CTSL

Thiol protease important for the overall degradation of proteins in lysosomes (Probable). Involved in the solubilization of cross-linked TG/thyroglobulin and in the subsequent release of thyroid hormone thyroxine (T4) by limited proteolysis of TG/thyroglobulin in the thyroid follicle lumen (PubMed:12782676). In neuroendocrine chromaffin cells secretory vesicles, catalyzes the prohormone proenkephalin processing to the active enkephalin peptide neurotransmitter (PubMed:12869695). In thymus, regulates CD4(+) T cell positive selection by generating the major histocompatibility complex class II (MHCII) bound peptide ligands presented by cortical thymic epithelial cells (PubMed:12021314). Also mediates invariant chain processing in cortical thymic epithelial cells (PubMed:9545226). Major elastin-degrading enzyme at neutral pH. Accumulates as a mature and active enzyme in the extracellular space of antigen presenting cells (APCs) to regulate degradation of the extracellular matrix in the course of inflammation (PubMed:12417635). Secreted form generates endostatin from COL18A1 (PubMed:10716919). Critical for cardiac morphology and function (PubMed:11972068). Plays an important role in hair follicle morphogenesis and cycling, as well as epidermal differentiation (PubMed:12163394). Required for maximal stimulation of steroidogenesis by TIMP1 (By similarity).

During export along the endocytic pathway, pro-CTSL undergoes several proteolytic cleavages to generate the CTSL single-chain and two-chain mature forms, composed of a heavy chain linked to a light chain by disulfide bonds (PubMed:11483509). Autocleavage; produces the single-chain CTSL after cleavage of the propeptide. The cleavage can be intermolecular (By similarity).

Belongs to the peptidase C1 family.

Expressed in thymus, kidney and liver (PubMed:9545226). Expressed in thyroid epithelial cells. Expressed in cortical thymic epithelial cells (PubMed:9545226). Expressed by antigen presenting cells (APCs) such as dendritic cells and macrophages (PubMed:11483509, PubMed:12417635).

• Lysosome
• Apical cell membrane
• Peripheral membrane protein
• Extracellular side
• Secreted
• Extracellular space
• Secreted
• Cytoplasmic vesicle
• Secretory vesicle
• Chromaffin granule
• Localizes to the apical membrane of thyroid epithelial cells. Released at extracellular space by activated dendritic cells and macrophages (PubMed:12417635).

Ctsl1, Ctsl, Procathepsin L, Cathepsin L1, Major excreted protein, p39 cysteine proteinase, MEP

• entrezGene:13039
• swissprot:P06797

Proteins

Neuroscience

37547Da