Highlights d SARS-CoV-2 spike protein interacts with heparan sulfate and ACE2 through the RBD d Heparan sulfate promotes Spike-ACE2 interaction d SARS-CoV-2 infection is co-dependent on heparan sulfate and ACE2 d Heparin and non-anticoagulant derivatives block SARS-CoV-2 binding and infection

Malignancy is associated with altered expression of glycans and glycoproteins that contribute to the cellular glycocalyx. We constructed a glycoprotein expression signature, which revealed that metastatic tumours upregulate expression of bulky glycoproteins. A computational model predicted that these glycoproteins would influence transmembrane receptor spatial organization and function. We tested this prediction by investigating whether bulky glycoproteins in the glycocalyx promote a tumour phenotype in human cells by increasing integrin adhesion and signalling. Our data revealed that a bulky glycocalyx facilitates integrin clustering by funnelling active integrins into adhesions and altering integrin state by applying tension to matrix-bound integrins, independent of actomyosin contractility. Expression of large tumour-associated glycoproteins in non-transformed mammary cells promoted focal adhesion assembly and facilitated integrin-dependent growth factor signalling to support cell growth and survival. Clinical studies revealed that large glycoproteins are abundantly expressed on circulating tumour cells from patients with advanced disease. Thus, a bulky glycocalyx is a feature of tumour cells that could foster metastasis by mechanically enhancing cell-surface receptor function.

We show that SARS-CoV-2 spike protein interacts with cell surface heparan sulfate and angiotensin converting enzyme 2 (ACE2) through its Receptor Binding Domain. Docking studies suggest a putative heparin/heparan sulfate-binding site adjacent to the domain that binds to ACE2. In vitro, binding of ACE2 and heparin to spike protein ectodomains occurs independently and a ternary complex can be generated using heparin as a template. Contrary to studies with purified components, spike protein binding to heparan sulfate and ACE2 on cells occurs codependently. Unfractionated heparin, non-anticoagulant heparin, treatment with heparin lyases, and purified lung heparan sulfate potently block spike protein binding and infection by spike protein-pseudotyped virus and SARS-CoV-2 virus. These findings support a model for SARS-CoV-2 infection in which viral attachment and infection involves formation of a complex between heparan sulfate and ACE2. Manipulation of heparan sulfate or inhibition of viral adhesion by exogenous heparin may represent new therapeutic opportunities.

Growth factor (GF) signaling is a key determinant of stem cell fate. Interactions of GFs with their receptors are often mediated by heparan sulfate proteoglycans (HSPGs). Here, we report a cell surface engineering strategy that exploits the function of HSPGs to promote differentiation in embryonic stem cells (ESCs). We have generated synthetic neoproteoglycans (neoPGs) with affinity for the fibroblast growth factor 2 (FGF2) and introduced them into plasma membranes of ESCs deficient in HS biosynthesis. There, the neoPGs assumed the function of native HSPGs, rescued FGF2-mediated kinase activity, and promoted neural specification. This glycocalyx remodeling strategy is versatile and may be applicable to other types of differentiation.

In this paper, we report on a general synthetic strategy for the assembly of glycopolymers that capitalizes on the intrinsic reactivity of reducing glycans toward hydrazides to form stable cyclic N-glycosides. We developed a poly(acryloyl hydrazide) (PAH) scaffold to which we conjugated a variety of reducing glycans ranging in structure from simple mono- and disaccharides to considerably more complex human milk and blood oligosaccharides. The conjugation proceeds under mild conditions with excellent ligation efficiencies and in a stereoselective manner, providing glycopolymers with pendant glycans accommodated mostly in their cyclic β-glycosidic form. Utilizing a biotin-terminated PAH scaffold prepared via RAFT polymerization, we quickly assembled a panel of glycopolymers that we microarrayed on streptavidin-coated glass. We then demonstrated that in these microarrays, the glycopolymer ligands bind lectins according to the structures of their pendant glycans. Importantly, glycopolymers containing biologically relevant branched oligosaccharides, such as sialyl Lewisx, as well as sulfated glycosaminoglycan-like epitopes can be readily prepared using our methodology.