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Duszyc K, von Pein JB, Ramnath D, Currin-Ross D, Verma S, Lim F, Sweet MJ, Schroder K, Yap AS. Apical extrusion prevents apoptosis from activating an acute inflammatory program in epithelia. Dev Cell 2023; 58:2235-2248.e6. [PMID: 37647898 DOI: 10.1016/j.devcel.2023.08.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 06/20/2023] [Accepted: 08/07/2023] [Indexed: 09/01/2023]
Abstract
Apoptosis is traditionally considered to be an immunologically silent form of cell death. Multiple mechanisms exist to ensure that apoptosis does not stimulate the immune system to cause inflammation or autoimmunity. Against this expectation, we now report that epithelia are programmed to provoke, rather than suppress, inflammation in response to apoptosis. We found that an acute inflammatory response led by neutrophils occurs in zebrafish and cell culture when apoptotic epithelial cells cannot be expelled from the monolayer by apical extrusion. This reflects an intrinsic circuit where ATP released from apoptotic cells stimulates epithelial cells in the immediate vicinity to produce interleukin-8 (IL-8). Apical extrusion therefore prevents inappropriate epithelial inflammation by physically eliminating apoptotic cells before they can activate this pro-inflammatory circuit. This carries the implication that epithelia may be predisposed to inflammation, elicited by sporadic or induced apoptosis, if apical extrusion is compromised.
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Affiliation(s)
- Kinga Duszyc
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia.
| | - Jessica B von Pein
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Divya Ramnath
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Denni Currin-Ross
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Suzie Verma
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Fayth Lim
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Matthew J Sweet
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Kate Schroder
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | - Alpha S Yap
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia.
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2
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Sophocleous RA, Miles NA, Ooi L, Sluyter R. P2Y 2 and P2X4 Receptors Mediate Ca 2+ Mobilization in DH82 Canine Macrophage Cells. Int J Mol Sci 2020; 21:ijms21228572. [PMID: 33202978 PMCID: PMC7696671 DOI: 10.3390/ijms21228572] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 11/11/2020] [Accepted: 11/12/2020] [Indexed: 02/08/2023] Open
Abstract
Purinergic receptors of the P2 subclass are commonly found in human and rodent macrophages where they can be activated by adenosine 5'-triphosphate (ATP) or uridine 5'-triphosphate (UTP) to mediate Ca2+ mobilization, resulting in downstream signalling to promote inflammation and pain. However, little is understood regarding these receptors in canine macrophages. To establish a macrophage model of canine P2 receptor signalling, the expression of these receptors in the DH82 canine macrophage cell line was determined by reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. P2 receptor function in DH82 cells was pharmacologically characterised using nucleotide-induced measurements of Fura-2 AM-bound intracellular Ca2+. RT-PCR revealed predominant expression of P2X4 receptors, while immunocytochemistry confirmed predominant expression of P2Y2 receptors, with low levels of P2X4 receptor expression. ATP and UTP induced robust Ca2+ responses in the absence or presence of extracellular Ca2+. ATP-induced responses were only partially inhibited by the P2X4 receptor antagonists, 2',3'-O-(2,4,6-trinitrophenyl)-ATP (TNP-ATP), paroxetine and 5-BDBD, but were strongly potentiated by ivermectin. UTP-induced responses were near completely inhibited by the P2Y2 receptor antagonists, suramin and AR-C118925. P2Y2 receptor-mediated Ca2+ mobilization was inhibited by U-73122 and 2-aminoethoxydiphenyl borate (2-APB), indicating P2Y2 receptor coupling to the phospholipase C and inositol triphosphate signal transduction pathway. Together this data demonstrates, for the first time, the expression of functional P2 receptors in DH82 canine macrophage cells and identifies a potential cell model for studying macrophage-mediated purinergic signalling in inflammation and pain in dogs.
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Affiliation(s)
- Reece Andrew Sophocleous
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia; (R.A.S.); (N.A.M.); (L.O.)
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Nicole Ashleigh Miles
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia; (R.A.S.); (N.A.M.); (L.O.)
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Lezanne Ooi
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia; (R.A.S.); (N.A.M.); (L.O.)
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Ronald Sluyter
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia; (R.A.S.); (N.A.M.); (L.O.)
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Correspondence: ; Tel.: +612-4221-5508
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Thongon N, Chamniansawat S. The inhibitory role of purinergic P2Y receptor on Mg 2+ transport across intestinal epithelium-like Caco-2 monolayer. J Physiol Sci 2019; 69:129-141. [PMID: 30032468 PMCID: PMC10717015 DOI: 10.1007/s12576-018-0628-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 07/13/2018] [Indexed: 02/06/2023]
Abstract
The mechanism of proton pump inhibitors (PPIs) suppressing intestinal Mg2+ uptake is unknown. The present study aimed to investigate the role of purinergic P2Y receptors in the regulation of Mg2+ absorption in normal and omeprazole-treated intestinal epithelium-like Caco-2 monolayers. Omeprazole suppressed Mg2+ transport across Caco-2 monolayers. An agonist of the P2Y2 receptor, but not the P2Y4 or P2Y6 receptor, suppressed Mg2+ transport across control and omeprazole-treated monolayers. Omeprazole enhanced P2Y2 receptor expression in Caco-2 cells. Forskolin and P2Y2 receptor agonist markedly enhanced apical HCO3- secretion by control and omeprazole-treated monolayers. The P2Y2 receptor agonist suppressed Mg2+ transport and stimulated apical HCO3- secretion through the Gq-protein coupled-phospholipase C (PLC) dependent pathway. Antagonists of cystic fibrosis transmembrane conductance regulator (CFTR) and Na+-HCO3- cotransporter-1 (NBCe1) could nullify the inhibitory effect of P2Y2 receptor agonist on Mg2+ transport across control and omeprazole-treated Caco-2 monolayers. Our results propose an inhibitory role of P2Y2 on intestinal Mg2+ absorption.
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Affiliation(s)
- Narongrit Thongon
- Division of Physiology, Department of Biomedical Sciences, Faculty of Allied Health Sciences, Burapha University, 169 Long-Hard Bangsaen Rd, Saensook, Muang, Chonburi, 20131, Thailand.
| | - Siriporn Chamniansawat
- Division of Anatomy, Department of Biomedical Sciences, Faculty of Allied Health Sciences, Burapha University, 169 Long-Hard Bangsaen Rd, Saensook, Muang, Chonburi, 20131, Thailand
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4
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Dreisig K, Kornum BR. A critical look at the function of the P2Y11 receptor. Purinergic Signal 2016; 12:427-37. [PMID: 27246167 DOI: 10.1007/s11302-016-9514-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 04/17/2016] [Indexed: 11/30/2022] Open
Abstract
The P2Y11 receptor is a member of the purinergic receptor family. It has been overlooked, somewhat due to the lack of a P2ry11 gene orthologue in the murine genome, which prevents the generation of knockout mice, which have been so helpful for defining the roles of other P2Y receptors. Furthermore, some of the studies reported to date have methodological shortcomings, making it difficult to determine the function of P2Y11 with certainty. In this review, we discuss the lack of a murine "P2Y11-like receptor" and highlight the limitations of the currently available methods used to investigate the P2Y11 receptor. These methods include protein recognition with antibodies that show very little specificity, gene expression studies that completely overlook the existence of a fusion transcript between the adjacent PPAN gene and P2RY11, and agonists/antagonists reported to be specific for the P2Y11 receptor but which have not been tested for activity on numerous other adenosine 5'-triphosphate (ATP)-binding receptors. We suggest a set of criteria for evaluating whether a dataset describes effects mediated by the P2Y11 receptor. Following these criteria, we conclude that the current evidence suggests a role for P2Y11 in immune activation with cell type-specific effects.
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Affiliation(s)
- Karin Dreisig
- Molecular Sleep Laboratory, Department of Clinical Biochemistry, Rigshospitalet, Glostrup, Denmark
| | - Birgitte Rahbek Kornum
- Molecular Sleep Laboratory, Department of Clinical Biochemistry, Rigshospitalet, Glostrup, Denmark.
- Danish Center for Sleep Medicine, Department of Clinical Neurophysiology, Rigshospitalet, Glostrup, Denmark.
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Franco M, Bautista-Pérez R, Pérez-Méndez O. Purinergic receptors in tubulointerstitial inflammatory cells: a pathophysiological mechanism of salt-sensitive hypertension. Acta Physiol (Oxf) 2015; 214:75-87. [PMID: 25683649 DOI: 10.1111/apha.12471] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 10/28/2014] [Accepted: 02/09/2015] [Indexed: 12/24/2022]
Abstract
Recent studies have suggested that both the tubulointerstitial inflammatory cells and the activation of purinergic receptors integrate common mechanisms that result in salt-sensitive hypertension. The basis of this hypothesis is that renal endothelial cells release ATP in response to shear stress in the setting of hypertension. It has been demonstrated that the over-expression and activation of the P2X7, P2Y12 and P2X1 receptors favour the elevation of blood pressure induced by high-salt intake. In addition, the release of interleukins and inflammatory mediators in the tubulointerstitial area appears to be related to the activation of these receptors. Renal vasoconstriction and tubulointerstitial injury develop as a result, which increase sodium reabsorption by epithelial cells. Consistent with these effects, the reduction of tubulointerstitial inflammation caused by immunosuppressants, such as mycophenolate mofetil, prevents the development of salt-sensitive hypertension. Also, P2X7-receptor knockout mice develop minor renal injury when hypertension is induced via the administration of deoxycorticosterone acetate and a high-salt diet. In the setting of angiotensin II-induced hypertension, which is an early stage in the development of salt-sensitive hypertension, an acute blockade with the specific, non-selective P2 antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid prevented the renal vasoconstriction induced by angiotensin II. In addition, it normalized glomerular haemodynamics and restored sodium excretion to control values. These findings suggest that chronic administration of P2 purinergic antagonists may prevent the deleterious effects of purinergic receptors during the development of salt-sensitive hypertension.
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Affiliation(s)
- M. Franco
- Renal Physiopathology Laboratory; Department of Nephrology; Instituto Nacional de Cardiología Ignacio Chávez; México City Mexico
| | - R. Bautista-Pérez
- Renal Physiopathology Laboratory; Department of Nephrology; Instituto Nacional de Cardiología Ignacio Chávez; México City Mexico
- Molecular Biology Department; Instituto Nacional de Cardiología Ignacio Chávez; México City Mexico
| | - O. Pérez-Méndez
- Molecular Biology Department; Instituto Nacional de Cardiología Ignacio Chávez; México City Mexico
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DuBose DR, Wolff SC, Qi AD, Naruszewicz I, Nicholas RA. Apical targeting of the P2Y(4) receptor is directed by hydrophobic and basic residues in the cytoplasmic tail. Am J Physiol Cell Physiol 2013; 304:C228-39. [PMID: 23054062 PMCID: PMC3566436 DOI: 10.1152/ajpcell.00251.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 10/03/2012] [Indexed: 11/22/2022]
Abstract
The P2Y(4) receptor is selectively targeted to the apical membrane in polarized epithelial cell lines and has been shown to play a key role in intestinal chloride secretion. In this study, we delimit a 23 amino acid sequence within the P2Y(4) receptor C-tail that directs its apical targeting. Using a mutagenesis approach, we found that four hydrophobic residues near the COOH-terminal end of the signal are necessary for apical sorting, whereas two basic residues near the NH(2)-terminal end of the signal are involved to a lesser extent. Interestingly, mutation of the key hydrophobic residues results in a basolateral enrichment of the receptor construct, suggesting that the apical targeting sequence may prevent insertion or disrupt stability of the receptor at the basolateral membrane. The signal is not sequence specific, as an inversion of the 23 amino acid sequence does not disrupt apical targeting. We also show that the apical targeting sequence is an autonomous signal and is capable of redistributing the normally basolateral P2Y(12) receptor, suggesting that the apical signal is dominant over the basolateral signal in the main body of the P2Y(12) receptor. The targeting sequence is unique to the P2Y(4) receptor, and sequence alignments of the COOH-terminal tail of mammalian orthologs reveal that the hydrophobic residues in the targeting signal are highly conserved. These data define the novel apical sorting signal of the P2Y(4) receptor, which may represent a common mechanism for trafficking of epithelial transmembrane proteins.
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Affiliation(s)
- D Ross DuBose
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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7
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Weisz OA. High-tailing it to the apical surface. Focus on "Apical targeting of the P2Y(4) receptor is directed by hydrophobic and basic residues in the cytoplasmic tail". Am J Physiol Cell Physiol 2013; 304:C226-7. [PMID: 23076794 DOI: 10.1152/ajpcell.00327.2012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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8
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Furuya S, Furuya K. Roles of substance P and ATP in the subepithelial fibroblasts of rat intestinal villi. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 304:133-89. [PMID: 23809436 DOI: 10.1016/b978-0-12-407696-9.00003-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ingestion of food and water induces chemical and mechanical signals that trigger peristaltic reflexes and also villous movement in the gut. In the intestinal villi, subepithelial fibroblasts under the epithelium form contractile cellular networks and closely contact to the varicosities of substance P and nonsubstance P afferent neurons. Subepithelial fibroblasts of the duodenal villi possess purinergic receptor P2Y1 and tachykinin receptor NK1. ATP and substance P induce increase in intracellular Ca(2+) and cell contraction in subepithelial fibroblasts. They are highly mechanosensitive and release ATP by mechanical stimuli. Released ATP spreads to form an ATP "cloud" with nearly 1μM concentration and activates the surroundings via P2Y1 and afferent neurons via P2X receptors. These findings suggest that villous subepithelial fibroblasts and afferent neurons interact via ATP and substance P. This mutual interaction may play important roles in the signal transduction of mechano reflex pathways including a coordinate villous movement and also in the maturation of the structure and function of the intestinal villi.
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Affiliation(s)
- Sonoko Furuya
- Section of Brain Structure Information, Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Japan.
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Erb L, Weisman GA. Coupling of P2Y receptors to G proteins and other signaling pathways. ACTA ACUST UNITED AC 2012; 1:789-803. [PMID: 25774333 DOI: 10.1002/wmts.62] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
P2Y receptors are G protein-coupled receptors (GPCRs) that are activated by adenine and uridine nucleotides and nucleotide sugars. There are eight subtypes of P2Y receptors (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and P2Y14), which activate intracellular signaling cascades to regulate a variety of cellular processes, including proliferation, differentiation, phagocytosis, secretion, nociception, cell adhesion, and cell migration. These signaling cascades operate mainly by the sequential activation or deactivation of heterotrimeric and monomeric G proteins, phospholipases, adenylyl and guanylyl cyclases, protein kinases, and phosphodiesterases. In addition, there are numerous ion channels, cell adhesion molecules, and receptor tyrosine kinases that are modulated by P2Y receptors and operate to transmit an extracellular signal to an intracellular response.
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Affiliation(s)
- Laurie Erb
- Department of Biochemistry, Life Sciences Center, University of Missouri-Columbia, Columbia, MO 65211, USA
| | - Gary A Weisman
- Department of Biochemistry, Life Sciences Center, University of Missouri-Columbia, Columbia, MO 65211, USA
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10
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Jongsma M, Matas-Rico E, Rzadkowski A, Jalink K, Moolenaar WH. LPA is a chemorepellent for B16 melanoma cells: action through the cAMP-elevating LPA5 receptor. PLoS One 2011; 6:e29260. [PMID: 22195035 PMCID: PMC3237609 DOI: 10.1371/journal.pone.0029260] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 11/23/2011] [Indexed: 01/08/2023] Open
Abstract
Lysophosphatidic acid (LPA), a lipid mediator enriched in serum, stimulates cell migration, proliferation and other functions in many cell types. LPA acts on six known G protein-coupled receptors, termed LPA1–6, showing both overlapping and distinct signaling properties. Here we show that, unexpectedly, LPA and serum almost completely inhibit the transwell migration of B16 melanoma cells, with alkyl-LPA(18∶1) being 10-fold more potent than acyl-LPA(18∶1). The anti-migratory response to LPA is highly polarized and dependent on protein kinase A (PKA) but not Rho kinase activity; it is associated with a rapid increase in intracellular cAMP levels and PIP3 depletion from the plasma membrane. B16 cells express LPA2, LPA5 and LPA6 receptors. We show that LPA-induced chemorepulsion is mediated specifically by the alkyl-LPA-preferring LPA5 receptor (GPR92), which raises intracellular cAMP via a noncanonical pathway. Our results define LPA5 as an anti-migratory receptor and they implicate the cAMP-PKA pathway, along with reduced PIP3 signaling, as an effector of chemorepulsion in B16 melanoma cells.
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Affiliation(s)
- Maikel Jongsma
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Elisa Matas-Rico
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Adrian Rzadkowski
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Kees Jalink
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Wouter H. Moolenaar
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
- * E-mail:
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Qi AD, Houston-Cohen D, Naruszewicz I, Harden TK, Nicholas RA. Ser352 and Ser354 in the carboxyl terminus of the human P2Y(1) receptor are required for agonist-promoted phosphorylation and internalization in MDCK cells. Br J Pharmacol 2011; 162:1304-13. [PMID: 21108629 PMCID: PMC3058163 DOI: 10.1111/j.1476-5381.2010.01135.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 09/23/2010] [Accepted: 10/26/2010] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The P2Y(1) receptor promotes chloride secretion in epithelial cells, a process critical for regulation of extracellular ion and fluid levels. Here we have examined the role of phosphorylation in agonist-induced internalization of P2Y(1) receptors. EXPERIMENTAL APPROACH A high-affinity radiolabelled antagonist, MRS2500, was used to quantify cell surface-binding sites of P2Y(1) receptors in Madin-Darby canine kidney (MDCK) epithelial cells, following exposure to agonists. The regions in the carboxyl terminus involved in both agonist-induced internalization of the receptor and its phosphorylation were identified by mutational analysis. KEY RESULTS Endogenous and stably expressed recombinant P2Y(1) receptors rapidly internalized with similar time courses in response to agonist in MDCK cells, ensuring that the levels of recombinant receptor achieved by retroviral infection did not adversely affect function of the internalization machinery. Four protein kinase C inhibitors of varying specificity did not affect internalization of recombinant receptors. Agonist-promoted internalization of a series of truncated P2Y(1) receptors identified a region between residues 349 and 359 in the carboxyl terminus as critical for regulation. Two amino acids within this region, Ser352 and Ser354, were shown to be both necessary and sufficient for agonist-promoted receptor phosphorylation and internalization. CONCLUSIONS AND IMPLICATIONS Our results firmly establish Ser352 and Ser354 in the carboxyl terminus of P2Y(1) receptors as critical residues for agonist-induced receptor internalization in MDCK cells. As the mechanism mediating this regulation requires phosphorylation of these key residues, the relevant receptor-regulated protein kinase can now be identified.
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Affiliation(s)
- Ai-Dong Qi
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7365, USA
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Molecular pharmacology, physiology, and structure of the P2Y receptors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 61:373-415. [PMID: 21586365 DOI: 10.1016/b978-0-12-385526-8.00012-6] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The P2Y receptors are a widely expressed group of eight nucleotide-activated G protein-coupled receptors (GPCRs). The P2Y(1)(ADP), P2Y(2)(ATP/UTP), P2Y(4)(UTP), P2Y(6)(UDP), and P2Y(11)(ATP) receptors activate G(q) and therefore robustly promote inositol lipid signaling responses. The P2Y(12)(ADP), P2Y(13)(ADP), and P2Y(14)(UDP/UDP-glucose) receptors activate G(i) leading to inhibition of adenylyl cyclase and to Gβγ-mediated activation of a range of effector proteins including phosphoinositide 3-kinase-γ, inward rectifying K(+) (GIRK) channels, phospholipase C-β2 and -β3, and G protein-receptor kinases 2 and 3. A broad range of physiological responses occur downstream of activation of these receptors ranging from Cl(-) secretion by epithelia to aggregation of platelets to neurotransmission. Useful structural models of the P2Y receptors have evolved from extensive genetic analyses coupled with molecular modeling based on three-dimensional structures obtained for rhodopsin and several other GPCRs. Selective ligands have been synthesized for most of the P2Y receptors with the most prominent successes attained with highly selective agonist and antagonist molecules for the ADP-activated P2Y(1) and P2Y(12) receptors. The widely prescribed drug, clopidogrel, which results in irreversible blockade of the platelet P2Y(12) receptor, is the most important therapeutic agent that targets a P2Y receptor.
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Abstract
A thin layer of airway surface liquid (ASL) lines the entire surface of the lung and is the first point of contact between the lung and the environment. Surfactants contained within this layer are secreted in the alveolar region and are required to maintain a low surface tension and to prevent alveolar collapse. Mucins are secreted into the ASL throughout the respiratory tract and serve to intercept inhaled pathogens, allergens and toxins. Their removal by mucociliary clearance (MCC) is facilitated by cilia beating and hydration of the ASL by active ion transport. Throughout the lung, secretion, ion transport and cilia beating are under purinergic control. Pulmonary epithelia release ATP into the ASL which acts in an autocrine fashion on P2Y(2) (ATP) receptors. The enzymatic network describes in Chap. 2 then mounts a secondary wave of signaling by surface conversion of ATP into adenosine (ADO), which induces A(2B) (ADO) receptor-mediated responses. This chapter offers a comprehensive description of MCC and the extensive ramifications of the purinergic signaling network on pulmonary surfaces.
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14
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Wolff SC, Qi AD, Harden TK, Nicholas RA. Charged residues in the C-terminus of the P2Y1 receptor constitute a basolateral-sorting signal. J Cell Sci 2010; 123:2512-20. [PMID: 20592187 PMCID: PMC2894661 DOI: 10.1242/jcs.060723] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2010] [Indexed: 11/20/2022] Open
Abstract
The P2Y(1) receptor is localized to the basolateral membrane of polarized Madin-Darby canine kidney (MDCK) cells. In the present study, we identified a 25-residue region within the C-terminal tail (C-tail) of the P2Y(1) receptor that directs basolateral sorting. Deletion of this sorting signal caused redirection of the receptor to the apical membrane, indicating that the region from the N-terminus to transmembrane domain 7 (TM7) contains an apical-sorting signal that is overridden by a dominant basolateral signal in the C-tail. Location of the signal relative to TM7 is crucial, because increasing its distance from the end of TM7 resulted in loss of basolateral sorting. The basolateral-sorting signal does not use any previously established basolateral-sorting motifs, i.e. tyrosine-containing or di-hydrophobic motifs, for function, and it is functional even when inverted or when its amino acids are scrambled, indicating that the signal is sequence independent. Mutagenesis of different classes of amino acids within the signal identified charged residues (five basic and four acidic amino acids in 25 residues) as crucial determinants for sorting function, with amidated amino acids having a lesser role. Mutational analyses revealed that whereas charge balance (+1 overall) of the signal is unimportant, the total number of charged residues (nine), either positive or negative, is crucial for basolateral targeting. These data define a new class of targeting signal that relies on total charge and might provide a common mechanism for polarized trafficking of epithelial proteins.
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MESH Headings
- Amino Acid Sequence/genetics
- Amino Acids, Acidic/chemistry
- Amino Acids, Acidic/genetics
- Amino Acids, Basic/chemistry
- Amino Acids, Basic/genetics
- Animals
- Cell Line
- Cell Polarity/genetics
- Cloning, Molecular
- Dogs
- Epithelial Cells/metabolism
- Epithelial Cells/pathology
- Kidney/pathology
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation/genetics
- Protein Sorting Signals/genetics
- Protein Structure, Tertiary/genetics
- Protein Transport/genetics
- Receptors, Purinergic P2Y1/chemistry
- Receptors, Purinergic P2Y1/genetics
- Receptors, Purinergic P2Y1/metabolism
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Affiliation(s)
- Samuel C. Wolff
- Curriculum in Neurobiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
| | - Ai-Dong Qi
- Curriculum in Neurobiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
| | - T. Kendall Harden
- Curriculum in Neurobiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
| | - Robert A. Nicholas
- Curriculum in Neurobiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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Carter RL, Fricks IP, Barrett MO, Burianek LE, Zhou Y, Ko H, Das A, Jacobson KA, Lazarowski ER, Harden TK. Quantification of Gi-mediated inhibition of adenylyl cyclase activity reveals that UDP is a potent agonist of the human P2Y14 receptor. Mol Pharmacol 2009; 76:1341-8. [PMID: 19759354 DOI: 10.1124/mol.109.058578] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The P2Y14 receptor was initially identified as a G protein-coupled receptor activated by UDP-glucose and other nucleotide sugars. We have developed several cell lines that stably express the human P2Y14 receptor, allowing facile examination of its coupling to native Gi family G proteins and their associated downstream signaling pathways (J Pharmacol Exp Ther 330:162-168, 2009). In the current study, we examined P2Y14 receptor-dependent inhibition of cyclic AMP accumulation in human embryonic kidney (HEK) 293, C6 glioma, and Chinese hamster ovary (CHO) cells stably expressing this receptor. Not only was the human P2Y14 receptor activated by UDP-glucose, but it also was activated by UDP. The apparent efficacies of UDP and UDP-glucose were similar, and the EC50 values (74, 33, and 29 nM) for UDP-dependent activation of the P2Y14 receptor in HEK293, CHO, and C6 glioma cells, respectively, were similar to the EC50 values (323, 132, and 72 nM) observed for UDP-glucose. UDP and UDP-glucose also stimulated extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in P2Y14 receptor-expressing HEK293 cells but not in wild-type HEK293 cells. A series of analogs of UDP were potent P2Y14 receptor agonists, but the naturally occurring nucleoside diphosphates, CDP, GDP, and ADP exhibited agonist potencies over 100-fold less than that observed with UDP. Two UDP analogs were identified that selectively activate the P2Y14 receptor over the UDP-activated P2Y6 receptor, and these molecules stimulated phosphorylation of ERK1/2 in differentiated human HL-60 promyeloleukemia cells, which natively express the P2Y14 receptor but had no effect in wild-type HL-60 cells, which do not express the receptor. We conclude that UDP is an important cognate agonist of the human P2Y14 receptor.
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Affiliation(s)
- Rhonda L Carter
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC, USA
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16
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Fricks IP, Carter RL, Lazarowski ER, Harden TK. Gi-dependent cell signaling responses of the human P2Y14 receptor in model cell systems. J Pharmacol Exp Ther 2009; 330:162-8. [PMID: 19339661 DOI: 10.1124/jpet.109.150730] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Eight G protein-coupled receptors comprise the P2Y receptor family of cell signaling proteins. The goal of the current study was to define native cell signaling pathways regulated by the uridine nucleotide sugar-activated P2Y(14) receptor (P2Y(14)-R). The P2Y(14)-R was stably expressed in human embryonic kidney (HEK) 293 and C6 rat glioma cells by retroviral infection. Nucleotide sugar-dependent P2Y(14)-R activation was examined by measuring inhibition of forskolin-stimulated cAMP accumulation. The effect of P2Y(14)-R activation on mitogen-activated protein kinase signaling also was studied in P2Y(14)-HEK293 cells and in differentiated HL-60 human myeloid leukemia cells. UDP-Glc, UDP-galactose, UDP-glucuronic acid, and UDP-N-acetylglucosamine promoted inhibition of forskolin-stimulated cAMP accumulation in P2Y(14)-HEK293 and P2Y(14)-C6 cells, and this signaling effect was abolished by pretreatment of cells with pertussis toxin. Inhibition of cAMP formation by nucleotide sugars also was observed in direct assays of adenylyl cyclase activity in membranes prepared from P2Y(14)-C6 cells. UDP-Glc promoted concentration-dependent and pertussis toxin-sensitive extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in P2Y(14)-HEK293 cells. P2Y(14)-R mRNA was not observed in wild-type HL-60 cells but was readily detected in dimethyl sulfoxide-differentiated cells. Consistent with this observation, no effect of UDP-Glc was observed in wild-type HL-60 cells, but UDP-Glc-promoted pertussis toxin-sensitive activation of ERK1/2 occurred after differentiation. These results illustrate that the human P2Y(14)-R signals through G(i) to inhibit adenylyl cyclase, and P2Y(14)-R activation also leads to ERK1/2 activation. This work also identifies two stable P2Y(14)-R-expressing cell lines and differentiated HL-60 cells as model systems for the study of P2Y(14)-R-dependent signal transduction.
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Affiliation(s)
- Ingrid P Fricks
- Department of Pharmacology, University of North Carolina, School of Medicine, Chapel Hill, NC 27599, USA
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The transforming Rho family GTPase Wrch-1 disrupts epithelial cell tight junctions and epithelial morphogenesis. Mol Cell Biol 2008; 29:1035-49. [PMID: 19064640 DOI: 10.1128/mcb.00336-08] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Wrch-1, an atypical and transforming Rho GTPase, regulates cellular activities including proliferation and actin organization, but its functions and effectors remain poorly characterized. We show here that Wrch-1 distributes along the apical and basolateral membranes in MDCK cells and binds the cell polarity protein Par6 in a GTP-dependent manner. Activated Wrch-1 negatively regulates the kinetics of tight junction (TJ) assembly during epithelial cell polarization but has no detectable effect on overall cell polarity in confluent monolayers. It also causes a dramatic cytoskeletal reorganization and multilayering in cells grown in two-dimensional culture and disrupts cystogenesis of cells grown in three-dimensional (3D) culture. Similarly, short hairpin RNA-mediated knockdown of Wrch-1 perturbs cystogenesis in 3D culture, suggesting that tight regulation of Wrch-1 activity is necessary for normal epithelial morphogenesis. A weakly transforming effector domain mutant of activated Wrch-1 that inhibits Par6 binding abrogates the ability of Wrch-1 to disrupt TJ formation, actin organization, and epithelial morphogenesis. We hypothesize that Wrch-1-induced morphological and growth transformation may occur in part through Par6-mediated disruption of TJs and actin organization.
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18
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Wong AM, Chow AW, Au SC, Wong CC, Ko WH. Apical versus basolateral P2Y(6) receptor-mediated Cl(-) secretion in immortalized bronchial epithelia. Am J Respir Cell Mol Biol 2008; 40:733-45. [PMID: 19011163 DOI: 10.1165/rcmb.2008-0020oc] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Apical and/or basolateral membranes of polarized epithelia express P2Y receptors, which regulate the transport of fluid and electrolytes. In the airway, P2Y receptors modulate Cl(-) secretion through the phospholipase C and calcium signaling pathways. Recent evidence suggests that P2Y(6) receptors are expressed in bronchial epithelium and coupled to the cAMP/protein kinase A (PKA) pathways. We examined P2Y receptor subtype expression, including P2Y(6,) and the effect of extracellular nucleotides on basal short-circuit current (I(SC)) and intracellular calcium concentration ([Ca(2+)](i)) in a human bronchial epithelial cell line (16HBE14o-). Real-time PCR demonstrated P2Y(1), P2Y(2), P2Y(4), and P2Y(6) receptor expression and confirmed that transcript levels were not altered when cells were grown under varied conditions. It was determined that P2Y agonists (ATP, UTP, UDP) stimulated a concomitant increase in I(SC) and [Ca(2+)](i). Apical nucleotides stimulated an increase in [Ca(2+)](i) more efficiently than basolateral nucleotides; however, P2Y agonistic effects on I(SC) were greater when applied basolaterally. Since the P2Y(6) receptors differentially regulate apical and basolateral UDP-induced I(SC) and [Ca(2+)](i), we investigated membrane-resident P2Y(6) receptor functions using Cl(-) or K(+) channels blockers. Apical and basolateral UDP activation of I(SC) was inhibited by applying DIDS apically or TRAM-34 and clotrimazole basolaterally. Although both apical and basolateral UDP increased PKA activity, only apical UDP-induced I(SC) was sensitive to a CFTR inhibitor. These data demonstrate that P2Y agonists stimulate Ca(2+)-dependent Cl(-) secretion across human bronchial epithelia and that the cAMP/PKA pathway regulates apical but not basolateral P2Y(6) receptor-coupled ion transport in human bronchial epithelia.
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Affiliation(s)
- Alison M Wong
- Department of Physiology, The Chinese University of Hong Kong, Shatin, Hong Kong
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19
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Coupling of airway ciliary activity and mucin secretion to mechanical stresses by purinergic signaling. Respir Physiol Neurobiol 2008; 163:208-13. [PMID: 18635403 DOI: 10.1016/j.resp.2008.05.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 05/14/2008] [Accepted: 05/18/2008] [Indexed: 11/24/2022]
Abstract
The mucociliary clearance system is comprised of three components, ion transport activities controlling the height of airway surface liquid (ASL), mucin secretion, and ciliary activity. These activities in humans are controlled principally by local agonists, extracellular nucleotides and nucleosides released from the epithelium. Importantly, mechanical stresses stimulate goblet cell mucin secretion, ciliary beating, and Cl- and fluid secretion through mechanically induced nucleotide release. Emerging evidence also implicates co-secretion of nucleotides and mucin from goblet cells as a source of extracellular agonist. At rest, ATP is released onto airway surfaces at approximately 370fmol/mincm2, but only approximately 3% of released ATP is recovered in ASL. Secreted UTP meets with a similar fate. A wide variety of hydrolytic and transphosphorylating ecto-enzymes convert the triphosphate nucleotides into ADP, AMP, and adenosine, UDP, UMP, and uridine. Of these, ATP, adenosine, UTP, and UDP act as agonists at apical P2Y2 (ATP, UTP), P2Y6 (UDP), and A2B (adenosine) receptors on ciliated and/or goblet cells to regulate mucociliary clearance.
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Grbic DM, Degagné E, Langlois C, Dupuis AA, Gendron FP. Intestinal inflammation increases the expression of the P2Y6 receptor on epithelial cells and the release of CXC chemokine ligand 8 by UDP. THE JOURNAL OF IMMUNOLOGY 2008; 180:2659-68. [PMID: 18250478 DOI: 10.4049/jimmunol.180.4.2659] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Epithelial cells participate in the immune response of the intestinal mucosa. Extracellular nucleotides have been recognized as inflammatory molecules. We investigated the role of extracellular nucleotides and their associated P2Y receptors in the secretion of cytokines by epithelial cells. The effect of intestinal inflammation on P2Y(6) receptor expression was determined by PCR in the mouse, rat, and human. Localization of the P2Y(6) receptor was determined by immunofluorescence microscopy in the colon of normal and dextran sulfate sodium-treated mice. The effect of P2Y(6) activation by UDP on cytokine expression and release by epithelial cells was determined using a combination of Western blots, luciferase assays, RT-PCR, cytokine Ab arrays, and ELISA. Inflammation up-regulates P2Y(2) as well as P2Y(6) receptor expression in the mucosa of the colon of colitic mice. In vitro, we demonstrated that UDP could be released by Caco-2/15 cells. We have confirmed the increased expression of P2Y(6) by challenging intestinal epithelial cell-6 and Caco-2/15 cells with TNF-alpha and IFN-gamma and showing that stimulation of epithelial cells by UDP results in an increased expression and release of CXCL8 by an ERK1/2-dependent mechanism. The increase in CXCL8 expression was associated with a transcriptional activation by the P2Y(6) receptor. This study is the first report demonstrating the implication of P2Y receptors in the inflammatory response of intestinal epithelial cells. We show for the first time that P2Y(6), as well as P2Y(2), expression is increased by the stress associated with intestinal inflammation. These results demonstrate the emergence of extracellular nucleotide signaling in the orchestration of intestinal inflammation.
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Affiliation(s)
- Djordje M Grbic
- Canadian Institutes of Health Research Team on the Digestive Epithelium, Département d'Anatomie et de Biologie Cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, 3001 12th Avenue North, Sherbrooke, Québec, Canada
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21
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Buvinic S, Bravo-Zehnder M, Boyer JL, Huidobro-Toro JP, González A. Nucleotide P2Y1 receptor regulates EGF receptor mitogenic signaling and expression in epithelial cells. J Cell Sci 2008; 120:4289-301. [PMID: 18057028 DOI: 10.1242/jcs.03490] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Epidermal growth factor receptor (EGFR) function is transregulated by a variety of stimuli, including agonists of certain G-protein-coupled receptors (GPCRs). One of the most ubiquitous GPCRs is the P2Y(1) receptor (P2RY1, hereafter referred to as P2Y(1)R) for extracellular nucleotides, mainly ADP. Here, we show in tumoral HeLa cells and normal FRT epithelial cells that P2Y(1)R broadcasts mitogenic signals by transactivating the EGFR. The pathway involves PKC, Src and cell surface metalloproteases. Stimulation of P2Y(1)R for as little as 15-60 minutes triggers mitogenesis, mirroring the half-life of extracellular ADP. Apyrase degradation of extracellular nucleotides and drug inhibition of P2Y(1)R, both reduced basal cell proliferation of HeLa and FRT cells, but not MDCK cells, which do not express P2Y(1)R. Thus, cell-released nucleotides constitute strong mitogenic stimuli, which act via P2Y(1)R. Strikingly, MDCK cells ectopically expressing P2Y(1)R display a highly proliferative phenotype that depends on EGFR activity associated with an increased level of EGFR, thus disclosing a novel aspect of GPCR-mediated regulation of EGFR function. These results highlight a role of P2Y(1)R in EGFR-dependent epithelial cell proliferation. P2Y(1)R could potentially mediate both trophic stimuli of basally released nucleotides and first-line mitogenic stimulation upon tissue damage. It could also contribute to carcinogenesis and serve as target for antitumor therapies.
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Affiliation(s)
- Sonja Buvinic
- Centro de Regulación Celular y Patología JV Luco, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 8330033, Santiago, Chile
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22
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Wildman SS, King BF. P2X Receptors: Epithelial Ion Channels and Regulators of Salt and Water Transport. ACTA ACUST UNITED AC 2008; 108:p60-7. [DOI: 10.1159/000122028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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23
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Akiba Y, Mizumori M, Guth PH, Engel E, Kaunitz JD. Duodenal brush border intestinal alkaline phosphatase activity affects bicarbonate secretion in rats. Am J Physiol Gastrointest Liver Physiol 2007; 293:G1223-33. [PMID: 17916646 DOI: 10.1152/ajpgi.00313.2007] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We hypothesized that duodenal HCO(3)(-) secretion alkalinizes the microclimate surrounding intestinal alkaline phosphatase (IAP), increasing its activity. We measured AP activity in rat duodenum in situ in frozen sections with the fluorogenic substrate ELF-97 phosphate and measured duodenal HCO(3)(-) secretion with a pH-stat in perfused duodenal loops. We examined the effects of the IAP inhibitors L-cysteine or L-phenylalanine (0.1-10 mM) or the tissue nonspecific AP inhibitor levamisole (0.1-10 mM) on AP activity in vitro and on acid-induced duodenal HCO(3)(-) secretion in vivo. AP activity was the highest in the duodenal brush border, decreasing longitudinally to the large intestine with no activity in stomach. Villous surface AP activity measured in vivo was enhanced by PGE(2) intravenously and inhibited by luminal L-cysteine. Furthermore, incubation with a pH 2.2 solution reduced AP activity in vivo, whereas pretreatment with the cystic fibrosis transmembrane regulator (CFTR) inhibitor CFTR(inh)-172 abolished AP activity at pH 2.2. L-Cysteine and L-phenylalanine enhanced acid-augmented duodenal HCO(3)(-) secretion. The nonselective P2 receptor antagonist suramin (1 mM) reduced acid-induced HCO(3)(-) secretion. Moreover, L-cysteine or the competitive AP inhibitor glycerol phosphate (10 mM) increased HCO(3)(-) secretion, inhibited by suramin. In conclusion, enhancement of the duodenal HCO(3)(-) secretory rate increased AP activity, whereas inhibition of AP activity increased the HCO(3)(-) secretory rate. These data support our hypothesis that HCO(3)(-) secretion increases AP activity by increasing local pH at its catalytic site and that AP hydrolyzes endogenous luminal phosphates, presumably ATP, which increases HCO(3)(-) secretion via activation of P2 receptors.
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Affiliation(s)
- Yasutada Akiba
- Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, CA, USA
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24
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Woo J, Chae YK, Jang SJ, Kim MS, Baek JH, Park JC, Trink B, Ratovitski E, Lee T, Park B, Park M, Kang JH, Soria JC, Lee J, Califano J, Sidransky D, Moon C. Membrane trafficking of AQP5 and cAMP dependent phosphorylation in bronchial epithelium. Biochem Biophys Res Commun 2007; 366:321-7. [PMID: 18042467 DOI: 10.1016/j.bbrc.2007.11.078] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Accepted: 11/14/2007] [Indexed: 12/20/2022]
Abstract
Phosphorylation pathway has been identified as an important step in membrane trafficking for AQP5. We generated stably transfected BEAS-2B human bronchial epithelial cells with various over-expression constructs on permeable support. In stable cells with wild-type AQP5 and S156A (AQP5 mutant targeting PKA consensus sequence), AQP5 expression was predominantly polarized to the apical membrane, whereas stable cells with N185D (AQP5 mutant targeting second NPA motif), mainly localized to the cytoplasm. Treatment with H89 and/or chlorophenylthio-cAMP (cpt-cAMP) did not affect membrane expression of AQP5 in any of three stable cells. In cells with wild-type AQP5 and N185D, AQP5s were phosphorylated by PKA, while phosphorylation of AQP5 was not detected in cells with S156A. These results indicate that, in AQP5, serine156 may be phosphorylated by PKA, but membrane expression of AQP5 may not be regulated by PKA phosphorylation. We conclude that AQP5 membrane targeting can include more than one mechanism besides cAMP dependent phosphorylation.
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Affiliation(s)
- Janghee Woo
- Department of Otolaryngology, Johns Hopkins University, 1550 Orleans St. 574A, Baltimore, MD 21231, USA
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25
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Purinergic inhibition of Na⁺,K⁺,Cl⁻ cotransport in C11-MDCK cells: Role of stress-activated protein kinases. Purinergic Signal 2007; 4:183-91. [PMID: 18368525 PMCID: PMC2377324 DOI: 10.1007/s11302-007-9057-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 05/08/2007] [Indexed: 12/01/2022] Open
Abstract
Previously, we observed that sustained activation of P2Y1 leads to inhibition of Na+,K+,Cl− cotransport (NKCC) in C11 cells resembling intercalated cells from collecting ducts of the Madin-Darby canine kidney. This study examined the role of stress-activated protein kinases (SAPK) in NKCC inhibition triggered by purinergic receptors. Treatment of C11 cells with ATP led to sustained phosphorylation of SAPK such as JNK and p38. Activation of these kinases also occurred in anisomycin-treated cells. Surprisingly, we observed that compounds SP600125 and SB202190, known as potent inhibitors of JNK and p38 in cell-free systems, activated rather than inhibited phosphorylation of the kinases in C11 cells. Importantly, similarly to ATP, all the above-listed activators of JNK and p38 phosphorylation inhibited NKCC. Thus, our results suggest that activation of JNK and/or p38 contributes to NKCC suppression detected in intercalated-like cells from distal tubules after their exposure to P2Y1 agonists.
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Gruber HE, Ingram J, Hoelscher GL, Norton HJ, Hanley EN. Cell polarity in the anulus of the human intervertebral disc: morphologic, immunocytochemical, and molecular evidence. Spine (Phila Pa 1976) 2007; 32:1287-94. [PMID: 17515816 DOI: 10.1097/brs.0b013e31805931d8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Human intervertebral disc tissue was obtained in a prospective study of cell morphology and gene expression. Experimental studies were approved by the authors' Human Subjects Institutional Review Board. Discs were obtained from surgical specimens or control donors. OBJECTIVES To determine if there is morphologic and molecular evidence for polarity in cells of the human anulus. SUMMARY OF BACKGROUND DATA In many tissues, cells become polarized as they develop functional specializations, which involve cell-cell and cell-extracellular matrix interactions and polarized targeting mechanisms. The highly specialized lamellar organization of the anulus is well recognized and suggests that this structure may be the result of directed secretion of extracellular matrix components by polarized disc cells. METHODS Human disc specimens from donor and surgical patients were examined with light and electron microscopy to assess morphology. Specimens were examined for immunocytochemical localization of PAR3 and claudin-1 and -11, recognized polarity proteins, and additional anulus specimens were examined for expression of polarity-related genes using microarray analysis. In vitro monolayer and 3-dimensional anulus cultures were also studied for gene expression, and additional surgical anulus specimens were used to obtain gene expression data using real time RT-PCR. RESULTS At the ultrastructural level, anulus cells showed localization of secretory organelles and directed deposition of extracellular matrix in one portion of the cell, with the nucleus positioned in the opposite side of the cell. Expression of the polarity-related genes claudin-11 and PAR3 and PARD6 was confirmed using RT-PCR and microarray studies and immunocytochemical analyses. The percentage of cells positive for PAR3 immunolocalization was significantly greater in the outer anulus (100%) than in either the inner anulus (43.8%) or nucleus pulposus (22.6%). CONCLUSIONS At the macroscopic level, the characteristic anular lamellar morphology implies a specialized architectural formation and organization, which is achieved by the tissue-specific function of polarized cells. Morphologic and molecular studies provided evidence for the presence of polarity in cells in the anulus. These findings advance our understanding of anulus disc cell function in production of highly aligned collagen fibrils and macroaggregates of these collagen fibrils into lamellar collagen bundles. Such disc cell activity is important in development and maintenance of the tissue-specific extracellular matrix of the disc.
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Affiliation(s)
- Helen E Gruber
- Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, NC 28232, USA.
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Transient Activation and Delayed Inhibition of Na+,K+,Cl– Cotransport in ATP-treated C11-MDCK Cells Involve Distinct P2Y Receptor Subtypes and Signaling Mechanisms. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84044-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Akimova OA, Grygorczyk A, Bundey RA, Bourcier N, Gekle M, Insel PA, Orlov SN. Transient activation and delayed inhibition of Na+,K+,Cl- cotransport in ATP-treated C11-MDCK cells involve distinct P2Y receptor subtypes and signaling mechanisms. J Biol Chem 2006; 281:31317-25. [PMID: 16916802 DOI: 10.1074/jbc.m602117200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In C11-MDCK cells, which resemble intercalated cells from collecting ducts of the canine kidney, P2Y agonists promote transient activation of the Na+,K+,Cl- cotransporter (NKCC), followed by its sustained inhibition. We designed this study to identify P2Y receptor subtypes involved in dual regulation of this carrier. Real time polymerase chain reaction analysis demonstrated that C11-MDCK cells express abundant P2Y1 and P2Y2 mRNA compared with that of other P2Y receptor subtypes. The rank order of potency of agents (ATP approximately UTP >> 2-(methylthio)-ATP (2MeSATP); adenosine 5'-[beta-thio]diphosphate (ADPbetaS) inactive) indicated that P2Y2 rather than P2Y1 receptors mediate a 3-4-fold activation of NKCC within the first 5-10 min of nucleotide addition. NKCC activation in ATP-treated cells was abolished by the intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, calmodulin (CaM) antagonists trifluoroperazine and W-7, and KN-62, an inhibitor of Ca2+/CaM-dependent protein kinase II. By contrast with the transient activation, 30-min incubation with nucleotides produced up to 4-5-fold inhibition of NKCC, and this inhibition exhibited a rank order of potency (2MeSATP > ADPbetaS > ATP >> UTP) typical of P2Y1 receptors. Unlike the early response, delayed inhibition of NKCC occurred in 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-loaded cells and was completely abolished by the P2Y1 antagonists MRS2179 and MRS2500. Transient activation and delayed inhibition of NKCC in C11 cell monolayers were observed after the addition of ATP to mucosal and serosal solutions, respectively. NKCC inhibition triggered by basolateral application of ADPbetaS was abolished by MRS2500. Our results thus show that transient activation and delayed inhibition of NKCC in ATP-treated C11-MDCK cells is mediated by Ca2+/CaM-dependent protein kinase II- and Ca2+-independent signaling triggered by apical P2Y2 and basolateral P2Y1 receptors, respectively.
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Affiliation(s)
- Olga A Akimova
- Centre de Recherche, Centre Hospitalier de l'Université de Montréal-Technopôle Angus, Montreal, Quebec H1W 4A4, Canada
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Chambers LA, Constable M, Clunes MT, Olver RE, Ko WH, Inglis SK, Wilson SM. Adenosine-evoked Na+ transport in human airway epithelial cells. Br J Pharmacol 2006; 149:43-55. [PMID: 16880767 PMCID: PMC1629408 DOI: 10.1038/sj.bjp.0706822] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Absorptive epithelia express apical receptors that allow nucleotides to inhibit Na(+) transport but ATP unexpectedly stimulated this process in an absorptive cell line derived from human bronchiolar epithelium (H441 cells) whilst UTP consistently caused inhibition. We have therefore examined the pharmacological basis of this anomalous effect of ATP. EXPERIMENTAL APPROACH H441 cells were grown on membranes and the short circuit current (I(SC)) measured in Ussing chambers. In some experiments, [Ca(2+)](i) was measured fluorimetrically using Fura -2. mRNAs for adenosine receptors were determined by the polymerase chain reaction (PCR). KEY RESULTS Cross desensitization experiments showed that the inhibitory response to UTP was abolished by prior exposure to ATP whilst the stimulatory response to ATP persisted in UTP-pre-stimulated cells. Apical adenosine evoked an increase in I(SC) and this response resembled the stimulatory component of the response to ATP, and could be mimicked by adenosine receptor agonists. Pre-stimulation with adenosine abolished the stimulatory component of the response to ATP. mRNA encoding A(1), A(2A) and A(2B) receptor subtypes, but not the A(3) subtype, was detected in H441 cells and adenosine receptor antagonists could abolish the ATP-evoked stimulation of Na(+) absorption. CONCLUSIONS AND IMPLICATIONS The ATP-induced stimulation of Na(+) absorption seems to be mediated via A(2A/B) receptors activated by adenosine produced from the extracellular hydrolysis of ATP. The present data thus provide the first description of adenosine-evoked Na(+) transport in airway epithelial cells and reveal a previously undocumented aspect of the control of this physiologically important ion transport process.
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Affiliation(s)
- L A Chambers
- Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - M Constable
- Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - M T Clunes
- Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - R E Olver
- Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - W H Ko
- Department of Physiology, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China
| | - S K Inglis
- Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - S M Wilson
- Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
- Author for correspondence:
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Ahmad S, Ahmad A, White CW. Purinergic signaling and kinase activation for survival in pulmonary oxidative stress and disease. Free Radic Biol Med 2006; 41:29-40. [PMID: 16781450 DOI: 10.1016/j.freeradbiomed.2006.03.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 02/27/2006] [Accepted: 03/02/2006] [Indexed: 10/24/2022]
Abstract
Stimulus-induced release of endogenous ATP into the extracellular milieu has been shown to occur in a variety of cells, tissues, and organs. Extracellular ATP can propagate signals via P2 receptors that are essential for growth and survival of cells. Abundance of P2 receptors, their multiple isoforms, and their ubiquitous distribution indicate that they transmit vital signals. Pulmonary epithelium and endothelium are rich in both P2X and P2Y receptors. ATP release from lung tissue and cells occurs upon stimulation both in vivo and in vitro. Extracellular ATP can activate signaling cascades composed of protein kinases including extracellular signal-regulated kinase (ERK) and phosphatidylinositol-3-kinase (PI3K). Here we summarize progress related to release of endogenous ATP and nucleotide signaling in pulmonary tissues upon exposure to oxidant stress. Hypoxic, hyperoxic, and ozone exposures cause a rapid increase of extracellular ATP in primary pulmonary endothelial and epithelial cells. Extracellular ATP is critical for survival of these cells in high oxygen and ozone concentrations. The released ATP, upon binding to its specific receptors, triggers ERK and PI3K signaling and renders cells resistant to these stresses. Impairment of ATP release and transmission of such signals could limit cellular survival under oxidative stress. This may further contribute to disease pathogenesis or exacerbation.
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Affiliation(s)
- Shama Ahmad
- Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
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Salo AM, Wang C, Sipilä L, Sormunen R, Vapola M, Kervinen P, Ruotsalainen H, Heikkinen J, Myllylä R. Lysyl hydroxylase 3 (LH3) modifies proteins in the extracellular space, a novel mechanism for matrix remodeling. J Cell Physiol 2006; 207:644-53. [PMID: 16447251 DOI: 10.1002/jcp.20596] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lysyl hydroxylase 3 (LH3), the multifunctional enzyme associated with collagen biosynthesis that possesses lysyl hydroxylase and collagen glycosyltransferase activities, has been characterized in the extracellular space in this study. Lysine modifications are known to occur in the endoplasmic reticulum (ER) prior to collagen triple-helix formation, but in this study we show that LH3 is also present and active in the extracellular space. Studies with in vitro cultured cells indicate that LH3, in addition to being an ER resident, is secreted from the cells and is found both in the medium and on the cell surface associated with collagens or other proteins with collagenous sequences. Furthermore, in vivo, LH3 is present in serum. LH3 protein levels correlate with the galactosylhydroxylysine glucosyltransferase (GGT) activity of mouse tissues. This, together with other data, indicates that LH3 is responsible for GGT activity in the tissues and that GGT activity assays can be used to quantify LH3 in tissues. LH3 in vivo is located in two compartments, in the ER and in the extracellular space, and the partitioning varies with tissue type. In mouse kidney the enzyme is located mainly intracellularly, whereas in mouse liver it is located solely in the extracellular space. The extracellular localization and the ability of LH3 to modify lysyl residues of extracellular proteins in their native, nondenaturated conformation reveals a new dynamic in extracellular matrix remodeling, suggesting a novel mechanism for adjusting the amount of hydroxylysine and hydroxylysine-linked carbohydrates in collagenous proteins.
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Affiliation(s)
- Antti M Salo
- Department of Biochemistry and Biocenter Oulu, University of Oulu, Oulu, Finland
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Carvou N, Norden AGW, Unwin RJ, Cockcroft S. Signalling through phospholipase C interferes with clathrin-mediated endocytosis. Cell Signal 2006; 19:42-51. [PMID: 16843639 DOI: 10.1016/j.cellsig.2006.05.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 05/23/2006] [Accepted: 05/24/2006] [Indexed: 11/23/2022]
Abstract
We investigated if phosphatidylinositol(4,5)bisphosphate (PtdIns(4,5)P2) hydrolysis by phospholipase C activation through cell surface receptors would interfere with clathrin-mediated endocytosis as recruitment of clathrin assembly proteins is PtdIns(4,5)P2-dependent. In the WKPT renal epithelial cell line, endocytosed insulin and beta2-glycoprotein I (beta2gpI) were observed in separate compartments, although endocytosis of both ligands was clathrin-dependent as demonstrated by expression of the clathrin-binding C-terminal domain of AP180 (AP180-C). The two uptake mechanisms were different as only insulin uptake was reduced when the mu2-subunit of the adaptor complex AP-2 was silenced by RNA interference. ATP receptors are expressed at the apical surface of renal cells and, thus, we examined the effect of extracellular ATP on insulin and beta2gpI uptake. ATP stimulated phospholipase C activity, and also suppressed uptake of insulin, but not beta2gpI. This effect was reversed by the PLC inhibitor U-73122. In polarized cell cultures, insulin uptake was apical, whereas beta2gpI uptake was through the basolateral membrane, thus providing an explanation for selective inhibition of insulin endocytosis by ATP. Taken together, these results demonstrate that stimulation of apical G-protein-coupled P2Y receptors, which are coupled to phospholipase C activation diminishes clathrin-mediated endocytosis without interfering with basolateral endocytic mechanisms.
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Affiliation(s)
- Nicolas Carvou
- Department of Physiology, University College London, London WC1E 6JJ UK
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Vial C, Fung CYE, Goodall AH, Mahaut-Smith MP, Evans RJ. Differential sensitivity of human platelet P2X1 and P2Y1 receptors to disruption of lipid rafts. Biochem Biophys Res Commun 2006; 343:415-9. [PMID: 16546137 DOI: 10.1016/j.bbrc.2006.02.174] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Accepted: 02/27/2006] [Indexed: 11/20/2022]
Abstract
ATP-stimulated P2X1 and ADP-stimulated P2Y1 receptors play important roles in platelet activation. An increase in intracellular Ca2+ represents a key signalling event coupled to both of these receptors, mediated via direct gating of Ca2+-permeable channels in the case of P2X1 and phospholipase-C-dependent Ca2+ mobilisation for P2Y1. We show that disruption of cholesterol-rich membrane lipid rafts reduces P2X1 receptor-mediated calcium increases by approximately 80%, while P2Y1 receptor-dependent Ca2+ release is unaffected. In contrast to artery, vas deferens, bladder smooth muscle, and recombinant expression in cell lines, where P2X1 receptors show almost exclusive association with lipid rafts, only approximately 20% of platelet P2X1 receptors are co-expressed with the lipid raft marker flotillin-2. We conclude that lipid rafts play a significant role in the regulation of P2X1 but not P2Y1 receptors in human platelets and that a reserve of non-functional P2X1 receptors may exist.
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Affiliation(s)
- Catherine Vial
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester LE1 9HN, UK
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Ghanem E, Robaye B, Leal T, Leipziger J, Driessche WV, Beauwens R, Boeynaems JM. The role of epithelial P2Y2 and P2Y4 receptors in the regulation of intestinal chloride secretion. Br J Pharmacol 2006; 146:364-9. [PMID: 16056234 PMCID: PMC1576293 DOI: 10.1038/sj.bjp.0706353] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
UTP-induced chloride secretion by the intestinal mucosa mounted in Ussing chambers was assessed by measurement of the short-circuit current (I(sc)) in the presence of phloridzin in the case of jejunum or amiloride in the case of colon to eliminate any contribution of electrogenic Na(+) movement to the net ionic transport. Since we have previously demonstrated the absence of chloride-secretory response to apical UTP in the jejunum from P2Y(4)-null mice, in the present study we studied the response to basolateral UTP in the jejunum and to either apical or basolateral UTP in the colon, in both P2Y(2)- and P2Y(4)-deficient mice. In the jejunum, the chloride-secretory response to basolateral UTP was partially reduced in both P2Y(2)- (40%) and P2Y(4)- (60%) null mice. In the colon, both apical or basolateral UTP increased the I(sc). That response was abolished in a chloride-free medium. The colonic chloride-secretory response to either basolateral or apical UTP was abolished in P2Y(4)-deficient mice, but not significantly affected in P2Y(2)-deficient mice. The chloride-secretory response to forskolin was potentiated by prior basolateral addition of UTP and this potentiation was abolished in P2Y(4)-null mice. The jejunum of mice homozygous for the DeltaF508 mutation of cystic fibrosis transmembrane conductance regulator was responsive to UTP, but the magnitude of that response was smaller than in the wild-type littermates. In conclusion, the P2Y(4) receptor fully mediates the chloride-secretory response to UTP in both small and large intestines, except at the basolateral side of the jejunum, where both P2Y(2) and P2Y(4) receptors are involved.
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Affiliation(s)
- Esam Ghanem
- Laboratory of Cell and Molecular Physiology, School of Medicine, Université Libre de Bruxelles, Brussels, Belgium
| | - Bernard Robaye
- Institute of Interdisciplinary Research, Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, Gosselies, Belgium
| | - Teresinha Leal
- Department of Clinical Chemistry, Saint Luc Hospital, Université Catholique de Louvain, Brussels, Belgium
| | - Jens Leipziger
- Institute of Physiology, The Water and Salt Research Center, University of Aarhus, Aarhus, Denmark
| | | | - Renaud Beauwens
- Laboratory of Cell and Molecular Physiology, School of Medicine, Université Libre de Bruxelles, Brussels, Belgium
| | - Jean-Marie Boeynaems
- Institute of Interdisciplinary Research, Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, Gosselies, Belgium
- Laboratory of Medical Chemistry, Erasme Hospital, Brussels, Belgium
- Author for correspondence:
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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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Qi AD, Wolff SC, Nicholas RA. The apical targeting signal of the P2Y2 receptor is located in its first extracellular loop. J Biol Chem 2005; 280:29169-75. [PMID: 15908695 DOI: 10.1074/jbc.m501301200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P2Y2 and P2Y4 receptors, which have 52% sequence identity, are both expressed at the apical membrane of Madin-Darby canine kidney cells, but the locations of their apical targeting signals are distinctly different. The targeting signal of the P2Y2 receptor is located between the N terminus and 7TM, whereas that of the P2Y4 receptor is present in its C-terminal tail. To identify the apical targeting signal in the P2Y2 receptor, regions of the P2Y2 receptor were progressively substituted with the corresponding regions of the P2Y4 receptor lacking its targeting signal. Characterization of these chimeras and subsequent mutational analysis revealed that four amino acids (Arg95, Gly96, Asp97, and Leu108) in the first extracellular loop play a major role in apical targeting of the P2Y2 receptor. Mutation of RGD to RGE had no effect on P2Y2 receptor targeting, indicating that receptor-integrin interactions are not involved in apical targeting. P2Y2 receptor mutants were localized in a similar manner in Caco-2 colon epithelial cells. This is the first identification of an extracellular protein-based targeting signal in a seven-transmembrane receptor.
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Affiliation(s)
- Ai-Dong Qi
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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