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Kim RJ, Kim HJ, Shim D, Suh MC. Molecular and biochemical characterizations of the monoacylglycerol lipase gene family of Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 85:758-71. [PMID: 26932457 DOI: 10.1111/tpj.13146] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 02/09/2016] [Accepted: 02/15/2016] [Indexed: 05/23/2023]
Abstract
Monoacylglycerol lipase (MAGL) catalyzes the last step of triacylglycerol breakdown, which is the hydrolysis of monoacylglycerol (MAG) to fatty acid and glycerol. Arabidopsis harbors over 270 genes annotated as 'lipase', the largest class of acyl lipid metabolism genes that have not been characterized experimentally. In this study, computational modeling suggested that 16 Arabidopsis putative MAGLs (AtMAGLs) have a three-dimensional structure that is similar to a human MAGL. Heterologous expression and enzyme assays indicated that 11 of the 16 encoded proteins indeed possess MAG lipase activity. Additionally, AtMAGL4 displayed hydrolase activity with lysophosphatidylcholine and lysophosphatidylethanolamine (LPE) substrates and AtMAGL1 and 2 utilized LPE as a substrate. All recombinant AtMAGLs preferred MAG substrates with unsaturated fatty acids over saturated fatty acids and AtMAGL8 exhibited the highest hydrolase activities with MAG containing 20:1 fatty acids. Except for AtMAGL4, -14 and -16, all AtMAGLs showed similar activity with both sn-1 and sn-2 MAG isomers. Spatial, temporal and stress-induced expression of the 16 AtMAGL genes was analyzed by transcriptome analyses. AtMAGL:eYFP fusion proteins provided initial evidence that AtMAGL1, -3, -6, -7, -8, -11, -13, -14 and -16 are targeted to the endoplasmic reticulum and/or Golgi network, AtMAGL10, -12 and -15 to the cytosol and AtMAGL2, -4 and -5 to the chloroplasts. Furthermore, AtMAGL8 was associated with the surface of oil bodies in germinating seeds and leaves accumulating oil bodies. This study provides the broad characterization of one of the least well-understood groups of Arabidopsis lipid-related enzymes and will be useful for better understanding their roles in planta.
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Affiliation(s)
- Ryeo Jin Kim
- Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 500-757, Korea
| | - Hae Jin Kim
- Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 500-757, Korea
| | - Donghwan Shim
- Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 500-757, Korea
| | - Mi Chung Suh
- Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 500-757, Korea
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2
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Douglass JD, Zhou YX, Wu A, Zadroga JA, Gajda AM, Lackey AI, Lang W, Chevalier KM, Sutton SW, Zhang SP, Flores CM, Connelly MA, Storch J. Global deletion of MGL in mice delays lipid absorption and alters energy homeostasis and diet-induced obesity. J Lipid Res 2015; 56:1153-71. [PMID: 25842377 DOI: 10.1194/jlr.m058586] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 11/20/2022] Open
Abstract
Monoacylglycerol lipase (MGL) is a ubiquitously expressed enzyme that catalyzes the hydrolysis of monoacylglycerols (MGs) to yield FFAs and glycerol. MGL contributes to energy homeostasis through the mobilization of fat stores and also via the degradation of the endocannabinoid 2-arachidonoyl glycerol. To further examine the role of MG metabolism in energy homeostasis, MGL(-/-) mice were fed either a 10% (kilocalories) low-fat diet (LFD) or a 45% (kilocalories) high-fat diet (HFD) for 12 weeks. Profound increases of MG species in the MGL(-/-) mice compared with WT control mice were found. Weight gain over the 12 weeks was blunted in both diet groups. MGL(-/-) mice were leaner than WT mice at both baseline and after 12 weeks of LFD feeding. Circulating lipids were decreased in HFD-fed MGL(-/-) mice, as were the levels of several plasma peptides involved in glucose homeostasis and energy balance. Interestingly, MGL(-/-) mice had markedly reduced intestinal TG secretion following an oral fat challenge, suggesting delayed lipid absorption. Overall, the results indicate that global MGL deletion leads to systemic changes that produce a leaner phenotype and an improved serum metabolic profile.
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Affiliation(s)
- John D Douglass
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Yin Xiu Zhou
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Amy Wu
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - John A Zadroga
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Angela M Gajda
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Atreju I Lackey
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Wensheng Lang
- Janssen Research & Development, LLC, Spring House, PA 19477
| | | | | | - Sui-Po Zhang
- Janssen Research & Development, LLC, Spring House, PA 19477
| | | | | | - Judith Storch
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901 Rutgers Center for Lipid Research, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901
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3
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Navia-Paldanius D, Savinainen JR, Laitinen JT. Biochemical and pharmacological characterization of human α/β-hydrolase domain containing 6 (ABHD6) and 12 (ABHD12). J Lipid Res 2012; 53:2413-24. [PMID: 22969151 DOI: 10.1194/jlr.m030411] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In the central nervous system, three enzymes belonging to the serine hydrolase family are thought to regulate the life time of the endocannabinoid 2-arachidonoylglycerol (C20:4) (2-AG). From these, monoacylglycerol lipase (MAGL) is well characterized and, on a quantitative basis, is the main 2-AG hydrolase. The postgenomic proteins α/β-hydrolase domain containing (ABHD)6 and ABHD12 remain poorly characterized. By applying a sensitive fluorescent glycerol assay, we delineate the substrate preferences of human ABHD6 and ABHD12 in comparison with MAGL. We show that the three hydrolases are genuine MAG lipases; medium-chain saturated MAGs were the best substrates for hABHD6 and hMAGL, whereas hABHD12 preferred the 1 (3)- and 2-isomers of arachidonoylglycerol. Site-directed mutagenesis of the amino acid residues forming the postulated catalytic triad (ABHD6: S148-D278-H306, ABHD12: S246-D333-H372) abolished enzymatic activity as well as labeling with the active site serine-directed fluorophosphonate probe TAMRA-FP. However, the role of D278 and H306 as residues of the catalytic core of ABHD6 could not be verified because none of the mutants showed detectable expression. Inhibitor profiling revealed striking potency differences between hABHD6 and hABHD12, a finding that, when combined with the substrate profiling data, should facilitate further efforts toward the design of potent and selective inhibitors, especially those targeting hABHD12, which currently lacks such inhibitors.
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Affiliation(s)
- Dina Navia-Paldanius
- Institute of Biomedicine, School of Medicine, University of Eastern Finland, Kuopio Campus, Kuopio, Finland
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4
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Alexander SPH, Kendall DA. The life cycle of the endocannabinoids: formation and inactivation. Curr Top Behav Neurosci 2009; 1:3-35. [PMID: 21104378 DOI: 10.1007/978-3-540-88955-7_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this chapter, we summarise the current thinking about the nature of endocannabinoids. In describing the life cycle of these agents, we highlight the synthetic and catabolic enzymes suggested to be involved. For each of these, we provide a systematic analysis of information on sequence, subcellular and cellular distribution, as well as physiological and pharmacological substrates, enhancers and inhibitors, together with brief descriptions of the impact of manipulating enzyme levels through genetic mechanisms (dealt with in more detail in the chapter "Genetic Models of the Endocannabinoid System" by Monory and Lutz, this volume). In addition, we describe experiments investigating the stimulation of endocannabinoid synthesis and release in intact cell systems.
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Affiliation(s)
- Stephen P H Alexander
- School of Biomedical Sciences and Institute of Neuroscience, University of Nottingham Medical School, Queens Medical Centre, Nottingham, UK.
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5
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Saario SM, Laitinen JT. Monoglyceride lipase as an enzyme hydrolyzing 2-arachidonoylglycerol. Chem Biodivers 2007; 4:1903-13. [PMID: 17712832 DOI: 10.1002/cbdv.200790158] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Susanna M Saario
- Department of Pharmaceutical Chemistry, University of Kuopio, P.O. Box 1627, FI-70211 Kuopio.
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6
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Saario SM, Salo OMH, Nevalainen T, Poso A, Laitinen JT, Järvinen T, Niemi R. Characterization of the sulfhydryl-sensitive site in the enzyme responsible for hydrolysis of 2-arachidonoyl-glycerol in rat cerebellar membranes. ACTA ACUST UNITED AC 2005; 12:649-56. [PMID: 15975510 DOI: 10.1016/j.chembiol.2005.04.013] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 03/24/2005] [Accepted: 04/08/2005] [Indexed: 11/28/2022]
Abstract
We have previously reported that the endocannabinoid, 2-arachidonoyl-glycerol (2-AG), is hydrolyzed in rat cerebellar membranes by monoglyceride lipase (MGL)-like enzymatic activity. The present study shows that, like MGL, 2-AG-degrading enzymatic activity is sensitive to inhibition by sulfhydryl-specific reagents. Inhibition studies of this enzymatic activity by N-ethylmaleimide analogs revealed that analogs with bulky hydrophobic N-substitution were more potent inhibitors than hydrophilic or less bulky agents. Interestingly, the substrate analog N-arachidonylmaleimide was found to be the most potent inhibitor. A comparison model of MGL was constructed to get a view on the cysteine residues located near the binding site. These findings support our previous conclusion that the 2-AG-degrading enzymatic activity in rat cerebellar membranes corresponds to MGL or MGL-like enzyme and should facilitate further efforts to develop potent and more selective MGL inhibitors.
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Affiliation(s)
- Susanna M Saario
- Department of Pharmaceutical Chemistry, P.O. Box 1627, FIN-70211 Kuopio, Finland.
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7
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Saario SM, Savinainen JR, Laitinen JT, Järvinen T, Niemi R. Monoglyceride lipase-like enzymatic activity is responsible for hydrolysis of 2-arachidonoylglycerol in rat cerebellar membranes. Biochem Pharmacol 2004; 67:1381-7. [PMID: 15013854 DOI: 10.1016/j.bcp.2003.12.003] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Accepted: 12/01/2003] [Indexed: 11/23/2022]
Abstract
2-Arachidonoylglycerol (2-AG) is an endogenous cannabinoid that binds to CB1 and CB2 cannabinoid receptors, inducing cannabimimetic effects. However, the cannabimimetic effects of 2-AG are weak in vivo due to its rapid enzymatic hydrolysis. The enzymatic hydrolysis of 2-AG has been proposed to mainly occur by monoglyceride lipase (monoacylglycerol lipase). Fatty acid amide hydrolase (FAAH), the enzyme responsible for the hydrolysis of N-arachidonoylethanolamide (AEA), is also able to hydrolyse 2-AG. In the present study, we investigated the hydrolysis of endocannabinoids in rat cerebellar membranes and observed that enzymatic activity towards 2-AG was 50-fold higher than that towards AEA. Furthermore, various inhibitors for 2-AG hydrolase activity were studied in rat cerebellar membranes. 2-AG hydrolysis was inhibited by methyl arachidonylfluorophosphonate, hexadecylsulphonyl fluoride and phenylmethylsulphonyl fluoride with ic(50) values of 2.2 nM, 241 nM and 155 microM, respectively. Potent FAAH inhibitors, such as OL-53 and URB597, did not inhibit the hydrolysis of 2-AG, suggesting that 2-AG is inactivated in rat cerebellar membranes by an enzyme distinct of FAAH. The observation that the hydrolysis of 1(3)-AG and 2-AG occurred at equal rates supports the role of MGL in 2-AG inactivation. This enzyme assay provides a useful method for future inhibition studies of 2-AG degrading enzyme(s) in brain membrane preparation having considerably higher MGL-like activity when compared to FAAH activity.
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Affiliation(s)
- Susanna M Saario
- Department of Pharmaceutical Chemistry, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland.
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8
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Lee JY, Lee HJ, Kim MR, Myung PK, Sok DE. Regulation of brain glycosylphosphatidylinositol-specific phospholipase D by natural amphiphiles. Neurochem Res 1999; 24:1577-83. [PMID: 10591409 DOI: 10.1023/a:1021112401640] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Brain glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD)-catalyzed conversion of amphiphilic form of Zn2+ -glycerophosphocholine cholinephosphodiesterase (Amp-GPC PDE) into hydrophilic form was investigated in the presence of natural amphiphiles. Monoacylglycerols enhanced considerably the conversion by GPI-PLD of Amp-GPC PDE to hydrophilic form, with the enhancing effect of monoacylglycerols being dependent on the size of acyl group (C8-C18). Whereas the maximal enhancement of GPI-PLD action was the greatest with monodecanoylglycerol, the concentration (EC50) required to achieve 50% maximal effect was the smallest for monomyristoyl- or monopalmitoylglycerol. In addition, monolaurylglycerol or its alkyl analogue, monododecylglycerol, showed a remarkable decrease in enhancing effect at high concentrations (>1 mM). Presence of double bond in acyl chain, as exemplified by monooleoylglycerol or mono-11-eicosenoin, further enhanced the conversion by GPI-PLD. Meanwhile, lysophosphatidylcholine (IC50, 25 microM) and phosphatidic acid (IC50, >100 microM), ionic amphiphiles, inhibited the GPI-PLD activity, which was determined in the presence of monooleoylglycerol as a detergent. From these results, it is suggested that the activity of GPI-PLD in vivo system may be regulated by natural amphiphiles.
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Affiliation(s)
- J Y Lee
- College of Pharmacy, Chungnam National University, Taejon, Korea
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9
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Fonovich de Schroeder TM, Pechén de D'Angelo AM. Dieldrin modifies the hydrolysis of PIP2 and decreases the fertilization rate in Bufo arenarum oocytes. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1995; 112:61-7. [PMID: 8564790 DOI: 10.1016/0742-8413(95)00076-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Carbachol treatment in Bufo arenarum oocytes decreases the radioactivity in [32P]PIP2 in the following 20 min after stimulation and increases the [3H]glycerol labeling of 1,2-DAG at 1 min of stimulation. On the contrary, in Dieldrin treated oocytes carbachol stimulation produces an increase in [32P]PIP2 labeling without changes in [3H]1,2-DAG radioactivity. The sustained hydrolysis of PIP2 observed in Control oocytes is necessary to generate the intracellular second messengers which initiate the fertilization pathway. The lack of response to muscarinic stimulation in Dieldrin treated oocytes, may be associated with an early activation of PIP2-PLC by the insecticide, producing a depletion of the PIP2 pool previous to the stimulation with carbachol. These changes take place simultaneously with a decrease in the ability of Bufo arenarum oocytes to be fertilized in vitro, suggesting a correlation between impairment in the PIP2 cascade and a decrease in the fertilization rate.
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Affiliation(s)
- T M Fonovich de Schroeder
- Libiquima, Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires, Neuquén, Argentina
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10
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He Y, Grinnell F. Role of phospholipase D in the cAMP signal transduction pathway activated during fibroblast contraction of collagen matrices. J Cell Biol 1995; 130:1197-205. [PMID: 7657704 PMCID: PMC2120549 DOI: 10.1083/jcb.130.5.1197] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Fibroblast contraction of stressed collagen matrices results in activation of a cAMP signal transduction pathway. This pathway involves influx of extracellular Ca2+ ions and increased production of arachidonic acid. We report that within 5 min after initiating contraction, a burst of phosphatidic acid release was detected. Phospholipase D was implicated in production of phosphatidic acid based on observation of a transphosphatidylation reaction in the presence of ethanol that resulted in formation of phosphatidylethanol at the expense of phosphatidic acid. Activation of phospholipase D required extracellular Ca2+ ions and was regulated by protein kinase C. Ethanol treatment of cells also inhibited by 60-70% contraction-dependent release of arachidonic acid and cAMP but had no effect on increased cAMP synthesis after addition of exogenous arachidonic acid or on phospholipase A2 activity measured in cell extracts. Moreover, other treatments that inhibited the burst of phosphatidic acid release after contraction--chelating extracellular Ca2+ or down-regulating protein kinase C--also blocked contraction activated cyclic AMP signaling. These results were consistent with the idea that phosphatidic acid production occurred upstream of arachidonic acid in the contraction-activated cAMP signaling pathway.
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Affiliation(s)
- Y He
- Department of Cell Biology and Neuroscience, UT Southwestern Medical Center, Dallas 75235, USA
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11
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Polyphosphoinositide-derived diacylglycerol stimulates the hydrolysis of phosphatidylcholine by phospholipase C during exocytosis of the ram sperm acrosome. Effect is not mediated by protein kinase C. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31555-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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12
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Abstract
A better knowledge of the biochemical and biophysical properties of cell membranes has revealed fundamental concepts concerning the regulation of cell functions by intrinsic components of the lipid matrix. Membrane lipids exhibit high chemical heterogeneity, with hundreds of distinct chemical species; studies of structure-function relationships have unraveled new roles for an increasing number of these lipids as determinants of membrane structure, anchors for membrane-associated proteins or signalling agents. Recent observations have confirmed triacylglycerol (TG) as a quantitatively minor intrinsic membrane component which seems to play a specific role in important metabolic events such as cell stimulation or transformation and metastatic processes. The rapid turnover of the acyl chains into TG of cell membranes suggests an active metabolism. In the plasma membrane, TG appears to be implicated in the generation of transient non-bilayer domains suspected to be associated with specific cellular events. This paper summarizes the current information on TG metabolism and focuses on the potential role of this neutral lipid species on the structure and function of cell membranes.
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Affiliation(s)
- B Lerique
- INSERM U.260, Faculté de Médecine Timone, Marseille, France
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13
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Vaughan PF, Murphy MG, Ball SG. Effect of inhibitors of eicosanoid metabolism on release of [3H]noradrenaline from the human neuroblastoma, SH-SY5Y. J Neurochem 1993; 60:1365-71. [PMID: 8455030 DOI: 10.1111/j.1471-4159.1993.tb03297.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Nordihydroguaiaretic acid (NDGA; a lipoxygenase inhibitor), LY-270766 (an inhibitor of 5-lipoxygenase), and the diacylglycerol lipase inhibitor RG 80267 completely eliminated potassium-evoked release of [3H]-noradrenaline ([3H]NA) from the human neuroblastoma clone SH-SY5Y with IC50 values of 10, 15, and 30 microM, respectively. In contrast, these inhibitors only partially inhibited carbachol-evoked release and had little effect on the calcium ionophore A23187-evoked release of NA in this cell line. Arachidonic acid partially inhibited potassium- and A23187-evoked release but did not reverse the inhibition of potassium-evoked release observed in the presence of RG 80267. These studies suggest that arachidonic acid (or its lipoxygenase products) are not important intermediates in the regulation of exocytosis in SH-SY5Y. This conclusion is strengthened by our studies in which SH-SY5Y cells were grown in medium supplemented with bovine serum albumin-linoleic acid (50 microM). Under these conditions there was a selective increase in content of membrane polyunsaturated fatty acids of the omega 6 series, including arachidonic acid; however, these changes did not effect potassium-, veratridine-, carbachol-, or calcium ionophore-evoked release of [3H]NA.
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Affiliation(s)
- P F Vaughan
- Department of Cardiovascular Studies, University of Leeds, England
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14
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Galatioto LE, Zahler P. Characterization of a triacylglycerol lipase that liberates arachidonic acid from bovine chromaffin cells during secretion. J Neurochem 1993; 60:32-9. [PMID: 8417152 DOI: 10.1111/j.1471-4159.1993.tb05819.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Primary cultures of chromaffin cells from bovine adrenal medullae were used as a model to study lipolytic events during stimulus-secretion coupling. It has been shown that chromaffin cells liberate arachidonic acid in addition to their main secretion product, the catecholamines. To understand more about the mechanism of arachidonic acid liberation, chromaffin cells were labeled with radioactive arachidonic acid, stimulated, and then analyzed for changes in lipid composition. After stimulation with 10(-4) M acetylcholine, the radioactivity of triacylglycerols decreased to the same extent that the free arachidonic acid level rose. This finding suggests that in bovine chromaffin cells a stimulation-dependent triacylglycerol lipase (triacylglycerol hydrolase; EC 3.1.1.3) is involved in arachidonic acid liberation. Further work was performed on detection, characterization, and isolation of this enzyme. Triacylglycerol lipase activity was found in whole cell homogenates and in plasma membrane fractions isolated from adrenal medullary tissue. The plasma membrane lipase showed a pH optimum of 4.3. The apparent Michaelis constant was determined as 3.3 x 10(-4) mol/L. Ca2+ did not influence the enzymatic activity. To differentiate the plasma membrane triacylglycerol lipase from the previously described plasma membrane diacylglycerol lipase of chromaffin cells, the influence of RG 80267, a specific diacylglycerol lipase inhibitor, was examined. RG 80267 (50 microM) inhibited the triacylglycerol lipase by only 24%, although diacylglycerol lipase was totally inhibited with only 20 microM RG 80267. The pH optimum of homogenate lipase was broad, lying between 4 and 7. Starting from the soluble fraction of whole cell homogenates, the triacylglycerol lipase was partially purified by ultracentrifugation and size-exclusion chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L E Galatioto
- Institute of Biochemistry, University of Berne, Switzerland
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15
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García MC, López MG, García AG, Sánchez Crespo M. Muscarinic acetylcholine receptor enhances phosphatidylcholine hydrolysis via phospholipase D in bovine chromaffin cells in culture. J Neurochem 1992; 59:2244-50. [PMID: 1431905 DOI: 10.1111/j.1471-4159.1992.tb10117.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Although it is well-established that inositol-containing lipids serve as precursors of intracellular second messenger molecules in chromaffin cells, we describe some findings that show the formation of diacylglycerol from phosphatidylcholine in response to agonist-mediated stimulation. Stimulation of chromaffin cells by acetylcholine produced a high turnover of phosphatidylcholine, as suggested by the release of [3H]choline derived from [3H]-phosphatidylcholine in experiments performed with [3H]choline chloride-prelabeled cells. An enhanced breakdown of phosphatidylcholine was also inferred from the finding of an increased formation of [3H]diacylglycerol in chromaffin cells prelabeled with [3H]glycerol. The diacylglycerol mass that accumulated after stimulation showed a distinct temporal course and seemed to exceed the mass that has been reported to be derived from phosphatidylinositol. In keeping with the purported origin from phosphatidylcholine, diacylglycerol showed a high content in [3H]oleate molecular species. Phospholipase D activity measurements and experiments performed in the presence of propranolol (an inhibitor of phosphatidic acid:phosphohydrolase) suggested that phosphatidylcholine is hydrolyzed by a phospholipase D activity, producing phosphatidic acid, which is subsequently degraded to diacylglycerol, rather than by a phospholipase C. Incubation of chromaffin cells in the presence of atropine before addition of acetylcholine showed complete inhibition of the increased formation of [3H]-diacylglycerol, whereas d-tubocurarine failed to do so. Taken together, these results suggest that acetylcholine activates phosphatidylcholine breakdown and diacylglycerol formation in chromaffin cells via a muscarinic-type receptor.
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Affiliation(s)
- M C García
- Departamento de Bioquímica y Fisiología-CSIC, Facultad de Medicina, Valladolid, Spain
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16
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Abstract
U-57,908 (RHC 80267) was shown to inhibit lipoprotein lipase (LPL) activity in cardiac myocytes from rat hearts; the concentrations required for inhibition to 50% of control activity were 1.1 microM and 2.5 microM for myocyte homogenates and a post-heparin medium preparation, respectively. The inhibition of LPL activity by U-57,908 was not changed when the concentration of the triolein substrate and apolipoprotein CII activator in the assay was reduced. The availability of U-57,908 as a potent and selective LPL inhibitor may provide a useful experimental approach in studies on lipoprotein metabolism.
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Affiliation(s)
- R Carroll
- MRC Signal Transduction Group, Faculty of Medicine, University of Calgary, Alberta, Canada
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17
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Owen PJ, Boarder MR. Influence of bradykinin on diacylglycerol and phosphatidic acid accumulation in cultured bovine adrenal chromaffin cells. J Neurochem 1991; 57:760-8. [PMID: 1861147 DOI: 10.1111/j.1471-4159.1991.tb08217.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Earlier studies have shown that bradykinin stimulated release of catecholamines from chromaffin cells by an influx of calcium through dihydropyridine-insensitive channels, and also that bradykinin stimulated (poly)phosphoinositide hydrolysis. To investigate membrane-bound second messengers in chromaffin cells, and to elucidate any role these may play in stimulus-secretion coupling, we have studied the influence of bradykinin on diacylglycerol and phosphatidic acid (PA). Using equilibrium labelling of primary cultures of chromaffin cells with [3H]arachidonic acid or [3H]glycerol, we found no influence of bradykinin (10 nM) on labelled diacylglycerol formation, either in the presence or absence of inhibitors of diacylglycerol lipase or kinase. However, when we used cells prelabelled with 32Pi for 2.5 h, we found that bradykinin produced a substantial stimulation of label found in PA, with an EC50 value of about 1 nM. This bradykinin stimulation of [32P]PA formation was only partially dependent on extracellular calcium, in contrast to the smaller response to nicotine, which was completely dependent on extracellular calcium. Short (10 min) pretreatment with tetradecanoylphorbol acetate (TPA) almost completely eliminated the bradykinin-stimulated formation of inositol phosphates, but failed to affect bradykinin stimulation of label in PA, suggesting that PA production in response to bradykinin is not downstream of phospholipase C activation. TPA alone failed to stimulate [32P]PA substantially, whereas long-term (24 or 48 h) treatment with TPA failed to attenuate the response to bradykinin. Diacylglycerol kinase inhibitors were also without effect on the bradykinin stimulation of [32P]PA. These results suggest that bradykinin stimulates PA production by a mechanism independent of the activation of protein kinase C.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P J Owen
- Department of Pharmacology and Therapeutics, University of Leicester, England
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Balsinde J, Diez E, Mollinedo F. Arachidonic acid release from diacylglycerol in human neutrophils. Translocation of diacylglycerol-deacylating enzyme activities from an intracellular pool to plasma membrane upon cell activation. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98454-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Shears SB. Regulation of the metabolism of 1,2-diacylglycerols and inositol phosphates that respond to receptor activation. Pharmacol Ther 1991; 49:79-104. [PMID: 1649478 DOI: 10.1016/0163-7258(91)90023-f] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This review assimilates information on the regulation of the metabolism of those inositol phosphates and diacylglycerols that respond to receptor activation. Particular emphasis is placed on the regulation of specific enzymes, the occurrence of isoenzymes, and metabolic compartmentalization; the overall aim is to demonstrate the significance of these activities in relation to the physiological impact of the various cell signalling processes.
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Affiliation(s)
- S B Shears
- Inositol Lipid Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
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Morgan A, Burgoyne RD. Relationship between arachidonic acid release and Ca2(+)-dependent exocytosis in digitonin-permeabilized bovine adrenal chromaffin cells. Biochem J 1990; 271:571-4. [PMID: 2123093 PMCID: PMC1149600 DOI: 10.1042/bj2710571] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The relationship between Ca2(+)-dependent arachidonic acid release and exocytosis from digitonin-permeabilized bovine adrenal chromaffin cells was investigated. The phospholipase A2 inhibitors mepacrine, nordihydroguaiaretic acid and indomethacin had no effect on either arachidonic acid release or secretion. The phospholipase A2 activator melittin had no effect on secretion. The specific diacylglycerol lipase inhibitor RG80267 had no effect on secretion, but decreased basal arachidonic acid release to such an extent that the level of arachidonic acid in treated cells in response to 10 microM-Ca2+ was equivalent to that of control cells in the absence of Ca2+. Staurosporine, a protein kinase C inhibitor, was found to abolish Ca2(+)-dependent arachidonic acid release completely, but had only a slight inhibitory effect on Ca2(+)-dependent secretion. It is concluded that arachidonic acid is not essential for Ca2(+)-dependent exocytosis in adrenal chromaffin cells.
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Affiliation(s)
- A Morgan
- M.R.C. Secretory Control Research Group, University of Liverpool, U.K
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Rindlisbacher B, Sidler MA, Galatioto LE, Zahler P. Arachidonic acid liberated by diacylglycerol lipase is essential for the release mechanism in chromaffin cells from bovine adrenal medulla. J Neurochem 1990; 54:1247-52. [PMID: 2107275 DOI: 10.1111/j.1471-4159.1990.tb01955.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Chromaffin cells from bovine adrenal medulla secrete catecholamines on stimulation with acetylcholine. In addition to the activation of the phosphatidylinositol cycle, arachidonic acid is generated, which was thought to be the result of phospholipase A2 activation. We have demonstrated in isolated plasma membranes of these cells that arachidonic acid is generated by a two-step reaction of diacylglycerol and monoacylglycerol lipase splitting diacylglycerol, which originates from the action of phospholipase C on phosphatidylinositols. No phospholipase A2 activity could be detected in plasma membranes so far. External addition of arachidonic acid increases the release in the absence and in the presence of agonist. Inhibition of the diacylglycerol lipase by RHC 80267 suppresses the catecholamine release, which is restored on addition of arachidonic acid. This effect, however, is reversed by lipoxygenase inhibitors, indicating that it is not arachidonic acid itself, but one of its lipoxygenase products, that is essential for inducing exocytosis.
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Plattner H. Regulation of membrane fusion during exocytosis. INTERNATIONAL REVIEW OF CYTOLOGY 1990; 119:197-286. [PMID: 2695484 DOI: 10.1016/s0074-7696(08)60652-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- H Plattner
- Faculty of Biology, University of Konstanz, Federal Republic of Germany
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