151
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Li L, Tibiche C, Fu C, Kaneko T, Moran MF, Schiller MR, Li SSC, Wang E. The human phosphotyrosine signaling network: evolution and hotspots of hijacking in cancer. Genome Res 2011; 22:1222-30. [PMID: 22194470 PMCID: PMC3396364 DOI: 10.1101/gr.128819.111] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Phosphotyrosine (pTyr) signaling, which plays a central role in cell–cell and cell–environment interactions, has been considered to be an evolutionary innovation in multicellular metazoans. However, neither the emergence nor the evolution of the human pTyr signaling system is currently understood. Tyrosine kinase (TK) circuits, each of which consists of a TK writer, a kinase substrate, and a related reader, such as Src homology (SH) 2 domains and pTyr-binding (PTB) domains, comprise the core machinery of the pTyr signaling network. In this study, we analyzed the evolutionary trajectories of 583 literature-derived and 50,000 computationally predicted human TK circuits in 19 representative eukaryotic species and assigned their evolutionary origins. We found that human TK circuits for intracellular pTyr signaling originated largely from primitive organisms, whereas the inter- or extracellular signaling circuits experienced significant expansion in the bilaterian lineage through the “back-wiring” of newly evolved kinases to primitive substrates and SH2/PTB domains. Conversely, the TK circuits that are involved in tissue-specific signaling evolved mainly in vertebrates by the back-wiring of vertebrate substrates to primitive kinases and SH2/PTB domains. Importantly, we found that cancer signaling preferentially employs the pTyr sites, which are linked to more TK circuits. Our work provides insights into the evolutionary paths of the human pTyr signaling circuits and suggests the use of a network approach for cancer intervention through the targeting of key pTyr sites and their associated signaling hubs in the network.
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Affiliation(s)
- Lei Li
- Department of Biochemistry and the Siebens-Drake Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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152
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Uhrig RG, Moorhead GB. Two ancient bacterial-like PPP family phosphatases from Arabidopsis are highly conserved plant proteins that possess unique properties. PLANT PHYSIOLOGY 2011; 157:1778-92. [PMID: 21976480 PMCID: PMC3327225 DOI: 10.1104/pp.111.182493] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Protein phosphorylation, catalyzed by the opposing actions of protein kinases and phosphatases, is a cornerstone of cellular signaling and regulation. Since their discovery, protein phosphatases have emerged as highly regulated enzymes with specificity that rivals their counteracting kinase partners. However, despite years of focused characterization in mammalian and yeast systems, many protein phosphatases in plants remain poorly or incompletely characterized. Here, we describe a bioinformatic, biochemical, and cellular examination of an ancient, Bacterial-like subclass of the phosphoprotein phosphatase (PPP) family designated the Shewanella-like protein phosphatases (SLP phosphatases). The SLP phosphatase subcluster is highly conserved in all plants, mosses, and green algae, with members also found in select fungi, protists, and bacteria. As in other plant species, the nucleus-encoded Arabidopsis (Arabidopsis thaliana) SLP phosphatases (AtSLP1 and AtSLP2) lack genetic redundancy and phylogenetically cluster into two distinct groups that maintain different subcellular localizations, with SLP1 being chloroplastic and SLP2 being cytosolic. Using heterologously expressed and purified protein, the enzymatic properties of both AtSLP1 and AtSLP2 were examined, revealing unique metal cation preferences in addition to a complete insensitivity to the classic serine/threonine PPP protein phosphatase inhibitors okadaic acid and microcystin. The unique properties and high conservation of the plant SLP phosphatases, coupled to their exclusion from animals, red algae, cyanobacteria, archaea, and most bacteria, render understanding the function(s) of this new subclass of PPP family protein phosphatases of particular interest.
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153
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Uhrig RG, Moorhead GB. Okadaic acid and microcystin insensitive PPP-family phosphatases may represent novel biotechnology targets. PLANT SIGNALING & BEHAVIOR 2011; 6:2057-9. [PMID: 22112445 PMCID: PMC3337206 DOI: 10.4161/psb.6.12.18541] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Reversible protein phosphorylation is of central importance to the proper cellular functioning of all living organisms. Catalyzed by the opposing reactions of protein kinases and phosphatases, dysfunction in reversible protein phosphorylation can result in a wide variety of cellular aberrations. In eukaryotic organisms there exists four classes of protein phosphatases, of which the PPP-family protein phosphatases have documented susceptibility to a range of protein and small molecule inhibitors. These inhibitors have been of great importance to the biochemical characterization of PPP-family protein phosphatases since their discovery, but also maintain in natura biological significance with their endogenous regulatory properties (protein inhibitors) and toxicity (small molecule inhibitors). Recently, two unique PPP-family protein phosphatases, named the Shewanella-like protein phosphatases (SLP phosphatases), from Arabidopsis thaliana were characterized and found to be phylogenetically similar to the PPP-family protein phosphatases protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A), while completely lacking sensitivity to the classic PPP-family phosphatase small molecule inhibitors okadaic acid and microcystin-LR. SLP phosphatases were also found to be absent in metazoans, but present in a wide range of bacteria, fungi and protozoa responsible for human disease. The unique biochemical properties and evolutionary heritage of SLP phosphatases suggests they could not only be potential biotechnology targets for agriculture, but may also prove to be of interest for future therapeutic drug development.
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154
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Ferrar T, Chamousset D, De Wever V, Nimick M, Andersen J, Trinkle-Mulcahy L, Moorhead GBG. Taperin (c9orf75), a mutated gene in nonsyndromic deafness, encodes a vertebrate specific, nuclear localized protein phosphatase one alpha (PP1α) docking protein. Biol Open 2011; 1:128-39. [PMID: 23213405 PMCID: PMC3507197 DOI: 10.1242/bio.2011049] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The promiscuous activity of protein phosphatase one (PP1) is controlled in the cell by associated proteins termed regulatory or targeting subunits. Using biochemical and proteomic approaches we demonstrate that the autosomal recessive nonsyndromic hearing loss gene, taperin (C9orf75), encodes a protein that preferentially docks the alpha isoform of PP1. Taperin associates with PP1 through a classic ‘RVxF’ motif and suppresses the general phosphatase activity of the enzyme. The steady-state localization of taperin is predominantly nuclear, however we demonstrate here that the protein can shuttle between the nucleus and cytoplasm and that it is found complexed to PP1 in both of these cellular compartments. Although originally identified as a hearing loss gene, Western blot analyses with taperin-specific antibodies revealed that the protein is widely expressed across mammalian tissues as multiple splice variants. Taperin is a recent proteome addition appearing during the vertebrate lineage with the PP1 binding site embedded within the most conserved region of the protein. Taperin also shares an ancestral relationship with the cytosolic actin binding protein phostensin, another PP1 interacting partner. Quantitative Stable Isotope Labeling by Amino acids in Culture (SILAC)-based mass spectrometry was employed to uncover additional taperin binding partners, and revealed an interaction with the DNA damage response proteins Ku70, Ku80, PARP and topoisomerases I and IIα. Consistent with this, we demonstrate the active recruitment of taperin to sites of DNA damage. This makes taperin a new addition to the family of PP1 targeting subunits involved in the DNA damage repair pathway.
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Affiliation(s)
- Tony Ferrar
- Department of Biological Sciences, University of Calgary , 2500 University Dr, Calgary, Alberta, T2N 1N4 , Canada
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155
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VDAC proteomics: post-translation modifications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1520-5. [PMID: 22120575 DOI: 10.1016/j.bbamem.2011.11.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 11/03/2011] [Accepted: 11/11/2011] [Indexed: 01/07/2023]
Abstract
Voltage-dependent anion channels are abundant mitochondrial outer membrane proteins expressed in three isoforms, VDAC1-3, and are considered as "mitochondrial gatekeepers". Most tissues express all three isoforms. The functions of VDACs are several-fold, ranging from metabolite and energy exchange to apoptosis. Some of these functions depend on or are affected by interaction with other proteins in the cytosol and intermembrane space. Furthermore, the function of VDACs, as well as their interaction with other proteins, is affected by posttranslational modification, mainly phosphorylation. This review summarizes recent findings on posttranslational modification of VDACs and discusses the physiological outcome of these modifications. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.
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156
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Kutuzov MA, Andreeva AV. Prediction of biological functions of Shewanella-like protein phosphatases (Shelphs) across different domains of life. Funct Integr Genomics 2011; 12:11-23. [DOI: 10.1007/s10142-011-0254-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 09/07/2011] [Accepted: 09/13/2011] [Indexed: 12/12/2022]
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157
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Computational Design of a DNA- and Fc-Binding Fusion Protein. Adv Bioinformatics 2011; 2011:457578. [PMID: 21941539 PMCID: PMC3173724 DOI: 10.1155/2011/457578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 06/16/2011] [Accepted: 06/22/2011] [Indexed: 12/23/2022] Open
Abstract
Computational design of novel proteins with well-defined functions is an ongoing topic in computational biology. In this work, we generated and optimized a new synthetic fusion protein using an evolutionary approach. The optimization was guided by directed evolution based on hydrophobicity scores, molecular weight, and secondary structure predictions. Several methods were used to refine the models built from the resulting sequences. We have successfully combined two unrelated naturally occurring binding sites, the immunoglobin Fc-binding site of the Z domain and the DNA-binding motif of MyoD bHLH, into a novel stable protein.
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158
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Franchini LF, López-Leal R, Nasif S, Beati P, Gelman DM, Low MJ, de Souza FJS, Rubinstein M. Convergent evolution of two mammalian neuronal enhancers by sequential exaptation of unrelated retroposons. Proc Natl Acad Sci U S A 2011; 108:15270-5. [PMID: 21876128 PMCID: PMC3174587 DOI: 10.1073/pnas.1104997108] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The proopiomelanocortin gene (POMC) is expressed in a group of neurons present in the arcuate nucleus of the hypothalamus. Neuron-specific POMC expression in mammals is conveyed by two distal enhancers, named nPE1 and nPE2. Previous transgenic mouse studies showed that nPE1 and nPE2 independently drive reporter gene expression to POMC neurons. Here, we investigated the evolutionary mechanisms that shaped not one but two neuron-specific POMC enhancers and tested whether nPE1 and nPE2 drive identical or complementary spatiotemporal expression patterns. Sequence comparison among representative genomes of most vertebrate classes and mammalian orders showed that nPE1 is a placental novelty. Using in silico paleogenomics we found that nPE1 originated from the exaptation of a mammalian-apparent LTR retrotransposon sometime between the metatherian/eutherian split (147 Mya) and the placental mammal radiation (≈ 90 Mya). Thus, the evolutionary origin of nPE1 differs, in kind and time, from that previously demonstrated for nPE2, which was exapted from a CORE-short interspersed nucleotide element (SINE) retroposon before the origin of prototherians, 166 Mya. Transgenic mice expressing the fluorescent markers tomato and EGFP driven by nPE1 or nPE2, respectively, demonstrated coexpression of both reporter genes along the entire arcuate nucleus. The onset of reporter gene expression guided by nPE1 and nPE2 was also identical and coincidental with the onset of Pomc expression in the presumptive mouse diencephalon. Thus, the independent exaptation of two unrelated retroposons into functional analogs regulating neuronal POMC expression constitutes an authentic example of convergent molecular evolution of cell-specific enhancers.
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Affiliation(s)
- Lucía F. Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Rodrigo López-Leal
- Centro de Estudios Científicos and Universidad Austral de Chile, Valdivia 5110466, Chile
| | - Sofía Nasif
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Paula Beati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Diego M. Gelman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48105; and
| | - Flávio J. S. de Souza
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
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159
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Miskei M, Ádám C, Kovács L, Karányi Z, Dombrádi V. Molecular evolution of phosphoprotein phosphatases in Drosophila. PLoS One 2011; 6:e22218. [PMID: 21789237 PMCID: PMC3137614 DOI: 10.1371/journal.pone.0022218] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 06/20/2011] [Indexed: 12/25/2022] Open
Abstract
Phosphoprotein phosphatases (PPP), these ancient and important regulatory enzymes are present in all eukaryotic organisms. Based on the genome sequences of 12 Drosophila species we traced the evolution of the PPP catalytic subunits and noted a substantial expansion of the gene family. We concluded that the 18–22 PPP genes of Drosophilidae were generated from a core set of 8 indispensable phosphatases that are present in most of the insects. Retropositons followed by tandem gene duplications extended the phosphatase repertoire, and sporadic gene losses contributed to the species specific variations in the PPP complement. During the course of these studies we identified 5, up till now uncharacterized phosphatase retrogenes: PpY+, PpD5+, PpD6+, Pp4+, and Pp6+ which are found only in some ancient Drosophila. We demonstrated that all of these new PPP genes exhibit a distinct male specific expression. In addition to the changes in gene numbers, the intron-exon structure and the chromosomal localization of several PPP genes was also altered during evolution. The G−C content of the coding regions decreased when a gene moved into the heterochromatic region of chromosome Y. Thus the PPP enzymes exemplify the various types of dynamic rearrangements that accompany the molecular evolution of a gene family in Drosophilidae.
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Affiliation(s)
- Márton Miskei
- Centre for Agricultural and Applied Economic Sciences, Institute of Horticultural Sciences, Department of Plant Biotechnology, University of Debrecen, Debrecen, Hungary
| | - Csaba Ádám
- Department of Medical Chemistry, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
| | - László Kovács
- Department of Medical Chemistry, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
| | - Zsolt Karányi
- First Department of Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Viktor Dombrádi
- Department of Medical Chemistry, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
- * E-mail:
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160
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Mithoe SC, Menke FLH. Phosphoproteomics perspective on plant signal transduction and tyrosine phosphorylation. PHYTOCHEMISTRY 2011; 72:997-1006. [PMID: 21315387 DOI: 10.1016/j.phytochem.2010.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 11/25/2010] [Accepted: 12/06/2010] [Indexed: 05/14/2023]
Abstract
Plants and animal cells use intricate signaling pathways to respond to a diverse array of stimuli. These stimuli include signals from environment, such as biotic and abiotic stress signals, as well as cell-to-cell signaling required for pattern formation during development. The transduction of the signal often relies on the post-translational modification (PTM) of proteins. Protein phosphorylation in eukaryotic cells is considered to be a central mechanism for regulation and cellular signaling. The classic view is that phosphorylation of serine (Ser) and threonine (Thr) residues is more abundant, whereas tyrosine (Tyr) phosphorylation is less frequent. This review provides an overview of the progress in the plant phosphoproteomics field and how this progress has lead to a re-evaluation of the relative contribution of tyrosine phosphorylation to the plant phosphoproteome. In relation to this appreciated contribution of tyrosine phosphorylation we also discuss some of the recent progress on the role of tyrosine phosphorylation in plant signal transduction.
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Affiliation(s)
- Sharon C Mithoe
- Department of Biology, Molecular Genetics, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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161
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Ghelis T. Signal processing by protein tyrosine phosphorylation in plants. PLANT SIGNALING & BEHAVIOR 2011; 6:942-51. [PMID: 21628997 PMCID: PMC3257767 DOI: 10.4161/psb.6.7.15261] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 02/22/2011] [Indexed: 05/05/2023]
Abstract
Protein phosphorylation is a reversible post-translational modification controlling many biological processes. Most phosphorylation occurs on serine and threonine, and to a less extend on tyrosine (Tyr). In animals, Tyr phosphorylation is crucial for the regulation of many responses such as growth or differentiation. Only recently with the development of mass spectrometry, it has been reported that Tyr phosphorylation is as important in plants as in animals. The genes encoding protein Tyr kinases and protein Tyr phosphatases have been identified in the Arabidopsis thaliana genome. Putative substrates of these enzymes, and thus Tyr-phosphorylated proteins have been reported by proteomic studies based on accurate mass spectrometry analysis of the phosphopeptides and phosphoproteins. Biochemical approaches, pharmacology and genetic manipulations have indicated that responses to stress and developmental processes involve changes in protein Tyr phosphorylation. The aim of this review is to present an update on Tyr phosphorylation in plants in order to better assess the role of this post-translational modification in plant physiology.
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Affiliation(s)
- Thanos Ghelis
- UPMC Université Paris 06, Sorbonne Universités, UR5 EAC 7180 CNRS, Physiologie Cellulaire et Moléculaire des Plantes, Paris, France.
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162
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Identification and characterization of AtI-2, an Arabidopsis homologue of an ancient protein phosphatase 1 (PP1) regulatory subunit. Biochem J 2011; 435:73-83. [PMID: 21222654 DOI: 10.1042/bj20101035] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PP1 (protein phosphatase 1) is among the most conserved enzymes known, with one or more isoforms present in all sequenced eukaryotic genomes. PP1 dephosphorylates specific serine/threonine phosphoproteins as defined by associated regulatory or targeting subunits. In the present study we performed a PP1-binding screen to find putative PP1 interactors in Arabidopsis thaliana and uncovered a homologue of the ancient PP1 interactor, I-2 (inhibitor-2). Bioinformatic analysis revealed remarkable conservation of three regions of plant I-2 that play key roles in binding to PP1 and regulating its function. The sequence-related properties of plant I-2 were compared across eukaryotes, indicating a lack of I-2 in some species and the emergence points from key motifs during the evolution of this ancient regulator. Biochemical characterization of AtI-2 (Arabidopsis I-2) revealed its ability to inhibit all plant PP1 isoforms and inhibitory dependence requiring the primary interaction motif known as RVXF. Arabidopsis I-2 was shown to be a phosphoprotein in vivo that was enriched in the nucleus. TAP (tandem affinity purification)-tag experiments with plant I-2 showed in vivo association with several Arabidopsis PP1 isoforms and identified other potential I-2 binding proteins.
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163
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Pereira SR, Vasconcelos VM, Antunes A. The phosphoprotein phosphatase family of Ser/Thr phosphatases as principal targets of naturally occurring toxins. Crit Rev Toxicol 2011; 41:83-110. [PMID: 21288162 DOI: 10.3109/10408444.2010.515564] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Phosphoprotein phosphatases (PPPs) constitute one of three otherwise unrelated families of enzymes that specialize in removing the phosphate group from phosphorylated serine and threonine residues. The involvement of PPP enzymes in the regulation of processes such as gene expression, DNA replication, morphogenesis, synaptic transmission, glycogen metabolism, and apoptosis has underscored their potential as targets for the treatment of a variety of conditions such as cancer, diabetes, or Alzheimer's disease. Interestingly, PPP enzymes also constitute the physiological target of multiple naturally occurring toxins, including microcystins from cyanobacteria and cantharidin from beetles. This review is devoted to the PPP family of enzymes--with a focus on the human PPPs--and the naturally occurring toxins that are known to potently impair their activity. The interaction of the toxins with the enzymes is evaluated in atomic detail to obtain insight on two complementary aspects: (1) which specific structural differences within the similarly folded catalytic core of the PPP enzymes explain their diverse sensitivities to toxin inhibition and (2) which structural features presented by the various toxins account for the differential inhibitory potency towards each PPP. These analyses take advantage of numerous site-directed mutagenesis studies, structure-activity evaluations, and recent crystallographic structures of PPPs bound to different toxins.
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Affiliation(s)
- Susana R Pereira
- CIIMAR/CIMAR-LA, Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Porto, Portugal.
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164
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Haenssler E, Isberg RR. Control of host cell phosphorylation by legionella pneumophila. Front Microbiol 2011; 2:64. [PMID: 21747787 PMCID: PMC3128975 DOI: 10.3389/fmicb.2011.00064] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 03/24/2011] [Indexed: 11/13/2022] Open
Abstract
Phosphorylation is one of the most frequent modifications in intracellular signaling and is implicated in many processes ranging from transcriptional control to signal transduction in innate immunity. Many pathogens modulate host cell phosphorylation pathways to promote growth and establish an infectious disease. The intracellular pathogen Legionella pneumophila targets and exploits the host phosphorylation system throughout the infection cycle as part of its strategy to establish an environment beneficial for replication. Key to this manipulation is the L. pneumophila Icm/Dot type IV secretion system, which translocates bacterial proteins into the host cytosol that can act directly on phosphorylation cascades. This review will focus on the different stages of L. pneumophila infection, in which host kinases and phosphatases contribute to infection of the host cell and promote intracellular survival of the pathogen. This includes the involvement of phosphatidylinositol 3-kinases during phagocytosis as well as the role of phosphoinositide metabolism during the establishment of the replication vacuole. Furthermore, L. pneumophila infection modulates the NF-κB and mitogen-activated protein kinase pathways, two signaling pathways that are central to the host innate immune response and involved in regulation of host cell survival. Therefore, L. pneumophila infection manipulates host cell signal transduction by phosphorylation at multiple levels.
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Affiliation(s)
- Eva Haenssler
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine Boston, MA, USA
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165
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Romá-Mateo C, Sacristán-Reviriego A, Beresford NJ, Caparrós-Martín JA, Culiáñez-Macià FA, Martín H, Molina M, Tabernero L, Pulido R. Phylogenetic and genetic linkage between novel atypical dual-specificity phosphatases from non-metazoan organisms. Mol Genet Genomics 2011; 285:341-54. [DOI: 10.1007/s00438-011-0611-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 02/27/2011] [Indexed: 11/29/2022]
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166
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Kinases and phosphatases in the mammalian circadian clock. FEBS Lett 2011; 585:1393-9. [DOI: 10.1016/j.febslet.2011.02.038] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 02/23/2011] [Accepted: 02/28/2011] [Indexed: 12/28/2022]
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167
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Bioinformatic identification of novel protein phosphatases in the dog genome. Mol Cell Biochem 2011; 351:149-56. [DOI: 10.1007/s11010-011-0722-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 01/05/2011] [Indexed: 12/17/2022]
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168
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Umbrasaite J, Schweighofer A, Meskiene I. Substrate analysis of Arabidopsis PP2C-type protein phosphatases. Methods Mol Biol 2011; 779:149-161. [PMID: 21837565 DOI: 10.1007/978-1-61779-264-9_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Protein phosphorylation by protein kinases can be reversed by the action of protein phosphatases. In plants, the Ser/Thr-specific phosphatases dominate among the protein phosphatase families with the type 2C protein phosphatases (PP2Cs) being the most abundant among them. PP2Cs are monomeric enzymes that require metal cations for their activity and are insensitive to known phosphatase inhibitors. PP2Cs were shown to counteract the mitogen-activated protein kinase (MAP kinase/MAPK) activities in plants and to regulate developmental and stress signaling pathways. Studies of PP2C activities can be performed in vitro using recombinant proteins. The potential substrates of PP2Cs can be tested for dephosphorylation by the phosphatase in vitro. We have found that the stress-induced PP2Cs from alfalfa and Arabidopsis interact with stress-activated MAPKs in yeast two-hybrid (Y2H) screens. Consequently, recombinant MAPKs were employed as substrates for dephosphorylation by selected PP2Cs from different family clusters. The members of the PP2C phosphatase family demonstrated specificity toward the substrate already in vitro, supporting the notion that protein phosphatases are specific enzymes. The PP2C from Arabidopsis thaliana cluster B, Arabidopsis PP2C-type phosphatase (AP2C1), and its homolog from Medicago sativa, Medicago PP2C-type phosphatase (MP2C), were able to dephosphorylate and inactivate MAPKs, whereas the ABSCISIC ACID (ABA)-INSENSITIVE 2 (ABI2) and HOMOLOGY TO ABI1 (HAB1) PP2Cs from the distinct Arabidopsis cluster A were not able to do so. The method described here can be used for the determination of PP2C protein activity and for studying the effect of mutations introduced into their catalytic domains.
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169
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Gay CM, Zygmunt T, Torres-Vázquez J. Diverse functions for the semaphorin receptor PlexinD1 in development and disease. Dev Biol 2011; 349:1-19. [PMID: 20880496 PMCID: PMC2993764 DOI: 10.1016/j.ydbio.2010.09.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 09/14/2010] [Accepted: 09/18/2010] [Indexed: 01/13/2023]
Abstract
Plexins are a family of single-pass transmembrane proteins that serve as cell surface receptors for Semaphorins during the embryonic development of animals. Semaphorin-Plexin signaling is critical for many cellular aspects of organogenesis, including cell migration, proliferation and survival. Until recently, little was known about the function of PlexinD1, the sole member of the vertebrate-specific PlexinD (PlxnD1) subfamily. Here we review novel findings about PlxnD1's roles in the development of the cardiovascular, nervous and immune systems and salivary gland branching morphogenesis and discuss new insights concerning the molecular mechanisms of PlxnD1 activity.
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Affiliation(s)
- Carl M Gay
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University Langone Medical Center, 540 First Avenue, 4th floor, lab 14, New York, NY 10016, USA
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170
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Zeqiraj E, van Aalten DMF. Pseudokinases-remnants of evolution or key allosteric regulators? Curr Opin Struct Biol 2010; 20:772-81. [PMID: 21074407 PMCID: PMC3014569 DOI: 10.1016/j.sbi.2010.10.001] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 10/05/2010] [Accepted: 10/08/2010] [Indexed: 11/18/2022]
Abstract
Protein kinases provide a platform for the integration of signal transduction networks. A key feature of transmitting these cellular signals is the ability of protein kinases to activate one another by phosphorylation. A number of kinases are predicted by sequence homology to be incapable of phosphoryl group transfer due to degradation of their catalytic motifs. These are termed pseudokinases and because of the assumed lack of phosphoryltransfer activity their biological role in cellular transduction has been mysterious. Recent structure-function studies have uncovered the molecular determinants for protein kinase inactivity and have shed light to the biological functions and evolution of this enigmatic subset of the human kinome. Pseudokinases act as signal transducers by bringing together components of signalling networks, as well as allosteric activators of active protein kinases.
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Affiliation(s)
- Elton Zeqiraj
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Room 1090, Toronto, Ontario M5G 1X5, Canada
- MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Daan MF van Aalten
- Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
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171
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A protected l-bromophosphonomethylphenylalanine amino acid derivative (BrPmp) for synthesis of irreversible protein tyrosine phosphatase inhibitors. Bioorg Med Chem 2010; 18:8679-86. [PMID: 21055952 DOI: 10.1016/j.bmc.2010.09.040] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/10/2010] [Accepted: 09/16/2010] [Indexed: 12/28/2022]
Abstract
Protein tyrosine phosphatases (PTPs) are important therapeutic targets for medicinal chemists and biochemists. General strategies for the development of inhibitors of these enzymes are needed. Several modular strategies which rely on phosphotyrosine mimics are known for PTP inhibitors. Previous strategies include phosphonomethylphenylalanine (Pmp) derivatives which act as competitive inhibitors. Pmp amino acid derivatives have been used to develop specific inhibitors by incorporation into sequences recognized by the PTP of interest. We report the synthesis of a new phosphonotyrosine analog, l-phosphonobromomethylphenylalanine (BrPmp), which acts as an inhibitor of PTPs. The BrPmp derivative was prepared as an Fmoc-protected amino acid which can be used in standard solid phase peptide synthesis (SPPS) methods. The synthesis of the protected amino acid derivative requires 11 steps from tyrosine with a 30% overall yield. Enzyme inhibition studies with the PTP CD45 demonstrate that BrPmp derivatives are irreversible inhibitors of the enzyme. A tripeptide which incorporated BrPmp had increased inhibitory potency against PTP relative to BrPmp alone, confirming that the incorporation of BrPmp into peptide sequences provides additional context to improve enzyme binding.
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172
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Kriehuber T, Rattei T, Weinmaier T, Bepperling A, Haslbeck M, Buchner J. Independent evolution of the core domain and its flanking sequences in small heat shock proteins. FASEB J 2010; 24:3633-42. [DOI: 10.1096/fj.10-156992] [Citation(s) in RCA: 183] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Thomas Kriehuber
- Munich Center for Integrated Protein ScienceDepartment Chemie TechnischeUniversität München Garching Germany
| | - Thomas Rattei
- Department of Genome Oriented Bioinformatics, Wissenschaftszentrum WeihenstephanTechnische Universität München Freising Germany
| | - Thomas Weinmaier
- Department of Genome Oriented Bioinformatics, Wissenschaftszentrum WeihenstephanTechnische Universität München Freising Germany
| | - Alexander Bepperling
- Munich Center for Integrated Protein ScienceDepartment Chemie TechnischeUniversität München Garching Germany
| | - Martin Haslbeck
- Munich Center for Integrated Protein ScienceDepartment Chemie TechnischeUniversität München Garching Germany
| | - Johannes Buchner
- Munich Center for Integrated Protein ScienceDepartment Chemie TechnischeUniversität München Garching Germany
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173
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Qiao M, Wang Y, Xu X, Lu J, Dong Y, Tao W, Stein J, Stein GS, Iglehart JD, Shi Q, Pardee AB. Mst1 Is an Interacting Protein that Mediates PHLPPs' Induced Apoptosis. Mol Cell 2010; 38:512-23. [DOI: 10.1016/j.molcel.2010.03.017] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2009] [Revised: 12/09/2009] [Accepted: 03/17/2010] [Indexed: 11/24/2022]
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174
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Grimsrud PA, Swaney DL, Wenger CD, Beauchene NA, Coon JJ. Phosphoproteomics for the masses. ACS Chem Biol 2010; 5:105-19. [PMID: 20047291 DOI: 10.1021/cb900277e] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Protein phosphorylation serves as a primary mechanism of signal transduction in the cells of biological organisms. Technical advancements over the last several years in mass spectrometry now allow for the large-scale identification and quantitation of in vivo phosphorylation at unprecedented levels. These developments have occurred in the areas of sample preparation, instrumentation, quantitative methodology, and informatics so that today, 10 000-20 000 phosphorylation sites can be identified and quantified within a few weeks. With the rapid development and widespread availability of such data, its translation into biological insight and knowledge is a current obstacle. Here we present an overview of how this technology came to be and is currently applied, as well as future challenges for the field.
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Affiliation(s)
| | | | | | - Nicole A. Beauchene
- Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Joshua J. Coon
- Departments of Chemistry
- Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
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175
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Afshar K, Werner ME, Tse YC, Glotzer M, Gönczy P. Regulation of cortical contractility and spindle positioning by the protein phosphatase 6 PPH-6 in one-cell stage C. elegans embryos. Development 2010; 137:237-47. [PMID: 20040490 DOI: 10.1242/dev.042754] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Modulation of the microtubule and the actin cytoskeleton is crucial for proper cell division. Protein phosphorylation is known to be an important regulatory mechanism modulating these cytoskeletal networks. By contrast, there is a relative paucity of information regarding how protein phosphatases contribute to such modulation. Here, we characterize the requirements for protein phosphatase PPH-6 and its associated subunit SAPS-1 in one-cell stage C. elegans embryos. We establish that the complex of PPH-6 and SAPS-1 (PPH-6/SAPS-1) is required for contractility of the actomyosin network and proper spindle positioning. Our analysis demonstrates that PPH-6/SAPS-1 regulates the organization of cortical non-muscle myosin II (NMY-2). Accordingly, we uncover that PPH-6/SAPS-1 contributes to cytokinesis by stimulating actomyosin contractility. Furthermore, we demonstrate that PPH-6/SAPS-1 is required for the proper generation of pulling forces on spindle poles during anaphase. Our results indicate that this requirement is distinct from the role in organizing the cortical actomyosin network. Instead, we uncover that PPH-6/SAPS-1 contributes to the cortical localization of two positive regulators of pulling forces, GPR-1/2 and LIN-5. Our findings provide the first insights into the role of a member of the PP6 family of phosphatases in metazoan development.
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Affiliation(s)
- Katayoun Afshar
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland
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176
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Mechanisms of protein kinase A anchoring. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 283:235-330. [PMID: 20801421 DOI: 10.1016/s1937-6448(10)83005-9] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The second messenger cyclic adenosine monophosphate (cAMP), which is produced by adenylyl cyclases following stimulation of G-protein-coupled receptors, exerts its effect mainly through the cAMP-dependent serine/threonine protein kinase A (PKA). Due to the ubiquitous nature of the cAMP/PKA system, PKA signaling pathways underlie strict spatial and temporal control to achieve specificity. A-kinase anchoring proteins (AKAPs) bind to the regulatory subunit dimer of the tetrameric PKA holoenzyme and thereby target PKA to defined cellular compartments in the vicinity of its substrates. AKAPs promote the termination of cAMP signals by recruiting phosphodiesterases and protein phosphatases, and the integration of signaling pathways by binding additional signaling proteins. AKAPs are a heterogeneous family of proteins that only display similarity within their PKA-binding domains, amphipathic helixes docking into a hydrophobic groove formed by the PKA regulatory subunit dimer. This review summarizes the current state of information on compartmentalized cAMP/PKA signaling with a major focus on structural aspects, evolution, diversity, and (patho)physiological functions of AKAPs and intends to outline newly emerging directions of the field, such as the elucidation of AKAP mutations and alterations of AKAP expression in human diseases, and the validation of AKAP-dependent protein-protein interactions as new drug targets. In addition, alternative PKA anchoring mechanisms employed by noncanonical AKAPs and PKA catalytic subunit-interacting proteins are illustrated.
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177
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Abstract
The reversible phosphorylation of proteins is accomplished by opposing activities of kinases and phosphatases. Relatively few protein serine/threonine phosphatases (PSPs) control the specific dephosphorylation of thousands of phosphoprotein substrates. Many PSPs, exemplified by protein phosphatase 1 (PP1) and PP2A, achieve substrate specificity and regulation through combinatorial interactions between conserved catalytic subunits and a large number of regulatory subunits. Other PSPs, represented by PP2C and FCP/SCP, contain both catalytic and regulatory domains within the same polypeptide chain. Here, we discuss biochemical and structural investigations that advance the mechanistic understanding of the three major classes of PSPs, with a focus on PP2A.
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Affiliation(s)
- Yigong Shi
- Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
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178
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Vlad F, Rubio S, Rodrigues A, Sirichandra C, Belin C, Robert N, Leung J, Rodriguez PL, Laurière C, Merlot S. Protein phosphatases 2C regulate the activation of the Snf1-related kinase OST1 by abscisic acid in Arabidopsis. THE PLANT CELL 2009; 21:3170-84. [PMID: 19855047 PMCID: PMC2782292 DOI: 10.1105/tpc.109.069179] [Citation(s) in RCA: 391] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2009] [Revised: 09/12/2009] [Accepted: 09/29/2009] [Indexed: 05/18/2023]
Abstract
The plant hormone abscisic acid (ABA) orchestrates plant adaptive responses to a variety of stresses, including drought. This signaling pathway is regulated by reversible protein phosphorylation, and genetic evidence demonstrated that several related protein phosphatases 2C (PP2Cs) are negative regulators of this pathway in Arabidopsis thaliana. Here, we developed a protein phosphatase profiling strategy to define the substrate preferences of the HAB1 PP2C implicated in ABA signaling and used these data to screen for putative substrates. Interestingly, this analysis designated the activation loop of the ABA activated kinase OST1, related to Snf1 and AMPK kinases, as a putative HAB1 substrate. We experimentally demonstrated that HAB1 dephosphorylates and deactivates OST1 in vitro. Furthermore, HAB1 and the related PP2Cs ABI1 and ABI2 interact with OST1 in vivo, and mutations in the corresponding genes strongly affect OST1 activation by ABA. Our results provide evidence that PP2Cs are directly implicated in the ABA-dependent activation of OST1 and further suggest that the activation mechanism of AMPK/Snf1-related kinases through the inhibition of regulating PP2Cs is conserved from plants to human.
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Affiliation(s)
- Florina Vlad
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
| | - Silvia Rubio
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, ES-46022 Valencia, Spain
| | - Americo Rodrigues
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, ES-46022 Valencia, Spain
| | - Caroline Sirichandra
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
| | - Christophe Belin
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
| | - Nadia Robert
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
| | - Jeffrey Leung
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
| | - Pedro L. Rodriguez
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, ES-46022 Valencia, Spain
| | - Christiane Laurière
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
- Address correspondence to
| | - Sylvain Merlot
- Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, UPR 2355, 91198 Gif-sur-Yvette Cedex, France
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179
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Popov D. Vascular PTPs: current developments and challenges for exploitation in Type 2 diabetes-associated vascular dysfunction. Biochem Biophys Res Commun 2009; 389:1-4. [PMID: 19715673 DOI: 10.1016/j.bbrc.2009.08.110] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 08/21/2009] [Indexed: 12/21/2022]
Abstract
Protein Tyrosine Phosphatases (PTPs) are important contributors to vascular cells normal function, by balancing signaling proteins activation exerted by phosphorylating kinases. Type 2 diabetes related insults, such as hyperglycemia, oxidative stress, and insulin resistance disturb the phosphorylation/dephosphorylation equilibrium towards an abnormal augmented phosphorylation of signaling proteins associated with changes in PTPs expression, enzymatic activity and interaction with cellular substrates. We briefly review here: (i) the new findings on receptor and non-receptor PTPs and their role in vascular cells, (ii) several data on oxidation and phosphorylation of these molecules in endothelial and smooth muscle cells, (iii) vascular PTPs intrinsic activity and dysregulation under the insults of diabetic milieu, and (iv) the potential use of PTPs and their inhibitors as therapeutic targets in Type 2 diabetes-associated vascular dysfunction.
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Affiliation(s)
- Doina Popov
- Institute of Cellular Biology and Pathology N. Simionescu, 050568 Bucharest, Romania.
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180
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Abstract
Phosphorylation plays essential roles in nearly every aspect of cell life. Protein kinases regulate signalling pathways and cellular processes that mediate metabolism, transcription, cell-cycle progression, differentiation, cytoskeleton arrangement and cell movement, apoptosis, intercellular communication, and neuronal and immunological functions. Protein kinases share a conserved catalytic domain, which catalyses the transfer of the γ-phosphate of ATP to a serine, threonine or tyrosine residue in protein substrates. The kinase can exist in an active or inactive state regulated by a variety of mechanisms in different kinases that include control by phosphorylation, regulation by additional domains that may target other molecules, binding and regulation by additional subunits, and control by protein–protein association. This Novartis Medal Lecture was delivered at a meeting on protein evolution celebrating the 200th anniversary of Charles Darwin's birth. I begin with a summary of current observations from protein sequences of kinase phylogeny. I then review the structural consequences of protein phosphorylation using our work on glycogen phosphorylase to illustrate one of the more dramatic consequences of phosphorylation. Regulation of protein phosphorylation is frequently disrupted in the diseased state, and protein kinases have become high-profile targets for drug development. Finally, I consider recent advances on protein kinases as drug targets and describe some of our recent work with CDK9 (cyclin-dependent kinase 9)–cyclin T, a regulator of transcription.
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181
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Hsu F, Schwarz S, Mougous JD. TagR promotes PpkA-catalysed type VI secretion activation in Pseudomonas aeruginosa. Mol Microbiol 2009; 72:1111-25. [PMID: 19400797 DOI: 10.1111/j.1365-2958.2009.06701.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Type VI secretion systems (T6SSs) contribute to interactions of bacterial pathogens and symbionts with their hosts. Previously, we showed that Pseudomonas aeruginosa T6S is posttranslationally activated upon phosphorylation of Fha1, an FHA domain protein, by PpkA, a membrane-spanning threonine kinase. Herein, additional structural, enzymatic and genetic requirements for PpkA-catalysed T6SS activation are identified. We found that PpkA plays an essential structural role in the T6SS, and that this role is intimately linked to its ability to promote secretion and phosphorylate Fha1. Protein localization and protein-protein interaction studies show that a complex containing Fha1 and the T6S ATPase, ClpV1 is recruited to the T6S apparatus in a phosphorylation-dependent manner. The mechanism of PpkA activation was also investigated. We identified critical PpkA autophosphorylation sites and showed that small molecule-induced dimerization of the extracellular domains of PpkA is sufficient to activate the T6SS. Finally, we discovered TagR, a component of the T6S posttranslational regulatory pathway that functions upstream of PpkA to promote kinase activity. We present a model whereby an unknown cue causes dimerization of the extracellular domains of PpkA, leading to its autophosphorylation, recruitment of the Fha1-ClpV1 complex, phosphorylation of Fha1, and T6SS activation. Our findings should facilitate approaches for identifying physiological activators of T6S.
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Affiliation(s)
- FoSheng Hsu
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
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