Heparin and heparan sulfate (HS/HSPG)

Heparin and heparan sulfate are highly sulfated linear polysaccharides belonging to the glycosaminoglycan (GAG) family, playing pivotal roles in human physiology and pathology [1]. Heparan sulfate (HS) is ubiquitously expressed on cell surfaces and within the extracellular matrix as part of heparan sulfate proteoglycans (HSPGs), where it serves as a critical regulator of cell signaling, adhesion, and endocytosis by interacting with a wide array of proteins, including growth factors, chemokines, and morphogens [2]. Heparin, a more densely sulfated structural analog primarily synthesized by mast cells, is one of the most widely used clinical anticoagulants [3]. It functions by binding to and activating antithrombin III, which subsequently neutralizes key coagulation enzymes like thrombin and Factor Xa to prevent clot formation [4]. Beyond their role in blood coagulation, these molecules are involved in viral entry (e.g., SARS-CoV-2), inflammation, and cancer metastasis, making them versatile targets for drug development [5, 6]. Their structural complexity and high negative charge density are central to their ability to interact with the "heparin interactome," a network of hundreds of proteins that govern diverse biological functions [1, 3].

Other names

Heparan sulfateHeparinHeparan sulfate proteoglycanHSPGHeparinic acidUnfractionated heparin

Heparin and heparan sulfate function as polyanionic scaffolds that facilitate or inhibit protein-protein interactions. In anticoagulation, heparin binds to antithrombin III (ATIII) via a specific pentasaccharide sequence, inducing a conformational change that increases ATIII's inhibitory activity against thrombin (Factor IIa) and Factor Xa by approximately 1,000-fold [4]. Heparan sulfate acts as a co-receptor for various growth factors, such as Fibroblast Growth Factor (FGF), by stabilizing the ligand-receptor signaling complex on the cell surface [2]. Therapeutic strategies include using heparin mimetics to compete for binding sites, neutralizing the molecules with cationic agents like protamine sulfate, or utilizing low-molecular-weight derivatives to achieve targeted anticoagulant effects [3, 6].