Glypicans are a family of heparan sulfate proteoglycans that are attached to the outer plasma membrane leaflet of the producing cell by a glycosylphosphatidylinositol anchor. Glypicans are involved in the regulation of many signalling pathways, including those that regulate the activities of Wnts, Hedgehog (Hh), Fibroblast Growth Factors (FGFs) and Bone Morphogenetic Proteins (BMPs), among others. In the Hh signalling pathway, glypicans have been shown to be essential for ligand transport and the formation of Hh gradients over long distances, for the maintenance of Hh levels in the extracellular matrix and for its unimpaired reception in distant recipient cells. Recently, two mechanistic models have been proposed to explain how Hh can form the signalling gradient and how glypicans may contribute to it. In this review, we describe the structure, biochemistry and metabolism of glypicans and their interactions with different components of the Hh signalling pathway that are important for the release, transport and reception of Hh.

The glycosaminoglycan, heparan sulphate (HS), orchestrates many developmental processes. Yet its biological role has not yet fully been elucidated. Small molecule chemical inhibitors can be used to perturb HS function and these compounds pro-vide cheap alternatives to genetic manipulation methods. However, existing chemical inhibition methods for HS also interfere with chondroitin sulphate (CS), complicating data interpretation of HS function. Herein, a simple method for the selective inhibition of HS biosynthesis is described. Using endogenous metabolic sugar pathways, Ac4GalNAz produces UDP-GlcNAz, which can target HS synthesis. Cell treatment with Ac4GalNAz resulted in defective chain elongation of the polymer and decreased HS expression. Conversely, no adverse effect on CS production was observed. The inhibition was transient and dose-dependent, affording rescue of HS expression after removal of the unnatural azido sugar. The utility of inhibition is demonstrated in cell culture and in whole or-ganisms, demonstrating that this small molecule can be used as a tool for HS inhibition in biological systems.

Alteration in heparan sulfate (HS) biosynthesis has been described to impact a range of pivotal processes involved in cancer progression. HS 3-O-sulfotransferase 3B1 (HS3ST3B1) catalyzes the reaction of 3-O-sulfation within HS chains. Over the past few years, a growing number of studies has reported a tumor-promoting effect of this HS-modifying enzyme in various cancers. Consistent with these studies, we previously reported that HS3ST3B1 overexpression increased survival and resistance to apoptosis in MDA-MB-231 breast cancer (BrCa) cells. In the present study, we further investigated the biological and clinical significance of HS3ST3B1 expression in BrCa. Interrogation of public databases revealed that high expression levels of HS3STB1 are associated with invasive and mesenchymal-like phenotype in BrCa cells and predict poor clinical outcome in BrCA patients with chemotherapy. In vitro, HS3ST3B1 overexpression increased the invasive properties of MDA-MB-231 cells and enhanced chemo-resistance to conventional anticancer drugs. Mechanistically, we found that the advantage given by HS3ST3B1 was linked to the expression and activation of PDGF-Rβ. Silencing the expression of this receptor reversed the effects driven by HS3ST3B1 overexpression. Altogether, our results suggest that HS3ST3B1 may play an important role in the progression of aggressive BrCa and offer a potentially druggable target for therapeutic application.

SARS-CoV-2 attachment and entry inside mammalian cells is mainly mediated by human angiotensin-converting enzyme 2 (ACE2) and its interaction with spike protein. However, it is well known that spike protein also interacts with other molecules like glycosaminoglycans (GAG), e.g., heparan sulfate (HS) or Enoxaparin (EX), which are linear, anionically charged polysaccharides known for their biological activities. The mode of action of these two polysaccharides is to bind spike protein to block the interaction with ACE2 receptors. This study aimed to assess a model capable of confirming the activity of these GAGs in both the wild-type strain of SARS-CoV-2 and its variants, such as the highly variable BA.2.86. This was achieved by combining in silico modeling with in vitro determination using BacMam technology. The results showed the antiviral activity of HS and EX both in vitro and through the in-silico analysis, reconciling conflicting findings from recent studies on the cellular entry of SARS-CoV-2. In conclusion, it is possible to highlight the ability of these molecules to circumvent the high variability of SARS-CoV-2, providing valuable insights into intervention strategies targeting cell entry mechanisms and establishing a safe in vitro model.

Alzheimer’s Disease (AD) is a debilitating neurodegenerative disease characterized by the accumulation of extracellular amyloid-β peptides (Aβ) within the cerebral parenchyma and vasculature, the latter termed cerebral amyloid angiopathy (CAA). This study utilized confocal imaging to investigate heparan sulfate (HS) within the cerebrovasculature and its potential associations with CAA, gender, and ApoE4 genotype. Our investigation revealed elevated levels of HS in the cerebrovasculature of AD patients with severe CAA. Additionally, these patients exhibited higher colocalization of HS with Aβ in the cerebrovasculature, including both endothelial and vascular smooth muscle cell compartments. Intriguingly, a reversal in the polarized expression of HS within the cerebral vasculature was detected in AD patients with severe CAA, suggesting a potential role in CAA development. Furthermore, male patients exhibited lower levels of both parenchymal and cerebrovascular HS. Additionally, ApoE4 carriers displayed heightened cerebrovascular Aβ expression and a tendency of elevated cerebrovascular HS levels in AD patients with severe CAA. Overall, these findings shed light on the intricate interplay between HS, Aβ, ApoE, and vascular pathology in AD, underscoring the potential roles of cerebrovascular HS in CAA development and AD pathology. Further exploring the underlying mechanisms may present novel therapeutic avenues for AD treatment.

The extremely controversial conclusions about the function of human interferon-gamma (hIFNγ) C-terminus as well as the lack of a consistent model explaining its role in the receptor binding prompted us to scrutinize the interaction of hIFNγ with its extracellular receptor hIFNGR1 in different scenarios by means of molecular dynamics simulations. We find that the two molecules alone fail to form a stable complex but the presence of heparan-sulfate-like oligosaccharides largely facilitates the process by both demobilizing the highly flexible C-termini of the cytokine and assisting in the proper positioning of its globule between the receptor subunits. An antiproliferative-activity essay on cells depleted from surface sulfation confirms qualitatively the simulation-based multistage complex-formation model. Our results reveal the key role of HS and its proteoglycans in all processes involving hIFNγ signalling.