Cystatin-SN (CST1)

Cystatin-SN (CST1) is a type 2 cystatin, a member of the cystatin superfamily of cysteine proteinase inhibitors, encoded by the CST1 gene on human chromosome 20. CST1 is secreted in various bodily fluids including saliva, tears, urine, and seminal fluid, and primarily inhibits cysteine proteases such as papain and dipeptidyl peptidase I, contributing to the regulation of extracellular proteolysis. CST1 forms tight complexes with its target enzymes to block inappropriate tissue degradation and may play a protective role in antimicrobial defense. Elevated CST1 expression is associated with increased proliferation and metastasis in colorectal and gastric cancers, likely due to its regulatory interaction with other protease inhibitors such as CST3 (cystatin C), which shifts the balance of protease activity in favor of tumor invasion.

Other names

Cystatin-SNCST1Cystain-SA-ICystatin-1Salivary cystatin-SA-1Cystatin SA-ICysteine proteinase inhibitor, type 2 familyCystatin SNCystein proteinase inhibitor, type 2 family

Protease inhibition: drugs could modulate CST1's interaction with cysteine proteases or its regulatory effect on protease activity (e.g., cathepsins). Interference with CST1/CST3/CTSB interactions to inhibit tumor cell invasion.