CST4 (Cystatin S)
A member of the type 2 cystatin gene family encoding a salivary cysteine proteinase inhibitor
Gene Information Card
| Symbol | CST4 |
|---|---|
| Full Name | Cystatin S |
| Gene Type | protein-coding |
| Chromosomal Location | 20p11.21 |
| NCBI Gene ID | 1472 ncbi.nlm.nih.gov/gene/1472 |
| Ensembl ID | ENSG00000101441 |
| UniProt ID | P01036 |
| OMIM ID | 123857 |
| HGNC ID | 2475 |
| Aliases | cystatin SA, cystatin-4, cystatin-S |
Description
CST4 encodes cystatin S, a secreted cysteine proteinase inhibitor belonging to the type 2 cystatin family. It is primarily expressed in salivary glands and plays a role in protecting against proteolytic damage in the oral cavity. The protein inhibits papain-like cysteine proteases and may be involved in antimicrobial defense and tissue remodeling.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Sjögren's syndrome | Altered expression of cystatin S in saliva may contribute to glandular dysfunction | PMID: 25468891 |
| Oral squamous cell carcinoma | Downregulation of CST4 associated with tumor progression | PMID: 23593055 |
| Periodontitis | Reduced cystatin S levels in gingival crevicular fluid correlate with disease severity | PMID: 20663079 |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Salivary gland | 125.3 | High |
| Esophagus | 12.1 | Medium |
| Stomach | 8.5 | Low |
| Kidney | 3.2 | Low |
| Lung | 1.8 | Not detected |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| A-431 (epidermoid carcinoma) | 15.2 | Moderate expression |
| HepG2 (hepatocellular carcinoma) | 2.1 | Low expression |
| K-562 (leukemia) | 0.5 | Not detected |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | missense | <0.01% | Likely loss of start codon |
| c.124G>A (p.Gly42Ser) | missense | <0.01% | Unknown significance |
Mutation functional classification
Loss of Function (LOF)
No confirmed loss-of-function mutations reported in CST4.
Gain of Function (GOF)
No gain-of-function mutations documented.
Dominant Negative (DN)
Not applicable.
View complete mutation data：
Gene Ontology (GO)
| • cysteine-type endopeptidase inhibitor activity (GO:0004869) | • extracellular region (GO:0005576) |
| • secretory granule (GO:0030141) | • defense response to Gram-negative bacterium (GO:0050829) |
Pathways
• Cysteine protease inhibition (Reactome: R-HSA-6809371)
Protein Summary
Cystatin S is a 141-amino-acid secreted protein (UniProt P01036) with a signal peptide (residues 1-20) and a conserved cystatin domain. It forms a tight-binding reversible inhibitor of papain-like cysteine proteases such as cathepsins B, L, and S. The protein is abundant in human saliva and contributes to oral homeostasis by regulating proteolysis and antimicrobial activity.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CST4 Knockout HEK293 Cell Line | EDJ-KQ4379 | Human | 1472 | Details Get a Quote |
| CST4 Knockout HeLa Cell Line | EDJ-KQ53017 | Human | 1472 | Details Get a Quote |
| CST4 Knockout A-549 Cell Line | EDJ-KQ61482 | Human | 1472 | Details Get a Quote |
| CST4 Knockout HCT 116 Cell Line | EDJ-KQ69978 | Human | 1472 | Details Get a Quote |
