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RBBP9, restricts to the nucleus and cytoplasm, is a retinoblastoma binding protein which takes part in the regulation of cell proliferation and differentiation. RBBP9 cooperates with retinoblastoma (Rb) and offers cellular resistance to the growth-inhibitory effects of TGFbeta1, therefore enabling the cellular transformation process.

Retinoblastoma (RB) is an embryonic malignant neoplasm of retinal origin. It almost always presents in early childhood and is often bilateral. Spontaneous regression ('cure') occurs in some cases. Retinoblastoma acts as a regulator of other genes and forms a complex with adenovirus e1a and with sv40 large t antigen. Retinoblastoma acts as a tumor suppressor and modulats functionally certain cellular proteins with which t and e1a compete for pocket binding. Retinoblastoma is potent inhibitor of e2f-mediated trans-activation, recruits and targets histone methyltransferase suv39h1 leading to epigenetic transcriptional repression, inhibits the intrinsic kinase activity of taf1.

Retinoblastoma binding protein 4 (RBBP4) is a ubiquitously expressed nuclear protein which is a member of a highly conserved subfamily of WD-repeat proteins. RBBP4 is present in protein complexes involved in histone acetylation and chromatin assembly. In addition, RBBP4 is part of co-repressor complexes, which is a fundamental component of transcriptional silencing. RBBP4 is observed among several cellular proteins which bind directly to a retinoblastoma protein to regulate cell proliferation. RBBP4 also is a part of the Mi-2 complex which is implicated in chromatin remodeling and transcriptional repression connected with histone deacetylation.

Recoverin is a member of the recoverin family of neuronal calcium sensors. Recoverin is a heterogeneously acylated calcium-binding and intracellular signal transduction 23kDa protein in the photoreceptor cells of retina. Recoverin contains four EF-hands, of which two bind Ca. Ca-induced extrusion of the acyl group from a hydrophobic cleft in the protein drives the translocation of recoverin from solution to the disc membrane. Recoverin may prolong the termination of the phototransduction cascade in the retina by blocking the phosphorylation of photo-activated rhodopsin. Recoverin plays a key role in the inhibition of rhodopsin kinase, a molecule that regulates the phosphorylation of rhodopsin. This in due course controls the ability of the eye to adapt to, and recover from, exposure to the presence of light. Recoverin is a detectable serologic protein that is expressed in patients with cancer-associated retinopathy, a paraneoplastic syndrome.

Human Retinol Binding Protein, also known as RBP, is responsible for transporting and binding vitamin A. Human RBP has a binding site for 1 molecule of retinol and circulates in the plasma together with prealbumin as a protein complex. The prealbumin binding prevents greater glomerular losses of the human RBP. Only the retinol-free form of the RBP, which has no affinity for prealbumin, undergoes glomerular filtration unhindered as a result of its low Mw. Human RBP is re-absorbed by the tubular cells and catabolized there.

The retinoid X receptor (RXR) is a pleiotropic nuclear receptor transcription factor that interacts with a variety of nuclear receptor dimeric partner. RXR binds cognate response elements as a homodimer in the presence of its ligand, 9-cis retinoic acid, or as a heterodimer with other members of the nuclear hormone receptor superfamily including retinoic acid receptors (RAR), thyroid hormone receptors (TR), vitamin D receptors and peroxisome proliferators-activated receptors (PPAR). The RXR family includes three different isoforms; RXR a, b, g . Human RXR a gene is localized on 9q34.9 and encodes two major isoforms (RXR a1, RXR a2). The DNA binding domain of RXR (111-228aa) was purified by using conventional column chromatography techniques.

Recoverin is a member of the recoverin family of neuronal calcium sensors. Recoverin is a heterogeneously acylated calcium-binding and intracellular signal transduction 23kDa protein in the photoreceptor cells of retina. Recoverin contains four EF-hands, of which two bind Ca. Ca-induced extrusion of the acyl group from a hydrophobic cleft in the protein drives the translocation of recoverin from solution to the disc membrane. Recoverin may prolong the termination of the phototransduction cascade in the retina by blocking the phosphorylation of photo-activated rhodopsin. Recoverin plays a key role in the inhibition of rhodopsin kinase, a molecule that regulates the phosphorylation of rhodopsin. This in due course controls the ability of the eye to adapt to, and recover from, exposure to the presence of light. Recoverin is a detectable serologic protein that is expressed in patients with cancer-associated retinopathy, a paraneoplastic syndrome.

Retinoic acid receptor alpha (RAR) belongs to the large family of ligand responsive gene regulatory proteins that includes receptors for steroid and thyroid hormones. These proteins contain two highly conserved domains that are involved in determining their DNA and ligand-binding activities. There are three isotypes of RAR proteins: alpha, beta, and gamma. The RAR proteins are encoded by distinct genetic loci and possess distinct transcriptional properties. Typically, RAR-alpha represses target gene transcription in the absence of hormone, whereas RAR-beta and gamma fail to repress under these conditions. RARA is a receptor for retinoic acid that has profound effects on vertebrate development. Retinoic acid is a morphogen and is a powerful teratogen. RARA controls cell function by directly regulating gene expression.
Chromosomal aberrations involving RARA cause acute promyelocytic leukemia (APL).

Retinol Binding Protein-2 (RBP2) which is present in the small intestinal epithelium takes part in the uptake and intracellular metabolism of vitamin A. Vitamin A is a fat-soluble vitamin essential for growth, reproduction, differentiation of epithelial tissues, and vision. RBP2 moderates the supply of retinoic acid to the nuclei of endometrial cells throughout the menstrual cycle.

RBP1 is a member of the calycin superfamily and fatty-acid binding protein (FABP) family. RBP1 is the carrier protein which takes part in the transport of retinol (vitamin A alcohol) from the liver storage site to peripheral tissue. Additionally, RBP1 performs as a bridging molecule to recruit histone deacetylases (HDACs) which is a forceful regulator of gene expression. RBP1 is found in almost all the tissues with higher expression in pancreas, adrenal gland and pituitary gland, fetal liver and adult ovary.

RBP5 is a member of the Retinol-binding proteins family. Estimation of retinol-binding protein is used to determine visceral protein mass in nutritional studies related to health. RBP5 has a higher expression in the adult kidney and liver and to a lesser extent in the adult and fetal spleen, adult lymph nodes and appendix, and fetal liver and kidney. RBP5 expression is strongly decreased in hepatocellular carcinoma tissues.

Retinol Binding Protein-4 or RBP4, is the retinol currier protein in the plasma. RBP4 takes part on the conversion of retinol to the stable and soluble retinol complex in the plasma. RBP4 carries retinol from the liver tissue where its store to peripheral tissues. RBP-retinol complex has interactions with transthyretin in the plasma, thus prevents its loss by filtration in the kidney.

RBP7 is a member of a superfamily of small cytoplasmic proteins which interact with hydrophobic ligands. RBP7 is cytoplasmic protein which, like CRBP I and CRBP II, forms ?-barrel structures and participates in the intracellular transport of retinol. RBP7 is a newly identified cellular retinol carrier, which is expressed in the kidney, heart and transverse colon in humans.

Retinol binding protein 4(RBP4) belongs to the lipocalin family and is the specific carrier for retinol (vitamin A alcohol) in the blood. This protein was found to be expressed and secreted by adipose tissue, and was strongly associated with insulin resistance. It delivers retinol from the liver stores to the peripheral tissues. In plasma, the RBP-retinol complex interacts with transthyretin which prevents its loss by filtration through the kidney glomeruli.
RBP4 delivers retinol from the liver to the peripheral tissues. In plasma, the rbp-retinol complex interacts with transthyretin, this prevents its loss by filtration through the kidney glomeruli.

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.

Neuroblastoma suppressor of tumorigenicity 1 (NBL1) is a part of the evolutionarily conserved CAN (Cerberus and DAN) family of proteins, which contain a domain resembling the CTCK (C-terminal cystine knot-like) motif found in several signaling molecules. NBL1 is a is a tumor suppressor of neuroblastoma and takes part in preventing cells from entering the final stage (G1/S) of the transformation process. NBL1 is produced in small neurons of the dorsal root ganglion. The expression of NBL1 is triggered by MATH-1.

Retinol binding protein 4(RBP4) belongs to the lipocalin family and is the specific carrier for retinol (vitamin A alcohol) in the blood. This protein was found to be expressed and secreted by adipose tissue, and was strongly associated with insulin resistance. It delivers retinol from the liver stores to the peripheral tissues. In plasma, the RBP-retinol complex interacts with transthyretin which prevents its loss by filtration through the kidney glomeruli.
RBP4 delivers retinol from the liver to the peripheral tissues. In plasma, the rbp-retinol complex interacts with transthyretin, this prevents its loss by filtration through the kidney glomeruli.

Ras-related protein Ral-B (RALB) is a member of a subfamily of Ras-related GTPases. RALB is activated by a unique nucleotide exchange factor, Ral GDS, and deactivated by a distinct GTPase-activating protein. RALB has a role in the late stages of cytokinesis and is required for the abscission of the bridge joining the sister cells emerging from mitosis. In addition, RALB is required for suppression of apoptosis.

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.

NRAS binds GDP/GTP and has intrinsic GTPase activity. NRAS is a membrane protein that shuttles between the Golgi apparatus and the plasma membrane. This transport is regulated through palmitoylation and depalmitoylation by the ZDHHC9-GOLGA7 complex. NRAS is activated to a GTP-bound form by a GTPase activating protein and inactivated to a GDP-bound form by a guanine nucleotide-exchange factor. Defects in this NRAS gene result in juvenile myelomonocytic leukemia.

RLBP1 is a 36-kD water-soluble protein that transports 11-cis-retinal or 11-cis-retinaldehyde as physiologic ligands. RLBP1 is a functional element of the visual cycle. RLBP1 gene mutations cause retinitis punctata albescens, severe rod-cone dystrophy and Bothnia dystrophy (nonsyndromic autosomal recessive retinitis pigmentosa).

RHOC is a small signaling G protein/GTPase which is part of the Rac subfamily of the family Rho family of GTPases. RHOC rotats between inactive GDP-bound and active GTP-bound states and has a role as a molecular switch in signal transduction cascades. RHOC promotes reorganization of the actin cytoskeleton and regulates cell shape, attachment, and motility.

RHEB is part of the Ras & GTPase superfamily that was originally identified as an immediate-early gene in brain but is also widely expressed in other tissues. RHEB encodes a lipid-anchored, cell membrane protein with five repeats of the RAS-related GTP-binding region. RHEB is necessary in regulation of growth and cell cycle progression due to its role in the TOR/S6K signaling pathway. RHEB has GTPase activity and shuttles between a GDP-bound form and a GTP-bound form, and farnesylation of the protein is required for this activity. RHEB induces oncogenic transformation. RHEB overexpression accelerates lymphomagenesis and is associated with prostate cancer. RHEB can cytopathologically distinguish between fibroadenoma from malignant breast carcinomas which is considered as a secondary diagnostic tool. RHEB has a central role in the regulation of the Ras/B-Raf/C-Raf/MEK signaling network.