Heparan sulfate proteoglycan (specifically, for hepatocyte surface forms, the most important are Syndecan-1 and Glypican-3) (HSPG (no unique abbreviation for all hepatocyte surface forms; examples include SDC1 for Syndecan-1, GPC3 for Glypican-3))

Heparan sulfate proteoglycans (HSPGs) are complex macromolecules consisting of a core protein with covalently attached heparan sulfate glycosaminoglycan chains, present on the cell surface of hepatocytes and all animal cells[1][5][7]. Major hepatocyte HSPGs include Syndecan-1 and Glypican-3. HSPGs act as cell surface co-receptors for a diverse range of ligands, including growth factors (FGF, Wnt, Hedgehog, TGF-β), extracellular matrix proteins, and pathogens (viruses such as hepatitis and SARS-CoV-2)[1][3][4][10]. They regulate critical processes such as cell proliferation, differentiation, adhesion, and tissue organization[3][4][7]. In the liver, HSPGs also function as receptors for lipoproteins and play a role in lipid metabolism and clearance. HSPGs are increasingly studied as therapeutic targets in cancer (especially hepatocellular carcinoma), viral infection, and fibrotic liver diseases due to their roles in cellular signaling and disease pathogenesis[4][10]. Select forms, notably Glypican-3, serve as diagnostic biomarkers and are targets for experimental immunotherapies in HCC. HSPGs' structural diversity and wide tissue distribution pose challenges for drug development, as they are essential for normal physiology and their inhibition could affect multiple pathways[4][5][7][10].

Other names

Heparan sulfate proteoglycancell surface HSPGsyndecan (e.g., Syndecan-1)glypican (e.g., Glypican-3)HSPG

Inhibit ligand binding (blockade of growth factor or viral entry); Promote competitive displacement of ligands (e.g., exogenous heparin); Modulate receptor-mediated endocytosis or signaling (as co-receptors)