Cathepsin S (CTSS) Active Protein

The protein encoded by this gene, a member of the peptidase C1 family, is a lysosomal cysteine proteinase that may participate in the degradation of antigenic proteins to peptides for presentation on MHC class II molecules. The encoded protein can function as an elastase over a broad pH range in alveolar macrophages. Alternatively spliced transcript variants encoding distinct isoforms have been found for this gene. [provided by RefSeq, Dec 2010]

CTSS: Thiol protease. Key protease responsible for the removal of the invariant chain from MHC class II molecules. The bond- specificity of this proteinase is in part similar to the specificities of cathepsin L and cathepsin N. Belongs to the peptidase C1 family. 2 isoforms of the human protein are produced by alternative splicing.

Protein type: Protease; EC 3.4.22.27

Chromosomal Location of Human Ortholog: 1q21

Cellular Component: lysosomal lumen; extracellular space; intracellular membrane-bound organelle; membrane; lysosome; extracellular region

Molecular Function: collagen binding; proteoglycan binding; cysteine-type endopeptidase activity; fibronectin binding; laminin binding

Biological Process: adaptive immune response; extracellular matrix organization and biogenesis; antigen processing and presentation of exogenous peptide antigen via MHC class I, TAP-independent; antigen processing and presentation of exogenous peptide antigen via MHC class II; proteolysis; collagen catabolic process; antigen processing and presentation; extracellular matrix disassembly; antigen processing and presentation of peptide antigen via MHC class I; proteolysis involved in cellular protein catabolic process; toll-like receptor signaling pathway; innate immune response; antigen processing and presentation of exogenous peptide antigen via MHC class I; immune response; positive regulation of inflammatory response