Cystatin C (CST3)

Cystatin C is a small, non-glycosylated protein of 120 amino acids (~13 kDa) encoded by the CST3 gene, widely expressed and secreted by all nucleated human cells[1][5][6]. It is the principal extracellular inhibitor of cysteine proteases, especially cathepsins, helping regulate proteolytic processes in tissues and bodily fluids[1][5][3]. Cystatin C provides cell and tissue protection by controlling protease activity during inflammation, tissue remodeling, and apoptotic events[2][1][5]. Highest physiological concentrations are found in cerebrospinal fluid, semen, breastmilk, tears, and saliva[1][6]. Its serum levels are used clinically to assess kidney function, being less influenced by muscle mass than creatinine, and altered levels may indicate risk for cardiovascular and neurodegenerative disease. Mutations or aggregation of Cystatin C are associated with rare hereditary amyloid disorders and may play a role in the pathogenesis of Alzheimer's disease and cerebral vessel fragility[3][2][4][6].

Other names

Cystatin-3Gamma-traceNeuroendocrine basic polypeptidePost-gamma-globulinADLDWAARMD11HEL-S-2cystatin-CbA218C14.4epididymis secretory protein Li 2CST3

Endogenous inhibitor: Prevents proteolysis by binding and inhibiting cysteine proteases (cathepsins)[1][3][6].