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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasma membrane from the brush border isolated from the tegument of Hymenolepis diminuta contains membrane-bound ribonuclease (RNase) and alkaline phosphatase activities. RNase (yeast RNA substrate), alkaline phosphatase (p-nitrophenyl phosphate substrate), and additional membrane proteins were solubilized by sonication or treatment with the detergents dodecyl trimethylammonium bromide, beta-octyl-D-glucopyranoside, sodium dodecyl sulfate (SDS), or ZwittergentTM 3-12 (N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate). At optimal conditions, greater than 90% of both enzymes and total protein were solubilized by the latter two detergents, whereas beta-octyl-D-glucopyranoside, dodecyl trimethylammonium bromide, and sonication were only partially effective. Nonionic detergents did not solubilize the membrane effectively.
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PMID:Solubilization of membrane-bound ribonuclease (RNAse) and alkaline phosphatase from the isolated brush border of Hymenolepis diminuta (Cestoda). 739 87

Transforming growth factor beta 1 (TGF-beta 1), a product of marrow stromal cells, inhibits the proliferation and differentiation of hematopoietic progenitor cells within the hematopoietic microenvironment. Steel factor (SF), also a product of marrow stromal cells, is an essential positive regulator of hematopoiesis in vivo. TGF-beta 1 has been shown to repress human and murine leukemic cell and murine lin- bone marrow mononuclear cell expression of the receptor for SF (c-kit). We speculated that TGF-beta 1 might exert its inhibitory effect on hematopoiesis in part by decreasing SF/c-kit interactions. Therefore, we tested the hypothesis that TGF-beta 1 inhibits both stromal cell expression of SF and hematopoietic progenitor cell expression of c-kit. We measured stromal cell expression of SF protein and hematopoietic progenitor cell expression of membrane-bound c-kit before and after exposure to recombinant human TGF-beta 1. Both stromal cell expression of SF protein and hematopoietic progenitor cell expression of c-kit protein were inhibited 50% to 80% by TGF-beta 1. Using Northern blot and ribonuclease protection assays, we determined that TGF-beta 1 repressed stromal cell SF mRNA, but did not alter SF transcript stability. TGF-beta 1 was also found to repress c-kit mRNA in human leukemic myeloblasts as well as in normal lin- hematopoietic progenitor cells. In contrast with its effect on SF mRNA, TGF-beta 1 accelerated the degradation of c-kit mRNA. We conclude that TGF-beta 1 inhibits stromal cell production of SF by repression of SF gene transcription and represses hematopoietic progenitor cell expression of c-kit by decreasing the stability of c-kit transcripts. Taking into account the importance of SF and c-kit in maintaining steady-state hematopoiesis in vivo, the dual effect of TGF-beta 1 on both SF and c-kit gene expression is likely to be one of the major mechanisms by which TGF-beta 1 inhibits hematopoiesis in vivo.
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PMID:Transforming growth factor beta 1 inhibits expression of the gene products for steel factor and its receptor (c-kit). 753 88

The mannose 6-phosphate (Man6P)-dependent pathway for routing lysosomal enzymes was characterized in the hepatopancreas of the estuary crab Chasmagnatus granulata: (a) an acid alpha-L-fucosidase was purified to homogeneity from the above-mentioned organ and was shown to contain mannose-linked phosphate residues; (b) high-mannose-type oligosaccharides isolated from a protein fraction enriched in acid hydrolases were found to contain acid-labile N-acetylglucosamine (GlcNAc) residues; (c) a membrane-bound UDP-GlcNAc:lysosomal enzyme GlcNAc-1-phosphotransferase was detected that phosphorylated the estuary-crab alpha-L-fucosidase and bovine uteroferrin but not bovine pancreas ribonuclease B; (d) a GlcNAc-1-phosphodiester alpha-N-acetylglucosaminidase that released GlcNAc units from GlcNAc alpha 1-P6Man alpha 1-methyl was detected in microsomal membranes of the hepatopancreas; (e) two detergent-solubilized microsomal proteins having molecular masses of 205 and 215 kDa that were retained by a Man6P-rich mannan-Sepharose column, from where they were eluted with Man6P but not with glucose 6-phosphate, were recognized by antisera raised against bovine large (215 kDa) and small (46 kDa) Man6P receptors. This is the first description of all the components of the Man6P-dependent mechanism for routing lysosomal enzymes in an invertebrate.
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PMID:Characterization of the mannose 6-phosphate-dependent pathway of lysosomal enzyme routing in an invertebrate. 765 99

The tyrosine kinase receptor c-kit and its ligand KL are required for postnatal development of germ cells, in addition to their role in primordial germ cells. To clarify their function, a detailed examination of the pattern of expression of KL in postnatal gonads was undertaken. In ovaries, the expression of KL as seen by RNA blot analysis and by RNase protection assays is relatively high at birth (P0), low from P5 to P8, and high from P12 onward. KL expression is relatively high in testes of all ages. The forms of KL RNA present in the testes suggest that from P5 onward the membrane-bound form of KL predominates, while in the ovary significant amounts of both forms are present. As observed by in situ hybridization and immunohistochemistry, in the newborn ovary KL is highly expressed in central cords whose cells contribute to the formation of central growing follicles. Expression is low in follicle cells of small growing follicles and increases to high levels in three-layered follicles during late oocyte growth. Large amounts of the ligand are found within growing oocytes. After oocyte growth ceases, expression continues only in the outer layers of multilayered follicles. In the testis, from P0 through P9, KL expression is distinct in Sertoli cells, but not in germ cells. Thereafter, the intensity of KL expression declines as the number of spermatogenic cells increases within the tubules. KL in Sertoli cells appears to be concentrated basally at the stage of the cycle of the seminiferous epithelium when it is known to interact with differentiating type A spermatogonia. These data are consistent with a role for KL in oocyte growth and in facilitating proliferation and/or differentiation of type A spermatogonia.
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PMID:The expression pattern of the c-kit ligand in gonads of mice supports a role for the c-kit receptor in oocyte growth and in proliferation of spermatogonia. 768 86

Steel factor (SF), the ligand for c-kit, is an essential regulator of normal hematopoiesis, melanogenesis, gametogenesis, and mast-cell growth and development. Hematopoietic stromal cells are important sources of SF, because inactivation of SF in mice results in defects in the support function of hematopoietic stromal cells. To identify specific cells that produce, and factors that govern the expression of the different isoforms of SF in human hematopoiesis, we quantified levels of SF mRNA and membrane-bound protein in human stromal cells before and after exposure to recombinant human interleukin (IL)-1 alpha, a cytokine known to induce the expression of a variety of hematopoietic growth factors. In addition, because stromal cells in longterm bone marrow cultures (LTBMC) are supportive of hematopoietic progenitor cell survival in vitro, while umbilical vein endothelial cells (EC) and diploid fibroblasts (DF) are not, we also sought to test the hypothesis that SF gene expression would differ in cells from LTBMC when compared with EC or DF. Using reverse-transcription polymerase chain reaction amplification (RT-PCR), ribonuclease protection assays (RPA), and Northern blot analysis, SF was found to be constitutively transcribed in EC, DF, and LTBMC. IL-1 alpha neither induced accumulation of SF mRNA nor altered the ratio of exon 6+ to exon 6- transcripts in these stromal cells. By Northern blot analysis, the predominant SF mRNA species was shown to be 5.6 kb; a minor population of 3.6 kb was also found. Low levels of membrane-bound SF protein were found to be constitutively expressed by all three types of stromal cells, and were not regulated by IL-1 alpha. We conclude that the unique capacity of LTBMC to support in vitro hematopoiesis, when compared with EC or DF, cannot be explained on the basis of qualitative or quantitative differences in SF gene expression in these cells.
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PMID:Constitutive expression of steel factor gene by human stromal cells. 768 92

Angiotensin I-converting enzyme (ACE) is known to be present at the surface of endothelial cells and also in the adventitia in large vessels. The presence of ACE in the vascular smooth muscle remains controversial. We microdissected segments of adventitia and media with or without endothelium from a region devoid of collateral arteries. The membrane-bound ACE activity in the media averaged 41% (pmol [glycine-1-14C]hippuryl-L-histidyl-L-leucine hydrolyzed.g tissue-1.min-1) of the values found in the whole aorta, whereas the adventitia contained only 6%. Immunoreactive ACE in media was characterized by Western blotting. ACE mRNAs were detected and characterized after polymerase chain amplification in isolated media. Angiotensin I and angiotensin II were equally able to contract medial rings, and the response to angiotensin I was blocked by enalaprilat. In aortas of two-kidney, one-clip hypertensive rats, there was an increase in ACE mRNA estimated by ribonuclease protection assay (P = 0.02) and in ACE activity at 15 days and 1 and 3 mo after clipping. This corresponded to a 1.5- to 2-fold increase in the ACE activity of both the media and the adventitia compared with sham-operated rats (P < or = 0.02). Thus ACE gene expression occurs in smooth muscle of rat aorta, which contains roughly the same amount of enzyme as the endothelium and readily converts angiotensin I to angiotensin II. ACE in the medial layer and the adventitia is upregulated in renovascular hypertension.
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PMID:ACE in three tunicae of rat aorta: expression in smooth muscle and effect of renovascular hypertension. 797 8

Splenic B cells from BALB/c mice bearing mammary adenocarcinomas are capable of performing Ab-dependent cellular cytotoxicity. Effector-target conjugation after 18 h results in minimal cytoplasmic damage, whereas extensive nuclear disintegration is observed. To determine whether splenic B cells from tumor-bearing mice can effect direct cytotoxicity against tumor cells, L929 and WEHI 164 cells were used as targets. B lymphocytes from tumor-bearing mice, but not from normal animals, were capable of lysing these two types of tumor cells. However, only a low level of cytotoxicity could be detected when the nontumorigenic 3T3 cells were used as targets. To elucidate the mechanism of cytotoxicity of these killer B cells, RNase protection assays were performed using perforin, granzyme A, TNF-alpha, and lymphotoxin probes. No perforin, granzyme A, or lymphotoxin RNA could be detected in purified preparations of B cells from normal and tumor-bearing mice. B cells from normal mice did not have TNF-alpha RNA. In contrast, B cells from tumor bearers expressed TNF-alpha RNA. TNF-alpha could be detected in supernatants from both unstimulated and stimulated tumor bearers' splenic B cells, as measured by ELISA, and its lytic activity was neutralized by anti-TNF-alpha Ab. Western blots revealed the presence of TNF-alpha on the surface of the killer B cells. Paraformaldehyde-fixed B cells from tumor-bearing mice but not from normal animals were able to lyse TNF-alpha-sensitive tumor targets. This cytotoxicity was neutralized by anti-TNF-alpha Ab. These results suggest that TNF-alpha in soluble and membrane-bound forms may be involved in the mechanism of cytotoxicity exerted by B cells from tumor-bearing mice.
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PMID:Soluble and membrane-bound TNF-alpha are involved in the cytotoxic activity of B cells from tumor-bearing mice against tumor targets. 814 19

Systemic interleukin-1 (IL-1) activates the hypothalamo-pituitary-adrenal (HPA) axis, an effect exerted through increased synthesis and secretion of corticotropin-releasing factor (CRF) by parvicellular neurosecretory neurons. The site(s) and mechanism(s) through which circulating IL-1 may access central systems governing HPA axis output remain obscure. To identify potential cellular targets for blood-borne IL-1, we analyzed the distribution of mRNA encoding the rat type 1 IL-1 receptor (IL-1R1) in rat brain. Regional ribonuclease protection assays detected a single protected fragment corresponding to the membrane-bound form of the IL-1R1 mRNA in all areas analyzed. In situ hybridization revealed labeling predominantly over barrier-related cells, including the leptomeninges, non-tanycytic portions of the ependyma, the choroid plexus, and vascular endothelium. Low to moderate levels of the IL-1R1 mRNA were detected in just a few neuronal cell groups, including the basolateral nucleus of the amygdala, the arcuate nucleus of the hypothalamus, the trigeminal and hypoglossal motor nuclei, and the area postrema. No specific labeling for IL-1R1 mRNA was detected over neurons that respond to intravenous IL-1 beta by induction of transcription factor Fos, including hypophysiotropic CRF cells and brainstem catecholamine neurons. Injection of IL-1 beta did, however, provoke induction of mRNA encoding the immediate-early gene, NGFI-B, but not c-fos, in two major loci of IL-1R1 expression, vascular endothelial cells, and the area postrema. Intravenous injection of IL-1 beta acutely down-regulated IL-1R1 mRNA in perivascular cells, but not in neuronal cell groups. These results suggest the parenchymal sites of IL-1R1 expression in rat to be distinct from those reported previously in mouse. The common expression in both species of an IL-1R in non-neuronal elements highlights the possibility that IL-1-mediated activation of CRF neurons may result from cytokine-receptor interaction at vascular, and/or other barrier-related, sites to trigger release of secondary signalling molecules in a position to interact with components of HPA control circuitry.
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PMID:Type 1 interleukin-1 receptor in the rat brain: distribution, regulation, and relationship to sites of IL-1-induced cellular activation. 857 22

The occurrence of multidrug resistance (MDR) is one of the main obstacles in the successful chemotherapeutic treatment of cancer. MDR cell lines are resistant to the so-called naturally occurring anti-cancer drugs, such as anthracyclines, Vinca alkaloids and epipodophyllotoxins, but are not cross-resistant to alkylating agents, antimetabolites and cisplatin. So far, three separate forms of MDR have been characterized in more detail: classical MDR, non-Pgp MDR and atypical MDR. Although all three MDR phenotypes have much in common with respect to cross-resistance patterns, the underlying mechanisms certainly differ. Atypical MDR is associated with quantitative and qualitative alterations in topoisomerase II alpha, a nuclear enzyme that actively participates in the lethal action of cytotoxic drugs. Atypical MDR cells do not overexpress P-glycoprotein, and are unaltered in their ability to accumulate drugs. In this review we will focus on classical and non-Pgp MDR. The molecular mechanism of classical and non-Pgp MDR is transcriptional activation of membrane-bound transport proteins. These transport proteins belong to the ATP-binding cassette (ABC) superfamily of transport systems. The classical MDR phenotype is characterized by a reduced ability to accumulate drugs, due to activity of an energy-dependent uni-directional, membrane-bound, drug-efflux pump with broad substrate specificity. The classical MDR drug pump is composed of a transmembrane glycoprotein (P-glyco-protein-Pgp) with a molecular weight of 170 kD, and is, in man, encoded by the so-called multidrug resistance (MDR1) gene. Typically, non-Pgp MDR has no P-gly-coprotein expression, yet has about the same cross-resistance pattern as classical MDR. This non-Pgp MDR phenotype is caused by overexpression of the multidrug resistance-associated protein (MRP) gene, which encodes a 190 kD membrane-bound glycoprotein (MRP). MRP probably works by direct extrusion of cytotoxic drugs from the cell and/or by mediating sequestration of the drugs into intracellular compartments, both leading to a reduction in effective intracellular drug concentrations. For the classical MDR phenotype, evidence is accumulating that it plays a role indeed, in clinical drug resistance, especially in some hematological malignancies (acute myeloid leukemia, multiple myeloma and non-Hodgkin's lymphoma) and solid tumors (soft tissue sarcomas and neuroblastoma). The association of MRP with clinical drug resistance has not been elaborated, yet, and studies on MRP expression in human cancer have just begun. We found that overexpression of MRP, as determined by RNase protection assay as well as by immunohistochemistry, occurs in several human cancers, among which are cancer of the lung, esophagus, breast and ovary, and leukemias. Further studies are indicated to establish whether elevated MRP expression at diagnosis is an unfavorable prognostic factor for clinical outcome of chemotherapy.
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PMID:Molecular mechanisms of multidrug resistance in cancer chemotherapy. 888 Aug 78

We have developed a nonisotopic RNase protection assay using RNA probes that are dual-labeled with biotin and fluorescein for detection. This system utilizes capture of the protected RNA probe hybrids to streptavidin-coated membranes attached to plastic dipsticks, complexing of anti-fluorescein-urease conjugate with the labeled RNA probe, and quantitative detection of the membrane-bound complex by a potentiometric silicon sensor. The dual-label RNase protection (RP) assay was capable of measuring beta-actin mRNA in cellular RNA samples at the 27- to 45-amol level (10-17 pg) with high precision (%CV < 7). We have used this method to quantitate the levels of erbB-2 mRNA in the human tumor cell lines SKBR-3, SKOV-3, and MCF-7. The levels of erbB-2 mRNA in these cells were 105, 190, and 0.9 amol per microgram of cellular RNA, respectively. The dual-label RP method should be useful for measuring the mRNA expression for other erbB-2 homologs such as erbB-3 and erbB-4 in tumor cells and tissues and can be a generally useful mRNA quantitative method for laboratories wishing to minimize radioisotope use.
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PMID:Nonisotopic quantitation of mRNA using a novel RNase protection assay: measurement of erbB-2 mRNA in tumor cell lines. 893 64


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