101
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Foley E, O'Farrell PH. Functional dissection of an innate immune response by a genome-wide RNAi screen. PLoS Biol 2004; 2:E203. [PMID: 15221030 PMCID: PMC434151 DOI: 10.1371/journal.pbio.0020203] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Accepted: 05/04/2004] [Indexed: 12/18/2022] Open
Abstract
The innate immune system is ancient and highly conserved. It is the first line of defense and the only recognizable immune system in the vast majority of metazoans. Signaling events that convert pathogen detection into a defense response are central to innate immunity. Drosophila has emerged as an invaluable model organism for studying this regulation. Activation of the NF-kappaB family member Relish by the caspase-8 homolog Dredd is a central, but still poorly understood, signaling module in the response to gram-negative bacteria. To identify the genes contributing to this regulation, we produced double-stranded RNAs corresponding to the conserved genes in the Drosophila genome and used this resource in genome-wide RNA interference screens. We identified numerous inhibitors and activators of immune reporters in a cell culture model. Epistatic interactions and phenotypes defined a hierarchy of gene action and demonstrated that the conserved gene sickie is required for activation of Relish. We also showed that a second gene, defense repressor 1, encodes a product with characteristics of an inhibitor of apoptosis protein that inhibits the Dredd caspase to maintain quiescence of the signaling pathway. Molecular analysis revealed that Defense repressor 1 is upregulated by Dredd in a feedback loop. We propose that interruption of this feedback loop contributes to signal transduction.
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MESH Headings
- Amino Acid Sequence
- Animals
- Blotting, Western
- Caspase 8
- Caspases/metabolism
- Cell Line
- Drosophila
- Drosophila Proteins/metabolism
- Epistasis, Genetic
- Gene Expression Regulation
- Gene Library
- Genes, Reporter
- Genome
- Image Processing, Computer-Assisted
- Immunity, Innate
- Insect Proteins/metabolism
- Microscopy, Fluorescence
- Models, Biological
- Models, Genetic
- Molecular Sequence Data
- NF-kappa B/metabolism
- Phenotype
- RNA Interference
- RNA, Double-Stranded/metabolism
- Sequence Homology, Amino Acid
- Signal Transduction
- Transcription Factors/metabolism
- Up-Regulation
- beta-Galactosidase/metabolism
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Affiliation(s)
- Edan Foley
- 1Department of Biochemistry and Biophysics, University of California, San FranciscoSan Francisco, CaliforniaUnited States of America
| | - Patrick H O'Farrell
- 1Department of Biochemistry and Biophysics, University of California, San FranciscoSan Francisco, CaliforniaUnited States of America
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102
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Sontag E, Luangpirom A, Hladik C, Mudrak I, Ogris E, Speciale S, White CL. Altered expression levels of the protein phosphatase 2A ABalphaC enzyme are associated with Alzheimer disease pathology. J Neuropathol Exp Neurol 2004; 63:287-301. [PMID: 15099019 DOI: 10.1093/jnen/63.4.287] [Citation(s) in RCA: 186] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The formation of amyloid-containing senile plaques and tau-rich neurofibrillary tangles are central events in Alzheimer disease (AD) pathogenesis. Significantly, ABalphaC, a major protein phosphatase 2A (PP2A) holoenzyme, specifically binds to and dephosphorylates tau. Deregulation of PP2A results in tau hyperphosphorylation in vivo. Here, we compared the expression levels and distribution of PP2A subunits in various brain regions from autopsy cases of AD and aged controls with or without histological evidence of age-related neurofibrillary degeneration. Immunoblotting analyses revealed that there was a significant reduction in the total amounts of ABalphaC in AD frontal and temporal cortices that matched the decrease in PP2A activity measured in the same brain homogenates. Immunohistochemical studies showed that neuronal ABalphaC expression levels were significantly and selectively decreased in AD-affected regions and in tangle-bearing neurons, but not in AD cerebellum and in non-AD dementias. Reduced neuronal ABalphaC immunoreactivity closely correlated with tangle load, but not plaque burden, suggesting that ABalphaC dysfunction contributes to AD tau pathology. Glial cells within senile plaques were also positive for ABalphaC. Increased glial PP2A immunoreactivity was observed in both AD and non-AD cases and may play a role in the brain's response to general inflammatory processes and amyloidogenesis.
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Affiliation(s)
- Estelle Sontag
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9073, USA.
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103
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Sathyanarayanan S, Zheng X, Xiao R, Sehgal A. Posttranslational regulation of Drosophila PERIOD protein by protein phosphatase 2A. Cell 2004; 116:603-15. [PMID: 14980226 DOI: 10.1016/s0092-8674(04)00128-x] [Citation(s) in RCA: 216] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2003] [Revised: 01/09/2004] [Accepted: 01/12/2004] [Indexed: 01/04/2023]
Abstract
The posttranscriptional mechanisms that control the cycling of circadian clock protein levels are not known. Here we demonstrate a role for protein phosphatase 2A (PP2A) in the cyclic expression of the PER protein. PP2A regulatory subunits TWS and WDB target PER and stabilize it in S2 cells. In adult fly heads, expression of tws cycles robustly under control of the circadian clock. Hypomorphic tws mutants show delayed accumulation of PER, while overexpression of tws in clock neurons produces shorter, weaker rhythms. Reduction of PP2A activity reduces PER expression in central clock neurons and results in long periods and arrhythmia. In addition, overexpression of the PP2A catalytic subunit results in loss of behavioral rhythms and constitutive nuclear expression of PER. PP2A also affects PER phosphorylation in vitro and in vivo. We propose that the posttranslational mechanisms that drive cycling of PER require the rhythmic expression of PP2A.
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Affiliation(s)
- Sriram Sathyanarayanan
- Howard Hughes Medical Institute, Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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104
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Zhou HW, Nussbaumer C, Chao Y, DeLong A. Disparate roles for the regulatory A subunit isoforms in Arabidopsis protein phosphatase 2A. THE PLANT CELL 2004; 16:709-22. [PMID: 14973165 PMCID: PMC385282 DOI: 10.1105/tpc.018994] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 01/20/2004] [Indexed: 05/20/2023]
Abstract
The heterotrimeric protein phosphatase 2A (PP2A) complex comprises a catalytic subunit and regulatory A and B subunits that modulate enzyme activity and mediate interactions with other proteins. We report here the results of a systematic analysis of the Arabidopsis (Arabidopsis thaliana) regulatory A subunit gene family, which includes the ROOTS CURL IN NAPHTHYLPHTHALAMIC ACID1 (RCN1), PP2AA2, and PP2AA3 genes. All three A subunit isoforms accumulate in the organs of seedlings and adult plants, suggesting extensive overlap in expression domains. We have isolated pp2aa2 and pp2aa3 mutants and found that their phenotypes are largely normal and do not resemble that of rcn1. Whereas rcn1 pp2aa2 and rcn1 pp2aa3 double mutants exhibit striking abnormalities in all stages of development, the pp2aa2 pp2aa3 double mutant shows only modest defects. Together, these data suggest that RCN1 performs a cardinal role in regulation of phosphatase activity and that PP2AA2 and PP2AA3 functions are unmasked only when RCN1 is absent.
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Affiliation(s)
- Hong-Wei Zhou
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA
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105
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Martens E, Stevens I, Janssens V, Vermeesch J, Götz J, Goris J, Van Hoof C. Genomic Organisation, Chromosomal Localisation Tissue Distribution and Developmental Regulation of the PR61/B′ Regulatory Subunits of Protein Phosphatase 2A in Mice. J Mol Biol 2004; 336:971-86. [PMID: 15095873 DOI: 10.1016/j.jmb.2003.12.047] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Revised: 12/10/2003] [Accepted: 12/12/2003] [Indexed: 12/16/2022]
Abstract
Protein phosphatase 2A (PP2A) is a major serine/threonine-specific phosphatase playing central roles in development, cell growth and transformation. Regulation is largely accomplished by the regulatory B subunits, which determine substrate specificity, subcellular localisation and catalytic activity. The B' family, also known as the PR61 family, is the most diverse, consisting of five genes (alpha,beta,gamma,delta and epsilon) that give rise to a number of splice variants. We deduced the sequences of the different PR61 proteins in mice and found evidence for the expression of PR61alpha, beta1, gamma1, gamma2, gamma3, delta1 and epsilon. We report the genomic organisation and localisation of the murine PR61 genes (Ppp2r5a-Ppp2r5e). This information will be useful for the future realisation of PR61 knockouts. Using Northern blotting, we examined the expression of the five PR61 isoforms in different tissues. A brain-specific function can be expected for the PR611beta protein based on the high expression levels observed in murine brain. In situ hybridisation analysis of the adult brain revealed a distinct and partially overlapping pattern of mRNA expression of the various PR61 isoforms. The PR61 mRNA expression during embryonic development was examined by Northern blotting. The PR61 transcripts were differentially expressed, suggesting a specific function for each of the PR61 proteins during embryonic development and/or adult life.
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Affiliation(s)
- Ellen Martens
- Division of Biochemistry, Faculty of Medicine, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium
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106
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Silverstein AM, Mumby MC. Analysis of protein phosphatase function in Drosophila cells using RNA interference. Methods Enzymol 2004; 366:361-72. [PMID: 14674261 DOI: 10.1016/s0076-6879(03)66027-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Double stranded RNA-mediated RNA interference is an effective method to downregulate the levels of protein phosphatases in Drosophila S2 cells. In many cases, nearly complete ablation of the targeted protein can be achieved. RNAi-mediated knockdown of protein phosphatases is akin to pharmacological inhibition with drugs and can be used to determine the roles of specific protein phosphatases in intact cells. RNAi can avoid the problems associated with less than adequate specificity of phosphatase inhibitors. Although information about the signaling pathways present in Drosophila S2 cells is not as well developed as many mammalian cell lines, the Drosophila system is particularly attractive for the study of oligomeric phosphatases like PP2A. Drosophila has far fewer isoforms for the phosphatases we have examined. This is especially true of the genes for PP2A regulatory subunits where over 50 isoforms are present in mammals but only four are present in Drosophila. Once hypotheses regarding phosphatase function have been generated from RNAi experiments in S2 cells, they can potentially be tested utilizing recent advances in the use of siRNAs to conduct RNAi experiments in mammalian cell lines. RNAi in Drosophila S2 cells has proven to be a powerful technique for identifying physiological functions of signaling proteins. The RNAi method is straightforward and works routinely with almost all proteins. RNAi in S2 cells can be used to assess the role of signaling proteins in specific pathways and as a screening tool to identify new roles for signaling molecules. For example, results from RNAi analysis of PP2A show that regulation of MAP kinase signaling involves the R2/B regulatory subunit and that the R5/B56 subunits play a previously unidentified role in apoptosis. While RNAi in Drosophila S2 cells is a powerful tool for analyzing protein function, the method does have limitations. Foremost, cells may exhibit an RNAi response to any nonspecific dsRNA, even in the absence of interferon. Therefore, physiological processes that respond to nonspecific dsRNA will be difficult to study. A second limitation is the need to produce antibodies that react with Drosophila isoforms. We have found that many antibodies to mammalian protein phosphatases do not cross-react with the corresponding Drosophila proteins. Finally, the physiology and signaling pathways of S2 cells have not been extensively studied. This lack of information limits the number of available readouts that can be used when assessing the effects of protein knockdowns.
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Affiliation(s)
- Adam M Silverstein
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
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107
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Yang J, Wu J, Tan C, Klein PS. PP2A:B56epsilon is required for Wnt/beta-catenin signaling during embryonic development. Development 2003; 130:5569-78. [PMID: 14522869 DOI: 10.1242/dev.00762] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The Wnt/beta-catenin pathway plays important roles during embryonic development and growth control. The B56 regulatory subunit of protein phosphatase 2A (PP2A) has been implicated as a regulator of this pathway. However, this has not been investigated by loss-of-function analyses. Here we report loss-of-function analysis of PP2A:B56epsilon during early Xenopus embryogenesis. We provide direct evidence that PP2A:B56epsilon is required for Wnt/beta-catenin signaling upstream of Dishevelled and downstream of the Wnt ligand. We show that maternal PP2A:B56epsilon function is required for dorsal development, and PP2A:B56epsilon function is required later for the expression of the Wnt target gene engrailed, for subsequent midbrain-hindbrain boundary formation, and for closure of the neural tube. These data demonstrate a positive role for PP2A:B56epsilon in the Wnt pathway.
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Affiliation(s)
- Jing Yang
- Department of Medicine (Hematology-Oncology) Institute, University of Pennsylvania School of Medicine, 364 Clinical Research Building, 415 Curie Blvd, Philadelphia, PA 19104, USA
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108
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Sim ATR, Baldwin ML, Rostas JAP, Holst J, Ludowyke RI. The role of serine/threonine protein phosphatases in exocytosis. Biochem J 2003; 373:641-59. [PMID: 12749763 PMCID: PMC1223558 DOI: 10.1042/bj20030484] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2003] [Revised: 05/09/2003] [Accepted: 05/16/2003] [Indexed: 10/27/2022]
Abstract
Modulation of exocytosis is integral to the regulation of cellular signalling, and a variety of disorders (such as epilepsy, hypertension, diabetes and asthma) are closely associated with pathological modulation of exocytosis. Emerging evidence points to protein phosphatases as key regulators of exocytosis in many cells and, therefore, as potential targets for the design of novel therapies to treat these diseases. Diverse yet exquisite regulatory mechanisms have evolved to direct the specificity of these enzymes in controlling particular cell processes, and functionally driven studies have demonstrated differential regulation of exocytosis by individual protein phosphatases. This Review discusses the evidence for the regulation of exocytosis by protein phosphatases in three major secretory systems, (1) mast cells, in which the regulation of exocytosis of inflammatory mediators plays a major role in the respiratory response to antigens, (2) insulin-secreting cells in which regulation of exocytosis is essential for metabolic control, and (3) neurons, in which regulation of exocytosis is perhaps the most complex and is essential for effective neurotransmission.
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Affiliation(s)
- Alistair T R Sim
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, and Clinical Neuroscience Program, Hunter Medical Research Institute, Callaghan, NSW 2308, Australia.
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109
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Dagda RK, Zaucha JA, Wadzinski BE, Strack S. A developmentally regulated, neuron-specific splice variant of the variable subunit Bbeta targets protein phosphatase 2A to mitochondria and modulates apoptosis. J Biol Chem 2003; 278:24976-85. [PMID: 12716901 DOI: 10.1074/jbc.m302832200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Heterotrimeric protein phosphatase 2A (PP2A) is a major Ser/Thr phosphatase composed of catalytic, structural, and regulatory subunits. Here, we characterize Bbeta2, a novel splice variant of the neuronal Bbeta regulatory subunit with a unique N-terminal tail. Bbeta2 is expressed predominantly in forebrain areas, and PP2A holoenzymes containing Bbeta2 are about 10-fold less abundant than those containing the Bbeta1 (previously Bbeta) isoform. Bbeta2 mRNA is dramatically induced postnatally and in response to neuronal differentiation of a hippocampal progenitor cell line. The divergent N terminus of Bbeta2 does not affect phosphatase activity but encodes a subcellular targeting signal. Bbeta2, but not Bbeta1 or an N-terminal truncation mutant, colocalizes with mitochondria in neuronal PC12 cells. Moreover, the Bbeta2 N-terminal tail is sufficient to target green fluorescent protein to this organelle. Inducible or transient expression of Bbeta2, but neither Bbeta1, Bgamma, nor a Bbeta2 mutant defective in holoenzyme formation, accelerates apoptosis in response to growth factor deprivation. Thus, alternative splicing of a mitochondrial localization signal generates a PP2A holoenzyme involved in neuronal survival signaling.
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Affiliation(s)
- Ruben K Dagda
- Department of. Pharmacology, University of Iowa Carver College of Medicine, Iowa City 52242, USA
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110
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Rozovskaia T, Ravid-Amir O, Tillib S, Getz G, Feinstein E, Agrawal H, Nagler A, Rappaport EF, Issaeva I, Matsuo Y, Kees UR, Lapidot T, Lo Coco F, Foa R, Mazo A, Nakamura T, Croce CM, Cimino G, Domany E, Canaani E. Expression profiles of acute lymphoblastic and myeloblastic leukemias with ALL-1 rearrangements. Proc Natl Acad Sci U S A 2003; 100:7853-8. [PMID: 12782787 PMCID: PMC164677 DOI: 10.1073/pnas.1132115100] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ALL-1 gene is directly involved in 5-10% of acute lymphoblastic leukemias (ALLs) and acute myeloid leukemias (AMLs) by fusion to other genes or through internal rearrangements. DNA microarrays were used to determine expression profiles of ALLs and AMLs with ALL-1 rearrangements. These profiles distinguish those tumors from other ALLs and AMLs. The expression patterns of ALL-1-associated tumors, in particular ALLs, involve oncogenes, tumor suppressors, antiapoptotic genes, drug-resistance genes, etc., and correlate with the aggressive nature of the tumors. The genes whose expression differentiates between ALLs with and without ALL-1 rearrangement were further divided into several groups, enabling separation of ALL-1-associated ALLs into two subclasses. One of the groups included 43 genes that exhibited expression profiles closely linked to ALLs with ALL-1 rearrangements. Further, there were evident differences between the expression profiles of AMLs in which ALL-1 had undergone fusion to other genes and AMLs with partial duplication of ALL-1. The extensive analysis described here pinpointed genes that might have a direct role in pathogenesis.
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MESH Headings
- Chromosome Aberrations
- Chromosomes, Human, Pair 11
- Chromosomes, Human, Pair 4
- Cluster Analysis
- DNA-Binding Proteins/genetics
- Down-Regulation
- Histone-Lysine N-Methyltransferase
- Humans
- Leukemia, Myeloid, Acute/blood
- Leukemia, Myeloid, Acute/genetics
- Myeloid-Lymphoid Leukemia Protein
- Oligonucleotide Array Sequence Analysis
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/blood
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics
- Proto-Oncogenes
- Transcription Factors
- Transcription, Genetic
- Translocation, Genetic
- Up-Regulation
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Affiliation(s)
- T Rozovskaia
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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111
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Abstract
The dsRNA binding proteins (DRBPs) comprise a growing family of eukaryotic, prokaryotic, and viral-encoded products that share a common evolutionarily conserved motif specifically facilitating interaction with dsRNA. Proteins harboring dsRNA binding domains (DRBDs) have been reported to interact with as little as 11 bp of dsRNA, an event that is independent of nucleotide sequence arrangement. More than 20 DRBPs have been identified and reportedly function in a diverse range of critically important roles in the cell. Examples include the dsRNA-dependent protein kinase PKR that functions in dsRNA signaling and host defense against virus infection and DICER, which is implicated in RNA interference (RNAi) -mediated gene silencing. Other DRBPs such as Staufen, adenosine deaminase acting on RNA (ADAR), and spermatid perinuclear RNA binding protein (SPNR) are known to play essential roles in development, translation, RNA editing, and stability. In many cases, homozygous and even heterozygous disruption of DRBPs in animal models results in embryonic lethality. These results implicate the recognition of dsRNA as an evolutionarily conserved mechanism important in the regulation of gene expression and in host defense and underscore the diversity of essential biological tasks performed by dsRNA-related processes in the cell.
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Affiliation(s)
- Laura R Saunders
- Department of Microbiology and Immunology and Sylvester Comprehensive Cancer Center, University of Miami School of Medicine, Miami, Florida, USA
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112
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Van Hoof C, Goris J. Phosphatases in apoptosis: to be or not to be, PP2A is in the heart of the question. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1640:97-104. [PMID: 12729918 DOI: 10.1016/s0167-4889(03)00029-6] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Protein phosphatase type 2A (PP2A) is a major Ser/Thr phosphatase involved in several cellular signal transduction pathways. In this review, we will focus on recent progress concerning the role of PP2A in apoptotic signalling. Since PP2A activates pro-apoptotic and inhibits anti-apoptotic proteins of the Bcl-2 family, we conclude that PP2A has a positive regulatory function in apoptosis. However, in Drosophila, a specific subset of the PP2A holoenzyme family, containing B'/PR61 as third regulatory subunit, is inhibitory for apoptosis, suggesting different regulatory mechanisms and substrates in different species. Moreover, PP2A acts not only upstream as a regulator of the apoptotic signal transduction pathway but also downstream as a substrate of effector caspases. Hence, PP2A is involved in the regulation as well as in the cellular response of apoptosis. Probably, various PP2A holoenzymes with distinct regulatory subunits specifically target different apoptotic substrates. This could explain the implication of PP2A at several levels of the apoptotic signal transduction pathway. Finally, some viral proteins such as adenovirus E4orf4 and simian virus small t target PP2A to alter its activity, resulting in induction of apoptosis as a regulatory mechanism to enhance virus spread.
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Affiliation(s)
- Christine Van Hoof
- Afdeling Biochemie, Faculteit Geneeskunde, Campus Gasthuisberg O&N, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium
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113
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Goswami S, Sheets NL, Zavadil J, Chauhan BK, Bottinger EP, Reddy VN, Kantorow M, Cvekl A. Spectrum and range of oxidative stress responses of human lens epithelial cells to H2O2 insult. Invest Ophthalmol Vis Sci 2003; 44:2084-93. [PMID: 12714647 PMCID: PMC2080867 DOI: 10.1167/iovs.02-0882] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Oxidative stress (OS) is believed to be a major contributor to age-related cataract and other age-related diseases. METHODS cDNA microarrays were used to identify the spectrum and range of genes with transcript levels that are altered in response to acute H(2)O(2)-induced OS in human lens epithelial (HLE) cells. HLE cells were treated with 50 microM H(2)O(2) for 1 hour in the absence of serum, followed by a return to complete medium. RNAs were prepared from treated and untreated cells at 0, 1, 2, and 8 hours after H(2)O(2) treatment. RESULTS The data showed 1171 genes that were significantly up- and downregulated in response to H(2)O(2) treatment. Several functional subcategories of genes were identified, including those encoding DNA repair proteins, antioxidant defense enzymes, molecular chaperones, protein biosynthesis enzymes, and trafficking and degradation proteins. Differential expression of selected genes was confirmed at the level of RNA and/or protein. Many of the identified genes (e.g., glutathione S-transferase [MGST2], thioredoxin reductase beta, and peroxiredoxin 2) have been identified as participants in OS responses in the lens and other systems. Some genes induced by OS in the current study (e.g., oxygen regulated protein [ORP150] and heat shock protein [HSP40]) are better known to respond to other forms of stress. Two genes (receptor tyrosine kinase [AXL/ARK] and protein phosphatase 2A) are known to be differentially expressed in cataract. Most of the genes point to a novel pathways associated with OS. CONCLUSIONS The present data provide a global perspective on those genes that respond to acute OS, point to novel genes and pathways associated with OS, and set the groundwork for understanding the functions of OS-related genes in lens protection and disease.
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Affiliation(s)
- Sumanta Goswami
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York
| | - Nancy L. Sheets
- Department of Biology, West Virginia University, Morgantown, West Virginia
| | - Jiři Zavadil
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
| | - Bharesh K. Chauhan
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York
| | - Erwin P. Bottinger
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
| | - Venkat N. Reddy
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan
| | - Marc Kantorow
- Department of Biology, West Virginia University, Morgantown, West Virginia
| | - Aleš Cvekl
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York
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114
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Janssens V, Jordens J, Stevens I, Van Hoof C, Martens E, De Smedt H, Engelborghs Y, Waelkens E, Goris J. Identification and functional analysis of two Ca2+-binding EF-hand motifs in the B"/PR72 subunit of protein phosphatase 2A. J Biol Chem 2003; 278:10697-706. [PMID: 12524438 DOI: 10.1074/jbc.m211717200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is a multifunctional serine/threonine phosphatase that is critical to many cellular processes including cell cycle regulation and signal transduction. PP2A is a heterotrimer containing a structural (A) and catalytic (C) subunit, associated with one variable regulatory or targeting B-type subunit, of which three families have been described to date (B/PR55, B'/PR61, and B"/PR72). We identified two functional and highly conserved Ca(2+)-binding EF-hand motifs in human B"/PR72 (denoted EF1 and EF2), demonstrating for the first time the ability of Ca(2+) to interact directly with and regulate PP2A. EF1 and EF2 apparently bind Ca(2+) with different affinities. Ca(2+) induces a significant conformational change, which is dependent on the integrity of the motifs. We have further evaluated the effects of Ca(2+) on subunit composition, subcellular targeting, catalytic activity, and function during the cell cycle of a PR72-containing PP2A trimer (PP2A(T72)) by site-directed mutagenesis of either or both motifs. The results suggest that integrity of EF2 is required for A/PR65 subunit interaction and proper nuclear targeting of PR72, whereas EF1 might mediate the effects of Ca(2+) on PP2A(T72) activity in vitro and is at least partially required for the ability of PR72 to alter cell cycle progression upon forced expression.
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Affiliation(s)
- Veerle Janssens
- Division of Biochemistry, Faculty of Medicine, Katholieke Universiteit Leuven, Herestraat 49, Belgium
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115
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Stevens I, Janssens V, Martens E, Dilworth S, Goris J, Van Hoof C. Identification and characterization of B"-subunits of protein phosphatase 2 A in Xenopus laevis oocytes and adult tissues. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:376-87. [PMID: 12605688 DOI: 10.1046/j.1432-1033.2003.03398.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Protein phosphatase 2A is a phosphoserine/threonine phosphatase implicated in many cellular processes. The core enzyme comprises a catalytic and a PR65/A-subunit. The substrate specificity and subcellular localization are determined by a third regulatory B-subunit (PR55/B, PR61/B' and PR72/130/B"). To identify the proteins of the B" family in Xenopus laevis oocytes, a prophase Xenopus oocyte cDNA library was screened using human PR130 cDNA as a probe. Three different classes of cDNAs were isolated. One class is very similar to human PR130 and is probably the Xenopus orthologue of PR130 (XPR130). A second class of clones (XN73) is identical to the N-terminal part of XPR130 but ends a few amino acids downstream of the putative splicing site of PR130. To investigate how this occurs, the genomic structure of the human PR130 gene was determined. This novel protein does not act as a PP2A subunit but might compete with the function of PR130. The third set of clones (XPR70) is very similar to human PR48 but has an N-terminal extension. Further analysis of the human EST-database and the human PR48 gene structure, revealed that the human PR48 clone published is incomplete. The Xenopus orthologue of PR48 encodes a protein of 70 kDa which like the XPR130, interacts with the A-subunit in GST pull-down assays. XPR70 is ubiquitously expressed in adult tissues and oocytes whereas expression of XPR130 is very low in brain and oocytes. Expression of XN73 mainly parallels XPR130 with the exception of the brain.
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Affiliation(s)
- Ilse Stevens
- Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Leuven, Belgium
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