Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Advanced glycosylation endproducts (AGEs) are derived from the nonenzymatic addition of glucose to proteins. AGEs have been found to accumulate on tissue proteins in patients with diabetes, and their accumulation is thought to play a role in the development of diabetic complications. The finding that macrophages and endothelial cells contain AGE-specific receptors led us to examine whether mesangial cells (MCs) also possess a mechanism for recognizing and processing AGEs. Membrane extracts isolated from rat and human MCs were found to bind AGE-bovine serum albumin (BSA) in a saturable fashion, with a binding affinity of 2.0 +/- 0.4 x 10(6) M-1 (500 nM). The binding was specific for the AGE adduct, since AGE-modified collagen I and ribonuclease both competitively inhibited 125I-AGE-BSA binding to MC membranes, while the unmodified proteins did not compete. Binding of AGE proteins was followed by slow internalization and degradation of the ligand. Ligand blotting of MC membrane extracts demonstrated three distinct AGE-binding membrane proteins of 50, 40, and 30 kD. Growth of MCs on various AGE-modified matrix proteins resulted in alterations in MC function, as demonstrated by enhanced production of fibronectin and decreased proliferation. These results point to the potential role that the interaction of AGE-modified proteins with MCs may play in vivo in promoting diabetic kidney disease.
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PMID:Human and rat mesangial cell receptors for glucose-modified proteins: potential role in kidney tissue remodelling and diabetic nephropathy. 165 49

We studied expression of laminin, fibronectin, and Type IV collagen in the testis by means of immunofluorescence and immunoblot analysis and also examined gene expression of fibronectin using the ribonuclease protection assay. By immunofluorescence on sections from 20-day-old rats, laminin, fibronectin, and Type IV collagen were found in the basement membrane of the seminiferous tubules and in the interstitial regions of the testis. No localization of any extracellular matrix components was found inside the sectioned cells. However, when Sertoli cells were cultured on glass coverslips, laminin and Type IV collagen were both found inside the cells, suggesting new synthesis. In cultured peritubular cells, Type IV collagen, laminin, and fibronectin were found within the cells. When examined by immunoblot analysis, freshly isolated Sertoli and peritubular cells from 20-day-old rats did not demonstrate production of laminin or fibronectin. After 5 days in culture, peritubular cells produced both laminin and fibronectin, whereas cultured Sertoli cells produced only laminin. In contrast, freshly isolated and cultured Sertoli and peritubular cells all produced Type IV collagen. Moreover, the ribonuclease protection assay indicated that the bulk of fibronectin gene expression occurs within the first 10 days of postnatal development, with lower maintenance levels occurring thereafter. These results indicate that in the testis the highest levels of expression of laminin and fibronectin occur during development and in primary cell culture, whereas expression of Type IV collagen is higher at later stages.
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PMID:Differential expression of extracellular matrix components in rat Sertoli cells. 170 45

We have isolated overlapping cDNA clones from human and hamster libraries which comprise the entire coding sequences for the prepro-alpha 1(V) collagen chains of both species. The translated polypeptide has a signal peptide of 36 amino acids, a central triple helical domain of 338 uninterrupted Gly-X-Y triplets, and 266 amino acids which comprise the C-telopeptide and propeptide. The N-propeptide and telopeptide are comprised of 522 residues in humans and 524 residues in hamsters. The cDNA-derived pro-alpha 1(V) amino acid sequences exhibit a variety of structural features characteristic of fibrillar collagens. Pro-alpha 1(V) is found to be unique among fibrillar collagen chains, however, in lacking potential cross-linking lysyl residues in either telopeptide, and in possessing potential N-asparaginyl-linked carbohydrate attachment sites in its N-propeptide. Of particular interest is the strong homology found between the pro-alpha 1(V) and pro-alpha 1(XI) collagen chains in most domains, with the notable exception of a subdomain in the globular region of the N-propeptide. RNase protection analysis of RNA with a variety of pro-alpha 1(V) cDNA-derived riboprobes indicates a broad distribution of expression of the pro-alpha 1(V) chain in tissues and suggests that transcripts encoding the pro-alpha 1(V) chain and the putative pro-alpha 1'(V) chain are not products of the same gene.
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PMID:The pro-alpha 1(V) collagen chain. Complete primary structure, distribution of expression, and comparison with the pro-alpha 1(XI) collagen chain. 172 13

A fluorescent compound has been detected in proteins browned during Maillard reactions with glucose in vitro and shown to be identical to pentosidine, a pentose-derived fluorescent cross-link formed between arginine and lysine residues in collagen (Sell, D. R., and Monnier, V. M. (1989) J. Biol. Chem. 264, 21597-21602). Pentosidine was the major fluorophore formed during nonenzymatic browning of ribonuclease and lysozyme by glucose, but accounted for less than 1% of non-disulfide cross-links in protein dimers formed during the reaction. Pentosidine was formed in greatest yields in reactions of pentoses with lysine and arginine in model systems but was also formed from glucose, fructose, ascorbate, Amadori compounds, 3-deoxyglucosone, and other sugars. Pentosidine was not formed from peroxidized polyunsaturated fatty acids or malondialdehyde. Its formation from carbohydrates was inhibited under nitrogen or anaerobic conditions and by aminoguanidine, an inhibitor of advanced glycation and browning reactions. Pentosidine was detected in human lens proteins, where its concentration increased gradually with age, but it did not exceed trace concentrations (less than or equal to 5 mumol/mol lysine), even in the 80-year-old lens. Although its precise carbohydrate source in vivo is uncertain and it is present in only trace concentrations in tissue proteins, pentosidine appears to be a useful biomarker for assessing cumulative damage to proteins by nonenzymatic browning reactions with carbohydrates.
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PMID:Formation of pentosidine during nonenzymatic browning of proteins by glucose. Identification of glucose and other carbohydrates as possible precursors of pentosidine in vivo. 190 67

Mice transgenic for growth hormone (GH) develop progressive glomerulosclerosis. The compositions of kidney extracellular matrix (ECM) and ECM mRNA were examined. The glomerulosclerotic areas in GH mice contained types I and IV collagen, laminin, and basement membrane heparan sulfate proteoglycan (HSPG), which increased with age. The type IV collagen, laminin B2, and HSPG mRNA levels in GH mice, measured by a solution hybridization RNase protection assay, were increased over normal littermates. These findings suggest that the accumulation of ECM components in the glomeruli of GH mice is regulated at the transcriptional level and that glomerulosclerosis is, in part, due to the excess production of ECM rather than simply a reduction in its turnover. The glomerular lesions in GH mice resemble diabetic nephropathy and may allow further dissection of the molecular basis of certain forms of glomerulosclerosis.
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PMID:Glomerulosclerosis in mice transgenic for growth hormone. Increased mesangial extracellular matrix is correlated with kidney mRNA levels. 202 27

Following subcutaneous inoculation of newborn Wistar-Furth rats with human adenovirus type 9 (Ad9), 16 of 16 female and 0 of 11 male rats developed mammary tumors. Tumor-positive animals usually developed tumors in multiple glands. Histopathological analyses indicated that three general categories of tumor could be identified. Mammary fibroadenomas were the most common tumor type encountered, but phyllodeslike tumors and solid sarcomas were also frequently found. In situ hybridization and immunohistochemical techniques established that benign fibroadenomas were derived from mammary fibroblasts (collagen type I- and vimentin-positive cells) and that malignant tumors were derived from myoepithelial cells (collagen type IV-, vimentin-, and muscle-specific actin-positive cells). The fact that mammary tumors were limited to female rats suggested that female hormones are essential for tumor growth and development. In this regard, ovariectomy of Ad9-infected female rats prevented tumor development, while subsequent diethylstilbestrol (DES) treatment elicited tumor formation. In addition, Ad9-infected and castrated male rats which received DES also developed mammary tumors. Established male mammary tumors regressed when DES treatment was stopped and reappeared after DES treatment was resumed. Together, these results indicate that estrogen is required for both initiation and maintenance of Ad9-induced mammary tumors. Southern blot analysis of high-molecular-weight tumor DNA showed that mammary tumor cells contained single or multiple integrated copies of the entire Ad9 genome. RNase protection experiments established that estrogen receptor as well as Ad9 E1a and E4 mRNAs were expressed in mammary tumors, but Ad9 E3 and, surprisingly, E1b mRNAs were not expressed at detectable levels.
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PMID:Human adenovirus type 9-induced rat mammary tumors. 203 70

Silicosis was produced experimentally in rats by single intratracheal injections of various doses of SiO2 dust. The weight of the lungs as well as the contents of total nitrogen, collagen, nucleic acids (especially RNA), and lipids increased in accordance with the dose and the time interval. Fibrogenic stimulation in vitro was shown by the supernatant of the homogenized lung in the incorporation of proline into incubated granulation tissue or lung fibroblasts. The fibrogenic factor-activity depended more on the time interval after the injection than on the SiO2 dose. Electrophoresis of the soluble proteins in the silicotic rat lungs showed a protein of 16,000 Da, which was dependent on the time interval following SiO2 administration as well as on the dose itself, and which originated from macrophages. This protein was purified by repeated gel-filtration chromatography. It stimulated collagen synthesis in granulation-tissue cells at a concentration of about 10(-10) M in a dose-dependent way. It was acidic by amino acid composition but differed from calmodulin which also increased collagen synthesis in granulation-tissue cells in vitro. The ability of non-fractionated macrophage preparations to stimulate the incorporation of proline into collagen correlated inversely with the gross alkaline RNase activity.
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PMID:Isolation of silica-dependent protein from rat lung with special reference to development of fibrosis. 254 36

The first intron of the human collagen alpha 1(I) gene contains several positively and negatively acting elements. We have studied the transcription of collagen-human growth hormone fusion genes, containing deletions and rearrangements of collagen intronic sequences, by transient transfection of chick tendon fibroblasts and NIH 3T3 cells. In chick tendon fibroblasts, but not in 3T3 cells, inversion of intronic sequences containing a previously studied 274-base-pair segment, A274, resulted in markedly reduced human growth hormone mRNA levels as determined by an RNase protection assay. This inhibitory effect was largely alleviated when deletions were introduced in the collagen promoter of plasmids containing negatively oriented intronic sequences. Evidence for interaction of the promoter with the intronic segment, A274, was obtained by gel mobility shift assays. We suggest that promoter-intron interactions, mediated by DNA-binding proteins, regulate collagen gene transcription. Inversion of intronic segments containing critical interactive elements might then lead to an altered geometry and reduced activity of a transcriptional complex in those cells with sufficiently high levels of appropriate transcription factors. We further suggest that the deleted promoter segment plays a key role in directing DNA interactions involved in transcriptional control.
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PMID:Interactions between the promoter and first intron are involved in transcriptional control of alpha 1(I) collagen gene expression. 321 Nov 30

Registration of the three procollagen alpha chains and assembly of the triple-helical procollagen molecules takes place in the rough endoplasmic reticulum, but the exact location and timing of assembly is not known. As part of a study of the mechanism of molecular assembly, intact collagen-producing polyribosomes from embryonic chicken tendon fibroblasts have been examined by the techniques of rotary shadowing and electron microscopy. Intact mRNA strands corresponding in length to approximately 4500 bases and complete procollagen alpha (I) chains have been observed. The mRNA strands are comprised of two mRNA chains. The ribosomes are present in pairs separated along the duplex strand by about 100 nm. The intact polysome is asymmetric; two duplex strands join, and large ribosome aggregates appear. These aggregates are dispersed by collagenase digestion, leaving separate duplex strands with ribosome pairs intact. Ribonuclease digestion yields mixtures of monosomes and ribosome aggregates. Sequential ribonuclease and collagenase digestions yield only monosomes. We propose that each ribosome reads one mRNA chain, so that each pair is thus translating two chains in synchrony. Thus, the complex morphology of the collagen-producing polyribosomes suggests that the organization of a single molecule begins by the organization of the mRNA chains themselves.
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PMID:Supramolecular assemblies of mRNA direct the coordinated synthesis of type I procollagen chains. 385 43

A review was made on the recent advances in the study on the pathogenesis of silica-induced pulmonary fibrosis. Alveolar macrophages which ingest silica particles liberate a fibrogenic factor, which stimulates the production of collagen of cultured fibroblasts. Silica deposited in the alveoli augments the demand of macrophages, the supply of which is maintained by monocytes recruited from the bone marrow. Attempts to demonstrate in vitro the presence of a fibrogenic factor in the supernatant of macrophages have been made in many laboratories, and an in vivo model utilizing diffusion chambers implanted in mice has been used by some investigators. A fibrogenic factor has been isolated and purified from the medium of silica-treated macrophages. Recent advances in immunological studies have demonstrated that silica stimulates macrophages to release monokines such as interleukin 1 (IL-1) and that IL-1 has chemical properties identical to the fibrogenic factor, which enhances the level of collagen production by modulating the proliferation of fibroblasts. Silica inhibits the suppressive effects of macrophages on fibroblasts. The increased protein synthesis in the fibroblasts is due partly to increase in mRNA. Collagen synthesis is stimulated not only by the fibrogenic factor released from silica-treated macrophages but also by the inhibition of macrophage ribonuclease activity. Information on the number of cells, collagen content and protease activity in the lung as well as in the bronchopulmonary lavage fluid has provided us a better understanding of the mechanisms involved in silica-induced pulmonary fibrosis.
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PMID:[Recent advances in the study of the mechanisms of silica-induced pulmonary fibrosis]. 391 86


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