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Taylor SS, Herberg FW, Veglia G, Wu J. Edmond Fischer's kinase legacy: History of the protein kinase inhibitor and protein kinase A. IUBMB Life 2023; 75:311-323. [PMID: 36855225 PMCID: PMC10050139 DOI: 10.1002/iub.2714] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 02/13/2023] [Indexed: 03/02/2023]
Abstract
Although Fischer's extraordinary career came to focus mostly on the protein phosphatases, after his co-discovery of Phosphorylase Kinase with Ed Krebs he was clearly intrigued not only by cAMP-dependent protein kinase (PKA), but also by the heat-stable, high-affinity protein kinase inhibitor (PKI). PKI is an intrinsically disordered protein that contains at its N-terminus a pseudo-substrate motif that binds synergistically and with high-affinity to the PKA catalytic (C) subunit. The sequencing and characterization of this inhibitor peptide (IP20) were validated by the structure of the PKA C-subunit solved first as a binary complex with IP20 and then as a ternary complex with ATP and two magnesium ions. A second motif, nuclear export signal (NES), was later discovered in PKI. Both motifs correspond to amphipathic helices that convey high-affinity binding. The dynamic features of full-length PKI, recently captured by NMR, confirmed that the IP20 motif becomes dynamically and sequentially ordered only in the presence of the C-subunit. The type I PKA regulatory (R) subunits also contain a pseudo-substrate ATPMg2-dependent high-affinity inhibitor sequence. PKI and PKA, especially the Cβ subunit, are highly expressed in the brain, and PKI expression is also cell cycle-dependent. In addition, PKI is now linked to several cancers. The full biological importance of PKI and PKA signaling in the brain, and their importance in cancer thus remains to be elucidated.
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Affiliation(s)
- Susan S Taylor
- Department of Pharmacology, University of California, San Diego, California, USA
- Department of Chemistry and Biochemistry, University of California, San Diego, California, USA
| | | | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Jian Wu
- Department of Pharmacology, University of California, San Diego, California, USA
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2
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Pfanzagl V, Görner W, Radolf M, Parich A, Schuhmacher R, Strauss J, Reiter W, Schüller C. A constitutive active allele of the transcription factor Msn2 mimicking low PKA activity dictates metabolic remodeling in yeast. Mol Biol Cell 2018; 29:2848-2862. [PMID: 30256697 PMCID: PMC6249869 DOI: 10.1091/mbc.e18-06-0389] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In yeast, protein kinase A (PKA) adjusts transcriptional profiles, metabolic rates, and cell growth in accord with carbon source availability. PKA affects gene expression mostly via the transcription factors Msn2 and Msn4, two key regulators of the environmental stress response. Here we analyze the role of the PKA-Msn2 signaling module using an Msn2 allele that harbors serine-to-alanine substitutions at six functionally important PKA motifs (Msn2A6) . Expression of Msn2A6 mimics low PKA activity, entails a transcription profile similar to that of respiring cells, and prevents formation of colonies on glucose-containing medium. Furthermore, Msn2A6 leads to high oxygen consumption and hence high respiratory activity. Substantially increased intracellular concentrations of several carbon metabolites, such as trehalose, point to a metabolic adjustment similar to diauxic shift. This partial metabolic switch is the likely cause for the slow-growth phenotype in the presence of glucose. Consistently, Msn2A6 expression does not interfere with growth on ethanol and tolerated is to a limited degree in deletion mutant strains with a gene expression signature corresponding to nonfermentative growth. We propose that the lethality observed in mutants with hampered PKA activity resides in metabolic reprogramming that is initiated by Msn2 hyperactivity.
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Affiliation(s)
- Vera Pfanzagl
- Department of Chemistry, University of Natural Resources and Life Sciences, Vienna (BOKU), 1190 Vienna, Austria
| | - Wolfram Görner
- Department for Biochemistry, Max. F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Martin Radolf
- Management Scientific Service/EHS, Research Institute of Molecular Pathology (IMP), 1030 Vienna, Austria
| | - Alexandra Parich
- Department of Agrobiotechnology (IFA-Tulln), Center for Analytical Chemistry, University of Natural Resources and Life Sciences, 3430 Tulln, Austria
| | - Rainer Schuhmacher
- Department of Agrobiotechnology (IFA-Tulln), Center for Analytical Chemistry, University of Natural Resources and Life Sciences, 3430 Tulln, Austria
| | - Joseph Strauss
- Department of Chemistry, University of Natural Resources and Life Sciences, Vienna (BOKU), 1190 Vienna, Austria
| | - Wolfgang Reiter
- Department for Biochemistry, Max. F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Christoph Schüller
- Department of Applied Genetics and Cell Biology (DAGZ), University of Natural Resources and Life Sciences, 3430 Tulln, Austria
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3
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Torres-Quesada O, Mayrhofer JE, Stefan E. The many faces of compartmentalized PKA signalosomes. Cell Signal 2017; 37:1-11. [PMID: 28528970 DOI: 10.1016/j.cellsig.2017.05.012] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 01/03/2023]
Abstract
Cellular signal transmission requires the dynamic formation of spatiotemporally controlled molecular interactions. At the cell surface information is received by receptor complexes and relayed through intracellular signaling platforms which organize the actions of functionally interacting signaling enzymes and substrates. The list of hormone or neurotransmitter pathways that utilize the ubiquitous cAMP-sensing protein kinase A (PKA) system is expansive. This requires that the specificity, duration, and intensity of PKA responses are spatially and temporally restricted. Hereby, scaffolding proteins take the center stage for ensuring proper signal transmission. They unite second messenger sensors, activators, effectors, and kinase substrates within cellular micro-domains to precisely control and route signal propagation. A-kinase anchoring proteins (AKAPs) organize such subcellular signalosomes by tethering the PKA holoenzyme to distinct cell compartments. AKAPs differ in their modular organization showing pathway specific arrangements of interaction motifs or domains. This enables the cell- and compartment- guided assembly of signalosomes with unique enzyme composition and function. The AKAP-mediated clustering of cAMP and other second messenger sensing and interacting signaling components along with functional successive enzymes facilitates the rapid and precise dissemination of incoming signals. This review article delineates examples for different means of PKA regulation and for snapshots of compartmentalized PKA signalosomes.
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Affiliation(s)
- Omar Torres-Quesada
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Johanna E Mayrhofer
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria.
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4
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Nevo I, Oberthuer A, Botzer E, Sagi-Assif O, Maman S, Pasmanik-Chor M, Kariv N, Fischer M, Yron I, Witz IP. Gene-expression-based analysis of local and metastatic neuroblastoma variants reveals a set of genes associated with tumor progression in neuroblastoma patients. Int J Cancer 2010; 126:1570-81. [PMID: 19739072 DOI: 10.1002/ijc.24889] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Metastasis is the primary cause of mortality in Neuroblastoma (NB) patients, but the metastatic process in NB is poorly understood. Metastsis is a multistep process that requires the coordinated action of many genes. The identification of genes that promote or suppress tumor metastasis can advance our understanding of this process. In the present study, we utilized a human NB xenograft model comprising local and metastatic NB variants, which was recently developed in our laboratory. We set out to identify molecular correlates of NB metastasis and to determine the clinical relevance of these molecules. We first performed genome-wide expression profiles of metastatic and nonmetastatic NB variants that have an identical genetic background. We found that some of the proteins highly expressed in the metastatic NB variants are localized in the cytoplasm and endoplasmic reticulum. Other proteins are linked to metabolic processes and signaling pathways, thereby supporting the invasive and metastatic state of the cells. Subsequently, we intersected the differentially expressed genes in the human xenografted variants with genes differentially expressed in Stage 1 and Stage 4 primary tumors of NB patients. By using the same gene-expression platform, molecular correlates associated with metastatic progression in primary NB tumors were identified. The resulting smaller gene set was clinically relevant as it discriminated between high- and low-risk NB patients.
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Affiliation(s)
- Ido Nevo
- Department of Cell Research and Immunology, The George S. Wise Faculty of Life Science, Tel-Aviv University, Tel-Aviv, Israel
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5
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Ghildyal R, Ho A, Jans DA. Central role of the respiratory syncytial virus matrix protein in infection. FEMS Microbiol Rev 2006; 30:692-705. [PMID: 16911040 DOI: 10.1111/j.1574-6976.2006.00025.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Respiratory syncytial virus is the major respiratory pathogen of infants and children worldwide, with no effective treatment or vaccine available. Steady progress has been made in understanding the respiratory syncytial virus life cycle and the consequences of infection, but many areas of respiratory syncytial virus biology remain poorly understood, including the role of subcellular localisation of respiratory syncytial virus gene products such as the matrix protein in the infected host cell. The matrix protein plays a central role in viral assembly and, intriguingly, has been observed to traffic into and out of the nucleus at specific times during the respiratory syncytial virus infectious cycle. Further, the matrix protein has been shown to be able to inhibit transcription, which may be a key to respiratory syncytial virus pathogenesis. This review will focus on the role of the matrix protein in respiratory syncytial virus infection and what is known of its nucleocytoplasmic trafficking, the understanding of which may lead to new therapeutic approaches to combat respiratory syncytial virus, and/or vaccine development.
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Affiliation(s)
- Reena Ghildyal
- Department of Respiratory and Sleep Medicine, Monash Medical Centre, Clayton, Australia
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6
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Dalton GD, Dewey WL. Protein kinase inhibitor peptide (PKI): a family of endogenous neuropeptides that modulate neuronal cAMP-dependent protein kinase function. Neuropeptides 2006; 40:23-34. [PMID: 16442618 DOI: 10.1016/j.npep.2005.10.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Accepted: 10/11/2005] [Indexed: 11/30/2022]
Abstract
Signal transduction cascades involving cAMP-dependent protein kinase are highly conserved among a wide variety of organisms. Given the universal nature of this enzyme it is not surprising that cAMP-dependent protein kinase plays a critical role in numerous cellular processes. This is particularly evident in the nervous system where cAMP-dependent protein kinase is involved in neurotransmitter release, gene transcription, and synaptic plasticity. Protein kinase inhibitor peptide (PKI) is an endogenous thermostable peptide that modulates cAMP-dependent protein kinase function. PKI contains two distinct functional domains within its amino acid sequence that allow it to: (1) potently and specifically inhibit the activity of the free catalytic subunit of cAMP-dependent protein kinase and (2) export the free catalytic subunit of cAMP-dependent protein kinase from the nucleus. Three distinct PKI isoforms (PKIalpha, PKIbeta, PKIgamma) have been identified and each isoform is expressed in the brain. PKI modulates neuronal synaptic activity, while PKI also is involved in morphogenesis and symmetrical left-right axis formation. In addition, PKI also plays a role in regulating gene expression induced by cAMP-dependent protein kinase. Future studies should identify novel physiological functions for endogenous PKI both in the nervous system and throughout the body. Most interesting will be the determination whether functional differences exist between individual PKI isoforms which is an intriguing possibility since these isoforms exhibit: (1) cell-type specific tissue expression patterns, (2) different potencies for the inhibition of cAMP-dependent protein kinase activity, and (3) expression patterns that are hormonally, developmentally and cell-cycle regulated. Finally, synthetic peptide analogs of endogenous PKI will continue to be invaluable tools that are used to elucidate the role of cAMP-dependent protein kinase in a variety of cellular processes throughout the nervous system and the rest of the body.
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Affiliation(s)
- George D Dalton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Box 980524, Richmond, VA 23298, USA.
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7
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Sastri M, Barraclough DM, Carmichael PT, Taylor SS. A-kinase-interacting protein localizes protein kinase A in the nucleus. Proc Natl Acad Sci U S A 2005; 102:349-54. [PMID: 15630084 PMCID: PMC544310 DOI: 10.1073/pnas.0408608102] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The genetic variability and covalent modifications associated with the amino terminus of the protein kinase A (PKA) catalytic (C) subunit suggest that it may contribute to protein-protein interactions and/or localization. By using a yeast two-hybrid screen, we identified a PKA-interacting protein (AKIP1) that binds to the amino terminus (residues 1-39) of the C subunit of PKA. The interaction was localized to the A helix (residues 14-39) of the C subunit and to the carboxyl terminus of AKIP1. AKIP1 thus defines the amino-terminal A helix of PKA as a protein interaction motif. In normal breast (Hs 578 Bst) and HeLa cells, AKIP1 is present in the nucleus as speckles. A nuclear localization signal (Arg-14 and Arg-15) was identified. Upon stimulation with forskolin, HeLa cells expressing AKIP1 accumulated higher levels of the endogenous C subunit in the nucleus. Deletion of the carboxyl terminus of AKIP1 or overexpression of residues 1-39 of the C subunit abolished nuclear localization of the activated endogenous C subunit. Thus, AKIP1 describes a PKA-interacting protein that can contribute to localization by a mechanism that is distinct from A-kinase anchoring proteins that interact with the regulatory subunits.
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Affiliation(s)
- Mira Sastri
- The Howard Hughes Medical Institute and Departments of Chemistry and Biochemistry and Pharmacology, University of California at San Diego, La Jolla, CA 92093-0654, USA
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8
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Taskén K, Aandahl EM. Localized effects of cAMP mediated by distinct routes of protein kinase A. Physiol Rev 2004; 84:137-67. [PMID: 14715913 DOI: 10.1152/physrev.00021.2003] [Citation(s) in RCA: 567] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
More than 20% of the human genome encodes proteins involved in transmembrane and intracellular signaling pathways. The cAMP-protein kinase A (PKA) pathway is one of the most common and versatile signal pathways in eukaryotic cells and is involved in regulation of cellular functions in almost all tissues in mammals. Various extracellular signals converge on this signal pathway through ligand binding to G protein-coupled receptors, and the cAMP-PKA pathway is therefore tightly regulated at several levels to maintain specificity in the multitude of signal inputs. Ligand-induced changes in cAMP concentration vary in duration, amplitude, and extension into the cell, and cAMP microdomains are shaped by adenylyl cyclases that form cAMP as well as phosphodiesterases that degrade cAMP. Different PKA isozymes with distinct biochemical properties and cell-specific expression contribute to cell and organ specificity. A kinase anchoring proteins (AKAPs) target PKA to specific substrates and distinct subcellular compartments providing spatial and temporal specificity for mediation of biological effects channeled through the cAMP-PKA pathway. AKAPs also serve as scaffolding proteins that assemble PKA together with signal terminators such as phosphatases and cAMP-specific phosphodiesterases as well as components of other signaling pathways into multiprotein signaling complexes that serve as crossroads for different paths of cell signaling. Targeting of PKA and integration of a wide repertoire of proteins involved in signal transduction into complex signal networks further increase the specificity required for the precise regulation of numerous cellular and physiological processes.
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Affiliation(s)
- Kjetil Taskén
- The Biotechnology Centre of Oslo, University of Oslo, Norway.
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9
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Brown VM, Krynetski EY, Krynetskaia NF, Grieger D, Mukatira ST, Murti KG, Slaughter CA, Park HW, Evans WE. A novel CRM1-mediated nuclear export signal governs nuclear accumulation of glyceraldehyde-3-phosphate dehydrogenase following genotoxic stress. J Biol Chem 2004; 279:5984-92. [PMID: 14617633 DOI: 10.1074/jbc.m307071200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein with glycolytic and non-glycolytic functions, including pro-apoptotic activity. GAPDH accumulates in the nucleus after cells are treated with genotoxic drugs, and it is present in a protein complex that binds DNA modified by thioguanine incorporation. We identified a novel CRM1-dependent nuclear export signal (NES) comprising 13 amino acids (KKVVKQASEGPLK) in the C-terminal domain of GAPDH, truncation or mutation of which abrogated CRM1 binding and caused nuclear accumulation of GAPDH. Alanine scanning of the sequence encompassing the putative NES demonstrated at least two regions important for nuclear export. Site mutagenesis of Lys259 did not affect oligomerization but impaired nuclear efflux of GAPDH, indicating that this amino acid residue is essential for proper functioning of this NES. This novel NES does not contain multiple leucine residues unlike other CRM1-interacting NES, is conserved in GAPDH from multiple species, and has sequence similarities to the export signal found in feline immunodeficiency virus Rev protein. Similar sequences (KKVV*7-13PLK) were found in two other human proteins, U5 small nuclear ribonucleoprotein, and transcription factor BT3.
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MESH Headings
- Active Transport, Cell Nucleus
- Alanine/chemistry
- Amino Acid Sequence
- Amino Acids/chemistry
- Antibodies, Monoclonal
- Apoptosis
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Chromatography
- Cytosol/metabolism
- DNA/metabolism
- Epitopes/chemistry
- Glyceraldehyde-3-Phosphate Dehydrogenases/metabolism
- Green Fluorescent Proteins
- Humans
- Karyopherins/metabolism
- Luminescent Proteins/metabolism
- Lysine/chemistry
- Microscopy, Confocal
- Microscopy, Fluorescence
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Nuclear Localization Signals
- Peptides/chemistry
- Precipitin Tests
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Cytoplasmic and Nuclear
- Recombinant Fusion Proteins/metabolism
- Ribonucleoprotein, U5 Small Nuclear/chemistry
- Trans-Activators/chemistry
- Transfection
- Exportin 1 Protein
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Affiliation(s)
- Victor M Brown
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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10
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Humphries KM, Juliano C, Taylor SS. Regulation of cAMP-dependent protein kinase activity by glutathionylation. J Biol Chem 2002; 277:43505-11. [PMID: 12189155 DOI: 10.1074/jbc.m207088200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The catalytic subunit of cAMP-dependent protein kinase (cAPK) is susceptible to inactivation by a number of thiol-modifying reagents. Inactivation occurs through modification of cysteine 199, which is located near the active site. Because cysteine 199 is reactive at physiological pH, and modification of this site inhibits activity, we hypothesized that cAPK is a likely target for regulation by an oxidative mechanism, specifically glutathionylation. In vitro studies demonstrated the susceptibility of kinase activity to the sulfhydryl oxidant diamide, which inhibited by promoting an intramolecular disulfide bond between cysteines 199 and 343. In the presence of a low concentration of diamide and reduced glutathione, the kinase was rapidly and reversibly inhibited by glutathionylation. Mutant kinase containing an alanine to cysteine mutation at position 199 was resistant to inhibition by both diamide and glutathionylation, thus implicating this as the oxidation-sensitive site. Mouse fibroblast cells treated with diamide showed a reversible decrease in cAPK activity. Inhibition was dramatically enhanced when cells were first treated with cAPK activators. Using biotin-cysteine as means for detecting and purifying thiolated cAPK from cells, we were able to show that, under conditions in which cAPK is inactivated by diamide, it is also readily thiolated.
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Affiliation(s)
- Kenneth M Humphries
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, The University of California, San Diego, La Jolla, California 92093-0654, USA
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11
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Cheng G, Brett ME, He B. Signals that dictate nuclear, nucleolar, and cytoplasmic shuttling of the gamma(1)34.5 protein of herpes simplex virus type 1. J Virol 2002; 76:9434-45. [PMID: 12186925 PMCID: PMC136443 DOI: 10.1128/jvi.76.18.9434-9445.2002] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gamma(1)34.5 protein of herpes simplex virus type 1 (HSV-1) is required for viral neurovirulence in vivo. In infected cells, this viral protein prevents the shutoff of protein synthesis mediated by double-stranded-RNA-dependent protein kinase PKR. This is accomplished by recruiting protein phosphatase 1 to dephosphorylate the alpha subunit of translation initiation factor eIF-2 (eIF-2 alpha). Moreover, the gamma(1)34.5 protein is implicated in viral egress and interacts with proliferating cell nuclear antigen. In this report, we show that the gamma(1)34.5 protein encoded by HSV-1(F) is distributed in the nucleus, nucleolus, and cytoplasm in transfected or superinfected cells. Deletion analysis revealed that the Arg-rich cluster from amino acids 1 to 16 in the gamma(1)34.5 protein functions as a nucleolar localization signal. The region from amino acids 208 to 236, containing a bipartite basic amino acid cluster, is able to mediate nuclear localization. R(215)A and R(216)A substitutions in the bipartite motif disrupt this activity. Intriguingly, leptomycin B, an inhibitor of nuclear export, blocks the cytoplasmic accumulation of the gamma(1)34.5 protein. L(134)A and L(136)A substitutions in the leucine-rich motif completely excluded the gamma(1)34.5 protein from the cytoplasm. These results suggest that the gamma(1)34.5 protein continuously shuttles between the nucleus, nucleolus, and cytoplasm, which may be a requirement for the different activities of the gamma(1)34.5 protein in virus-infected cells.
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Affiliation(s)
- Guofeng Cheng
- Department of Microbiology and Immunology, College of Medicine, The University of Illinois at Chicago, Chicago, Illinois 60612, USA
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12
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Johnson DA, Akamine P, Radzio-Andzelm E, Madhusudan M, Taylor SS. Dynamics of cAMP-dependent protein kinase. Chem Rev 2001; 101:2243-70. [PMID: 11749372 DOI: 10.1021/cr000226k] [Citation(s) in RCA: 317] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D A Johnson
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0654, USA
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13
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Abstract
The second messenger cascade of cyclic AMP (cAMP) plays an important physiological role in neurones, modulating neuronal excitability and synaptic transmission. The fluorescent probe FlCRhR allows real time ratiometric imaging of cAMP changes inside cells (Nature 349 (1991) 694). Until now, the only way to introduce FlCRhR into cells was microinjection, which restricted the use of FlCRhR to large invertebrate neurones. This report describes the use of the patch-clamp technique to deliver FlCRhR into the cytosol of several types of neurones in brain slice preparations. Direct activation of adenylate cyclase by forskolin produced marked increases in fluorescence ratio, confirming that the probe can report cAMP increases. However, some neurones failed to exhibit a cAMP response and this lack of response was related to the nucleus integrity. Stimulation of membrane receptors positively coupled to adenylate cyclase elicited cAMP increases in various neuronal cell types. This is the first report of a cAMP response to neuromodulators measured by an imaging technique in neurones in brain slices. The method described here could find many applications such as testing the ability of agonists to specifically activate the cAMP cascade in identified neurones, studying the kinetics of the cAMP response and determining the subcellular localisation of cAMP changes.
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Affiliation(s)
- P Vincent
- Equipe Neurobiologie Cellulaire, Neurobiologie des Processus Adaptatifs FRE 2371, CNRS Université Paris VI, Mailbox #16, 9, quai St. Bernard, F-75005 Paris, France.
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14
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Taylor MK, Uhler MD. The amino-terminal cyclic nucleotide binding site of the type II cGMP-dependent protein kinase is essential for full cyclic nucleotide-dependent activation. J Biol Chem 2000; 275:28053-62. [PMID: 10864932 DOI: 10.1074/jbc.m004184200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
For the type I cGMP-dependent protein kinases (cGKIalpha and cGKIbeta), a high affinity interaction exists between the C2 amino group of cGMP and the hydroxyl side chain of a threonine conserved in most cGMP binding sites. To examine the effect of this interaction on ligand binding and kinase activation in the type II isozyme of cGMP-dependent protein kinase (cGKII), alanine was substituted for the conserved threonine or serine. cGKII was found to require the C2 amino group of cGMP and its cognate serine or threonine hydroxyl for efficient cGMP activation. Of the two binding sites, disruption of cGMP-specific binding in the NH(2)-terminal binding site had the greatest effect on cGMP-dependent kinase activation, like cGKI. However, ligand dissociation studies showed that the location of the rapid and slow dissociation sites of cGKII was reversed relative to cGKI. Another set of mutations that prevented cyclic nucleotide binding demonstrated the necessity of the NH(2)-terminal, rapid dissociation binding site for cyclic nucleotide-dependent activation of cGKII. These findings suggest distinct mechanisms of activation for cGKII and cGKI isoforms. Because cGKII mediates the effects of heat-stable enterotoxins via the cystic fibrosis transmembrane regulator Cl(-) channel, these findings define a structural target for drug design.
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Affiliation(s)
- M K Taylor
- Department of Biological Chemistry, the Neuroscience Graduate Program, and the Mental Health Research Institute, University of Michigan, Ann Arbor, Michigan 48104, USA
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15
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Orellana SA, Marfella-Scivittaro C. Distinctive cyclic AMP-dependent protein kinase subunit localization is associated with cyst formation and loss of tubulogenic capacity in Madin-Darby canine kidney cell clones. J Biol Chem 2000; 275:21233-40. [PMID: 10767293 DOI: 10.1074/jbc.m001964200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycystic kidney disease is characterized by abnormal morphological development. Mechanisms that regulate cyst development may involve multiple signaling pathways. Cyst formation by Madin-Darby canine kidney (MDCK) cells in three-dimensional culture is assumed to be cyclic AMP-dependent and due to cyclic AMP-dependent protein kinase (cAPK) activation based on pharmacological responsiveness. To determine if different cyclic AMP (cAMP) pathways are associated with morphological development, the role of cAMP in regulating morphological change was examined in MDCK clones that form tumor-like or tubular structures under basal conditions. Pharmacological cAMP pathway activators induce cyst formation and diminish formation of other structures in three clones, whereas one clone is unaffected. Tyrosine kinase-mediated morphogens have little effect. Although all clones have intact cAMP signaling pathways, each has a unique subcellular distribution of cAPK regulatory subunits. This may reflect distinct mechanisms for cAPK anchoring, allowing cAPK subtype regulation of the unique phenotypic character of each clone through preferential access to substrates. These observations suggest a molecular basis for differential cAMP responsiveness in cells that develop distinct morphological phenotypes. This evidence establishes these MDCK clones as models for understanding the mechanism and functional significance of cAPK subunit localization and may have broader implications for cystogenesis in polycystic kidney disease.
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Affiliation(s)
- S A Orellana
- Department of Pediatrics, Case Western Reserve University School of Medicine, The Rainbow Center for Childhood PKD at Rainbow Babies and Children's Hospital of the University Hospitals of Cleveland, Cleveland, Ohio, USA.
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16
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Smith CM, Radzio-Andzelm E, Akamine P, Taylor SS. The catalytic subunit of cAMP-dependent protein kinase: prototype for an extended network of communication. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1999; 71:313-41. [PMID: 10354702 DOI: 10.1016/s0079-6107(98)00059-5] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The protein kinase catalytic core in essence comprises an extended network of interactions that link distal parts of the molecule to the active site where they facilitate phosphoryl transfer from ATP to protein substrate. This review defines key sequence and structural elements, describes what is currently known about the molecular interactions, and how they are involved in catalysis.
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Affiliation(s)
- C M Smith
- San Diego Supercomputer Center, University of California, La Jolla 92093-0505, USA.
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17
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Kiger JA, Eklund JL, Younger SH, O'Kane CJ. Transgenic inhibitors identify two roles for protein kinase A in Drosophila development. Genetics 1999; 152:281-90. [PMID: 10224260 PMCID: PMC1460600 DOI: 10.1093/genetics/152.1.281] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have initiated an analysis of protein kinase A (PKA) in Drosophila using transgenic techniques to modulate PKA activity in specific tissues during development. We have constructed GAL4/UAS-regulated transgenes in active and mutant forms that encode PKAc, the catalytic subunit of PKA, and PKI(1-31), a competitive inhibitor of PKAc. We present evidence that the wild-type transgenes are active and summarize the phenotypes produced by a number of GAL4 enhancer-detector strains. We compare the effects of transgenes encoding PKI(1-31) with those encoding PKAr*, a mutant regulatory subunit that constitutively inhibits PKAc because of its inability to bind cyclic AMP. Both inhibitors block larval growth, but only PKAr* alters pattern formation by activating the Hedgehog signaling pathway. Therefore, transgenic PKI(1-31) should provide a tool to investigate the role of PKAc in larval growth regulation without concomitant changes in pattern formation. The different effects of PKI(1-31) and PKAr* suggest two distinct roles, cytoplasmic and nuclear, for PKAc in Hedgehog signal transduction. Alternatively, PKAr* may target proteins other than PKAc, suggesting a role for free PKAr in signal transduction, a role inhibited by PKAc in reversal of the classical relationship of these subunits.
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Affiliation(s)
- J A Kiger
- Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
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18
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Wiley JC, Wailes LA, Idzerda RL, McKnight GS. Role of regulatory subunits and protein kinase inhibitor (PKI) in determining nuclear localization and activity of the catalytic subunit of protein kinase A. J Biol Chem 1999; 274:6381-7. [PMID: 10037729 DOI: 10.1074/jbc.274.10.6381] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulation of protein kinase A by subcellular localization may be critical to target catalytic subunits to specific substrates. We employed epitope-tagged catalytic subunit to correlate subcellular localization and gene-inducing activity in the presence of regulatory subunit or protein kinase inhibitor (PKI). Transiently expressed catalytic subunit distributed throughout the cell and induced gene expression. Co-expression of regulatory subunit or PKI blocked gene induction and prevented nuclear accumulation. A mutant PKI lacking the nuclear export signal blocked gene induction but not nuclear accumulation, demonstrating that nuclear export is not essential to inhibit gene induction. When the catalytic subunit was targeted to the nucleus with a nuclear localization signal, it was not sequestered in the cytoplasm by regulatory subunit, although its activity was completely inhibited. PKI redistributed the nuclear catalytic subunit to the cytoplasm and blocked gene induction, demonstrating that the nuclear export signal of PKI can override a strong nuclear localization signal. With increasing PKI, the export process appeared to saturate, resulting in the return of catalytic subunit to the nucleus. These results demonstrate that both the regulatory subunit and PKI are able to completely inhibit the gene-inducing activity of the catalytic subunit even when the catalytic subunit is forced to concentrate in the nuclear compartment.
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Affiliation(s)
- J C Wiley
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7750, USA
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Aldred A, Nagy LE. Ethanol dissociates hormone-stimulated cAMP production from inhibition of TNF-alpha production in rat Kupffer cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:G98-G106. [PMID: 9886984 DOI: 10.1152/ajpgi.1999.276.1.g98] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ethanol impairs hormone-stimulated cAMP production in a number of cell types, yet the effects of ethanol on downstream responses mediated by cAMP-dependent protein kinase (PKA) are not understood. Here we have investigated the effects of ethanol feeding on cAMP-mediated inhibition of tumor necrosis factor-alpha (TNF-alpha) synthesis in rat Kupffer cells. Male Wistar rats were fed liquid diets containing 36% of calories as ethanol for 4 wk or were pair fed a control diet. Stimulation of cAMP production by the adenosine A2 receptor agonist 5'-(N-ethylcarboxamido)-adenosine (NECA), prostaglandin E2, or forskolin was decreased to 25% of control values in Kupffer cells isolated from ethanol-fed rats. This decrease was associated with a reduction in the quantity of immunoreactive Gsalpha protein in ethanol-fed rats, with no changes observed in Gialpha or Gbeta. TNF-alpha production was higher in ethanol-fed rats in response to stimulation with lipopolysaccharide or latex beads. Despite the profound reduction in the ability of hormone to increase cAMP production, NECA and prostaglandin E2 inhibited TNF-alpha production to an equivalent degree in Kupffer cells from ethanol- and pair-fed rats. Total activity and immuoreactive protein quantity of PKA did not differ between groups. Activation of PKA in response to a 15-min treatment with 1 microM NECA was reduced by 50% in ethanol-fed rats compared with control. Despite this reduction in activation, translocation of the catalytic subunit of PKA to the nucleus and phosphorylation of cAMP response element binding protein in response to activation were observed in Kupffer cells from both ethanol- and pair-fed rats. These data demonstrate that there is a dissociation between ethanol-induced desensitization of hormone-stimulated cAMP production in rat Kupffer cells and the downstream inhibition of TNF-alpha production mediated by cAMP.
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Affiliation(s)
- A Aldred
- Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Wang W, Li P, Schettino A, Peng Z, McLeod M. Characterization of functional regions in the Schizosaccharomyces pombe mei3 developmental activator. Genetics 1998; 150:1007-18. [PMID: 9799254 PMCID: PMC1460408 DOI: 10.1093/genetics/150.3.1007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Schizosaccharomyces pombe mei3(+) gene is expressed only in diploid cells undergoing meiosis. Ectopic expression of mei3(+) in haploid cells causes meiotic catastrophe. Mei3 is an inhibitor of Ran1/Pat1 kinase and contains a nine-amino-acid motif, Mei3-RKDIII, that resembles two regions in the Ste11 substrate for Ran1/Pat1. Substitution of serine for Arg-81 within Mei3-RKDIII transforms the inhibitor into a substrate for Ran1/Pat1. Thus, it is likely that Mei3-RKDIII defines a pseudosubstrate sequence. In this study, we constructed a series of mei3 deletion mutations and assayed each for activity. This analysis indicates that the carboxy-terminal domain of Mei3 is sufficient for function in vivo. Alanine-scanning mutagenesis identifies critical residues within the inhibitory domain. Two mutations, SM1 and SM8, fail to cause meiotic catastrophe. The SM1 mutation contains alterations of amino acid residues in Mei3-RKDIII. Recombinant SM1 protein exhibits reduced ability to inhibit Ran1/Pat1 kinase in vitro and interacts inefficiently with the kinase in a two-hybrid assay. The SM8 protein binds to Ran1/Pat1 in a two-hybrid assay but fails to inhibit Ran1/Pat1 substrate phosphorylation in vitro. These findings provide evidence that Mei3-RKDIII defines a Ran1/Pat1-binding site that is necessary but not sufficient for inhibition of the kinase. Using fusions to green fluorescent protein, the cellular localization of Ran1 and Mei3 was examined in living cells. Ran1 is concentrated in the nucleus. Mei3 is also enriched in the nucleus and, consistent with the genetic and biochemical results, the inhibitory domain of Mei3 is sufficient for nuclear localization.
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Affiliation(s)
- W Wang
- Department of Microbiology and Immunology, Morse Institute for Molecular Biology and Genetics, Health Science Center, State University of New York, Brooklyn, New York 11203, USA
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21
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Chiorini JA, Zimmermann B, Yang L, Smith RH, Ahearn A, Herberg F, Kotin RM. Inhibition of PrKX, a novel protein kinase, and the cyclic AMP-dependent protein kinase PKA by the regulatory proteins of adeno-associated virus type 2. Mol Cell Biol 1998; 18:5921-9. [PMID: 9742109 PMCID: PMC109178 DOI: 10.1128/mcb.18.10.5921] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated virus encodes four nonstructural proteins, which are known as Rep78, Rep68, Rep52, and Rep40. Expression of these nonstructural proteins affects cell growth and gene expression through processes that have not yet been characterized. Using a yeast two-hybrid screen, we have demonstrated that a stable interaction occurs between the viral proteins Rep78 and Rep52 and the putative protein kinase PrKX, which is encoded on the X chromosome. The stability and specificity of the Rep-PrKX interaction were confirmed by coimmunoprecipitation of complexes assembled in vitro and in vivo. Overexpressed PrKX, which was purified from cos cells, was shown to phosphorylate a synthetic protein kinase A (PKA) substrate. However, this activity was dramatically inhibited by stoichiometric amounts of Rep52 and weakly inhibited with Rep68, which lacks the carboxy-terminal sequence contained in Rep52. Similarly, a stable interaction was observed with Rep78, which also contains the carboxy-terminal sequence of Rep52. A stable interaction and inhibition were also observed between Rep52 and the catalytic subunit of PKA. By using surface plasmon resonance and kinetic studies, Kis of approximately 300 and 167 nM were calculated for Rep52 with PKA and with PrKX, respectively. Thus, Rep52 but not Rep68 can significantly inhibit the trans- and autophosphorylation activities of these kinases. The biological effects of Rep78-specific inhibition of PKA-responsive genes are illustrated by the reduction of steady-state levels of cyclic AMP-responsive-element-binding protein and cyclin A protein.
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Affiliation(s)
- J A Chiorini
- Molecular Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892, USA
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Taagepera S, McDonald D, Loeb JE, Whitaker LL, McElroy AK, Wang JY, Hope TJ. Nuclear-cytoplasmic shuttling of C-ABL tyrosine kinase. Proc Natl Acad Sci U S A 1998; 95:7457-62. [PMID: 9636171 PMCID: PMC22649 DOI: 10.1073/pnas.95.13.7457] [Citation(s) in RCA: 244] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The ubiquitously expressed nonreceptor tyrosine kinase c-Abl contains three nuclear localization signals, however, it is found in both the nucleus and the cytoplasm of proliferating fibroblasts. A rapid and transient loss of c-Abl from the nucleus is observed upon the initial adhesion of fibroblasts onto a fibronectin matrix, suggesting the possibility of nuclear export [Lewis, J., Baskaran, R. , Taagepera, S., Schwartz, M. & Wang, J. (1996) Proc. Natl. Acad. Sci. USA 93, 15174-15179]. Here we show that the C terminus of c-Abl does indeed contain a functional nuclear export signal (NES) with the characteristic leucine-rich motif. The c-Abl NES can functionally complement an NES-defective HIV Rev protein (RevDelta3NI) and can mediate the nuclear export of glutathione-S-transferase. The c-Abl NES function is sensitive to the nuclear export inhibitor leptomycin B. Mutation of a single leucine (L1064A) in the c-Abl NES abrogates export function. The NES-mutated c-Abl, termed c-Abl NES(-), is localized exclusively to the nucleus. Treatment of cells with leptomycin B also leads to the nuclear accumulation of wild-type c-Abl protein. The c-Abl NES(-) is not lost from the nucleus when detached fibroblasts are replated onto fibronectin matrix. Taken together, these results demonstrate that c-Abl shuttles continuously between the nucleus and the cytoplasm and that the rate of nuclear import and export can be modulated by the adherence status of fibroblastic cells.
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Affiliation(s)
- S Taagepera
- Department of Biology, Center for Molecular Genetics and the Cancer Center, University of California at San Diego, La Jolla CA 92093-0322, USA
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23
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O'Brien LJ, Levac KD, Nagy LE. Moderate dietary protein and energy restriction modulate cAMP-dependent protein kinase activity in rat liver. J Nutr 1998; 128:927-33. [PMID: 9614149 DOI: 10.1093/jn/128.6.927] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Very low protein diets result in a desensitization of hepatic cAMP signaling in rats, which is characterized by a loss of cAMP-dependent protein kinase (PKA) activity and type I regulatory subunit (RI). Here we have tested whether more moderate protein restriction (Trial 1) or energy restriction (Trial 2) also modulates hepatic PKA quantity and activity. In trial 1, weanling rats were allowed free access to diets containing normal protein (15%, AL-NP), moderately restricted protein (12.5%, AL-MP) and low protein (7.5%, AL-LP); in trial 2, rats were allowed free access to diet containing 15% (AL-NP) or 0.5% protein (very low protein, AL-VLP) or were energy restricted by pair-feeding a diet isonitrogenous to AL-NP but at 65% of the energy intake (ER-IN) for 14 d. Body weights were lower (P < 0.05) by d 14 in all restricted groups compared with the AL-NP group. The quantity of cytosolic RI was lower (P < 0.05) in AL-LP and AL-VLP, but not in AL-MP or ER-IN, compared with AL-NP. In contrast, there was no effect of diet on RI in the particulate fraction. RII was not changed by moderate and low protein diets in either the cytosol or particulate fraction. However, type II regulatory subunit (RII) was greater in the cytosol of ER-IN and in the particulate fraction of AL-VLP (P < 0.05) compared with AL-NP. Specific activity of PKA was lower in the cytosol and particulate fraction (P < 0.05) in the AL-VLP and ER-IN groups compared with the AL-NP group. In contrast, specific activity of PKA was maintained in cytosol from AL-LP, but lower in the particulate fraction (P < 0.05) compared with AL-NP. In summary, protein restricted-diets lower RI subunit in the cytosol; however, only in rats fed very low protein diets is this loss of RI associated with lower cytosolic PKA activity. In contrast, energy restriction lowers PKA activity in the cytosol and particulate fractions, independent of signficant reduction in RI or RII subunits. Taken together, these data indicate that moderate protein and energy restrictions have differential effects on activity and quantity of PKA.
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Affiliation(s)
- L J O'Brien
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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Abstract
Zyxin is a low abundance phosphoprotein that is localized at sites of cell-substratum adhesion in fibroblasts. Zyxin displays the architectural features of an intracellular signal transducer. The protein exhibits an extensive proline-rich domain, a nuclear export signal and three copies of the LIM motif, a double zinc-finger domain found in many proteins that play central roles in regulation of cell differentiation. Zyxin interacts with alpha-actinin, members of the cysteine-rich protein (CRP) family, proteins that display Src homology 3 (SH3) domains and Ena/VASP family members. Zyxin and its partners have been implicated in the spatial control of actin filament assembly as well as in pathways important for cell differentiation. Based on its repertoire of binding partners and its behavior, zyxin may serve as a scaffold for the assembly of multimeric protein machines that function in the nucleus and at sites of cell adhesion.
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Affiliation(s)
- M C Beckerle
- Department of Biology, University of Utah, Salt Lake City 84112, USA
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Fritz CC, Green MR. HIV Rev uses a conserved cellular protein export pathway for the nucleocytoplasmic transport of viral RNAs. Curr Biol 1996; 6:848-54. [PMID: 8805303 DOI: 10.1016/s0960-9822(02)00608-5] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND The structural proteins of human immunodeficiency virus type 1 (HIV-1) are encoded by intron-containing mRNAs that normally are retained in the nucleus. A viral regulatory protein, Rev, specifically induces the accumulation of these transcripts in the cytoplasm. Rev is an RNA-binding protein that also contains an 'effector' domain. The Rev effector domain has recently been shown to function as an autonomous nuclear export signal (NES) that, when fused to a foreign protein, will cause its rapid nuclear export. We and others have recently reported the cloning of a human protein (hRIP/Rab), that specifically interacts with the effector domain of Rev. RESULTS Here we show that the NESs contained within two cellular proteins, PKI and I kappa B, which are not involved in RNA metabolism, also interact with hRIP. Fusion of these cellular sequences to the Rev RNA-binding domain reconstitutes a functional Rev protein. In addition to hRIP, these NESs also bind to several nuclear pore complex (NPC). We show that this protein export pathway is highly conserved by demonstrating that mammalian NESs also function in yeast. CONCLUSIONS Our results indicate that the HIV-1 Rev protein evolved to take advantage of a cellular protein export pathway in order to allow the nucleocytoplasmic transport of unspliced viral RNA. Our data suggest a model in which the export substrate is translocated through the NPC by sequential interactions with different nucleoporins. Finally, our experiment suggests a mechanism by which I kappa B can downregulate nuclear NF kappa B activity by causing its rapid export from the nucleus.
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Affiliation(s)
- C C Fritz
- Howard Hughes Medical Institute, Program in Molecular Medicine, University of Massachusetts Medical Center, Worcester 01605, USA
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Wen W, Meinkoth JL, Tsien RY, Taylor SS. Identification of a signal for rapid export of proteins from the nucleus. Cell 1995; 82:463-73. [PMID: 7634336 DOI: 10.1016/0092-8674(95)90435-2] [Citation(s) in RCA: 949] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Active nuclear import of protein is controlled by nuclear localization signals (NLSs), but nuclear export is not understood well. Nuclear trafficking of the catalytic (C) subunit of cAMP-dependent protein kinase (cAPK) is critical for regulation of gene expression. The heat-stable inhibitor (PKl) of cAPK contains a nuclear export signal (NES) that triggers rapid, active net extrusion of the C-PKl complex from the nucleus. This NES (residues 35-49), fused or conjugated to heterologous proteins, was sufficient for rapid nuclear export. Hydrophobic residues were critical. The NES is a slightly weaker signal than the SV40 NLS. A sequence containing only residues 37-46, LALKLAGLDI, is also sufficient for nuclear export. This is an example of a protein-based NES having no obvious association with RNA. A similar sequence, LQLPPLERLTL, from Rev, an RNA-binding protein of HIV-1, also is an NES.
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Affiliation(s)
- W Wen
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of California, San Diego, La Jolla 92093-0654, USA
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