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Abstract
In the last 15 years, tremendous progress has been made in the development of single-cell cAMP sensors. Sensors are based upon cAMP-binding proteins that have been modified to transduce cAMP concentrations into electrical or fluorescent readouts that can be readily detected using patch clamp amplifiers, photomultiplier tubes, or cameras. Here we describe two complementary approaches for the detection and measurement of cAMP signals near the plasma membrane of cells. These probes take advantage of the ability of cyclic nucleotide-gated (CNG) channels to transduce small changes in cAMP concentrations into ionic flux through channel pores that can be readily detected by measuring Ca(2+) and/or Mn(2+) influx or by measuring ionic currents.
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Neves-Zaph SR, Song RS. Development of computational models of cAMP signaling. Methods Mol Biol 2015; 1294:203-17. [PMID: 25783888 DOI: 10.1007/978-1-4939-2537-7_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Despite the growing evidence defining the cAMP signaling network as a master regulator of cellular function in a number of tissues, regulatory feedback loops, signal compartmentalization, as well as cross-talk with other signaling pathways make understanding the emergent properties of cAMP cellular action a daunting task. Dynamical models of signaling that combine quantitative rigor with molecular details can contribute valuable mechanistic insight into the complexity of intracellular cAMP signaling by complementing and guiding experimental efforts. In this chapter, we review the development of cAMP computational models. We describe how features of the cAMP network can be represented and review the types of experimental data useful in modeling cAMP signaling. We also compile a list of published cAMP models that can aid in the development of novel dynamical models of cAMP signaling.
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Affiliation(s)
- Susana R Neves-Zaph
- Department of Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA,
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53
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Morrow KA, Seifert R, Kaever V, Britain AL, Sayner SL, Ochoa CD, Cioffi EA, Frank DW, Rich TC, Stevens T. Heterogeneity of pulmonary endothelial cyclic nucleotide response to Pseudomonas aeruginosa ExoY infection. Am J Physiol Lung Cell Mol Physiol 2015; 309:L1199-207. [PMID: 26386118 PMCID: PMC4652153 DOI: 10.1152/ajplung.00165.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/11/2015] [Indexed: 01/16/2023] Open
Abstract
Here, we tested the hypothesis that a promiscuous bacterial cyclase synthesizes purine and pyrimidine cyclic nucleotides in the pulmonary endothelium. To test this hypothesis, pulmonary endothelial cells were infected with a strain of the Gram-negative bacterium Pseudomonas aeruginosa that introduces only exoenzyme Y (PA103 ΔexoUexoT::Tc pUCPexoY; ExoY(+)) via a type III secretion system. Purine and pyrimidine cyclic nucleotides were simultaneously detected using mass spectrometry. Pulmonary artery (PAECs) and pulmonary microvascular (PMVECs) endothelial cells both possess basal levels of four different cyclic nucleotides in the following rank order: cAMP > cUMP ≈ cGMP ≈ cCMP. Endothelial gap formation was induced in a time-dependent manner following ExoY(+) intoxication. In PAECs, intercellular gaps formed within 2 h and progressively increased in size up to 6 h, when the experiment was terminated. cGMP concentrations increased within 1 h postinfection, whereas cAMP and cUMP concentrations increased within 3 h, and cCMP concentrations increased within 4 h postinfection. In PMVECs, intercellular gaps did not form until 4 h postinfection. Only cGMP and cUMP concentrations increased at 3 and 6 h postinfection, respectively. PAECs generated higher cyclic nucleotide levels than PMVECs, and the cyclic nucleotide levels increased earlier in response to ExoY(+) intoxication. Heterogeneity of the cyclic nucleotide signature in response to P. aeruginosa infection exists between PAECs and PMVECs, suggesting the intracellular milieu in PAECs is more conducive to cNMP generation.
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Affiliation(s)
- K A Morrow
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - R Seifert
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany
| | - V Kaever
- Research Core Unit Metabolomics, Hannover Medical School, Hannover, Germany
| | - A L Britain
- Department of Pharmacology, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - S L Sayner
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - C D Ochoa
- Physician-Scientist Training Program, Department of Medicine, University of Texas-Southwestern Medical Center, Dallas, Texas; Physician-Scientist Training Program, Division of Pulmonary and Critical Care, University of Texas-Southwestern Medical Center, Dallas, Texas
| | - E A Cioffi
- Department of Pharmacology, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - D W Frank
- Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin; and Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - T C Rich
- Department of Pharmacology, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - T Stevens
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama; Department of Medicine, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama;
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Felouzis V, Hermand P, de Laissardière GT, Combadière C, Deterre P. Comprehensive analysis of chemokine-induced cAMP-inhibitory responses using a real-time luminescent biosensor. Cell Signal 2015; 28:120-9. [PMID: 26515128 DOI: 10.1016/j.cellsig.2015.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 10/23/2015] [Indexed: 01/29/2023]
Abstract
Chemokine receptors are members of the G-protein-coupled receptor (GPCR) family coupled to members of the Gi class, whose primary function is to inhibit the cellular adenylate cyclase. We used a cAMP-related and PKA-based luminescent biosensor (GloSensor™ F-22) to monitor the real-time downstream response of chemokine receptors, especially CX3CR1 and CXCR4, after activation with their cognate ligands CX3CL1 and CXCL12. We found that the amplitudes and kinetic profiles of the chemokine responses were conserved in various cell types and were independent of the nature and concentration of the molecules used for cAMP prestimulation, including either the adenylate cyclase activator forskolin or ligands mediating Gs-mediated responses like prostaglandin E2 or beta-adrenergic agonist. We conclude that the cAMP chemokine response is robustly conserved in various inflammatory conditions. Moreover, the cAMP-related luminescent biosensor appears as a valuable tool to analyze the details of Gi-mediated cAMP-inhibitory cellular responses, even in native conditions and could help to decipher their precise role in cell function.
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Affiliation(s)
- Virginia Felouzis
- Sorbonne Universités, UPMC Université Paris 06, Inserm U 1135, CNRS ERL 8255, Centre d'Immunologie et des Maladies Infectieuses, 91 Boulevard de l'Hôpital, F-75013 Paris, France
| | - Patricia Hermand
- Sorbonne Universités, UPMC Université Paris 06, Inserm U 1135, CNRS ERL 8255, Centre d'Immunologie et des Maladies Infectieuses, 91 Boulevard de l'Hôpital, F-75013 Paris, France
| | - Guy Trambly de Laissardière
- Université de Cergy-Pontoise, CNRS, UMR 8089, Laboratoire de Physique Théorique et Modélisation, 2 Avenue A. Chauvin, F-95302 Cergy-Pontoise, France
| | - Christophe Combadière
- Sorbonne Universités, UPMC Université Paris 06, Inserm U 1135, CNRS ERL 8255, Centre d'Immunologie et des Maladies Infectieuses, 91 Boulevard de l'Hôpital, F-75013 Paris, France
| | - Philippe Deterre
- Sorbonne Universités, UPMC Université Paris 06, Inserm U 1135, CNRS ERL 8255, Centre d'Immunologie et des Maladies Infectieuses, 91 Boulevard de l'Hôpital, F-75013 Paris, France.
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55
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Bentin Toaldo C, Alexi X, Beelen K, Kok M, Hauptmann M, Jansen M, Berns E, Neefjes J, Linn S, Michalides R, Zwart W. Protein Kinase A-induced tamoxifen resistance is mediated by anchoring protein AKAP13. BMC Cancer 2015; 15:588. [PMID: 26272591 PMCID: PMC4536754 DOI: 10.1186/s12885-015-1591-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 08/03/2015] [Indexed: 11/16/2022] Open
Abstract
Background Estrogen Receptor alpha (ERα)-positive breast cancer patients receive endocrine therapy, often in the form of tamoxifen. However, resistance to tamoxifen is frequently observed. A signalling cascade that leads to tamoxifen resistance is dictated by activation of the Protein Kinase A (PKA) pathway, which leads to phosphorylation of ERα on Serine 305 and receptor activation, following tamoxifen binding. Thus far, it remains elusive what protein complexes enable the PKA-ERα interaction resulting in ERα Serine 305 phosphorylation. Methods We performed immunohistochemistry to detect ERαSerine 305 phosphorylation in a cohort of breast cancer patients who received tamoxifen treatment in the metastatic setting. From the same tumor specimens, Agilent 44 K gene expression analyses were performed and integrated with clinicopathological data and survival information. In vitro analyses were performed using MCF7 breast cancer cells, which included immunoprecipitations and Fluorescence Resonance Energy Transfer (FRET) analyses to illustrate ERα complex formation. siRNA mediated knockdown experiments were performed to assess effects on ERαSerine 305 phosphorylation status, ERα/PKA interactions and downstream responsive gene activity. Results Stratifying breast tumors on ERα Serine 305 phosphorylation status resulted in the identification of a gene network centered upon AKAP13. AKAP13 mRNA expression levels correlate with poor outcome in patients who received tamoxifen treatment in the metastatic setting. In addition, AKAP13 mRNA levels correlate with ERαSerine 305 phosphorylation in breast tumor samples, suggesting a functional connection between these two events. In a luminal breast cancer cell line, AKAP13 was found to interact with ERα as well as with a regulatory subunit of PKA. Knocking down of AKAP13 prevented PKA-mediated Serine 305 phosphorylation of ERα and abrogated PKA-driven tamoxifen resistance, illustrating that AKAP13 is an essential protein in this process. Conclusions We show that the PKA-anchoring protein AKAP13 is essential for the phosphorylation of ERαS305, which leads to tamoxifen resistance both in cell lines and tamoxifen-treated breast cancer patients. Electronic supplementary material The online version of this article (doi:10.1186/s12885-015-1591-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Cristiane Bentin Toaldo
- Division of Molecular Pathology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Xanthippi Alexi
- Division of Molecular Pathology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Karin Beelen
- Division of Molecular Pathology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Marleen Kok
- Division of Molecular Pathology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Michael Hauptmann
- Division of Psychosocial Research and Epidemiology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Maurice Jansen
- Department of Medical Oncology, Josephine Nefkens Institute and Cancer Genomics Center, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands.
| | - Els Berns
- Department of Medical Oncology, Josephine Nefkens Institute and Cancer Genomics Center, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands.
| | - Jacques Neefjes
- Division of Cell Biology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Sabine Linn
- Division of Molecular Pathology, the Netherlands Cancer Institute, Amsterdam, The Netherlands. .,Department of Medical Oncology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Rob Michalides
- Division of Cell Biology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Wilbert Zwart
- Division of Molecular Pathology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.
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56
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Xin W, Feinstein WP, Britain AL, Ochoa CD, Zhu B, Richter W, Leavesley SJ, Rich TC. Estimating the magnitude of near-membrane PDE4 activity in living cells. Am J Physiol Cell Physiol 2015. [PMID: 26201952 DOI: 10.1152/ajpcell.00090.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Recent studies have demonstrated that functionally discrete pools of phosphodiesterase (PDE) activity regulate distinct cellular functions. While the importance of localized pools of enzyme activity has become apparent, few studies have estimated enzyme activity within discrete subcellular compartments. Here we present an approach to estimate near-membrane PDE activity. First, total PDE activity is measured using traditional PDE activity assays. Second, known cAMP concentrations are dialyzed into single cells and the spatial spread of cAMP is monitored using cyclic nucleotide-gated channels. Third, mathematical models are used to estimate the spatial distribution of PDE activity within cells. Using this three-tiered approach, we observed two pharmacologically distinct pools of PDE activity, a rolipram-sensitive pool and an 8-methoxymethyl IBMX (8MM-IBMX)-sensitive pool. We observed that the rolipram-sensitive PDE (PDE4) was primarily responsible for cAMP hydrolysis near the plasma membrane. Finally, we observed that PDE4 was capable of blunting cAMP levels near the plasma membrane even when 100 μM cAMP were introduced into the cell via a patch pipette. Two compartment models predict that PDE activity near the plasma membrane, near cyclic nucleotide-gated channels, was significantly lower than total cellular PDE activity and that a slow spatial spread of cAMP allowed PDE activity to effectively hydrolyze near-membrane cAMP. These results imply that cAMP levels near the plasma membrane are distinct from those in other subcellular compartments; PDE activity is not uniform within cells; and localized pools of AC and PDE activities are responsible for controlling cAMP levels within distinct subcellular compartments.
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Affiliation(s)
- Wenkuan Xin
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
| | - Wei P Feinstein
- High Performance Computing, Louisiana State University, Baton Rouge, Louisiana
| | - Andrea L Britain
- Department of Pharmacology, University of South Alabama, Mobile, Alabama; and Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - Cristhiaan D Ochoa
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Bing Zhu
- Mitchell Cancer Institute, Mobile, Alabama
| | - Wito Richter
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama; Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - Silas J Leavesley
- Department of Chemical and Biomolecular Engineering, University of South Alabama, Mobile, Alabama; Department of Pharmacology, University of South Alabama, Mobile, Alabama; and Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - Thomas C Rich
- Department of Pharmacology, University of South Alabama, Mobile, Alabama; and Center for Lung Biology, University of South Alabama, Mobile, Alabama
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Kang JH, Lee HS, Kang YW, Cho KH. Systems biological approaches to the cardiac signaling network. Brief Bioinform 2015; 17:419-28. [DOI: 10.1093/bib/bbv039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Indexed: 01/08/2023] Open
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58
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Krishnamurthy S, Moorthy BS, Xin Xiang L, Xin Shan L, Bharatham K, Tulsian NK, Mihalek I, Anand GS. Active site coupling in PDE:PKA complexes promotes resetting of mammalian cAMP signaling. Biophys J 2015; 107:1426-40. [PMID: 25229150 DOI: 10.1016/j.bpj.2014.07.050] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 07/03/2014] [Accepted: 07/15/2014] [Indexed: 11/25/2022] Open
Abstract
Cyclic 3'5' adenosine monophosphate (cAMP)-dependent-protein kinase (PKA) signaling is a fundamental regulatory pathway for mediating cellular responses to hormonal stimuli. The pathway is activated by high-affinity association of cAMP with the regulatory subunit of PKA and signal termination is achieved upon cAMP dissociation from PKA. Although steps in the activation phase are well understood, little is known on how signal termination/resetting occurs. Due to the high affinity of cAMP to PKA (KD ∼ low nM), bound cAMP does not readily dissociate from PKA, thus begging the question of how tightly bound cAMP is released from PKA to reset its signaling state to respond to subsequent stimuli. It has been recently shown that phosphodiesterases (PDEs) can catalyze dissociation of bound cAMP and thereby play an active role in cAMP signal desensitization/termination. This is achieved through direct interactions with the regulatory subunit of PKA, thereby facilitating cAMP dissociation and hydrolysis. In this study, we have mapped direct interactions between a specific cyclic nucleotide phosphodiesterase (PDE8A) and a PKA regulatory subunit (RIα isoform) in mammalian cAMP signaling, by a combination of amide hydrogen/deuterium exchange mass spectrometry, peptide array, and computational docking. The interaction interface of the PDE8A:RIα complex, probed by peptide array and hydrogen/deuterium exchange mass spectrometry, brings together regions spanning the phosphodiesterase active site and cAMP-binding sites of RIα. Computational docking combined with amide hydrogen/deuterium exchange mass spectrometry provided a model for parallel dissociation of bound cAMP from the two tandem cAMP-binding domains of RIα. Active site coupling suggests a role for substrate channeling in the PDE-dependent dissociation and hydrolysis of cAMP bound to PKA. This is the first instance, to our knowledge, of PDEs directly interacting with a cAMP-receptor protein in a mammalian system, and highlights an entirely new class of binding partners for RIα. This study also highlights applications of structural mass spectrometry combined with computational docking for mapping dynamics in transient signaling protein complexes. Together, these results present a novel and critical role for phosphodiesterases in moderating local concentrations of cAMP in microdomains and signal resetting.
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Affiliation(s)
- Srinath Krishnamurthy
- Department of Biological Sciences, National University of Singapore, Singapore; Mechanobiology Institute, National University of Singapore, Singapore
| | | | - Lim Xin Xiang
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Lim Xin Shan
- Department of Biological Sciences, National University of Singapore, Singapore
| | | | | | | | - Ganesh S Anand
- Department of Biological Sciences, National University of Singapore, Singapore; Mechanobiology Institute, National University of Singapore, Singapore.
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Monterisi S, Casavola V, Zaccolo M. Local modulation of cystic fibrosis conductance regulator: cytoskeleton and compartmentalized cAMP signalling. Br J Pharmacol 2014; 169:1-9. [PMID: 23072488 DOI: 10.1111/bph.12017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/12/2012] [Accepted: 10/05/2012] [Indexed: 11/28/2022] Open
Abstract
The cystic fibrosis conductance regulator (CFTR) is a cAMP-regulated Cl(-) channel expressed predominantly at the apical membrane of secreting epithelial cells. Mutations in the CFTR gene lead to cystic fibrosis, the most frequent genetic disease in the Caucasian population. The most common mutation, a deletion of phenylalanine at position 508 (F508del), impairs CFTR folding and chloride channel function. Although an intense effort is under way to identify compounds that target the F508del CFTR structural defect and promote its expression and stability at the plasma membrane, so far their clinical efficacy has proven to be poor, highlighting the necessity to better understand the molecular mechanism of CFTR regulation and of the pathogenesis of the disease. Accumulating evidence suggests that the inclusion of the CFTR in macromolecular complexes and its interaction with the cortical cytoskeleton may play a key role in fine-tuning the regulation of channel function. Here we review some recent findings that support a critical role for protein-protein interactions involving CFTR and for the cytoskeleton in promoting local control of channel activity. These findings indicate that compounds that rescue and stabilize CFTR at the apical membrane may not be sufficient to restore its function unless the appropriate intracellular milieu is also reconstituted.
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Affiliation(s)
- Stefania Monterisi
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, UK
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60
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Radeva MY, Kugelmann D, Spindler V, Waschke J. PKA compartmentalization via AKAP220 and AKAP12 contributes to endothelial barrier regulation. PLoS One 2014; 9:e106733. [PMID: 25188285 PMCID: PMC4154725 DOI: 10.1371/journal.pone.0106733] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 08/07/2014] [Indexed: 01/14/2023] Open
Abstract
cAMP-mediated PKA signaling is the main known pathway involved in maintenance of the endothelial barrier. Tight regulation of PKA function can be achieved by discrete compartmentalization of the enzyme via physical interaction with A-kinase anchoring proteins (AKAPs). Here, we investigated the role of AKAPs 220 and 12 in endothelial barrier regulation. Analysis of human and mouse microvascular endothelial cells as well as isolated rat mesenteric microvessels was performed using TAT-Ahx-AKAPis peptide, designed to competitively inhibit PKA-AKAP interaction. In vivo microvessel hydraulic conductivity and in vitro transendothelial electrical resistance measurements showed that this peptide destabilized endothelial barrier properties, and dampened the cAMP-mediated endothelial barrier stabilization induced by forskolin and rolipram. Immunofluorescence analysis revealed that TAT-Ahx-AKAPis led to both adherens junctions and actin cytoskeleton reorganization. Those effects were paralleled by redistribution of PKA and Rac1 from endothelial junctions and by Rac1 inactivation. Similarly, membrane localization of AKAP220 was also reduced. In addition, depletion of either AKAP12 or AKAP220 significantly impaired endothelial barrier function and AKAP12 was also shown to interfere with cAMP-mediated barrier enhancement. Furthermore, immunoprecipitation analysis demonstrated that AKAP220 interacts not only with PKA but also with VE-cadherin and ß-catenin. Taken together, these results indicate that AKAP-mediated PKA subcellular compartmentalization is involved in endothelial barrier regulation. More specifically, AKAP220 and AKAP12 contribute to endothelial barrier function and AKAP12 is required for cAMP-mediated barrier stabilization.
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Affiliation(s)
- Mariya Y. Radeva
- Institute of Anatomy and Cell Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Daniela Kugelmann
- Institute of Anatomy and Cell Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Volker Spindler
- Institute of Anatomy and Cell Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Jens Waschke
- Institute of Anatomy and Cell Biology, Ludwig-Maximilians-University Munich, Munich, Germany
- * E-mail:
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Saucerman JJ, Greenwald EC, Polanowska-Grabowska R. Mechanisms of cyclic AMP compartmentation revealed by computational models. ACTA ACUST UNITED AC 2014; 143:39-48. [PMID: 24378906 PMCID: PMC3874575 DOI: 10.1085/jgp.201311044] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jeffrey J Saucerman
- Department of Biomedical Engineering and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908
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Conti M, Mika D, Richter W. Cyclic AMP compartments and signaling specificity: role of cyclic nucleotide phosphodiesterases. ACTA ACUST UNITED AC 2014; 143:29-38. [PMID: 24378905 PMCID: PMC3874571 DOI: 10.1085/jgp.201311083] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Marco Conti
- Center for Reproductive Sciences, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143
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Karpen JW. Perspectives on: Cyclic nucleotide microdomains and signaling specificity. ACTA ACUST UNITED AC 2014; 143:5-7. [PMID: 24378902 PMCID: PMC3874568 DOI: 10.1085/jgp.201311144] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Jeffrey W Karpen
- Department of Medical Education, California Northstate University College of Medicine, Elk Grove, CA 95757
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Role of soluble adenylyl cyclase in cell death and growth. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2646-55. [PMID: 25010002 DOI: 10.1016/j.bbadis.2014.06.034] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/26/2014] [Accepted: 06/27/2014] [Indexed: 12/13/2022]
Abstract
cAMP signaling is an evolutionarily conserved intracellular communication system controlling numerous cellular functions. Until recently, transmembrane adenylyl cyclase (tmAC) was considered the major source for cAMP in the cell, and the role of cAMP signaling was therefore attributed exclusively to the activity of this family of enzymes. However, increasing evidence demonstrates the role of an alternative, intracellular source of cAMP produced by type 10 soluble adenylyl cyclase (sAC). In contrast to tmAC, sAC produces cAMP in various intracellular microdomains close to specific cAMP targets, e.g., in nucleus and mitochondria. Ongoing research demonstrates involvement of sAC in diverse physiological and pathological processes. The present review is focused on the role of cAMP signaling, particularly that of sAC, in cell death and growth. Although the contributions of sAC to the regulation of these cellular functions have only recently been discovered, current data suggest that sAC plays key roles in mitochondrial bioenergetics and the mitochondrial apoptosis pathway, as well as cell proliferation and development. Furthermore, recent reports suggest the importance of sAC in several pathologies associated with apoptosis as well as in oncogenesis. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.
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Nadim F, Bucher D. Neuromodulation of neurons and synapses. Curr Opin Neurobiol 2014; 29:48-56. [PMID: 24907657 DOI: 10.1016/j.conb.2014.05.003] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/09/2014] [Accepted: 05/09/2014] [Indexed: 12/15/2022]
Abstract
Neuromodulation underlies the flexibility of neural circuit operation and behavior. Individual neuromodulators can have divergent actions in a neuron by targeting multiple physiological mechanisms. Conversely, multiple neuromodulators may have convergent actions through overlapping targets. The divergent and convergent neuromodulator actions can be unambiguously synergistic or antagonistic, but neuromodulation often entails balanced adjustment of nonlinear membrane and synaptic properties by targeting ion channel and synaptic dynamics rather than just excitability or synaptic strength. In addition, neuromodulators can exert effects at multiple timescales, from short-term adjustments of neuron and synapse function to persistent long-term regulation. This short review summarizes some highlights of the diverse actions of neuromodulators on ion channel and synaptic properties.
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Affiliation(s)
- Farzan Nadim
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, 323 Martin Luther King Blvd, Newark, NJ 07102, United States.
| | - Dirk Bucher
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, 323 Martin Luther King Blvd, Newark, NJ 07102, United States
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Modulation of the cAMP response by Gαi and Gβγ: a computational study of G protein signaling in immune cells. Bull Math Biol 2014; 76:1352-75. [PMID: 24809944 DOI: 10.1007/s11538-014-9964-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Accepted: 04/14/2014] [Indexed: 12/15/2022]
Abstract
Cyclic AMP is important for the resolution of inflammation, as it promotes anti-inflammatory signaling in several immune cell lines. In this paper, we present an immune cell specific model of the cAMP signaling cascade, paying close attention to the specific isoforms of adenylyl cyclase (AC) and phosphodiesterase that control cAMP production and degradation, respectively, in these cells. The model describes the role that G protein subunits, including Gαs, Gαi, and Gβγ, have in regulating cAMP production. Previously, Gαi activation has been shown to increase the level of cAMP in certain immune cell types. This increase in cAMP is thought to be mediated by βγ subunits which are released upon Gα activation and can directly stimulate specific isoforms of AC. We conduct numerical experiments in order to explore the mechanisms through which Gαi activation can increase cAMP production. An important conclusion of our analysis is that the relative abundance of different G protein subunits is an essential determinant of the cAMP profile in immune cells. In particular, our model predicts that limited availability of βγ subunits may both (i) enable immune cells to link inflammatory Gαi signaling to anti-inflammatory cAMP production thereby creating a balanced immune response to stimulation with low concentrations of PGE2, and (ii) prohibit robust anti-inflammatory cAMP signaling in response to stimulation with high concentrations of PGE2.
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67
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Agarwal SR, Yang PC, Rice M, Singer CA, Nikolaev VO, Lohse MJ, Clancy CE, Harvey RD. Role of membrane microdomains in compartmentation of cAMP signaling. PLoS One 2014; 9:e95835. [PMID: 24752595 PMCID: PMC3994114 DOI: 10.1371/journal.pone.0095835] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 03/31/2014] [Indexed: 12/03/2022] Open
Abstract
Spatially restricting cAMP production to discrete subcellular locations permits selective regulation of specific functional responses. But exactly where and how cAMP signaling is confined is not fully understood. Different receptors and adenylyl cyclase isoforms responsible for cAMP production are not uniformly distributed between lipid raft and non-lipid raft domains of the plasma membrane. We sought to determine the role that these membrane domains play in organizing cAMP responses in HEK293 cells. The freely diffusible FRET-based biosensor Epac2-camps was used to measure global cAMP responses, while versions of the probe targeted to lipid raft (Epac2-MyrPalm) and non-raft (Epac2-CAAX) domains were used to monitor local cAMP production near the plasma membrane. Disruption of lipid rafts by cholesterol depletion selectively altered cAMP responses produced by raft-associated receptors. The results indicate that receptors associated with lipid raft as well as non-lipid raft domains can contribute to global cAMP responses. In addition, basal cAMP activity was found to be significantly higher in non-raft domains. This was supported by the fact that pharmacologic inhibition of adenylyl cyclase activity reduced basal cAMP activity detected by Epac2-CAAX but not Epac2-MyrPalm or Epac2-camps. Responses detected by Epac2-CAAX were also more sensitive to direct stimulation of adenylyl cyclase activity, but less sensitive to inhibition of phosphodiesterase activity. Quantitative modeling was used to demonstrate that differences in adenylyl cyclase and phosphodiesterase activities are necessary but not sufficient to explain compartmentation of cAMP associated with different microdomains of the plasma membrane.
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Affiliation(s)
- Shailesh R. Agarwal
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, United States of America
| | - Pei-Chi Yang
- Department of Pharmacology, University of California Davis, Davis, California, United States of America
| | - Monica Rice
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, United States of America
| | - Cherie A. Singer
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, United States of America
| | - Viacheslav O. Nikolaev
- European Heart Research Institute Gottingen, University of Göttingen, Göttingen, Germany
| | - Martin J. Lohse
- Department of Pharmacology, University of Würzburg, Würzburg, Germany
| | - Colleen E. Clancy
- Department of Pharmacology, University of California Davis, Davis, California, United States of America
| | - Robert D. Harvey
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, United States of America
- * E-mail:
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68
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Castro LRV, Guiot E, Polito M, Paupardin-Tritsch D, Vincent P. Decoding spatial and temporal features of neuronal cAMP/PKA signaling with FRET biosensors. Biotechnol J 2014; 9:192-202. [PMID: 24478276 DOI: 10.1002/biot.201300202] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 12/02/2013] [Accepted: 01/08/2014] [Indexed: 11/11/2022]
Abstract
Cyclic adenosine monophosphate (cAMP) and the cyclic-AMP-dependent protein kinase (PKA) regulate a plethora of cellular functions in virtually all eukaryotic cells. In neurons, the cAMP/PKA signaling cascade controls a number of biological properties such as axonal growth, pathfinding, efficacy of synaptic transmission, regulation of excitability, or long term changes. Genetically encoded optical biosensors for cAMP or PKA are considerably improving our understanding of these processes by providing a real-time measurement in living neurons. In this review, we describe the recent progress made in the creation of biosensors for cAMP or PKA activity. These biosensors revealed profound differences in the amplitude of the cAMP signal evoked by neuromodulators between various neuronal preparations. These responses can be resolved at the level of individual neurons, also revealing differences related to the neuronal type. At the sub-cellular level, biosensors reported different signal dynamics in domains like dendrites, cell body, nucleus, and axon. Combining this imaging approach with pharmacology or genetic models points at phosphodiesterases and phosphatases as critical regulatory proteins. Biosensor imaging will certainly emerge as a forefront tool to decipher the subtle mechanics of intracellular signaling. This will certainly help us to understand the mechanism of action of current drugs and foster the development of novel molecules for neuropsychiatric diseases.
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Affiliation(s)
- Liliana R V Castro
- CNRS UMR7102, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR7102, Paris, France
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69
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Rich TC, Webb KJ, Leavesley SJ. Can we decipher the information content contained within cyclic nucleotide signals? J Gen Physiol 2014; 143:17-27. [PMID: 24378904 PMCID: PMC3874573 DOI: 10.1085/jgp.201311095] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Thomas C. Rich
- Center for Lung Biology, Department of Pharmacology, Basic Medical Sciences Graduate Program, and Department of Pharmacology, College of Medicine; and Department of Chemical and Biomolecular Engineering, College of Engineering, University of South Alabama, Mobile, AL 36688
| | - Kristal J. Webb
- Center for Lung Biology, Department of Pharmacology, Basic Medical Sciences Graduate Program, and Department of Pharmacology, College of Medicine; and Department of Chemical and Biomolecular Engineering, College of Engineering, University of South Alabama, Mobile, AL 36688
| | - Silas J. Leavesley
- Center for Lung Biology, Department of Pharmacology, Basic Medical Sciences Graduate Program, and Department of Pharmacology, College of Medicine; and Department of Chemical and Biomolecular Engineering, College of Engineering, University of South Alabama, Mobile, AL 36688
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70
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Dopaminergic tone regulates transient potassium current maximal conductance through a translational mechanism requiring D1Rs, cAMP/PKA, Erk and mTOR. BMC Neurosci 2013; 14:143. [PMID: 24225021 PMCID: PMC3840709 DOI: 10.1186/1471-2202-14-143] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 11/07/2013] [Indexed: 01/09/2023] Open
Abstract
Background Dopamine (DA) can produce divergent effects at different time scales. DA has opposing immediate and long-term effects on the transient potassium current (IA) within neurons of the pyloric network, in the Panulirus interruptus stomatogastric ganglion. The lateral pyloric neuron (LP) expresses type 1 DA receptors (D1Rs). A 10 min application of 5-100 μM DA decreases LP IA by producing a decrease in IA maximal conductance (Gmax) and a depolarizing shift in IA voltage dependence through a cAMP-Protein kinase A (PKA) dependent mechanism. Alternatively, a 1 hr application of DA (≥5 nM) generates a persistent (measured 4 hr after DA washout) increase in IA Gmax in the same neuron, through a mechanistic target of rapamycin (mTOR) dependent translational mechanism. We examined the dose, time and protein dependencies of the persistent DA effect. Results We found that disrupting normal modulatory tone decreased LP IA. Addition of 500 pM-5 nM DA to the saline for 1 hr prevented this decrease, and in the case of a 5 nM DA application, the effect was sustained for >4 hrs after DA removal. To determine if increased cAMP mediated the persistent effect of 5nM DA, we applied the cAMP analog, 8-bromo-cAMP alone or with rapamycin for 1 hr, followed by wash and TEVC. 8-bromo-cAMP induced an increase in IA Gmax, which was blocked by rapamycin. Next we tested the roles of PKA and guanine exchange factor protein activated by cAMP (ePACs) in the DA-induced persistent change in IA using the PKA specific antagonist Rp-cAMP and the ePAC specific agonist 8-pCPT-2′-O-Me-cAMP. The PKA antagonist blocked the DA induced increases in LP IA Gmax, whereas the ePAC agonist did not induce an increase in LP IA Gmax. Finally we tested whether extracellular signal regulated kinase (Erk) activity was necessary for the persistent effect by co-application of Erk antagonists PD98059 or U0126 with DA. Erk antagonism blocked the DA induced persistent increase in LP IA. Conclusions These data suggest that dopaminergic tone regulates ion channel density in a concentration and time dependent manner. The D1R- PKA axis, along with Erk and mTOR are necessary for the persistent increase in LP IA induced by high affinity D1Rs.
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Cazabat L, Ragazzon B, Varin A, Potier-Cartereau M, Vandier C, Vezzosi D, Risk-Rabin M, Guellich A, Schittl J, Lechêne P, Richter W, Nikolaev VO, Zhang J, Bertherat J, Vandecasteele G. Inactivation of the Carney complex gene 1 (PRKAR1A) alters spatiotemporal regulation of cAMP and cAMP-dependent protein kinase: a study using genetically encoded FRET-based reporters. Hum Mol Genet 2013; 23:1163-74. [PMID: 24122441 DOI: 10.1093/hmg/ddt510] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Carney complex (CNC) is a hereditary disease associating cardiac myxoma, spotty skin pigmentation and endocrine overactivity. CNC is caused by inactivating mutations in the PRKAR1A gene encoding PKA type I alpha regulatory subunit (RIα). Although PKA activity is enhanced in CNC, the mechanisms linking PKA dysregulation to endocrine tumorigenesis are poorly understood. In this study, we used Förster resonance energy transfer (FRET)-based sensors for cAMP and PKA activity to define the role of RIα in the spatiotemporal organization of the cAMP/PKA pathway. RIα knockdown in HEK293 cells increased basal as well as forskolin or prostaglandin E1 (PGE1)-stimulated total cellular PKA activity as reported by western blots of endogenous PKA targets and the FRET-based global PKA activity reporter, AKAR3. Using variants of AKAR3 targeted to subcellular compartments, we identified similar increases in the response to PGE1 in the cytoplasm and at the outer mitochondrial membrane. In contrast, at the plasma membrane, the response to PGE1 was decreased along with an increase in basal FRET ratio. These results were confirmed by western blot analysis of basal and PGE1-induced phosphorylation of membrane-associated vasodilator-stimulated phosphoprotein. Similar differences were observed between the cytoplasm and the plasma membrane in human adrenal cells carrying a RIα inactivating mutation. RIα inactivation also increased cAMP in the cytoplasm, at the outer mitochondrial membrane and at the plasma membrane, as reported by targeted versions of the cAMP indicator Epac1-camps. These results show that RIα inactivation leads to multiple, compartment-specific alterations of the cAMP/PKA pathway revealing new aspects of signaling dysregulation in tumorigenesis.
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72
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Wei H, Ren Y, Wang ZY. A computational neural model of orientation detection based on multiple guesses: comparison of geometrical and algebraic models. Cogn Neurodyn 2013; 7:361-79. [PMID: 24427212 PMCID: PMC3773326 DOI: 10.1007/s11571-012-9235-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 11/09/2012] [Accepted: 12/14/2012] [Indexed: 02/03/2023] Open
Abstract
The implementation of Hubel-Wiesel hypothesis that orientation selectivity of a simple cell is based on ordered arrangement of its afferent cells has some difficulties. It requires the receptive fields (RFs) of those ganglion cells (GCs) and LGN cells to be similar in size and sub-structure and highly arranged in a perfect order. It also requires an adequate number of regularly distributed simple cells to match ubiquitous edges. However, the anatomical and electrophysiological evidence is not strong enough to support this geometry-based model. These strict regularities also make the model very uneconomical in both evolution and neural computation. We propose a new neural model based on an algebraic method to estimate orientations. This approach synthesizes the guesses made by multiple GCs or LGN cells and calculates local orientation information subject to a group of constraints. This algebraic model need not obey the constraints of Hubel-Wiesel hypothesis, and is easily implemented with a neural network. By using the idea of a satisfiability problem with constraints, we also prove that the precision and efficiency of this model are mathematically practicable. The proposed model makes clear several major questions which Hubel-Wiesel model does not account for. Image-rebuilding experiments are conducted to check whether this model misses any important boundary in the visual field because of the estimation strategy. This study is significant in terms of explaining the neural mechanism of orientation detection, and finding the circuit structure and computational route in neural networks. For engineering applications, our model can be used in orientation detection and as a simulation platform for cell-to-cell communications to develop bio-inspired eye chips.
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Affiliation(s)
- Hui Wei
- Laboratory of Cognitive Model and Algorithm, School of Computer Science, Fudan University, Shanghai, 200433 China
| | - Yuan Ren
- Laboratory of Cognitive Model and Algorithm, School of Computer Science, Fudan University, Shanghai, 200433 China
| | - Zi Yan Wang
- Laboratory of Cognitive Model and Algorithm, School of Computer Science, Fudan University, Shanghai, 200433 China
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73
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Shen JX, Cooper DMF. AKAP79, PKC, PKA and PDE4 participate in a Gq-linked muscarinic receptor and adenylate cyclase 2 cAMP signalling complex. Biochem J 2013; 455:47-56. [PMID: 23889134 PMCID: PMC3968274 DOI: 10.1042/bj20130359] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
AC2 (adenylate cyclase 2) is stimulated by activation of Gq-coupled muscarinic receptors through PKC (protein kinase C) to generate localized cAMP in HEK (human embryonic kidney)-293 cells. In the present study, we utilized a sensitive live-cell imaging technique to unravel the proteins that play essential roles in a Gq-coupled muscarinic receptor-mediated cAMP signalling complex. We reveal that, upon agonist binding to the Gq-coupled muscarinic receptor, AKAP79 (A-kinase-anchoring protein 79) recruits PKC to activate AC2 to produce cAMP. The cAMP formed is degraded by PDE4 (phosphodiesterase 4) activated by an AKAP-anchored PKA (protein kinase A). Calcineurin, a phosphatase bound to AKAP79, is not involved in this regulation. Overall, a transient cAMP increase is generated from AC2 by Gq-coupled muscarinic receptor activation, subject to sophisticated regulation through AKAP79, PKC, PDE4 and PKA, which significantly enhances acetylcholine-mediated signalling.
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Affiliation(s)
- Jia X. Shen
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Dermot M. F. Cooper
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
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74
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Balczon R, Prasain N, Ochoa C, Prater J, Zhu B, Alexeyev M, Sayner S, Frank DW, Stevens T. Pseudomonas aeruginosa exotoxin Y-mediated tau hyperphosphorylation impairs microtubule assembly in pulmonary microvascular endothelial cells. PLoS One 2013; 8:e74343. [PMID: 24023939 PMCID: PMC3762819 DOI: 10.1371/journal.pone.0074343] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 08/01/2013] [Indexed: 12/21/2022] Open
Abstract
Pseudomonas aeruginosa uses a type III secretion system to introduce the adenylyl and guanylyl cyclase exotoxin Y (ExoY) into the cytoplasm of endothelial cells. ExoY induces Tau hyperphosphorylation and insolubility, microtubule breakdown, barrier disruption and edema, although the mechanism(s) responsible for microtubule breakdown remain poorly understood. Here we investigated both microtubule behavior and centrosome activity to test the hypothesis that ExoY disrupts microtubule dynamics. Fluorescence microscopy determined that infected pulmonary microvascular endothelial cells contained fewer microtubules than control cells, and further studies demonstrated that the microtubule-associated protein Tau was hyperphosphorylated following infection and dissociated from microtubules. Disassembly/reassembly studies determined that microtubule assembly was disrupted in infected cells, with no detectable effects on either microtubule disassembly or microtubule nucleation by centrosomes. This effect of ExoY on microtubules was abolished when the cAMP-dependent kinase phosphorylation site (Ser-214) on Tau was mutated to a non-phosphorylatable form. These studies identify Tau in microvascular endothelial cells as the target of ExoY in control of microtubule architecture following pulmonary infection by Pseudomonas aeruginosa and demonstrate that phosphorylation of tau following infection decreases microtubule assembly.
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Affiliation(s)
- Ron Balczon
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama, United States of America
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
- * E-mail:
| | - Nutan Prasain
- Department of Pediatrics, University of Indiana School of Medicine, Indianapolis, Indiana, United States of America
| | - Cristhiaan Ochoa
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
- Department of Pharmacology, University of South Alabama, Mobile, Alabama, United States of America
| | - Jason Prater
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
- Department of Medicine, University of South Alabama, Mobile, Alabama, United States of America
| | - Bing Zhu
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
- Department of Pharmacology, University of South Alabama, Mobile, Alabama, United States of America
| | - Mikhail Alexeyev
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama, United States of America
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
| | - Sarah Sayner
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama, United States of America
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
| | - Dara W. Frank
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Troy Stevens
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America
- Department of Pharmacology, University of South Alabama, Mobile, Alabama, United States of America
- Department of Medicine, University of South Alabama, Mobile, Alabama, United States of America
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75
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Perera RK, Nikolaev VO. Compartmentation of cAMP signalling in cardiomyocytes in health and disease. Acta Physiol (Oxf) 2013; 207:650-62. [PMID: 23383621 DOI: 10.1111/apha.12077] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 11/27/2012] [Accepted: 01/30/2013] [Indexed: 12/13/2022]
Abstract
3',5'-cyclic adenosine monophosphate (cAMP) is a ubiquitous second messenger critically involved in the regulation of heart function. It has been shown to act in discrete subcellular signalling compartments formed by differentially localized receptors, phosphodiesterases and protein kinases. Cardiac diseases such as hypertrophy or heart failure are associated with structural and functional remodelling of these microdomains which leads to changes in cAMP compartmentation. In this review, we will discuss recent key findings which provided new insights into cAMP compartmentation in cardiomyocytes with a particular focus on its alterations in heart disease.
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Affiliation(s)
- R. K. Perera
- Emmy Noether Group of the DFG, Department of Cardiology and Pneumology, European Heart Research Insitute Göttingen, Georg August University Medical Center; University of Göttingen; Göttingen; Germany
| | - V. O. Nikolaev
- Emmy Noether Group of the DFG, Department of Cardiology and Pneumology, European Heart Research Insitute Göttingen, Georg August University Medical Center; University of Göttingen; Göttingen; Germany
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76
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Cheepala S, Hulot JS, Morgan JA, Sassi Y, Zhang W, Naren AP, Schuetz JD. Cyclic nucleotide compartmentalization: contributions of phosphodiesterases and ATP-binding cassette transporters. Annu Rev Pharmacol Toxicol 2012; 53:231-53. [PMID: 23072381 DOI: 10.1146/annurev-pharmtox-010611-134609] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cyclic nucleotides [e.g., cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP)] are ubiquitous second messengers that affect multiple cell functions from maturation of the egg to cell division, growth, differentiation, and death. The concentration of cAMP can be regulated by processes within membrane domains (local regulation) as well as throughout a cell (global regulation). The phosphodiesterases (PDEs) that degrade cAMP have well-known roles in both these processes. It has recently been discovered that ATP-binding cassette (ABC) transporters contribute to both local and global regulation of cAMP. This regulation may require the formation of macromolecular complexes. Some of these transporters are ubiquitously expressed, whereas others are more tissue restricted. Because some PDE inhibitors are also ABC transporter inhibitors, it is conceivable that the therapeutic benefits of their use result from the combined inhibition of both PDEs and ABC transporters. Deciphering the individual contributions of PDEs and ABC transporters to such drug effects may lead to improved therapeutic benefits.
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Affiliation(s)
- Satish Cheepala
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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77
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Tian G, Sågetorp J, Xu Y, Shuai H, Degerman E, Tengholm A. Role of phosphodiesterases in the shaping of sub-plasma-membrane cAMP oscillations and pulsatile insulin secretion. J Cell Sci 2012; 125:5084-95. [PMID: 22946044 DOI: 10.1242/jcs.107201] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Specificity and versatility in cyclic AMP (cAMP) signalling are governed by the spatial localisation and temporal dynamics of the signal. Phosphodiesterases (PDEs) are important for shaping cAMP signals by hydrolyzing the nucleotide. In pancreatic β-cells, glucose triggers sub-plasma-membrane cAMP oscillations, which are important for insulin secretion, but the mechanisms underlying the oscillations are poorly understood. Here, we investigated the role of different PDEs in the generation of cAMP oscillations by monitoring the concentration of cAMP in the sub-plasma-membrane space ([cAMP](pm)) with ratiometric evanescent wave microscopy in MIN6 cells or mouse pancreatic β-cells expressing a fluorescent translocation biosensor. The general PDE inhibitor IBMX increased [cAMP](pm), and whereas oscillations were frequently observed at 50 µM IBMX, 300 µM-1 mM of the inhibitor caused a stable increase in [cAMP](pm). The [cAMP](pm) was nevertheless markedly suppressed by the adenylyl cyclase inhibitor 2',5'-dideoxyadenosine, indicating IBMX-insensitive cAMP degradation. Among IBMX-sensitive PDEs, PDE3 was most important for maintaining a low basal level of [cAMP](pm) in unstimulated cells. After glucose induction of [cAMP](pm) oscillations, inhibitors of PDE1, PDE3 and PDE4 inhibitors the average cAMP level, often without disturbing the [cAMP](pm) rhythmicity. Knockdown of the IBMX-insensitive PDE8B by shRNA in MIN6 cells increased the basal level of [cAMP](pm) and prevented the [cAMP](pm)-lowering effect of 2',5'-dideoxyadenosine after exposure to IBMX. Moreover, PDE8B-knockdown cells showed reduced glucose-induced [cAMP](pm) oscillations and loss of the normal pulsatile pattern of insulin secretion. It is concluded that [cAMP](pm) oscillations in β-cells are caused by periodic variations in cAMP generation, and that several PDEs, including PDE1, PDE3 and the IBMX-insensitive PDE8B, are required for shaping the sub-membrane cAMP signals and pulsatile insulin release.
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Affiliation(s)
- Geng Tian
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre Box 571, SE-751 23 Uppsala, Sweden
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78
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Riise J, Ørstavik Ø, Qvigstad E, Dahl CP, Osnes JB, Skomedal T, Levy FO, Krobert KA. Prostaglandin E1 facilitates inotropic effects of 5-HT4 serotonin receptors and β-adrenoceptors in failing human heart. Basic Res Cardiol 2012; 107:295. [PMID: 22923058 DOI: 10.1007/s00395-012-0295-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 06/26/2012] [Accepted: 08/02/2012] [Indexed: 11/30/2022]
Abstract
Prostaglandins have displayed both beneficial and detrimental effects in clinical studies in patients with severe heart failure. Prostaglandins are known to increase cardiac output, but the mechanism is not clarified. Here, we tested the hypothesis that prostaglandins can increase contractility in human heart by amplifying cAMP-dependent inotropic responses. Contractility was measured ex vivo in isolated left ventricular strips and phosphodiesterase (PDE) and adenylyl cyclase (AC) activity was measured in homogenates or membranes from failing human left ventricles. PGE(1) (1 µM) alone did not modify contractility, but given prior, amplified maximal serotonin (5-HT)-evoked (10 µM) contractile responses mediated by 5-HT(4) receptors several fold (24 ± 7 % with PGE(1) vs. 3 ± 2 % above basal with 5-HT alone). The 5-HT(4)-mediated inotropic response was amplified by the PDE3 inhibitor cilostamide and further amplified in combination with PGE(1) (26 ± 6 vs. 56 ± 12 % above basal). PGE(1) reduced the time to reach 90 % of both the maximal 5-HT- and isoproterenol-evoked inotropic response compared to 5-HT or isoproterenol alone. PGE(1) did not modify PDE activity in the homogenate, either alone or when given simultaneously with PDE3 and/or PDE4 inhibitors. Neither 5-HT- nor isoproterenol-stimulated AC activity was significantly amplified by PGE(1). Sensitivity of ventricular strips to Ca(2+) was not enhanced in the presence of PGE(1). Our results show that PGE(1) can enhance cAMP-mediated responses in failing human left ventricle, through a mechanism independent of PDE inhibition, amplification of AC activity or increasing sensitivity to calcium. This effect of PGE(1) possibly contributes to the increase of cardiac output, independent of decreased afterload, observed after prostaglandin administration in humans.
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Affiliation(s)
- Jon Riise
- Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Sognsvannsvn. 20, Blindern, Oslo, Norway
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Bagavandoss P, Grimshaw S. Distribution of adenylyl cyclases in the rat ovary by immunofluorescence microscopy. Anat Rec (Hoboken) 2012; 295:1717-26. [PMID: 22899545 DOI: 10.1002/ar.22550] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 07/16/2012] [Indexed: 12/11/2022]
Abstract
In the mammalian ovary both gonadotropins and local cytokines, acting through G-protein coupled receptors, govern the physiology of the ovary in part by regulating the cyclic adenosine 3',5'-monophosphate via adenylyl cyclases. The nine transmembrane adenylyl cyclases and a soluble adenylyl cyclase are regulated by a diversity of ligands. In this study we have examined the rat ovaries, prior to and subsequent to gonadotropin treatment, for the presence of different transmembrane adenylyl cyclases by indirect immunofluorescence microscopy. Adenylyl cyclase I immunoreactivity was observed in the nuclei of oocytes in preantral and antral follicles along with some staining in granulosa cells. Equine chorionic gonadotropin injection increased adenylyl cyclase I staining in granulosa cells. Adenylyl cyclase I staining was also observed in luteal and endothelial cells. Adenylyl cyclase II was observed throughout the ovary, including granulosa cells and the ovarian surface epithelium. Adenylyl cyclase II staining was also found to increase in granulosa cells after equine chorionic gonadotropin injection. Adenylyl cyclase III was distributed primarily in theca and smooth muscle cells of arterioles, with faint staining in the oocytes of equine chorionic gonadotropin-injected ovaries. Adenylyl cyclase IV staining was present throughout the ovary, including the nuclei of oocytes. Adenylyl cyclase VIII staining in granulosa cells increased subsequent to equine chorionic gonadotropin injection and remained in luteal cells. Our study reveals the redundancy of adenylyl cyclases present in the rat ovary and, therefore, implies potential regulation of follicular and corpus luteum physiology by cyclic adenosine 3',5'-monophosphate generated through distinct adenylyl cyclases.
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Affiliation(s)
- P Bagavandoss
- Department of Biological Sciences, Kent State University at Stark, North Canton, Ohio, USA.
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80
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Calcineurin regulates homologous desensitization of natriuretic peptide receptor-A and inhibits ANP-induced testosterone production in MA-10 cells. PLoS One 2012; 7:e41711. [PMID: 22876290 PMCID: PMC3410877 DOI: 10.1371/journal.pone.0041711] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 06/25/2012] [Indexed: 12/30/2022] Open
Abstract
Receptor desensitization is a ubiquitous regulatory mechanism that defines the activatable pool of receptors, and thus, the ability of cells to respond to environmental stimuli. In recent years, the molecular mechanisms controlling the desensitization of a variety of receptors have been established. However, little is known about the molecular mechanisms that underlie desensitization of natriuretic peptide receptors, including natriuretic peptide receptor-A (NPR-A). Here we report that calcineurin (protein phosphatase 2B, PP2B, PPP3C) regulates homologous desensitization of NPR-A in murine Leydig tumor (MA-10) cells. We demonstrate that both pharmacological inhibition of calcineurin activity and siRNA-mediated suppression of calcineurin expression potentiate atrial natriuretic peptide (ANP)-induced cGMP synthesis. Treatment of MA-10 cells with inhibitors of other phosphoprotein phosphatases had little or no effect on ANP-induced cGMP accumulation. In addition, overexpression of calcineurin blunts ANP-induced cGMP synthesis. We also present data indicating that the inhibition of calcineurin potentiates ANP-induced testosterone production. To better understand the contribution of calcineurin in the regulation of NPR-A activity, we examined the kinetics of ANP-induced cGMP signals. We observed transient ANP-induced cGMP signals, even in the presence of phosphodiesterase inhibitors. Inhibition of both calcineurin and phosphodiesterase dramatically slowed the decay in the response. These observations are consistent with a model in which calcineurin mediated dephosphorylation and desensitization of NPR-A is associated with significant inhibition of cGMP synthesis. PDE activity hydrolyzes cGMP, thus lowering intracellular cGMP toward the basal level. Taken together, these data suggest that calcineurin plays a previously unrecognized role in the desensitization of NPR-A and, thereby, inhibits ANP-mediated increases in testosterone production.
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81
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Kolodecik TR, Shugrue CA, Thrower EC, Levin LR, Buck J, Gorelick FS. Activation of soluble adenylyl cyclase protects against secretagogue stimulated zymogen activation in rat pancreaic acinar cells. PLoS One 2012; 7:e41320. [PMID: 22844459 PMCID: PMC3402497 DOI: 10.1371/journal.pone.0041320] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 06/20/2012] [Indexed: 01/11/2023] Open
Abstract
An early feature of acute pancreatitis is activation of zymogens, such as trypsinogen, within the pancreatic acinar cell. Supraphysiologic concentrations of the hormone cholecystokinin (CCK; 100 nM), or its orthologue cerulein (CER), induce zymogen activation and elevate levels of cAMP in pancreatic acinar cells. The two classes of adenylyl cyclase, trans-membrane (tmAC) and soluble (sAC), are activated by distinct mechanisms, localize to specific subcellular domains, and can produce locally high concentrations of cAMP. We hypothesized that sAC activity might selectively modulate acinar cell zymogen activation. sAC was identified in acinar cells by PCR and immunoblot. It localized to the apical region of the cell under resting conditions and redistributed intracellularly after treatment with supraphysiologic concentrations of cerulein. In cerulein-treated cells, pre-incubation with a trans-membrane adenylyl cyclase inhibitor did not affect zymogen activation or amylase secretion. However, treatment with a sAC inhibitor (KH7), or inhibition of a downstream target of cAMP, protein kinase A (PKA), significantly enhanced secretagogue-stimulated zymogen activation and amylase secretion. Activation of sAC with bicarbonate significantly inhibited secretagogue-stimulated zymogen activation; this response was decreased by inhibition of sAC or PKA. Bicarbonate also enhanced secretagogue-stimulated cAMP accumulation; this effect was inhibited by KH7. Bicarbonate treatment reduced secretagogue-stimulated acinar cell vacuolization, an early marker of pancreatitis. These data suggest that activation of sAC in the pancreatic acinar cell has a protective effect and reduces the pathologic activation of proteases during pancreatitis.
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Affiliation(s)
- Thomas R. Kolodecik
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Veterans Administration Connecticut Healthcare, West Haven, Connecticut, United States of America
| | - Christine A. Shugrue
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Veterans Administration Connecticut Healthcare, West Haven, Connecticut, United States of America
| | - Edwin C. Thrower
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Veterans Administration Connecticut Healthcare, West Haven, Connecticut, United States of America
| | - Lonny R. Levin
- Department of Pharmacology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Jochen Buck
- Department of Pharmacology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Fred S. Gorelick
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Veterans Administration Connecticut Healthcare, West Haven, Connecticut, United States of America
- * E-mail:
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Abstract
Cyclic di-GMP (c-di-GMP) is a second messenger molecule that regulates the transition between sessile and motile lifestyles in bacteria. Bacteria often encode multiple diguanylate cyclase (DGC) and phosphodiesterase (PDE) enzymes that produce and degrade c-di-GMP, respectively. Because of multiple inputs into the c-di-GMP-signaling network, it is unclear whether this system functions via high or low specificity. High-specificity signaling is characterized by individual DGCs or PDEs that are specifically associated with downstream c-di-GMP-mediated responses. In contrast, low-specificity signaling is characterized by DGCs or PDEs that modulate a general signal pool, which, in turn, controls a global c-di-GMP-mediated response. To determine whether c-di-GMP functions via high or low specificity in Vibrio cholerae, we correlated the in vivo c-di-GMP concentration generated by seven DGCs, each expressed at eight different levels, to the c-di-GMP-mediated induction of biofilm formation and transcription. There was no correlation between total intracellular c-di-GMP levels and biofilm formation or gene expression when considering all states. However, individual DGCs showed a significant correlation between c-di-GMP production and c-di-GMP-mediated responses. Moreover, the rate of phenotypic change versus c-di-GMP concentration was significantly different between DGCs, suggesting that bacteria can optimize phenotypic output to c-di-GMP levels via expression or activation of specific DGCs. Our results conclusively demonstrate that c-di-GMP does not function via a simple, low-specificity signaling pathway in V. cholerae.
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83
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Horvat SJ, Deshpande DA, Yan H, Panettieri RA, Codina J, DuBose TD, Xin W, Rich TC, Penn RB. A-kinase anchoring proteins regulate compartmentalized cAMP signaling in airway smooth muscle. FASEB J 2012; 26:3670-9. [PMID: 22649031 DOI: 10.1096/fj.11-201020] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A-kinase anchoring proteins (AKAPs) have emerged as important regulatory molecules that can compartmentalize cAMP signaling transduced by β2-adrenergic receptors (β(2)ARs); such compartmentalization ensures speed and fidelity of cAMP signaling and effects on cell function. This study aimed to assess the role of AKAPs in regulating global and compartmentalized β(2)AR signaling in human airway smooth muscle (ASM). Transcriptome and proteomic analyses were used to characterize AKAP expression in ASM. Stable expression or injection of peptides AKAP-IS or Ht31 was used to disrupt AKAP-PKA interactions, and global and compartmentalized cAMP accumulation stimulated by β-agonist was assessed by radioimmunoassay and membrane-delineated flow through cyclic nucleotide-gated channels, respectively. ASM expresses multiple AKAP family members, with gravin and ezrin among the most readily detected. AKAP-PKA disruption had minimal effects on whole-cell cAMP accumulation stimulated by β-agonist (EC(50) and B(max)) concentrations, but significantly increased the duration of plasma membrane-delineated cAMP (τ=251±51 s for scrambled peptide control vs. 399±79 s for Ht31). Direct PKA inhibition eliminated decay of membrane-delineated cAMP levels. AKAPs coordinate compartmentalized cAMP signaling in ASM cells by regulating multiple elements of β(2)AR-mediated cAMP accumulation, thereby representing a novel target for manipulating β(2)AR signaling and function in ASM.
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Affiliation(s)
- Sarah J Horvat
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201-1075, USA
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84
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Vandamme J, Castermans D, Thevelein JM. Molecular mechanisms of feedback inhibition of protein kinase A on intracellular cAMP accumulation. Cell Signal 2012; 24:1610-8. [PMID: 22522182 DOI: 10.1016/j.cellsig.2012.04.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 03/22/2012] [Accepted: 04/04/2012] [Indexed: 01/13/2023]
Abstract
The cAMP-protein kinase A (PKA) pathway is a major signalling pathway in the yeast Saccharomyces cerevisiae, but also in many other eukaryotic cell types, including mammalian cells. Since cAMP plays a crucial role as second messenger in the regulation of this pathway, its levels are strictly controlled, both in the basal condition and after induction by agonists. A major factor in the down-regulation of the cAMP level after stimulation is PKA itself. Activation of PKA triggers feedback down-regulation of the increased cAMP level, stimulating its return to the basal concentration. This is accomplished at different levels. The best documented mechanisms are: inhibition of cAMP synthesis by down-regulation of adenylate cyclase and/or its regulatory proteins, stimulation of cAMP breakdown by phosphodiesterases and spatial regulation of cAMP levels in the cell by A-Kinase Anchoring Proteins (AKAPs). In this review we describe these processes in detail for S. cerevisiae, for cells of mammals and selected other organisms, and we hint at other possible targets for feedback regulation of intracellular cAMP levels.
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85
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Lohse MJ, Nuber S, Hoffmann C. Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling. Pharmacol Rev 2012; 64:299-336. [PMID: 22407612 DOI: 10.1124/pr.110.004309] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fluorescence and bioluminescence resonance energy transfer (FRET and BRET) techniques allow the sensitive monitoring of distances between two labels at the nanometer scale. Depending on the placement of the labels, this permits the analysis of conformational changes within a single protein (for example of a receptor) or the monitoring of protein-protein interactions (for example, between receptors and G-protein subunits). Over the past decade, numerous such techniques have been developed to monitor the activation and signaling of G-protein-coupled receptors (GPCRs) in both the purified, reconstituted state and in intact cells. These techniques span the entire spectrum from ligand binding to the receptors down to intracellular second messengers. They allow the determination and the visualization of signaling processes with high temporal and spatial resolution. With these techniques, it has been demonstrated that GPCR signals may show spatial and temporal patterning. In particular, evidence has been provided for spatial compartmentalization of GPCRs and their signals in intact cells and for distinct physiological consequences of such spatial patterning. We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments.
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Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, Versbacher Str. 9, 97078 Würzburg, Germany.
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86
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Alekseev AE, Reyes S, Selivanov VA, Dzeja PP, Terzic A. Compartmentation of membrane processes and nucleotide dynamics in diffusion-restricted cardiac cell microenvironment. J Mol Cell Cardiol 2012; 52:401-9. [PMID: 21704043 PMCID: PMC3264845 DOI: 10.1016/j.yjmcc.2011.06.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 01/08/2023]
Abstract
Orchestrated excitation-contraction coupling in heart muscle requires adequate spatial arrangement of systems responsible for ion movement and metabolite turnover. Co-localization of regulatory and transporting proteins into macromolecular complexes within an environment of microanatomical cell components raises intracellular diffusion barriers that hamper the mobility of metabolites and signaling molecules. Compared to substrate diffusion in the cytosol, diffusional restrictions underneath the sarcolemma are much larger and could impede ion and nucleotide movement by a factor of 10(3)-10(5). Diffusion barriers thus seclude metabolites within the submembrane space enabling rapid and vectorial effector targeting, yet hinder energy supply from the bulk cytosolic space implicating the necessity for a shunting transfer mechanism. Here, we address principles of membrane protein compartmentation, phosphotransfer enzyme-facilitated interdomain energy transfer, and nucleotide signal dynamics at the subsarcolemma-cytosol interface. This article is part of a Special Issue entitled "Local Signaling in Myocytes".
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Affiliation(s)
- Alexey E. Alekseev
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Santiago Reyes
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Vitaly A. Selivanov
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, and IBUB Barcelona, Gran Via de les Corts Catalanes 585, 08007 Barcelona, Spain
| | - Petras P. Dzeja
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Andre Terzic
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
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87
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Bailes HJ, Zhuang LY, Lucas RJ. Reproducible and sustained regulation of Gαs signalling using a metazoan opsin as an optogenetic tool. PLoS One 2012; 7:e30774. [PMID: 22292038 PMCID: PMC3265508 DOI: 10.1371/journal.pone.0030774] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 12/26/2011] [Indexed: 01/18/2023] Open
Abstract
Originally developed to regulate neuronal excitability, optogenetics is increasingly also used to control other cellular processes with unprecedented spatiotemporal resolution. Optogenetic modulation of all major G-protein signalling pathways (Gq, Gi and Gs) has been achieved using variants of mammalian rod opsin. We show here that the light response driven by such rod opsin-based tools dissipates under repeated exposure, consistent with the known bleaching characteristics of this photopigment. We continue to show that replacing rod opsin with a bleach resistant opsin from Carybdea rastonii, the box jellyfish, (JellyOp) overcomes this limitation. Visible light induced high amplitude, reversible, and reproducible increases in cAMP in mammalian cells expressing JellyOp. While single flashes produced a brief cAMP spike, repeated stimulation could sustain elevated levels for 10s of minutes. JellyOp was more photosensitive than currently available optogenetic tools, responding to white light at irradiances ≥1 µW/cm(2). We conclude that JellyOp is a promising new tool for mimicking the activity of Gs-coupled G protein coupled receptors with fine spatiotemporal resolution.
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Affiliation(s)
- Helena J Bailes
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
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88
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Feinstein WP, Zhu B, Leavesley SJ, Sayner SL, Rich TC. Assessment of cellular mechanisms contributing to cAMP compartmentalization in pulmonary microvascular endothelial cells. Am J Physiol Cell Physiol 2011; 302:C839-52. [PMID: 22116306 DOI: 10.1152/ajpcell.00361.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cyclic AMP signals encode information required to differentially regulate a wide variety of cellular responses; yet it is not well understood how information is encrypted within these signals. An emerging concept is that compartmentalization underlies specificity within the cAMP signaling pathway. This concept is based on a series of observations indicating that cAMP levels are distinct in different regions of the cell. One such observation is that cAMP production at the plasma membrane increases pulmonary microvascular endothelial barrier integrity, whereas cAMP production in the cytosol disrupts barrier integrity. To better understand how cAMP signals might be compartmentalized, we have developed mathematical models in which cellular geometry as well as total adenylyl cyclase and phosphodiesterase activities were constrained to approximate values measured in pulmonary microvascular endothelial cells. These simulations suggest that the subcellular localizations of adenylyl cyclase and phosphodiesterase activities are by themselves insufficient to generate physiologically relevant cAMP gradients. Thus, the assembly of adenylyl cyclase, phosphodiesterase, and protein kinase A onto protein scaffolds is by itself unlikely to ensure signal specificity. Rather, our simulations suggest that reductions in the effective cAMP diffusion coefficient may facilitate the formation of substantial cAMP gradients. We conclude that reductions in the effective rate of cAMP diffusion due to buffers, structural impediments, and local changes in viscosity greatly facilitate the ability of signaling complexes to impart specificity within the cAMP signaling pathway.
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Affiliation(s)
- Wei P Feinstein
- Center for Lung Biology, University of South Alabama, Mobile, Alabama 36688, USA
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89
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Harvey RD. How uniform is cAMP signaling? Focus on “Systems analysis of GLP-1 receptor signaling in pancreatic β-cells”. Am J Physiol Cell Physiol 2011; 301:C775-6. [DOI: 10.1152/ajpcell.00245.2011] [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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90
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Bucher D, Goaillard JM. Beyond faithful conduction: short-term dynamics, neuromodulation, and long-term regulation of spike propagation in the axon. Prog Neurobiol 2011; 94:307-46. [PMID: 21708220 PMCID: PMC3156869 DOI: 10.1016/j.pneurobio.2011.06.001] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 05/27/2011] [Accepted: 06/07/2011] [Indexed: 12/13/2022]
Abstract
Most spiking neurons are divided into functional compartments: a dendritic input region, a soma, a site of action potential initiation, an axon trunk and its collaterals for propagation of action potentials, and distal arborizations and terminals carrying the output synapses. The axon trunk and lower order branches are probably the most neglected and are often assumed to do nothing more than faithfully conducting action potentials. Nevertheless, there are numerous reports of complex membrane properties in non-synaptic axonal regions, owing to the presence of a multitude of different ion channels. Many different types of sodium and potassium channels have been described in axons, as well as calcium transients and hyperpolarization-activated inward currents. The complex time- and voltage-dependence resulting from the properties of ion channels can lead to activity-dependent changes in spike shape and resting potential, affecting the temporal fidelity of spike conduction. Neural coding can be altered by activity-dependent changes in conduction velocity, spike failures, and ectopic spike initiation. This is true under normal physiological conditions, and relevant for a number of neuropathies that lead to abnormal excitability. In addition, a growing number of studies show that the axon trunk can express receptors to glutamate, GABA, acetylcholine or biogenic amines, changing the relative contribution of some channels to axonal excitability and therefore rendering the contribution of this compartment to neural coding conditional on the presence of neuromodulators. Long-term regulatory processes, both during development and in the context of activity-dependent plasticity may also affect axonal properties to an underappreciated extent.
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Affiliation(s)
- Dirk Bucher
- The Whitney Laboratory and Department of Neuroscience, University of Florida, St. Augustine, FL 32080, USA.
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91
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Xin W, Yang X, Rich TC, Krieg T, Barrington R, Cohen MV, Downey JM. All preconditioning-related G protein-coupled receptors can be demonstrated in the rabbit cardiomyocyte. J Cardiovasc Pharmacol Ther 2011; 17:190-8. [PMID: 21828281 DOI: 10.1177/1074248411416815] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
G protein-coupled receptors for adenosine (A(1), A(3), A(2A), and A(2B)), bradykinin (B(1)) and opioids (δ) are all involved in the mechanism of ischemic preconditioning. Although the heart is comprised of many tissue types, it has been assumed that preconditioning's protective signaling occurs in the cardiomyocyte. We critically tested that hypothesis by testing for the presence of each of these receptors in isolated adult rabbit ventricular myocytes that had been transfected with cyclic nucleotide-gated (CNG) ion channels. Because subsarcolemmal cyclic adenosine monophosphate (cAMP) opens the CNG channels, we could monitor cAMP levels within a single cardiomyocyte by measuring channel current with a patch pipette. The presence of a receptor would be confirmed if we could alter cAMP in the cell with a selective agonist to the receptor being studied. Superfusion with the β-adrenergic G(s)-coupled receptor agonist isoproterenol (50 nmol/L) transiently increased cAMP levels and, therefore, channel current. Pretreatment with selective agonists to A(1) or A(3) adenosine receptors (ARs) that are G(i)-coupled markedly attenuated the response to isoproterenol, indicating inhibition of adenylyl cyclase by increased G(i) activity. Agonists to bradykinin or δ-opioid receptors also attenuated isoproterenol's response. A(2A)AR and A(2B)AR are G(s)-coupled. The A(2A)AR-selective agonist CGS21680 increased current through CNG channels but only in the presence of phosphodiesterase (PDE) inhibitors, indicating low surface receptor activity and high intracellular PDE activity. As we previously reported, BAY 60-6583, an A(2B)AR-selective agonist which mimics preconditioning's protection in rabbit heart, neither increased nor decreased membrane current in transfected cardiomyocytes, suggesting the absence or a markedly limited number of A(2B)AR in the sarcolemma. However, reverse transcription polymerase chain reaction (RT-PCR) of purified cardiomyocytes yielded an A(2B)AR band, implying that rabbit cardiomyocytes do indeed express A(2B)AR. These data reveal that all receptors reported to be involved in ischemic preconditioning do exist on or within the cardiomyocyte.
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Affiliation(s)
- Wenkuan Xin
- Department of Pharmacology, University of South Alabama College of Medicine, Mobile, AL 36688, USA
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92
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Xie M, Rich TC, Scheitrum C, Conti M, Richter W. Inactivation of multidrug resistance proteins disrupts both cellular extrusion and intracellular degradation of cAMP. Mol Pharmacol 2011; 80:281-93. [PMID: 21551375 DOI: 10.1124/mol.111.071134] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In addition to xenobiotics and several other endogenous metabolites, multidrug-resistance proteins (MRPs) extrude the second-messenger cAMP from various cells. Pharmacological and/or genetic inactivation of MRPs has been shown to augment intracellular cAMP signaling, an effect assumed to be a direct consequence of the blockade of cAMP extrusion. Here we provide evidence that the augmented intracellular cAMP levels are not due exclusively to the prevention of cAMP efflux because MRP inactivation is also associated with reduced cAMP degradation by phosphodiesterases (PDEs). Several prototypical MRP inhibitors block PDE activity at concentrations widely used to inhibit MRPs. Their dose-dependent effects in several paradigms of cAMP signaling are more consistent with their potency in inhibiting PDEs than MRPs. Moreover, genetic manipulation of MRP expression results in concomitant changes in PDE activity and protein levels, thus affecting cAMP degradation in parallel with cAMP efflux. These findings suggest that the effects of MRP inactivation on intracellular cAMP levels reported previously may be due in part to reduced degradation by PDEs and identify MRP-dependent transport mechanisms as novel regulators of cellular PDE expression levels. Mathematical simulations of cAMP signaling predict that selective ablation of MRP-dependent cAMP efflux per se does not affect bulk cytosolic cAMP levels, but may control cAMP levels in restricted submembrane compartments that are defined by small volume, high MRP activity, limited PDE activity, and limited exchange of cAMP with the bulk-cytosolic cAMP pool. Whether this regulation occurs in cells remains to be confirmed experimentally under conditions that do not affect PDE activity.
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Affiliation(s)
- Moses Xie
- Department of Gynecology, Obstetrics and Reproductive Sciences, University of California San Francisco, 513 Parnassus Ave., Box 0556, San Francisco, CA 94143-0556, USA
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93
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Protein kinase a in cancer. Cancers (Basel) 2011; 3:913-26. [PMID: 24212646 PMCID: PMC3756396 DOI: 10.3390/cancers3010913] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 02/09/2011] [Accepted: 02/22/2011] [Indexed: 01/07/2023] Open
Abstract
In the past, many chromosomal and genetic alterations have been examined as possible causes of cancer. However, some tumors do not display a clear molecular and/or genetic signature. Therefore, other cellular processes may be involved in carcinogenesis. Genetic alterations of proteins involved in signal transduction have been extensively studied, for example oncogenes, while modifications in intracellular compartmentalization of these molecules, or changes in the expression of unmodified genes have received less attention. Yet, epigenetic modulation of second messenger systems can deeply modify cellular functioning and in the end may cause instability of many processes, including cell mitosis. It is important to understand the functional meaning of modifications in second messenger intracellular pathways and unravel the role of downstream proteins in the initiation and growth of tumors. Within this framework, the cAMP system has been examined. cAMP is a second messenger involved in regulation of a variety of cellular functions. It acts mainly through its binding to cAMP-activated protein kinases (PKA), that were suggested to participate in the onset and progression of various tumors. PKA may represent a biomarker for tumor detection, identification and staging, and may be a potential target for pharmacological treatment of tumors.
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94
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Sayner SL. Emerging themes of cAMP regulation of the pulmonary endothelial barrier. Am J Physiol Lung Cell Mol Physiol 2011; 300:L667-78. [PMID: 21335524 DOI: 10.1152/ajplung.00433.2010] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The presence of excess fluid in the interstitium and air spaces of the lung presents severe restrictions to gas exchange. The pulmonary endothelial barrier regulates the flux of fluid and plasma proteins from the vascular space into the underlying tissue. The integrity of this endothelial barrier is dynamically regulated by transitions in cAMP (3',5'-cyclic adenosine monophosphate), which are synthesized in discrete subcellular compartments. Cyclic AMP generated in the subplasma membrane compartment acts through PKA and Epac (exchange protein directly activated by cAMP) to tighten cell adhesions, strengthen cortical actin, reduce actomyosin contraction, and decrease permeability. Confining cAMP within the subplasma membrane space is critical to its barrier-protective properties. When cAMP escapes the near membrane compartment and gains access to the cytosolic compartment, or when soluble adenylyl cyclases generate cAMP within the cytosolic compartment, this second messenger activates established cytosolic cAMP signaling cascades to perturb the endothelial barrier through PKA-mediated disruption of microtubules. Thus the concept of cAMP compartmentalization in endothelial barrier regulation is gaining momentum and new possibilities are being unveiled for cytosolic cAMP signaling with the emergence of the bicarbonate-regulated mammalian soluble adenylyl cyclase (sAC or AC10).
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Affiliation(s)
- Sarah L Sayner
- Dept. of Cell Biology and Neuroscience, Member, Center for Lung Biology, College of Medicine, Univ. of South Alabama, Mobile, AL 36688, USA.
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Blackman BE, Horner K, Heidmann J, Wang D, Richter W, Rich TC, Conti M. PDE4D and PDE4B function in distinct subcellular compartments in mouse embryonic fibroblasts. J Biol Chem 2011; 286:12590-601. [PMID: 21288894 PMCID: PMC3069460 DOI: 10.1074/jbc.m110.203604] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Signaling through cAMP regulates most cellular functions. The spatiotemporal control of cAMP is, therefore, crucial for differential regulation of specific cellular targets. Here we investigated the consequences of PDE4B or PDE4D gene ablation on cAMP signaling at a subcellular level using mouse embryonic fibroblasts. PDE4B ablation had no effect on the global or bulk cytosol accumulation of cAMP but increased both basal and hormone-dependent cAMP in a near-membrane pool. Conversely, PDE4D ablation enhanced agonist-induced cAMP accumulation in the bulk cytosol as well as at the plasma membrane. Both PDE4B and PDE4D ablation significantly modified the time course and the level of isoproterenol-induced phosphorylation of vasodilator-stimulated phosphoprotein, a membrane cytoskeletal component. A second membrane response through Toll-like receptor signaling, however, was only affected by PDE4B ablation. PDE4D but not PDE4B ablation significantly prolonged cAMP-response element-binding protein-mediated transcription. These findings demonstrate that PDE4D and PDE4B have specialized functions in mouse embryonic fibroblasts with PDE4B controlling cAMP in a discrete subdomain near the plasma membrane.
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Affiliation(s)
- Brigitte E Blackman
- Center for Reproductive Sciences, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California San Francisco School of Medicine, San Francisco, California 94143, USA
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96
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Abstract
Cyclic nucleotide phosphodiesterases (PDEs) are promising targets for pharmacological intervention. The presence of multiple PDE genes, diversity of the isoforms produced from each gene, selective tissue and cellular expression of the isoforms, compartmentation within cells, and an array of conformations of PDE proteins are some of the properties that challenge the development of drugs that target these enzymes. Nevertheless, many of the characteristics of PDEs are also viewed as unique opportunities to increase specificity and selectivity when designing novel compounds for certain therapeutic indications. This chapter provides a summary of the major concepts related to the design and use of PDE inhibitors. The overall structure and properties of the catalytic domain and conformations of PDEs are summarized in light of the most recent X-ray crystal structures. The distinctive properties of catalytic domains of different families as well as the technical challenges associated with probing PDE properties and their interactions with small molecules are discussed. The effect of posttranslational modifications and protein-protein interactions are additional factors to be considered when designing PDE inhibitors. PDE inhibitor interaction with other proteins needs to be taken into account and is also discussed.
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97
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Hochbaum D, Barila G, Ribeiro-Neto F, Altschuler DL. Radixin assembles cAMP effectors Epac and PKA into a functional cAMP compartment: role in cAMP-dependent cell proliferation. J Biol Chem 2010; 286:859-66. [PMID: 21047789 DOI: 10.1074/jbc.m110.163816] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
cAMP is an ubiquitous second messenger. Localized areas with high cAMP concentration, i.e. cAMP microdomains, provide an elegant mechanism to generate signaling specificity and transduction efficiency. However, the mechanisms underlying cAMP effector targeting into these compartments is still unclear. Here we report the identification of radixin as a scaffolding unit for both cAMP effectors, Epac and PKA. This complex localizes in a submembrane compartment where cAMP synthesis occurs. Compartment disruption by shRNA and dominant negative approaches negatively affects cAMP action. Inhibition can be rescued by expression of Rap1b, a substrate for both Epac1 and PKA, but only in its GTP-bound and phosphorylated state. We propose that radixin scaffolds both cAMP effectors in a functional cAMP-sensing compartment for efficient signal transduction, using Rap1 as a downstream signal integrator.
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Affiliation(s)
- Daniel Hochbaum
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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98
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Peercy BE, Sherman AS. How pancreatic beta-cells discriminate long and short timescale cAMP signals. Biophys J 2010; 99:398-406. [PMID: 20643057 DOI: 10.1016/j.bpj.2010.04.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 03/15/2010] [Accepted: 04/14/2010] [Indexed: 11/16/2022] Open
Abstract
The translocation of catalytic protein kinase A (cPKA) in response to cyclic-adenosine mono-phosphate (cAMP) depends on the pattern of stimulus applied to the cell. Experiments with IBMX have shown that 1), sustained cAMP elevation is more effective than oscillations of cAMP at getting cPKA into the nucleus; and 2), cPKA enters the nucleus by diffusion. We constructed mathematical models of cAMP activation of cPKA and their diffusion in order to study nuclear translocation of cPKA, and conclude that hindered diffusion of cPKA through the nuclear membrane by a rapid-binding process, but not globally reduced diffusion, can explain the experimental data. Perturbation analysis suggests that normal physiological oscillations of glucose would not result in nuclear translocation, but chronically high glucose that produces extended calcium plateaus and/or chronic glucagonlike peptide-1 stimulation could result in elevated levels of nuclear cPKA.
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Affiliation(s)
- Bradford E Peercy
- Department of Mathematics and Statistics, University of Maryland, Baltimore, Maryland, USA
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99
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The N terminus of phosphodiesterase TbrPDEB1 of Trypanosoma brucei contains the signal for integration into the flagellar skeleton. EUKARYOTIC CELL 2010; 9:1466-75. [PMID: 20693305 DOI: 10.1128/ec.00112-10] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The precise subcellular localization of the components of the cyclic AMP (cAMP) signaling pathways is a crucial aspect of eukaryotic intracellular signaling. In the human pathogen Trypanosoma brucei, the strict control of cAMP levels by cAMP-specific phosphodiesterases is essential for parasite survival, both in cell culture and in the infected host. Among the five cyclic nucleotide phosphodiesterases identified in this organism, two closely related isoenzymes, T. brucei PDEB1 (TbrPDEB1) (PDEB1) and TbrPDEB2 (PDEB2) are predominantly responsible for the maintenance of cAMP levels. Despite their close sequence similarity, they are distinctly localized in the cell. PDEB1 is mostly located in the flagellum, where it forms an integral part of the flagellar skeleton. PDEB2 is mainly located in the cell body, and only a minor part of the protein localizes to the flagellum. The current study, using transfection of procyclic trypanosomes with green fluorescent protein (GFP) reporters, demonstrates that the N termini of the two enzymes are essential for determining their final subcellular localization. The first 70 amino acids of PDEB1 are sufficient to specifically direct a GFP reporter to the flagellum and to lead to its detergent-resistant integration into the flagellar skeleton. In contrast, the analogous region of PDEB2 causes the GFP reporter to reside predominantly in the cell body. Mutagenesis of selected residues in the N-terminal region of PDEB2 demonstrated that single amino acid changes are sufficient to redirect the reporter from a cell body location to stable integration into the flagellar skeleton.
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100
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Oliveira RF, Terrin A, Di Benedetto G, Cannon RC, Koh W, Kim M, Zaccolo M, Blackwell KT. The role of type 4 phosphodiesterases in generating microdomains of cAMP: large scale stochastic simulations. PLoS One 2010; 5:e11725. [PMID: 20661441 PMCID: PMC2908681 DOI: 10.1371/journal.pone.0011725] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/17/2010] [Indexed: 11/29/2022] Open
Abstract
Cyclic AMP (cAMP) and its main effector Protein Kinase A (PKA) are critical for several aspects of neuronal function including synaptic plasticity. Specificity of synaptic plasticity requires that cAMP activates PKA in a highly localized manner despite the speed with which cAMP diffuses. Two mechanisms have been proposed to produce localized elevations in cAMP, known as microdomains: impeded diffusion, and high phosphodiesterase (PDE) activity. This paper investigates the mechanism of localized cAMP signaling using a computational model of the biochemical network in the HEK293 cell, which is a subset of pathways involved in PKA-dependent synaptic plasticity. This biochemical network includes cAMP production, PKA activation, and cAMP degradation by PDE activity. The model is implemented in NeuroRD: novel, computationally efficient, stochastic reaction-diffusion software, and is constrained by intracellular cAMP dynamics that were determined experimentally by real-time imaging using an Epac-based FRET sensor (H30). The model reproduces the high concentration cAMP microdomain in the submembrane region, distinct from the lower concentration of cAMP in the cytosol. Simulations further demonstrate that generation of the cAMP microdomain requires a pool of PDE4D anchored in the cytosol and also requires PKA-mediated phosphorylation of PDE4D which increases its activity. The microdomain does not require impeded diffusion of cAMP, confirming that barriers are not required for microdomains. The simulations reported here further demonstrate the utility of the new stochastic reaction-diffusion algorithm for exploring signaling pathways in spatially complex structures such as neurons.
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Affiliation(s)
- Rodrigo F. Oliveira
- The Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, United States of America
| | - Anna Terrin
- Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | | | | | - Wonryull Koh
- The Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, United States of America
| | - MyungSook Kim
- The Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, United States of America
| | - Manuela Zaccolo
- Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Kim T. Blackwell
- The Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, United States of America
- * E-mail:
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