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Results for “Retinol-Binding Proteins, Cellular”

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At least 19 recordsLinked to original sources
PubMed1979

Demonstration of a novel cellular retinol-binding protein, F-type, in hepatocellular carcinoma.

Vitamin A level and the cytosol-binding proteins specific for vitamin A ere studied in human tumor and its surrounding tissue. The tissues examined were 10 hepatocellular carcinomas which were surgically removed, 4 other malignant tumors (2 metastatic liver cancer and one each of gastric cancer and glioma), and 3 human fetal livers. Compared with surrounding tissues, considerable decrease of vitamin A content was observed in the hepatocellular carcinoma suggesting local deficient state of the vitamin. In addition to cellular retinol-binding protein (CRBP) and retinoic acid-binding protein (CRABP), a new molecular species having affinity for both retinol and retinoic acid was detected in the cytosols obtained from hepatocellular carcinoma as well as glioma by means of gel filtration on Sephadex G-75. With regard to ligand specificity, the protein was found to be similar to cellular retinol-binding protein, F-type or CRBP(F) which was originally recognized in the fish eye cytosol. Since the protein was also demonstrated in human fetal liver, CRBP(F) is considered to be an oncofetal protein in nature. The present study further revealed that CRBP(F) was detected in 80% of hepatocellular carcinoma (whereas plasma alpha-fetoprotein was significantly elevated only in 50%), and hepatocellular carcinoma contained CRBP(F) in a larger amount than CRABP.

Adult↗
PubMed1979

Cellular retinol-binding protein allows specific interaction of retinol with the nucleus in vitro.

Purified cellular retinol-binding protein (CRBP), a potential mediator of vitamin A action, was found to enable retinol to bind in a specific manner to isolated nuclei from livers of vitamin A deficient rats. Binding was followed after complexing [3H]retinol with CRBP. The binding was specific, saturable, and temperature dependent. CRBP charged with unlabeled retinol or CRBP without retinol diminished binding of radioactivity whereas free retinol did not. No specific binding sites could be detected for free retinol. Purified cellular retinoic acid binding protein (CRABI) complexed with retinoic acid did not diminish the amount of retinol bound to nuclei. Approximately 3 x 10(5) specific binding sites per nucleus could be detected. Fewer binding sites were found in nuclei isolated from livers of control (chow-fed) rats and also from livers of vitamin A-deficient rats 2 hr after refeeding with retinylacetate.

Animals↗
PubMed1978

Cellular retinol-binding protein from rat liver. Purification and characterization.

Cellular retinol-binding protein has been purified to homogeneity from rat liver. The procedures utilized in the purification included acid precipitation, gel filtration on Sephadex G-75 and G-50, and chromatography on DEAE-cellulose. The binding protein was purified approximately 3,500-fold, based on total soluble liver protein. The protein is a single polypeptide chain with a molecular weight of 14,600 based on information obtained by the techniques of sedimentation equilibrium analysis, gel filtration, and sodium dodecyl sulfate-polyacrylamide electrophoresis. The protein binds retinol with high affinity; the appparent dissociation constant was determined by fluorometric titration to be 1.6 X 10(-8) M. Retinol bound to the protein has an absorption spectrum (lambdamax, 350 nm) considerably altered from the spectrum of retinol in ethanol (lambdamax, 325 nm).

Animals↗
PubMed1979

Demonstration of a novel molecular species in chick embryo brain: cellular retinol-binding protein, F-type.

By sucrose density gradient sedimentation analysis, a cytosol component of small molecular size which bound 3H-retinoic acid was detected in the chick embryo brain, exhibiting a peak on day 14 (7 days before hatching). In general, cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP) have been distinguished by showing binding specificity for retinol or retinoic acid, respectively. However, the component found in embryo brain cytosol exhibited binding affinity for both retinol and retinoic acid, being similar in less ligand-specificity to CRBP (F) which was originally recognized in fish eye cytosol. Moreover, the component also showed a lack of binding affinity for prealbumin (PA), excluding the possibility that chicken plasma RBP was contaminated in the cytosol. These findings strongly suggest that a distinct molecular species of cellular binding protein for vitamin A exists in the brain cytosol of a developing chick embryo.

Animals↗
PubMed1975

Cellular retinol-binding protein.

1. A protein which binds retinol in vitro with high affinity and specificity was detected by sucrose gradient centrifugation or by gel filtration after preincubating rat tissue cytosols with all-trans-[3H]retinol. This protein sediments in the 2 S region of sucrose gradients. Molecular size determination by gel filtration indicates a molecular weight of 16 000. 2. Competition studies revealed that only all-trans-retinol, not retinal or retinoic acid, competes for binding. The binding of radioactive retinol is reversible. 3. This protein was detected in cytosols of rat liver, lung, spleen, brain, testis, ovaries, uterus and intestinal mucosa whereas heart or gastrocnemius muscle seem to lack this protein. 4. The cellular retinol binding protein was found in fetuses as early as day 12 of the gestation period and possessed the same specificity for the ligand as the one in adult tissues. 5. This binding component was not detected in cytosols prepared from Novikoff hepatoma, ascites hepatoma AS-30D, mouse Ehrlich ascites tumor and mouse pituitary tumor cell line AtT 20. 6. The cellular retinol binding protein seems to be different from that described to be present in the serum as suggested by difference in size and by the inability of the antisera against the serum retinol binding protein to remove the cellular binding protein from the cytosol preparations.

Amniotic Fluid↗
PubMed1977

Localization of cellular retinal-binding protein in bovine retina and retinal pigment epithelium, with a consideration of the pigment epithelium isolation technique.

Bovine RPE was isolated by commonly used brushout procedures and analyzed by light and electron microscopy. The preparation was found to consist almost entirely of cells with retained organelles (mitochondria, pigment, and other granules) but with broken surface membranes and extracted cytoplasm. In keeping with this, the wash obtained by sedimenting these broken cells contained approximately 97 percent of the cellular retinol-binding protein present in the suspension. Cellular retinoic acid-binding protein, present in bovine retinal extracts, was found in low amounts in the wash from RPE. The cellular retinol-binding protein present in the RPE wash was of high specific activity and similar in properties to that obtained from bovine retina. Supernatant obtained from sonicated rod outer segments contained approximately 10 percent of the retinol-binding protein of the retina. No retinoic acid-binding protein was found. The relatively large amount of cellular retinol-binding protein present in the RPE (more than is found in the retina) is consistent with a functional role of this protein in uptake and transport of retinol by the RPE.

Animals↗
PubMed1979

Immunochemical comparison of vitamin A binding proteins of rat.

Specific antibodies against cellular retinol-binding protein (CRBP), raised in rabbit, were detected by sucrose gradient centrifugation and gel filtration using tritium-labeled CRBP, prepared by reductive methylation. By means of radioimmunoassay, pure CRBP from liver and testis as well as CRBP present in a crude extract of liver were compared. All preparations showed identical immunoreactivity, suggesting CRBP is not tissue-specific. In contrast, two other vitamin A-binding proteins, cellular retinoic acid-binding protein, and serum retinol-binding protein, showed no cross-reaction in the radioimmunoassay.

Animals↗
PubMed1979

Cellular binding proteins for vitamin A in the normal human uterine cervix and in dysplasias.

Cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein are present in the cytosol of normal human uterine cervical tissues, as detected by ultracentrifugation analysis. Both binding proteins have characteristically high specificity for their respective ligands. In sucrose gradients, both proteins sediment in the 2S region and are of similar molecular weight (M.W. approximately 14,000). In blind analyses of cervical biopsies, obtained under direct vision by colposcopy of normal women (control) or from patients histopathologically diagnosed to have dysplasias or carcinoma in situ (study group), CRBP was not detectable by sucrose gradient analysis in 78.8% of the 33 abnormal biopsies, compared to 23.5% of the 34 controls. This difference was statistically significant (p less than 0.005). In biopsies in which CRBP was detected, the mean levels were 2.76 and 0.72 pmol/mg protein in the cytosol for the control and study groups, respectively. In some subjects from each group, cellular retinoic acid-binding protein but not CRBP was detected in the biopsied tissue. The presence and role of these binding proteins in vitamin A metabolism, epithelial maturation and differentiation in cervical dysplasias, and in situ lesions remain to be investigated.

Adolescent↗
PubMed1977

Retinoic acid-binding protein in experimental tumors and in tissues with metastatic tumor foci.

Screening for retinoic acid-binding protein (RABP) in experimental tumors revealed the presence of this protein in three mammary tumors, two metastatic colon tumors, B16 melanoma. Lewis lung carcinoma, Ridgway osteogenic sarcoma, and keratoacanthoma. RABP was below the limits of detection in two weakly metastatic colon tumors and in Sarcoma 180. After s.c. implantation of RABP-containing tumors into mice, this protein could be traced in the lungs due to pulmonary metastasis. Following implantation of Lewis lung tumors, RABP was detected in the lung on the 6th day. On the 15th day after implantation, RABP was present in lung and brain, but not in other tissues where this protein was normally lacking. In primary cultures of Lewis lung carcinoma, the lower limit for detection of RABP by sucrose gradient sedimentation technique corresponded to 0.12 mg protein that was extractable from 3 X 10(5) cells. Both chick embryo skin and rabbit ear skin extracts contained RABP; the level of cellular retinol-binding protein was high in chick embryo skin but only marginal in rabbit ear. The amounts of these proteins on chick embryo skin and rabbit ear skin correlate with the biological potency of retinol and retinoic acid, as observed by others.

Animals↗
PubMed1979

Cellular retinol- and retinoic acid-binding proteins in vitamin A action.

Two intracellular proteins that bind compounds with vitamin A activity have been discovered in animal tissues. One, called cellular retinol-binding protein (CRBP), binds retinol with high specificity and affinity, but not retinal or retinoic acid. The other protein, called cellular retinoic acid-binding protein (CRABP), has high affinity for retinoic acid but does not bind retinol or retinal. CRBP is different from the well-known serum retinol binding protein. The proteins are present in many fetal tissues, whereas their tissue distribution in the adult rat differs. The levels of these proteins change differently during perinatal development, suggesting that they are regulated in a nonsynchronous manner. Some malignant tumors contain these proteins. The presence of these proteins could be an indication of whether the tumor might be inhibited by or might require vitamin A for growth. It appears that the cell nucleus is a target for retinol action, as CRBP allows specific interaction of retinol with the nucleus, showing the presence of specific binding sites for retinol. The number of these sites is dependent on the vitamin A status of the animal.

Animals↗
PubMed1977

Occurrence of 11-cis-retinal-binding protein restricted to the retina.

A binding protein for retinal (vitamin A aldehyde), the 11-cis-retinal-binding protein, was present in the soluble protein fraction of rat retina but was absent from brain, lung, heart, skeletal muscle, liver, kidney, spleen, small intestine, and testes. The binding protein was also found in human retina but not human liver. The binding protein for retinal from human retina did not bind retinol and was larger than, and readily separable from, the cellular retinol-binding protein which did not bind retinal. It would appear that the occurrence of a soluble binding protein for retinal, unlike the more widely distributed binding proteins for retinol and retinoic acid, may be unique to the retina.

Animals↗
PubMed1978

Cellular binding proteins for vitamin A in colorectal adenocarcinoma of rat.

Rat colorectal mucosa was examined during the course of carcinogenesis, induced by chronic administration of 1,2-dimethylhydrazine (DMH), for the presence and amount of cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein. These two binding proteins are implicated in the action of vitamin A in normal and neoplastic tissue. Induced adenocarcinomas were found to contain low levels of cellular retinoic acid-binding protein (10 pmol/g), similar to the levels found in adjacent mucosa of the same animal and also in colorectal mucosa from normal rats or rats chronically treated with DMH. However, the adenocarcinomas had high levels of CRBP (300 to 500 pmol/g), and these levels were dramatically higher than levels of CRBP in adjacent mucosa of the same animal (40 to 100 pmol/g), colorectal mucosa from normal rats (20 pmol/g), or colorectal mucosa from rats chronically treated with DMH (22 to 25 pmol/g). Consequently, the increase in CRBP occurred only with tumor appearance and not with the general hyperplasia of the crypts caused by DMH administration. The CRBP of the tumor was associated with endogenous retinol (77 to 100% saturation) and was similar to, if not identical with, CRBP of normal tissue, as judged by fluorescence spectra, sedimentation behavior, and elution position on Sephadex G-75.

Adenocarcinoma↗
PubMed1979

Intracellular binding proteins for retinol and retinoic acid: comparison with each other and with serum retinol-binding protein.

Soluble proteins with binding specificity for either retinol or retinoic acid were isolated from rat testis cytosol. The characteristics of the purified cytosolic protein were compared both with each other, and directly with those of serum retinol-binding protein (RBP). Substantial similarities were observed between the two cytosol retinoid binding proteins, as well as clear differences between each of these proteins and serum RBP. The intracellular binding proteins differed from serum RBP with regard to molecular weight, immuno-reactivity, binding affinity for serum prealbumin, and ultraviolet and fluorescence spectral characteristics. The ultraviolet absorption spectrums of the cytosol binding protein for retinol (CRBP) and of the cytosol binding protein for retinoic acid (CRABP) were almost identical despite differences in the nature of the ligands bound by these two proteins.

Animals↗
PubMed1978

Cellular retinoic acid-binding protein from rat testis. Purification and characterization.

Cellular retinoic acid-binding protein has been purified to homogeneity from rat testes. The procedures utilized in the purification included acid precipitation, gel filtration, and chromatography on DEAE-cellulose. The binding protein was purified approximately 12,000-fold, based on total soluble testicular protein. The protein is a single polypeptide chain with a molecular weight of 14,600, determined by information from gel filtration and sodium dodecyl sulfate-polyacrylamide electrophoresis. The protein binds retinoic acid with high affinity; the apparent dissociation constant was determined by fluorometric titration to be 4.2 X 10(-9) M.

Animals↗