, wound healing, and viral attachment (1, 2). Mechanistically, this extensive functional repertoire often relies on the ability of HS to recognize diverse proteins, the conformation, stability, local concentration, or biological activities of which are modified by the interaction (3-7).Consistent with its wide protein binding activity, HS is structurally complex. It is composed of strongly anionic domains enriched in N-sulfated glucosamines and iduronic acids, typically 3-8 disaccharides long (referred to as NS or heparin-like domains), that bear a variable number of O-sulfate moieties and are hypervariable in sequence. These domains are separated by relatively regular regions encompassing a larger area that contain predominantly N-acetylated glucosamine and glucuronic acid domains (NA domains) and mixed NA/NS regions that make the transition between NA and NS domains (8). It has been thought that specific information for protein recognition resided within the NS domains in HS and, indeed, a large number of "heparin-bindi...

Syndecan-1 Is an in Vivo Suppressor of Gram-positive Toxic Shock

“…Further, IFN␥ is a potent physiological inducer of the CXC chemokines, MIG (monokine induced by IFN␥, CXCL9), IP-10 (IFN␥-induced protein, CXCL10), and I-TAC (interferon-inducible T cell alpha chemoattractant, CXCL11), which are the primary chemoattractants of activated T cells (59 -61). Third, HS and heparin bind to and inhibit IFN␥ (8,9,62). Altogether, these observations suggest that the HS moiety of syndecan-1 ectodomain attenuates SEB shock by inhibiting the capacity of IFN␥ to amplify TNF␣ and IL-6 production, and facilitate the recruitment of SEB-activated T cells by inducing the expression of T cell chemotactic CXC chemokines.…”

“…Thus, it is important to understand how the expression and activity of superantigen-induced cytokines are regulated in vivo. Heparan sulfate (HS) and its highly sulfated pharmaceutical analogue, heparin, bind to and regulate many molecules that have been implicated in Gram-positive toxic shock, such as IL-2 (6, 7), IFN␥ (8,9), TNF␣ (10), and IL-6 (11). Further, several studies have shown that heparin attenuates inflammation in several major inflammatory diseases, such as asthma (12), inflammatory bowel disease (13), and sepsis (14).…”

Streptococcus pneumoniae Sheds Syndecan-1 Ectodomains through ZmpC, a Metalloproteinase Virulence Factor

“…How syndecan-1 shedding promotes bacterial pathogenesis is not completely understood, but syndecan-1 ectodomains bind to and inhibit various host defense factors, such as antimicrobial peptides, in a heparan sulfate (HS)-dependent manner (22). Moreover, because soluble HS can inhibit several cytokines (23)(24)(25)(26), syndecan-1 ectodomains might similarly inhibit cytokines through their HS moiety. These observations suggest that activation of syndecan-1 shedding is a broadly used pathogenic strategy to enhance microbial virulence.…”

Interferon and heparan sulphate

“…Finally, we also reported that 2O 10 inhibited the binding of IFNγ to the IFNγ Rα chain, and consequently the biological activity of the cytokine [27]. This important observation thus provides a new strategy to inhibit IFNγ in a number of diseases, in which the cytokine has been identified as an attractive target.…”

“…This was developed by David Bonnaffé at the Orsay University in Paris [26], and a set of compounds called 2X n was obtained (in which 2 means that two oligosaccharides X are linked through a spacer having n ethylene glycol repeats). This strategy was successful, and among the different 2X n molecules synthesized, 2O 10 (O stands for octasaccharide) very efficiently interacted with the cytokine, inhibited the IFNγ -heparin interaction with an IC 50 of 35-40 nM and, thus, appeared as a good mimic of the IFNγ -binding domain [27].…”