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Osteoprotegerin acts as decoy receptor for rankl and thereby neutralizes its function in osteoclastogenesis. OPG inhibits the activation of osteoclasts and promotes osteoclast apoptosis in vitro. Bone homeostasis seems to depend on the local rankl/opg ratio. Osteoprotegerin may also play a role in preventing arterial calcification. May act as decoy receptor for trail and protect against apoptosis. Trail binding blocks the inhibition of osteoclastogenesis.

A 16-kDa peptide hormone secreted from white adipocytes and implicated in the regulation of food intake and energy balance. Leptin provides the key afferent signal from fat cells in the feedback system that controls body fat stores.

Recombinant Human Sonic Hedgehog is part of a small group of secreted proteins that are vital for development in both vertebrates and invertebrates. 3 mammalian hedgehog genes (sonic, desert, Indian) share about 60% homology. The Human Sonic Hedgehog is 99% homologous to the mouse gene. Sonic HedgeHog is a protein that is vital in guding the early embryo. It has been associated as the major inductive signal in patterning of the ventral neural tube, the anterior-posterior limb axis, and the ventral somites. Sonic HedgeHog binds to the patched receptor, which functions in association with smoothened, to activate the transcription of target genes. In the absence of sonic HedgeHog, patched receptor represses the constitutive signaling activity of smoothened. Sonic HedgeHog also regulates another factor, the gli oncogene. Sonic HedgeHog intercellular signal is essential for a various patterning events during development: signal produced by the notochord that induces ventral cell fate in the neural tube and somites, and the polarizing signal for patterning of the anterior-posterior axis of the developing limb bud. Sonic HedgeHog exhibits both floor plate- and motor neuron-inducing activity. Mutations in a long-range Sonic HedgeHog enhancer located in an intron of the limb region 1 gene result in preaxial polydactyly.

Alanyl-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 108 kDa protein is an autoantigen recognized by PL-12 antibodies which occur in a subset of patients with polymyositis and dermatomyositis. Preliminary data suggest that epitope spreading occurs in the autoimmune PL-12 response such that even antibodies to an isolated alanyl-tRNA molecule can develop.

Alpha-2-antiplasmin (SERPINF2) is a serine protease inhibitor. The main targets of SERPINF2 are plasmin and trypsin; however SERPINF2 also inactivates matriptase-3/TMPRSS7 and chymotrypsin.

SPRY domain-containing SOCS box protein 1 (SPSB1) belongs to the SOCS box protein subfamily. SPSB1 includes a central SPRY domain and a C-terminal SOCS box. Even though, some of the SOCS protein subfamilies function as adaptors for a large family of ubiquitin-protein isopeptide ligases to regulate certain signaling pathways, the function of the SSB subfamily remains to be determined. SPSB1 may have an imperative role in enhancing the HGF-induced Erk-Elk-1-SRE pathway. SPSB1 overexpression exhibited no effect on the basal level or epidermal growth factor-induced SRE-luciferase activity.

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.

PDXP is the active form of vitamin B6 that functions as a coenzyme in preserving biochemical homeostasis. The desired degradation route from PLP to 4-pyridoxic acid involves the dephosphorylation of PLP by PDXP. PDXP shows activity to pyridoxal 5''-phosphate (PLP), pyridoxine 5''-phosphate (PMP) and Pyridoxine 5''-phosphate (PNP), with a highest activity with PLP followed by PNP.

GDF-11 belongs to the bone morphogenetic protein (BMP) family and the TGF-beta superfamily. GDF-11 is a central developmental factor which controls muscular and neural development. In adults, GDF-11 encourages cardiac hypertrophy reverse by the revival of cardiomyocytes.

ARL4A is related Specifically to ARL6 and ARL7 and belongs to the ARF-like protein (ARL) subfamily of small GTPases. However, unlike ARFs, ARL4 does not activate the cholera toxin ADP-ribosyltranferase. ARL4A takes part in neurogenesis during embryonic development and somitogenesis in the early stages of adult spermatogenesis.

ACOT11 belongs to the acyl-CoA thioesterase family which catalyses the transformation of activated fatty acids to the equivalent non-esterified fatty acid and coenzyme A. Expression of a mouse homolog in brown adipose tissue is induced by low temperatures and inhibited by high temperatures. Obesity-resistant mice demonstrated High levels of expression compared with obesity-prone mice, indicating BFIT takes part in acyl-CoA thioesterase 11 in obesity. BFIT has acyl-CoA thioesterase activity towards medium (C12) and long-chain (C18) fatty acyl-CoA substrates.

Dickkopf-related protein 3 (DKK3) belongs to the DKK protein family including Dkk-1, 2, 3 and -4. DKK3 is a 350 amino acid secreted glycoprotein which is comprised of an N-terminal signal peptide and 2 conserved cysteine-rich domains that are separated by a 12 amino acid linker region. DKK3 is involved in embryonic development through its inhibition of the WNT signaling pathway. DKK3 gene expression is decreased in a variety of cancer cell lines and it may act as a tumor suppressor gene.

Pirin (PIR) which belongs to the cupin superfamily, is an Fe(II)-containing nuclear protein expressed in all tissues of the body and concentrated within dot-like subnuclear structures. Pirin may function as a transcriptional cofactor and is involved in the regulation of DNA transcription and replication, as a result of interactions with nuclear factor I/CCAAT box transcription factor as well as B cell lymphoma 3-encoded oncoprotein.

Thiamin pyrophosphokinase 1 (TPK1) is a homodimer which catalyzes the phosphorylation of thiamine to thiamine pyrophosphate. TPK1 is found in the heart, kidney, testis, small intestine and peripheral blood leukocytes, and at very low levels in a variety of tissues. TPK1 gene defects cause the thiamine metabolism dysfunction syndrome type 5, episodic encephalopathy type (THMD5), which is an autosomal recessive metabolic disorder due to an inborn error of thiamine metabolism.

The alteration of proteins with ubiquitin is a vital cellular mechanism for targeting atypical or short-lived proteins for degradation. Ubiquitination involves noT less than three classes of enzymes: ubiquitin-activating enzymes, or E1s, ubiquitin-conjugating enzymes, or E2s, and ubiquitin-protein ligases, or E3s. UBE2A is part of the E2 ubiquitin-conjugating enzyme family. UBE2A is necessary for post-replicative DNA damage repair. UBE2A catalyzes the covalent attachment of ubiquitin to other proteins. UBE2A is necessary for postreplication repair of UV-damaged DNA.

Phosphoribosyl Pyrophosphate Synthetase-Associated Protein 2 (PRPSAP2) is a protein which relates with the enzyme phosphoribosylpyrophosphate synthetase (PRS). PRS catalyzes the formation of phosphoribosylpyrophosphate which is a substrate for synthesis of purine, pyrimidine, histidine, tryptophan and NAD. PRS is a complex with 2 catalytic subunits and 2 associated subunits. PRPSAP2 encodes a non-catalytic associated subunit of PRS.

GOT1 is a pyridoxal phosphate-dependent enzyme which exists in cytoplasmic and mitochondrial forms, GOT1 and GOT2, which participate in amino acid metabolism and the urea and tricarboxylic acid cycles. Both enzymes are homodimeric and show close homology.

UFC1 is a member of the ubiquitin-conjugating enzyme family. UFC1 is an E2-like conjugating enzyme for ubiquitin-fold modifier-1. UFM1 is activated by UBA5 (a novel E1-like enzyme) by forming a high-energy thioester bond. Activated UFM1 is subsequently transferred to its cognate E2-like enzyme, UFC1, in a similar thioester linkage.

COP9 signalosome complex subunit 8 isoform 1 (COPS8) is one of the 8 subunits of COP9 signalosome, which is a much conserved protein complex that functions as an imperative regulator in multiple signaling pathways. The structure and function of COP9 signalosome is analogous to that of the 19S regulatory particle of 26S proteasome. COP9 signalosome interacts with SCF-type E3 ubiquitin ligases and acts as a positive regulator of E3 ubiquitin ligases.

Tumor necrosis factor receptor superfamily member 21 or TNFRSF21, is a protein that located in the cell membrane from the TNF receptor superfamily. By activating the NF-kappaB pathway, TNFRSF21 promotes cell apoptosis. The degeneration of cells caused by activating caspase 3 and caspase 6, the TNFRSF21 binds to the N-terminal APP in neuronal cell bodies and axons which leads to apoptosis. TNFRSF21 takes part in signaling cascades activated by stimulation of T-cell receptor.

Ectodysplasin A Receptor, also known as EDAR belongs to the tumor necrosis factor receptor family. EDAR is a receptor for the soluble ligand ectodysplasin A, and is capable of activating the nuclear factor-kappaB, JNK, as well as caspase-independent cell death pathways. EDAR is necessary for the development of hair, teeth, and other ectodermal derivatives. Furthermore, mutations in EDAR resulted in autosomal dominant and recessive forms of hypohidrotic ectodermal dysplasia.

Methionine sulfoxide reductase B3 (MSRB3) is a member of the methionine sulfoxide reductases (MSR) family proteins. MSRB3 catalyzes the reduction of methionine sulfoxide to methionine. The MSRB3 enzyme acts as a monomer and requires zinc as a cofactor. MSRs are thought to defend against reactive oxygen species-induced oxidative damage in various organs, including the most environmentally exposed organ, the human skin. MSRB3 has a vital role in cold tolerance by eliminating MetO and ROS which accumulate at the ER during cold acclimation.

Celiac disease is an enteropathy that is characterized by intestinal lesions of variable severity. Tissue-type transglutaminase (tTG) is believed to be the predominant autoantigen for celiac disease and the corresponding autoantibodies show higher sensitivity and specificity than anti-gliadin antibodies. Highly pure recombinant human tTG is now available to replace the traditionally used tTG fraction from guinea pig.
Tissue-type transglutaminase antigens have been specifically modified for improved handling: exchange of an active site amino acid eliminates the protein cross-linking activity of the enzyme, while maintaining the native three-dimensional structure and the enzyme's secondary GTPase activity. This engineering assures reproducible properties of the antigen preparations through the absence of variable and ill-defined covalent aggregates of tTG antigen and host cell proteins.