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BTLA, also known as B And T Lymphocyte Associated, is an inhibitory molecule which is part of the Ig superfamily. BTLA is a type 1 transmembrane glycoprotein in the CD28 family of T cell costimulatory molecules. BTLA is a 3rd inhibitory receptor on T lymphocytes with resemblances to CTLA-4 & PD-1. Moreover, BTLA is a ligand for TNF (receptor) superfamily, TNFRSF14, and HVEM. BTLA-HVEM complexes negatively regulate T-cell immune responses.

PDXK converts vitamin B6 to Pyridoxal-5-phosphate (PLP), which is a vital cofactor in the intermediate metabolism of amino acids and neurotransmitters. PDXK is cytoplasmic and probably acts as a homodimer. The biological validity of the alternatively spliced transcript variants has not been determined.

Penta-EF-hand domain containing 1 (PEF1) is a member of the penta-EF-hand protein family, which shares similarities to the apoptosis linked gene ALG-2. PEF1 forms heterodimers with PDCD6/ALG2 and dissociates from PDCD6/ALG2 in the presence of Ca (2+). Furthermore, PEF1 proteins bind calcium and participate in a various calcium-dependent processes in vertebrates.

Pyruvate kinase is a key enzyme in the glycolytic pathway. The M2 isoenzyme of pyruvate kinase is specifically expressed at high levels in tumor cells, and can be measured in plasma of patients with advanced breast cancer. The marker is useful for measuring disease activity, sensitivity to chemotherapy and recurrence.

PSMA6 belongs to the peptidase T1A family, which is a 20S core alpha subunit. The proteasome is a multicatalytic proteinase complex with an extremely organized ring-shaped 20S core structure. The core structure consists of 4 rings of 28 non-identical subunits; 2 rings consist of 7 alpha subunits and 2 rings consist of 7 beta subunits. PSMA6 is spread all over eukaryotic cells in large quantities and cleave peptides in an ATP/ubiquitin-dependent procedure in a non-lysosomal pathway.

Alanine aminotransferase 2 (GPT2), catalyzes the reversible transamination among alanine and 2-oxoglutarate to create pyruvate and glutamate. GPT2 expressed mainly in muscle, fat and kidney and participates in the intermediary metabolism of glucose and amino acids. Multiple transcript variants encoding various isoforms have been found for GPT2.

PSMB5 belongs to the proteasome B-type family that has a 20S core beta subunit in the proteasome. This catalytic subunit is not present in the immunoproteasome and is substituted by catalytic subunit 3i (proteasome beta 8 subunit). A fundamental function of a modified proteasome, the immunoproteasome, is the processing of class I MHC peptides. PSMB5 exhibits an ATP dependent proteolytic activity and is involved in an ATP/ubiquitin dependent non lysosomal proteolytic pathway.

PSME3 is a member of the PA28 family. The 26S proteasome is an extremely organized multicatalytic proteinase complex composed of 2 complexes, a 20S core and a 19S regulator. Proteasomes are spread all over the eukaryotic cells in large quantities and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. PSME3 stimulates the trypsin-like catalytic subunit of the proteasome and inhibits the chymotrypsin-like and postglutamyl-preferring (PGPH) subunits. PSEM3 enables the MDM2-p53/TP53 collaboration that encourages ubiquitination- and MDM2-dependent proteasomal degradation of p53/TP53, restricting its growth and causing inhibited apoptosis after DNA damage.

Collagen triple helix repeat-containing protein 1 (CTHRC1) functions as a negative regulator of collagen matrix deposition. CTHRC1 is a secreted 28kDa protein which is glycosylated and highly conserved from lower chordates to mammals. CTHRC1 is highly connected with calcified tissues and cartilaginous matrix, but not with endothelial cells. CTHRC1 is detected qualitatively in plasma of healthy human subjects. CTHRC1 plasma levels are also significantly elevated during pregnancy, in diabetes, in inflammatory and infectious conditions, in subjects with acute myeloid leukemia but not in subjects with solid cancers. The hormonal functions of CTHRC1 include regulation of lipid storage and cellular glycogen levels with potentially far-reaching implications for cell metabolism and physiology. CTHRC1 gene deletion leads to fatty liver (steatosis) formation in mice while others exhibited inactivation of the CTHRC1 gene also results in low bone mass.

ATP synthase subunit gamma, mitochondrial isoform L (liver) (ATP5C1) is a member of the ATPase gamma chain family. ATP5C1 catalyzes ATP synthesis by using an electrochemical gradient of protons across the inner membrane throughout oxidative phosphorylation. The catalytic portion of mitochondrial ATP synthase is comprised of 5 different subunits (alpha, beta, gamma, delta, and epsilon) gathered with a stoichiometry of 3 alpha, 3 beta, and a single representative of the other 3.

Lymphokine-activated killer T-cell-originated protein kinase (PBK) is a serine/threonine kinase related to the dual specific mitogen-activated protein kinase (MAPKK) family. PBK is abundant in placenta (is also found in the testis’ outer cell layer of seminiferous tubules) and absent from adult brain tissue. PBK is involved in the activation of lymphoid cells and supports testicular functions, with a possible role in the process of spermatogenesis. Mitotic phosphorylation is required for PBK’s catalytic activity. Once phosphorylated,PBK forms a complex with TP53, leading to TP53 destabilization and weakening of G2/M checkpoint during some kind of DNA damage. PBK is active only during mitosis. In addition, a PDZ domain in the tumor suppressor protein Dlg can coordinate with the T/SXV motif of PBK. PBK also phosphorylates MAP kinase p38, and may have a role in the activation of lymphoid cells.

PGK1 is an X-linked enzyme that has a major role in the glycolytic pathway. PGK1 is a glycolytic enzyme which catalyzes the conversion of 1,3-diphosphoglycerate to 3-phosphoglycerate, generating an ATP molecule. PGK1 may also act as a cofactor for polymerase alpha. Defects in the PGK1 gene are usually associated with chronic hemolytic anemia, though it can be accompanied by either mental retardation or muscular disease (rhabdomyolysis). Overexpression of PGK1 and its signalling targets are possibly an expression-pathway in diffuse primary gastric carcinomas promoting peritoneal dissemination. It was shown that PGK1 is differentially expressed in the dorsolateral prefrontal cortex from patients with schizophrenia.

Inositol-tetrakisphosphate 1-kinase (ITPK1) is a 414 amino acid monomer which is a member of the ITPK1 family and exists as 2 alternatively spliced isoforms. ITPK1 highest levels are found in the brain, followed by the heart, skeletal muscle, kidney, pancreas, liver, placenta and lung. ITPK1 is comprised of one ATP-grasp domain and has been shown to phosphorylate various inositol polyphosphates and modify TNFa induced apoptosis.

CTK-19 is a member of the keratin family. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. The type I cytokeratins consist of acidic proteins which are arranged in pairs of heterotypic keratin chains. Unlike its related family members, this smallest known acidic cytokeratin is not paired with a basic cytokeratin in epithelial cells. It is specifically expressed in the periderm, the transiently superficial layer that envelopes the developing epidermis. The type I cytokeratins are clustered in a region of chromosome 17q12-q21.

PPIF is a part of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIF accelerates the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. PPIF is key component of the mitochondrial permeability transition pore in the inner mitochondrial membrane. Activation of this pore is thought to be involved in the induction of apoptotic and necrotic cell death.

Protein Phosphatase 1, Regulatory Subunit 3B (PPP1R3B) is the catalytic subunit of the serine/theonine phosphatase, protein phosphatase-1. PPP1R3B, which is expressed both in liver and in skeletal muscle tissue, regulates glycogen synthesis in these tissues. PPP1R3B is involved in type 2 diabetes and maturity-onset diabetes of the young.

PSG5 belongs to the PSG family, which are a highly connected group of secreted glycoproteins, vastly expressed in fetal placental syncytiotrophoblast cells. PSGs are can be found in serum from the first 2-3 weeks of pregnancy and at higher levels as the pregnancy progresses, up to e point where they are the highest fetal protein found in maternal blood at term. PSG5’s role is inducing secretion of TH2-type cytokines from monocytes and modulating the maternal immune system throughout the pregnancy, thus defending the semi-allotypic fetus from rejection.

Threonyl-tRNA Synthetase is a member of the aminoacyl-tRNA synthetase family, key enzymes of protein biosynthesis which charge tRNA molecules with the respective amino acids. This 83 kDa protein is an autoantigen recognized by PL-7 antibodies which occur in a subset of patients with polymyositis and dermatomyositis. Preliminary data suggest that PL-7 antibodies (similar to Jo-1 antibodies) indicate an increased risk for lung involvement, but this needs to be confirmed for a larger number of cases.

Platelet-derived growth factor receptor beta (PDGFRB), belongs to the class III subfamily of receptor tyrosine kinases (RTK) which also consist of the receptors for Flt3-ligand, SCF and M-CSF. PDGFRB takes a vital part in blood vessel development by promoting growth, migration as well as recruitment of pericytes and smooth muscle cells to endothelial cells. PDGFRB helps in rearrangement of the actin cytoskeleton in addition the formation of membrane ruffles. PDGFRB phosphorylates, NCK1, PIK3R1, PTPN11, CBL, SHC1, RASA1/GAP and PLCG1.

POU5F1 is a homeodomain transcription factor of the POU family, expressed in embryonic stem (ES) cells and embryonic carcinoma (EC) cells.POU5F1 is significantly involved in the signaling pathway for maintaining self-renewal and pluripotency of ES cells. POU5F1 has 2 distinct DNA binding domains which independently bind half-sites of the canonical octamer motif. This flexibility allows POU5F1 to bind with distinct DNA motifs by forming heterodimers with other transcription factors or by forming homodimers in several conformations. Human POU5F1 contains a 75aa POU specific (POUS) domain and a 60aa POU-Homeo-(POUH) domain connected by a linker region. The Human POU5F1 specifically interacts with Octamer motif ATGCAAAT. In addition, 2 proline-rich domains in the N-terminal and C-terminal regions are vital for POU5F1 transactivation. POU5F1 regulates a number of target genes and has been shown to work jointly with other transcription factors including Sox2 as well as Nanog to sustain stem cell potency and self-renewal.

Cadherin 11 (CDH11) belongs to the cadherin superfamily (integral membrane proteins) which mediate calcium-dependent cell-cell adhesion. CDH11 is defined based on lacking a HAV cell adhesion recognition sequence specific to type I cadherins. CDH11 protein’s expression in osteoblastic cell lines, and its upregulation during differentiation, suggests a specific function in bone development and maintenance. CDH11 contributes to the sorting of heterogeneous cell types.

PSMB6 belongs to the proteasome B-type family (T1B family) which is a 20S core beta subunit in the proteasome. The PSMB6 is not present in the immunoproteasome and is replaced by PSMB9. The proteasome is a multicatalytic proteinase complex with an extremely ordered ring-shaped 20S core structure. The core structure is comprised 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.

Dehydrogenase/reductase SDR family member 8 (HSD17B11) is a member of the HSD17B family of proteins, which regulate the availability of steroids within various tissues throughout the body. HSD17B11 is widely expressed with the highest levels found in the retina, pancreas, kidney, liver, lung, adrenal, small intestine, ovary and heart as well as in steroidogenic cells. HSD17B11 converts androstan-3-?,17-?-diol (3-?-diol) to androsterone, suggesting it may participate in androgen metabolism during steroidogenesis.

Phosphoribosylaminoimidazole Carboxylase (PAICS) is an enzyme involved in nucleotide biosynthesis and particularly in purine biosynthesis. PAICS is a bifunctional enzyme containing phosphoribosylaminoimidazole carboxylase activity at its N-terminal region and phosphoribosylaminoimidazole succinocarboxamide synthetase at its C-terminal region. PAICS catalyzes the conversion of 5'-phosphoribosyl-5-aminoimidazole(AIR) into 5'-phosphoribosyl-4-carboxy-5-aminoimidazole (CAIR) as described in the reaction. PAICS catalyzes steps six and seven of purine biosynthesis.