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)

In cultured rat hepatocytes, transcription of the glucokinase gene is turned on by insulin and turned off by glucagon/cAMP, the latter being the dominant effector system. It is thus possible that in the absence of hormones the gene is maintained in a repressed state by the basal level of cAMP and that insulin turns on transcription by relieving cAMP repression, for instance via activation of a cyclic-nucleotide phosphodiesterase. Three inhibitors of this class of enzymes were tested for their effect on the insulin-dependent induction of the glucokinase gene in hepatocytes. Isobutyl methylxanthine, the prototype inhibitor, abrogated the gene response to insulin, as shown by run-on transcription assay. Among the drugs investigated, Ly186126, a preferential inhibitor of type-III phosphodiesterase, proved the most potent in inhibiting insulin-induced accumulation of glucokinase mRNA. Type-III phosphodiesterase is inhibited by cGMP. Induction of glucokinase mRNA was prevented in hepatocytes challenged with insulin in presence of 8-bromoguanosine-3',5'-phosphate. These results are consistent with the involvement of type-III phosphodiesterase in transduction of the insulin signal to the glucokinase gene. However, we were unable to detect significant decreases in total cellular cAMP level or cAMP-dependent-protein-kinase ratio after the addition of insulin to hepatocytes. Many effects of glucagon are mediated via cAMP-dependent protein-kinase phosphorylation of regulatory proteins and, conversely, insulin effects are often accompanied by protein dephosphorylation. A specific inhibitor of protein phosphatases PP1 and PP2A, okadaic acid, was shown to abolish the transcriptional response of the glucokinase gene to insulin. Thus, interference of insulin with the cAMP signal transduction pathway at several steps may be a critical aspect of insulin action on hepatic glucokinase gene expression. In addition, insulin induction of glucokinase mRNA was suppressed by inhibitors of protein synthesis. The underlying mechanism was a severe inhibition of the transcriptional effect of insulin, rather than mRNA destabilization, as demonstrated by run-on transcription assays with nuclei from cycloheximide-treated or pactamycin-treated cells. Transcription of the glucokinase gene may therefore depend on de novo synthesis of the product of an early-response gene induced by insulin, or may require a short-lived trans-acting or accessory factor of transcription. Alternatively, insulin signalling may be compromised in hepatocytes by a mechanism indirectly related to the arrest of protein synthesis.
...
PMID:Insulin signalling and regulation of glucokinase gene expression in cultured hepatocytes. 128 Feb 18

The involvement of cAMP in the process of sperm capacitation has been the subject of several studies. In addition, the importance of protein-tyrosine phosphorylation in this process has been investigated, although only a few studies have been reported in the human. Since agents regulating the intracellular concentrations of cAMP affect sperm capacitation rates, the role of cAMP on the expression of phosphotyrosine-containing proteins was investigated during human sperm capacitation. Fetal cord serum ultrafiltrate, a known capacitation inducer in human spermatozoa, caused an increase in the phosphotyrosine content of 105- and 81-kDa proteins (p105 and p81), the two major phosphotyrosine-containing proteins of human spermatozoa. Similar effects were observed when spermatozoa were incubated with phosphodiesterase inhibitors or cell-permeant cAMP analogs, suggesting that cAMP is involved in these two processes. Forskolin, an adenylyl cyclase activator, also caused an increase in both sperm capacitation rates and tyrosine phosphorylation of p105 and p81, while 12-O-tetradecanoyl phorbol 13-acetate stimulated both capacitation and tyrosine phosphorylation of p105 and p81 only when spermatozoa were incubated in the presence of bicarbonate, in agreement with its reported effects on cAMP production and hamster sperm capacitation. The inhibition of these phenomena by cAMP-dependent protein kinase inhibitors, and the stimulation by protein phosphatase inhibitors, suggest that Ser/Thr protein phosphorylation plays an important role in the regulation of both sperm capacitation and protein-tyrosine phosphorylation pathways. However, observations that both calyculin A and okadaic acid stimulated sperm capacitation, whereas only calyculin A increased p105 and p81 phosphotyrosine content and sperm velocity, suggest that protein phosphatase PP1 is involved in the two latter phenomena while PP2A mediates sperm capacitation. These results suggest that divergent pathways might regulate tyrosine phosphorylation of p105 and p81 and sperm capacitation after cAMP-dependent phosphorylation of an intermediate protein.
...
PMID:Cyclic adenosine 3',5'monophosphate-dependent regulation of protein tyrosine phosphorylation in relation to human sperm capacitation and motility. 886 88

The flux of multisized fluorescein-isothiocyanate-labeled hydroxy ethyl starch (FITC-HES) macromolecules was used to assess changes in barrier function of rat pulmonary microvascular endothelial cell (RPMVEC) monolayers exposed to protein phosphatase (PP) inhibitors or cGMP analogs and atriopeptin (ANF). Two potent PP inhibitors, calyculin A (CalA) and okadaic acid (OA), increased RPMVEC permeability in a dose- and time-dependent manner, and CalA had a higher intrinsic activity than OA. In contrast, ANF and potent cGMP analogs had no effect on basal RPMVEC permeability. The phosphohistone PP activity contained in RPMVEC sonicates was inhibited by OA with an inhibition profile that suggested at least two components were present, with PP2A accounting for approximately 70% of the OA-inhibitable phosphohistone phosphatase activity. Following separation with heparin-Sepharose chromatography, PP activity exhibited equipotent inhibition by CalA and differential inhibition by OA. Differential inhibition of PP1 and PP2A by OA suggested that PP1 is involved in regulating RPMVEC barrier function. Permeabilized RPMVEC showed increased phosphorylation of several proteins in the presence of phosphatase inhibitors. Treatment with KT 5926, a myosin light chain (MLC) kinase (MLCK) inhibitor, or rolipram, a phosphodiesterase inhibitor, decreased 32P incorporation into immunoprecipitated MLC by CalA and OA. However, this effect did not abolish either the CalA- or OA-induced decrease in the RPMVEC barrier function. Localization of filamentous (F) actin was at the periphery as well as in the cytoplasm and perinuclear region, whereas nonmuscle myosin was seen in the perinuclear region. Neither of these patterns was changed in the presence of CalA. Thus, cGMP does not alter RPMVEC permeability, but inhibition of PP activity results in loss of barrier function by a mechanism independent from MLC phosphorylation.
...
PMID:Inhibition of serine-threonine protein phosphatases decreases barrier function of rat pulmonary microvascular endothelial cells. 918 Aug 95

We have previously reported that varying stimulus intensity produces qualitatively different types of synaptic plasticity in area CA1 of hippocampal slices: brief low-intensity (LI) theta-burst (TB) stimuli induce long-term potentiation (LTP), but if the stimulus intensity is increased (to mimic conditions that may exist during seizures), LTP is not induced; instead, high-intensity (HI) TB stimuli erase previously induced LTP ("TB depotentiation"). We now have explored the mechanisms underlying TB depotentiation using extracellular field recordings with pharmacological manipulations. We found that TB depotentiation was blocked by okadaic acid and calyculin A (inhibitors of serine/threonine protein phosphatases PP1 and PP2A), FK506 (a specific blocker of calcineurin, a Ca(2+)/calmodulin (CaM) protein phosphatase), and 8-Br-cAMP (an activator of protein kinase A) with 3-isobutyl-1-methylxanthine (IBMX, a phosphodiesterase inhibitor). These results suggest that protein phosphatase pathways are involved in the TB depotentiation similar to other type of down-regulating synaptic plasticity such as low-frequency stimulation (LFS)-induced long-term depression (LTD) and depotentiation in the rat hippocampus. However, TB depotentiation and LFS depotentiation could have differential functional significance.
...
PMID:Protein phosphatases mediate depotentiation induced by high-intensity theta-burst stimulation. 1257 46

The enzyme PP1gamma2 is a testis- and sperm-specific isoform of type 1 protein phosphatase (PP1), and it is the only isoform of PP1 in spermatozoa. The enzyme PP1gamma2 is essential for spermatogenesis and is also a key enzyme in the development and regulation of sperm motility. The carboxy terminus of the enzyme contains a consensus amino acid sequence for phosphorylation by cyclin-dependent kinases. Using antibodies specific to this phosphorylated amino acid sequence domain, we found that phosphorylated PP1gamma2 is present in bovine epididymal spermatozoa. The level of phosphorylated PP1gamma2 is significantly higher in motile caudal compared to immotile caput epididymal spermatozoa. A number of treatments, such as 2-chloro adenosine, cAMP analogues, cAMP phosphodiesterase inhibitors, and calcium, which stimulate sperm motility, did not alter the level of phosphorylated PP1gamma2. However, calyculin A, which is an inhibitor of protein phosphatase subtypes PP1 and PP2A, significantly increases the level of phosphorylated PP1gamma2 in both caput and caudal epididymal spermatozoa. Partial purification by column chromatography showed that phosphorylated PP1gamma2 is catalytically active. Phosphorylated PP1gamma2 is the only spontaneously catalytically active form of the enzyme in caudal sperm extracts. Western blot analysis shows that the enzyme cyclin-dependent kinase 2, one of the enzymes that phosphorylates the consensus domain at the carboxy terminus in PP1 isoforms, is present in spermatozoa. Western blot analysis of proteins extracted from purified head and tail fragments of spermatozoa showed that phosphorylated PP1gamma2 is present predominantly in the sperm head. Fluorescence immunocytochemistry also showed that phosphorylated PP1gamma2 is present predominantly in the posterior region of the sperm head. The distinct subcellular localization and changes in its level during sperm maturation suggest a possible role for sperm phosphorylated PP1gamma2 in signaling events during fertilization.
...
PMID:Increased phosphorylation of a distinct subcellular pool of protein phosphatase, PP1gamma2, during epididymal sperm maturation. 1456 12

Cyclic AMP affects microvascular smooth muscle contraction and growth. Therefore, it is important to elucidate mechanisms regulating cyclic AMP production in microvascular smooth muscle. In this study, we determined whether several signal transduction pathways regulate receptor-induced cyclic AMP in isolated preglomerular microvessels and microvascular smooth muscle cells. Preglomerular microvessels were incubated with isoproterenol (beta-adrenoceptor agonist) and with and without U73122 (phospholipase C inhibitor), GF109203X (protein kinase C inhibitor), 1-butanol (phospholipase D inhibitor), CGP77675 (c-src inhibitor), HA1077 (Rho kinase inhibitor), Y27632 (Rho kinase inhibitor), LY294002 (phosphatidylinositol-3-kinase inhibitor), dipenyleneiodonium (NADPH oxidase inhibitor), or Tempol (superoxide dismutase mimetic). Cultured preglomerular microvascular smooth muscle cells were incubated with isoproterenol or forskolin (direct activator of adenylyl cyclase) and with or without U73122, C(2)-ceramide (phospholipase D inhibitor), or PP1 [src family inhibitor, 1-(1,1-dimethylethyl)-1-(4-methylphenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine]. All studies were conducted with 3-isobutyl-1-methylxanthine (broad-spectrum phosphodiesterase inhibitor) to eliminate changes in cyclic AMP degradation. In microvessels isoproterenol-induced cyclic AMP was not affected by Y27632, HA1007, LY294002, dipenylene-iodonium, or Tempol; was increased by U73122 and GF109203X; and was decreased by 1-butanol and CGP77675. In cells, U73122 increased and C(2)-ceramide and PP1 decreased isoproterenol-induced cyclic AMP. Forskolin-induced cyclic AMP was not altered. These results indicate that receptor-mediated activation of adenylyl cyclase is 1) not modulated by Rho kinase, phosphatidylinositol-3-kinase, NADPH oxidase, or superoxide; 2) is attenuated by phospholipase C and protein kinase C; and 3) is augmented by phospholipase D and src. Phospholipase C, phospholipase D, and src modulate receptor-induced cyclic AMP by affecting beta-adrenoreceptor/G protein/adenylyl cyclase coupling rather than by directly affecting adenylyl cyclase activity.
...
PMID:Modulation of cyclic AMP production by signal transduction pathways in preglomerular microvessels and microvascular smooth muscle cells. 1508 74

Phosphatidic acid (PA) has been recognized as a lipid second messenger, yet few cellular targets for PA have been identified. Previous work demonstrated PA as a potent and noncompetitive tight-binding inhibitor of the catalytic subunit (gamma isoform) of protein phosphatase-1 (PP1c gamma) in vitro. The high potency of inhibition, coupled with high specificity for PA over other phospholipids, suggested the presence of a high-affinity PA binding domain on PP1c gamma. In the current study, quantification of the binding interaction and identification of the binding domain were pursued. Surface plasmon resonance was employed to quantitate the interaction between PP1c gamma and immobilized mixed lipid vesicles of PA/phosphatidylcholine (PC) or PC alone. The data disclosed a high-affinity interaction with a KD measured in the low (1-40) nanomolar range, consistent with the range of Ki previously obtained from in vitro enzymatic assays. Next, identification of the segment of PP1 necessary for PA binding was determined using a deletion mutagenesis strategy. Binding assays revealed that PP1c gamma residues between 274 and 299 were required for the interaction with the lipid. When fusions of PP1c gamma fragments with green fluorescent protein (GFP) were generated, it was then determined that PP1c gamma residues 286-296 were sufficient to confer PA binding to GFP, a protein that does not interact with PA. The minimal PA binding domain of PP1c gamma lacked similarity to the previously described PA binding segments of Raf-1 kinase and cyclic-AMP phosphodiesterase 4A1. When these results were taken together with the known crystallographic structure of PP1, they identified a novel PA binding region on PP1c gamma that contains a unique loop-strand structural fold responsible for the interaction with PA.
...
PMID:Identification of a novel phosphatidic acid binding domain in protein phosphatase-1. 1620 49

The effects of dopamine (DA) and dopaminergic agonists and antagonists on ion transport were studied in isolated perfused gills of the crab Chasmagnathus granulatus. DA applied under steady state conditions (perfusion with hemolymph-like saline) produced a transient increase of the transepithelial potential difference (V(te)) from 2.2+/-0.2 to 4.8+/-0.3 mV, describing an initial cAMP-dependent stimulating phase followed by an inhibitory phase. Spiperone and domperidone (antagonists of D2-like DA receptors in vertebrates) completely blocked the response to DA, while the D1-like antagonist SCH23390 blocked only the inhibitory phase. Theophylline (phosphodiesterase inhibitor) and okadaic acid (protein phosphatases PP1 and PP2A inhibitor) were also able to block the inhibitory phase, suggesting that it depends on adenylyl cyclase inhibition and on protein phosphatases. When the gills were perfused with hypo-osmotic solution, or with the adenylyl cyclase activator forskolin, V(te) was increased several-fold. DA applied under these stimulated conditions partially reversed the V(te) increase by 54% and 25%, respectively. Similarly, the D1-like agonist, fenoldopam, produced a 33% reduction in the stimulated V(te). We propose that, in C. granulatus gills, DA stimulates adenylyl cyclase and therefore ion transport through D1-like receptors linked to a Gs protein, although they respond to antagonists that interact with D2-like receptors in vertebrates. The inhibitory phase seems to be mediated by D2-like receptors linked to a Gi/o protein, which inhibits adenylyl cyclase, although these receptors can be activated or blocked by agonists or antagonists that interact with D1-like receptors in vertebrates and insects.
...
PMID:Dopaminergic regulation of ion transport in gills of the euryhaline semiterrestrial crab Chasmagnathus granulatus: interaction between D1- and D2-like receptors. 1680 69

Phosphodiesterase 5 (PDE5) is one of eleven members of the mammalian phosphodiesterase family that hydrolyzes cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP). Best known as the target of the impotence drug sildenafil, PDE5 degrades cGMP in smooth muscle cells so as to maintain the contracted state of contractile organs such as the penis, blood vessels, uterus, and intestines. In addition, it regulates numerous other physiological processes such as neurogenesis and apoptosis. Like all other PDEs, PDE5 is dimeric; each subunit is approximately 100 kd in size and has two allosteric cGMP-binding sites and a catalytic domain. Protein kinase G (PKG)-mediated phosphorylation and allosteric cGMP binding upregulate PDE5 activity, while PP1 phosphatase-mediated dephosphorylation downregulates. Sildenafil and other selective inhibitors inhibit PDE5 by binding to the catalytic site. From two promoters a single PDE5A gene at human chromosome 4q26 encodes three alternatively spliced isoforms (PDE5A1-3) that differ in the N-terminus. The PDE5A promoter is located upstream of the three isoform-specific first exons (in the order of A1-A3-A2) and consists of a 139-bp core, a 308-bp upstream enhancer, and a 156-bp downstream enhancer. The weaker 182-bp PDE5A2 promoter is located between the A3- and A2-specific exons and contains an indispensable Sp1-binding sequence. Both promoters are responsive to cGMP or cAMP stimulation, and several studies have demonstrated regulation of PDE5 expression possibly through these promoters. Virtually all tissues and cell types express PDE5, with heart and cardiomyocytes being contentious. PDE5A1 and PDE5A2 are ubiquitous, but PDE5A3 is specific to smooth muscle.
...
PMID:Expression, distribution and regulation of phosphodiesterase 5. 1701 38

High levels of specific prolactin-releasing peptide (PrRP) binding sites have been found in the myocardium; however, the functional importance of PrRP in the regulation of cardiac function is unknown. In isolated perfused rat hearts, infusion of PrRP (1-100 nM) induced a dose-dependent positive inotropic effect. Inhibition of cAMP catabolism by IBMX, a phosphodiesterase inhibitor, failed to augment the contractile effect of PrRP. The protein phosphatase (PP1/PP2A) inhibitor calyculin A increased the inotropic response to PrRP, whereas the PP2A inhibitor okadaic acid had no effect. Ro32-0432, a protein kinase C alpha (PKC alpha) inhibitor, significantly enhanced the inotropic effect of PrRP as well as the phosphorylation of phospholamban at Ser-16. In conclusion, the present data define a hitherto unrecognized role for PrRP in the regulation of cardiovascular system by showing that PrRP exerts a direct positive inotropic effect. Moreover, our results suggest that the cAMP-independent inotropic response to PrRP is suppressed by concurrent activation of PKC alpha and PP1.
...
PMID:Prolactin-releasing peptide regulates cardiac contractility. 1961 82


1 2 Next >>

---