Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein kinase C (PKC) activation was examined for its role in delta-opioid receptor down-regulation in the neuroblastoma X glioma hybrid cell line NG108-15. Incubation of NG108-15 cells for 2 hr at 37 degrees with up to 1 microM 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA), a phorbol ester that activates PKC, had no effect on opioid binding to membranes prepared from these cells. However, as little as 3 nM PMA incubated with an opioid agonist and NG108-15 cells potentiated the decrease and the rate of decrease of opioid binding, compared with agonist alone. Scatchard analysis of [3H][D-Ala2,D-Leu5]enkephalin (DADLE) binding revealed that NG108-15 cells incubated for 3 hr with 1 nM DADLE and 30 nM PMA displayed a > 50% reduction in the number of [3H]DADLE binding sites with no affinity change at the remaining sites, compared with cells treated with DADLE alone. The antagonist naloxone blocked both DADLE-induced and PMA-enhanced DADLE-induced down-regulation. The agonists morphine and cyclazocine, which alone were unable to induce delta receptor down-regulation, did so in the presence of PMA. The PKC inhibitor staurosporine and down-regulation of PKC by chronic PMA treatment blocked PMA potentiation of DADLE-induced down-regulation, but not "normal" DADLE-induced down-regulation. The enhancement of down-regulation by PMA was unaffected by either metabolic inhibitor or incubations at 20 degrees, conditions that blocked down-regulation by DADLE alone. NG108-15 cells incubated with [3H]DADLE and PMA retained more [3H]DADLE than cells incubated with [3H]DADLE alone, suggesting that PMA enhanced receptor internalization instead of merely inhibiting membrane binding. The diacylglycerol 1-oleoyl-2-acetyl-glycerol and bradykinin substituted for PMA but not carbachol, indicating that PKC activated physiologically may play a role in delta receptor down-regulation.
Mol Pharmacol 1992 Oct
PMID:Protein kinase C activation increases the rate and magnitude of agonist-induced delta-opioid receptor down-regulation in NG108-15 cells. 133 57

The structure of microtubules has been characterized to 3 nm resolution employing time-resolved X-ray scattering. This has revealed detailed structural features of microtubules not observed before in solution. The polymerization of highly purified tubulin, induced by the antitumour drug taxol, has been employed as a microtubule model system. This assembly reaction requires Mg2+, is optimal at a 1:1 taxol to tubulin heterodimer molar ratio, proceeds with GTP or GDP and is intrinsically reversible. The X-ray scattering profiles are consistent with identical non-globular alpha and beta-tubulin monomers ordered within the known helical surface lattice of microtubules. Purified tubulin-taxol microtubules have a smaller mean diameter (approx. 22 nm) than those induced by microtubule associated proteins or glycerol (approx. 24 nm), but nearly identical wall substructure to the resolution of the measurements. This is because the majority of the former consist of only 12 protofilaments instead of the typical 13 protofilaments, as confirmed by electron microscopy of thin-sectioned, negatively stained and ice-embedded taxol microtubules. It may be concluded that taxol induces a slight reduction of the lateral contact curvature between tubulin monomers. The main fringe pattern observed in cryo-electron micrographs is consistent with a simple 12 protofilament 3-start skewed lattice model. Cylindrical closure of this lattice can be achieved by tilting the lattice 0.8 degrees with respect to the microtubule axis. The closure implies a discontinuity in the type of lateral contacts between the tubulin monomers (regardless of whether these are of the -alpha-beta- or the -alpha-alpha-/-beta-beta- type), which indicates that lateral contacts and the subunit specificity of taxol binding are, to a large degree, equivalent.
J Mol Biol 1992 Jul 05
PMID:Low resolution structure of microtubules in solution. Synchrotron X-ray scattering and electron microscopy of taxol-induced microtubules assembled from purified tubulin in comparison with glycerol and MAP-induced microtubules. 135 57

A novel small nuclear ribonucleoprotein (snRNP) complex containing both U11 and U12 RNAs has been identified in HeLa cell extracts. This U11/U12 snRNP complex can be visualized on glycerol gradients, on native polyacrylamide gels, and by selection with antisense 2'-O-methyl oligoribonucleotides. RNase H-mediated degradation of the U12 snRNA confirmed a direct interaction between the U11 and U12 snRNPs. This snRNP complex is the first to be identified involving low-abundance snRNPs. Selection of the U11/U12 snRNP complex is sensitive to high salt, suggestive of a protein-mediated interaction. Secondary structure analyses revealed several regions of the U11 snRNP accessible for interaction with other RNAs or proteins but no detectable difference between the accessibility of these regions in the U11 monoparticle compared with the U11/U12 snRNP complex. There are also several accessible single-stranded regions in the U12 snRNP, and oligonucleotide-directed RNase H digestion identified nucleotides 28 to 36 of U12 as containing sequences required for the U11/U12 interaction. Both the U12 snRNP and the U11/U12 snRNP complex can be disrupted without altering the cleavage/polyadenylation activity of a nuclear extract.
Mol Cell Biol 1992 Mar
PMID:The low-abundance U11 and U12 small nuclear ribonucleoproteins (snRNPs) interact to form a two-snRNP complex. 137 90

3 alpha-Hydroxysteroid dehydrogenase (3 alpha-HSD) was purified greater than 500-fold from human liver cytosol. The purification was monitored using 5 beta-[3H]dihydrocortisol (5 beta-DHF) as substrate. Electrophoretically homogeneous enzyme was obtained using a procedure that involved ammonium sulfate precipitation and three successive column chromatography steps: DEAE-cellulose, hydroxylapatite and Blue-Sepharose. The enzyme is a monomer since the native molecular weight was found to be 37,000, using a calibrated Sephadex G-75 column, and the denatured subunit molecular weight was determined to be 38,500, by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The enzyme had a pI of 5.6-5.9. The 3-ketosteroids: cortisol, testosterone, progesterone and androstenedione, were not substrates for 3 alpha-HSD indicating that a saturated 4,5 double bond was required for substrate activity. The conformation at the 5 position, however, did not influence substrate activity since 5 alpha- and 5 beta-DHF and 5 alpha-dihydrotestosterone were all reduced at similar rates. The purified enzyme preferred NADPH to NADH as a cofactor and showed a broad peak of activity in the pH range of 6.8-7.4. The apparent Km for 5 beta-DHF was 18 microM. The enzyme was markedly stabilized by 50 mM phosphate buffer containing 10 to 20% glycerol at 4 degrees C. Freezing and thawing of the enzyme resulted in a large loss of activity during early stages of the purification. This is the first report of the purification to homogeneity of 3 alpha-HSD from human tissue.
J Steroid Biochem Mol Biol 1992 Oct
PMID:Purification and properties of human hepatic 3 alpha-hydroxysteroid dehydrogenase. 139 Feb 84

We have isolated mutants of the yeast Saccharomyces cerevisiae that are defective in localization of nuclear proteins. Chimeric proteins containing the nuclear localization sequence from SV40 large T-antigen fused to the N-terminus of the mitochondrial F1 beta-ATPase are localized to the nucleus. Npl (nuclear protein localization) mutants were isolated by their ability to grow on glycerol as a consequence of no longer exclusively targeting SV40-F1 beta-ATPase to the nucleus. All mutants with defects in localization of nucleolar proteins and histones are temperature sensitive for growth at 36 degrees C. Seven alleles of NPL3 and single alleles of several additional genes were isolated. NPL3 mutants were studied in detail. NPL3 encodes a nuclear protein with an RNA recognition motif and similarities to a family of proteins involved in RNA metabolism. Our genetic analysis indicates that NPL3 is essential for normal cell growth; cells lacking NPL3 are temperature sensitive for growth but do not exhibit a defect in localization of nuclear proteins. Taken together, these results indicate that the mutant forms of Npl3 protein isolated by this procedure are interfering with nuclear protein uptake in a general manner.
Mol Biol Cell 1992 Aug
PMID:A mutant nuclear protein with similarity to RNA binding proteins interferes with nuclear import in yeast. 139 78

We have examined the effect of 1-palmitoyl-2-(10-pyrenyl)decanoyl-sn-glycerol-3-phosphatidylcholine (Pyr-PC) concentration on the ratio of excimer fluorescence to monomer fluorescence (E/M) in L-alpha-dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles at 30 degrees C, with special attention focussed on the smoothness of the curve. We observed a series of dips, in addition to kinks, in the plot of E/M versus the mole fraction of Pyr-PC (XPyrPC). The observation of dips is a new finding, perhaps unique for Pyr-PC in DMPC since only kinks were observed for Pyr-PC in L-alpha-dipalmitoylphosphatidylcholine (DPPC) and in egg yolk phosphatidylcholine (egg-PC) (Somerharju et al., 1985. Biochemistry. 24: 2773-2781). The dips/kinks observed here are distributed according to a well defined pattern reflecting a lateral order in the membrane, and distributed symmetrically with respect to 50 mol% Pyr-PC. Some of the dips appear at specific concentrations (YPyrPC) according to the hexagonal super-lattice model proposed by Virtanen et al. (1988. J. Mol. Electr. 4: 233-236). However, the observations of dips at XPyrPC > 66.7 mol% and the kink at 33.3 mol% cannot be interpreted by the model of Virtanen et al. (1988). These surprising results can be understood by virtue of an extended hexagonal super-lattice model, in which we have proposed that if the pyrene-containing acyl chains are regularly distributed as a hexagonal super-lattice in the DMPC matrix at a specific concentration YPyrPC, then the acyl chains of DMPC can form a regularly distributed hexagonal super-lattice in the membrane at a critical concentration (1-YPyrPC). The excellent agreement between the calculated and the observed dip/kink positions, except for the dip at 74 mol% and the kink at 40 mol%, provides most compelling evidence that lipids are regularly distributed into hexagonal super-lattices in Pyr-PC/DMPC mixtures at specific concentrations. The physical nature of the dips not only gives us a better understanding of lipid lateral organization in membranes but also will lead to new theoretical considerations and experimental designs for exploring the relationship between lipid regular distribution and membrane functions.
 ...
PMID:E/M dips. Evidence for lipids regularly distributed into hexagonal super-lattices in pyrene-PC/DMPC binary mixtures at specific concentrations. 142 Sep 34

We have recently shown that a triacylglycerol (TG)-fatty acid cycle is operating in rat myocardial cells incubated in a hypoxic, glucose-containing incubation medium (Myrmel et al., 1991a). In the present study we investigated whether this cycle occurred in hypoxic, glucose-deprived myocytes, and whether high TG levels would increase TG-fatty acid cycling and thereby energy consumption. Myocytes with elevated contents of TG were obtained from the hearts of streptozotocin-induced diabetic rats (diabetic myocytes) and from normal rat myocytes prepared in the presence of oleic acid (TG-loaded myocytes). The TG content of diabetic and TG-loaded myocytes prior to hypoxic incubations was more than two times higher (P < 0.05) than that of their respective controls (123.8 +/- 20.6 and 125.3 +/- 12.7 vs 56.8 +/- 6.0 and 58.6 +/- 9.4 nmol/10(6) cells, mean +/- S.E., n = 7). Only diabetic and TG-loaded myocytes expressed marked reductions in TG content during glucose free incubations. There were no differences in TG-fatty acid cycling between the various myocyte groups, calculated as the difference between glycerol output and the concomitant decrease in TG (range: 36.7 +/- 8.1- 48.9 +/- 9.7 nmol TG/10(6) cells.2h). Apparently, the cycle was continuous throughout the whole incubation period despite falling ATP levels, contracture (rounding up) of myocytes, as well as cessation of glycogenolysis after about 40 min incubation. The cellular content of glycerol-3-phosphate, known to control TG-fatty acid cycling, increased continuously and to the same extent throughout the 2 h incubation period. Futile energy consumption associated with TG-fatty acid cycling, amounted to approximately 30% of total cellular energy consumption for the whole incubation period. In conclusion, hypoxic glucose deprived rat myocytes show TG-fatty-acid cycling, even after cessation of glycogenolysis. The extent of cycling, and thus the energy cost associated with it, was not influenced by the initial level of TG in the myocytes. We propose that glycerol-3-phosphate needed to fuel the TG-fatty acid cycle after exhaustion of the glycolytic supply is derived from phospholipid degradation.
J Mol Cell Cardiol 1992 Aug
PMID:Triacylglycerol metabolism in hypoxic, glucose-deprived rat cardiomyocytes. 143 15

Phytomonas sp. isolated from Euphorbia characias was adapted to SDM-79 medium. Cells isolated in the early stationary phase of growth were analyzed for their capacity to utilize plant carbohydrates for their energy requirements. The cellulose-degrading enzymes amylase, amylomaltase, invertase, carboxymethylcellulase, and the pectin-degrading enzymes polygalacturonase and oligo-D-galactosiduronate lyase were present in Phytomonas sp. and were all, except for amylomaltase, excreted into the external medium. Glucose, fructose and mannose served as the major energy substrates. Catabolism of carbohydrates occurred mainly via aerobic glycolysis according to the Embden-Meyerhof pathway, of which all the enzymes were detected. Likewise, the end-products of glycolysis, acetate and pyruvate, glycerol, succinate and ethanol were detected in the culture medium, as were the enzymes responsible for their production. Mitochondria were incapable of oxidizing succinate, 2-oxoglutarate, pyruvate, malate and proline, but had a high capacity to oxidize glycerol 3-phosphate. This oxidation was completely inhibited by salicylhydroxamic acid. No cytochromes could be detected either in intact mitochondria or in sub-mitochondrial particles. Mitochondrial respiration was not inhibited by antimycin, azide or cyanide. The glycolytic enzymes, from hexokinase to phosphoglycerate kinase, and the enzymes glycerol kinase, glycerol-3-phosphate dehydrogenase, phosphoenolpyruvate carboxykinase, malate dehydrogenase and adenylate kinase, were all associated with glycosomes that had a buoyant density of about 1.24 g cm-1 in sucrose. Cytochemical staining revealed the presence of catalase in these organelles. The cytosolic enzyme pyruvate kinase was activated by fructose 2,6-bisphosphate, typical of all other pyruvate kinases from Kinetoplastida. The energy metabolism of the plant parasite Phytomonas sp. isolated from E. characias resembled that of the bloodstream form of the mammalian parasite Trypanosoma brucei.
Mol Biochem Parasitol 1992 Sep
PMID:Characterization of carbohydrate metabolism and demonstration of glycosomes in a Phytomonas sp. isolated from Euphorbia characias. 143 59

The Bacillus subtilis glpD gene, encoding glycerol-3-phosphate (G3P) dehydrogenase, is preceded by a promoter and an inverted repeat which is located between the promoter and the glpD coding region. The inverted repeat acts as a transcriptional terminator in vitro. Expression of glpD is induced by G3P in the presence of the glpP gene product. Full-length glpD transcripts can be detected only in glycerol-induced cells. The major glpD transcript is initiated from the glpD promoter but minor amounts of larger transcripts, possibly initiated at upstream glp promoters, can also be found. In uninduced cells short transcripts are present, corresponding to initiation at the glpD promoter and termination at the inverted repeat. Upon induction, these short transcripts disappear and are replaced by full-length glpD transcripts. The 3'-ends of full-length glpD transcripts were mapped to an inverted repeat located immediately downstream of glpD. These results show that glpD of B. subtilis is regulated by termination/antitermination of transcription.
Mol Microbiol 1992 Oct
PMID:An inverted repeat preceding the Bacillus subtilis glpD gene is a conditional terminator of transcription. 147 85

The vascular endothelium can be regarded as a widely distributed organ, interposed between the intravascular and extravascular spaces, with a pluripotent function in the regulation of capillary diameter, vascular homeostasis, lipoprotein metabolism and the vascular response to injury. In the basal physiological state these processes provide a non-thrombotic, non-inflammatory vascular lining preventing uncontrolled inflammation and coagulation. Endothelial cells respond to potential harmful conditions (mechanical stress, anoxia, ischemia and oxidative stress) and a variety of hormones and vasoactive mediators by inducing coagulation and production of inflammatory mediators through the production of 'bioactive' lipids. Although the number of studies in isolated myocardial endothelial cells is limited, from the presumed metabolic analogy with endothelial cells isolated (and cultured) from other organs, one may conclude that the bioactive lipids include oxygenated arachidonate metabolites (eicosanoids) and the platelet activating factor (1--O-alkyl-2-acetyl-sn-glycerol-3-phosphocholine; PAF). All aspects of lipid metabolism, related to the production of eicosanoids and PAF, are present within myocardial endothelial cells. There is uptake and incorporation of fatty acids by endothelial cells and liberation from endogenous triacylglycerol and (membrane) phospholipid stores by (phospho)lipases. Endothelial cells oxidize fatty acids in a carnitine-dependent, mitochondrial, pathway. Endothelial cells actively interact with high density lipoprotein (HDL) and low density lipoprotein (LDL) leading to uptake of cholesterol(esters) that undergo intracellular hydrolysis, and re-esterification to phospho- and neutral lipids, and leaving the LDL-particle modified in a way that makes them bind to the scavenger receptor on macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1992 Oct 21
PMID:Lipid metabolism of myocardial endothelial cells. 148 Jan 46


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>