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RARRES2 is a secreted chemotactic protein that initiates chemotaxis through the ChemR23 G protein-coupled seven-transmembrane domain ligand. RARRES2 is upregulated by the synthetic retinoid tazarotene and found in many tissues. RARRES2 acts as an adipokine and is truncated on both termini from the proprotein. RARRES2 is structurally related to the cathelicidin precursors, cystatin C and kininogens. RARRES2 promotes calcium mobilization and chemotaxis of immature dendritic cells and macrophages. RARRES2 is secreted as a precursor of little biological activity, which requires proteolytic cleavage of its COOH-terminal domain to be exchangeed into a potent and highly specific agonist of ChemR23.

Interleukin 13 Receptor, Alpha 2 (IL13RA2) is a member of the type I cytokine receptor family, Type 5 subfamily. IL13RA2 is related to l13RA1, a subunit of the interleukin 13 receptor complex. IL13RA2 binds IL13 with high affinity, though lacking the cytoplasmic domain, and does not appear to function as a signal mediator. IL13RA2 plays a role in the internalization of IL13.

Protein-c Receptor (PROCR) is a receptor for activated protein C, a serine protease activated by and involved in the blood coagulation pathway. The PROCR protein is an N-glycosylated type I membrane protein which enhances the activation of protein C. PROCR gene mutations are linked with venous thromboembolism and myocardial infarction, as well as with late fetal loss during pregnancy. In addition, PROCR may have a role in malarial infection and has been linked with cancer.

Fibroblast growth factors (FGFs) comprise a family of at least eighteen structurally related proteins that are involved in a multitude of physiological and pathological cellular processes, including cell growth, differentiation, angiogenesis, wound healing and tumorgenesis. The biological activities of the FGFs are mediated by a family of type I transmembrane tyrosine kinases which undergo dimerization and autophosphorylation after ligand binding. Four distinct genes encoding closely related FGF receptors, FGF R1 - 4, are known. All four genes for FGF Rs encode proteins with an N-terminal signal peptide, three immunoglobulin (Ig)-like domains, an acid-box region containing a run of acidic residues between the IgI and IgII domains, a transmembrane domain and the split tyrosine-kinase domain. Multiple forms of FGF R1 - 3 are generated by alternative splicing of the mRNAs. A frequent splicing event involving FGF R1 and 2 results in receptors containing all three Ig domains, referred to as the a isoform, or only IgII and IgIII, referred to as the b isoform. Only the a isoform has been identified for FGF R3 and FGF R4. Additional splicing events for FGF R1 - 3, involving the C-terminal half of the IgIII domain encoded by two mutually exclusive alternative exons, generate FGF receptors with alternative IgIII domains (IIIb and IIIc). A IIIa isoform which is a secreted FGF binding protein containing only the N-terminal half of the IgIII domain plus some intron sequences has also been reported for FGF R1. Mutations in FGF R1 - 3 have been found in patients with birth defects involving craniosynostosis. The complex patterns of expression of these receptors as well as the specificity of their interactions with the various FGF ligand family members are under investigation.

The Fas receptor (CD95) mediates apoptotic signaling by Fas-ligand expressed on the surface of other cells. The Fas-FasL interaction plays an important role in the immune system and lack of this system leads to autoimmunity, indicating that Fas-mediated apoptosis removes self-reactive lymphocytes. Fas signaling is also involved in immune surveillance to remove transformed cells and virus infected cells. Binding of FAS to oligimerized FasL on another cell activates apoptotic signaling through a cytoplasmic domain termed the death domain that interacts with signaling adaptors including FAF, FADD and DAX to activate the caspase proteolytic cascade. Caspase-8 and caspase-10 are first activated, to then cleave and activate downstream caspases, and a variety of cellular substrates that lead to cell death. Caspases cleave nuclear lamins, causing the nucleus to break down and lose its normal structure and another caspase substrate is DFF, inducing cleavage and degradation of the genome. Other caspase substrates are involved in cytoskeletal structure, cell cycle regulation and signaling pathways. Activation of JNK kinase, activation of Jun, and production of ceramide may also play roles in Fas-mediated apoptosis. Activation of fas-mediated apoptosis is opposed by I-FLICE and FAP. Viruses and tumors may escape immune surveillance in part through suppression of fas-mediated apoptosis using similar mechanisms.

EPH Receptor A2 (EPHA2) is a member of the ephrin receptor subfamily of the protein-tyrosine kinase family. EPHA2 is a protein which binds ephrin-A ligands. EPH and EPH-related receptors are associated with mediating developmental events, particularly in the nervous system. Receptors in the EPH subfamily normally have a single kinase domain and an extracellular region containing a Cys-rich domain and 2 fibronectin type III repeats. The ephrin receptors are divided into two groups based on the similarity of their extracellular domain sequences and their affinities for binding ephrin-A and ephrin-B ligands. EPHA2 gene mutations are the cause of certain genetically-related cataract disorders.

Human TNFRSF10A is a type 1 transmembrane protein in the TNF R superfamily. TNFRSF10A is not expressed in rodents. The trimeric ligand Trail binds TNFRSF10A and induces apoptosis, and recombinant, soluble forms of the receptor inhibit Trail-induced apoptosis. TNFRSF10A is expressed generally in damaged, infected, and malignant cells. TNFRSF10A functions in immune surveillance, inducing apoptosis in cancer cells but not normal cells.

RAET1E is a member of the MHC class I family. MHC class I family contains main histocompatibility complex (MHC) class I-related genes positioned in a cluster on chromosome 6q24.2-q25.3. RAET1E and RAET1G protein are different from other RAET1 proteins since they have type I membrane-spanning sequences at their C termini instead glycosylphosphatidylinositol anchor sequences.RAET1E acts as a ligand for NKG2D receptor, expressed on the surface of numerous types of immune cells, involves in innate adaptive immune reactions.RAET1E delivers signals to NK cells and advances tumor immune surveillance by inducing the growth of anti-tumor cytotoxic lymphocyte.

The epidermal growth factor receptor (EGF R) subfamily of receptor tyrosine kinases comprises four members: EGF R (also known as HER1, ErbB1 or ErbB), ErbB2 (Neu, HER-2), ErbB3 (HER-3), and ErbB4 (HER-4). All family members are type I transmembrane glycoprotein that has an extracellular domain which contains two cysteine-rich domains separated by a spacer region that is involved in ligand-binding, and a cytoplasmic domain which has a membrane-proximal tyrosine kinase domain and a C-terminal tail with multiple tyrosine autophosphorylation sites. The human EGF R gene encodes a 1210 amino acid (aa) residue precursor with a 24 aa putative signal peptide, a 621 aa extracellular domain, a 23 aa transmembrane domain, and a 542 aa cytoplasmic domain. EGF R has been shown to bind a subset of the EGF family ligands, including EGF, amphiregulin, TGF-a , betacellulin, epiregulin, heparin-binding EGF and neuregulin-2 in the absence of a co-receptor. Ligand binding induces EGF R homodimerization as well as heterdimerization with ErbB2, resulting in kinase activation, tyrosine phosphorylation and cell signaling. EGF R can also be recruited to form heterodimers with the ligand-activated ErbB3 or ErbB4. EGF R signaling has been shown to regulate multiple biological functions including cell proliferation, differentiation, motility and apoptosis. In addition, EGF R signaling has also been shown to play a role in carcinogenesis.

Insulin Receptor (INSR) is a receptor tyrosine kinase which mediates the pleiotropic actions of insulin. Binding of insulin to the insulin receptor (INSR) stimulates glucose uptake. Once the precursor signal peptide is removed, the insulin receptor precursor is post-translationally cleaved into 2 chains (alpha and beta) which are covalently linked. Insulin binding initiates phosphorylation of several intracellular substrates, including, insulin receptor substrates (IRS1, 2, 3, 4), SHC, GAB1, CBL and other signaling intermediates. Each of these phosphorylated proteins function as docking proteins for other signaling proteins which contain Src-homology-2 domains (SH2 domain) that specifically recognize different phosphotyrosines residues, including the p85 regulatory subunit of PI3K and SHP2.

Endothelial cells express three different vascular endothelial growth factor (VEGF) receptors, belonging to the family of receptor tyrosine kinases (RTKs). They are named VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1), VEGFR-3 (Flt-4). Their expression is almost exclusively restricted to endothelial cells, but VEGFR-1 can also be found on monocytes. All VEGF-receptors have seven immunoglobulin-like extracellular domains, a single transmembrane region and an intracellular split tyrosine kinase domain. VEGFR-2 has a lower affinity for VEGF than the Flt-1 receptor, but a higher signaling activity. Mitogenic activity in endothelial cells is mainly mediated by VEGFR-2 leading to their proliferation.
Differential splicing of the flt-1 gene leads to the formation of a secreted, soluble variant of VEGFR-1 (sVEGFR-1). No naturally occuring, secreted forms of VEGFR-2 have so far been reported. The binding of VEGF165 to VEGFR-2 is dependent on heparin.

The epidermal growth factor receptor (EGF R) subfamily of receptor tyrosine kinases comprises four members: EGF R (also known as HER1, ErbB1 or ErbB), ErbB2 (Neu, HER-2), ErbB3 (HER-3), and ErbB4 (HER-4). All family members are type I transmembrane glycoprotein that has an extracellular domain which contains two cysteine-rich domains separated by a spacer region that is involved in ligand-binding, and a cytoplasmic domain which has a membrane-proximal tyrosine kinase domain and a C-terminal tail with multiple tyrosine autophosphorylation sites. The human EGF R gene encodes a 1210 amino acid (aa) residue precursor with a 24 aa putative signal peptide, a 621 aa extracellular domain, a 23 aa transmembrane domain, and a 542 aa cytoplasmic domain. EGF R has been shown to bind a subset of the EGF family ligands, including EGF, amphiregulin, TGFa , betacellulin, epiregulin, heparin-binding EGF and neuregulin-2 in the absence of a co-receptor. Ligand binding induces EGF R homodimerization as well as heterdimerization with ErbB2, resulting in kinase activation, tyrosine phosphorylation and cell signaling. EGF R can also be recruited to form heterodimers with the ligand-activated ErbB3 or ErbB4. EGF R signaling has been shown to regulate multiple biological functions including cell proliferation, differentiation, motility and apoptosis. In addition, EGF R signaling has also been shown to play a role in carcinogenesis.

GDNF family receptor alpha-1 (GFRA1) belongs to the GDNF receptor family. GFRA1 is a glycosyl-phosphatidylinositol(GPI)-linked cell surface receptor for both Glial cell line-derived growth factor (GDNF), neurturin (NTN), and mediates activation of the RET tyrosine kinase receptor. The GFRA1 protein is a potent survival factor for central and peripheral neurons, and is vital for the development of kidneys and the enteric nervous system.

KLRC2 has a part as a receptor for the recognition of MHC class I HLA-E molecules by NK cells and some cytotoxic T-cells. The group, designated KLRC (NKG2) are expressed mainly in natural killer (NK) cells and encodes a family of transmembrane proteins categorized by a type II membrane orientation (extracellular C terminus) and the presence of a C-type lectin domain. The KLRC (NKG2) gene family is situated inside the NK complex, a region which holds a few C-type lectin genes specially expressed on NK cells. KLRC2 alternative splice variants are known but their full-length nature is yet to be determined.

Activin A Receptor Type 1 (ACVR1) is a member of TGF-beta serine/threonine kinase receptor family. ACVR1 forms a receptor complex contains2 type II and 2 type I transmembrane serine/threonine kinases. Type II receptors phosphorylate and activate type I receptors which autophosphorylate,bind and activate SMAD transcriptional regulators. ACVR1 takes part in left-right pattern formation during embryogenesis and is also essential in the BMP pathway which is responsible for the development and repair of the skeletal system.ACVR1 is linked to Fibrodysplasia Ossificans Progressiva which isknown for the formation of heterotopic bone throughout the body.

NCR2 is a member of the natural cytotoxicity receptor (NCR) family and holds 1 immunoglobulin-like (Ig-like) domain. NCR2 cooperates with TYROBP/DAP12 and is specifically expressed by activated NK cells and by in vitro cultured TCRg/d lymphoid cells. NCR2 is a cytotoxicity-activating receptor which induces the amplified efficiency of activated natural killer (NK) cells to mediate tumor cell lysis.

SSR is a glycosylated endoplasmic reticulum (ER) membrane receptor involved in protein translocation across the ER membrane. SSR is formed of 2 subunits, a 34-kD glycoprotein encoded by this gene and a 22-kD glycoprotein. SSR gene creates a number of mRNA species due to complex alternative polyadenylation. SSR is unique since it exploits arrays of polyA signal sequences which are mostly non-canonical.

RARRES2 is a secreted chemotactic protein that initiates chemotaxis through the ChemR23 G protein-coupled seven-transmembrane domain ligand. RARRES2 is upregulated by the synthetic retinoid tazarotene and found in a vast variety of tissues. RARRES2 acts as an adipokine, and is truncated on both termini from the proprotein. RARRES2 is structurally related to the cathelicidin precursors, cystatin C and kininogens. RARRES2 promotes calcium mobilization and chemotaxis of immature dendritic cells and macrophages. RARRES2 is secreted as a precursor of little biological activity, which requires proteolytic cleavage of its COOH-terminal domain to be exchangeed into a potent and highly specific agonist of ChemR23. RARRES2 signals via its receptor, ChemR23 (CMKLR1), as a positive regulator of adipocyte differentiation and metabolic function. The Chemerin receptor acts as a coreceptor for SIV and some primary HIV-1 strains. The Chemerin receptor has another ligand, called tazarotene-induced gene.

Thymic Stromal Lymphopoietin Receptor (TSLPR) is a member of the type I cytokine receptor family. TSLPR alongside the interleukin 7 receptor (IL7R) activate STAT3, STAT5, and JAK2 pathways, which is regulated processes such as cell proliferation and development of the hematopoietic system. Two transcript variants encoding dissimilar isoforms have been found for this gene. TSLPR is expressed in heart, skeletal muscle, kidney and adult and fetal liver.

Killer Cell Lectin-Like Receptor Subfamily C, Member 1 (KLRC1) is a part of the killer cell lectin-like receptor family. KLRC1 functions as a receptor for the detection of MHC class I HLA-E molecules by NK cells and some cytotoxic T-cells. KLRC1 is also connects with CD94 and is expressed on NK cells and some activated T cell.

RARRES2 is a secreted chemotactic protein that initiates chemotaxis through the ChemR23 G protein-coupled seven-transmembrane domain ligand. RARRES2 acts as an adipokine, and is truncated on both termini from the proprotein. RARRES2 is structurally related to the cathelicidin precursors, cystatin C and kininogens. RARRES2 promotes calcium mobilization and chemotaxis of immature dendritic cells and macrophages. RARRES2 is secreted as a precursor of little biological activity, which requires proteolytic cleavage of its COOH-terminal domain to be exchangeed into a potent and highly specific agonist of ChemR23. RARRES2 signals via its receptor, ChemR23 (CMKLR1), as a positive regulator of adipocyte differentiation and metabolic function. The Chemerin receptor acts as a coreceptor for SIV and some primary HIV-1 strains.

Retinoic Acid Receptor Responder 1 (RARRES1) is a part of the TIGs family. TIGs operate like tumor suppressor genes in human cancers and are greatly expressed in skin, hair follicles and endothelial cells plus in pancreas, spleen and intestine. TIGs are growth regulators which mediate the growth suppressive effects of retinoids.

KLRB1 has an inhibitory role on natural killer (NK) cells cytotoxicity which are lymphocytes who facilitate cytotoxicity and secrete cytokines subsequent to immune stimulation. Some genes of the C-type lectin superfamily, like the rodent NKRP1 family of glycoproteins, are expressed by NK cells and take part in NK cell function regulation. KLRB1 holds an extracellular domain with a few characteristic motifs of C-type lectins, a transmembrane domain, and a cytoplasmic domain. Due to its external C terminus KLRB1 is considered to be a type II membrane protein.