401
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Hong CS, Kwon SJ, Cho MC, Kwak YG, Ha KC, Hong B, Li H, Chae SW, Chai OH, Song CH, Li Y, Kim JC, Woo SH, Lee SY, Lee CO, Kim DH. Overexpression of junctate induces cardiac hypertrophy and arrhythmia via altered calcium handling. J Mol Cell Cardiol 2008; 44:672-82. [PMID: 18353357 DOI: 10.1016/j.yjmcc.2008.01.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2007] [Revised: 01/15/2008] [Accepted: 01/29/2008] [Indexed: 12/14/2022]
Abstract
Junctate-1 is a newly identified integral endoplasmic/sarcoplasmic reticulum Ca2+ binding protein. However, its functional role in the heart is unknown. In the present study, the consequences of constitutively overexpressed junctate in cardiomyocytes were investigated using transgenic (TG) mice overexpressing junctate-1. TG mice (8 weeks old) showed cardiac remodeling such as marked bi-atrial enlargement with intra-atrial thrombus and biventricular hypertrophy. The TG mice also showed bradycardia with atrial fibrillation, reduced amplitude and elongated decay time of Ca2+ transients, increased L-type Ca2+ current and prolonged action potential durations. Time-course study (2-8 weeks) showed an initially reduced SR function due to down-regulation of SERCA2 and calsequestrin followed by sarcolemmal protein expression and cardiac hypertrophy at later age. These sequential changes could well be correlated with the physiological changes. Adrenergic agonist treatment and subsequent biochemical study showed that junctate-1 TG mice (8 weeks old) were under local PKA signaling that could cause increased L-type Ca2+ current and reduced SR function. Junctate-1 in the heart is closely linked to the homeostasis of E-C coupling proteins and a sustained increase of junctate-1 expression leads to a severe cardiac remodeling and arrhythmias.
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Affiliation(s)
- Chang-Soo Hong
- Department of Biological Science, College of Natural Sciences, Daegu University, Gyeongsan, South Korea
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402
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Spatiotemporal control of cAMP signalling processes by anchored signalling complexes. Biochem Soc Trans 2008; 35:931-7. [PMID: 17956249 DOI: 10.1042/bst0350931] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ligand-induced changes in cAMP concentration vary in duration, amplitude and extension into the cell. cAMP microdomains are shaped by adenylate cyclases that form cAMP as well as PDEs (phosphodiesterases) that degrade cAMP. Various extracellular signals converge on the cAMP/PKA (protein kinase A) pathway through ligand binding to GPCRs (G-protein-coupled receptors) and the cAMP/PKA pathway is therefore tightly regulated on several levels to maintain specificity in the multitude of signal inputs. AKAPs (A-kinase-anchoring proteins) target PKA to specific substrates and distinct subcellular compartments, providing spatial and temporal specificity for mediation of biological effects channelled through the cAMP/PKA pathway. AKAPs also serve as scaffolding proteins that assemble PKA together with signal terminators such as phosphoprotein phosphatases and cAMP-specific PDEs as well as components of other signalling pathways into multiprotein signalling complexes.
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403
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Borthwick LA, Riemen C, Goddard C, Colledge WH, Mehta A, Gerke V, Muimo R. Defective formation of PKA/CnA-dependent annexin 2-S100A10/CFTR complex in DeltaF508 cystic fibrosis cells. Cell Signal 2008; 20:1073-83. [PMID: 18346874 DOI: 10.1016/j.cellsig.2008.01.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 01/21/2008] [Accepted: 01/22/2008] [Indexed: 01/01/2023]
Abstract
Cystic fibrosis (CF) is characterised by impaired epithelial ion transport and is caused by mutations in the cystic fibrosis conductance regulator protein (CFTR), a cAMP/PKA and ATP-regulated chloride channel. We recently demonstrated a cAMP/PKA/calcineurin (CnA)-driven association between annexin 2 (anx 2), its cognate partner -S100A10 and cell surface CFTR. The complex is required for CFTR and outwardly rectifying chloride channel function in epithelia. Since the cAMP/PKA-induced Cl(-) current is absent in CF epithelia, we hypothesized that the anx 2-S100A10/CFTR complex may be defective in CFBE41o cells expressing the commonest F508del-CFTR (DeltaF-CFTR) mutation. Here, we demonstrate that, despite the presence of cell surface DeltaF-CFTR, cAMP/PKA fails to induce anx 2-S100A10/CFTR complex formation in CFBE41o- cells homozygous for F508del-CFTR. Mechanistically, PKA-dependent serine phosphorylation of CnA, CnA-anx 2 complex formation and CnA-dependent dephosphorylation of anx 2 are all defective in CFBE41o- cells. Immunohistochemical analysis confirms an abnormal cellular distribution of anx 2 in human and CF mouse epithelia. Thus, we demonstrate that cAMP/PKA/CnA signaling pathway is defective in CF cells and suggest that loss of anx 2-S100A10/CFTR complex formation may contribute to defective cAMP/PKA-dependent CFTR channel function.
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Affiliation(s)
- Lee Anthony Borthwick
- Academic Unit of Child Health, The University of Sheffield, Sheffield Children's, Hospital, Stephenson Wing, Sheffield, S10 2TH, UK
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404
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cAMP-specific phosphodiesterase-4D5 (PDE4D5) provides a paradigm for understanding the unique non-redundant roles that PDE4 isoforms play in shaping compartmentalized cAMP cell signalling. Biochem Soc Trans 2008; 35:938-41. [PMID: 17956250 DOI: 10.1042/bst0350938] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The PDE4 (phosphodiesterase-4) enzyme family consists of a distinct array of N-terminal splice variant isoforms arising from four subfamily genes (4A, 4B, 4C and 4D). These all hydrolyse specifically the intracellular second messenger cAMP. Although identical in catalytic function, each isoform appears to serve a non-superfluous regulatory role. For example, a beta-arrestin-sequestered subpopulation of the PDE4D5 isoform specifically regulates the phosphorylation of the beta(2)-AR (beta(2)-adrenergic receptor) by PKA (protein kinase A; also called cAMP-dependent protein kinase). This was elucidated by the use of novel technologies, including dominant-negative approaches, siRNA (small interfering RNA) knockdown and spot-immobilized peptide array analyses. Functional phenotypes uncovered using these methodologies have shown that beta-arrestin-sequestered PDE4D5 shapes the spatial cAMP gradient around the membrane-bound beta(2)-AR, regulating its phosphorylation by PKA and its ability to activate ERK (extracellular-signal-regulated kinase) through G(i) in cardiomyocytes and HEK-293 (human embryonic kidney)-B2 cells. This approach has provided the very first identification of a non-redundant and specific role for a PDE isoform. The fact that phenotypes can be uncovered by displacing PDE4 isoforms from specific anchor sites using dominant-negative constructs and cell-permeable peptides points to novel means for developing therapeutics aimed at disrupting specifically sequestered PDE isoforms and even specifically sequestered subpopulations of individual isoforms.
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405
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Hofer AM, Lefkimmiatis K. Extracellular calcium and cAMP: second messengers as "third messengers"? Physiology (Bethesda) 2008; 22:320-7. [PMID: 17928545 DOI: 10.1152/physiol.00019.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Calcium and cyclic AMP are familiar second messengers that typically become elevated inside cells on activation of cell surface receptors. This article will explore emerging evidence that transport of these signaling molecules across the plasma membrane allows them to be recycled as "third messengers," extending their ability to convey information in a domain outside the cell.
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Affiliation(s)
- Aldebaran M Hofer
- Department of Surgery, VA Boston Healthcare System and Brigham & Women's Hospital, Harvard Medical School, West Roxbury, Massachusetts, USA.
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406
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Jiang Y, Kumada T, Cameron DB, Komuro H. Cerebellar granule cell migration and the effects of alcohol. Dev Neurosci 2008; 30:7-23. [PMID: 18075250 DOI: 10.1159/000109847] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 01/04/2007] [Indexed: 01/30/2023] Open
Abstract
In the developing brain the majority of neurons migrate from their birthplace to their final destination. This active movement is essential for the formation of cortical layers and nuclei. The impairment of migration does not affect the viability of neurons but often results in abnormal differentiation. The proper migration of neurons requires the orchestrated activities of multiple cellular and molecular events, such as pathway selection, the activation of specific receptors and channels, and the assembly and disassembly of cytoskeletal components. The migration of neurons is very vulnerable to exposure to environmental toxins, such as alcohol. In this article, we will focus on recent developments in the migration of cerebellar granule cells. First, we will describe when, where and how granule cells migrate through different cortical layers to reach their final destination. Second, we will present how internal programs control the sequential changes in granule cell migration. Third, we will review the roles of external guidance cues and transmembrane signals in granule cell migration. Finally, we will reveal mechanisms by which alcohol exposure impairs granule cell migration.
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Affiliation(s)
- Yulan Jiang
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
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407
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Constantin S, Wray S. Gonadotropin-releasing hormone-1 neuronal activity is independent of cyclic nucleotide-gated channels. Endocrinology 2008; 149:279-90. [PMID: 17916627 PMCID: PMC2194613 DOI: 10.1210/en.2007-0955] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 09/26/2007] [Indexed: 12/18/2022]
Abstract
Pulsatile release of GnRH-1 is essential for secretion of gonadotropin hormones. The frequency of GnRH-1 pulses is regulated during the reproductive cycle by numerous neurotransmitters. Cyclic nucleotide-gated (CNG) channels have been proposed as a mechanism to integrate the cAMP signal evoked by many neurotransmitters. This study reports the expression of the CNGA2 subunit in GnRH-1 neurons obtained from mouse nasal explants and shows the ability of GnRH-1 neurons to increase their activity in response to forskolin (activator of adenylyl cyclases), or 3-isobutyl-1-methylxanthine (inhibitor of phosphodiesterases) even after removal of gamma-aminobutyric acid (A)-ergic input. Next, the endogenous activity of adenylyl cyclases was evaluated as a component of the oscillatory mechanism of GnRH-1 neurons. Inhibition of endogenous activity of adenylyl cyclases did not alter GnRH-1 activity. The potential involvement of CNGA2 subunit in basal or induced activity was tested on GnRH-1 neurons obtained from CNGA2-deficient mice. Without up-regulation of CNGA1 or CNGA3, the absence of functional CNGA2 did not alter either the endogenous GnRH-1 neuronal activity or the response to forskolin, negating CNG channels from cAMP-sensitive mechanisms leading to changes in GnRH-1 neuronal activity. In addition, the potential role of CNGA2 subunit in the synchronization of calcium oscillations previously described was evaluated in GnRH-1 neurons from CNGA2-deficient explants. Synchronized calcium oscillations persisted in CNGA2-deficient GnRH-1 neurons. Taken together, these results indicate that CNGA2 channels are not necessary for either the response of GnRH-1 neurons to cAMP increases or the basal rhythmic activity of GnRH-1 neurons.
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Affiliation(s)
- Stéphanie Constantin
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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408
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Holz GG, Chepurny OG, Schwede F. Epac-selective cAMP analogs: new tools with which to evaluate the signal transduction properties of cAMP-regulated guanine nucleotide exchange factors. Cell Signal 2008; 20:10-20. [PMID: 17716863 PMCID: PMC2215344 DOI: 10.1016/j.cellsig.2007.07.009] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/03/2007] [Accepted: 07/18/2007] [Indexed: 11/22/2022]
Abstract
The identification of 2'-O-methyl substituted adenosine-3',5'-cyclic monophosphate (cAMP) analogs that activate the Epac family of cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs, also known as Epac1 and Epac2), has ushered in a new era of cyclic nucleotide research in which previously unrecognized signalling properties of the second messenger cAMP have been revealed. These Epac-Selective Cyclic AMP Analogs (ESCAs) incorporate a 2'-O-methyl substitution on the ribose ring of cAMP, a modification that impairs their ability to activate protein kinase A (PKA), while leaving intact their ability to activate Epac (the Exchange Protein directly Activated by Cyclic AMP). One such ESCA in wide-spread use is 8-pCPT-2'-O-Me-cAMP. It is a cell-permeant derivative of 2'-O-Me-cAMP, and it is a super activator of Epac. A wealth of newly published studies demonstrate that 8-pCPT-2'-O-Me-cAMP is a unique tool with which to asses atypical actions of cAMP that are PKA-independent. Particularly intriguing are recent reports demonstrating that ESCAs reproduce the PKA-independent actions of ligands known to stimulate Class I (Family A) and Class II (Family B) GTP-binding protein-coupled receptors (GPCRs). This topical review summarizes the current state of knowledge regarding the molecular pharmacology and signal transduction properties of Epac-selective cAMP analogs. Special attention is focused on the rational drug design of ESCAs in order to improve their Epac selectivity, membrane permeability, and stability. Also emphasized is the usefulness of ESCAs as new tools with which to assess the role of Epac as a determinant of intracellular Ca2+ signalling, ion channel function, neurotransmitter release, and hormone secretion.
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Affiliation(s)
- George G Holz
- Department of Physiology and Neuroscience, New York University School of Medicine, New York, NY, USA.
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409
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Berrera M, Dodoni G, Monterisi S, Pertegato V, Zamparo I, Zaccolo M. A toolkit for real-time detection of cAMP: insights into compartmentalized signaling. Handb Exp Pharmacol 2008:285-98. [PMID: 18491057 DOI: 10.1007/978-3-540-72843-6_12] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The study of cAMP signaling has received a renewed impulse since the recognition that a key aspect of this pathway is the tight spatial control of signal propagation. The study of the mechanism that regulates cAMP signaling in space and time has prompted the development of new methodological approaches to detect cAMP in intact cells. Over the last decades, techniques to assess cAMP concentration with high spatial and temporal resolution in living cells have been elaborated that are based on fluorescent molecules and the phenomenon of fluorescence resonance energy transfer (FRET). A FRET-based indicator of cAMP concentration is typically a protein, including two fluorophores that are linked to a cAMP-binding domain. Binding of cAMP causes a change in the protein conformation and, as a consequence, in the distance between the fluorophores, thus altering the energy transfer between them. Several FRET indicators have been developed, differing in their affinity for cAMP, kinetic features and intracellular targeting. Such indicators enable the measurement of cAMP fluctuations as they happen in the complex intracellular environment and are proving to be effective tools to dissect compartmentalized cAMP signaling.
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Affiliation(s)
- M Berrera
- Dvn Biochemistry and Molecular Biology, IBLS, Wolfson Link Building, University Avenue, Glasgow, Scotland, UK
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410
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Juric DM, Loncar D, Carman-Krzan M. Noradrenergic stimulation of BDNF synthesis in astrocytes: Mediation via α1- and β1/β2-adrenergic receptors. Neurochem Int 2008; 52:297-306. [PMID: 17681645 DOI: 10.1016/j.neuint.2007.06.035] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Revised: 06/23/2007] [Accepted: 06/28/2007] [Indexed: 12/11/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) synthesis in astrocytes induced by noradrenaline (NA) is a receptor-mediated process utilizing two parallel adrenergic pathways: beta1/beta2-adrenergic/cAMP and the novel alpha1-adrenergic/PKC pathway. BDNF is produced by astrocytes, in addition to neurons, and the noradrenergic system plays a role in controlling BDNF synthesis. Since astrocytes express various subtypes of alpha- and beta-adrenergic receptors that have the potential to be activated by synaptically released NA, we focused our present study on the mediatory role of adrenergic receptors in the noradrenergic up-regulation of BDNF synthesis in cultured neonatal rat cortical astrocytes. NA (1 microM) elevates BDNF levels by four-fold after 6 h of incubation. Its stimulation was partly inhibited by either the beta1-adrenergic antagonist atenolol, the beta2-adrenergic antagonist ICI 118,551, or by the alpha1-adrenergic antagonist prazosin, while the alpha2-adrenergic antagonist yohimbine showed no effect. BDNF levels in astrocytes were increased by the specific beta1-adrenergic agonist dobutamine and the beta2-adrenergic agonist salbutamol, as well as by adenylate cyclase activation (by forskolin) and PKA activation (by dBcAMP). However, none of the tested agonists or mediators of the intracellular beta-adrenergic pathways were able to reach the level of NA's stimulatory effect. BDNF cellular levels were also elevated by the alpha1-adrenergic agonist methoxamine, but not by the alpha2-adrenergic agonist clonidine. The increase in intracellular Ca2+ by ionophore A23187 showed no effect, whereas PKC activation by phorbol 12-myristate 13-acetate (TPA) potently stimulated BDNF levels in the cells. The methoxamine-stimulated BDNF synthesis was inhibited by desensitizing pretreatment with TPA, indicating that the alpha1-stimulation was mediated via PKC activation. In conclusion, the synthesis of astrocytic BDNF stimulated by noradrenergic neuronal activity is an adaptable process using multiple types (alpha1 and beta1/beta2) of adrenergic receptor activation.
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Affiliation(s)
- Damijana Mojca Juric
- Department of Pharmacology and Experimental Toxicology, Faculty of Medicine, University of Ljubljana, Korytkova 2, Ljubljana SI-1000, Slovenia.
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411
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Torgersen KM, Aandahl EM, Taskén K. Molecular architecture of signal complexes regulating immune cell function. Handb Exp Pharmacol 2008:327-63. [PMID: 18491059 DOI: 10.1007/978-3-540-72843-6_14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Signals transmitted via multichain immunoreceptors control the development, differentiation and activation of hematopoetic cells. The cytoplasmic parts of these receptors contain immunoreceptor tyrosine-based activation motifs (ITAMs) that upon phosphorylation by members of the Src tyrosine kinase family orchestrate a complex set of signaling events involving tyrosine phosphorylation, generation of second messengers like DAG, IP3 and Ca2+, activation of effector molecules like Ras and MAPKs and the translocation and activation of transcription factors like NFAT, API and NF-kB. Spatial and temporal organization of these signaling events is essential both to connect the receptors to downstream cascades as well as to control the functional outcome of the immune activation. Throughout this process control and fine-tuning of the different signals are necessary both for effective immune function and in order to avoid inappropriate or exaggerated immune activation and autoimmunity. This control includes modulating mechanisms that set the threshold for activation and reset the activation status after an immune response has been launched. One immunomodulating pathway is the cAMP-protein kinase A-Csk pathway scaffolded by a supramolecular complex residing in lipid rafts with the A kinase-anchoring protein (AKAP) ezrin, the Csk-binding protein PAG and a linker between the two, EBP50. Failure of correct scaffolding and loss of spatiotemporal control can potentially have severe consequences, leading to immune failure or autoimmunity. The clinical relevance of supramolecular complexes specifically organized by scaffolding proteins in regulating immune activity and the specter of genetic diseases linked to different signaling components suggest that protein-protein contact surfaces can be potential targets for drug intervention. It is also of interest to note that different pathogens have evolved strategies to specifically modulate signal integration, thereby rewiring the signal in a way beneficial for their survival. In addition to demonstrating the importance of different signal processes, these adaptations are elegant illustrations of the potential for drug targeting of protein assembly. This chapter reviews some of the important scaffolding events downstream of immunoreceptors with focus on signaling transduction through the T-cell receptor (TCR).
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Affiliation(s)
- K M Torgersen
- The Biotechnology Centre of Oslo, Gaustadalléen 21, PO Box 1125 Blindern, Oslo, Norway
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412
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Abstract
A-kinase-anchoring proteins (AKAPs) are a diverse family of about 50 scaffolding proteins. They are defined by the presence of a structurally conserved protein kinase A (PKA)-binding domain. AKAPs tether PKA and other signalling proteins such as further protein kinases, protein phosphatases and phosphodiesterases by direct protein-protein interactions to cellular compartments. Thus, AKAPs form the basis of signalling modules that integrate cellular signalling processes and limit these to defined sites. Disruption of AKAP functions by gene targeting, knockdown approaches and, in particular, pharmacological disruption of defined AKAP-dependent protein-protein interactions has revealed key roles of AKAPs in numerous processes, including the regulation of cardiac myocyte contractility and vasopressin-mediated water reabsorption in the kidney. Dysregulation of such processes causes diseases, including cardiovascular and renal disorders. In this review, we discuss AKAP functions elucidated by gene targeting and knockdown approaches, but mainly focus on studies utilizing peptides for disruption of direct AKAP-mediated protein-protein interactions. The latter studies point to direct AKAP-mediated protein-protein interactions as targets for novel drugs.
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413
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Smith KJ, Baillie GS, Hyde EI, Li X, Houslay TM, McCahill A, Dunlop AJ, Bolger GB, Klussmann E, Adams DR, Houslay MD. 1H NMR structural and functional characterisation of a cAMP-specific phosphodiesterase-4D5 (PDE4D5) N-terminal region peptide that disrupts PDE4D5 interaction with the signalling scaffold proteins, beta-arrestin and RACK1. Cell Signal 2007; 19:2612-24. [PMID: 17900862 DOI: 10.1016/j.cellsig.2007.08.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 08/26/2007] [Indexed: 01/29/2023]
Abstract
The unique 88 amino acid N-terminal region of cAMP-specific phosphodiesterase-4D5 (PDE4D5) contains overlapping binding sites conferring interaction with the signaling scaffold proteins, betaarrestin and RACK1. A 38-mer peptide, whose sequence reflected residues 12 through 49 of PDE4D5, encompasses the entire N-terminal RACK1 Interaction Domain (RAID1) together with a portion of the beta-arrestin binding site. (1)H NMR and CD analyses indicate that this region has propensity to form a helical structure. The leucine-rich hydrophobic grouping essential for RACK1 interaction forms a discrete hydrophobic ridge located along a single face of an amphipathic alpha-helix with Arg34 and Asn36, which also play important roles in RACK1 binding. The Asn22/Pro23/Trp24/Asn26 grouping, essential for RACK1 interaction, was located at the N-terminal head of the amphipathic helix that contained the hydrophobic ridge. RAID1 is thus provided by a distinct amphipathic helical structure. We suggest that the binding of PDE4D5 to the WD-repeat protein, RACK1, may occur in a manner akin to the helix-helix interaction shown for G(gamma) binding to the WD-repeat protein, G(beta). A more extensive section of the PDE4D5 N-terminal sequence (Thr11-Ala85) is involved in beta-arrestin binding. Several residues within the RAID1 helix contribute to this interaction however. We show here that these residues form a focused band around the centre of the RAID1 helix, generating a hydrophobic patch (from Leu29, Val30 and Leu33) flanked by polar/charged residues (Asn26, Glu27, Asp28, Arg34). The interaction with beta-arrestin exploits a greater circumference on the RAID1 helix, and involves two residues (Glu27, Asp28) that do not contribute to RACK1 binding. In contrast, the interaction of RACK1 with RAID1 is extended over a greater length of the helix and includes Leu37/Leu38, which do not contribute to beta-arrestin binding. A membrane-permeable, stearoylated Val12-Ser49 38-mer peptide disrupted the interaction of both beta-arrestin and RACK1 with endogenous PDE4D5 in HEKB2 cells, whilst a cognate peptide with a Glu27Ala substitution selectively failed to disrupt PDE4D5/RACK1 interaction. The stearoylated Val12-Ser49 38-mer peptide enhanced the isoprenaline-stimulated PKA phosphorylation of the beta(2)-adrenergic receptors (beta(2)AR) and its activation of ERK, whilst the Glu27Ala peptide was ineffective in both these regards.
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MESH Headings
- Adrenergic beta-2 Receptor Agonists
- Adrenergic beta-Agonists/pharmacology
- Amino Acid Sequence
- Arrestins/chemistry
- Arrestins/metabolism
- Binding Sites
- Cell Line
- Circular Dichroism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 3
- Cyclic Nucleotide Phosphodiesterases, Type 4
- Epithelial Cells/drug effects
- Epithelial Cells/enzymology
- Epithelial Cells/metabolism
- GTP-Binding Proteins/chemistry
- GTP-Binding Proteins/metabolism
- Humans
- Hydrophobic and Hydrophilic Interactions
- Isoproterenol/pharmacology
- Models, Molecular
- Molecular Sequence Data
- Neoplasm Proteins/chemistry
- Neoplasm Proteins/metabolism
- Nuclear Magnetic Resonance, Biomolecular
- Peptides/pharmacology
- Phosphoric Diester Hydrolases/chemistry
- Phosphoric Diester Hydrolases/metabolism
- Phosphorylation
- Protein Binding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors for Activated C Kinase
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/metabolism
- Signal Transduction
- beta-Arrestins
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Affiliation(s)
- K John Smith
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, PO Box 363, B15 2TT, UK
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414
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Ruppelt A, Mosenden R, Grönholm M, Aandahl EM, Tobin D, Carlson CR, Abrahamsen H, Herberg FW, Carpén O, Taskén K. Inhibition of T cell activation by cyclic adenosine 5'-monophosphate requires lipid raft targeting of protein kinase A type I by the A-kinase anchoring protein ezrin. THE JOURNAL OF IMMUNOLOGY 2007; 179:5159-68. [PMID: 17911601 DOI: 10.4049/jimmunol.179.8.5159] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
cAMP negatively regulates T cell immune responses by activation of type I protein kinase A (PKA), which in turn phosphorylates and activates C-terminal Src kinase (Csk) in T cell lipid rafts. Using yeast two-hybrid screening, far-Western blot, immunoprecipitation and immunofluorescense analyses, and small interfering RNA-mediated knockdown, we identified Ezrin as the A-kinase anchoring protein that targets PKA type I to lipid rafts. Furthermore, Ezrin brings PKA in proximity to its downstream substrate Csk in lipid rafts by forming a multiprotein complex consisting of PKA/Ezrin/Ezrin-binding protein 50, Csk, and Csk-binding protein/phosphoprotein associated with glycosphingolipid-enriched microdomains. The complex is initially present in immunological synapses when T cells contact APCs and subsequently exits to the distal pole. Introduction of an anchoring disruptor peptide (Ht31) into T cells competes with Ezrin binding to PKA and thereby releases the cAMP/PKA type I-mediated inhibition of T cell proliferation. Finally, small interfering RNA-mediated knockdown of Ezrin abrogates cAMP regulation of IL-2. We propose that Ezrin is essential in the assembly of the cAMP-mediated regulatory pathway that modulates T cell immune responses.
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Affiliation(s)
- Anja Ruppelt
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
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415
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Baragli A, Grieco ML, Trieu P, Villeneuve LR, Hébert TE. Heterodimers of adenylyl cyclases 2 and 5 show enhanced functional responses in the presence of Galpha s. Cell Signal 2007; 20:480-92. [PMID: 18164588 DOI: 10.1016/j.cellsig.2007.10.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 10/30/2007] [Indexed: 12/22/2022]
Abstract
Recent studies have demonstrated that adenylyl cyclase isoforms can form both homo- and heterodimers and that this may be the basic functional unit of these enzymes (see Cooper, D.M.F. and Crossthwaite, A.J. (2006) Trends. Pharmacol. Sci. 8:426-431). Here, we show that adenylyl cyclases 2 and 5 can form a functional heterodimeric complex in HEK293 cells using a combination of BRET, confocal imaging, co-immunoprecipitation and assays of adenylyl cyclase activity. The AC2/5 complex is formed constitutively and is stable in the presence of receptor or forskolin stimulation. The complex formed by AC2/5 is also much more sensitive to the presence of Galpha(s) and forskolin than either of the parent AC isoforms themselves. Finally, we also show that this complex can be detected in native tissues as AC2 and AC5 were localized to the same structures in adult mouse ventricular myocytes and neonatal mouse cardiac fibroblasts and could be co-immunoprecipitated from lysates of mouse heart.
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Affiliation(s)
- Alessandra Baragli
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Quebec, Canada
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416
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Goehring AS, Pedroja BS, Hinke SA, Langeberg LK, Scott JD. MyRIP anchors protein kinase A to the exocyst complex. J Biol Chem 2007; 282:33155-67. [PMID: 17827149 PMCID: PMC3508720 DOI: 10.1074/jbc.m705167200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The movement of signal transduction enzymes in and out of multi-protein complexes coordinates the spatial and temporal resolution of cellular events. Anchoring and scaffolding proteins are key to this process because they sequester protein kinases and phosphatases with a subset of their preferred substrates. The protein kinase A-anchoring family of proteins (AKAPs), which target the cAMP-dependent protein kinase (PKA) and other enzymes to defined subcellular microenvironments, represent a well studied group of these signal-organizing molecules. In this report we demonstrate that the Rab27a GTPase effector protein MyRIP is a member of the AKAP family. The zebrafish homolog of MyRIP (Ze-AKAP2) was initially detected in a two-hybrid screen for AKAPs. A combination of biochemical, cell-based, and immunofluorescence approaches demonstrate that the mouse MyRIP ortholog targets the type II PKA holoenzyme via an atypical mechanism to a specific perinuclear region of insulin-secreting cells. Similar approaches show that MyRIP interacts with the Sec6 and Sec8 components of the exocyst complex, an evolutionarily conserved protein unit that controls protein trafficking and exocytosis. These data indicate that MyRIP functions as a scaffolding protein that links PKA to components of the exocytosis machinery.
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Affiliation(s)
- April S. Goehring
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Benjamin S. Pedroja
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Simon A. Hinke
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Lorene K. Langeberg
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - John D. Scott
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
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417
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Andreeva AV, Kutuzov MA, Voyno-Yasenetskaya TA. Scaffolding proteins in G-protein signaling. J Mol Signal 2007; 2:13. [PMID: 17971232 PMCID: PMC2211295 DOI: 10.1186/1750-2187-2-13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 10/30/2007] [Indexed: 11/18/2022] Open
Abstract
Heterotrimeric G proteins are ubiquitous signaling partners of seven transmembrane-domain G-protein-coupled receptors (GPCRs), the largest (and most important pharmacologically) receptor family in mammals. A number of scaffolding proteins have been identified that regulate various facets of GPCR signaling. In this review, we summarize current knowledge concerning those scaffolding proteins that are known to directly bind heterotrimeric G proteins, and discuss the composition of the protein complexes they assemble and their effects on signal transduction. Emerging evidence about possible ways of regulation of activity of these scaffolding proteins is also discussed.
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Affiliation(s)
- Alexandra V Andreeva
- Department of Pharmacology, College of Medicine, University of Illinois at Chicago, 909 S, Wolcott Ave, Chicago, Illinois 60612, USA.
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418
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Compartmentalized cAMP signalling in regulated exocytic processes in non-neuronal cells. Cell Signal 2007; 20:590-601. [PMID: 18061403 DOI: 10.1016/j.cellsig.2007.10.020] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 10/16/2007] [Indexed: 01/04/2023]
Abstract
Cyclic adenosine monophosphate (cAMP) is a central second messenger controlling a plethora of vital functions. Studies of cAMP dynamics in living cells have revealed markedly inhomogeneous concentrations of the second messenger in different compartments. Moreover, cAMP effectors such as cAMP-dependent protein kinase (PKA) and cAMP-activated GTP-exchange factors (Epacs) are tethered to specific cellular sites. Both the tailoring of cAMP concentrations, and the activities of cAMP-dependent signalling systems at specific cellular locations are prerequisites for most, if not all, cAMP-dependent processes. This review focuses on the role of compartmentalized cAMP signalling in exocytic processes in non-neuronal cells. Particularly, the insertion of aquaporin-2 into the plasma membrane of renal principal cells as an example for a cAMP-dependent exocytic process in a non-secretory cell type, renin secretion from juxtaglomerular cells as a cAMP-triggered exocytosis from an endocrine cell, insulin release from pancreatic beta-cells as a Ca2+-mediated and cAMP-potentiated exocytic processes in an endocrine cell, and cAMP- or Ca2+ -triggered H+ secretion from gastric parietal cells as an exocytic process in an exocrine cell are discussed. The selected examples of cAMP-regulated exocytic pathways are reviewed with regard to key proteins involved: adenylyl cyclases, phosphodiesterases, PKA, A kinase anchoring proteins (AKAPs) and Epacs.
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419
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Amidi F, Beall M, Ross MG. Cyclic adenosine monophosphate regulation of aquaporin gene expression in human amnion epithelia. Reprod Sci 2007; 14:234-40. [PMID: 17636236 DOI: 10.1177/1933719107300970] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cell membrane aquaporins (AQPs) may con t r i b u t e importantly to the regulation of intramembranous absorption of amniotic fluid. Recently, the authors demonstrated that human amnion AQP3 expression is upregulated by second-messenger cyclic adenosine monophosphate (cAMP). The present study was undertaken to determine the cAMP regulation of other AQP types, specifically AQP1, 8, and 9, in human amnion epithelia in vitro. Human amnion epithelial cell cultures were prepared from amnion of normal-term pregnancy. To investigate the effect of cAMP on AQP expression, primary human amnion cell cultures were incubated for 2, 10, and 20 hours with culture medium containing either 50 microM forskolin, an adenylate cyclase activator that stimulates cellular production of cAMP, or 100 microM SP-cAMP, a cAMP agonist that stimulates protein kinase A. Total RNA was isolated from the cultured cells, and semiquantitative real-time reverse transcription polymerase chain reaction was carried out to determine the relative level of AQPs mRNA expression. In primary amnion epithelial cell culture, AQP1 mRNA expression increased significantly at 10 hours (0.219 +/- 0.006 to 0.314 +/- 0.008, P < .05) and remained elevated for 20 hours (0.223 +/- 0.004 to 0.323 +/- 0.012, P < .05) following forskolin treatment. AQP8 mRNA expression increased significantly at 2 hours (0.069 +/- 0.003 to 0.086 +/- 0.012, P < .05) and remained upregulated for 20 hours following forskolin treatment. Forskolin stimulation of AQP9 mRNA expression was evidenced by 10 hours (0.098 +/- 0.005 to 0.115 +/- 0.006, P < .05) and maintained for 20 hours. In contrast to forskolin, SP-cAMP incubation resulted in no change in AQP1, 8, or 9 mRNA expression. Human amnion epithelial cell AQP1, 8, and 9 mRNA expression is upregulated by cAMP as their expression is simulated by forskolin. Lack of effect of SP-cAMP, the protein kinase A activator, on AQP1, 8, and 9 mRNA expression suggests that cAMP upregulates human amnion AQP1, 8, and 9 mRNA expression via the protein kinase A independent pathway.
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420
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Lygren B, Carlson CR, Santamaria K, Lissandron V, McSorley T, Litzenberg J, Lorenz D, Wiesner B, Rosenthal W, Zaccolo M, Taskén K, Klussmann E. AKAP complex regulates Ca2+ re-uptake into heart sarcoplasmic reticulum. EMBO Rep 2007; 8:1061-7. [PMID: 17901878 PMCID: PMC2247390 DOI: 10.1038/sj.embor.7401081] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Revised: 08/06/2007] [Accepted: 08/28/2007] [Indexed: 01/20/2023] Open
Abstract
The beta-adrenergic receptor/cyclic AMP/protein kinase A (PKA) signalling pathway regulates heart rate and contractility. Here, we identified a supramolecular complex consisting of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2), its negative regulator phospholamban (PLN), the A-kinase anchoring protein AKAP18delta and PKA. We show that AKAP18delta acts as a scaffold that coordinates PKA phosphorylation of PLN and the adrenergic effect on Ca(2+) re-uptake. Inhibition of the compartmentalization of this cAMP signalling complex by specific molecular disruptors interferes with the phosphorylation of PLN. This prevents the subsequent release of PLN from SERCA2, thereby affecting the Ca(2+) re-uptake into the sarcoplasmic reticulum induced by adrenergic stimuli.
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Affiliation(s)
- Birgitte Lygren
- Biotechnology Centre of Oslo, University of Oslo, PO Box 1125, Blindern, N-0317 Oslo, Norway
| | - Cathrine Rein Carlson
- Biotechnology Centre of Oslo, University of Oslo, PO Box 1125, Blindern, N-0317 Oslo, Norway
| | - Katja Santamaria
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
| | - Valentina Lissandron
- Dulbecco Telethon Institute, Venetian Institute of Molecular Medicine, I-35124 Padova, Italy
| | - Theresa McSorley
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
| | - Jessica Litzenberg
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
| | - Dorothea Lorenz
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
| | - Burkhard Wiesner
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
| | - Walter Rosenthal
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
- Institut für Pharmakologie, Charité—Universitätsmedizin Berlin, Freie Universität Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
| | - Manuela Zaccolo
- Dulbecco Telethon Institute, Venetian Institute of Molecular Medicine, I-35124 Padova, Italy
| | - Kjetil Taskén
- Biotechnology Centre of Oslo, University of Oslo, PO Box 1125, Blindern, N-0317 Oslo, Norway
- Tel: +47 22840505/0549; Fax: +47 22840506; E-mail:
| | - Enno Klussmann
- Leibniz-Institut fûr Molekulare Pharmakologie (FMP), D-13125 Berlin, Germany
- Institut für Pharmakologie, Charité—Universitätsmedizin Berlin, Freie Universität Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
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421
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Murdoch H, Mackie S, Collins DM, Hill EV, Bolger GB, Klussmann E, Porteous DJ, Millar JK, Houslay MD. Isoform-selective susceptibility of DISC1/phosphodiesterase-4 complexes to dissociation by elevated intracellular cAMP levels. J Neurosci 2007; 27:9513-24. [PMID: 17728464 PMCID: PMC6673124 DOI: 10.1523/jneurosci.1493-07.2007] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Disrupted-in-schizophrenia 1 (DISC1) is a genetic susceptibility factor for schizophrenia and related severe psychiatric conditions. DISC1 is a multifunctional scaffold protein that is able to interact with several proteins, including the independently identified schizophrenia risk factor phosphodiesterase-4B (PDE4B). Here we report that the 100 kDa full-length DISC1 isoform (fl-DISC1) can bind members of each of the four gene, cAMP-specific PDE4 family. Elevation of intracellular cAMP levels, so as to activate protein kinase A, caused the release of PDE4D3 and PDE4C2 isoforms from fl-DISC1 while not affecting binding of PDE4B1 and PDE4A5 isoforms. Using a peptide array strategy, we show that PDE4D3 binds fl-DISC1 through two regions found in common with PDE4B isoforms, the interaction of which is supplemented because of the presence of additional PDE4B-specific binding sites. We propose that the additional binding sites found in PDE4B1 underpin its resistance to release during cAMP elevation. We identify, for the first time, a functional distinction between the 100 kDa long DISC1 isoform and the short 71 kDa isoform. Thus, changes in the expression pattern of DISC1 and PDE4 isoforms offers a means to reprogram their interaction and to determine whether the PDE4 sequestered by DISC1 is released after cAMP elevation. The PDE4B-specific binding sites encompass point mutations in mouse Disc1 that confer phenotypes related to schizophrenia and depression and that affect binding to PDE4B. Thus, genetic variation in DISC1 and PDE4 that influence either isoform expression or docking site functioning may directly affect psychopathology.
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Affiliation(s)
- Hannah Murdoch
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Shaun Mackie
- Medical Genetics Section, Molecular Medicine Centre, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Daniel M. Collins
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Elaine V. Hill
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Graeme B. Bolger
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35294-3300
| | - Enno Klussmann
- Leibniz-Institut für Molekulare Pharmakologie, Campus Berlin-Buch, 13125 Berlin, Germany, and
| | - David J. Porteous
- Medical Genetics Section, Molecular Medicine Centre, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - J. Kirsty Millar
- Medical Genetics Section, Molecular Medicine Centre, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Miles D. Houslay
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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422
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Ocampo J, Moreno S, Rossi S. PKA from Mucor circinelloides: model to study the role of linker I in the interaction between R and C subunits. Biochem Biophys Res Commun 2007; 362:721-6. [PMID: 17761146 DOI: 10.1016/j.bbrc.2007.08.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 08/10/2007] [Indexed: 01/14/2023]
Abstract
Protein kinase A from the fungus Mucor circinelloides shows high affinity interaction between regulatory (R) and catalytic (C) subunits. Its R subunit shows a differential presence of several acidic residues in linker I region, in the amino terminus. Mutants R1, lacking the N-terminal region, and R2, lacking the acidic cluster, were used to analyze its effect on the interaction with the C subunit, assessed through inhibition of catalytic activity and cAMP activation of reconstituted holoenzyme. A similar decrease in the interaction was obtained when using R1 and R2 with the homologous C subunit; however when using heterologous bovine C, only R1 had a decreased interaction. The results show the general importance of linker I region in the R-C interaction in protein kinases A and point to the importance of the acidic cluster present in the N-terminus of M. circinelloides R subunit in the high affinity interaction between R and C in this holoenzyme.
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Affiliation(s)
- Josefina Ocampo
- Departamento de Química Biológica, Facultad de Ciencias Exactas y, Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, 1428 Buenos Aires, Argentina
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423
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Abstract
PURPOSE OF REVIEW Aquaporin-2 is an aquaporin water channel protein present at the apical membrane of kidney collecting duct cells and plays a key role in urine concentrating ability. Like other membrane proteins, aquaporin-2 undergoes dynamic processes within the cells: synthesized, targeted to the subapical region, exocytosed to the apical membrane, endocytosed, recycled and finally degraded. The understanding of the molecular and cellular mechanisms of these events is advancing rapidly, and recent new findings characterizing such processes are reviewed. RECENT FINDINGS Hypertonicity itself stimulates aquaporin-2 expression through the tonicity-responsive enhancer and its transcription factors. Gene targeted mouse models for human nephrogenic diabetes insipidus show the importance of the C-terminus of aquaporin-2 in apical sorting and provide mechanistic insights. Evidence for the importance of actin cytoskelton in exocytosis of aquaporin-2 to the apical membrane is accumulating. Actin and other proteins bind to aquaporin-2 and make a multiprotein complex. New proteomic analyses indicate the involvement of a large series of proteins in aquaporin-2 dynamics. SUMMARY The protein-level understanding of aquaporin-2 dynamics has advanced considerably over the past few years, and continuing studies will open a new way in developing new manoeuvres or drugs to manipulate kidney water homeostasis.
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Affiliation(s)
- Sei Sasaki
- Department of Nephrology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
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424
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Ceccarini M, Grasso M, Veroni C, Gambara G, Artegiani B, Macchia G, Ramoni C, Torreri P, Mallozzi C, Petrucci TC, Macioce P. Association of Dystrobrevin and Regulatory Subunit of Protein Kinase A: A New Role for Dystrobrevin as a Scaffold for Signaling Proteins. J Mol Biol 2007; 371:1174-87. [PMID: 17610895 DOI: 10.1016/j.jmb.2007.06.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 06/06/2007] [Accepted: 06/07/2007] [Indexed: 11/15/2022]
Abstract
The dystrophin-related and -associated protein dystrobrevin is a component of the dystrophin-associated protein complex, which directly links the cytoskeleton to the extracellular matrix. It is now thought that this complex also serves as a dynamic scaffold for signaling proteins, and dystrobrevin may play a role in this context. Since dystrobrevin involvement in signaling pathways seems to be dependent on its interaction with other proteins, we sought new insights and performed a two-hybrid screen of a mouse brain cDNA library using beta-dystrobrevin, the isoform expressed in non-muscle tissues, as bait. Among the positive clones characterized after the screen, one encodes the regulatory subunit RIalpha of the cAMP-dependent protein kinase A (PKA). We confirmed the interaction by in vitro and in vivo association assays, and mapped the binding site of beta-dystrobrevin on RIalpha to the amino-terminal region encompassing the dimerization/docking domain of PKA regulatory subunit. We also found that the domain of interaction for RIalpha is contained in the amino-terminal region of beta-dystrobrevin. We obtained evidence that beta-dystrobrevin also interacts directly with RIIbeta, and that not only beta-dystrobrevin but also alpha-dystrobrevin interacts with PKA regulatory subunits. We show that both alpha and beta-dystrobrevin are specific phosphorylation substrates for PKA and that protein phosphatase 2A (PP2A) is associated with dystrobrevins. Our results suggest a new role for dystrobrevin as a scaffold protein that may play a role in different cellular processes involving PKA signaling.
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Affiliation(s)
- Marina Ceccarini
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, 00161 Roma, Italy
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425
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Lissandron V, Rossetto MG, Erbguth K, Fiala A, Daga A, Zaccolo M. Transgenic fruit-flies expressing a FRET-based sensor for in vivo imaging of cAMP dynamics. Cell Signal 2007; 19:2296-303. [PMID: 17689927 DOI: 10.1016/j.cellsig.2007.07.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Accepted: 07/02/2007] [Indexed: 01/23/2023]
Abstract
3'-5'-cyclic adenosine monophosphate (cAMP) is a ubiquitous intracellular second messenger that mediates the action of various hormones and neurotransmitters and influences a plethora of cellular functions. In particular, multiple neuronal processes such as synaptic plasticity underlying learning and memory are dependent on cAMP signalling cascades. It is now well recognized that the specificity and fidelity of cAMP downstream effects are achieved through a tight temporal as well as spatial control of the cAMP signals. Approaches relying on real-time imaging and Fluorescence Resonance Energy Transfer (FRET)-based biosensors for direct visualization of cAMP changes as they happen in intact living cells have recently started to uncover the fine details of cAMP spatio-temporal signalling patterns. Here we report the generation of transgenic fruit-flies expressing a FRET-based, GFP-PKA sensor and their use in real-time optical recordings of cAMP signalling both ex vivo and in vivo in adult and developing organisms. These transgenic animals represent a novel tool for understanding the physiology of the cAMP signalling pathway in the context of a functioning body.
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Affiliation(s)
- Valentina Lissandron
- Dulbecco Telethon Institute at the Venetian Institute of Molecular Medicine, via Orus 2, Padova, Italy
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426
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Willoughby D, Cooper DMF. Organization and Ca2+Regulation of Adenylyl Cyclases in cAMP Microdomains. Physiol Rev 2007; 87:965-1010. [PMID: 17615394 DOI: 10.1152/physrev.00049.2006] [Citation(s) in RCA: 327] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The adenylyl cyclases are variously regulated by G protein subunits, a number of serine/threonine and tyrosine protein kinases, and Ca2+. In some physiological situations, this regulation can be readily incorporated into a hormonal cascade, controlling processes such as cardiac contractility or neurotransmitter release. However, the significance of some modes of regulation is obscure and is likely only to be apparent in explicit cellular contexts (or stages of the cell cycle). The regulation of many of the ACs by the ubiquitous second messenger Ca2+provides an overarching mechanism for integrating the activities of these two major signaling systems. Elaborate devices have been evolved to ensure that this interaction occurs, to guarantee the fidelity of the interaction, and to insulate the microenvironment in which it occurs. Subcellular targeting, as well as a variety of scaffolding devices, is used to promote interaction of the ACs with specific signaling proteins and regulatory factors to generate privileged domains for cAMP signaling. A direct consequence of this organization is that cAMP will exhibit distinct kinetics in discrete cellular domains. A variety of means are now available to study cAMP in these domains and to dissect their components in real time in live cells. These topics are explored within the present review.
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Affiliation(s)
- Debbie Willoughby
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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427
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O'Mahony F, Alzamora R, Betts V, LaPaix F, Carter D, Irnaten M, Harvey BJ. Female gender-specific inhibition of KCNQ1 channels and chloride secretion by 17beta-estradiol in rat distal colonic crypts. J Biol Chem 2007; 282:24563-73. [PMID: 17556370 DOI: 10.1074/jbc.m611682200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The estrogen sex steroid 17beta-estradiol rapidly inhibits secretagogue-stimulated cAMP-dependent Cl(-) secretion in the female rat distal colonic crypt by the inhibition of basolateral K(+) channels. In Ussing chamber studies, both the anti-secretory response and inhibition of basolateral K(+) current was shown to be attenuated by pretreatment with rottlerin, a PKCdelta-specific inhibitor. In whole cell patch-clamp analysis, 17beta-estradiol inhibited a chromanol 293B-sensitive KCNQ1 channel current in isolated female rat distal colonic crypts. Estrogen had no effect on KCNQ1 channel currents in colonic crypts isolated from male rats. Female distal colonic crypts expressed a significantly higher amount of PKCdelta in comparison to male tissue. PKCdelta and PKA were activated at 5 min in response to 17beta-estradiol in female distal colonic crypts only. Both PKCdelta- and PKA-associated with the KCNQ1 channel in response to 17beta-estradiol in female distal colonic crypts, and no associations were observed in crypts from males. PKA activation, association with KCNQ1, and phosphorylation of the channel were regulated by PKCdelta as the responses were blocked by pretreatment with rottlerin. Taken together, our experiments have identified the molecular targets underlying the anti-secretory response to estrogen involving the inhibition of KCNQ1 channel activity via PKCdelta- and PKA-dependent signaling pathways. This is a novel gender-specific mechanism of regulation of an ion channel by estrogen. The anti-secretory response described in this study provides molecular insights whereby estrogen causes fluid retention effects in the female during periods of high circulating plasma estrogen levels.
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Affiliation(s)
- Fiona O'Mahony
- Department of Molecular Medicine, Beaumont Hospital, Royal College of Surgeons in Ireland, Dublin 9, Ireland.
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428
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Iejima D, Sumita Y, Kagami H, Ando Y, Ueda M. Odontoblast marker gene expression is enhanced by a CC-chemokine family protein MIP-3alpha in human mesenchymal stem cells. Arch Oral Biol 2007; 52:924-31. [PMID: 17532291 DOI: 10.1016/j.archoralbio.2007.04.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 04/05/2007] [Accepted: 04/06/2007] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Macrophage inflammatory protein-3 alpha (MIP-3alpha) is a major CC-chemokine family protein, which serves as a differentiation factor for mesenchymal cells, including osteoblasts and dental pulp cells. The purpose of this study was to investigate the influence of MIP-3alpha on human mesenchymal stem cell differentiation in vitro. DESIGN Human mesenchymal stem cells were maintained in Dulbecco's modified Eagle's medium in the presence or absence of MIP-3alpha and the presence or absence of osteogenic factors (dexamethasone, beta-glycerophoshate and ascorbic acid). Alkaline phosphatase (ALP) activity was measured, and expression of odontoblast and osteoblast markers were examined by RT-PCR and Western blotting. RESULTS MIP-3alpha alone did not increase ALP activity, as compared to controls. The combination of MIP-3alpha and osteogenic factors increased ALP activity beyond increases observed with osteogenic factors alone. mRNA expression of the odontoblast marker dspp was only detectable when MIP-3alpha was added together with osteogenic factors at day 7 in three out of four samples. DSP protein level was increased only in the samples treated with both MIP-3alpha and osteogenic factors until day 5. In contrast, MIP-3alpha did not influence levels of the osteoblast markers CBFA1 or BSP. CONCLUSIONS The present study demonstrated that MIP-3alpha enhanced gene expression and protein levels of odontoblast-related genes, without affecting levels of the osteogenic proteins CBFA1 or BSP.
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Affiliation(s)
- D Iejima
- Research and Development Center, Hitachi Medical Corporation, Kashiwa, Chiba 277-0804, Japan
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429
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Cheung YF, Kan Z, Garrett-Engele P, Gall I, Murdoch H, Baillie GS, Camargo LM, Johnson JM, Houslay MD, Castle JC. PDE4B5, a Novel, Super-Short, Brain-Specific cAMP Phosphodiesterase-4 Variant Whose Isoform-Specifying N-Terminal Region Is Identical to That of cAMP Phosphodiesterase-4D6 (PDE4D6). J Pharmacol Exp Ther 2007; 322:600-9. [PMID: 17519386 DOI: 10.1124/jpet.107.122218] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The cAMP-specific phosphodiesterase-4 (PDE4) gene family is the target of several potential selective therapeutic inhibitors. The four PDE4 genes generate several distinct protein-coding isoforms through the use of alternative promoters and 5'-coding exons. Using mouse transcripts, we identified a novel, super-short isoform of human PDE4B encoding a novel 5' terminus, which we label PDE4B5. The protein-coding region of the novel 5' exon is conserved across vertebrates, chicken, zebrafish, and fugu. Reverse-transcription-polymerase chain reaction (PCR) and quantitative (PCR) measurements show that this isoform is brain-specific. The novel protein is 58 +/- 2 kDa; it has cAMP hydrolyzing enzymatic activity and is inhibited by PDE4-selective inhibitors rolipram and cilomilast (Ariflo). Confocal and subcellular fractionation analyses show that it is distributed predominantly and unevenly within the cytosol. The 16 novel N-terminal residues of PDE4B5 are identical to the 16 N-terminal residues of the super-short isoform of PDE4D (PDE4D6), which is also brain-specific. PDE4B5 is able to bind the scaffold protein DISC1, whose gene has been linked to schizophrenia. Microarray expression profiling of the PDE4 gene family shows that specific PDE4 genes are enriched in muscle and blood fractions; however, only by monitoring the individual isoforms is the brain specificity of the super-short PDE4D and PDE4B isoforms revealed. Understanding the distinct tissue specificity of PDE4 isoforms will be important for understanding phosphodiesterase biology and opportunities for therapeutic intervention.
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Affiliation(s)
- York-Fong Cheung
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
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430
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Baillie G, Adams D, Bhari N, Houslay T, Vadrevu S, Meng D, Li X, Dunlop A, Milligan G, Bolger G, Klussmann E, Houslay M. Mapping binding sites for the PDE4D5 cAMP-specific phosphodiesterase to the N- and C-domains of beta-arrestin using spot-immobilized peptide arrays. Biochem J 2007; 404:71-80. [PMID: 17288540 PMCID: PMC1868836 DOI: 10.1042/bj20070005] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Revised: 02/05/2007] [Accepted: 02/08/2007] [Indexed: 12/16/2022]
Abstract
Beta2-ARs (beta2-adrenoceptors) become desensitized rapidly upon recruitment of cytosolic beta-arrestin. PDE4D5 (family 4 cAMP-specific phosphodiesterase, subfamily D, isoform 5) can be recruited in complex with beta-arrestin, whereupon it regulates PKA (cAMP-dependent protein kinase) phosphorylation of the beta2-AR. In the present study, we have used novel technology, employing a library of overlapping peptides (25-mers) immobilized on cellulose membranes that scan the entire sequence of beta-arrestin 2, to define the interaction sites on beta-arrestin 2 for binding of PDE4D5 and the cognate long isoform, PDE4D3. We have identified a binding site in the beta-arrestin 2 N-domain for the common PDE4D catalytic unit and two regions in the beta-arrestin 2 C-domain that confer specificity for PDE4D5 binding. Alanine-scanning peptide array analysis of the N-domain binding region identified severely reduced interaction with PDE4D5 upon R26A substitution, and reduced interaction upon either K18A or T20A substitution. Similar analysis of the beta-arrestin 2 C-domain identified Arg286 and Asp291, together with the Leu215-His220 region, as being important for binding PDE4D5, but not PDE4D3. Transfection with wild-type beta-arrestin 2 profoundly decreased isoprenaline-stimulated PKA phosphorylation of the beta2-AR in MEFs (mouse embryo fibroblasts) lacking both beta-arrestin 1 and beta-arrestin 2. This effect was negated using either the R26A or the R286A mutant form of beta-arrestin 2 or a mutant with substitution of an alanine cassette for Leu215-His220, which showed little or no PDE4D5 binding, but was still recruited to the beta2-AR upon isoprenaline challenge. These data show that the interaction of PDE4D5 with both the N- and C-domains of beta-arrestin 2 are essential for beta2-AR regulation.
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Key Words
- β2-adrenoceptor
- β-arrestin
- camp
- desensitization
- peptide array
- phosphodiesterase 4 (pde4)
- akap79, a-kinase-anchoring protein 79
- β2-ar, β2-adrenoceptor
- erk, extracellular-signal-regulated kinase
- gfp, green fluorescent protein
- gpcr, g-protein-coupled receptor
- grk, gpcr kinase
- gst, glutathione s-transferase
- hek-293, human embryonic kidney
- mef, mouse embryonic fibroblast
- pde, phosphodiesterase
- pka, camp-dependent protein kinase
- sirna, small interfering rna
- vsv, vesicular-stomatitis virus
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Affiliation(s)
- George S. Baillie
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - David R. Adams
- †Department of Chemistry, Heriot-Watt University, Riccarton Campus, Edinburgh EH14 4AS, Scotland, U.K
| | - Narinder Bhari
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Thomas M. Houslay
- ‡Bioinformatics Research Centre, Davidson Building, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Suryakiran Vadrevu
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Dong Meng
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Xiang Li
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Allan Dunlop
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Graeme Milligan
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Graeme B. Bolger
- §Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294-3300, U.S.A
| | - Enno Klussmann
- ∥Leibniz-Institut für Molekulare Pharmakologie (FMP), Campus Berlin-Buch, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Miles D. Houslay
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
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431
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Kalamidas SA, Kuehnel MP, Peyron P, Rybin V, Rauch S, Kotoulas OB, Houslay M, Hemmings BA, Gutierrez MG, Anes E, Griffiths G. cAMP synthesis and degradation by phagosomes regulate actin assembly and fusion events: consequences for mycobacteria. J Cell Sci 2007; 119:3686-94. [PMID: 16931599 DOI: 10.1242/jcs.03091] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
We showed recently that actin assembly by phagosomal membranes facilitates fusion with late endocytic organelles in macrophages. Moreover, lipids that induced phagosomal actin also stimulated this fusion process. In macrophages infected with pathogenic mycobacteria actin-stimulatory lipids led to an increase in pathogen destruction, whereas inhibitors facilitated their growth. A model was proposed whereby phagosomal membrane actin assembly provides tracks for lysosomes to move towards phagosomes, thereby facilitating fusion. Here, we investigated how cAMP affected phagosomal actin assembly in vitro, and phagosomal actin, acidification and late fusion events in J774 macrophages. Latex bead phagosomes are shown to possess adenylyl cyclase activity, which synthesizes cAMP, and phosphodiesterase activity, which degrades cAMP. The system is regulated by protein kinase A (PKA). Increasing cAMP levels inhibited, whereas decreasing cAMP levels stimulated, actin assembly in vitro and within cells. Increasing cAMP levels also inhibited phagosome-lysosome fusion and acidification in cells, whereas reducing cAMP had the opposite effect. High cAMP levels induced an increase in intraphagosomal growth in macrophages of both the non-pathogenic Mycobacterium smegmatis and the pathogenic Mycobacterium tuberculosis, whereas low cAMP levels or inhibition of PKA correlated with increased bacterial destruction. We argue that the phagosome cAMP-PKA system behaves as a molecular switch that regulates phagosome actin and maturation in macrophages.
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432
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Abstract
Maternal alcohol consumption during pregnancy can cause serious birth defects, of which fetal alcohol syndrome (FAS) is the most devastating. Recognized by characteristic craniofacial abnormalities and growth deficiency, this condition produces severe alcohol-induced damage in the developing brain. FAS children experience ataxia; deficits in intellectual functioning; and difficulties in learning, memory, problem solving, and attention. Multiple aspects of central nervous system development can be affected by alcohol exposure, but the most striking abnormalities are neuronal and glial migration. Little is known about cellular mechanisms by which alcohol affects the migration of immature neurons. Recently, it has been found that Ca(2+) signaling and cyclic nucleotide signaling are the central targets of the action of alcohol in neuronal cell migration. Most importantly, the aberrant migration of immature neurons caused by alcohol exposure is significantly ameliorated by controlling the activity of these second-messenger pathways. In this Mini-Review, we first describe how alcohol exposure impairs the migration of cerebellar granule cells and then discuss the signaling mechanisms involved.
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Affiliation(s)
- Tatsuro Kumada
- Department of Neurosciences, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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433
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Han J, Han L, Tiwari P, Wen Z, Zheng JQ. Spatial targeting of type II protein kinase A to filopodia mediates the regulation of growth cone guidance by cAMP. ACTA ACUST UNITED AC 2007; 176:101-11. [PMID: 17200417 PMCID: PMC2063631 DOI: 10.1083/jcb.200607128] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The second messenger cyclic adenosine monophosphate (cAMP) plays a pivotal role in axonal growth and guidance, but its downstream mechanisms remain elusive. In this study, we report that type II protein kinase A (PKA) is highly enriched in growth cone filopodia, and this spatial localization enables the coupling of cAMP signaling to its specific effectors to regulate guidance responses. Disrupting the localization of PKA to filopodia impairs cAMP-mediated growth cone attraction and prevents the switching of repulsive responses to attraction by elevated cAMP. Our data further show that PKA targets protein phosphatase-1 (PP1) through the phosphorylation of a regulatory protein inhibitor-1 (I-1) to promote growth cone attraction. Finally, we find that I-1 and PP1 mediate growth cone repulsion induced by myelin-associated glycoprotein. These findings demonstrate that the spatial localization of type II PKA to growth cone filopodia plays an important role in the regulation of growth cone motility and guidance by cAMP.
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Affiliation(s)
- Jianzhong Han
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA
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434
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Reynolds JG, McCalmon SA, Tomczyk T, Naya FJ. Identification and mapping of protein kinase A binding sites in the costameric protein myospryn. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:891-902. [PMID: 17499862 PMCID: PMC1955755 DOI: 10.1016/j.bbamcr.2007.04.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 03/30/2007] [Accepted: 04/05/2007] [Indexed: 01/08/2023]
Abstract
Recently we identified a novel target gene of MEF2A named myospryn that encodes a large, muscle-specific, costamere-restricted alpha-actinin binding protein. Myospryn belongs to the tripartite motif (TRIM) superfamily of proteins and was independently identified as a dysbindin-interacting protein. Dysbindin is associated with alpha-dystrobrevin, a component of the dystrophin-glycoprotein complex (DGC) in muscle. Apart from these initial findings little else is known regarding the potential function of myospryn in striated muscle. Here we reveal that myospryn is an anchoring protein for protein kinase A (PKA) (or AKAP) whose closest homolog is AKAP12, also known as gravin/AKAP250/SSeCKS. We demonstrate that myospryn co-localizes with RII alpha, a type II regulatory subunit of PKA, at the peripheral Z-disc/costameric region in striated muscle. Myospryn interacts with RII alpha and this scaffolding function has been evolutionarily conserved as the zebrafish ortholog also interacts with PKA. Moreover, myospryn serves as a substrate for PKA. These findings point to localized PKA signaling at the muscle costamere.
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Affiliation(s)
- Joseph G Reynolds
- Department of Biology, Program in Cell and Molecular Biology, Boston University, 24 Cummington Street, Boston, MA 02215, USA
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435
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Abstract
Cyclic AMP regulates a vast number of distinct events in all cells. Early studies established that its hydrolysis by cyclic nucleotide phosphodiesterases (PDEs) controlled both the magnitude and the duration of its influence. Recent evidence shows that PDEs also act as coincident detectors linking cyclic-nucleotide- and non-cyclic-nucleotide-based cellular signaling processes and are tethered with great selectively to defined intracellular structures, thereby integrating and spatially restricting their cellular effects in time and space. Although 11 distinct families of PDEs have been defined, and cells invariably express numerous individual PDE enzymes, a large measure of our increased appreciation of the roles of these enzymes in regulating cyclic nucleotide signaling has come from studies on the PDE4 family. Four PDE4 genes encode more than 20 isoforms. Alternative mRNA splicing and the use of different promoters allows cells the possibility of expressing numerous PDE4 enzymes, each with unique amino-terminal-targeting and/or regulatory sequences. Dominant negative and small interfering RNA-mediated knockdown strategies have proven that particular isoforms can uniquely control specific cellular functions. Thus the protein kinase A phosphorylation status of the beta(2) adrenoceptor and, thereby, its ability to switch its signaling to extracellular signal-regulated kinase activation, is uniquely regulated by PDE4D5 in cardiomyocytes. We describe how cardiomyocytes and vascular smooth muscle cells selectively vary both the expression and the catalytic activities of PDE4 isoforms to regulate their various functions and how altered regulation of these processes can influence the development, or resolution, of cardiovascular pathologies, such as heart failure, as well as various vasculopathies.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/chemistry
- 3',5'-Cyclic-AMP Phosphodiesterases/metabolism
- A Kinase Anchor Proteins
- Adaptor Proteins, Signal Transducing/metabolism
- Animals
- Arrestins/metabolism
- Cardiovascular System/enzymology
- Cardiovascular System/metabolism
- Cyclic AMP/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 4
- Humans
- Isoenzymes/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/enzymology
- Myocytes, Cardiac/enzymology
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/physiology
- Ryanodine Receptor Calcium Release Channel/metabolism
- Signal Transduction
- Vasoconstriction
- beta-Arrestins
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Affiliation(s)
- Miles D Houslay
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
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436
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Levallet G, Levallet J, Bonnamy PJ. Alterations in proteoglycan synthesis selectively impair FSH-induced particulate cAMP-phosphodiesterase 4 (PDE4) activation in immature rat Sertoli cells. Biochim Biophys Acta Gen Subj 2007; 1770:638-48. [PMID: 17261351 DOI: 10.1016/j.bbagen.2006.12.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Revised: 12/11/2006] [Accepted: 12/15/2006] [Indexed: 01/24/2023]
Abstract
FSH-induced upregulation of cAMP-PDE4 activities was decreased in cultured Sertoli cells when alteration of cell proteoglycans (PGs) metabolism was simultaneously induced either by para-nitrophenyl beta-d-xyloside (PNPX) or by sodium chlorate. This effect was restricted to the particulate PDE4 activities and its timing was consistent with the half-life of Sertoli cell PGs. It did not result from alterations in Pde4d variants expression, the major FSH-regulated PDE4 in Sertoli cells. Moreover, lack of changes in the particulate levels of major immunoreactive 75 kDa and 90 kDa PDE4D proteins, corresponding likely to short PDE4D1 and long PDE4D3/D8/D9 isoforms respectively, suggested that the decrease in FSH-stimulated of PDE4 activities in chlorate- and PNPX-treated cells at the end of the 24-h incubation period resulted from the increased reversal of the activated particulate PDE4(D) activities back to unstimulated levels. By controlling FSH-stimulated particulate PDE4 inactivation through a still unknown mechanism (sustained activation of PKA or reduction of phosphoprotein phosphatase activities), cell PGs could be involved in the alteration of cAMP response to FSH accompanying the transition of Sertoli cells from proliferative to non-proliferative differentiated state.
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Affiliation(s)
- Guénaëlle Levallet
- Laboratoire Oestrogènes et Reproduction, EA 2608, INRA USC 2006, Université de Caen, 14032 Caen, France
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437
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Erdogan S, Aslantas O, Celik S, Atik E. The effects of increased cAMP content on inflammation, oxidative stress and PDE4 transcripts during Brucella melitensis infection. Res Vet Sci 2007; 84:18-25. [PMID: 17397885 DOI: 10.1016/j.rvsc.2007.02.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 01/16/2007] [Accepted: 02/06/2007] [Indexed: 01/19/2023]
Abstract
Cyclic AMP (cAMP) is a key intracellular second messenger which at increased levels has been shown to have anti-inflammatory and tissue-protective effects. Its concentration is determined by the activities of both adenylate cyclase (AC) and the phosphodiesterase (PDE) enzymes. The aim of this study was to compare the effects of increased cAMP and glucocorticoid dexamethasone administration on B. melitensis-induced lipid peroxidation, Brucella suppressed antioxidant enzyme activities and PDE4 transcripts in rats. Intracellular cyclic AMP level was elevated by two different approaches; activation of AC and inhibition of PDE activities. Rats were inoculated with B. melitensis for seven days then a single dose of nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX), the adenylate cyclase activator forskolin and dexamethasone were administrated to each infected group, and animals were challenged for 48 h. Brucella-induced lipid peroxidation was significantly reduced by the cAMP elevating agents as well as dexamethasone administration in plasma, liver and spleen. The antioxidant enzymes glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities were significantly decreased by the pathogen. Whilst suppressed GSH-Px activity was reversed by cAMP elevating agents, SOD activity was not restored. Superoxide generating enzyme xanthine oxidase activity was not altered at the end of the infection period. Brucella infection increased plasma IL-12 level and this effect was also suppressed by the cAMP elevating agents, whereas TNF-alpha, IFN-gamma and IL-10 levels were unchanged. Intracellular cAMP levels are entirely hydrolyzed by cAMP-specific PDE 4 isozymes (PDE4s) in inflammatory and immunocompetent cells. Brucella reduced mRNA transcript levels for PDE4A by 40%, though PDE4B and 4D transcriptions were being unaffected in spleen. It was concluded that B. melitensis infection decreased activity of the antioxidant defence system, induced lipid peroxidation and suppressed PDE4A transcription. Administration of cAMP elevating agents exhibited similar affect with dexamethasone on lipid peroxidation, IL-12 production and antioxidant enzyme activities in Brucella infection.
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Affiliation(s)
- Suat Erdogan
- Department of Biochemistry, Faculty of Veterinary Medicine, Mustafa Kemal University, Hatay 31034, Turkey.
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438
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Sastry KSR, Karpova Y, Prokopovich S, Smith AJ, Essau B, Gersappe A, Carson JP, Weber MJ, Register TC, Chen YQ, Penn RB, Kulik G. Epinephrine protects cancer cells from apoptosis via activation of cAMP-dependent protein kinase and BAD phosphorylation. J Biol Chem 2007; 282:14094-100. [PMID: 17353197 DOI: 10.1074/jbc.m611370200] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The stress hormone epinephrine is known to elicit multiple systemic effects that include changes in cardiovascular parameters and immune responses. However, information about its direct action on cancer cells is limited. Here we provide evidence that epinephrine reduces sensitivity of cancer cells to apoptosis through interaction with beta(2)-adrenergic receptors. The antiapoptotic mechanism of epinephrine primarily involves phosphorylation and inactivation of the proapoptotic protein BAD by cAMP-dependent protein kinase. Moreover, BAD phosphorylation was observed at epinephrine concentrations found after acute and chronic psychosocial stress. Antiapoptotic signaling by epinephrine could be one of the mechanisms by which stress promotes tumorigenesis and decreases the efficacy of anti-cancer therapies.
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Affiliation(s)
- Konduru S R Sastry
- Department of Cancer Biology, Section on Comparative Medicine, and Center for Human Genomics, Wake Forest University School of Medicine, Winston Salem, NC 27157, USA
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439
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Doyle ME, Egan JM. Mechanisms of action of glucagon-like peptide 1 in the pancreas. Pharmacol Ther 2007; 113:546-93. [PMID: 17306374 PMCID: PMC1934514 DOI: 10.1016/j.pharmthera.2006.11.007] [Citation(s) in RCA: 478] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Accepted: 11/27/2006] [Indexed: 12/13/2022]
Abstract
Glucagon-like peptide 1 (GLP-1) is a hormone that is encoded in the proglucagon gene. It is mainly produced in enteroendocrine L cells of the gut and is secreted into the blood stream when food containing fat, protein hydrolysate, and/or glucose enters the duodenum. Its particular effects on insulin and glucagon secretion have generated a flurry of research activity over the past 20 years culminating in a naturally occurring GLP-1 receptor (GLP-1R) agonist, exendin 4 (Ex-4), now being used to treat type 2 diabetes mellitus (T2DM). GLP-1 engages a specific guanine nucleotide-binding protein (G-protein) coupled receptor (GPCR) that is present in tissues other than the pancreas (brain, kidney, lung, heart, and major blood vessels). The most widely studied cell activated by GLP-1 is the insulin-secreting beta cell where its defining action is augmentation of glucose-induced insulin secretion. Upon GLP-1R activation, adenylyl cyclase (AC) is activated and cAMP is generated, leading, in turn, to cAMP-dependent activation of second messenger pathways, such as the protein kinase A (PKA) and Epac pathways. As well as short-term effects of enhancing glucose-induced insulin secretion, continuous GLP-1R activation also increases insulin synthesis, beta cell proliferation, and neogenesis. Although these latter effects cannot be currently monitored in humans, there are substantial improvements in glucose tolerance and increases in both first phase and plateau phase insulin secretory responses in T2DM patients treated with Ex-4. This review will focus on the effects resulting from GLP-1R activation in the pancreas.
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Affiliation(s)
- Máire E Doyle
- Department of Pathology, Immunology & Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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440
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Moeenrezakhanlou A, Nandan D, Shephard L, Reiner NE. 1alpha,25-dihydroxycholecalciferol activates binding of CREB to a CRE site in the CD14 promoter and drives promoter activity in a phosphatidylinositol-3 kinase-dependent manner. J Leukoc Biol 2007; 81:1311-21. [PMID: 17327484 DOI: 10.1189/jlb.1106681] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
1,25-dihydroxycholecalciferol, also known as 1alpha,25-dihydroxyvitamin D3 or calcitriol, regulates the differentiation and functional properties of mononuclear phagocytes. Many of these effects involve nongenomic signaling pathways, which are not fully understood. Activation of CD14 expression, a monocyte differentiation marker and coreceptor with TLR-2 for bacterial LPS, by calcitriol was shown previously to be PI-3K-dependent [1]; however, the mechanism of gene activation remained undefined. Using a transcription factor-binding array screen coupled with EMSA, we found evidence for PI-3K-dependent activation of CREB in THP-1 cells incubated with calcitriol. Furthermore, analysis of the proximal promoter of human CD14 identified regions that contained up to seven sequences, which showed significant similarity to a canonical CRE sequence, 5'-TGACGTCA-3'. Treatment of THP-1 cells with calcitriol activated CREB binding to one of these regions at Positions -37 to -55, relative to the transcription start site in a PI-3K-dependent manner. This 19-mer region also became transcriptionally active in a reporter assay in response to calcitriol, again dependent on PI-3K. Mutation of the CRE within the 19-mer abolished this activity. Taken together, these results show that calcitriol signaling, leading to activation of the CD14 promoter, involves CREB activation downstream of PI-3K.
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Affiliation(s)
- Alireza Moeenrezakhanlou
- Department of Medicine, University of British Columbia, Rm. 452D, 2733 Heather St., Vancouver, BC, Canada, V5Z 3J5
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441
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Beene DL, Scott JD. A-kinase anchoring proteins take shape. Curr Opin Cell Biol 2007; 19:192-8. [PMID: 17317140 PMCID: PMC3521038 DOI: 10.1016/j.ceb.2007.02.011] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Accepted: 02/09/2007] [Indexed: 01/18/2023]
Abstract
A-kinase anchoring proteins (AKAPs) are signaling scaffolds that contribute to various aspects of cAMP signaling. They do this by tethering protein kinase-A to specific subcellular sites, thereby focusing its activity toward relevant substrates. Recently the structural basis for these protein-protein interactions has been elucidated by x-ray crystallography. Recent reports have identified AKAPs that bind to adenylyl cyclases to regulate cAMP synthesis and that sequester phosphodiesterases to break down this second messenger locally. Another emerging aspect of AKAP function is their role in integrating cAMP signaling with other signaling pathways. For example, molecular and genetic approaches have been used to show that the neuronal anchoring protein WAVE1 integrates signaling from PKA and Cdk5 to regulate actin polymerization and cytoskeletal events.
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Affiliation(s)
- Darren L Beene
- Howard Hughes Medical Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA
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442
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Kassuya CAL, Ferreira J, Claudino RF, Calixto JB. Intraplantar PGE2 causes nociceptive behaviour and mechanical allodynia: the role of prostanoid E receptors and protein kinases. Br J Pharmacol 2007; 150:727-37. [PMID: 17310141 PMCID: PMC2013868 DOI: 10.1038/sj.bjp.0707149] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Receptor subtypes involved in PGE(2)-induced nociception are still controversial. The present study investigated the prostanoid E receptor (EP) subtypes and the protein kinase (PK) pathways involved in the nociception induced by PGE(2) injection in the mouse paw. EXPERIMENTAL APPROACH Paw-licking and mechanical allodynia were measured in vivo and protein kinase activation ex vivo by Western blots of extracts of paw skin. KEY RESULTS Intraplantar (i.pl.) injection of PGE(2) into the mouse paw caused nociceptive behaviour of short duration with mean ED(50) of 1.43 nmol. PGE(2) produced a longer-lasting mechanical allodynia, with an ED(50) of 0.05 nmol. Intraplantar injection of antagonists at EP(3) or EP(4), but not at EP(1) or EP(2) receptors inhibited PGE(2)-induced paw-licking. Paw-licking caused by PGE(2) was blocked by an inhibitor of PKA but only partially decreased by inhibition of the extracellular-regulated kinase (ERK). Selective inhibitors of PKC, c-Jun N-terminal kinase (JNK) or p38, all failed to affect PGE(2)-induced paw-licking. An EP(3) antagonist inhibited PGE(2)-induced mechanical allodynia. However, inhibitors of PKA, PKC or ERK, but not p38 or JNK, also partially inhibited PGE(2)-induced mechanical allodynia. Western blot analyses confirmed that i.pl. injection of PGE(2) activated PKA, PKCalpha, and mitogen activated kinases (MAPKs) in the paw. Co-treatment with EP(3) or EP(4) receptor antagonists reduced PGE(2)-induced PKA and ERK, but not PKCalpha activation. CONCLUSIONS AND IMPLICATIONS The present results indicate that the nociceptive behaviour and mechanical allodynia caused by i.pl. PGE(2) are mediated through activation of distinct EP receptors and PK-dependent mechanisms.
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Affiliation(s)
- C A L Kassuya
- Department of Pharmacology, Universidade Federal de Santa Catarina Florianópolis, Santa Catarina, Brazil
| | - J Ferreira
- Department of Chemistry, Universidade Federal de Santa Maria Santa Maria, Rio Grande do Sul, Brazil
| | - R F Claudino
- Department of Pharmacology, Universidade Federal de Santa Catarina Florianópolis, Santa Catarina, Brazil
| | - J B Calixto
- Department of Pharmacology, Universidade Federal de Santa Catarina Florianópolis, Santa Catarina, Brazil
- Author for correspondence:
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443
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Ster J, De Bock F, Guérineau NC, Janossy A, Barrère-Lemaire S, Bos JL, Bockaert J, Fagni L. Exchange protein activated by cAMP (Epac) mediates cAMP activation of p38 MAPK and modulation of Ca2+-dependent K+ channels in cerebellar neurons. Proc Natl Acad Sci U S A 2007; 104:2519-24. [PMID: 17284589 PMCID: PMC1892910 DOI: 10.1073/pnas.0611031104] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The exchange factor directly activated by cAMP (Epac) is a newly discovered direct target for cAMP and a guanine-nucleotide exchange factor for the small GTPase Rap. Little is known about the neuronal functions of Epac. Here we show that activation of Epac by specific cAMP analogs or by the pituitary adenylate cyclase-activating polypeptide induces a potent activation of the Ca2+-sensitive big K+ channel, slight membrane hyperpolarization, and increased after-hyperpolarization in cultured cerebellar granule cells. These effects involve activation of Rap and p38 MAPK, which mobilizes intracellular Ca2+ stores. These findings reveal a cAMP Epac-dependent and protein kinase A-independent signaling cascade that controls neuronal excitability.
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Affiliation(s)
- Jeanne Ster
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
| | - Frédéric De Bock
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
| | - Nathalie C. Guérineau
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
| | - Andrea Janossy
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
| | - Stéphanie Barrère-Lemaire
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
| | - Johannes L. Bos
- Department of Physiological Chemistry and Centre for Biochemical Genetics, University Medical Centre Utrecht Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
| | - Joël Bockaert
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
| | - Laurent Fagni
- *Institute of Functional Genomics, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 5203, Institute National de la Santé et de la Recherche Médicale U661, Universités Montpellier I et II, 34095 Montpellier, France; and
- To whom correspondence should be addressed. E-mail:
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444
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Janciauskiene SM, Nita IM, Stevens T. Alpha1-antitrypsin, old dog, new tricks. Alpha1-antitrypsin exerts in vitro anti-inflammatory activity in human monocytes by elevating cAMP. J Biol Chem 2007; 282:8573-82. [PMID: 17261591 DOI: 10.1074/jbc.m607976200] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulation of serine protease activity is considered to be the sole mechanism for the function of alpha1-antitrypsin (AAT). However, recent reports of the anti-inflammatory effects of AAT are hard to reconcile with this classical mechanism. We discovered that two key activities of AAT in vitro, namely inhibition of endotoxin-stimulated tumor necrosis factor-alpha and enhancement of interleukin-10 in human monocytes, are mediated by an elevation of cAMP and activation of cAMP-dependent protein kinase A. As expected with this type of mechanism, the AAT-mediated rise in cAMP and the impact on endotoxin-stimulated tumor necrosis factor-alpha and interleukin-10 was enhanced when the catabolism of cAMP was blocked by the phosphodiesterase inhibitor rolipram. These effects were still observed with modified forms of AAT lacking protease inhibitor activity.
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Affiliation(s)
- Sabina M Janciauskiene
- Department of Clinical Sciences, University Hospital Malmö, Lund University, SE-20502 Malmö, Sweden.
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445
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Rudolph JA, Pratt J, Mourya R, Steinbrecher KA, Cohen MB. Novel mechanism of cyclic AMP mediated extracellular signal regulated kinase activation in an intestinal cell line. Cell Signal 2007; 19:1221-8. [PMID: 17317103 DOI: 10.1016/j.cellsig.2007.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 12/21/2006] [Accepted: 01/08/2007] [Indexed: 11/16/2022]
Abstract
The extracellular signal regulated kinase (ERK1/2) signaling cascade has been implicated as both a pro-apoptotic and anti-apoptotic pathway depending on cell type and context. In the T84 intestinal epithelial cell line, cAMP activates ERK1/2 resulting in the inhibition of apoptosis. Cyclic-AMP signaling relies on the binding and activation of a cAMP binding protein. In most cell types, the majority of this signaling occurs through an isoform of protein kinase A (PKAI or PKAII). Despite evidence to the contrary, we hypothesized that ERK1/2 activation is through a PKA isoform. Pharmacological activators and inhibitors of PKA as well as siRNA were used to further interrogate this potential signaling pathway. Our results demonstrate that at doses sufficient to increase PKA activity, PKAII specific cAMP analogs activate ERK1/2 while PKAI analogs do not. Pharmacological inhibition of the PKAII regulatory subunit and catalytic subunit as well as siRNA knockdown of the catalytic subunit blocks ERK1/2 activation. We conclude that in the T84 cell line, cAMP binding to the PKAII regulatory subunit leads to the subsequent phosphorylation of ERK1/2 and provides insight into the mechanism of cAMP mediated survival signaling in the intestinal epithelium. These results directly implicate PKAII as a mediator of cell survival in T84 cells and provide evidence for an additional means by which cAMP can influence intestinal cell turnover.
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Affiliation(s)
- Jeffrey A Rudolph
- Division of Pediatric Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center and the University of Cincinnati, Cincinnati, Ohio, 45229, United States.
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446
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Wang Z, Shi F. Phosphodiesterase 4 and compartmentalization of cyclic AMP signaling. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/s11434-007-0025-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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447
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Andrei M, Bjørnstad V, Langli G, Rømming C, Klaveness J, Taskén K, Undheim K. Stereoselective preparation of (RP)-8-hetaryladenosine-3′,5′-cyclic phosphorothioic acids. Org Biomol Chem 2007; 5:2070-80. [PMID: 17581650 DOI: 10.1039/b702403g] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Cyclic adenosine monophosphate (cAMP) has been converted into its 8-bromo derivative and 2'O-TBDMS protected before activation of the phosphoric acid moiety with a reagent generated in situ from oxalyl chloride and DMF. Further reactions with primary amines furnished corresponding phosphoramidates with high stereoselectivity at the phosphorus atom. Cross-coupling reactions with the 8-bromopurine yielded 8-hetaryl derivatives. X-Ray analyses showed the amidates to possess the (S(P))-configuration. Carbon disulfide effected thiylation under strongly basic conditions stereospecifically provided the (R(P))-phosphorothioic acids.
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448
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Piper M, van Horck F, Holt C. The role of cyclic nucleotides in axon guidance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 621:134-43. [PMID: 18269216 PMCID: PMC3687206 DOI: 10.1007/978-0-387-76715-4_10] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
During the formation of the nervous system, axonal growth cones navigate through the complex environment of the developing embryo to innervate their targets. Growth cones achieve this formidable feat by responding to attractive or repulsive guidance cues expressed at specific points along the trajectory of their growth, which impart the directional information required for accurate pathfinding. While much is known about guidance molecules and their receptors, many questions remain unanswered. Which signal transduction pathways are activated within the growth cone after encountering a guidance cue? How is this related to rearrangement of the growth cone cytoskeleton? Do different cues use different signal transduction pathways? This chapter will review some of the work that has addressed these fundamental questions, with a specific focus on the role of the cyclic nucleotides, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), in axon guidance.
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Affiliation(s)
| | | | - Christine Holt
- Corresponding Author: Christine Holt–Department of Anatomy, University of Cambridge, Downing Street, Cambridge, CB2 3DY, U.K.
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449
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Misra UK, Pizzo SV. Upregulation of AKT1 protein expression in forskolin-stimulated macrophage: Evidence from ChIP analysis that CREB binds to and activates the AKT1 promoter. J Cell Biochem 2007; 100:1022-33. [PMID: 17152074 DOI: 10.1002/jcb.21086] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Recently, we reported that silencing CREB gene expression by RNAi significantly attenuates forskolin-induced activation of Akt1. We now provide evidence that forskolin-treatment causes transcriptional and translational upregulation of Akt1 in macrophages. Akt synthesis was demonstrated by [(14)C]leucine or [(35)S] incorporation into newly synthesized Akt1 protein. Akt protein levels increased by approximately 1.5-fold after only a 5 min exposure of macrophages to forskolin. Akt1 levels thereafter rapidly returned to basal values (t(1/2) approximately 15 min). Maximal upregulation of Akt1 occurred in cells treated with 10 microM forskolin. Forskolin-dependent Akt1 synthesis was abolished by pretreating the cells with CREB-directed dsRNA as demonstrated at both the message and protein level, as well as by determining the synthesis of [(35)S]-labeled Akt1 protein. The PKA inhibitor H-89, greatly attenuated forskolin-induced Akt1 synthesis. Transcriptional and translational inhibitors also greatly reduced Akt1 synthesis in forskolin-stimulated [(14)C]leucine-labeled macrophages. Using a chromatin immunoprecipitation assay, we demonstrate that CREB binds to a CRE binding domain of the Akt1 gene promoter. In conclusion, we show here for the first time transcriptional upregulation of Akt1 by CREB, based upon Akt1 protein synthesis and its modulation by transitional and translational inhibitors in forskolin-stimulated cells, Akt1 protein. and mRNA levels upon silencing CREB gene expression, and binding of CREB to the Akt1 gene promoter.
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Affiliation(s)
- Uma Kant Misra
- Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA
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450
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Alonso GD, Schoijet AC, Torres HN, Flawiá MM. TcrPDEA1, a cAMP-specific phosphodiesterase with atypical pharmacological properties from Trypanosoma cruzi. Mol Biochem Parasitol 2006; 152:72-9. [PMID: 17222469 DOI: 10.1016/j.molbiopara.2006.12.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 12/04/2006] [Accepted: 12/05/2006] [Indexed: 11/27/2022]
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) catalyze the degradation of cAMP and cGMP, and regulate a variety of cellular processes by controlling the levels of these second messengers. We have previously described the presence of both a calcium-stimulated adenylyl cyclase and two membrane-bound cAMP-specific PDEs (one of them strongly associated to the flagellum and the other one with a possible vesicular localization) in Trypanosoma cruzi. Here we report the identification and characterization of TcrPDEA1, a singular phosphodiesterase of T. cruzi which is resistant to the typical phosphodiesterase inhibitors, such as IBMX, papaverine and theofylline. TcrPDEA1 is a single copy gene that encodes a 620-amino acid protein, which is grouped with PDE1 family members, mainly with its kinetoplastid orthologs. TcrPDEA1 was able to complement a mutant yeast strain deficient in PDE genes, demonstrating that this enzyme is a functional phosphodiesterase. TcrPDEA1 is specific for cAMP with a high K(m) value (191.1+/-6.5 microM). Cyclic GMP neither activates the enzyme nor competes as a substrate. In addition, calcium-calmodulin did not affect the kinetic parameters and, as its counterpart in T. brucei, magnesium showed to be crucial for its activity and stability. Although TcrPDEA1 function remains unclear, its presence points out the high complexity of the cAMP signaling in trypanosomatids and the possible compartmentalization of the enzymes involved in the cAMP pathway.
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Affiliation(s)
- Guillermo D Alonso
- Consejo Nacional de Investigaciones Científicas y Técnicas and Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
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