Histidine-rich glycoprotein (HRG)

Histidine-rich glycoprotein (HRG) is a multidomain plasma glycoprotein primarily produced in the liver and present at relatively high concentration in vertebrate blood. Structurally, HRG features two N-terminal cystatin-like domains, a central histidine-rich region flanked by proline-rich regions, and a C-terminal domain. Functionally, HRG binds a diverse array of ligands such as heparin, heparan sulfate, plasminogen, fibrinogen, immunoglobulins, complement components, and divalent metal ions (particularly zinc), enabling it to mediate processes including regulation of coagulation and fibrinolysis, modulation of immune responses, control of angiogenesis (with both stimulatory and inhibitory actions depending on context), and host defense against certain pathogens. HRG also facilitates clearance of apoptotic cells and immune complexes and participates in cell adhesion and migration. Clinically, abnormal HRG levels have been associated with thrombophilia and various cancers, and HRG is under investigation as a biomarker for disease prognosis and diagnosis. HRG’s multidomain structure and ligand-binding versatility underlie its multivalent functions in vascular, immune, and hemostatic physiology. Although HRG shares structural motifs with cystatin family proteins, it does not act as a cysteine protease inhibitor[1][2][3][4].

Other names

Histidine–proline-rich glycoproteinHPRGHRGPhistidine-proline-rich glycoproteinthrombophilia due to elevated HRGTHPH11

Not applicable directly to drugs, but biological mechanisms include binding to heparin, plasminogen, fibrinogen, divalent metal ions, and regulation of angiogenesis and coagulation pathways