401
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Briley EM, Lolait SJ, Axelrod J, Felder CC. The cloned vasopressin V1a receptor stimulates phospholipase A2, phospholipase C, and phospholipase D through activation of receptor-operated calcium channels. Neuropeptides 1994; 27:63-74. [PMID: 7969820 DOI: 10.1016/0143-4179(94)90017-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Arginine vasopressin mediates its effects through vasopressin receptor activation and second messenger production. Recent cloning of the V1a receptor provided the opportunity to investigate the possible signal transduction pathways associated with this single vasopressin receptor subtype. When stably expressed in CHO cells, vasopressin stimulated several signal transduction pathways simultaneously including calcium influx, phospholipase A2, phospholipase C, and phospholipase D. Vasopressin-stimulated release of arachidonic acid, IP3 formation, and phosphatidylethanol formation (in the presence of 1% ethanol) were used as indexes of phospholipase A2, phospholipase C, and phospholipase D activation, respectively. V1a receptor-activation stimulated a peak followed by a sustained plateau phase of intracellular calcium. The plateau phase was dependent on extracellular calcium, insensitive to blockers of voltage sensitive calcium channels, blocked by heavy metals, and quenched when MnCl2 was present in the extracellular media. Removal of extracellular calcium blunted the release of IP3, and blocked the release of arachidonic acid and phosphatidylethanol indicating that these responses were at least in part regulated by receptor-operated calcium influx. Vasopressin-stimulated release of arachidonic acid and phosphatidylethanol were augmented with the phorbol ester PMA, and this augmentation was blocked by inhibitors of protein kinase C and absent with long-term PMA treatment. Vasopressin-stimulated IP3 release was inhibited with PMA and the inhibition reversed with protein kinase C inhibitors.
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Affiliation(s)
- E M Briley
- Laboratory of Cell Biology, National Institute of Mental Health, Bethesda, MD 20892
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402
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McKay RR, Miller K, Weckström M, Torkkeli P, Järvilehto M, Shortridge RD. The rpa (receptor potential absent) visual mutant of the blowfly (Calliphora erythrocephala) is deficient in phospholipase C in the eye. J Neurogenet 1994; 9:177-87. [PMID: 7965386 DOI: 10.3109/01677069409167278] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The rpa (receptor potential absent) mutation of the blowfly, Calliphora erythrocephala, reduces the light-evoked responses of photoreceptor cells and renders the fly blind. This phenotype is similar to the phenotype caused by norpA mutations in Drosophila which have been shown to occur within a gene encoding phospholipase C. In Western blots, norpA antiserum stains a protein in homogenates of wild-type Calliphora eye and head that is similar in molecular weight to the norpA protein. Very little staining of this protein is observed in similar homogenates of rpa mutant. Moreover, norpA antiserum strongly stains retina in immunohistochemical assays of wild-type adult head, but not in rpa mutant. Furthermore, eyes of rpa mutant have a reduced amount of phospholipase C activity compared to eye of wild-type Calliphora. These data suggest that the rpa mutation occurs in a phospholipase C gene of the blowfly that is homologous to the norpA gene of Drosophila.
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Affiliation(s)
- R R McKay
- Department of Biological Sciences, State University of New York, Buffalo 14260
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403
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Larsson C, Gustavsson L, Simonsson P, Bergman O, Alling C. Mechanisms of muscarinic receptor-stimulated expression of c-fos in SH-SY5Y cells. Eur J Pharmacol 1994; 268:19-28. [PMID: 7925609 DOI: 10.1016/0922-4106(94)90116-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In this study, the signal cascade transducing carbachol stimulation into c-fos expression in SH-SY5Y neuroblastoma cells was investigated. 1,2-Diacylglycerol formation and c-fos expression were mediated via stimulation of muscarinic M1 receptors and the first 5 min of receptor stimulation were critical for these events. Application of 1,2-dioctanoylglycerol induced c-fos expression and this, as well as carbachol-stimulated c-fos expression, was inhibited by protein kinase C inhibitors. Increasing the intracellular Ca2+ concentration had only small effects on c-fos expression. There was a dependency on extracellular Ca2+ for maximal c-fos expression and 1,2-diacylglycerol formation. The carbachol-stimulated c-fos expression was potentiated by application of the protein phosphatase inhibitor okadaic acid. These results demonstrate the importance of 1,2-diacylglycerol formation for muscarinic receptor-stimulated, protein kinase C-mediated c-fos expression in the SH-SY5Y cells and that this cascade is counteracted by an okadaic acid-sensitive protein phosphatase.
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Affiliation(s)
- C Larsson
- Department of Psychiatry and Neurochemistry, Lund University, Sweden
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404
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Tompkins TA, Moscarello MA. The mechanism of stimulation of brain phospholipase C-alpha by myelin basic protein involves specific interactions. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1206:208-14. [PMID: 7516186 DOI: 10.1016/0167-4838(94)90210-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The modulation of a brain phosphoinositide-specific phospholipase C-alpha activity was studied using a variety of compounds of different charge. Detergents such as sodium deoxycholate and cetyltrimethylammonium bromide stimulated the phospholipase C activity when used alone but when used together the effects were not additive. Spermine was an effective inhibitor of the enzyme activity while the cationic peptide, Melittin, had no effect. The inositol phosphates produced by hydrolysis with phosphoinositide-specific phospholipase C were inhibitory while diacylglycerol and inositol did not affect the phospholipase activity. Myelin basic protein, which was previously shown to stimulate phospholipase C activity by 2.5-fold, did not interact with the anionic inositol phosphatases to any significant extent. Thus we concluded that the mechanism of stimulation was not due to relief of product inhibition. Crosslinking studies with the photoactivatable reagent, N-hydroxysuccinimidyl-4-azidosalicylic acid, showed that peptide 24-33 of myelin basic protein, which stimulated the activity almost as much as the native protein, interacted specifically with the phospholipase C. Thus the mechanism by which myelin basic protein stimulated the enzyme appeared to be through specific protein-protein interaction.
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Affiliation(s)
- T A Tompkins
- Department of Molecular Biology and Genetics, University of Guelph, Ont., Canada
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405
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Abstract
Antigen and cytokine receptors induce rapid tyrosine phosphorylation of receptor subunits, other membrane proteins, and signaling components. Each receptor induces phosphorylation of a number of proteins. Although there is often overlap between targets of different receptors, any given receptor only induces phosphorylation of a subset of possible targets. How this choice of targets is achieved for these receptors is not yet understood. The cellular events downstream of some signaling components are beginning to come into view. Recent progress in these areas is discussed.
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Affiliation(s)
- A L DeFranco
- GW Hooper Foundation, University of California, San Francisco 94143-0552
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406
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Kow LM, Mobbs CV, Pfaff DW. Roles of second-messenger systems and neuronal activity in the regulation of lordosis by neurotransmitters, neuropeptides, and estrogen: a review. Neurosci Biobehav Rev 1994; 18:251-68. [PMID: 7914686 DOI: 10.1016/0149-7634(94)90028-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Many neurotransmitters and neuropeptides can affect the rodent feminine sexual behavior, lordosis, when administered in the ventromedial hypothalamus (VMH), midbrain central gray (MCG), or other brain regions. A survey of the electrophysiological and biochemical actions of these neural agents revealed that there is a very consistent association between lordosis facilitation with both the activation of the phosphoinositide (PI) pathway and the excitation of VMH and MCG neurons. In contrast, lordosis inhibition is associated, less consistently, with alterations of the adenylate cyclase (AC) system and the inhibition of neuronal activity. The findings that lordosis could be facilitated by going beyond membrane receptors and directly activating the PI pathway, suggest that this second-messenger pathway is a common mediator for the lordosis-facilitating agents. Furthermore, as in the case of stimulating membrane receptors, direct activation of this common mediator also requires estrogen priming for lordosis facilitation. Therefore, it is likely that the PI pathway is modulated by estrogen in the permissive action of estrogen priming. Indeed, a literature review shows that estrogen can affect selective isozymes of key enzyme families of the PI pathway at various levels. Such selective modulations, at several levels, could easily alter the course of a PI cascade; thence, the eventual functional outcome. These findings prompt us to propose that estrogen enables lordosis to be facilitated by a selective modulation of the PI pathway.
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Affiliation(s)
- L M Kow
- Rockefeller University, Laboratory of Neurobiology and Behavior, New York, NY 10021
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407
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Banno Y, Okano Y, Nozawa Y. Thrombin-mediated phosphoinositide hydrolysis in Chinese hamster ovary cells overexpressing phospholipase C-delta 1. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)40758-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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408
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Milting H, Heilmeyer LM, Thieleczek R. Phosphoinositides in membranes that build up the triads of rabbit skeletal muscle. FEBS Lett 1994; 345:211-8. [PMID: 8200458 DOI: 10.1016/0014-5793(94)00440-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The total membrane concentrations of PtdIns, PtdIns4P, and PtdIns(4,5)P2 contribute to the functional capacity of the Ins(1,4,5)P3 signalling system which is operating in skeletal muscle but the function of which is still unknown. Total amounts of these phosphoinositides have been determined in purified membranes of transverse tubules (TT) and terminal cisternae (TC) of the sarcoplasmic reticulum (SR) of rabbit skeletal muscle. PtdIns and PtdIns4P have been detected in both membrane systems whereas PtdIns(4,5)P2 (290 mumol/mol phospholipid) is confined only to TT. A much greater pool of PtdIns(4,5)P2 seems, however, to be located in the sarcolemma away from the triadic junction.
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Affiliation(s)
- H Milting
- Institut für Physiologische Chemie, Ruhr-Universität, Bochum, Germany
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409
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de Mazancourt P, Carneiro EM, Atwater I, Boschero AC. Prolactin treatment increases GLUT2 but not the G protein subunit content in cell membranes from cultured neonatal rat islets. FEBS Lett 1994; 343:137-40. [PMID: 8168618 DOI: 10.1016/0014-5793(94)80305-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Neonatal rat islets exhibit a reduced secretory response to glucose, compared to adult rat islets. The maturation of the secretory response is stimulated by prolactin (PRL). We show here by immunoblot analysis that PRL increases the beta-cell/liver glucose transporter GLUT2 in membrane fractions from cultured neonatal rat islets. This increase (+86%) may explain, at least in part, the development of a mature glucose response. G proteins modulate insulin secretion from pancreatic beta-cells. We show here by immunoblot analysis that, in contrast to the effect on GLUT2, PRL treatment does not modify the G protein subunits alpha i2, alpha i3, alpha o, alpha s, alpha q and beta 35 and beta 36, in cultured neonatal islets.
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Affiliation(s)
- P de Mazancourt
- Laboratoire Central de Biologie, Centre Hospitalier Intercommunal Leon Touhladjian, Poissy, France
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410
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Abstract
PC hydrolysis by PLA2, PLC or PLD is a widespread response elicited by most growth factors, cytokines, neurotransmitters, hormones and other extracellular signals. The mechanisms can involve G-proteins, PKC, Ca2+ and tyrosine kinase activities. Although an agonist-responsive cytosolic PLA2 has been purified, cloned and sequenced, the agonist-responsive form(s) of PC-PLC has not been identified and no form of PC-PLD has been purified or cloned. Regulation of PLA2 by Ca2+ and MAPK is well established and involves membrane translocation and phosphorylation, respectively. PKC regulation of the enzyme in intact cells is probably mediated by MAPK. The question of G-protein control of PLA2 remains controversial since the nature of the G-protein is unknown and it is not established that its interaction with the enzyme is direct or not. Growth factor regulation of PLA2 involves tyrosine kinase activity, but not necessarily PKC. It may be mediated by MAPK. The physiological significance of PLA2 activation is undoubtedly related to the release of AA for eicosanoid production, but the LPC formed may have actions also. There is much evidence that PKC regulates PC-PLC and PC-PLD and this is probably a major mechanism by which agonists that promote PI hydrolysis secondarily activate PC hydrolysis. Since no agonist-responsive forms of either phospholipase have been isolated, it is not clear that PKC exerts its effects directly on the enzymes. Although it is assumed that a phosphorylation mechanism is involved, this may not be the case, and regulation may be by protein-protein interactions. G-protein control of PC-PLD is well-established, although, again, it has not been demonstrated that this is direct, and the nature of the G-protein(s) involved is unknown. In some cell types, there is evidence of the participation of a soluble protein, which may be a low Mr GTP-binding protein. What role this plays in the activation of PC-PLD is obscure. Agonist activation of PC hydrolysis in cells is usually Ca(2+)-dependent, but the step at which Ca2+ is involved is unclear, since PC-PLD and PC-PLC per se are not influenced by physiological concentrations of the ion. Most growth factors promote PC hydrolysis and this is mainly due to activation of PKC as a result of PI breakdown. However, in some cases, PC breakdown occurs in the absence of PI hydrolysis, implying another mechanism that does not involve PI-derived DAG.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J H Exton
- Howard Hughes Medical Institute, Nashville, TN
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411
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Varticovski L, Harrison-Findik D, Keeler ML, Susa M. Role of PI 3-kinase in mitogenesis. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1226:1-11. [PMID: 7512386 DOI: 10.1016/0925-4439(94)90051-5] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- L Varticovski
- Department of Medicine, St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, MA 02135
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412
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Stephens L, Smrcka A, Cooke FT, Jackson TR, Sternweis PC, Hawkins PT. A novel phosphoinositide 3 kinase activity in myeloid-derived cells is activated by G protein beta gamma subunits. Cell 1994; 77:83-93. [PMID: 8156600 DOI: 10.1016/0092-8674(94)90237-2] [Citation(s) in RCA: 506] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Phosphoinositide 3 kinase (PI3K) is a key signaling enzyme implicated in receptor-stimulated mitogenesis, oxidative bursting in neutrophils, membrane ruffling, and glucose uptake. A PI3K has already been purified, cloned, and shown to be regulated by receptors that act via tyrosine kinase-dependent regulatory mechanisms. We report that an immunologically, pharmacologically, and chromatographically distinct form of PI3K activity present in neutrophils and U937 cells is specifically activated by G protein beta gamma subunits. This data suggests PI3Ks conform to the paradigm set by receptor regulation of phosphoinositidase Cs: different receptor transduction systems specifically regulate dedicated isoforms of effector protein.
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Affiliation(s)
- L Stephens
- Agricultural and Food Research Council, Babraham Institute, Cambridge, England
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413
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Abstract
Intracellular signalling pathways mediating the effects of oncogenes on cell growth and transformation offer novel targets for the development of anticancer drugs. With this approach, it may be sufficient to target a component of the signalling pathway activated by the oncogene rather than the oncogene product itself. In this review, the abilities of some antiproliferative drugs to inhibit signalling targets are considered. There are some anticancer drugs already in clinical trial that may act by inhibiting signalling targets, as well as drugs in preclinical development. Some problems that may be encountered in developing this new class of anticancer drugs are discussed.
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Affiliation(s)
- G Powis
- Arizona Cancer Center, University of Arizona Health Sciences Center, Tucson 85724
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414
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Tsutsumi T, Kobayashi T, Ueda H, Yamauchi E, Watanabe S, Okuyama H. Lysophosphoinositide-specific phospholipase C in rat brain synaptic plasma membranes. Neurochem Res 1994; 19:399-406. [PMID: 8065496 DOI: 10.1007/bf00967316] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A membrane preparation from rat brain catalyzed the hydrolysis of [2-3H]glycerol-labeled lysophosphatidylinositol (lysoPI) to yield monoacylglycerol (MG) and inositolphosphates. This phospholipase C activity had an optimal pH of 8.2. The membrane preparation did not require the addition of Ca2+ for its maximum activity, but the activity was inhibited by addition of 0.1 mM EDTA to the assay mixture and was restored by simultaneous addition of 0.2 mM Ca2+. The activity was found to be localized in synaptic plasma membranes prepared by Ficoll and Percoll density gradients. The phospholipase C was highly specific for lysoPI; diacylglycerol formation from phosphatidylinositol, and MG formation from lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylserine were below 5% of that observed with lysoPI under the conditions used. We concluded that there is a pathway for phosphatidylinositol metabolism in brain synaptic membranes which is different from the well-characterized phosphoinositide-specific phospholipase C pathway.
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Affiliation(s)
- T Tsutsumi
- Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Nagoya City University, Japan
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415
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Affiliation(s)
- M DeVivo
- Department of Pharmacology, Mount Sinai School of Medicine, City University of New York, NY 10029
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416
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Marrero M, Paxton W, Duff J, Berk B, Bernstein K. Angiotensin II stimulates tyrosine phosphorylation of phospholipase C-gamma 1 in vascular smooth muscle cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34147-9] [Citation(s) in RCA: 166] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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417
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418
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Banno Y, Asano T, Nozawa Y. Proteolytic modification of membrane-associated phospholipase C-beta by mu-calpain enhances its activation by G-protein beta gamma subunits in human platelets. FEBS Lett 1994; 340:185-8. [PMID: 8131842 DOI: 10.1016/0014-5793(94)80134-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Membrane-associated phosphoinositide-phospholipase C (PI-PLC)-beta (150 kDa) and its truncated forms (100 kDa and 45 kDa) were purified from human platelets. The 100 kDa PI-PLC-beta was found to be activated to a greater extent by brain G-protein beta gamma subunits compared to the intact 150 kDa enzyme. Furthermore, treatment with mu-calpain of the intact PI-PLC-beta (150 kDa) caused a marked augmentation of its activation by beta gamma subunits. This enhanced PLC activation by beta gamma subunits was due to truncation by mu-calpain, producing a 100 kDa PI-PLC, but not by another protease, thrombin.
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Affiliation(s)
- Y Banno
- Department of Biochemistry, Gifu University School of Medicine, Japan
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419
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420
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Uyama Y, Muraki K, Walsh MP, Imaizumi Y, Watanabe M. Tetrahexylammonium ions increase Ca2+ sensitivity of contraction of guinea-pig ileal smooth muscle. Pflugers Arch 1994; 426:363-70. [PMID: 8015886 DOI: 10.1007/bf00388298] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Effects of tetraalkylammonium ions, having tetraalkyl chains of increasing length from ethyl to octyl, on inositol-trisphosphate (InsP3)-induced Ca2+ release and contractile mechanics were examined in guinea-pig skinned ileal smooth muscle longitudinal strips. Although tetrahexylammonium ions (THexA) appeared to be the most potent inhibitor of Ca2+ release among the tetraalkylammonium ions examined, an additional and more prominent effect was found, i.e., the contraction induced by Ca2+ release showed a large sustained component in the presence of THexA. Potentiation of the contraction by THexA (above 30 microM) was also observed in skinned fibers in which the sarcoplasmic reticulum function was destroyed by treatment with A23187. The potentiating effect of THexA was the most potent by far among the tetraalkylammonium ions examined and was elicited by Ca(2+)-dependent and GTP-binding-protein-independent mechanisms. The potentiation was not due to activation of myosin light-chain kinase. The selective inhibitors of myosin light-chain kinase, protein kinase C and calmodulin reduced THexA-induced potentiation of contraction only at concentrations above 30 microM, at which non-specific effects are likely. Furthermore, relaxation induced by changing pCa from 4.5 to 8.5 was not affected by 1 mM THexA, suggesting that the potentiating effect is not mainly due to inhibition of myosin light-chain phosphatase. In conclusion, ThexA sensitizes guinea-pig skinned ileal smooth muscle to Ca2+ in a structure-selective manner. This sensitization appears not to be mediated mainly by a GTP-binding protein, by activation of myosin light-chain kinase or protein kinase C, by enhanced Ca2+ binding to calmodulin, or by inhibition of myosin light-chain phosphatase.
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Affiliation(s)
- Y Uyama
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University, Japan
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421
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York J, Majerus P. Nuclear phosphatidylinositols decrease during S-phase of the cell cycle in HeLa cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37126-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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422
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Dhar A, Shukla S. Electrotransjection of pp60v-src monoclonal antibody inhibits activation of phospholipase C in platelets. A new mechanism for platelet-activating factor responses. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37085-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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423
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Sphingosine-1-phosphate, a putative second messenger, mobilizes calcium from internal stores via an inositol trisphosphate-independent pathway. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41846-1] [Citation(s) in RCA: 214] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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424
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Nomoto K, Morotomi M, Miyake M, Xu DB, LoGerfo PP, Weinstein IB. The effects of bile acids on phospholipase C activity in extracts of normal human colon mucosa and primary colon tumors. Mol Carcinog 1994; 9:87-94. [PMID: 8142013 DOI: 10.1002/mc.2940090206] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Phospholipase C (PLC) activity and its response to stimulation by bile acids was assayed in cellular extracts from 16 primary human colon tumors of various Duke's stages and paired adjacent normal mucosal samples. In the absence of bile acid, there was negligible degradation of phosphatidylinositol (PI) 1-stearoyl-2-[14C]-arachiodonoyl by tumor or normal tissue, but the addition of deoxycholic acid (DCA) or taurocholic acid (TCA) resulted in concentration-dependent and time-dependent stimulation of diacylglycerol (DAG) formation at optimal concentrations of 2 mM DCA and 4 mM TCA. Triton X-100 (0.125-1.0%) inhibited rather than enhanced the PI-degrading activity of these extracts, indicating that the stimulatory effects of DCA and TCA were not simply due to a detergent effect. Under the same assay conditions there was only a small amount of labeled monoacylglycerol or free arachidonic acid produced by extracts incubated in the absence or presence of DCA or TCA. No major differences in DAG production from PI were seen between paired samples of normal colon mucosa and primary colon tumors, in assays done in the presence of 2 mM TCA. Extracts from tumors in the distal part of the colon had higher activity than those from the proximal colon. This was also true for the extent of release of free arachidonic acid from labeled PI. Under the same conditions, labeled phosphatidylcholine or phosphatidylethanolamine did not serve as substrates for the colon mucosa or tumor extracts. Nor was there significant hydrolysis of the labeled DAG (1-stearoyl-2-14C-arachidonoylglycerol) by normal colon mucosa or tumor extracts, in the absence or presence of DCA or TCA. On the other hand, a low level of DAG lipase activity was detected in the presence of Triton X-100. These findings provide the first evidence that normal human colon mucosa and primary colon tumors contain a PI-specific PLC activity that is markedly stimulated by bile acids. Our results also suggest that bile acids may enhance colon carcinogenesis by acting on this enzyme system, thereby influencing signal transduction pathways in the target cells.
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Affiliation(s)
- K Nomoto
- Columbia-Presbyterian Cancer Center, Columbia University College of Physicians and Surgeons, New York, New York
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425
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Lee J, Pilch PF. The insulin receptor: structure, function, and signaling. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:C319-34. [PMID: 8141246 DOI: 10.1152/ajpcell.1994.266.2.c319] [Citation(s) in RCA: 262] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The insulin receptor is a member of the ligand-activated receptor and tyrosine kinase family of transmembrane signaling proteins that collectively are fundamentally important regulators of cell differentiation, growth, and metabolism. The insulin receptor has a number of unique physiological and biochemical properties that distinguish it from other members of this large well-studied receptor family. The main physiological role of the insulin receptor appears to be metabolic regulation, whereas all other receptor tyrosine kinases are engaged in regulating cell growth and/or differentiation. Receptor tyrosine kinases are allosterically regulated by their cognate ligands and function as dimers. In all cases but the insulin receptor (and 2 closely related receptors), these dimers are noncovalent, but insulin receptors are covalently maintained as functional dimers by disulfide bonds. The initial response to the ligand is receptor autophosphorylation for all receptor tyrosine kinases. In most cases, this results in receptor association of effector molecules that have unique recognition domains for phosphotyrosine residues and whose binding to these results in a biological response. For the insulin receptor, this does not occur; rather, it phosphorylates a large substrate protein that, in turn, engages effector molecules. Possible reasons for these differences are discussed in this review. The chemistry of insulin is very well characterized because of possible therapeutic interventions in diabetes using insulin derivatives. This has allowed the synthesis of many insulin derivatives, and we review our recent exploitation of one such derivative to understand the biochemistry of the interaction of this ligand with the receptor and to dissect the complicated steps of ligand-induced insulin receptor autophosphorylation. We note possible future directions in the study of the insulin receptor and its intracellular signaling pathway(s).
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Affiliation(s)
- J Lee
- Department of Biochemistry, Boston University, School of Medicine, Massachusetts 02118
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426
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Abstract
Phospholipases and protein kinases are critical for the intracellular transmission and amplification of signals induced by extracellular ligands. Chemotactic activation of phagocytes through G protein coupled receptors leads to inflammatory responses of the immune cells. Downstream of G proteins, phospholipases generate precursors for eicosanoid synthesis and are involved in the functional responses. Recently, the molecular characterization of specific enzymes of the signalling cascades has gained much attention in research.
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Affiliation(s)
- M Thelen
- Theodor Kocher Institute, University of Bern, Switzerland
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427
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Affiliation(s)
- K S Bruzik
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago 60612
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428
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Regulation of phosphatidylinositol 4-kinase by the protein activator PIK-A49. Activation requires phosphorylation of PIK-A49. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41938-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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429
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Chao C, Laulederkind S, Ballou L. Sphingosine-mediated phosphatidylinositol metabolism and calcium mobilization. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37539-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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430
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Bothmer J, Jolles J. Phosphoinositide metabolism, aging and Alzheimer's disease. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1225:111-24. [PMID: 8280779 DOI: 10.1016/0925-4439(94)90068-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- J Bothmer
- Department of Neuropsychology and Psychobiology, University of Limburg, Maastricht, The Netherlands
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431
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Hirata M, Murad F. Interrelationships of cyclic GMP, inositol phosphates, and calcium. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1994; 26:195-216. [PMID: 8038104 DOI: 10.1016/s1054-3589(08)60055-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- M Hirata
- Department of Biochemistry, Faculty of Dentistry, Kyushu University, Fukuoka, Japan
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432
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Cockcroft S, Thomas GM, Cunningham E, Ball A. Use of cytosol-depleted HL-60 cells for reconstitution studies of G-protein-regulated phosphoinositide-specific phospholipase C-beta isozymes. Methods Enzymol 1994; 238:154-68. [PMID: 7799782 DOI: 10.1016/0076-6879(94)38014-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- S Cockcroft
- Department of Physiology, University College London, United Kingdom
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433
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Abstract
Heterotrimeric GTP-binding proteins (G proteins) that are made up of alpha and beta gamma subunits couple many kinds of cell-surface receptors to intracellular effector enzymes or ion channels. Every cell contains several types of receptors, G proteins, and effectors. The specificity with which G protein subunits interact with receptors and effectors defines the range of responses a cell is able to make to an external signal. Thus, the G proteins act as a critical control point that determines whether a signal spreads through several pathways or is focused to a single pathway. In this review, I will summarize some features of the structure and function of mammalian G protein subunits, discuss the role of both alpha and beta gamma subunits in regulation of effectors, the role of the beta gamma subunit in macromolecular assembly, and the mechanisms that might make some responses extremely specific and others rather diffuse.
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Affiliation(s)
- E J Neer
- Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
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434
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Waldo GL, Boyer JL, Harden TK. Purification of phospholipase C-activating G protein, G11, from turkey erythrocytes. Methods Enzymol 1994; 237:182-91. [PMID: 7934996 DOI: 10.1016/s0076-6879(94)37062-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G L Waldo
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill 27599
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435
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Blank JL, Exton JH. Purification of 110 kDa phosphoinositide phospholipase C activated by G-protein beta gamma subunits. Methods Enzymol 1994; 238:237-44. [PMID: 7799789 DOI: 10.1016/0076-6879(94)38021-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J L Blank
- Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206
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436
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Waldo GL, Morris AJ, Harden TK. Purification of G-protein-regulated phospholipase C from turkey erythrocytes. Methods Enzymol 1994; 238:195-207. [PMID: 7799785 DOI: 10.1016/0076-6879(94)38017-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G L Waldo
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill 27599
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437
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D-myo-inositol 1,4,5-trisphosphate inhibits binding of phospholipase C-delta 1 to bilayer membranes. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42118-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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438
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Lyons J. Identification of mutant forms of G-protein alpha subunits in human neoplasia by polymerase chain reaction-based techniques. Methods Enzymol 1994; 237:295-308. [PMID: 7935005 DOI: 10.1016/s0076-6879(94)37070-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Lyons
- Department of Drug Discovery, Onyx Pharmaceuticals, Richmond, California 94806
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439
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Abstract
By virtue of their biological simplicity and widespread availability, platelets frequently have been used as a model system to study signal transduction. Such studies have revealed that changes in intracellular free calcium concentration are central to platelet functioning. The following article reviews current concepts of platelet structure and function, with particular emphasis on the mechanisms involved in platelet Ca2+ signalling.
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Affiliation(s)
- P Sargeant
- Physiological Laboratory, Cambridge University, U.K
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440
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Thomas GM, Cunningham E, Cockcroft S. Purification of phosphatidylinositol transfer protein from brain cytosol for reconstituting G-protein-regulated phosphoinositide-specific phospholipase C-beta isozymes. Methods Enzymol 1994; 238:168-81. [PMID: 7799783 DOI: 10.1016/0076-6879(94)38015-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G M Thomas
- Department of Physiology, University College London, United Kingdom
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441
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Affiliation(s)
- P Gierschik
- Department of Pharmacology and Toxicology, University of Ulm, Germany
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442
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Affiliation(s)
- M De Vivo
- Department of Pharmacology, Mount Sinai School of Medicine, City University of New York, New York 10029
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443
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Clyman RI, Peters KG, Chen YQ, Escobedo J, Williams LT, Ives HE, Wilson E. Phospholipase C gamma activation, phosphotidylinositol hydrolysis, and calcium mobilization are not required for FGF receptor-mediated chemotaxis. CELL ADHESION AND COMMUNICATION 1994; 1:333-42. [PMID: 8081884 DOI: 10.3109/15419069409097264] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Basic fibroblast growth factor (FGF) is a potent angiogenic factor that stimulates several cell types to migrate along a chemotactic gradient. Most chemoattractant receptors appear to share a common mechanism that involves activation of phospholipase C (PLC), hydrolysis of phosphotidylinositol, and mobilization of intracellular calcium. We transfected two different cell lines with either human FGF receptor-1 cDNA or chimeric FGF receptor cDNA. Ligand stimulation induced chemotaxis, activation of PLC gamma, phosphotidylinositol hydrolysis, and calcium mobilization in both wild-type receptor cell lines. No such response was elicited in control cells. Mutation of the two fibroblast growth factor receptors at residue 766, replacing tyrosine with phenylalanine, made the receptors incapable of associating with and activating PLC gamma following ligand stimulation. These mutant receptors also failed to mediate phosphotidylinositol hydrolysis and calcium mobilization. However, cells transfected with the mutant fibroblast growth factor receptors were as chemotactically responsive to the appropriate ligand as were cells transfected with the wild-type receptors. These findings demonstrate that the ability of the fibroblast growth factor receptor to promote chemotaxis is not dependent on increased activation of PLC gamma, increased hydrolysis of phosphotidylinositol, or increased global mobilization of calcium.
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Affiliation(s)
- R I Clyman
- Department of Pediatrics, University of California, San Francisco 94143
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444
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Abstract
BACKGROUND Phospholipase C isozymes (PLC) play a role in ligand-mediated signal transduction for cellular activity, such as proliferation and differentiation. However, the biologic significance of their molecules in carcinogenesis or tumor progression is yet to be determined. METHODS Using PLC isozyme-specific antibodies, the relative content of PLC in human colorectal carcinomas and in normal colonic mucosa was examined. RESULTS Immunoreactive analysis revealed considerably higher levels of PLC-gamma 1 protein in 15 of 17 colorectal carcinomas and little difference in PLC-beta 1 or PLC-gamma 1 content compared with normal colorectal tissues. By radioimmunoassay and Western blotting, PLC-gamma 1 showed three-fold to fourfold more expression in carcinomas than that in normal tissues. CONCLUSION Although factors that might influence the level of PLC-gamma 1 expression in colorectal carcinomas still remain obscure, the fact that most colorectal carcinomas display elevated levels of PLC-gamma 1 expression implies that PLC-gamma 1 may play an important role in proliferation of colorectal carcinoma cells.
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Affiliation(s)
- D Y Noh
- Laboratory of Cell Biology, Seoul National University College of Medicine, Korea
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445
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Mathew J, Eichberg J. Guanosine-5'-(3-O-thio)triphosphate-mediated stimulation of phosphoinositidase C in solubilized rat peripheral nerve myelin and its alteration in streptozotocin-induced diabetes. J Neurosci Res 1994; 37:83-91. [PMID: 8145305 DOI: 10.1002/jnr.490370111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The regulation of phosphoinositidase C (PIC) activity by guanosine-5'-(3-O-thio)triphosphate (GTP gamma S) was characterized in a cholate-solubilized peripheral myelin-enriched fraction from rat sciatic nerve. The GTP analog maximally enhanced PIC-catalyzed hydrolysis of exogenous phosphatidylinositol-4,5-bisphosphate (PIP2) in a dose-dependent manner only within a narrow range of cholate concentrations. Maximal stimulation was attained at 0.6 microM GTP gamma S and could be completely prevented by 1 microM guanosine-5'-(2-O-thio)diphosphate. Neither adenylyl-imidodiphosphate nor adenosine triphosphate (ATP) enhanced PIC activity. Carbamoylcholine (1 mM) added together with GTP gamma S increased the extent of PIP2 hydrolysis over that elicited by GTP gamma S alone and this stimulation was blocked by the muscarinic receptor antagonist, atropine (50 microM). In detergent-solubilized myelin preparations from streptozotocin-induced diabetic rats, a higher concentration of the guanine nucleotide analog was required to achieve stimulation comparable to that obtained with corresponding preparations from normal animals. These results suggest that sciatic nerve myelin possesses muscarinic receptors coupled via a GTP-binding protein to PIC and that this system can be reconstituted in detergent-solubilized extracts. It is possible that the function of G proteins in cell signaling is impaired in experimental diabetic neuropathy.
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Affiliation(s)
- J Mathew
- Department of Biochemical and Biophysical Sciences, University of Houston, Texas
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446
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Parthasarathy L, Vadnal RE, Parthasarathy R, Devi CS. Biochemical and molecular properties of lithium-sensitive myo-inositol monophosphatase. Life Sci 1994; 54:1127-42. [PMID: 8152337 DOI: 10.1016/0024-3205(94)00835-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Myo-inositol monophosphatase is a pivotal enzyme of the inositol second messenger system which is specifically inhibited by therapeutic levels of lithium salts, implicating inhibition of this enzyme as a potential site of its action in bipolar disease. This enzyme has a native molecular weight of 59,000, and has traditionally been found in the cytosolic fraction, although a membrane-bound form has also been identified. Possessing two identical subunits, this enzyme hydrolyzes those monophosphates which are equatorially located within the inositol ring, and several nucleoside monophosphates phosphorylated at the 2-position. Each subunit of the native enzyme contains an active site with unusually large caverns as revealed by crystallographic studies, which may explain the accommodation of these structurally unrelated substrates. We have suggested that the uncompetitive inhibition of this phosphatase by lithium ions may prevent the formation of an enzyme-bound non-isomeric (meso) intermediate, Mg(2+)-inositol 1,3 or 4,6 cyclic monophosphate when this enzyme hydrolyzes its respective isomeric substrates.
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447
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Powis G, Gallegos A, Abraham RT, Ashendel CL, Zalkow LH, Grindey GB, Bonjouklian R. Increased intracellular Ca2+ signaling caused by the antitumor agent helenalin and its analogues. Cancer Chemother Pharmacol 1994; 34:344-50. [PMID: 8033301 DOI: 10.1007/bf00686043] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The antitumor sesquiterpene lactone helenalin, which is found in species of the plant genus Helenium, caused a marked potentiation of the increases in intracellular free Ca2+ concentration ([Ca2+]i) produced by mitogens such as vasopressin, bradykinin, and platelet-derived growth factor in Swiss mouse 3T3 fibroblasts. Removing external Ca2+ partly attenuated the increased [Ca2+]i responses caused by helenalin. The increased [Ca2+]i responses occurred at concentrations of helenalin that inhibited cell proliferation. At higher concentrations, helenalin inhibited the [Ca2+]i responses. No change in resting [Ca2+]i was caused by helenalin even at high concentrations. Other helenalin analogues also increased the [Ca2+]i response. Helenalin did not inhibit protein kinase C (PKC) and PKC appeared to play a minor role in the effects of helenalin on [Ca2+]i responses in intact cells. Studies with saponin-permeabilized HT-29 human colon carcinosarcoma cells indicated that helenalin caused an increased accumulation of Ca2+ into nonmitochondrial stores and that the potentiating effect of helenalin on mitogen-stimulated [Ca2+]i responses was due in part to an increase in the inositol-(1,4,5)-trisphosphate-mediated release of Ca2+ from these stores.
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Affiliation(s)
- G Powis
- Arizona Cancer Center, University of Arizona, Tucson 85724
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448
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Fukami K, Endo T, Imamura M, Takenawa T. alpha-Actinin and vinculin are PIP2-binding proteins involved in signaling by tyrosine kinase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42287-3] [Citation(s) in RCA: 144] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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449
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Affiliation(s)
- D Y Jhon
- Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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450
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Selective activation of phospholipase C by recombinant G-protein alpha- and beta gamma-subunits. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42015-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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