Cathepsin B

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Cathepsin B belongs to a family of lysosomal cysteine proteases known as the cysteine cathepsins and plays an important role in intracellular proteolysis.^[5] In humans, cathepsin B is encoded by the CTSB gene.^[6][7] Cathepsin B is upregulated in certain cancers, in pre-malignant lesions, and in various other pathological conditions.^{[8][9][10][11]}

CTSB
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 3PBH, 1CSB, 1GMY, 1HUC, 1PBH, 2IPP, 2PBH, 3AI8, 3CBJ, 3CBK, 3K9M
Identifiers
Aliases	CTSB, APPS, CPSB, cathepsin B, RECEUP
External IDs	OMIM: 116810; MGI: 88561; HomoloGene: 37550; GeneCards: CTSB; OMA:CTSB - orthologs
Gene location (Human) Chr. Chromosome 8 (human)[1] Band 8p23.1 Start 11,842,524 bp[1] End 11,869,448 bp[1]
Gene location (Mouse) Chr. Chromosome 14 (mouse)[2] Band 14 D1|14 33.24 cM Start 63,359,911 bp[2] End 63,383,372 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in stromal cell of endometrium right lobe of thyroid gland left lobe of thyroid gland appendix canal of the cervix gallbladder ectocervix smooth muscle tissue olfactory zone of nasal mucosa monocyte Top expressed in stroma of bone marrow calvaria white adipose tissue subcutaneous adipose tissue epithelium of stomach brown adipose tissue tibiofemoral joint tunica adventitia of aorta decidua lactiferous gland More reference expression data BioGPS More reference expression data
Gene ontology Molecular function cysteine-type peptidase activity collagen binding peptidase activity protein binding cysteine-type endopeptidase activity hydrolase activity proteoglycan binding serine-type endopeptidase activity endopeptidase activity Cellular component intracellular membrane-bounded organelle melanosome intracellular anatomical structure extracellular region endolysosome lumen nucleolus mitochondrion lysosome extracellular exosome perinuclear region of cytoplasm extracellular space ficolin-1-rich granule lumen collagen-containing extracellular matrix Biological process regulation of apoptotic process epithelial cell differentiation proteolysis toll-like receptor signaling pathway decidualization cellular response to thyroid hormone stimulus collagen catabolic process viral entry into host cell regulation of catalytic activity proteolysis involved in cellular protein catabolic process neutrophil degranulation Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 1508 13030 Ensembl ENSG00000164733 ENSG00000285132 ENSMUSG00000021939 UniProt P07858 P10605 RefSeq (mRNA) NM_001908 NM_147780 NM_147781 NM_147782 NM_147783 NM_001317237 NM_007798 RefSeq (protein) NP_001304166 NP_001899 NP_680090 NP_680091 NP_680092 NP_680093 NP_031824 Location (UCSC) Chr 8: 11.84 – 11.87 Mb Chr 14: 63.36 – 63.38 Mb PubMed search [3] [4]
Wikidata
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Structure

Gene

The CTSB gene is located at chromosome 8p22, consisting of 13 exons. The promoter of CTSB gene contains a GC-rich region including many SP1 sites, which is similar to housekeeping genes.^[12] At least five transcript variants encoding the same protein have been found for this gene.^[13]

Protein

Cathepsin B is synthesized on the rough endoplasmic reticulum as a preproenzyme of 339 amino acids with a signal peptide of 17 amino acids.^[14][15] Procathepsin B of 43/46 kDa is then transported to the Golgi apparatus, where cathepsin B is formed. Mature cathepsin B is composed of a heavy chain of 25-26 kDa and a light chain of 5kDa, which are linked by a dimer of disulfide.

Function

Cathepsin B may enhance the activity of other proteases, including matrix metalloproteinase, urokinase (serine protease urokinase plasminogen activator), and cathepsin D,^[16][17] and thus it has an essential position for the proteolysis of extracellular matrix components, intercellular communication disruption, and reduced protease inhibitor expression.^[11]

Cells may become carcinogenic when cathepsin B is unregulated.^[18]

Potential in disease

Cathepsin B has been proposed as a potentially effective biomarker for a variety of cancers.^[16][19] Overexpression of cathepsin B is correlated with invasive and metastatic cancers.^[20]

Cathepsin B has been shown to be involved in the pathogenesis of pancreatitis, by prematurely activating the digestive enzyme trypsinogen within the pancreas, leading to autodigestion of acinar cells.^[21][22][23]

Interactions

Cathepsin B has been shown to interact with:

• CTSD^[24]
• CSTA,^[25][26]
• CSTB,^[25][27] and
• S100A10.^[28]

Cathepsin B is inhibited by:

• Nitroxoline^[29]
• CA-074^[30]

See also

• Cathepsins