UC San Diego

Heparanase, an endo-β-glucuronidase, is expressed by mammalian cells and plays essential roles in viral infection. For example, in herpes simplex virus, the virus induces the host to produce heparanase and which facilitates release of viral progeny from the infected cell. SARS-CoV-2 may use a similar mechanism to escape from cells. Heparanase acts upon cell surface heparan sulfate proteoglycans, cleaving the heparan sulfate chains into fragments and releasing any bound proteins or viral particles. Assays for measuring heparanase activity exist, however, the existing assays are not generalizable to tissues or cells, which limits their use for measuring heparanase activity in a variety of biological samples. We developed a sensitive assay using an ELISA-based format in which heparan sulfate-BSA conjugates are used to coat the wells of a 96-well plate. The immobilized heparan sulfate-BSA will bind heparin binding proteins, such as biotinylated FGF2, which can be quantitated by ELISA. Incubation with heparanase cleaves the heparan sulfate chains and reduces FGF2 binding. The assay was optimized with respect to substrate and buffer conditions. Future studies will focus on assaying heparanase in cell and tissue extracts, before and after SARS-CoV-2 infection. The high through-put potential of the assay also would allow screening for heparanase inhibitors.