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

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.

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Objective Angiogenesis requires tightly coordinated cross-talk between endothelial cells and stromal cells such as fibroblasts and smooth muscle cells. The specific molecular mechanisms moderating this process are still poorly understood. Method and Results Stromal cell-derived factors are essential for endothelial cell sprouting and lumen formation. We therefore compared the abilities of two primary fibroblast isolates and a primary smooth muscle cell isolate to promote in vitro angiogenesis and analyzed their secretomes using a combination of nanoLC-MS/MS, qPCR and ELISA. Each isolate exhibited a different level of angiogenic ability. Using quantitative MS, we then compared the secretomes of a fibroblast isolate exhibiting low angiogenic activity, a fibroblast isolate exhibiting high angiogenic activity and human umbilical vein endothelial cells. High angiogenic fibroblast supernatants exhibited an over-abundance of proteins associated with extracellular matrix constituents compared to low angiogenic fibroblasts or endothelial cells. Finally, siRNA technology and purified protein were used to confirm a role for stromal cell-derived hepatocyte growth factor and fibronectin in inducing endothelial cell sprouting. Conclusion Differences in stromal cell ability to induce angiogenesis are due to differences in the secreted proteomes of both extracellular matrix proteins and pro-angiogenic growth factors.