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

---

Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Characteristics of Drug-Resistant Cell Sublines L5178Y: We isolated aclarubicin (ACR)-, adriamycin (ADM)-, bleomycin (BLM-, and macromomycin (MCR)-resistant (r) cell sublines. The BLMr cell line did not show cross-resistance to other drugs. The ACRr and ADMr cell lines displayed cross-resistance to other anthracyclines. The drug-resistance of these cell lines was due to changes in membrane transport. All four resistant cell lines showed higher activity of membrane alkaline phosphodiesterase (APD) than the parental cells. The APD of the BLMr scell line differed from that of the parental line in molecular size. 2-Crotonyloxymethyl-4, 5, 6-trihydroxycyclohex-2-enone: We isolated an inhibitor of APD from a Streptomyces species. This substance inhibited the drug-resistant cell lines of L5178Y more markedly than the parental line in culture and showed synergistic effects with ACR against the ACRr cell line. It was an SH-inhibitor, and prevented DNA polymerase alpha and some mitotic processes. Transplantability of Drug-Resistant L5178Y Cells: DBA/2 mice, the syngeneic host, exhibited more resistance to ip transplantation of drug-resistant cell lines than parental cells. The animals showed the strongest resistance to the ACRr cell line. Treatment with cyclophosphamide markedly reversed the host resistance, suggesting that the immune mechanism was involved in the resistance. The ACRr cells were sensitive to NK cells, but the parental cells were not. Injection with anti-asialo GM1 markedly decreased host resistance. The results suggested that NK cells were involved in the transplantation resistance of mice to the ACRr cells. 230-Kilodalton Membrane Protein of ACRr Cells Identified by Monoclonal Antibody: We prepared monoclonal antibodies to the ACRr cells, and found that a monoclonal antibody, designated SC438, specifically agglutinated the ACRr cells. A specific 230K membrane protein was found in the ACRr cells by immunoprecipitation. Natural BLM Resistance of Chinese Hamster V79 Cells: V79 cells were more resistant to BLM than CHO cells. This natural drug-resistance was is due to higher BLM hydrolase activity. We isolated BLM cell lines, and found that BLM supersensitivity was not due to BLM hydrolase, but to decreased repairing activity of DNA damage.
...
PMID:[Studies on the mechanism of drug resistance in tumor cells and a new antitumor antibiotic]. 621 60

Two classes of high affinity, cGMP-specific binding sites have been found in association with a peripheral membrane protein in rod outer segments. [3H]cGMP and a photoaffinity label, 8-N3-[32P]cIMP, have been used to study these cGMP binding sites. The cGMP binding sites co-migrated with rod outer segment phosphodiesterase (EC 3.1.4.17) upon Bio-Gel A-0.5m column chromatography, sucrose density gradient centrifugation, and isoelectric focusing (pI 5.35). Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the 8-N3-[32P]cIMP-labeled protein also migrated in a position identical with that of purified phosphodiesterase. Scatchard analysis, using purified phosphodiesterase, revealed the presence of two classes of cGMP binding sites with apparent KD values of 0.16 and 0.83 microM. A number of observations indicated that these high affinity, cGMP-specific binding sites are distinct from the phosphodiesterase catalytic site. cAMP, which is a substrate for phosphodiesterase, did not bind to the high affinity cGMP specific sites. Limited tryptic proteolysis of phosphodiesterase resulted in a striking activation of the catalytic activity and a 96% loss of cGMP binding. 1-Methyl-3-isobutylxanthine inhibited phosphodiesterase activity and enhanced the specific binding of cGMP. Mg2+ was necessary for phosphodiesterase activity, but not for high affinity cGMP binding. Finally, phosphodiesterase activity and the cGMP-specific high affinity sites showed different stabilities on storage in phosphate buffer. These specific high affinity cGMP binding sites may be involved in the regulation of phosphodiesterase activity.
...
PMID:Cyclic GMP-specific, high affinity, noncatalytic binding sites on light-activated phosphodiesterase. 625 76

The peripheral cycle AMP phosphodiesterase from rat liver plasma membranes binds with high affinity (2.4 nM) to a single class of receptor sites on the liver plasma membrane. These receptor sites appear to be proteins, as they are trypsin- and heat-labile. The sensitivity of these sites to denaturation by trypsin and heat is a first-order process. The presence of Ca2+ (5 mM) increases the affinity of these sites for the enzyme, but does not alter their total number. The receptor sites and the cyclic AMP phosphodiesterase occur in similar numbers, at around 2 pmol/mg of plasma-membrane protein. It is proposed that the peripheral, liver plasma-membrane cyclic AMP phosphodiesterase is attached to a specific site on the insulin receptor and that the binding of insulin to the receptor site triggers a conformational change in the enzyme such that the enzyme can be phosphorylated and activated by an endogenous cyclic AMP-dependent protein kinase.
...
PMID:The insulin-stimulated cyclic AMP phosphodiesterase binds to a single class of protein sites on the liver plasma membrane. 627 57

Our experiments have delineated the flow of information in the cyclic nucleotide cascade of vision of ROS. A single, photoexcited rhodopsin molecule activates several hundred phosphodiesterase molecules in two stages. First, photoexcited rhodopsin (R*) interacts with transducin (T), a peripheral membrane protein consisting of alpha- (39 kD), beta- (36 kD), and gamma- (approximately 10 kD) subunits. R* catalyzes the exchange of GTP for GDP bound to the subunit of transducin. About 500 T alpha- GTPs are produced per photoexcited rhodopsin at low light levels. T alpha-GTP, released from the beta- and gamma-subunits of transducin, then interacts with the phosphodiesterase to relieve the inhibitory constraint imposed by its gamma-subunit. Hydrolysis of GTP bound to T alpha serves to restore the system to the dark state. Transducin is the amplified signal carrier in this light-triggered cascade. The formation of hundreds of T alpha- GTPs is likely to be the first stage of amplification in visual excitation. The photoactivation of the phosphodiesterase in ROS closely resembles the activation of adenylate cyclase in hormone-sensitive cells. Our cholera toxin labeling studies have shown that transducin is akin to the signal-coupling G protein of the adenylate cyclase system. Cholera toxin specifically ADP- ribosylates and inactivates the GTPase activity of T alpha, just as it does with Gs. The action of pertussis toxin on ROS further underscores the homology of the photoreceptor and hormone-responsive systems. It seems likely that transducin, the stimulatory G protein, and the inhibitory G protein are members of the same family of signal-amplifying proteins. The study of the cyclic nucleotide cascade of vision is proving to be rewarding in affording a view of a recurring motif of signal amplification in nature in addition to providing insight into the mechanism of vision.
...
PMID:Transducin and the cyclic GMP phosphodiesterase: amplifier proteins in vision. 632 79

The three-dimensional high-resolution structure of rhodopsin is unknown, as is the case for almost all integral membrane patients. As part of an alternative approach to determine of membrane protein structure, we are pursuing the structure of cytoplasmic domains of this G-protein receptor. A peptide, rhoIII, with the sequence of the third cytoplasmic loop of bovine rhodopsin was synthesized. This soluble peptide was biologically active, inhibiting the light-stimulated activation of the rod cell phosphodiesterase by rhodopsin in rod outer segment disks. Therefore rhoIII likely contains structural elements characteristic of native rhodopsin. The structure of rhoIII was determined by H nuclear magnetic resonance. A defined structure was obtained for about 70% of rhoIII. A model of a turn-helix-turn motif could then be proposed for the third cytoplasmic loop of rhodopsin, which suggested a molecular switch for activation of the G-protein by the receptor.
...
PMID:Structure of the third cytoplasmic loop of bovine rhodopsin. 757 70

Monoclonal antibody RB13-6 recognizes a subset of rat brain glial precursor cells that are highly susceptible to malignant conversion by the carcinogen N-ethyl-N-nitrosourea. The corresponding cell surface antigen was identified as a membrane glycoprotein (gp130RB13-6) and purified by immunoaffinity chromatography from the tumorigenic neuroectodermal rat cell line BT4Ca. Sequencing of 5 endoproteinase-generated peptides of the purified antigen permitted the specific amplification of a cDNA fragment by reverse transcription-polymerase chain reaction and subsequent isolation of the complete coding sequence from a fetal rat brain cDNA library. The derived amino acid sequence indicates that the RB13-6 antigen is related to the human and murine plasma cell membrane protein PC-1, a nucleotide pyrophosphatase/alkaline phosphodiesterase and ectoprotein kinase. Similarly, purified gp130RB13-6 possesses 5'-nucleotidase activity that can be inhibited with EDTA. Different from PC-1, gp130RB13-6 isolated from BT4Ca cells is not a disulfide-linked dimer and contains an RGD-tripeptide sequence which, together with other structural features, suggests a possible function in cell adhesion and its subversion in malignant phenotypes.
...
PMID:Affinity purification and cDNA cloning of rat neural differentiation and tumor cell surface antigen gp130RB13-6 reveals relationship to human and murine PC-1. 773 Mar 66

Adenylate cyclase, the catalytic protein that converts ATP to cAMP, plays a fundamental role in adrenergic signal transduction. Adenylate cyclase activity (pmol cAMP/mg/min) is generally assayed by measuring radiolabeled cAMP generated from [alpha-32P]ATP. Although sensitive, the radioactive approach is costly and time consuming. Given safety and environmental concerns, we developed a highly sensitive fluorometric assay for adenylate cyclase activity. This assay depends upon the breakdown of cAMP by phosphodiesterase to AMP, and the subsequent stimulation by AMP of glycogen phosphorylase a. Radioactive and fluorescence methods were compared using the same ventricular membrane preparations from five different rabbit hearts. Theophylline, used in the fluorometric assay, increased basal adenylate cyclase activity. However, adenylate cyclase kinetics, the dose response to isoproterenol, and the "fold" stimulation (agonist stimulated/basal adenylate cyclase activity) after isoproterenol (10(-6)M), guanylyl-5'-imidodiphosphate (GppNHp) (10(-4)M), and NaF (10(-2)M) were nearly identical with both methods. Adenylate cyclase activity can be measured with the fluorometric assay in samples as small as 10 micrograms of membrane protein. In summary, this new fluorometric assay is highly sensitive, safer, less costly, and less time consuming than radioactive assays for adenylate cyclase activity.
...
PMID:An enzymatic fluorometric assay for adenylate cyclase activity. 838 28

The effect of hormones on the morphology and cell surface polarity of the epithelial cell line MDCK was examined. When MDCK cells were seeded in high densities in media containing FCS a regular monolayer was formed. However, in serum-free medium supplemented with insulin, transferrin, prostaglandin E1, hydrocortisone and triiodothyronine, the development of a multilayer with intercellular lumina was observed. In hormone-depletion studies we identified PGE1 as the inducer of these multilayers. Since dibutyryl cyclic AMP and the phosphodiesterase inhibitor isobutyl methylxanthine could substitute for PGE1, we conclude that an elevated intracellular cAMP level resulted in formation of the multilayer. Further analysis by electron microscopy and immunocytochemistry revealed a polarized organization of the multilayered cells. Junctional complexes, enclosing microvilli-rich membrane domains, were found at the apices of adjacent cells facing the medium and those surrounding the intercellular lumina. Surprisingly, cells participating in the formation of both the free surface and the surface of the intercellular lumen, exhibited two distinct membranes with microvilli, each separated by junctional complexes. Immunolocalization of membrane marker proteins demonstrated that an apical 114 kDa membrane protein was localized to the free cell surfaces, the same membrane domains where extensive microvilli were also observed. The distribution of a basolateral 58 kDa membrane protein was restricted to sites of cell contact. These results provided evidence that nontransformed epithelial MDCK cells form multilayers in response to elevated cAMP levels; however, they retain the potential of developing cell surface polarity.
...
PMID:Elevated cAMP levels induce multilayering of MDCK cells without disrupting cell surface polarity. 839 Oct 11

The membrane protein plasma-cell-differentiation antigen 1 (PC-1) has been described as a phosphodiesterase-I/nucleotide pyrophosphatase and as an autophosphorylating protein kinase. It has been suggested, however, that PC-1 is not a real protein kinase and that the autophosphorylated enzyme represents a nucleotidylated derivative, which is formed on Thr238 (murine PC-1) as a catalytic intermediate during ATP hydrolysis [Belli, S.I., Mercuri, F.A., Sali, A.& Goding, J.W. (1995) Eur. J. Biochem. 228, 669-676]. We have investigated the proposed multifunctional role of PC-1 and show here that ATP hydrolysis and autophosphorylation represent two distinct catalytic reactions. The enzyme was radiolabeled when various concentrations (1-260 microM) of [alpha-32P]ATP or [alpha-32P]ADP, but not [gamma-32P]ATP, were used as substrates for the formation of the pyrophosphatase catalytic intermediate, especially in the presence of imidazole, which interferes with the hydrolysis of the nucleotidylated enzyme. In contrast, autoradiography revealed autophosphorylation only with [gamma-32P]ATP as the phosphoryl donor, and autophosphorylation has been shown to occur only at ATP concentrations below 5 microM. Autophosphorylation could also be differentiated from nucleotidylation by its higher resistance to alkaline treatment and its more basic pH optimum. An intestinal nucleotide pyrophosphatase with a structurally related catalytic site could not be autophosphorylated, which shows that autophosphorylation is not an intrinsic property of the nucleotide pyrophosphatase reaction. Autophosphorylation of PC-1 was associated with inactivation of its phosphodiesterase-I/nucleotide-pyrophosphatase activity. We propose that autophosphorylation of PC-1 on Thr238 at low ATP concentrations serves as an autoregulatory mechanism that makes Thr238 unavailable for participation in the hydrolysis of extracellular nucleotides when they become scarce.
...
PMID:Threonine autophosphorylation and nucleotidylation of the hepatic membrane protein PC-1. 891 28

Many developmentally regulated membrane proteins of lymphocytes are ecto-enzymes, with their active sites on the external surface of the cell. These enzymes commonly have peptidase, phosphodiesterase or nucleotidase activity. Their biological roles are just beginning to be discovered. Although their expression is usually associated with particular stages of lymphoid differentiation, the same gene products are often expressed on the surface of certain non-lymphoid cell types outside the immune system, indicating that their functions cannot be unique to lymphocytes, nor can they be ubiquitous. The plasma cell membrane protein PC-1 (phosphodiesterase I; EC 3.1.4.1/nucleotide pyrophosphatase; EC 3.6.1.9), which was one of the first serological markers for lymphocyte subsets to be discovered, is a typical example. Within the immune system, PC-1 is confined to plasma cells, which represent about 0.1% of lymphocytes. However, PC-1 is also expressed on cells of the distal convoluted tubule of the kidney, chondrocytes, osteoblasts, epididymis and hepatocytes. Recent work has shown that PC-1 is a member of a multigene family of ecto-phosphodiesterases that currently has two other members, PD-1 alpha (autotaxin) and PD-1 beta (B10). Within this family, the extracellular domains are highly conserved, especially around the active site. In contrast, the transmembrane and cytoplasmic domains are highly divergent. Individual members of the eco-phosphodiesterase family have distinct patterns of distribution in different cell types, and even within the same cell. For example, PC-1 is present only on the basolateral surface of hepatocytes, while B10 (PD-1 beta) is confined to the apical surface. Analysis of conservation and differences in the sequence of their cytoplasmic tails may illuminate intracellular targetting signals. Ecto-phosphodiesterases may play a part in diverse activities in different tissues, including recycling of nucleotides. They may also regulate the concentration of pharmacologically active extracellular compounds such as adenosine or its derivatives and cell motility. Some members may modulate local concentrations of pyrophosphate, and hence influence calcification in bone and cartilage.
...
PMID:Ecto-phosphodiesterase/pyrophosphatase of lymphocytes and non-lymphoid cells: structure and function of the PC-1 family. 955 61


<< Previous 1 2 3 4 5 6 Next >>

---