lysosomal

Scavenger Receptor Class B Member 2 (SCARB2) is a type III multi-pass membrane glycoprotein that is located primarily in limiting membranes of lysosomes and endosomes on all tissues and cell types so far examined. Earlier studies in mice and rat suggested that this protein may participate in membrane transportation and the reorganization of endosomal/lysosomal compartment. The protein deficiency in mice was reported to impair cell membrane transport processes and cause pelvic junction obstruction, deafness, and peripheral neuropathy. Further studies in human showed that this protein is identified as a receptor for EV71 (human enterovirus species A, Enterovirus 71) and CVA16 (coxsackievirus A16) which are most frequently associated with hand, foot and mouth disease (HFMD). Mutations in this gene caused an autosomal recessive progressive myoclonic epilepsy-4 (EPM4), also known as action myoclonus-renal failure syndrome (AMRF). Alternatively spliced transcript variants encoding different isoforms have been found for this gene. In addition, SCARB2 also has been shown to bind thrombospondin-1, may contribute to the pro-adhesive changes of activated platelets during coagulation, and inflammation.

Glucosylceramidase that catalyzes, within the lysosomal compartment, the hydrolysis of glucosylceramide/GlcCer into free ceramide and glucose. Thereby, plays a central role in the degradation of complex lipids and the turnover of cellular membranes. Through the production of ceramides, participates in the PKC-activated salvage pathway of ceramide formation. Also plays a role in cholesterol metabolism. May either catalyze the glucosylation of cholesterol, through a transglucosylation reaction that transfers glucose from glucosylceramide to cholesterol. The short chain saturated C8:0-GlcCer and the mono-unsaturated C18:0-GlcCer being the most effective glucose donors for that transglucosylation reaction. Under specific conditions, may alternatively catalyze the reverse reaction, transferring glucose from cholesteryl-beta-D-glucoside to ceramide. Finally, may also hydrolyze cholesteryl-beta-D-glucoside to produce D-glucose and cholesterol.

Catalyzes the deacylation of triacylglyceryl and cholesteryl ester core lipids of endocytosed low density lipoproteins to generate free fatty acids and cholesterol. LIPA Protein, Human, Recombinant (GST) is expressed in E. coli expression system with N-GST tag. The predicted molecular weight is 70.0 kDa and the accession number is P38571.

LAMP1 Protein, Human, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 39.8 kDa and the accession number is A0A024RDY3.

LAMP1 Protein, Rat, Recombinant (hFc) is expressed in HEK293 mammalian cells with hFc tag. The predicted molecular weight is 65.1 kDa and the accession number is P14562.

LAMP2 Protein, Human, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 39.77 kDa and the accession number is P13473-2.

Acts as a lysosomal receptor for glucosylceramidase (GBA) targeting. LIMPII/SR-B2 Protein, Rat, Recombinant (His & Myc) is expressed in E. coli expression system with N-10xHis and C-Myc tag. The predicted molecular weight is 53.7 kDa and the accession number is P27615.

LAMP3/CD208 Protein, Human, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 39 kDa and the accession number is Q9UQV4.

Ragulator complex protein LAMTOR2, also known as Endosomal adaptor protein p14, Late endosomal/lysosomal Mp1-interacting protein, Late endosomal/lysosomal adaptor and MAPK and MTOR activator 2, Mitogen-activated protein-binding protein-interacting protein, Roadblock domain-containing protein 3, LAMTOR2, MAPBPIP, and ROBLD3, is a protein which belongs to the GAMAD family. LAMTOR2 / ROBLD3 is a regulator of the TOR pathway, a signaling cascade that promotes cell growth in response to growth factors, energy levels, and amino acids. As part of the Ragulator complex, LAMTOR2 / ROBLD3 recruits the Rag GTPases and the mTORC1 complex to lysosomes, a key step in the activation of the TOR signaling cascade by amino acids. LAMTOR2 / ROBLD3 is an adapter protein that enhances the efficiency of the MAP kinase cascade facilitating the activation of MAPK2. Defects in LAMTOR2 are the cause of immunodeficiency due to defects in MAPBP-interacting protein (ID-MAPBPIP). This form of primary immunodeficiency syndrome includes congenital neutropenia, partial albinism, short stature, and B-cell and cytotoxic T-cell deficiency.

LAMP2 Protein, Mouse, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 40.6 kDa and the accession number is P17047-1.

LAMP2 Protein, Cynomolgus, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 42.4 kDa and the accession number is G7Q3L7.

PLA2G15 Protein, Canine, Recombinant (His & Myc) is expressed in Baculovirus insect cells with N-10xHis and C-Myc tag. The predicted molecular weight is 46.8 kDa and the accession number is Q6XPZ3.

Catalyzes the deacylation of triacylglyceryl and cholesteryl ester core lipids of endocytosed low density lipoproteins to generate free fatty acids and cholesterol. LIPA Protein, Human, Recombinant (His) is expressed in yeast with N-6xHis tag. The predicted molecular weight is 45.0 kDa and the accession number is P38571.

N/A. ASAH2B Protein, Human, Recombinant (His) is expressed in E. coli expression system with N-6xHis tag. The predicted molecular weight is 23.0 kDa and the accession number is P0C7U1.

PLA2G15 Protein, Mouse, Recombinant (His & Myc) is expressed in E. coli expression system with N-10xHis and C-Myc tag. The predicted molecular weight is 50.5 kDa and the accession number is Q8VEB4.

GBA Protein, Mouse, Recombinant (His & SUMO) is expressed in E. coli.

ATP6V1F encodes a component of vacuolar ATPase mediating acidification. The cDNA and the genomic sequences of ATP6V1F were cloned successfully for the first time from the Giant Panda (Ailuropoda melanoleuca) using reverse transcription polymerase chain reaction and touchdown-polymerase chain reaction, respectively. Topology prediction showed that there is one protein kinase C phosphorylation site, two Casein kinase II phosphorylation sites, and one N-myristoylation site in the ATP6V1F protein. Up-regulated expression of mammary tumor 8 kDa protein (MAT-8), complement component C1S (C1S), ferritin heavy chain (FTH1), peptidyl-prolyl cis-trans isomerase A (PPIA), RNA-binding protein regulatory subunit DJ-1 protein (DJ-1) and vacuolar ATP synthase subunit F (ATP6V1F) was determined in prostate carcinoma and confirmed by using quantitative real-time RT-PCR analyses.

Lysosome membrane protein II (LIMPII)，also known as SCARB2, is a type III multi-pass membrane glycoprotein that is located primarily in limiting membranes of lysosomes and endosomes on all tissues and cell types so far examined. Earlier studies in mice and rat suggested that this protein may participate in membrane transportation and the reorganization of endosomal/lysosomal compartment. The protein deficiency in mice was reported to impair cell membrane transport processes and cause pelvic junction obstruction, deafness, and peripheral neuropathy. Further studies in human showed that this protein is identified as a receptor for EV71 (human enterovirus species A, Enterovirus 71) and CVA16 (coxsackievirus A16) which are most frequently associated with hand, foot and mouth disease (HFMD). Mutations in this gene caused an autosomal recessive progressive myoclonic epilepsy-4 (EPM4), also known as action myoclonus-renal failure syndrome (AMRF). Alternatively spliced transcript variants encoding different isoforms have been found for this gene. In addition, LIMPII also has been shown to bind thrombospondin-1, may contribute to the pro-adhesive changes of activated platelets during coagulation, and inflammation.

Lysosomal Pro-X Carboxypeptidase (PRCP) belongs to the peptidase S28 family. PRCP is detected in many tissues, with highest levels observed in placenta, lung, and liver. It is also present in the heart, brain, pancreas, and kidney. PRCP exists as a homodimer. PRCP cleaves C-terminal amino acids linked to proline in peptides such as angiotensin II, III and des-Arg9-bradykinin. This cleavage occurs at acidic pH, but enzymatic activity is retained with some substrates at neutral pH. PRCP has been shown to be an activator of the cell matrix-associated prekallikrein.

Sialidase-1 belongs to the N-acetyl-a neuraminidase family. Sialidase-1 is expressed in many tissues; it is highly expressed in the pancreas, and weakly expressed in the brain. Sialidase-1 is a lysosomal enzyme, which cleaves terminal sialic acid residues from substrates such as glycoproteins and glycolipids. Deficiencies in the human enzyme Sialidase-1 leads to sialidosis, a rare lysosomal storage disease. Sialidase-1 has been shown to interact with Cathepsin A (protective protein), β-galactosidase and N-acetylgalactosamine-6-sulfate sulfatase in a multienzyme complex.

Mitogen-Activated Protein Kinase Scaffold Protein 1 (MAPKSP1) was identified as an interacting protein that belongs to the LAMTOR3 family. MAPKSP1 restricted to late endosomes by the mitogen-activated protein-binding protein-interacting protein, and binds specifically to MAP kinase kinase MAP2K1/MEK1, MAP kinase MAPK3/ERK1, and MAP kinase MAPK1/ERK2. MAPKSP1 interacts with MAP2K1/MEK1 and MAPK2 and enhances the activation of MAPK2, and thus is thought to function as an adaptor to enhance the efficiency of the MAP kinase cascade.

ASAH2 Protein, Human, Recombinant (His) is expressed in E. coli expression system with N-6xHis tag. The predicted molecular weight is 25.2 kDa and the accession number is Q9NR71.

LAMTOR1 Protein, Human, Recombinant (His) is expressed in E. coli.

Renin receptor Protein, Human, Recombinant (His) is expressed in E. coli.

GBA Protein, Mouse, Recombinant (His) is expressed in yeast with N-6xHis tag. The predicted molecular weight is 57.5 kDa and the accession number is P17439.

ASAH2 (N-acylsphingosine amidohydrolase 2), also known as neutral ceramidase, is a type II integral membrane protein that can be cleaved to produce a soluble secreted protein. The enzyme is abundant in the brush border membranes of the intestine, and also expressed in several tissues such as kidney, brain and liver. The primary structure of ASAH2/neutral ceramidase is highly conserved from bacteria to humans, however, there is a clear difference in the molecular architecture. The murine ASAH2 possesses ‘amucin box’, a Ser/Thr/Pro-rich domain glycosylated with O-glycans which is necessary to retain the enzyme on the plasma membrane as a type II integral protein. The major physiological function of ASAH2/neutral ceramidase is the metabolism of dietary sphingolipids, and thus plays a role in the generation of messenger molecules such as sphingosine and sphingosine 1-phosphate.

LAMP3/CD208 Protein, Rhesus, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 36.6 kDa and the accession number is Q8MJJ2.

Lysosomal associated membrane protein 1 (LAMP1) is an approximately 120 kDa transmembrane glycoprotein that is a major protein component of lysosomal membranes. Mature mouse LAMP1 consists of a 346 amino acid (aa) intralumenal domain (ECD), a 24 aa transmembrane segment, and a 12 aa cytoplasmic tail. Its lumenal domain is organized into two heavily N-glycosylated regions separated by a Ser/Pro-rich linker that carries a minor amount of O-linked glycosylation. Within the lumenal domain, mouse LAMP1 shares approximately 64% and 82% aa sequence identity with human and rat LAMP1, respectively. The sorting of LAMP1 to lysosomes relies on a tyrosine motif in the cytoplasmic tail. In cytotoxic T cells and mast cells, LAMP1 is expressed in the membranes of intracellular granules that contain effector molecules such as perforin, granzymes, eicosanoids, and histamine. A glycoform of LAMP1 known as M150 is expressed on the surface of activated macrophages where it promotes T cell co-stimulation and a Th1 biased immune response. Exposure of epithelial cells to pathogenic Neisseria bacteria induces the redistribution of LAMP1 to the cell surface where it can be cleaved by the Neisseria IgA1 protease.

Glucosylceramidase that catalyzes, within the lysosomal compartment, the hydrolysis of glucosylceramide/GlcCer into free ceramide and glucose. Thereby, plays a central role in the degradation of complex lipids and the turnover of cellular membranes. Through the production of ceramides, participates in the PKC-activated salvage pathway of ceramide formation. Also plays a role in cholesterol metabolism. May either catalyze the glucosylation of cholesterol, through a transglucosylation reaction that transfers glucose from glucosylceramide to cholesterol. The short chain saturated C8:0-GlcCer and the mono-unsaturated C18:0-GlcCer being the most effective glucose donors for that transglucosylation reaction. Under specific conditions, may alternatively catalyze the reverse reaction, transferring glucose from cholesteryl-beta-D-glucoside to ceramide. Finally, may also hydrolyze cholesteryl-beta-D-glucoside to produce D-glucose and cholesterol.

Catalyzes the removal of sialic acid (N-acetylneuraminic acid) moieties from glycoproteins and glycolipids. To be active, it is strictly dependent on its presence in the multienzyme complex. Appears to have a preference for alpha 2-3 and alpha 2-6 sialyl linkage. Sialidase-1 Protein, Mouse, Recombinant (His) is expressed in E. coli expression system with N-10xHis tag. The predicted molecular weight is 46.3 kDa and the accession number is O35657.

Catalyzes the deacylation of triacylglyceryl and cholesteryl ester core lipids of endocytosed low density lipoproteins to generate free fatty acids and cholesterol. LIPA Protein, Rat, Recombinant (His) is expressed in E. coli expression system with N-6xHis tag. The predicted molecular weight is 48.6 kDa and the accession number is Q64194.

GBA2 Protein, Rat, Recombinant (His) is expressed in E. coli expression system with C-6xHis tag. The predicted molecular weight is 42.6 kDa and the accession number is Q5M868.

BLOC1S2, also known as BLOS2, belongs to the BLOC1S2 family. It is a component of BLOC-1 complex. The BLOC-1 complex is composed of BLOC1S1, BLOC1S2, BLOC1S3, DTNBP1, MUTED, PLDN, CNO/cappuccino and SNAPIN. The BLOC-1 complex is required for normal biogenesis of lysosome-related organelles, such as platelet dense granules and melanosomes. BLOC1S2 interacts directly with BLOC1S1, BLOC1S3, MUTED, CNO/cappuccino and SNAPIN. It may play a role in cell proliferation. It also plays a role in intracellular vesicle trafficking. Functionally, BLOC1S2 gene has been proposed to participate in processes (melanosome organization, microtubule nucleation, platelet dense granule organization, positive regulation of cell proliferation, positive regulation of transcription, regulation of apoptosis, positive regulation of transcription from RNA polymerase II promoter).

Cathepsin L is an enzyme. Cathepsin L, a lysosomal endopeptidase expressed in most eukaryotic cells, is a member of the papain-like family of cysteine proteinases. Cathepsin L plays a major role in antigen processing, tumor invasion and metastasis, bone resorption, and turnover of intracellular and secreted proteins involved in growth regulation. Unlike the precursor forms of other papain family members, the 43 kDa pro-cathepsin L itself is secreted from various cells. Pro-cathepsin L is the major excreted protein of malignantly transformed mouse fibroblasts and is also one of the major acidic cysteine proteases in mammalian cells.

β Galactosidase is a lysosomal β Galactosidase that hydrolyzes the terminal β Galactose from Ganglioside and Keratan sulfate. In lysosome, the mature β Galactosidase protein associates with Cathepsin A and Neuraminidase 1 to form the lysosomal multienzyme complex . An alternative splicing at the RNA level of β Galactosidase results a catalytically inactive β Galactosidase that plays an important role in vascular development. Defects of β-galactosidase (GLB1) are the cause of diseases like GM1-gangliosidosis which is a lysosomal storage disease and Morquio Syndrome B that cause patients to have abnormal elastic fibers. More than 100 mutations have been identified for β Galactosidase, which result in different residual activities of the mutant enzymes and a spectrum of symptoms in the two related diseases.

RNF43 (E3 ubiquitin-protein ligase RNF43 or RING-type E3 ubiquitin transferase RNF43) functions as a tumor suppressor, by exerting a predominant negative feedback mechanism in the Wnt/β-catenin signaling pathway. RNF43 inhibits Wnt/beta-catenin signaling by ubiquitinating Frizzled receptor and targeting it to the lysosomal pathway for degradation.

Cathepsins are proteases found in many types of cells conserved in all animals, which have a vital role in mammalian cellular turnover such as bone resorption. The lysosomal cysteine protease Cathepsin C (CTSC), also known as dipeptidyl peptidase I (DPPI/DPP1), activates a number of granule-associated serine proteases with pro-inflammatory and immune functions by removal of their inhibitory N-terminal dipeptides. This lysosomal exo-cysteine protease belonging to the peptidase C1 family. Active cathepsin C is found in lysosomes as a 200-kDa multimeric enzyme. Subunits constituting this assembly all arise from the proteolytic cleavage of a single precursor giving rise to three peptides: the propeptide, the alpha- and the beta-chains. It is a central coordinator for activation of many serine proteases in immune/inflammatory cells. Defects in the Cathepsin C have been shown to be a cause of Papillon-Lefevre disease, an autosomal recessive disorder characterized by palmoplantar keratosis and periodontitis. Cathepsin C plays a key role in the activation of several degradative enzymes linked to tissue destruction in inflammatory diseases. Thus, it is a therapeutic target for the treatment of a number of inflammatory and autoimmune diseases.

IFI30 belongs to the GILT family. This family includes the two characterized human gamma-interferon-inducible lysosomal thiol reductase (GILT) sequences: P13284 and Q9UL08. It also contains several other eukaryotic putative proteins with similarity to GILT. The aligned region contains three conserved cysteine residues. Besides, the two GILT sequences possess a C-X(2)-C motif that is shared by some of the other sequences in the family. This motif is thought to be associated with disulfide bond reduction. IFI30 is a lysosomal thiol reductase that can reduce protein disulfide bonds. It facilitates the generation of MHC class II-restricted epitopes from disulfide bond-containing antigens by the endocytic reduction of disulfide bonds. It also facilitates MHC class I-restricted recognition of exogenous antigens containing disulfide bonds by CD8+ T-cells or cross-presentation. IFI30 may facilitate the complete unfolding of proteins destined for lysosomal degradation and plays an important role in antigen processing.

PSME2, also known as PA28b, is a subunit of proteasome. The 26S proteasome multicatalytic proteinase complex has a highly ordered structure composed of 2 complexes, a 2S core and a 19S regulator. The 2S core is composed of 4 rings of 28 non-identical subunits; 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. The 19S regulator is composed of a base, which contains 6 ATPase subunits and 2 non-ATPase subunits, and a lid, which contains up to 1 non-ATPase subunits. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. An essential function of a modified proteasome, the immunoproteasome, is the processing of class I MHC peptides. The immunoproteasome contains an alternate regulator, referred to as the 11S regulator or PA28, that replaces the 19S regulator. Three subunits (alpha, beta and gamma) of the 11S regulator have been identified. PSME2 gene encodes the beta subunit of the 11S regulator, one of the two 11S subunits that is induced by gamma-interferon. Three beta and three alpha subunits combine to form a heterohexameric ring.

Polyubiquitin-B(UBB) is one of Ubiquitins. Ubiquitin is one of the most conserved proteins known in eukaryotic organisms. Ubiquitin is required for ATP-dependent, non-lysosomal intracellular protein degradation of abnormal proteins and normal proteins with a rapid turnover. Ubiquitin is covalently bound to proteins to be degraded, and presumably labels these proteins for degradation.

Serpin B6 belongs to the serpin family. Serpin B6 localizes to the cytoplasm. Serpin B6 is expressed in many tissues, abundantly by mast cells in different tissues and mastocytoma lesions. Serpin B6 may be involved in the regulation of serine proteinases present in the brain or extravasated from the blood. In addition, Serpin B6 may play an important role in the inner ear in the protection against leakage of lysosomal content during stress and loss of this protection results in cell death and sensorineural hearing loss.

Protein AMBP belongs to the calycin superfamily and Lipocalin family. AMBP can be cleaved into three chains: α-1-microglobulin, inter-α-trypsin inhibitor light chain and trypstatin. AMBP is expressed by the liver and secreted in plasma. α-1-microglobulin occurs in many physiological fluids including the plasma, urine, and cerebrospinal fluid. Inter-α-trypsin inhibitor is present in the plasma and urine. α-1-microglobulin occurs as a monomer and also in complexes with IgA and albumin, Inter-α-trypsin inhibitor inhibits trypsin, plasmin and lysosomal granulocytic elastase. Trypstatin act as a trypsin inhibitor, exists in a monomer forms and also occurs as a complex with tryptase in mast cells.

Calcium-regulated non-lysosomal thiol-protease which catalyzes limited proteolysis of substrates involved in cytoskeletal remodeling and signal transduction. Proteolytically cleaves MYOC at 'Arg-226'. Proteolytically cleaves CPEB3 following neuronal stimulation which abolishes CPEB3 translational repressor activity, leading to translation of CPEB3 target mRNAs. CAPN2 Protein, Human, Recombinant (His) is expressed in E. coli expression system with N-6xHis tag. The predicted molecular weight is 82.1 kDa and the accession number is P17655.

Plays an important role in the regulation of different protein degradation mechanisms and pathways including ubiquitin-proteasome system (UPS), autophagy and endoplasmic reticulum-associated protein degradation (ERAD) pathway. Mediates the proteasomal targeting of misfolded or accumulated proteins for degradation by binding (via UBA domain) to their polyubiquitin chains and by interacting (via ubiquitin-like domain) with the subunits of the proteasome. Plays a role in the ERAD pathway via its interaction with ER-localized proteins UBXN4, VCP and HERPUD1 and may form a link between the polyubiquitinated ERAD substrates and the proteasome. Isoform 1, isoform 2 and isoform 3 play a role in unfolded protein response (UPR) by attenuating the induction of UPR-inducible genes, DDTI3/CHOP, HSPA5 and PDIA2 during ER stress. Involved in the regulation of macroautophagy and autophagosome formation; required for maturation of autophagy-related protein LC3 from the cytosolic form LC3-I to the membrane-bound form LC3-II and may assist in the maturation of autophagosomes to autolysosomes by mediating autophagosome-lysosome fusion. Negatively regulates the TICAM1/TRIF-dependent toll-like receptor signaling pathway by decreasing the abundance of TICAM1 via the autophagic pathway. Isoform 1 and isoform 3 play a key role in the regulation of the levels of PSEN1 by targeting its accumulation to aggresomes which may then be removed from cells by autophagocytosis. Promotes the ubiquitination and lysosomal degradation of ORAI1, consequently downregulating the ORAI1-mediated Ca2+ mobilization. Suppresses the maturation and proteasomal degradation of amyloid beta A4 protein (A4) by stimulating the lysine 63 (K63)-linked polyubiquitination. Delays the maturation of A4 by sequestering it in the Golgi apparatus and preventing its transport to the cell surface for subsequent processing.

Calcium-regulated non-lysosomal thiol-protease which catalyzes limited proteolysis of substrates involved in cytoskeletal remodeling and signal transduction. Proteolytically cleaves CTBP1 at 'Asn-375', 'Gly-388' and 'His-410'.

Iduronate 2-Sulfatase, also known as IDS, is a member of the highly conserved sulfatase family of enzymes that catalyze the hydrolysis of O- and N-sulfate esters from a variety of substrates. The human Iduronate 2-Sulfatase/IDS consists of a signal peptide, a propeptide, and a mature chain that may be further processed into two chains. Among the identified 18 human sulfatases, Iduronate 2-Sulfatase/IDS is required for the lysosomal degradation of the glycosaminoglycans (GAG), heparan sulfate, and dermatan sulfate. Multiple mutations in this X-chromosome localized gene result in Iduronate 2-Sulfatase/IDS enzymatic deficiency and lead to the sex-linked Mucopolysaccharidosis Type II (MPS II ), also known as Hunter Syndrome characterized by the lysosomal accumulation of the GAG and their excretion in urine. MPS II has a wide spectrum of clinical manifestations ranging from mild to severe due to the level of Iduronate 2-Sulfatase/IDS enzyme. Retroviral-mediated Iduronate 2-Sulfatase/IDS gene transfer into lymphoid cells would be a promising gene therapeutic strategy.

Cathepsin V (CTSV), also known as Cathepsin L2, CTSL2, and CATL2, is a member of the peptidase C1 family. It is predominantly expressed in the thymus and testis. Cathepsin V is also expressed in corneal epithelium, and to a lesser extent in conjuctival epithelium and skin. It is a lysosomal cysteine proteinase that may play an important role in corneal physiology. It has about 75% protein sequence identity to murine cathepsin L. The fold of this enzyme is similar to the fold adopted by other members of the papain superfamily of cysteine proteases. Cathepsin V has been recently described as highly homologous to Cathepsin L and exclusively expressed in human thymus and testis. Cathepsin V is the dominant cysteine protease in cortical human thymic epithelial cells, while Cathepsin L and Cathepsin S seem to be restricted to dendritic and macrophage-like cells. Active Cathepsin V in thymic lysosomal preparations was demonstrated by active-site labeling. Recombinant Cathepsin V was capable of converting Ii into CLIP efficiently, suggesting that it is the protease that controls the generation of alphabeta-CLIP complexes in the human thymus. Cathepsin V is the third elastolytic cysteine protease which exhibits the most potent elastase activity yet described among human proteases and that it is present in atherosclerotic plaque specimens. Cathepsin L2 may play a specialized role in the thymus and testis. Expression analysis of cathepsin L2 in human tumors revealed a widespread expression in colorectal and breast carcinomas but not in normal colon or mammary gland or in peritumoral tissues. Cathepsin L2 was also expressed by colorectal and breast cancer cell lines as well as by some tumors of diverse origin, including ovarian and renal carcinomas.

ASGR2 is a subunit of the asialoglycoprotein receptor. Asialoglycoprotein receptor, also known as the Ashwell receptor, which is specific for desialylated (galactosyl-terminal) glycoproteins and is expressed exclusively in hepatic parenchymal cells. This receptor is a transmembrane protein that plays a critical role in serum glycoprotein homeostasis by mediating the endocytosis and lysosomal degradation of glycoproteins with exposed terminal galactose or N-acetylgalactosamine residues. ASGR2 is a glycoprotein. The asialoglycoprotein receptor may facilitate hepatic infection by multiple viruses including hepatitis B, and is also a target for liver-specific drug delivery. The asialoglycoprotein receptor is a hetero-oligomeric protein composed of major and minor subunits, which are encoded by different genes. ASGR2 is the less abundant minor subunit.

PA28A, also known as PSME1, is a subunit of proteasome. The 26S proteasome multicatalytic proteinase complex has a highly ordered structure composed of 2 complexes, a 2S core and a 19S regulator. The 2S core is composed of 4 rings of 28 non-identical subunits; 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. The 19S regulator is composed of a base, which contains 6 ATPase subunits and 2 non-ATPase subunits, and a lid, which contains up to 1 non-ATPase subunits. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. An essential function of a modified proteasome, the immunoproteasome, is the processing of class I MHC peptides. The immunoproteasome contains an alternate regulator, referred to as the 11S regulator or PA28, that replaces the 19S regulator. Three subunits (alpha, beta and gamma) of the 11S regulator have been identified. PSME1 gene encodes the alpha subunit of the 11S regulator, one of the two 11S subunits that is induced by gamma-interferon. Three alpha and three beta subunits combine to form a heterohexameric ring.

PSME3, also known as PA28-gamma, is a subunit of proteasome. The 26S proteasome multicatalytic proteinase complex has a highly ordered structure composed of 2 complexes, a 2S core and a 19S regulator. The 2S core is composed of 4 rings of 28 non-identical subunits; 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. The 19S regulator is composed of a base, which contains 6 ATPase subunits and 2 non-ATPase subunits, and a lid, which contains up to 1 non-ATPase subunits. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. An essential function of a modified proteasome, the immunoproteasome, is the processing of class I MHC peptides. The immunoproteasome contains an alternate regulator, referred to as the 11S regulator or PA28, that replaces the 19S regulator. Three subunits (alpha, beta and gamma) of the 11S regulator have been identified. PSME3 gene encodes the gamma subunit of the 11S regulator. Six gamma subunits combine to form a homohexameric ring.