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Khan SA, Ilies MA. The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles. Int J Mol Sci 2023; 24:ijms24021353. [PMID: 36674864 PMCID: PMC9862071 DOI: 10.3390/ijms24021353] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 12/23/2022] [Accepted: 01/06/2023] [Indexed: 01/13/2023] Open
Abstract
The phospholipase A2 (PLA2) superfamily of phospholipase enzymes hydrolyzes the ester bond at the sn-2 position of the phospholipids, generating a free fatty acid and a lysophospholipid. The PLA2s are amphiphilic in nature and work only at the water/lipid interface, acting on phospholipid assemblies rather than on isolated single phospholipids. The superfamily of PLA2 comprises at least six big families of isoenzymes, based on their structure, location, substrate specificity and physiologic roles. We are reviewing the secreted PLA2 (sPLA2), cytosolic PLA2 (cPLA2), Ca2+-independent PLA2 (iPLA2), lipoprotein-associated PLA2 (LpPLA2), lysosomal PLA2 (LPLA2) and adipose-tissue-specific PLA2 (AdPLA2), focusing on the differences in their structure, mechanism of action, substrate specificity, interfacial kinetics and tissue distribution. The PLA2s play important roles both physiologically and pathologically, with their expression increasing significantly in diseases such as sepsis, inflammation, different cancers, glaucoma, obesity and Alzheimer's disease, which are also detailed in this review.
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Naranjo AN, Bandara G, Bai Y, Smelkinson MG, Tobío A, Komarow HD, Boyden SE, Kastner DL, Metcalfe DD, Olivera A. Critical Signaling Events in the Mechanoactivation of Human Mast Cells through p.C492Y-ADGRE2. J Invest Dermatol 2020; 140:2210-2220.e5. [PMID: 32222457 PMCID: PMC7529699 DOI: 10.1016/j.jid.2020.03.936] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/18/2020] [Accepted: 03/03/2020] [Indexed: 12/18/2022]
Abstract
A role for the adhesion G-protein coupled receptor ADGRE2 or EMR2 in mechanosensing was revealed by the finding of a missense substitution (p.C492Y) associated with familial vibratory urticaria. In these patients, friction of the skin induces mast cell hyper-degranulation through p.C492Y-ADGRE2, causing localized hives, flushing, and hypotension. We have now characterized the responses and intracellular signals elicited by mechanical activation in human mast cells expressing p.C492Y-ADGRE2 and attached to dermatan sulfate, a ligand for ADGRE2. The presence of p.C492Y-ADGRE2 reduced the threshold to activation and increased the extent of degranulation along with the percentage of mast cells responding. Vibration caused phospholipase C activation, transient increases in cytosolic calcium, and downstream activation of phosphoinositide 3-kinase and extracellular signal-regulated kinases 1 and 2 by Gβγ, Gαq/11, and Gαi/o-independent mechanisms. Degranulation induced by vibration was dependent on phospholipase C pathways, including calcium, protein kinase C, and phosphoinositide 3-kinase but not extracellular signal-regulated kinases 1/2 pathways, along with pertussis toxin-sensitive signals. In addition, mechanoactivation of mast cells stimulated the synthesis and release of prostaglandin D2, to our knowledge a previously unreported mediator in vibratory urticaria, and extracellular signal-regulated kinases 1/2 activation was required for this response together with calcium, protein kinase C, and to some extent, phosphoinositide 3-kinase. Our studies thus identified critical molecular events initiated by mechanical forces and potential therapeutic targets for patients with vibratory urticaria.
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Affiliation(s)
- Andrea N Naranjo
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Geethani Bandara
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Yun Bai
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Margery G Smelkinson
- Biological Imaging Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Araceli Tobío
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Hirsh D Komarow
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Steven E Boyden
- Inflammatory Disease Section, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Daniel L Kastner
- Inflammatory Disease Section, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Dean D Metcalfe
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Ana Olivera
- Mast Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
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Activation of bradykinin B2 receptor induced the inflammatory responses of cytosolic phospholipase A 2 after the early traumatic brain injury. Biochim Biophys Acta Mol Basis Dis 2018; 1864:2957-2971. [PMID: 29894755 DOI: 10.1016/j.bbadis.2018.06.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 06/02/2018] [Accepted: 06/07/2018] [Indexed: 12/17/2022]
Abstract
Phospholipase A2 is a known aggravator of inflammation and deteriorates neurological outcomes after traumatic brain injury (TBI), however the exact inflammatory mechanisms remain unknown. This study investigated the role of bradykinin and its receptor, which are known initial mediators within inflammation activation, as well as the mechanisms of the cytosolic phospholipase A2 (cPLA2)-related inflammatory responses after TBI. We found that cPLA2 and bradykinin B2 receptor were upregulated after a TBI. Rats treated with the bradykinin B2 receptor inhibitor LF 16-0687 exhibited significantly less cPLA2 expression and related inflammatory responses in the brain cortex after sustaining a controlled cortical impact (CCI) injury. Both the cPLA2 inhibitor and the LF16-0687 improved CCI rat outcomes by decreasing neuron death and reducing brain edema. The following TBI model utilized both primary astrocytes and primary neurons in order to gain further understanding of the inflammation mechanisms of the B2 bradykinin receptor and the cPLA2 in the central nervous system. There was a stronger reaction from the astrocytes as well as a protective effect of LF16-0687 after the stretch injury and bradykinin treatment. The protein kinase C pathway was thought to be involved in the B2 bradykinin receptor as well as the cPLA2-related inflammatory responses. Rottlerin, a Protein Kinase C (PKC) δ inhibitor, decreased the activity of the cPLA2 activity post-injury, and LF16-0687 suppressed both the PKC pathway and the cPLA2 activity within the astrocytes. These results indicated that the bradykinin B2 receptor-mediated pathway is involved in the cPLA2-related inflammatory response from the PKC pathway.
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Rafehi M, Neumann A, Baqi Y, Malik EM, Wiese M, Namasivayam V, Müller CE. Molecular Recognition of Agonists and Antagonists by the Nucleotide-Activated G Protein-Coupled P2Y 2 Receptor. J Med Chem 2017; 60:8425-8440. [PMID: 28938069 DOI: 10.1021/acs.jmedchem.7b00854] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A homology model of the nucleotide-activated P2Y2R was created based on the X-ray structures of the P2Y1 receptor. Docking studies were performed, and receptor mutants were created to probe the identified binding interactions. Mutation of residues predicted to interact with the ribose (Arg110) and the phosphates of the nucleotide agonists (Arg265, Arg292) or that contribute indirectly to binding (Tyr288) abolished activity. The Y114F, R194A, and F261A mutations led to inactivity of diadenosine tetraphosphate and to a reduced response of UTP. Significant reduction in agonist potency was observed for all other receptor mutants (Phe111, His184, Ser193, Phe261, Tyr268, Tyr269) predicted to be involved in agonist recognition. An ionic lock between Asp185 and Arg292 that is probably involved in receptor activation interacts with the phosphate groups. The antagonist AR-C118925 and anthraquinones likely bind to the orthosteric site. The updated homology models will be useful for virtual screening and drug design.
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Affiliation(s)
- Muhammad Rafehi
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, University of Bonn , 53121 Bonn, Germany
| | - Alexander Neumann
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, University of Bonn , 53121 Bonn, Germany
| | - Younis Baqi
- Department of Chemistry, Faculty of Science, Sultan Qaboos University , PO Box 36, Postal Code 123, Muscat, Oman
| | - Enas M Malik
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, University of Bonn , 53121 Bonn, Germany
| | - Michael Wiese
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry II, University of Bonn , 53121 Bonn, Germany
| | - Vigneshwaran Namasivayam
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, University of Bonn , 53121 Bonn, Germany.,PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry II, University of Bonn , 53121 Bonn, Germany
| | - Christa E Müller
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, University of Bonn , 53121 Bonn, Germany
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Yun B, Leslie CC. Cellular Assays for Evaluating Calcium-Dependent Translocation of cPLA 2α to Membrane. Methods Enzymol 2016; 583:71-99. [PMID: 28063500 DOI: 10.1016/bs.mie.2016.09.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The group IVA phospholipase A2, commonly called cytosolic phospholipase A2α (cPLA2α), is a widely expressed enzyme that hydrolyzes membrane phospholipid to produce arachidonic acid and lysophospholipids, which are precursors for a number of bioactive lipid mediators. Arachidonic acid is metabolized through the cyclooxygenase and lipoxygenase pathways for production of prostaglandins and leukotrienes that regulate normal physiological processes and contribute to disease pathogenesis. cPLA2α is composed of an N-terminal C2 domain and a C-terminal catalytic domain that contains the Ser-Asp catalytic dyad. The catalytic domain contains phosphorylation sites and basic residues that regulate the catalytic activity of cPLA2α. In response to cell stimulation, cPLA2α is rapidly activated by posttranslational mechanisms including increases in intracellular calcium and phosphorylation by mitogen-activated protein kinases. In resting cells, cPLA2α is localized in the cytosol but translocates to membrane including the Golgi, endoplasmic reticulum, and the peri-nuclear membrane in response to increases in intracellular calcium. Calcium binds to the C2 domain, which promotes the interaction of cPLA2α with membrane through hydrophobic interactions. In this chapter, we describe assays used to study the calcium-dependent translocation of cPLA2α to membrane, a regulatory step necessary for access to phospholipid and release of arachidonic acid.
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Affiliation(s)
- B Yun
- National Jewish Health, Denver, CO, United States
| | - C C Leslie
- National Jewish Health, Denver, CO, United States; University of Colorado Denver, Aurora, CO, United States.
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Lee J, Lee SJ, Lim KT. Preventive effects of ZPDC glycoprotein (24 kDa) on hepatotoxicity induced by mercury chloride in vitro and in vivo. Cell Biochem Funct 2014; 32:520-9. [PMID: 25043152 DOI: 10.1002/cbf.3046] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 06/18/2014] [Accepted: 06/19/2014] [Indexed: 12/23/2022]
Abstract
Mercury is a potent environmental contaminant that exerts toxic effect on various vital organs in the human body. Recently, we isolated glycoprotein from Zanthoxylum piperitum DC (ZPDC), which has antioxidant and anticancer effects. In the present study, we determined the preventive effects of ZPDC glycoprotein on hepatic damage induced by mercury chloride (HgCl2 ). We evaluated the activities of lactate dehydrogenase (LDH), alanine aminotransferase (ALT), antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)], extracellular signal-regulated kinase (ERK)1/2, p38 mitogen-activated protein kinase (MAPK), cyclo-oxygenase (COX-2), inducible nitric oxide synthetase (iNOS), and activator protein (AP-1) and the quantitative expressions of nuclear factor E2-related factor (Nrf2), heme oxygenase (HO-1), metallothionein (MT) and reduced glutathione (GSH) in mercury-chloride-exposed (50 μM and 10 mg/kg body weight) primary cultured hepatocytes and ICR mice, using biochemical assays, radioactivity and immunoblot analysis. The results demonstrated that ZPDC glycoprotein decreased the levels of LDH, ALT, HO-1 and MT, whereas it increased the activities of hepatic antioxidant enzymes (SOD, CAT and GPx) and reduced GSH in mercury-chloride-exposed primary cultured hepatocytes. Also, it suppressed arachidonic acid release and expression of ERK, p38 MAPK, COX-2, iNOS, AP-1 and Nrf-2 in primary cultured hepatocytes and ICR mice exposed to mercury chloride. Collectively, ZPDC glycoprotein may have potential applications to prevent hepatotoxicity induced by mercury chloride.
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Affiliation(s)
- Jin Lee
- Molecular Biochemistry Laboratory, Biotechnology Research Institute & Center for the Control of Animal Hazards Using Biotechnology (BK21), Chonnam National University, Gwang-ju, Korea
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Arana L, Gangoiti P, Ouro A, Rivera IG, Ordoñez M, Trueba M, Lankalapalli RS, Bittman R, Gomez-Muñoz A. Generation of reactive oxygen species (ROS) is a key factor for stimulation of macrophage proliferation by ceramide 1-phosphate. Exp Cell Res 2012; 318:350-60. [DOI: 10.1016/j.yexcr.2011.11.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 11/16/2011] [Accepted: 11/24/2011] [Indexed: 11/26/2022]
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Gabryel B, Bielecka A, Stolecka A, Bernacki J, Langfort J. Cytosolic phospholipase A2 inhibition is involved in the protective effect of nortriptyline in primary astrocyte cultures exposed to combined oxygen-glucose deprivation. Pharmacol Rep 2010; 62:814-26. [DOI: 10.1016/s1734-1140(10)70342-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 03/09/2010] [Indexed: 01/19/2023]
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Lim KT. Inhibitory effect of glycoprotein isolated from Opuntia ficus-indica var. saboten MAKINO on activities of allergy-mediators in compound 48/80-stimulated mast cells. Cell Immunol 2010; 264:78-85. [PMID: 20510397 DOI: 10.1016/j.cellimm.2010.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 05/02/2010] [Accepted: 05/04/2010] [Indexed: 11/15/2022]
Abstract
The present study was performed to investigate the anti-allergy potentials of glycoprotein (90kDa) isolated from Opuntia ficus-indica var. saboten MAKINO (OFI glycoprotein) in vivo (ICR mice) and in vitro (RBL-2H3 cells). At first, to know whether the OFI glycoprotein has an inhibitory ability for allergy in vivo, we evaluated the activities of allergy-related factors such as histamine and beta-hexosaminidase release, lactate dehydrogenase (LDH), and interleukin 4 (IL-4) in compound 48/80 (8 ml/kg BW)-treated ICR mice. After that, we studied to found the effect for anti-allergy in vitro such as nuclear factor kappa B (NF-kappaB) and inducible nitric oxide synthase (iNOS), extracellular signal-regulated kinase (ERK) 1/2, arachidonic acid, and cyclooxygenase-2 (COX-2) in compound 48/80 (5 microg/ml)-treated RBL-2H3 cells. Our results showed that the OFI glycoprotein (5 mg/kg) inhibited histamine and beta-hexosaminidase release, lactate dehydrogenase (LDH), and interleukin 4 (IL-4) in mice serum. Also OFI glycoprotein (25 microg/ml) has suppressive effects on the expression of MAPK (ERK1/2), and on protein expression of anti-allergic proteins (iNOS and COX-2). Thus, we speculate that the OFI glycoprotein is an example of natural compound that blocks anti-allergic signal transduction pathways.
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Affiliation(s)
- Kye-Taek Lim
- Molecular Biochemistry Laboratory, Biotechnology Research Institute, Chonnam National University, Gwang-ju 300, Yongbong-Dong 500-757, Republic of Korea.
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Sugita M, Kuwata H, Kudo I, Hara S. Differential contributions of protein kinase C isoforms in the regulation of group IIA secreted phospholipase A2 expression in cytokine-stimulated rat fibroblasts. Biochim Biophys Acta Mol Cell Biol Lipids 2010; 1801:70-6. [DOI: 10.1016/j.bbalip.2009.09.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/14/2009] [Accepted: 09/16/2009] [Indexed: 10/20/2022]
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Chalimoniuk M, Stolecka A, Ziemińska E, Stepień A, Langfort J, Strosznajder JB. Involvement of multiple protein kinases in cPLA2 phosphorylation, arachidonic acid release, and cell death in in vivo and in vitro models of 1-methyl-4-phenylpyridinium-induced parkinsonism--the possible key role of PKG. J Neurochem 2009; 110:307-17. [PMID: 19457107 DOI: 10.1111/j.1471-4159.2009.06147.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The study was aimed at investigating in vivo and in vitro the involvement of the cGMP/cGMP-dependent protein kinase (PKG) signaling pathway in MPP(+)-induced cytosolic phospholipase A(2) (cPLA(2)) activation of dopaminergic neurons. MPP(+) activated neuronal nitric oxide synthase (NOS)/soluble guanylyl cyclase/cGMP pathway in mouse midbrain and striatum, and in pheochromocytoma cell line 12 cells, and caused an upward shift in [Ca(2+)](i) level in the latter. The activation was accompanied by increases in total and phosphorylated cPLA(2), and increased arachidonic acid release. Effects of selective inhibitors [2-oxo-1,1,1-trifluoro-6,9-12,15-heneicosatetraene (AACOCF(3)), (E)-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)2h-pyran-2-one (BEL)] indicated the main impact of cPLA(2) on arachidonic acid release in pheochromocytoma cell line 12 cells. Treatment of the cells with the protein kinase inhibitors GF102610x, UO126, and KT5823, and with the nitric oxide synthase (NOS) inhibitor NNLA revealed the involvement of protein kinase C (PKC) and extracellular signal-regulated kinases 1 and 2 (ERK 1/2), with the possible key role of PKG, in cPLA(2) phosphorylation at Ser505. Inhibitors of cPLA(2) and PKG increased viability and reduced MPP(+)-induced apoptosis of the cells. Our results indicate that the neuronal NOS/cGMP/PKG pathway stimulates cPLA(2) phosphorylation at Ser505 by activating PKC and ERK1/2, and suggest that up-regulation of this pathway in experimental models of Parkinson's disease may mediate dopaminergic neuron degeneration and death through activation of cPLA(2).
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Affiliation(s)
- Malgorzata Chalimoniuk
- Department of Cellular Signaling, Mossakowski Medical Research Center, Polish Academy of Sciences, Warsaw, Poland.
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12
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van der Merwe JQ, Ohland CL, Hirota CL, MacNaughton WK. Prostaglandin E2 derived from cyclooxygenases 1 and 2 mediates intestinal epithelial ion transport stimulated by the activation of protease-activated receptor 2. J Pharmacol Exp Ther 2009; 329:747-52. [PMID: 19190238 DOI: 10.1124/jpet.108.145466] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Proteinase-activated receptor (PAR)(2) is activated by trypsin-like serine proteinases and has been implicated in intestinal inflammation. However, its role in the regulation of intestinal mucosal function remains unclear. Using the intestinal epithelial cell line, SCBN, we have studied the stimulus-secretion coupling mechanisms of PAR(2)-induced epithelial chloride transport, focusing on cyclooxygenase (COX)-1 and COX-2 activities and prostaglandin (PG) E(2) secretion. SCBN monolayers were grown on Snapwell supports, mounted in modified Ussing chambers, and exposed to the activating peptide, SLIGRL-NH(2) (50 microM), to activate PAR(2). Pretreatment with inhibitors of cytosolic PLA(2) (cPLA(2)) (AACOCF3, arachidonyltrifluoromethyl ketone), COX-1 [SC560, 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole], and COX-2 (celecoxib) resulted in a significant concentration-dependent attenuation of PAR(2)-induced changes in short-circuit current. Immunoblot analysis showed a PAR(2)-induced increase in cPLA(2) phosphorylation that was blocked by the mitogen-activated protein kinase kinase inhibitor, PD98059 [2-(2-amino-3methoxyphenyl)-4H-1benzopyran-4-one, C(16)H(13)NO(3)], and the pan-protein kinase C inhibitor, GFX (bisindolylmaleimide). PAR(2) stimulation also resulted in a large increase in the production of PGE(2) as determined by enzyme-linked immunosorbent assay and was also blocked by PD98059 and GFX. Immunofluorescence and immunoblot analysis determined that EP2 and EP4 are expressed at the basolateral membrane of SCBN cells. Through the use of selective inhibitors (EP2, AH6809 [6-isopropoxy-9-oxoxanthene-2-carboxylic acid]; EP4, GW627368X [N-[2[4,9-diethoxy-1-oxo-1,3-dihydro-2H-benzo[f]isoindol-2-yl)phenyl] acetyl]benzene sulphonamide]), it was found that both EP2 and EP4 were involved in mediating the PAR(2)-induced chloride secretory response. We conclude that basolateral PAR(2) activation induces epithelial chloride secretion that is mediated by cPLA(2), COX-1, COX-2, and the subsequent release of PGE(2). The production of PGE(2) results in an autocrine secretory response that is dependent on basolateral EP2 and EP4 receptors.
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Fogle KJ, Lyashchenko AK, Turbendian HK, Tibbs GR. HCN pacemaker channel activation is controlled by acidic lipids downstream of diacylglycerol kinase and phospholipase A2. J Neurosci 2007; 27:2802-14. [PMID: 17360902 PMCID: PMC6672581 DOI: 10.1523/jneurosci.4376-06.2007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hyperpolarization-activated pacemaker currents (I(H)) contribute to the subthreshold properties of excitable cells and thereby influence behaviors such as synaptic integration and the appearance and frequency of intrinsic rhythmic activity. Accordingly, modulation of I(H) contributes to cellular plasticity. Although I(H) activation is regulated by a plethora of neurotransmitters, including some that act via phospholipase C (PLC), the only second messengers known to alter I(H) voltage dependence are cAMP, internal protons (H+(I)s), and phosphatidylinositol-4,5-phosphate. Here, we show that 4beta-phorbol-12-myristate-13-acetate (4betaPMA), a stereoselective C-1 diacylglycerol-binding site agonist, enhances voltage-dependent opening of wild-type and cAMP/H+(I)-uncoupled hyperpolarization-activated, cyclic nucleotide-regulated (HCN) channels, but does not alter gating of the plant hyperpolarization-activated channel, KAT1. Pharmacological analysis indicates that 4betaPMA exerts its effects on HCN gating via sequential activation of PKC and diacylglycerol kinase (DGK) coupled with upregulation of MAPK (mitogen-activated protein kinase) and phospholipase A2 (PLA2), but its action is independent of phosphoinositide kinase 3 (PI3K) and PI4K. Demonstration that both phosphatidic acid and arachidonic acid (AA) directly facilitate HCN gating suggests that these metabolites may serve as the messengers downstream of DGK and PLA2, respectively. 4BetaPMA-mediated suppression of the maximal HCN current likely arises from channel interaction with AA coupled with an enhanced membrane retrieval triggered by the same pathways that modulate channel gating. These results indicate that regulation of excitable cell behavior by neurotransmitter-mediated modulation of I(H) may be exerted via changes in three signaling lipids in addition to the allosteric actions of cAMP and H+(I)s.
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Affiliation(s)
| | | | | | - Gareth R. Tibbs
- the Departments of Anesthesiology and
- Pharmacology, Columbia University, New York, New York 10032
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Garcia-Marcos M, Pochet S, Marino A, Dehaye JP. P2X7 and phospholipid signalling: The search of the “missing link” in epithelial cells. Cell Signal 2006; 18:2098-104. [PMID: 16815675 DOI: 10.1016/j.cellsig.2006.05.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Accepted: 05/11/2006] [Indexed: 11/22/2022]
Abstract
The purinergic receptor P2X(7) is widely expressed in epithelial cells. This receptor shares in common with the other P2X receptors the ability to form a non-selective cation channel. On the other hand, the COOH terminus of P2X(7) seems to allow this receptor to couple to a spectrum of downstream effectors responsible for the regulation of cell death and pore formation among other functions. However, the coupling of P2X(7) to these downstream effectors, as well as the identity of possible adapters directly interacting with the receptor, remains poorly understood. Here we review the ability of P2X(7) to activate phospholipid signalling pathways in epithelial cells and propose this step as a possible link between the receptor and other downstream effectors. The P2X(7) ability to control the cellular levels of several lipid messengers (PA, AA, DAG, ceramide, etc.) through the modulation of phospholipases (C, A(2), D) and neutral sphingomyelinase is described. These pathways are sometimes regulated independently of the channel function of the receptor. Recent data concerning P2X(7) localization in lipid rafts is also discussed in relation to the coupling to these pathways and dissociation from channel function.
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Affiliation(s)
- Mikel Garcia-Marcos
- Departamento de Bioquimica y Biologia Molecular, Facultad de Ciencias, Universidad del Pais Vasco, Barrio Sarriena S/N, Leioa, 48080 Bilbao, Spain
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McNamara RK, Ostrander M, Abplanalp W, Richtand NM, Benoit SC, Clegg DJ. Modulation of phosphoinositide-protein kinase C signal transduction by omega-3 fatty acids: implications for the pathophysiology and treatment of recurrent neuropsychiatric illness. Prostaglandins Leukot Essent Fatty Acids 2006; 75:237-57. [PMID: 16935483 DOI: 10.1016/j.plefa.2006.07.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The phosphoinositide (PI)-protein kinase C (PKC) signal transduction pathway is initiated by pre- and postsynaptic Galphaq-coupled receptors, and regulates several clinically relevant neurochemical events, including neurotransmitter release efficacy, monoamine receptor function and trafficking, monoamine transporter function and trafficking, axonal myelination, and gene expression. Mounting evidence for PI-PKC signaling hyperactivity in the peripheral (platelets) and central (premortem and postmortem brain) tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, coupled with evidence that PI-PKC signal transduction is down-regulated in rat brain following chronic, but not acute, treatment with antipsychotic, mood-stabilizer, and antidepressant medications, suggest that PI-PKC hyperactivity is central to an underlying pathophysiology. Evidence that membrane omega-3 fatty acids act as endogenous antagonists of the PI-PKC signal transduction pathway, coupled with evidence that omega-3 fatty acid deficiency is observed in peripheral and central tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, support the hypothesis that omega-3 fatty acid deficiency may contribute to elevated PI-PKC activity in these illnesses. The data reviewed in this paper outline a potential molecular mechanism by which omega-3 fatty acids could contribute to the pathophysiology and treatment of recurrent neuropsychiatric illness.
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Affiliation(s)
- Robert K McNamara
- Department of Psychiatry, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0559, USA.
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16
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Nandigama R, Padmasekar M, Wartenberg M, Sauer H. Feed forward cycle of hypotonic stress-induced ATP release, purinergic receptor activation, and growth stimulation of prostate cancer cells. J Biol Chem 2005; 281:5686-93. [PMID: 16321972 DOI: 10.1074/jbc.m510452200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP is released in many cell types upon mechanical strain, the physiological function of extracellular ATP is largely unknown, however. Here we report that ATP released upon hypotonic stress stimulated prostate cancer cell proliferation, activated purinergic receptors, increased intracellular [Ca(2+)](i), and initiated downstream signaling cascades that involved MAPKs ERK1/2 and p38 as well as phosphatidylinositol 3-kinase (PI3K). MAPK activation, the calcium response as well as induction of cell proliferation upon hypotonic stress were inhibited by preincubation with the ATP scavenger apyrase, indicating that hypotonic stress-induced signaling pathways are elicited by released ATP. Hypotonic stress increased prostaglandin E(2) (PGE(2)) synthesis. Consequently, ATP release was inhibited by antagonists of PI3K (LY294002 and wortmannin), phospholipase A(2) (methyl arachidonyl fluorophosphonate (MAFP)), cyclooxygenase-2 (COX-2) (indomethacin, etodolac, NS398) and 5,8,11,14-eicosatetraynoic acid (ETYA), which are involved in arachidonic acid metabolism. Furthermore, ATP release was abolished in the presence of the adenylate cyclase (AC) inhibitor MDL-12,330A, indicating regulation of ATP-release by cAMP. The hypotonic stress-induced ATP release was significantly blunted when the ATP-mediated signal transduction cascade was inhibited on different levels, i.e. purinergic receptors were blocked by suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), the Ca(2+) response was inhibited upon chelation of intracellular Ca(2+) by 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), and ERK1,2 as well as p38 were inhibited by UO126 and SB203580, respectively. In summary our data demonstrate that hypotonic stress initiates a feed forward cycle of ATP release and purinergic receptor signaling resulting in proliferation of prostate cancer cells.
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Affiliation(s)
- Rajender Nandigama
- Department of Physiology, Justus-Liebig-University Giessen, 35312 Giessen, Germany
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17
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Akimova AO, Bourcier N, Taurin S, Bundey RA, Grygorczyk K, Gekle M, Insel PA, Dulin NO, Orlov SN. Cl- secretion in ATP-treated renal epithelial C7-MDCK cells is mediated by activation of P 2Y1 receptors, phospholipase A2 and protein kinase A. J Physiol 2005; 568:789-801. [PMID: 16109726 PMCID: PMC1464179 DOI: 10.1113/jphysiol.2005.094375] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
This study examines the mechanism of P 2Y-induced Cl- secretion in monolayers of C7-Madin-Darby canine kidney (MDCK) cells triggered by basolateral application of ATP and measured as transcellular short current (I(SC)). Both ATP-induced arachidonic acid (AA) synthesis and I(SC) in ATP-treated cells were abolished by the phosholipase A2 (PLA2) inhibitor, AACOCF3. The cyclo-oxygenase inhibitor indomethacin decreased I(SC) and cAMP production in ATP-treated cells with an IC50 of approximately 0.3 microm. ATP led to rapid activation of cAMP-dependent protein kinase A (PKA), as estimated by phosphorylation of a vasodilator-stimulated phosphoprotein. PKA activity and I(SC) evoked by ATP, as well as by prostaglandin E1 (PGE1), were diminished in the presence of the PKA inhibitor H-89 or an adenovirus-mediated expression of PKA-inhibitor protein, PKI. In contrast, indomethacin completely blocked the increment of PKA and I(SC) triggered by ATP and AA, but did not affect PKA activation and I(SC) detected with PGE1. The kinetics of [Ca2+]i elevation in ATP- and thapsigargin-treated cells were similar and suppressed by the Ca(2+)i chelator BAPTA. Neither baseline nor maximal increment of ATP-induced I(SC) was affected by thapsigargin and BAPTA. Real-time PCR showed that C7 cells express more mRNA for P 2Y1 and P 2Y2 than for other P 2Y receptor subtypes. The rank order of potency (2MeSATP > ATP > ADP >> UTP) indicates that P 2Y1 rather than P 2Y2 receptors contribute to PKA and I(SC) activation. Viewed collectively, these data show that Cl- secretion in C7-MDCK monolayers treated with basolateral ATP is triggered by P 2Y1 receptors and is mediated by subsequent [Ca2+]i-independent activation of PLA2 and PKA.
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Affiliation(s)
- A Olga Akimova
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CHUM-Hôtel-Dieu), Montreal, PQ, Canada
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18
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Bae YS, Park EY, Lee HY, Kang HK, Suh PG, Kwak JY, Ryu SH, Lee T. Compounds stimulating cytosolic phospholipase A2 activity with a combinational action mode. Biochem Biophys Res Commun 2004; 325:632-8. [PMID: 15530440 DOI: 10.1016/j.bbrc.2004.10.063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2004] [Indexed: 10/26/2022]
Abstract
The screening of small synthetic compound libraries is a useful means of identifying molecules that modulate various cellular responses. We screened more than 10,000 different small compounds and identified three synthetic compounds that stimulate arachidonic acid (AA) release in a combinational manner in neutrophil-like differentiated HL60 cells. These three compounds were designated as AARIC-1, -2, and -3, representing AA release inducing compounds-1, -2, and -3. Although AA release was not induced by any single one of these compounds, it was dramatically stimulated by the three compounds in combination. Moreover, the effect of combined treatment by these compounds on AA release was completely abolished by MAFP and AACOCF(3), specific cytosolic phospholipase A(2) inhibitors. Furthermore, we found that AARIC-3 stimulates cytosolic calcium influx, while AARIC-1 induces ERK activation. Taken together, we demonstrate a useful approach to the study of complicated and nonlinear intracellular signaling networks using small synthetic compounds in combination.
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Affiliation(s)
- Yoe-Sik Bae
- Medical Research Center for Cancer Molecular Therapy, College of Medicine, Dong-A University, Busan 602-714, Republic of Korea.
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19
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Cho SH, You HJ, Woo CH, Yoo YJ, Kim JH. Rac and protein kinase C-delta regulate ERKs and cytosolic phospholipase A2 in FcepsilonRI signaling to cysteinyl leukotriene synthesis in mast cells. THE JOURNAL OF IMMUNOLOGY 2004; 173:624-31. [PMID: 15210825 DOI: 10.4049/jimmunol.173.1.624] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Although cysteinyl leukotrienes (cysLTs) are known to be principal inflammatory lipid mediators released from IgE-stimulated mast cells, the signaling mechanisms involved in the synthesis of cysLTs remain largely unknown. In the present study, therefore, we investigated the signaling pathway by which IgE induces cysLTs synthesis after binding to its high affinity receptor (FcepsilonRI) in RBL-2H3 mast cells. We found that IgE-induced cysLT synthesis is completely abolished in RBL-2H3(Rac-N17) cells, a stable cell line expressing Rac(N17), a dominant negative Rac1 mutant; conversely, synthesis was enhanced in cells expressing Rac(V12), a constitutively active Rac1 mutant, suggesting that Rac1 is a key mediator of IgE signaling to cysLT synthesis. Further analysis aimed at identifying mediators downstream of Rac1 revealed that pretreating cells with a protein kinase C-delta (PKC-delta) inhibitor or infection with an adenoviral vector harboring a dominant negative PKC-delta mutant significantly attenuates IgE-induced ERKs phosphorylation, cytosolic phospholipase A(2) phosphorylation/translocation, and cysLT synthesis. In addition, the expression of Rac(N17) blocked PKC-delta translocation and impaired the phosphorylation of ERKs and cytosolic phospholipase A(2) otherwise elicited by IgE stimulation. Taken together these results suggest that PKC-delta also plays a critical mediatory role in the IgE signaling pathway leading to cysLT synthesis, acting downstream of Rac1. Finally, the physiological significance of PKC-delta in the IgE signaling pathway was demonstrated in an Ag (OVA)-challenged in vivo mouse model, in which induced levels of cysLTs and airway responsiveness in lung airways were significantly diminished by prior i.p. injection of a PKC-delta inhibitor.
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Affiliation(s)
- Sung-Hoon Cho
- School of Life Sciences and Biotechnology, Korea University, 5-1 Anam-dong, Sungbuk-gu, Seoul 136-701, Korea
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20
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Tulapurkar ME, Laubinger W, Nahum V, Fischer B, Reiser G. Subtype specific internalization of P2Y1 and P2Y2 receptors induced by novel adenosine 5'-O-(1-boranotriphosphate) derivatives. Br J Pharmacol 2004; 142:869-78. [PMID: 15197109 PMCID: PMC1575069 DOI: 10.1038/sj.bjp.0705859] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
P2Y-nucleotide receptors represent important targets for drug development. The lack of stable and receptor specific agonists, however, has prevented successful therapeutic applications. A novel series of P-boronated ATP derivatives (ATP-alpha-B) were synthesized by substitution of a nonbridging O at P(alpha) with a BH(3) group. This introduces a chiral center, thus resulting in diastereoisomers. In addition, at C2 of the adenine ring a further substitution was made (Cl- or methylthio-). The pairs of diastereoisomers were denoted here as A and B isomers. Here, we tested the receptor subtype specificity of these analogs on HEK 293 cells stably expressing rat P2Y(1) and rat P2Y(2) receptors, respectively, both attached to the fluorescent marker protein GFP (rP2Y(1)-GFP, rP2Y(2)-GFP). We investigated agonist-induced receptor endocytosis, [Ca(2+)](i) rise and arachidonic acid (AA) release. Agonist-induced endocytosis of rP2Y(1)-GFP was more pronounced for the A isomers than the corresponding B counterparts for all ATP-alpha-B analogs. Both 2-MeS-substituted diastereoisomers induced a greater degree of agonist-induced receptor endocytosis as compared to the 2-Cl-substituted derivatives. Endocytosis results are in accordance with the potency to induce Ca(2+) release by these compounds in HEK 293 cells stably transfected with rP2Y(1). In case of rP2Y(2)-GFP, the borano-nucleotides were very weak agonists in comparison to UTP and ATP in terms of Ca(2+) release, AA release and in inducing receptor endocytosis. The different ATP-alpha-B derivatives and also the diastereoisomers were equally ineffective. Thus, the new agonists may be considered as potent and highly specific agonist drug candidates for P2Y(1) receptors. The difference in activity of the ATP analogs at P2Y receptors could be used as a tool to investigate structural differences between P2Y receptor subtypes.
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Affiliation(s)
- M E Tulapurkar
- Institut für Neurobiochemie, Medizinische Fakultät, Otto-von-Guericke-Universität Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany
| | - W Laubinger
- Institut für Neurobiochemie, Medizinische Fakultät, Otto-von-Guericke-Universität Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany
| | - V Nahum
- Department of Chemistry, Gonda-Goldschmied Medical Research Center, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - B Fischer
- Department of Chemistry, Gonda-Goldschmied Medical Research Center, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - G Reiser
- Institut für Neurobiochemie, Medizinische Fakultät, Otto-von-Guericke-Universität Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany
- Author for correspondence:
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Silva M, Song C, Nadeau WJ, Matthews JB, McCormick BA. Salmonella typhimurium SipA-induced neutrophil transepithelial migration: involvement of a PKC-alpha-dependent signal transduction pathway. Am J Physiol Gastrointest Liver Physiol 2004; 286:G1024-31. [PMID: 14739142 DOI: 10.1152/ajpgi.00299.2003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Salmonella typhimurium elicits an intense proinflammatory response characterized by movement of polymorphonuclear neutrophils (PMN) across the epithelial barrier to the intestinal lumen. We previously showed that S. typhimurium, via the type III secretion system effector protein SipA, initiates an ADP-ribosylation factor-6- and phospholipase D-dependent lipid-signaling cascade that directs activation of protein kinase C (PKC) and subsequent transepithelial movement of PMN. Here we sought to determine the specific PKC isoforms that are induced by the S. typhimurium effector SipA in model intestinal epithelia and to link the functional consequences of these isoforms in the promotion of PMN transepithelial migration. In vitro kinase PKC activation assays performed on polarized monolayers of T84 cells revealed that S. typhimurium and recombinant SipA induced activation of PKC-alpha, -delta, and -epsilon. To elucidate which of these isoforms play a key role in mediating epithelial cell responses that lead to the observed PMN transepithelial migration, we used a variety of PKC inhibitors with different isoform selectivity profiles. Inhibitors selective for PKC-alpha (Gö-6976 and 2,2',3,3',4,4'-hexahydroxyl-1,1'-biphenyl-6,6'-dimethanoldimethyl ether) markedly reduced S. typhimurium- and recombinant SipA-induced PMN transepithelial migration, whereas inhibitors to PKC-delta (rottlerin) or PKC-epsilon (V1-2) failed to exhibit a significant decrease in transepithelial movement of PMN. These results were confirmed biochemically and by immunofluorescence coupled to confocal microscopy. Our results are the first to show that the S. typhimurium effector protein SipA can activate multiple PKC isoforms, but only PKC-alpha is involved in the signal transduction cascade leading to PMN transepithelial migration.
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Affiliation(s)
- Milton Silva
- Combined Program in Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Boston, 02129, USA
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22
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Bailleux A, Wendum D, Audubert F, Jouniaux AM, Koumanov K, Trugnan G, Masliah J. Cytosolic phospholipase A2-p11 interaction controls arachidonic acid release as a function of epithelial cell confluence. Biochem J 2004; 378:307-15. [PMID: 14599294 PMCID: PMC1223956 DOI: 10.1042/bj20031014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Revised: 10/15/2003] [Accepted: 11/04/2003] [Indexed: 11/17/2022]
Abstract
Madin-Darby canine kidney type II cells were shown to release low amounts of AA (arachidonic acid) and prostaglandin E2 in response to various stimuli when analysed after cell confluence. In contrast, non-confluent Madin-Darby canine kidney type II cells released much higher amounts of AA and prostaglandin E2. In both stationary and non-confluent cells, AA was released by type IV cPLA2 (cytosolic phospholipase A2), as shown by the use of specific inhibitors and by analysis of the profile of fatty acids released. This confluence-dependent cPLA2 activation was not due to a difference in expression, or in phosphorylation of the enzyme, or in the amount of its substrate. To find out the mechanism by which cPLA2 activation may be regulated as a function of cell confluence, immunofluorescence and co-immunoprecipitation experiments were performed using cPLA2, p11, a natural inhibitor of the enzyme, and annexin II, the natural ligand of p11. These three proteins were expressed at a constant level, regardless of the cell confluence. In contrast, whereas annexin II and cPLA2 interacted at a constant rate, p11 and cPLA2 interacted more strongly in stationary cells, thus indicating that cPLA2 activation is regulated by its accessibility to p11, independent of their expression level. Our results indicate that, in epithelial cells, the cell confluence, i.e. the establishment of cell-cell contacts, rather than cell proliferation directly controls cPLA2 activation by changing the stoichiometry of p11/cPLA2 interaction.
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Affiliation(s)
- Anne Bailleux
- INSERM Unité 538, Université Pierre et Marie Curie, CHU Saint-Antoine, 27 rue Chaligny, 75012 Paris, France
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23
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Evans JH, Fergus DJ, Leslie CC. Regulation of cytosolic phospholipase A(2) translocation. ADVANCES IN ENZYME REGULATION 2004; 43:229-44. [PMID: 12791394 DOI: 10.1016/s0065-2571(02)00034-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- John H Evans
- Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA
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24
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Welch BD, Carlson NG, Shi H, Myatt L, Kishore BK. P2Y2 receptor-stimulated release of prostaglandin E2 by rat inner medullary collecting duct preparations. Am J Physiol Renal Physiol 2003; 285:F711-21. [PMID: 12799304 DOI: 10.1152/ajprenal.00096.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Extracellular nucleotides, acting through the P2Y2 receptor and the associated phosphoinositide-Ca2+ signaling pathway, inhibit AVP-stimulated osmotic water permeability in rat inner medullary collecting duct (IMCD). Because a rise in intracellular Ca2+ is frequently associated with enhanced arachidonic acid metabolism, we examined the effect of activation of the P2Y2 receptor on release of PGE2 in freshly prepared rat IMCD suspensions. Unstimulated IMCD released moderate, but significant, amounts of PGE2, which were more sensitive to cyclooxygenase (COX)-2 than COX-1 inhibition. Agonist activation of P2Y2 receptor by adenosine 5'-O-(3-thiotriphosphate) enhanced release of PGE2 from IMCD in a time- and concentration-dependent fashion. Purinergic-stimulated release of PGE2 was completely blocked by nonspecific COX inhibitors (flurbiprofen and 2-acetoxyphenylhept-2-ynyl sulfide). Differential COX inhibition studies revealed that purinergic-stimulated release of PGE2 was more sensitive to a COX-1-specific inhibitor (valeroyl salicylate) than a COX-2-specific inhibitor (NS-398). Thus purinergic stimulation resulted in significantly more release of PGE2 in the presence of COX-2 inhibitor than COX-1 inhibitor. If it is assumed that increased release of PGE2 is related to its increased production, our results suggest that purinergic stimulation of IMCD results in enhanced production and release of PGE2 in a COX-1-dependent fashion. Because PGE2 is known to affect transport of water, salt, and urea in IMCD, interaction of the purinergic system with the prostanoid system in IMCD can modulate handling of water, salt, and urea by IMCD and, thus, may constitute an AVP-independent regulatory mechanism.
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Affiliation(s)
- Brett D Welch
- Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake City 84132, USA
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25
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Neeli I, Yellaturu CR, Rao GN. Arachidonic acid activation of translation initiation signaling in vascular smooth muscle cells. Biochem Biophys Res Commun 2003; 309:755-61. [PMID: 13679036 DOI: 10.1016/j.bbrc.2003.08.066] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To understand the role of arachidonic acid (AA) in regulating vascular smooth muscle cell (VSMC) growth, its effects on phosphorylation of Akt, S6K1, ribosomal protein S6, 4EBP1, and eIF4E were studied. Arachidonic acid stimulated phosphorylation of Akt, S6K1, ribosomal protein S6, 4EBP1, and eIF4E in a time-dependent manner in VSMC. Arachidonic acid stimulation of phosphorylation of the above signaling molecules is specific, as these events were not affected by other unsaturated or saturated fatty acids. Metabolic conversion of AA via the LOX/MOX and/or COX pathways, to some extent, was required for its effects on the phosphorylation of Akt, S6K1, ribosomal protein S6, 4EBP1, and eIF4E. In addition, AA increased PI3K activity in a time-dependent manner in VSMC. LY294002, an inhibitor of PI3K, completely blocked AA-induced phosphorylation of Akt, S6K1, ribosomal protein S6, 4EBP1, and eIF4E, suggesting a role for PI3K in these effects. Consistent with its effects on translation initiation signaling events, AA induced global protein synthesis in VSMC and this response was dependent, to some extent, on its metabolism via the LOX/MOX and/or COX pathways, and mediated by the PI3K/Akt/mTOR pathway. Thus, the above observations provide the first biochemical evidence for the role of AA in the activation of translation initiation signaling in VSMC.
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Affiliation(s)
- Indira Neeli
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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26
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Han WK, Sapirstein A, Hung CC, Alessandrini A, Bonventre JV. Cross-talk between cytosolic phospholipase A2 alpha (cPLA2 alpha) and secretory phospholipase A2 (sPLA2) in hydrogen peroxide-induced arachidonic acid release in murine mesangial cells: sPLA2 regulates cPLA2 alpha activity that is responsible for arachidonic acid release. J Biol Chem 2003; 278:24153-63. [PMID: 12676927 DOI: 10.1074/jbc.m300424200] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Oxidant stress and phospholipase A2 (PLA2) activation have been implicated in numerous proinflammatory responses of the mesangial cell (MC). We investigated the cross-talk between group IValpha cytosolic PLA2 (cPLA2alpha) and secretory PLA2s (sPLA2s) during H2O2-induced arachidonic acid (AA) release using two types of murine MC: (i). MC+/+, which lack group IIa and V PLA2s, and (ii). MC-/-, which lack groups IIa, V, and IValpha PLA2s. H2O2-induced AA release was greater in MC+/+ compared with MC-/-. It has been argued that cPLA2alpha plays a regulatory role enhancing the activity of sPLA2s, which act on phospholipids to release fatty acid. Group IIa, V, or IValpha PLA2s were expressed in MC-/- or MC+/+ using recombinant adenovirus vectors. Expression of cPLA2alpha in H2O2-treated MC-/- increased AA release to a level approaching that of H2O2-treated MC+/+. Expression of either group IIa PLA2 or V PLA2 enhanced AA release in MC+/+ but had no effect on AA release in MC-/-. When sPLA2 and cPLA2alpha are both present, the effect of H2O2 is manifested by preferential release of AA compared with oleic acid. Inhibition of the ERK and protein kinase C signaling pathways with the MEK-1 inhibitor, U0126, and protein kinase C inhibitor, GF 1092030x, respectively, and chelating intracellular free calcium with 1,2-bis(2-aminophenoyl)ethane-N,N,N',N'-tetraacetic acid-AM, which also reduced ERK1/2 activation, significantly reduced H2O2-induced AA release in MC+/+ expressing either group IIa or V PLA2s. By contrast, H2O2-induced AA release was not enhanced when ERK1/2 was activated by infection of MC+/+ with constitutively active MEK1-DD. We conclude that the effect of group IIa and V PLA2s on H2O2-induced AA release is dependent upon the presence of cPLA2alpha and the activation of PKC and ERK1/2. Group IIa and V PLA2s are regulatory and cPLA2alpha is responsible for AA release.
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Affiliation(s)
- Won K Han
- Medical Services, Massachusetts General Hospital, Department of Medicine and Anesthesia, Harvard Medical School, Massachusetts, USA
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27
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Hughes RJ, Torres B, Zambon A, Arthur D, Bohmann C, Rump LC, Insel PA. Expression of multiple P2Y receptors by MDCK-D1 cells: P2Y1 receptor cloning and signaling. Drug Dev Res 2003. [DOI: 10.1002/ddr.10196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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28
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Zhou H, Das S, Murthy KS. Erk1/2- and p38 MAP kinase-dependent phosphorylation and activation of cPLA2 by m3 and m2 receptors. Am J Physiol Gastrointest Liver Physiol 2003; 284:G472-80. [PMID: 12576304 DOI: 10.1152/ajpgi.00345.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
This study examined the upstream signaling pathways initiated by muscarinic m2 and m3 receptors that mediate sustained ERK1/2- and p38 MAP kinase-dependent phosphorylation and activation of the 85-kDa cytosolic phospholipase (cPL)A(2) in smooth muscle. The pathway initiated by m2 receptors involved sequential activation of Gbetagamma(i3), phosphatidylinositol (PI)3-kinase, Cdc42, and Rac1, p21-activated kinase (PAK1), p38 mitogen-activated protein (MAP) kinase, and cPLA(2), and phosphorylation of cPLA(2) at Ser(505). cPLA(2) activity was inhibited to the same extent (61 +/- 5 to 72 +/- 4%) by the m2 antagonist methoctramine, Gbeta antibody, pertussis toxin, the PI3-kinase inhibitor LY 294002, PAK1 antibody, the p38 MAP kinase inhibitor SB-203580, and a Cdc42/Rac1 GEF (Vav2) antibody and by coexpression of dominant-negative Cdc42 and Rac1 mutants. The pathway initiated by m3 receptors involved sequential activation of Galpha(q), PLC-beta1, PKC, ERK1/2, and cPLA(2), and phosphorylation of cPLA(2) at Ser(505). cPLA(2) activity was inhibited to the same extent (35 +/- 3 to 41 +/- 5%) by the m3 antagonist 4-diphenylacetoxy-N-methylpiperdine (4-DAMP), the phosphoinositide hydrolysis inhibitor U-73122, the PKC inhibitor bisindolylmaleimide, and the ERK1/2 inhibitor PD 98059. cPLA(2) activity was not affected in cells coexpressing dominant-negative RhoA and PLC-delta1 mutants, implying that PKC was not derived from phosphatidylcholine hydrolysis. The effects of ERK1/2 and p38 MAP kinase on cPLA(2) activity were additive and accounted fully for activation and phosphorylation of cPLA(2).
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Affiliation(s)
- Huiping Zhou
- Departments of Physiology and Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA
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29
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Pilane CM, LaBelle EF. cPLA2 activator peptide, PLAP, increases arachidonic acid release and apoptosis of vascular smooth muscle cells. J Cell Physiol 2003; 198:48-52. [PMID: 14584043 DOI: 10.1002/jcp.10382] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Apoptosis of vascular smooth muscle cells (VSMCs) has recently drawn a lot of interest in various laboratories due to its importance in atherogenesis. We have shown previously that nitric-oxide (NO) can induce apoptosis of VSMCs and that the NO-induced apoptosis is accompanied by an increase in arachidonic acid release via cytoplasmic Ca(2+)-dependent phospholipase A(2) (cPLA(2)). We have demonstrated here that NO-induced activation of cPLA(2) leading to increased arachidonic acid release can be mimicked via direct activation of cPLA(2) with a cPLA(2) activator peptide, PLAP. The PLAP induced arachidonic acid release and apoptosis is inhibitable by a cPLA(2)-specific inhibitor, AACOCF(3), indicating the direct involvement of cPLA(2). In this study, activation of cPLA(2) appears to be preceded by activation and binding by PLAP indicating that the cPLA(2) functions are mediated via PLAP.
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Affiliation(s)
- Cyril M Pilane
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA
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Han SJ, Ko HM, Choi JH, Seo KH, Lee HS, Choi EK, Choi IW, Lee HK, Im SY. Molecular mechanisms for lipopolysaccharide-induced biphasic activation of nuclear factor-kappa B (NF-kappa B). J Biol Chem 2002; 277:44715-21. [PMID: 12235132 DOI: 10.1074/jbc.m202524200] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nuclear factor-kappaB (NF-kappaB) is an important transcription factor necessary for initiating and sustaining inflammatory and immune reactions. The inducers of NF-kappaB are well characterized, but the molecular mechanisms underlying multiple in vivo NF-kappaB activation processes are poorly understood. The injection of lipopolysaccharide resulted in a biphasic activation of NF-kappaB during the 18-h observation period in various organs of mice. The early and late phases of NF-kappaB activation occurred at 0.5-2 h and 8-12 h, respectively. Platelet-activating factor, which is released in response to lipopolysaccharide injection, was responsible for the activation of the early phase of NF-kappaB. The early NF-kappaB activity led to the induction of proinflammatory cytokines, tumor necrosis factor (TNF), and interleukin (IL)-1beta, which are known to be efficient inducers of NF-kappaB. Using the TNF knockout and IL-1 receptor knockout mice, we found that TNF and IL-1beta had a role in the second phase activation of NF-kappaB. These cytokines did promote the synthesis of platelet-activating factor, which in turn induced the secondary activation of NF-kappaB. These observations describe a novel autoregulatory molecular mechanism for the biphasic activation of NF-kappaB.
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Affiliation(s)
- Su-Ji Han
- Department of Biological Sciences, College of Natural Sciences, The Institute of Basic Sciences, Chonnam National University, Kwangju 500-757, Republic of Korea
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31
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Evans JH, Fergus DJ, Leslie CC. Inhibition of the MEK1/ERK pathway reduces arachidonic acid release independently of cPLA2 phosphorylation and translocation. BMC BIOCHEMISTRY 2002; 3:30. [PMID: 12370087 PMCID: PMC130032 DOI: 10.1186/1471-2091-3-30] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2002] [Accepted: 10/08/2002] [Indexed: 12/05/2022]
Abstract
BACKGROUND The 85-kDa cytosolic phospholipase A2 (cPLA2) mediates arachidonic acid (AA) release in MDCK cells. Although calcium and mitogen-activated protein kinases regulate cPLA2, the correlation of cPLA2 translocation and phosphorylation with MAPK activation and AA release is unclear. RESULTS MEK1 inhibition by U0126 inhibited AA release in response to ATP and ionomycin. This directly correlated with inhibition of ERK activation but not with phosphorylation of cPLA2 on Ser505, which was only partially inhibited by ERK inhibition. Inhibition of AA release by U0126 was still observed when stoichiometric phosphorylation of cPLA2 on Ser505 was maintained by activating p38 with anisomycin. Translocation kinetics of wild-type cPLA2 and cPLA2 containing S505A or S727A mutations to Golgi were similar in response to ATP and ionomycin and were not affected by U0126. CONCLUSIONS These results suggest that the ability of cPLA2 to hydrolyze membrane phospholipid is reduced by inhibition of the MEK1/ERK pathway and that the reduction in activity is independent of cPLA2 phosphorylation and translocation to membrane. The results also demonstrate that cPLA2 mutated at the phosphorylation sites Ser505 and Ser727 translocated with similar kinetic as wild-type cPLA2.
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Affiliation(s)
- John H Evans
- Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado USA 80206
| | - Daniel J Fergus
- Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado USA 80206
| | - Christina C Leslie
- Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado USA 80206
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Xu J, Weng YI, Simonyi A, Krugh BW, Liao Z, Weisman GA, Sun GY, Simoni A. Role of PKC and MAPK in cytosolic PLA2 phosphorylation and arachadonic acid release in primary murine astrocytes. J Neurochem 2002; 83:259-70. [PMID: 12423237 DOI: 10.1046/j.1471-4159.2002.01145.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although Group IV cytosolic phospholipase A2 (cPLA2) in astrocytes has been implicated in a number of neurodegenerative diseases, mechanisms leading to its activation and release of arachidonic acid (AA) have not been clearly elucidated. In primary murine astrocytes, phorbol myristate acetate (PMA) and ATP stimulated phosphorylation of ERK1/2 and cPLA2 as well as evoked AA release. However, complete inhibition of phospho-ERK by U0126, an inhibitor of mitogen-activated protein kinase kinase (MEK), did not completely inhibit PMA-stimulated cPLA2 and AA release. Epidermal growth factor (EGF) also stimulated phosphorylation of ERK1/2 and cPLA2[largely through a protein kinase C (PKC)-independent pathway], but EGF did not evoke AA release. These results suggest that phosphorylation of cPLA2 due to phospho-ERK is not sufficient to evoke AA release. However, complete inhibition of ATP-induced cPLA2 phosphorylation and AA release was observed when astrocytes were treated with GF109203x, a general PKC inhibitor, together with U0126, indicating the important role for both PKC and ERK in mediating the ATP-induced AA response. There is evidence that PMA and ATP stimulated AA release through different PKC isoforms in astrocytes. In agreement with the sensitivity of PMA-induced responses to PKC down-regulation, prolonged treatment with PMA resulted in down-regulation of PKCalpha and epsilon in these cells. Furthermore, PMA but not ATP stimulated rapid translocation of PKCalpha from cytosol to membranes. Together, our results provided evidence for an important role of PKC in mediating cPLA2 phosphorylation and AA release in astrocytes through both ERK1/2-dependent and ERK1/2-independent pathways.
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Affiliation(s)
- Jianfeng Xu
- Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, USA
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Torres B, Zambon AC, Insel PA. P2Y11 receptors activate adenylyl cyclase and contribute to nucleotide-promoted cAMP formation in MDCK-D(1) cells. A mechanism for nucleotide-mediated autocrine-paracrine regulation. J Biol Chem 2002; 277:7761-5. [PMID: 11788591 DOI: 10.1074/jbc.m110352200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Extracellular nucleotides activate P2Y receptors, thereby increasing cAMP formation in Madin-Darby canine kidney (MDCK-D(1)) cells, which express P2Y(1), P2Y(2), and P2Y(11) receptors (Post, S. R., Rump, L. C., Zambon, A., Hughes, R. J., Buda, M. D., Jacobson, J. P., Kao, C. C., and Insel, P. A. (1998) J. Biol. Chem. 273, 23093-23097). The cyclooxygenase inhibitor indomethacin (indo) eliminates UTP-promoted cAMP formation (i.e. via P2Y(2) receptors) but only partially blocks ATP-promoted cAMP formation. The latter response is completely blocked by the nonselective P2Y receptor antagonist suramin. We have sought to identify the mechanism for this P2Y receptor-mediated, indo-resistant cAMP formation. The agonist rank order potencies for cAMP formation were: ADP beta S > or = MT-ADP > 2-MT-ATP > ADP, ATP, ATP gamma S > UTP, AMP, adenosine. We found a similar rank order in MDCK-D(1) cells overexpressing cloned green fluorescent protein-tagged P2Y(11) receptors, but the potency of the agonists was enhanced, consistent with a P2Y(11) receptor-mediated effect. cAMP generation by the P2Y(1) and P2Y(11) receptor agonist ADP beta S was not inhibited by several P2Y(1)-selective antagonists (PPADS, A2P5P, and MRS 2179). Forskolin synergistically enhanced cAMP generation in response to ADP beta S or PGE(2), implying that, like PGE(2), ADP beta S activates adenylyl cyclase via G(s), a conclusion supported by results showing ADP beta S and MT-ADP promoted activation of adenylyl cyclase activity in MDCK-D(1) membranes. We conclude that nucleotide-promoted, indo-resistant cAMP formation in MDCK-D(1) cells occurs via G(s)-linked P2Y(11) receptors. These data describing adenylyl cyclase activity via endogenous P2Y(11) receptors define a mechanism by which released nucleotides can increase cAMP in MDCK-D(1) and other P2Y(11)-containing cells.
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Affiliation(s)
- Brian Torres
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636
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34
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Criss AK, Silva M, Casanova JE, McCormick BA. Regulation of Salmonella-induced neutrophil transmigration by epithelial ADP-ribosylation factor 6. J Biol Chem 2001; 276:48431-9. [PMID: 11641400 DOI: 10.1074/jbc.m106969200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Salmonella typhimurium elicits an acute inflammatory response in the host intestinal epithelium, characterized by the movement of polymorphonuclear leukocytes (PMN) across the epithelial monolayer to the intestinal lumen. It was recently shown that SipA, a protein secreted by S. typhimurium, is necessary and sufficient to drive PMN transmigration across model intestinal epithelia (Lee, C. A., Silva, M., Siber, A. M., Kelly, A. J., Galyov, E., and McCormick, B. A. (2000) Proc. Natl. Acad Sci. USA 97, 12283-12288). However, the epithelial factors responsible for this process have not been identified. Here, for the first time, we demonstrate that S. typhimurium-induced PMN transmigration across Madin-Darby canine kidney-polarized monolayers is regulated by the GTPase ARF6. Apically added S. typhimurium promoted the translocation of ARF6 and its exchange factor ARNO to the apical surface. Overexpression of a dominant-negative mutant of ARF6 inhibited Salmonella-induced PMN transmigration, which was due to a reduction in apical release of the PMN chemoattractant PEEC (pathogen-elicited epithelial chemoattractant), without affecting bacterial internalization. Furthermore, ARF6 and its effector phospholipase D (PLD) were both required for bacteria-induced translocation of protein kinase C (PKC) to membranes. These results describe a novel signal transduction pathway, in which Salmonella initiates an ARF6- and PLD-dependent lipid signaling cascade that, in turn, directs activation of PKC, release of PEEC, and subsequent transepithelial PMN movement.
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Affiliation(s)
- A K Criss
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, USA
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35
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Malhotra A, Kang BP, Opawumi D, Belizaire W, Meggs LG. Molecular biology of protein kinase C signaling in cardiac myocytes. Mol Cell Biochem 2001; 225:97-107. [PMID: 11716370 DOI: 10.1023/a:1012261903611] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The PKC family of serine/threonine kinases have been implicated in a diverse array of cellular responses. Adult cardiac myocytes express multiple PKC isozymes, which participate in the response of muscle cells to extracellular stimuli, modulate contractile properties, and promote cell growth and survival. Recently, the classification of this ubiquitous family of signaling molecules has been expanded from three to four subfamilies. This review will focus on the application of pharmacologic and molecular approaches to explore the biology of cardiac PKC isozymes. The availability of transgenic mice and peptide PKC modulators have been instrumental in identifying target substrates for activated cardiac PKC isozymes, as well as the identification of specific isozymes linked to distinct growth characteristics and cell phenotype. The rapid growth of knowledge in the area of PKC signaling and PKC substrate interactions, may result in the development of therapeutic modalities with the potential to arrest or reverse the progression of cardiovascular diseases.
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Affiliation(s)
- A Malhotra
- Department of Medicine, UMDNJ-New Jersey Medical School, Newark 07103, USA.
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36
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Ghomashchi F, Stewart A, Hefner Y, Ramanadham S, Turk J, Leslie CC, Gelb MH. A pyrrolidine-based specific inhibitor of cytosolic phospholipase A(2)alpha blocks arachidonic acid release in a variety of mammalian cells. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1513:160-6. [PMID: 11470087 DOI: 10.1016/s0005-2736(01)00349-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We analyzed a recently reported (K. Seno, T. Okuno, K. Nishi, Y. Murakami, F. Watanabe, T. Matsuur, M. Wada, Y. Fujii, M. Yamada, T. Ogawa, T. Okada, H. Hashizume, M. Kii, S.-H. Hara, S. Hagishita, S. Nakamoto, J. Med. Chem. 43 (2000)) pyrrolidine-based inhibitor, pyrrolidine-1, against the human group IV cytosolic phospholipase A(2) alpha-isoform (cPLA(2)alpha). Pyrrolidine-1 inhibits cPLA(2)alpha by 50% when present at approx. 0.002 mole fraction in the interface in a number of in vitro assays. It is much less potent on the cPLA(2)gamma isoform, calcium-independent group VI PLA(2) and groups IIA, X, and V secreted PLA(2)s. Pyrrolidine-1 blocked all of the arachidonic acid released in Ca(2+) ionophore-stimulated CHO cells stably transfected with cPLA(2)alpha, in zymosan- and okadaic acid-stimulated mouse peritoneal macrophages, and in ATP- and Ca(2+) ionophore-stimulated MDCK cells.
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Affiliation(s)
- F Ghomashchi
- Departments of Chemistry and Biochemistry, University of Washington, Seattle, WA 98195, USA
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37
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Evans JH, Spencer DM, Zweifach A, Leslie CC. Intracellular Calcium Signals Regulating Cytosolic Phospholipase A2 Translocation to Internal Membranes. J Biol Chem 2001; 276:30150-60. [PMID: 11375391 DOI: 10.1074/jbc.m100943200] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Increased intracellular Ca(2+) concentrations ([Ca(2+)](i)) promote cytosolic phospholipase A(2) (cPLA(2)) translocation to intracellular membranes. The specific membranes to which cPLA(2) translocates and the [Ca(2+)](i) signals required were investigated. Plasmids of EGFP fused to full-length cPLA(2) (EGFP-FL) or to the cPLA(2) C2 domain (EGFP-C2) were used in Ca(2+)/EGFP imaging experiments of cells treated with [Ca(2+)](i)-mobilizing agonists. EGFP-FL and -C2 translocated to Golgi in response to sustained [Ca(2+)](i) greater than approximately 100-125 nm and to Golgi, ER, and perinuclear membranes (PNM) at [Ca(2+)](i) greater than approximately 210-280 nm. In response to short duration [Ca(2+)](i) transients, EGFP-C2 translocated to Golgi, ER, and PNM, but EGFP-FL translocation was restricted to Golgi. However, EGFP-FL translocated to Golgi, ER, and PNM in response to long duration transients. In response to declining [Ca(2+)](i), EGFP-C2 readily dissociated from Golgi, but EGFP-FL dissociation was delayed. Agonist-induced arachidonic acid release was proportional to the [Ca(2+)](i) and to the extent of cPLA(2) translocation. In summary, we find that the differential translocation of cPLA(2) to Golgi or to ER and PNM is a function of [Ca(2+)](i) amplitude and duration. These results suggest that the cPLA(2) C2 domain regulates differential, Ca(2+)-dependent membrane targeting and that the catalytic domain regulates both the rate of translocation and enzyme residence.
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Affiliation(s)
- J H Evans
- Program in Cell Biology, Department of Pediatrics, and Department of Immunology, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
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38
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Ostrom RS, Gregorian C, Drenan RM, Gabot K, Rana BK, Insel PA. Key role for constitutive cyclooxygenase-2 of MDCK cells in basal signaling and response to released ATP. Am J Physiol Cell Physiol 2001; 281:C524-31. [PMID: 11443051 DOI: 10.1152/ajpcell.2001.281.2.c524] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Madin-Darby canine kidney (MDCK) cells release ATP upon mechanical or biochemical activation, initiating P2Y receptor signaling that regulates basal levels of multiple second messengers, including cAMP (J Biol Chem 275: 11735--11739, 2000). Data shown here document inhibition of cAMP formation by Gd(3+) and niflumic acid, channel inhibitors that block ATP release. cAMP production is stimulated via Ca(2+)-dependent activation of cytosolic phospholipase A(2), release of arachidonic acid (AA), and cyclooxygenase (COX)-dependent production of prostaglandins, which activate prostanoid receptors coupled to G(s) and adenylyl cyclase. In the current investigation, we assessed the expression and functional role of the two known isoforms of COX, COX-1 and COX-2. Treatment of cells with either a COX-1-selective inhibitor, SC-560, or COX-2-selective inhibitors, SC-58125 or NS-398, inhibited basal and UTP-stimulated cAMP levels. COX inhibitors also decreased forskolin-stimulated cAMP formation, implying this response is in part attributable to an action of AA metabolites. These findings imply an important role for the inducible form of COX, COX-2, under basal conditions. Indeed, COX-2 expression was readily detectable by immunoblot, and treatments that induce or reduce COX-2 expression in other cells (interleukin-1beta, tumor necrosis factor-alpha, phorbol ester, or dexamethasone) had minimal or no effect on the levels of COX-2 immunoreactivity. RT-PCR using isoform-specific primers detected COX-2 mRNA. We conclude that COX-2 is constitutively expressed in MDCK-D(1) cells and participates in basal and P2Y(2)-mediated signaling, implying a key role for COX-2 in regulation of epithelial cell function.
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Affiliation(s)
- R S Ostrom
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA
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39
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Zambon AC, Brunton LL, Barrett KE, Hughes RJ, Torres B, Insel PA. Cloning, expression, signaling mechanisms, and membrane targeting of P2Y(11) receptors in Madin Darby canine kidney cells. Mol Pharmacol 2001; 60:26-35. [PMID: 11408597 DOI: 10.1124/mol.60.1.26] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The P2Y(11) receptor is hypothesized to link to both G(s) and G(q), although this proposition is based on expression and separate assays of G(s) and G(q) function in different cell types [J Biol Chem 1997;272:31969-31973]. We have cloned and characterized a canine P2Y(11)-like (cP2Y(11)) receptor from cultured Madin Darby canine kidney (MDCK-D1) cells. When cP2Y(11) receptors are expressed in canine thymocyte (CF2Th) cells that normally lack functional purinergic responses, ADP beta S stimulates phosphatidylinositol (PI) hydrolysis, Ca(2+) mobilization, and cAMP accumulation. Pharmacologic analysis indicates that the stimulation of cAMP production is direct and not a result of eicosanoid synthesis, activation of PKC, or elevation of cell Ca(2+). The rank order of potency for stimulation of PI hydrolysis by cP2Y(11) receptors (adenosine 5'-(2-O-thio) diphosphate = 2-methylthio-ADP >/= 2-methylthio-ATP >> ADP > ATP) differs from that of hP2Y(11) receptors. Microscopic examination of MDCK-D1 cells expressing carboxyl-terminal green fluorescent protein (GFP)-tagged cP2Y(11) (cP2Y(11)-GFP) receptors indicates primarily basolateral (BL) targeting. BL addition of 200 microM ADP beta S to confluent monolayers of MDCK-D1 cells produces an increase in short circuit current (I(sc)) (11.6 +/- 1.6 microA/cm(2)) whereas apical addition of agonist has no effect, confirming targeting of functional endogenous P2Y(11) receptors to the BL surface. In contrast, when either cP2Y(11) or cP2Y(11)-GFP is overexpressed in MDCK-D1 cells, the sensitivity of I(sc) to BL agonist increases by nearly 2 orders of magnitude, as if receptor density normally limited agonist potency; moreover, apical addition of ADP beta S now produces an increase in I(sc) but with low potency. The data support the BL localization of cP2Y(11) receptors and receptor coupling to changes in I(sc) in MDCK-D1 cells except in cases in which receptors are overexpressed; receptor overexpression leads to altered sensitivities and sites of coupling to physiologic responses.
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Affiliation(s)
- A C Zambon
- The Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, California, USA
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40
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Abstract
ATP, besides an intracellular energy source, is an agonist when applied to a variety of different cells including cardiomyocytes. Sources of ATP in the extracellular milieu are multiple. Extracellular ATP is rapidly degraded by ectonucleotidases. Today ionotropic P2X(1--7) receptors and metabotropic P2Y(1,2,4,6,11) receptors have been cloned and their mRNA found in cardiomyocytes. On a single cardiomyocyte, micromolar ATP induces nonspecific cationic and Cl(-) currents that depolarize the cells. ATP both increases directly via a G(s) protein and decreases Ca(2+) current. ATP activates the inward-rectifying currents (ACh- and ATP-activated K(+) currents) and outward K(+) currents. P2-purinergic stimulation increases cAMP by activating adenylyl cyclase isoform V. It also involves tyrosine kinases to activate phospholipase C-gamma to produce inositol 1,4,5-trisphosphate and Cl(-)/HCO(3)(-) exchange to induce a large transient acidosis. No clear correlation is presently possible between an effect and the activation of a given P2-receptor subtype in cardiomyocytes. ATP itself is generally a positive inotropic agent. Upon rapid application to cells, ATP induces various forms of arrhythmia. At the tissue level, arrhythmia could be due to slowing of electrical spread after both Na(+) current decrease and cell-to-cell uncoupling as well as cell depolarization and Ca(2+) current increase. In as much as the information is available, this review also reports analog effects of UTP and diadenosine polyphosphates.
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Affiliation(s)
- G Vassort
- Institut National de la Santé et de la Recherche Médicale U. 390, Centre Hospitalier Universitaire Arnaud de Villeneuve, Montpellier, France.
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41
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Insel PA, Ostrom RS, Zambon AC, Hughes RJ, Balboa MA, Shehnaz D, Gregorian C, Torres B, Firestein BL, Xing M, Post SR. P2Y receptors of MDCK cells: epithelial cell regulation by extracellular nucleotides. Clin Exp Pharmacol Physiol 2001; 28:351-4. [PMID: 11339212 DOI: 10.1046/j.1440-1681.2001.03452.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Madin-Darby canine kidney (MDCK) cells, a well- differentiated renal epithelial cell line derived from distal tubule/collecting duct, respond to extracellular nucleotides by altering ion flux and the production of arachidonic acid-derived products, in particular prostaglandin E2 (PGE2). Our work has defined the receptors and signalling events involved in such responses. 2. We have found evidence for expression of at least three P2Y receptor subtypes (P2Y1, P2Y2 and P2Y11) in MDCK-D1 cells, a subclone from parental MDCK. 3. These receptors appear to couple to increases in calcium and protein kinase C activity, probably via a Gq/G11-mediated activation of phospholipase C. 4. In addition, P2Y receptor activation can promote a prominent increase in cAMP. This includes both a P2Y2 receptor-mediated cyclo-oxygenase (COX)-dependent component and another COX-independent component mediated by other P2Y receptors. 5. We have documented that changing media in which cells are grown releases ATP and, in turn, activates P2Y receptors. Such release of ATP contributes in a major way to basal cAMP levels in these cells. 6. The data indicate that MDCK cells are a useful model to define the regulation of epithelial cells by extracellular nucleotides. Of particular note, spontaneous or stretch-induced release of ATP and subsequent activation of one or more P2Y receptors contributes to establishing the basal activity of signalling pathways.
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Affiliation(s)
- P A Insel
- Department of Pharmacology, University of California, San Diego, La Jolla 92093-0636, USA.
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42
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Jeyaseelan S, Kannan MS, Hsuan SL, Singh AK, Walseth TF, Maheswaran SK. Pasteurella (Mannheimia) haemolytica leukotoxin-induced cytolysis of bovine leukocytes: role of arachidonic acid and its regulation. Microb Pathog 2001; 30:59-69. [PMID: 11162186 DOI: 10.1006/mpat.2000.0410] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pasteurella (Mannheimia) haemolytica leukotoxin (Lkt) is the major factor that contributes to lung injury in bovine pneumonic pasteurellosis. Lkt is a pore-forming exotoxin that has the unique property of inducing cytolysis only in ruminant leukocytes and platelets. Cytolysis of many cell types is mediated by arachidonic acid (AA) and its generation by phospholipases is regulated by G-protein-coupled receptors. However, the contribution of Lkt-induced AA generation to cytolysis and the signalling cascade underlying AA generation in bovine leukocytes have not been determined. We have determined whether AA mediates Lkt-induced cytolysis and delineated the signalling mechanisms underlying AA generation in bovine leukocytes. Bovine lymphoma cells were used as an experimental system to investigate the Lkt-induced [(3)H] AA release, an index of AA generation and lactate dehydrogenase release, an index of cytolysis. The results indicate that Lkt induces AA release and cytolysis in a concentration- and time-dependent fashion. The AA analog, 5,8,11,14-eicosatetraynoic acid inhibited Lkt-induced cytolysis, but not AA release. Lkt-induced AA release and cytolysis were inhibited by pertussis toxin, inhibitors of cytosolic phospholipase A(2)(cPLA(2)), phospholipase C and protein kinase C (PKC), and by chelation of intracellular calcium. Furthermore, Western blot analysis revealed the presence of G(i), G(s)and G(q)type G-proteins. These results demonstrate that AA metabolites from cPLA(2)activation contribute to Lkt-induced cytolysis and G(i)type G-proteins, Ca(2+)and PKC, regulate the cPLA(2)activity.
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Affiliation(s)
- S Jeyaseelan
- Department of Veterinary PathoBiology, College of Veterinary Medicine, St. Paul, MN 55108, USA
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43
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Teixeira M, Bernard C, Ferrary E, Butlen D. Purine and pyrimidine nucleotide-sensitive phospholipase A(2) in ampulla from frog semicircular canal. Am J Physiol Regul Integr Comp Physiol 2001; 280:R519-26. [PMID: 11208583 DOI: 10.1152/ajpregu.2001.280.2.r519] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was attempted to characterize pharmacologically the P2Y receptors triggering phospholipase A(2) (PLA(2)) activation in ampulla from frog semicircular canal. A microassay was developed to screen the abilities of UTP analogs to stimulate [(3)H]arachidonic acid release by labeled ampullas. At 26 degrees C UTP induced a dose-dependent and saturable increase of PLA(2) activity (apparent activation constant 1.3 +/- 0.4 microM, Hill coefficient 0.9 +/- 0.2, maximal stimulating factor 2.0 +/- 0.1). The rank order of potency of agonists for PLA(2) activation was UTP > or = UDP > adenosine 5'-O-(2-thiodiphosphate) = adenosine 5'-O-(3-thiotriphosphate) > or = ATP = 2-methylthio-ATP > or = ADP = diadenosine tetraphosphate > or = alpha,beta-methylene-ATP = CTP > 2' and 3'-O-(4-benzoylbenzoyl)-ATP > or = AMP = UMP >> uridine and adenosine. UTP- and 2-methylthio-ATP-induced PLA(2) activations were inhibited by U-73122, GF-109203X, and methyl arachidonyl fluorophosphate. Basal activity was stimulated by phorbol ester and epinephrine and reduced by vasotocin, isoproterenol, prostaglandin E(2), cAMP, and forskolin. H-89 restored the cAMP- and forskolin-inhibited PLA(2) activities. Results indicate that P2Y receptor-mediated PLA(2) stimulation requires phopholipase C and protein kinase C activations and basal activity is inhibited by agonist-stimulated cAMP-dependent mechanisms.
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Affiliation(s)
- M Teixeira
- Institut National de la Santé et de la Recherche Médicale, Unité 426, Faculté de Médecine Xavier Bichat, 75870 Paris Cedex 18, France
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Zambon AC, Hughes RJ, Meszaros JG, Wu JJ, Torres B, Brunton LL, Insel PA. P2Y(2) receptor of MDCK cells: cloning, expression, and cell-specific signaling. Am J Physiol Renal Physiol 2000; 279:F1045-52. [PMID: 11097622 DOI: 10.1152/ajprenal.2000.279.6.f1045] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Madin-Darby canine kidney (MDCK)-D1 cells, a canine renal epithelial cell line, co-express at least three different P2Y receptor subtypes: P2Y(1), P2Y(2), and P2Y(11) (24). Stimulation of P2Y receptors in these cells results in the release of arachidonic acid (AA) and metabolites and the elevation of intracellular cAMP. To define in more precise terms the signaling contributed by the MDCK-D1 P2Y(2) (cP2Y(2)) receptor, we have cloned and heterologously expressed it in CF2Th (canine thymocyte) cells, a P2Y(2)-null cell. Analysis by RT-PCR indicated that canine P2Y(2) receptors are expressed in skeletal muscle, spleen, kidney, lung, and liver. When expressed in CF2Th cells, cP2Y(2) receptors promoted phospholipase C-mediated phosphatidylinositol (PI) hydrolysis [uridine 5'-triphosphate > or = ATP > adenosine 5'-diphosphate > 2MT-ATP] and mobilization of intracellular Ca(2+). In contrast to their actions in MDCK-D1 cells, cP2Y(2) receptors did not stimulate formation of cAMP or AA release when expressed in CF2Th cells. The data indicate that cell setting plays an essential role in the ability of P2Y receptors to regulate AA release and cAMP formation. In particular, renal epithelial cells preferentially express components critical for cP2Y(2)-induced cAMP formation, including the expression of enzymes involved in the generation and metabolism of AA and receptors that respond to PGE(2).
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Affiliation(s)
- A C Zambon
- Department of Pharmacology, Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, California 92093-0636, USA
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Wilson SM, Lee SC, Shook S, Pappone PA. ATP and beta-adrenergic stimulation enhance voltage-gated K current inactivation in brown adipocytes. Am J Physiol Cell Physiol 2000; 279:C1847-58. [PMID: 11078700 DOI: 10.1152/ajpcell.2000.279.6.c1847] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sympathetic activation of brown fat thermogenesis stimulates adrenergic and purinergic receptors. We examined the effects of extracellular ATP and beta-adrenergic agonists on voltage-activated K currents (IKv) in voltage-clamped rat brown adipocytes. ATP or the beta-adrenergic agonist isoproterenol increased the development of IKv inactivation during depolarizing voltage steps in perforated patch-clamped cells. The effects on inactivation developed slowly in the presence of agonist and continued to increase for long times following agonist washout. 8-bromo-cAMP or forskolin had similar effects on IKv inactivation. Development of IKv inactivation during depolarizations was consistently enhanced by ATP or beta-adrenergic stimulation in perforated-patch voltage-clamped cells but was not altered by these agents in whole cell recordings, suggesting that cytosolic factors are necessary for inactivation modulation. In either recording configuration, ATP or isoproterenol shifted the activation voltage dependence of IKv to more negative potentials, indicating the activation effect is mediated by a different pathway. Since both P2 purinergic and beta-adrenergic signaling pathways generate fatty acids, we tested whether fatty acids could reproduce these modulations of IKv. Linoleic or arachidonic acid applied in whole cell recordings had effects similar to those of ATP or isoproterenol in perforated-patch experiments. These results are consistent with the possibility that beta-adrenergic and P2 receptor stimulation modulate IKv through generation of fatty acids.
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Affiliation(s)
- S M Wilson
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
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Dempsey EC, Newton AC, Mochly-Rosen D, Fields AP, Reyland ME, Insel PA, Messing RO. Protein kinase C isozymes and the regulation of diverse cell responses. Am J Physiol Lung Cell Mol Physiol 2000; 279:L429-38. [PMID: 10956616 DOI: 10.1152/ajplung.2000.279.3.l429] [Citation(s) in RCA: 514] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Individual protein kinase C (PKC) isozymes have been implicated in many cellular responses important in lung health and disease, including permeability, contraction, migration, hypertrophy, proliferation, apoptosis, and secretion. New ideas on mechanisms that regulate PKC activity, including the identification of a novel PKC kinase, 3-phosphoinositide-dependent kinase-1 (PDK-1), that regulates phosphorylation of PKC, have been advanced. The importance of targeted translocation of PKC and isozyme-specific binding proteins (like receptors for activated C-kinase and caveolins) is well established. Phosphorylation state and localization are now thought to be key determinants of isozyme activity and specificity. New concepts on the role of individual PKC isozymes in proliferation and apoptosis are emerging. Opposing roles for selected isozymes in the same cell system have been defined. Coupling to the Wnt signaling pathway has been described. Phenotypes for PKC knockout mice have recently been reported. More specific approaches for studying PKC isozymes and their role in cell responses have been developed. Strengths and weaknesses of different experimental strategies are reviewed. Future directions for investigation are identified.
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Affiliation(s)
- E C Dempsey
- Cardiovascular Pulmonary Research Laboratory, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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Ekokoski E, Dugué B, Vainio M, Vainio PJ, Törnquist K. Extracellular ATP-mediated phospholipase A(2) activation in rat thyroid FRTL-5 cells: regulation by a G(i)/G(o) protein, Ca(2+), and mitogen-activated protein kinase. J Cell Physiol 2000; 183:155-62. [PMID: 10737891 DOI: 10.1002/(sici)1097-4652(200005)183:2<155::aid-jcp2>3.0.co;2-r] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We investigated the mechanism of phospholipase A(2) (PLA(2)) activation in response to the P2 receptor agonist ATP in rat thyroid FRTL-5 cells. The PLA(2) activity was determined by measuring the release of [(3)H]-arachidonic acid (AA) from prelabeled cells. ATP evoked a dose- and time-dependent AA release. This release was totally inhibited by pertussis toxin (PTX) treatment, indicating the involvement of a G(i)/G(o) protein. The AA release was also diminished by chelating extracellular Ca(2+) with EGTA or by inhibiting influx of Ca(2+) using Ni(2+). Although the activation of protein kinase C (PKC) by 12-phorbol 13-myristate acetate (PMA) alone did not induce any AA release, the ATP-evoked AA release was significantly reduced when PKC was inhibited by GF109203X or by a long incubation with PMA to downregulate PKC. Both the ATP-evoked AA release and the mitogen-activated protein kinase (MAP kinase) phosphorylation were decreased by the MAP kinase kinase (MEK) inhibitor PD98059. Furthermore, the ATP-evoked MAP kinase phosphorylation was also inhibited by GF109203X and by downregulation of PKC, suggesting a PKC-mediated activation of MAP kinase. Inhibiting Src-like kinases by PP1 attenuated both the MAP kinase phosphorylation and the AA release. These results suggest that these kinases are involved in the regulation of MAP kinase and PLA(2) activation. Elevation of intracellular cAMP by TSH or by dBucAMP did not induce a phosphorylation of MAP kinase. Furthermore, neither the ATP-evoked AA release nor the MAP kinase phosphorylation were attenuated by TSH or dBucAMP. Taken together, our results suggest that ATP regulates the activation of PLA(2) by a G(i)/G(o) protein-dependent mechanism. Moreover, Ca(2+), PKC, MAP kinase, and Src-like kinases are also involved in this regulatory process.
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Affiliation(s)
- E Ekokoski
- Department of Biosciences, Division of Animal Physiology, University of Helsinki, Helsinki, Finland
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Ostrom RS, Gregorian C, Insel PA. Cellular release of and response to ATP as key determinants of the set-point of signal transduction pathways. J Biol Chem 2000; 275:11735-9. [PMID: 10766795 DOI: 10.1074/jbc.275.16.11735] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The determinants of "basal" activity of signaling pathways regulating cellular responses are poorly defined. One possibility is that cells release factors to establish the set-point of such pathways. Here we show that treatment of Madin-Darby canine kidney cells with the nucleotidase apyrase decreases basal arachidonic acid release and cAMP production 30-40% and that inhibitors of P2Y receptor action also affect basal and forskolin-stimulated cAMP accumulation. Changing medium prominently increases extracellular levels of ATP in Madin-Darby canine kidney, COS-7, and HEK-293 cells. Mechanical stimulation of ATP release likely occurs in virtually every experimental protocol with cultured cells, implicating such release and P2Y receptor activation as critical in establishing the set-point for signal transduction pathways.
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Affiliation(s)
- R S Ostrom
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA.
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Gagnon F, Hamet P, Orlov SN. Na+,K+ pump and Na+-coupled ion carriers in isolated mammalian kidney epithelial cells: regulation by protein kinase C. Can J Physiol Pharmacol 1999. [DOI: 10.1139/y99-041] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
This review updates our current knowledge on the regulation of Na+/H+ exchanger, Na+,K+,Cl- cotransporter, Na+,Pi cotransporter, and Na+,K+ pump in isolated epithelial cells from mammalian kidney by protein kinase C (PKC). In cells derived from different tubule segments, an activator of PKC, 4beta-phorbol 12-myristate 13-acetate (PMA), inhibits apical Na+/H+ exchanger (NHE3), Na+,Pi cotransport, and basolateral Na+,K+ cotransport (NKCC1) and augments Na+,K+ pump. In PMA-treated proximal tubules, activation of Na+,K+ pump probably plays a major role in increased reabsorption of salt and osmotically obliged water. In Madin-Darby canine kidney (MDCK) cells, which are highly abundant with intercalated cells from the collecting duct, PMA completely blocks Na+,K+,Cl- cotransport and decreases the activity of Na+,Pi cotransport by 30-40%. In these cells, agonists of P2 purinoceptors inhibit Na+,K+,Cl- and Na+,Pi cotransport by 50-70% via a PKC-independent pathway. In contrast with MDCK cells, in epithelial cells derived from proximal and distal tubules of the rabbit kidney, Na+,K+,Cl- cotransport is inhibited by PMA but is insensitive to P2 receptor activation. In proximal tubules, PKC-induced inhibition of NHE3 and Na+,Pi cotransporter can be triggered by parathyroid hormone. Both PKC and cAMP signaling contribute to dopaminergic inhibition of NHE3 and Na+,K+ pump. The receptors triggering PKC-mediated activation of Na+,K+ pump remain unknown. Recent data suggest that the PKC signaling system is involved in abnormalities of dopaminergic regulation of renal ion transport in hypertension and in the development of diabetic complications. The physiological and pathophysiological implications of PKC-independent regulation of renal ion transporters by P2 purinoceptors has not yet been examined.Key words: Na+/H+ exchanger, Na+,K+,Cl- and Na+,Pi cotransporters, Na+,K+ pump, protein kinase C, P2 purinoceptor.
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Abstract
In recent years, there has been great interest in the study of phospholipid metabolism in intact cell systems. Such an interest arises mainly from the discovery that cellular membrane phospholipids serve not only in structural roles, but are also reservoirs of preformed second messenger molecules with key roles in cellular signaling. These second messenger molecules are generated by agonist-induced activation and secretion of intracellular and extracellular phospholipases, respectively, i.e. enzymes that cleave ester bonds within phospholipids. Prominent members of the large collection of signal-activated phospholipases are the phospholipase A2s. These enzymes hydrolyze the sn-2 ester bond of phospholipids, releasing a free fatty acid and a lysophospholipid, both of which may alter cell function. In addition to its role in cellular signaling, phospholipase A2 has recently been recognized to be involved in a wide number of pathophysiological situations, ranging from systemic and acute inflammatory conditions to cancer. A growing number of pharmacologic inhibitors will help define the role of particular phospholipase A2s in signaling cascades.
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Affiliation(s)
- J Balsinde
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla 92093, USA
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