1
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Montaño-Rendón F, Walpole GF, Krause M, Hammond GR, Grinstein S, Fairn GD. PtdIns(3,4)P2, Lamellipodin, and VASP coordinate actin dynamics during phagocytosis in macrophages. J Cell Biol 2022; 221:e202207042. [PMID: 36165850 PMCID: PMC9521245 DOI: 10.1083/jcb.202207042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/29/2022] [Accepted: 08/31/2022] [Indexed: 11/22/2022] Open
Abstract
Phosphoinositides are pivotal regulators of vesicular traffic and signaling during phagocytosis. Phagosome formation, the initial step of the process, is characterized by local membrane remodeling and reorganization of the actin cytoskeleton that leads to formation of the pseudopods that drive particle engulfment. Using genetically encoded fluorescent probes, we found that upon particle engagement a localized pool of PtdIns(3,4)P2 is generated by the sequential activities of class I phosphoinositide 3-kinases and phosphoinositide 5-phosphatases. Depletion of this locally generated pool of PtdIns(3,4)P2 blocks pseudopod progression and ultimately phagocytosis. We show that the PtdIns(3,4)P2 effector Lamellipodin (Lpd) is recruited to nascent phagosomes by PtdIns(3,4)P2. Furthermore, we show that silencing of Lpd inhibits phagocytosis and produces aberrant pseudopodia with disorganized actin filaments. Finally, vasodilator-stimulated phosphoprotein (VASP) was identified as a key actin-regulatory protein mediating phagosome formation downstream of Lpd. Mechanistically, our findings imply that a pathway involving PtdIns(3,4)P2, Lpd, and VASP mediates phagocytosis at the stage of particle engulfment.
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Affiliation(s)
- Fernando Montaño-Rendón
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Glenn F.W. Walpole
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Matthias Krause
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, UK
| | - Gerald R.V. Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Sergio Grinstein
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - Gregory D. Fairn
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, Ontario, Canada
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
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2
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Walpole GFW, Pacheco J, Chauhan N, Clark J, Anderson KE, Abbas YM, Brabant-Kirwan D, Montaño-Rendón F, Liu Z, Zhu H, Brumell JH, Deiters A, Stephens LR, Hawkins PT, Hammond GRV, Grinstein S, Fairn GD. Kinase-independent synthesis of 3-phosphorylated phosphoinositides by a phosphotransferase. Nat Cell Biol 2022; 24:708-722. [PMID: 35484249 PMCID: PMC9107517 DOI: 10.1038/s41556-022-00895-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 03/08/2022] [Indexed: 01/10/2023]
Abstract
Despite their low abundance, phosphoinositides play a central role in membrane traffic and signalling. PtdIns(3,4,5)P3 and PtdIns(3,4)P2 are uniquely important, as they promote cell growth, survival and migration. Pathogenic organisms have developed means to subvert phosphoinositide metabolism to promote successful infection and their survival in host organisms. We demonstrate that PtdIns(3,4)P2 is a major product generated in host cells by the effectors of the enteropathogenic bacteria Salmonella and Shigella. Pharmacological, gene silencing and heterologous expression experiments revealed that, remarkably, the biosynthesis of PtdIns(3,4)P2 occurs independently of phosphoinositide 3-kinases. Instead, we found that the Salmonella effector SopB, heretofore believed to be a phosphatase, generates PtdIns(3,4)P2 de novo via a phosphotransferase/phosphoisomerase mechanism. Recombinant SopB is capable of generating PtdIns(3,4,5)P3 and PtdIns(3,4)P2 from PtdIns(4,5)P2 in a cell-free system. Through a remarkable instance of convergent evolution, bacterial effectors acquired the ability to synthesize 3-phosphorylated phosphoinositides by an ATP- and kinase-independent mechanism, thereby subverting host signalling to gain entry and even provoke oncogenic transformation.
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Affiliation(s)
- Glenn F W Walpole
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Jonathan Pacheco
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Neha Chauhan
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
| | | | | | - Yazan M Abbas
- Molecular Medicine Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | - Fernando Montaño-Rendón
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Zetao Liu
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Hongxian Zhu
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - John H Brumell
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Alexander Deiters
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | | | | | - Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Sergio Grinstein
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada.
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada.
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada.
| | - Gregory D Fairn
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada.
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada.
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada.
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3
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Montaño-Rendón F, Grinstein S, Walpole GFW. Monitoring Phosphoinositide Fluxes and Effectors During Leukocyte Chemotaxis and Phagocytosis. Front Cell Dev Biol 2021; 9:626136. [PMID: 33614656 PMCID: PMC7890364 DOI: 10.3389/fcell.2021.626136] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 01/06/2021] [Indexed: 01/22/2023] Open
Abstract
The dynamic re-organization of cellular membranes in response to extracellular stimuli is fundamental to the cell physiology of myeloid and lymphoid cells of the immune system. In addition to maintaining cellular homeostatic functions, remodeling of the plasmalemma and endomembranes endow leukocytes with the potential to relay extracellular signals across their biological membranes to promote rolling adhesion and diapedesis, migration into the tissue parenchyma, and to ingest foreign particles and effete cells. Phosphoinositides, signaling lipids that control the interface of biological membranes with the external environment, are pivotal to this wealth of functions. Here, we highlight the complex metabolic transitions that occur to phosphoinositides during several stages of the leukocyte lifecycle, namely diapedesis, migration, and phagocytosis. We describe classical and recently developed tools that have aided our understanding of these complex lipids. Finally, major downstream effectors of inositides are highlighted including the cytoskeleton, emphasizing the importance of these rare lipids in immunity and disease.
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Affiliation(s)
- Fernando Montaño-Rendón
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada
| | - Glenn F W Walpole
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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4
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Snider CE, Willet AH, Brown HT, Chen JS, Evers JM, Gould KL. Fission yeast Opy1 is an endogenous PI(4,5)P 2 sensor that binds to the phosphatidylinositol 4-phosphate 5-kinase Its3. J Cell Sci 2020; 133:jcs.247973. [PMID: 33172987 DOI: 10.1242/jcs.247973] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 10/29/2020] [Indexed: 11/20/2022] Open
Abstract
Phosphoinositides (PIPs) are a dynamic family of lipids that execute diverse roles in cell biology. PIP levels are regulated by numerous enzymes, but our understanding of how these enzymes are controlled in space and time is incomplete. One role of the PIP phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] is to anchor the cytokinetic ring (CR) to the plasma membrane (PM) in Schizosaccharomyces pombe While examining potential PI(4,5)P2-binding proteins for roles in CR anchoring, we identified the dual pleckstrin homology (PH) domain-containing protein Opy1. Although related proteins are implicated in PIP regulation, we found no role for S. pombe Opy1 in CR anchoring, which would be expected if it modulated PM PI(4,5)P2 levels. Our data indicate that although Opy1 senses PM PI(4,5)P2 levels and binds to the phosphatidylinositol 4-phosphate 5-kinase (PI5-kinase) Its3, Opy1 does not regulate Its3 kinase activity or PM PI(4,5)P2 levels, a striking difference from its Saccharomyces cerevisiae homolog. However, overexpression of Opy1 resulted in cytokinesis defects, as might be expected if it sequestered PI(4,5)P2 Our results highlight the evolutionary divergence of dual PH domain-containing proteins and the need for caution when interpreting results based on their overexpression.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Chloe E Snider
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Alaina H Willet
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - HannahSofia T Brown
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Jun-Song Chen
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Joshua M Evers
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Kathleen L Gould
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
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5
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Aβ modulates actin cytoskeleton via SHIP2-mediated phosphoinositide metabolism. Sci Rep 2019; 9:15557. [PMID: 31664099 PMCID: PMC6820556 DOI: 10.1038/s41598-019-51914-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 10/02/2019] [Indexed: 12/22/2022] Open
Abstract
Emerging evidences suggest that phospholipid metabolism is altered in Alzheimer’s disease (AD), but molecular mechanisms on how this affects neurodegeneration in AD is poorly understood. SHIP2 is a phosphoinositide-metabolizing enzyme, which dephosphorylates PI(3,4,5)P3 resulting to PI(3,4)P2, and it has been recently shown that Aβ directly increases the activity of SHIP2. Here we monitored, utilizing fluorescent SHIP2 biosensor, real-time increase of PI(3,4)P2-containing vesicles in HT22 cells treated with Aβ. Interestingly, PI(3,4)P2 is accumulated at late endosomes and lysosomal vesicles. We further discovered that ARAP3 can be attracted to PI(3,4)P2-positive mature endosomes via its PH domain and this facilitates the degradation of ARAP3. The reduced level of ARAP3 then causes RhoA hyperactivation and filamentous actin, which are critical for neurodegeneration in AD. These results provide a novel molecular link between Aβ and actin disruption through dysregulated phosphoinositide metabolism, and the SHIP2-PI(3,4)P2-ARAP3-RhoA signaling pathway can be considered as new therapeutic targets for synaptic dysfunctions in Alzheimer’s disease.
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6
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Abstract
Lipids convey both structural and functional properties to eukaryotic membranes. Understanding the basic lipid composition and the dynamics of these important molecules, in the context of cellular membranes, can shed light on signaling, metabolism, trafficking, and even membrane identity. The development of genetically encoded lipid biosensors has allowed for the visualization of specific lipids inside individual, living cells. However, a number of caveats and considerations have emerged with the overexpression of these biosensors. In this Technical Perspective, we provide a current list of available genetically encoded lipid biosensors, together with criteria that determine their veracity. We also provide some suggestions for the optimal utilization of these biosensors when both designing experiments and interpreting results.
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Affiliation(s)
- Rachel C Wills
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 16261
| | - Brady D Goulden
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 16261
| | - Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 16261
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7
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Goulden BD, Pacheco J, Dull A, Zewe JP, Deiters A, Hammond GRV. A high-avidity biosensor reveals plasma membrane PI(3,4)P 2 is predominantly a class I PI3K signaling product. J Cell Biol 2018; 218:1066-1079. [PMID: 30591513 PMCID: PMC6400549 DOI: 10.1083/jcb.201809026] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 11/20/2018] [Accepted: 12/07/2018] [Indexed: 12/21/2022] Open
Abstract
Class I phosphoinositide 3-OH kinase (PI3K) signaling is central to animal growth and metabolism, and pathological disruption of this pathway affects cancer and diabetes. However, the specific spatial/temporal dynamics and signaling roles of its minor lipid messenger, phosphatidylinositol (3,4)-bisphosphate (PI(3,4)P2), are not well understood. This owes principally to a lack of tools to study this scarce lipid. Here we developed a high-sensitivity genetically encoded biosensor for PI(3,4)P2, demonstrating high selectivity and specificity of the sensor for the lipid. We show that despite clear evidence for class II PI3K in PI(3,4)P2-driven function, the overwhelming majority of the lipid accumulates through degradation of class I PI3K-produced PIP3 However, we show that PI(3,4)P2 is also subject to hydrolysis by the tumor suppressor lipid phosphatase PTEN. Collectively, our results show that PI(3,4)P2 is potentially an important driver of class I PI3K-driven signaling and provides powerful new tools to begin to resolve the biological functions of this lipid downstream of class I and II PI3K.
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Affiliation(s)
- Brady D Goulden
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Jonathan Pacheco
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Allyson Dull
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - James P Zewe
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | | | - Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
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8
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Scacioc A, Schmidt C, Hofmann T, Urlaub H, Kühnel K, Pérez-Lara Á. Structure based biophysical characterization of the PROPPIN Atg18 shows Atg18 oligomerization upon membrane binding. Sci Rep 2017; 7:14008. [PMID: 29070817 PMCID: PMC5656675 DOI: 10.1038/s41598-017-14337-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 09/19/2017] [Indexed: 11/29/2022] Open
Abstract
PROPPINs (β-propellers that bind polyphosphoinositides) are PtdIns3P and PtdIns(3,5)P2 binding autophagy related proteins. They contain two phosphatidylinositolphosphate (PIP) binding sites and a conserved FRRG motif is essential for PIP binding. Here we present the 2.0 Å resolution crystal structure of the PROPPIN Atg18 from Pichia angusta. We designed cysteine mutants for labelling with the fluorescence dyes to probe the distances of the mutants to the membrane. These measurements support a model for PROPPIN-membrane binding, where the PROPPIN sits in a perpendicular or slightly tilted orientation on the membrane. Stopped-flow measurements suggest that initial PROPPIN-membrane binding is driven by non-specific PIP interactions. The FRRG motif then retains the protein in the membrane by binding two PIP molecules as evident by a lower dissociation rate for Atg18 in comparison with its PIP binding deficient FTTG mutant. We demonstrate that the amine-specific cross-linker Bis(sulfosuccinimidyl)suberate (BS3), which is used for protein-protein cross-linking can also be applied for cross-linking proteins and phosphatidylethanolamine (PE). Cross-linking experiments with liposome bound Atg18 yielded several PE cross-linked peptides. We also observed intermolecular cross-linked peptides, which indicated Atg18 oligomerization. FRET-based stopped-flow measurements revealed that Atg18 rapidly oligomerizes upon membrane binding while it is mainly monomeric in solution.
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Affiliation(s)
- Andreea Scacioc
- Research Group Autophagy, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany
| | - Carla Schmidt
- Interdisciplinary research center HALOmem, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120, Halle, Germany. .,Bioanalytical Mass Spectrometry Group, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.
| | - Tommy Hofmann
- Interdisciplinary research center HALOmem, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120, Halle, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.,Bioanalytics Group, University Medical Center Göttingen, Robert-Koch-Strasse 40, 37075, Göttingen, Germany
| | - Karin Kühnel
- Research Group Autophagy, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany. .,Nature Communications, 4 Crinan Street, London, N1 9XW, United Kingdom.
| | - Ángel Pérez-Lara
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.
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9
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De Craene JO, Bertazzi DL, Bär S, Friant S. Phosphoinositides, Major Actors in Membrane Trafficking and Lipid Signaling Pathways. Int J Mol Sci 2017; 18:ijms18030634. [PMID: 28294977 PMCID: PMC5372647 DOI: 10.3390/ijms18030634] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 03/02/2017] [Accepted: 03/06/2017] [Indexed: 11/30/2022] Open
Abstract
Phosphoinositides are lipids involved in the vesicular transport of proteins and lipids between the different compartments of eukaryotic cells. They act by recruiting and/or activating effector proteins and thus are involved in regulating various cellular functions, such as vesicular budding, membrane fusion and cytoskeleton dynamics. Although detected in small concentrations in membranes, their role is essential to cell function, since imbalance in their concentrations is a hallmark of many cancers. Their synthesis involves phosphorylating/dephosphorylating positions D3, D4 and/or D5 of their inositol ring by specific lipid kinases and phosphatases. This process is tightly regulated and specific to the different intracellular membranes. Most enzymes involved in phosphoinositide synthesis are conserved between yeast and human, and their loss of function leads to severe diseases (cancer, myopathy, neuropathy and ciliopathy).
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Affiliation(s)
- Johan-Owen De Craene
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Dimitri L Bertazzi
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Séverine Bär
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
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10
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Kuang G, Bulone V, Tu Y. Computational studies of the binding profile of phosphoinositide PtdIns (3,4,5) P₃ with the pleckstrin homology domain of an oomycete cellulose synthase. Sci Rep 2016; 6:20555. [PMID: 26857031 PMCID: PMC4746654 DOI: 10.1038/srep20555] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 01/06/2016] [Indexed: 12/05/2022] Open
Abstract
Saprolegnia monoica is a model organism to investigate Saprolegnia parasitica, an important oomycete which causes considerable loss in aquaculture every year. S. monoica contains cellulose synthases vital for oomycete growth. However, the molecular mechanism of the cellulose biosynthesis process in the oomycete growth is still poorly understood. Some cellulose synthases of S. monoica, such as SmCesA2, are found to contain a plecsktrin homology (PH) domain, which is a protein module widely found in nature and known to bind to phosphoinositides, a class of signaling compounds involved in many biological processes. Understanding the molecular interactions between the PH domain and phosphoinositides would help to unravel the cellulose biosynthesis process of oomycetes. In this work, the binding profile of PtdIns (3,4,5) P3, a typical phosphoinositide, with SmCesA2-PH was studied by molecular docking, molecular dynamics and metadynamics simulations. PtdIns (3,4,5) P3 is found to bind at a specific site located at β1, β2 and β1-β2 loop of SmCesA2-PH. The high affinity of PtdIns (3,4,5) P3 to SmCesA2-PH is contributed by the free phosphate groups, which have electrostatic and hydrogen-bond interactions with Lys88, Lys100 and Arg102 in the binding site.
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Affiliation(s)
- Guanglin Kuang
- Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Center, Stockholm, 106 91, Sweden
| | - Vincent Bulone
- Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Center, Stockholm, 106 91, Sweden
| | - Yaoquan Tu
- Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Center, Stockholm, 106 91, Sweden
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11
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Membrane and Protein Interactions of the Pleckstrin Homology Domain Superfamily. MEMBRANES 2015; 5:646-63. [PMID: 26512702 PMCID: PMC4704004 DOI: 10.3390/membranes5040646] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/15/2015] [Accepted: 10/16/2015] [Indexed: 12/23/2022]
Abstract
The human genome encodes about 285 proteins that contain at least one annotated pleckstrin homology (PH) domain. As the first phosphoinositide binding module domain to be discovered, the PH domain recruits diverse protein architectures to cellular membranes. PH domains constitute one of the largest protein superfamilies, and have diverged to regulate many different signaling proteins and modules such as Dbl homology (DH) and Tec homology (TH) domains. The ligands of approximately 70 PH domains have been validated by binding assays and complexed structures, allowing meaningful extrapolation across the entire superfamily. Here the Membrane Optimal Docking Area (MODA) program is used at a genome-wide level to identify all membrane docking PH structures and map their lipid-binding determinants. In addition to the linear sequence motifs which are employed for phosphoinositide recognition, the three dimensional structural features that allow peripheral membrane domains to approach and insert into the bilayer are pinpointed and can be predicted ab initio. The analysis shows that conserved structural surfaces distinguish which PH domains associate with membrane from those that do not. Moreover, the results indicate that lipid-binding PH domains can be classified into different functional subgroups based on the type of membrane insertion elements they project towards the bilayer.
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12
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Chen L, Du-Cuny L, Moses S, Dumas S, Song Z, Rezaeian AH, Lin HK, Meuillet EJ, Zhang S. Novel inhibitors induce large conformational changes of GAB1 pleckstrin homology domain and kill breast cancer cells. PLoS Comput Biol 2015; 11:e1004021. [PMID: 25569504 PMCID: PMC4287437 DOI: 10.1371/journal.pcbi.1004021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Accepted: 07/25/2014] [Indexed: 12/05/2022] Open
Abstract
The Grb2-associated binding protein 1 (GAB1) integrates signals from different signaling pathways and is over-expressed in many cancers, therefore representing a new therapeutic target. In the present study, we aim to target the pleckstrin homology (PH) domain of GAB1 for cancer treatment. Using homology models we derived, high-throughput virtual screening of five million compounds resulted in five hits which exhibited strong binding affinities to GAB1 PH domain. Our prediction of ligand binding affinities is also in agreement with the experimental KD values. Furthermore, molecular dynamics studies showed that GAB1 PH domain underwent large conformational changes upon ligand binding. Moreover, these hits inhibited the phosphorylation of GAB1 and demonstrated potent, tumor-specific cytotoxicity against MDA-MB-231 and T47D breast cancer cell lines. This effort represents the discovery of first-in-class GAB1 PH domain inhibitors with potential for targeted breast cancer therapy and provides novel insights into structure-based approaches to targeting this protein. In this paper, we described the identification and evaluation of a set of first-in-class potent inhibitors targeting a new cancer target, Grb2-associated binder-1 (GAB1), which integrates signals from different signaling pathways, and is frequently over-expressed in cancer cells. To achieve our goals, we have employed intensive computational modeling to understand the structure of the GAB1 pleckstrin homology (PH) domain and screened five million compounds. Upon biological evaluation, we found that several inhibitors that induced large conformational changes of the target structure exhibited strong selective binding to GAB1 PH domain. Particularly, these inhibitors demonstrated potent and tumor-specific cytotoxicity in breast cancer cells. This represents a groundbreaking discovery in targeting GAB1 signaling which may be used for cancer therapy, especially for triple negative breast cancer patients.
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Affiliation(s)
- Lu Chen
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Lei Du-Cuny
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Sylvestor Moses
- Departments of Nutritional Sciences and Molecular and Cellular Biology, the University of Arizona Cancer Center, Tucson, Arizona, United States of America
| | - Sabrina Dumas
- Departments of Nutritional Sciences and Molecular and Cellular Biology, the University of Arizona Cancer Center, Tucson, Arizona, United States of America
| | - Zuohe Song
- Departments of Nutritional Sciences and Molecular and Cellular Biology, the University of Arizona Cancer Center, Tucson, Arizona, United States of America
| | - Abdol Hossein Rezaeian
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Hui-Kuan Lin
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Emmanuelle J. Meuillet
- Departments of Nutritional Sciences and Molecular and Cellular Biology, the University of Arizona Cancer Center, Tucson, Arizona, United States of America
- * E-mail: (EJM); (SZ)
| | - Shuxing Zhang
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- * E-mail: (EJM); (SZ)
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13
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Specificity and Commonality of the Phosphoinositide-Binding Proteome Analyzed by Quantitative Mass Spectrometry. Cell Rep 2014; 6:578-91. [DOI: 10.1016/j.celrep.2013.12.038] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 12/03/2013] [Accepted: 12/26/2013] [Indexed: 01/03/2023] Open
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14
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Shi H, Hong A, Kong X, Koya RC, Song C, Moriceau G, Hugo W, Yu CC, Ng C, Chodon T, Scolyer RA, Kefford RF, Ribas A, Long GV, Lo RS. A novel AKT1 mutant amplifies an adaptive melanoma response to BRAF inhibition. Cancer Discov 2013; 4:69-79. [PMID: 24265152 DOI: 10.1158/2159-8290.cd-13-0279] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BRAF inhibitor (BRAFi) therapy leads to remarkable anti melanoma responses, but the initial tumor shrinkage is commonly incomplete, providing a nidus for subsequent disease progression. Adaptive signaling may underlie early BRAFi resistance and influence the selection pattern for genetic variants, causing late, acquired resistance. We show here that BRAFi (or BRAFi + MEKi) therapy in patients frequently led to rebound phosphorylated AKT (p-AKT) levels in their melanomas early on-treatment. In cell lines, BRAFi treatment led to rebound levels of receptor tyrosine kinases (RTK; including PDGFRβ), phosphatidyl (3,4,5)-triphosphate (PIP3), pleckstrin homology domain recruitment, and p-AKT. PTEN expression limited this BRAFi-elicited PI3K-AKT signaling, which could be rescued by the introduction of a mutant AKT1 (Q79K) known to confer acquired BRAFi resistance. Functionally, AKT1(Q79K) conferred BRAFi resistance via amplification of BRAFi-elicited PI3K-AKT signaling. In addition, mitogen-activated protein kinase pathway inhibition enhanced clonogenic growth dependency on PI3K or AKT. Thus, adaptive or genetic upregulation of AKT critically participates in melanoma survival during BRAFi therapy.
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Affiliation(s)
- Hubing Shi
- 1The Division of Dermatology, Department of Medicine, 2Division of Surgical Oncology, Department of Surgery, 3Division of Hematology and Oncology, Department of Medicine, 4Jonsson Comprehensive Cancer Center, 5Department of Molecular and Medical Pharmacology, 6David Geffen School of Medicine, University of California, Los Angeles, California; 7Melanoma Institute of Australia, 8Royal Prince Alfred Hospital, 9Westmead Millennium Institute, and 10Westmead Hospital, University of Sydney, New South Wales, Australia
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15
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Shi H, Hugo W, Kong X, Hong A, Koya RC, Moriceau G, Chodon T, Guo R, Johnson DB, Dahlman KB, Kelley MC, Kefford RF, Chmielowski B, Glaspy JA, Sosman JA, van Baren N, Long GV, Ribas A, Lo RS. Acquired resistance and clonal evolution in melanoma during BRAF inhibitor therapy. Cancer Discov 2013; 4:80-93. [PMID: 24265155 DOI: 10.1158/2159-8290.cd-13-0642] [Citation(s) in RCA: 760] [Impact Index Per Article: 69.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BRAF inhibitors elicit rapid antitumor responses in the majority of patients with BRAF(V600)-mutant melanoma, but acquired drug resistance is almost universal. We sought to identify the core resistance pathways and the extent of tumor heterogeneity during disease progression. We show that mitogen-activated protein kinase reactivation mechanisms were detected among 70% of disease-progressive tissues, with RAS mutations, mutant BRAF amplification, and alternative splicing being most common. We also detected PI3K-PTEN-AKT-upregulating genetic alterations among 22% of progressive melanomas. Distinct molecular lesions in both core drug escape pathways were commonly detected concurrently in the same tumor or among multiple tumors from the same patient. Beyond harboring extensively heterogeneous resistance mechanisms, melanoma regrowth emerging from BRAF inhibitor selection displayed branched evolution marked by altered mutational spectra/signatures and increased fitness. Thus, melanoma genomic heterogeneity contributes significantly to BRAF inhibitor treatment failure, implying upfront, cotargeting of two core pathways as an essential strategy for durable responses.
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Affiliation(s)
- Hubing Shi
- Division of Dermatology, Department of Medicine.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Willy Hugo
- Division of Dermatology, Department of Medicine.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Xiangju Kong
- Division of Dermatology, Department of Medicine.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Aayoung Hong
- Division of Dermatology, Department of Medicine.,Department of Molecular and Medical Pharmacology.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Richard C Koya
- Division of Surgical Oncology, Department of Surgery.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Gatien Moriceau
- Division of Dermatology, Department of Medicine.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Thinle Chodon
- Division of Hematology & Oncology, Department of Medicine.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Rongqing Guo
- Division of Hematology & Oncology, Department of Medicine.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Douglas B Johnson
- Department of Medicine.,Vanderbilt-Ingram Cancer Center, Nashville, TN 37232
| | - Kimberly B Dahlman
- Department of Cancer Biology.,Vanderbilt-Ingram Cancer Center, Nashville, TN 37232
| | - Mark C Kelley
- Department of Surgery.,Vanderbilt-Ingram Cancer Center, Nashville, TN 37232
| | - Richard F Kefford
- Melanoma Institute of Australia, Westmead Millenium Institute, Westmead Hospital, University of Sydney, New South Wales, Australia
| | - Bartosz Chmielowski
- Division of Hematology & Oncology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - John A Glaspy
- Division of Hematology & Oncology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Jeffrey A Sosman
- Department of Medicine.,Vanderbilt-Ingram Cancer Center, Nashville, TN 37232
| | | | - Georgina V Long
- Melanoma Institute of Australia, Westmead Millenium Institute, Westmead Hospital, University of Sydney, New South Wales, Australia
| | - Antoni Ribas
- Division of Dermatology, Department of Medicine.,Division of Hematology & Oncology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,Department of Molecular and Medical Pharmacology.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
| | - Roger S Lo
- Division of Dermatology, Department of Medicine.,Jonsson Comprehensive Cancer Center.,Department of Molecular and Medical Pharmacology.,David Geffen School of Medicine, University of California, LA, California 90095-1662 USA
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16
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Ueda Y, Kwok S, Hayashi Y. Application of FRET probes in the analysis of neuronal plasticity. Front Neural Circuits 2013; 7:163. [PMID: 24133415 PMCID: PMC3794420 DOI: 10.3389/fncir.2013.00163] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 09/23/2013] [Indexed: 12/12/2022] Open
Abstract
Breakthroughs in imaging techniques and optical probes in recent years have revolutionized the field of life sciences in ways that traditional methods could never match. The spatial and temporal regulation of molecular events can now be studied with great precision. There have been several key discoveries that have made this possible. Since green fluorescent protein (GFP) was cloned in 1992, it has become the dominant tracer of proteins in living cells. Then the evolution of color variants of GFP opened the door to the application of Förster resonance energy transfer (FRET), which is now widely recognized as a powerful tool to study complicated signal transduction events and interactions between molecules. Employment of fluorescent lifetime imaging microscopy (FLIM) allows the precise detection of FRET in small subcellular structures such as dendritic spines. In this review, we provide an overview of the basic and practical aspects of FRET imaging and discuss how different FRET probes have revealed insights into the molecular mechanisms of synaptic plasticity and enabled visualization of neuronal network activity both in vitro and in vivo.
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PIP₃ regulates spinule formation in dendritic spines during structural long-term potentiation. J Neurosci 2013; 33:11040-7. [PMID: 23825409 DOI: 10.1523/jneurosci.3122-12.2013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Dendritic spines are small, highly motile structures on dendritic shafts that provide flexibility to neuronal networks. Spinules are small protrusions that project from spines. The number and the length of spinules increase in response to activity including theta burst stimulation and glutamate application. However, what function spinules exert and how their formation is regulated still remains unclear. Phosphatidylinositol-3,4,5-trisphosphate (PIP₃) plays important roles in cell motility such as filopodia and lamellipodia by recruiting downstream proteins such as Akt and WAVE to the membrane, respectively. Here we reveal that PIP₃ regulates spinule formation during structural long-term potentiation (sLTP) of single spines in CA1 pyramidal neurons of hippocampal slices from rats. Since the local distribution of PIP₃ is important to exert its functions, the subcellular distribution of PIP₃ was investigated using a fluorescence lifetime-based PIP₃ probe. PIP₃ accumulates to a greater extent in spines than in dendritic shafts, which is regulated by the subcellular activity pattern of proteins that produce and degrade PIP₃. Subspine imaging revealed that when sLTP was induced in a single spine, PIP₃ accumulates in the spinule whereas PIP₃ concentration in the spine decreased.
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18
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Sugiki T, Takeuchi K, Yamaji T, Takano T, Tokunaga Y, Kumagai K, Hanada K, Takahashi H, Shimada I. Structural basis for the Golgi association by the pleckstrin homology domain of the ceramide trafficking protein (CERT). J Biol Chem 2012; 287:33706-18. [PMID: 22869376 DOI: 10.1074/jbc.m112.367730] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ceramide transport from the endoplasmic reticulum to the Golgi apparatus is crucial in sphingolipid biosynthesis, and the process relies on the ceramide trafficking protein (CERT), which contains pleckstrin homology (PH) and StAR-related lipid transfer domains. The CERT PH domain specifically recognizes phosphatidylinositol 4-monophosphate (PtdIns(4)P), a characteristic phosphoinositide in the Golgi membrane, and is indispensable for the endoplasmic reticulum-to-Golgi transport of ceramide by CERT. In this study, we determined the three-dimensional structure of the CERT PH domain by using solution NMR techniques. The structure revealed the presence of a characteristic basic groove near the canonical PtdIns(4)P recognition site. An extensive interaction study using NMR and other biophysical techniques revealed that the basic groove coordinates the CERT PH domain for efficient PtdIns(4)P recognition and localization in the Golgi apparatus. The notion was also supported by Golgi mislocalization of the CERT mutants in living cells. The distinctive binding modes reflect the functions of PH domains, as the basic groove is conserved only in the PH domains involved with the PtdIns(4)P-dependent lipid transport activity but not in those with the signal transduction activity.
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Affiliation(s)
- Toshihiko Sugiki
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
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19
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van Gisbergen PAC, Li M, Wu SZ, Bezanilla M. Class II formin targeting to the cell cortex by binding PI(3,5)P(2) is essential for polarized growth. ACTA ACUST UNITED AC 2012; 198:235-50. [PMID: 22801781 PMCID: PMC3410418 DOI: 10.1083/jcb.201112085] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
PI(3,5)P2 is directly linked to generation and remodeling of the cortical actin array by formin during polarized cell growth in plants. Class II formins are key regulators of actin and are essential for polarized plant cell growth. Here, we show that the class II formin N-terminal phosphatase and tensin (PTEN) domain binds phosphoinositide-3,5-bisphosphate (PI(3,5)P2). Replacing the PTEN domain with polypeptides of known lipid-binding specificity, we show that PI(3,5)P2 binding was required for formin-mediated polarized growth. Via PTEN, formin also localized to the cell apex, phragmoplast, and to the cell cortex as dynamic cortical spots. We show that the cortical localization driven by binding to PI(3,5)P2 was required for function. Silencing the kinases that produce PI(3,5)P2 reduced cortical targeting of formin and inhibited polarized growth. We show a subset of cortical formin spots moved in actin-dependent linear trajectories. We observed that the linearly moving subpopulation of cortical formin generated new actin filaments de novo and along preexisting filaments, providing evidence for formin-mediated actin bundling in vivo. Taken together, our data directly link PI(3,5)P2 to generation and remodeling of the cortical actin array.
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20
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Abstract
Phosphoinositides are important regulators of cellular homoeostasis and numerous signal-transduction pathways. One of their major features is their ability to recruit signalling proteins to membranes by direct interaction with phosphoinositide-binding modules. The distribution and dynamics of membrane phosphoinositides are therefore major determinants in the spatiotemporal control of cell signalling and membrane trafficking. However, standard biochemical approaches cannot reveal the dynamics of phosphoinositides at the single-cell level. A major technical advance has been the development of genetically encoded fluorescent phosphoinositide probes on the basis of the phosphoinositide-binding domains found in signalling proteins, such as the PH (pleckstrin homology) domain. This review describes the diverse fluorescent phosphoinositide probes available for imaging specific phosphoinositide species and how their use has improved the understanding of phosphoinositide signalling at the single-cell level.
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Affiliation(s)
- Guillaume Halet
- Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK.
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21
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Role of TAPP1 and TAPP2 adaptor binding to PtdIns(3,4)P2 in regulating insulin sensitivity defined by knock-in analysis. Biochem J 2011; 434:265-74. [PMID: 21204784 DOI: 10.1042/bj20102012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insulin sensitivity is critically dependent on the activity of PI3K (phosphoinositide 3-kinase) and generation of the PtdIns(3,4,5)P(3) second messenger. PtdIns(3,4,5)P(3) can be broken down to PtdIns(3,4)P(2) through the action of the SHIPs (Src-homology-2-domain-containing inositol phosphatases). As PtdIns(3,4)P(2) levels peak after those of PtdIns(3,4,5)P(3), it has been proposed that PtdIns(3,4)P(2) controls a negative-feedback loop that down-regulates the insulin and PI3K network. Previously, we identified two related adaptor proteins termed TAPP [tandem PH (pleckstrin homology)-domain-containing protein] 1 and TAPP2 that specifically bind to PtdIns(3,4)P(2) through their C-terminal PH domain. To determine whether TAPP1 and TAPP2 play a role in regulating insulin sensitivity, we generated knock-in mice that express normal endogenous levels of mutant TAPP1 and TAPP2 that are incapable of binding PtdIns(3,4)P(2). These homozygous TAPP1(R211L/R211L) TAPP2(R218L/R218L) double knock-in mice are viable and exhibit significantly enhanced activation of Akt, a key downstream mediator of insulin signalling. Consistent with increased PI3K and Akt activity, the double knock-in mice display enhanced whole body insulin sensitivity and disposal of glucose uptake into muscle tissues. We also generated wild-type and double TAPP1(R211L/R211L) TAPP2(R218L/R218L) knock-in embryonic fibroblasts and found that insulin triggered enhanced production of PtdIns(3,4,5)P(3) and Akt activity in the double knock-in fibroblasts. These observations provide the first genetic evidence to support the notion that binding of TAPP1 and TAPP2 adap-tors to PtdIns(3,4)P(2) function as negative regulators of the insulin and PI3K signalling pathways.
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22
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Perino J, Crouzier D, Spehner D, Debouzy JC, Garin D, Crance JM, Favier AL. Lung surfactant DPPG phospholipid inhibits vaccinia virus infection. Antiviral Res 2010; 89:89-97. [PMID: 21095206 DOI: 10.1016/j.antiviral.2010.11.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 11/03/2010] [Accepted: 11/14/2010] [Indexed: 10/18/2022]
Abstract
Vaccinia virus (VACV) was used as a surrogate of Variola virus (genus Orthopoxvirus), the causative agent of smallpox, to study orthopoxvirus infection via the respiratory airway. Lung surfactant, a physiological barrier to infection encountered by the virus, is predominantly composed of phospholipids whose role during orthopoxvirus infection has not been investigated. An attenuated Lister strain, derived from the traditional smallpox vaccine and the Western Reserve (WR) strain, lethal for mice infected by the respiratory route, were examined for their ability to bind various surfactant phospholipids. Dipalmitoyl phosphatidylglycerol (DPPG) was found to interact with both VACV strains. DPPG incorporated in small unilamellar vesicle (SUV-DPPG) inhibited VACV cell infection, unlike other phospholipids tested. Both pre-incubation of virus with SUV-DPPG and pretreatment of the cell with SUV-DPPG inhibited cell infection. This specific DPPG effect was shown to be concentration and time dependent and to prevent the first step of the viral cycle, i.e. virus cell attachment. Cryo-electron microscopy highlighted the interaction between the virus and SUV-DPPG. In the presence of the phospholipid, virus particles displayed a hedgehog-like appearance due to the attachment of lipid vesicles. Mice infected intranasally with VACV-WR pre-incubated with SUV-DPPG survived a lethal infection. These data suggest that DPPG in lung surfactant could reduce the amount of orthopoxvirus particles able to infect pneumocytes at the beginning of a respiratory poxvirus infection. The knowledge acquired during this study of virus-DPPG interactions may be used to develop novel chemotherapeutic strategies for smallpox.
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Affiliation(s)
- Julien Perino
- Laboratoire de Virologie, Institut de Recherche Biomédicale des Armées-Antenne du Centre de Recherches du Service de Santé des Armées, 38702 La Tronche Cedex, France
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23
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Hou S, Pauls SD, Liu P, Marshall AJ. The PH domain adaptor protein Bam32/DAPP1 functions in mast cells to restrain FcɛRI-induced calcium flux and granule release. Mol Immunol 2010; 48:89-97. [PMID: 20956018 DOI: 10.1016/j.molimm.2010.09.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 09/07/2010] [Accepted: 09/14/2010] [Indexed: 12/12/2022]
Abstract
Mast cell activation triggered by IgE binding to its high affinity receptor FcɛRI is highly dependent on signaling via phosphoinositde 3-kinases (PI3K). The phosphoinositide phosphatase SHIP controls mast cell activation by regulating accumulation of D3 phosphoinositide second messengers generated by PI3K. The PH domain adaptor protein Bam32/DAPP1 binds specifically to the D3 phosphoinositides PI(3,4,5)P3 and PI(3,4)P2 (the substrate and product of SHIP respectively). In B cells, Bam32 is phosphorylated by Src family kinases including Lyn, and is required for antigen receptor-induced activation; however the function of Bam32 in mast cells is unknown. Here we report that Bam32 is expressed in mast cells, is recruited to the plasma membrane upon stimulation and functions in FcɛRI signaling. Examination of bone marrow-derived mast cells (BMMC) isolated from Bam32-deficient mice revealed enhanced FcɛRI-induced degranulation and IL-6 production, indicating that Bam32 may function to restrain signaling via FcɛRI. These enhanced degranulation responses were PI3K-dependent, as indicated by blockade with PI3K inhibitors wortmannin or IC87114. While Bam32-deficient BMMC showed reduced FcɛRI-induced activation of mitogen-activated protein kinases ERK and JNK, FcɛRI-induced calcium flux and phosphorylation of PLCγ1 and Akt were increased. Bam32-deficient BMMC showed significantly reduced phosphorylation of Lyn and SHIP, indicating reduced activity of inhibitory signaling pathways. Together our results identify Bam32 as a novel regulator of mast cell activation, potentially functioning in membrane-proximal integration of positive and negative signaling pathways.
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Affiliation(s)
- Sen Hou
- Department of Immunology, University of Manitoba, Winnipeg, MB R3E 0W3, Canada
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24
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Campa F, Yoon HY, Ha VL, Szentpetery Z, Balla T, Randazzo PA. A PH domain in the Arf GTPase-activating protein (GAP) ARAP1 binds phosphatidylinositol 3,4,5-trisphosphate and regulates Arf GAP activity independently of recruitment to the plasma membranes. J Biol Chem 2009; 284:28069-28083. [PMID: 19666464 DOI: 10.1074/jbc.m109.028266] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARAP1 is a phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3))-dependent Arf GTPase-activating protein (GAP) with five PH domains that regulates endocytic trafficking of the epidermal growth factor receptor (EGFR). Two tandem PH domains are immediately N-terminal of the Arf GAP domain, and one of these fits the consensus sequence for PtdIns(3,4,5)P(3) binding. Here, we tested the hypothesis that PtdIns(3,4,5)P(3)-dependent recruitment mediated by the first PH domain of ARAP1 regulates the in vivo and in vitro function of ARAP1. We found that PH1 of ARAP1 specifically bound to PtdIns(3,4,5)P(3), but with relatively low affinity (approximately 1.6 microm), and the PH domains did not mediate PtdIns(3,4,5)P(3)-dependent recruitment to membranes in cells. However, PtdIns(3,4,5)P(3) binding to the PH domain stimulated GAP activity and was required for in vivo function of ARAP1 as a regulator of endocytic trafficking of the EGFR. Based on these results, we propose a variation on the model for the function of phosphoinositide-binding PH domains. In our model, ARAP1 is recruited to membranes independently of PtdIns(3,4,5)P(3), the subsequent production of which triggers enzymatic activity.
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Affiliation(s)
- Fanny Campa
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Hye-Young Yoon
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Vi Luan Ha
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Zsofia Szentpetery
- Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Tamas Balla
- Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
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25
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Balla T, Várnai P. Visualization of cellular phosphoinositide pools with GFP-fused protein-domains. CURRENT PROTOCOLS IN CELL BIOLOGY 2009; Chapter 24:Unit 24.4. [PMID: 19283730 PMCID: PMC3125592 DOI: 10.1002/0471143030.cb2404s42] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This unit describes the method of following phosphoinositide dynamics in live cells. Inositol phospholipids have emerged as universal signaling molecules present in virtually every membrane of eukaryotic cells. Phosphoinositides are present in only tiny amounts as compared to structural lipids, but they are metabolically very active as they are produced and degraded by the numerous inositide kinase and phosphatase enzymes. Phosphoinositides control the membrane recruitment and activity of many membrane protein signaling complexes in specific membrane compartments, and they have been implicated in the regulation of a variety of signaling and trafficking pathways. It has been a challenge to develop methods that allow detection of phosphoinositides at the single-cell level. The only available technique in live cell applications is based on the use of the same protein domains selected by evolution to recognize cellular phosphoinositides. Some of these isolated protein modules, when fused to fluorescent proteins, can follow dynamic changes in phosphoinositides. While this technique can provide information on phosphoinositide dynamics in live cells with subcellular localization, and it has rapidly gained popularity, it also has several limitations that must be taken into account when interpreting the data. This unit summarizes the design and practical use of these constructs and also reviews important considerations for interpretation of the data obtained by this technique.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, MD 20892 USA
| | - Péter Várnai
- Department of Physiology, Semmelweis University Medical School, Budapest, Hungary
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26
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Park WS, Heo WD, Whalen JH, O'Rourke NA, Bryan HM, Meyer T, Teruel MN. Comprehensive identification of PIP3-regulated PH domains from C. elegans to H. sapiens by model prediction and live imaging. Mol Cell 2008; 30:381-92. [PMID: 18471983 DOI: 10.1016/j.molcel.2008.04.008] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 12/25/2007] [Accepted: 04/23/2008] [Indexed: 01/25/2023]
Abstract
Phosphoinositide 3-kinase (PI3K) and its product phosphatidylinositol(3,4,5)-trisphosphate (PIP3) control cell growth, migration, and other processes by recruiting proteins with pleckstrin homology (PH) domains and possibly other domains to the plasma membrane (PM). However, previous experimental and structural work with PH domains left conflicting evidence about which ones are PIP3 regulated. Here we used live-cell confocal imaging of 130 YFP-conjugated mouse PH domains and found that 20% translocated to the PM in response to receptor-generated PIP3 production. We developed a recursive-learning algorithm to predict PIP3 regulation of 1200 PH domains from different eukaryotes and validated that it accurately predicts PIP3 regulation. Strikingly, this algorithm showed that PIP3 regulation is specified by amino acids across the PH domain, not just the PIP3-binding pocket, and must have evolved several times independently from PIP3-insensitive ancestral PH domains. Finally, our algorithm and live-cell experiments provide a functional survey of PH domains in different species, showing that PI3K regulation increased from approximately two C. elegans and four Drosophila to 40 vertebrate proteins.
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Affiliation(s)
- Wei Sun Park
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
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27
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Cheung SMS, Kornelson JC, Al-Alwan M, Marshall AJ. Regulation of phosphoinositide 3-kinase signaling by oxidants: Hydrogen peroxide selectively enhances immunoreceptor-induced recruitment of phosphatidylinositol (3,4) bisphosphate-binding PH domain proteins. Cell Signal 2007; 19:902-12. [PMID: 17215104 DOI: 10.1016/j.cellsig.2006.10.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 10/26/2006] [Accepted: 10/27/2006] [Indexed: 12/29/2022]
Abstract
Phosphoinositide 3-kinases (PI3Ks) generate several distinct lipid second messengers including phosphatidylinositol (3,4,5) trisphosphate (PIP3) and phosphatidylinositol (3,4) bisphosphate PI(3,4)P2. PI(3,4)P2 is produced with distinct kinetics and binds to distinct PH domain effector proteins; however, the regulation of this signaling pathway is poorly understood. Superoxides such as hydrogen peroxide are transiently produced after activation through various cell surface receptors and play important roles in immune and inflammatory responses. Here we use quantitative microscopy to examine the effect of peroxide on PI(3,4)P2-mediated mobilization of signaling proteins in B lymphocytes. Peroxide was found to induce dose-dependant membrane recruitment of the PI(3,4)P2-binding PH domain proteins Bam32, TAPP2 and Akt/PKB but not the PIP3-binding PH domain of Btk. Peroxide-induced membrane recruitment was found to be dependant on PI3K activity, with the p110delta isoform contributing much of the activity in the BJAB human B lymphoma model. Strikingly, peroxide co-stimulation enhanced antigen receptor-induced membrane recruitment of Bam32 and TAPP2, with combined stimulation exceeding the maximum achievable with either stimulus alone. Expression of the lipid phosphatase PTEN led to reduction of antigen receptor-induced membrane recruitment of TAPP2; however, peroxide costimulation could overcome the inhibitory effect of PTEN. Inhibition of the NADPH oxidase led to reduction of antigen receptor-induced membrane recruitment of TAPP2. Our results indicate that exogenous and endogenous superoxides can modulate the quality of the PI3K signal in lymphocytes by selectively increasing PI(3,4)P2-dependant signaling.
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Affiliation(s)
- Samuel M S Cheung
- Department of Immunology, University of Manitoba, 730 William Avenue, Winnipeg, MB Canada R3E 0W3
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Lemmon MA. Pleckstrin homology (PH) domains and phosphoinositides. BIOCHEMICAL SOCIETY SYMPOSIUM 2007; 74:81-93. [PMID: 17233582 PMCID: PMC3777418 DOI: 10.1042/bss0740081] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PH (pleckstrin homology) domains represent the 11th most common domain in the human proteome. They are best known for their ability to bind phosphoinositides with high affinity and specificity, although it is now clear that less than 10% of all PH domains share this property. Cases in which PH domains bind specific phosphoinositides with high affinity are restricted to those phosphoinositides that have a pair of adjacent phosphates in their inositol headgroup. Those that do not [PtdIns3P, PtdIns5P and PtdIns(3,5)P2] are instead recognized by distinct classes of domains including FYVE domains, PX (phox homology) domains, PHD (plant homeodomain) fingers and the recently identified PROPPINs (b-propellers that bind polyphosphoinositides). Of the 90% of PH domains that do not bind strongly and specifically to phosphoinositides, few are well understood. One group of PH domains appears to bind both phosphoinositides (with little specificity) and Arf (ADP-ribosylation factor) family small G-proteins, and are targeted to the Golgi apparatus where both phosphoinositides and the relevant Arfs are both present. Here, the PH domains may function as coincidence detectors. A central challenge in understanding the majority of PH domains is to establish whether the very low affinity phosphoinositide binding reported in many cases has any functional relevance. For PH domains from dynamin and from Dbl family proteins, this weak binding does appear to be functionally important, although its precise mechanistic role is unclear. In many other cases, it is quite likely that alternative binding partners are more relevant, and that the observed PH domain homology represents conservation of structural fold rather than function.
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Affiliation(s)
- Mark A Lemmon
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, 809C Stellar-Chance Laboratories, 422 Curie Boulevard, Philadelphia, PA 19104-6059, USA.
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Delacour D, Gouyer V, Zanetta JP, Drobecq H, Leteurtre E, Grard G, Moreau-Hannedouche O, Maes E, Pons A, André S, Le Bivic A, Gabius HJ, Manninen A, Simons K, Huet G. Galectin-4 and sulfatides in apical membrane trafficking in enterocyte-like cells. ACTA ACUST UNITED AC 2005; 169:491-501. [PMID: 15883199 PMCID: PMC2171948 DOI: 10.1083/jcb.200407073] [Citation(s) in RCA: 208] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have previously reported that 1-benzyl-2-acetamido-2-deoxy-alpha-D-galactopyranoside (GalNAc alpha-O-bn), an inhibitor of glycosylation, perturbed apical biosynthetic trafficking in polarized HT-29 cells suggesting an involvement of a lectin-based mechanism. Here, we have identified galectin-4 as one of the major components of detergent-resistant membranes (DRMs) isolated from HT-29 5M12 cells. Galectin-4 was also found in post-Golgi carrier vesicles. The functional role of galectin-4 in polarized trafficking in HT-29 5M12 cells was studied by using a retrovirus-mediated RNA interference. In galectin-4-depleted HT-29 5M12 cells apical membrane markers accumulated intracellularly. In contrast, basolateral membrane markers were not affected. Moreover, galectin-4 depletion altered the DRM association characteristics of apical proteins. Sulfatides with long chain-hydroxylated fatty acids, which were also enriched in DRMs, were identified as high-affinity ligands for galectin-4. Together, our data propose that interaction between galectin-4 and sulfatides plays a functional role in the clustering of lipid rafts for apical delivery.
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Edlich C, Stier G, Simon B, Sattler M, Muhle-Goll C. Structure and phosphatidylinositol-(3,4)-bisphosphate binding of the C-terminal PH domain of human pleckstrin. Structure 2005; 13:277-86. [PMID: 15698571 DOI: 10.1016/j.str.2004.11.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2004] [Revised: 11/03/2004] [Accepted: 11/28/2004] [Indexed: 11/20/2022]
Abstract
Pleckstrin is the major target of protein kinase C (PKC) in blood platelets. Its phosphorylation triggers responses that ultimately lead to platelet activation and blood clot formation. Pleckstrin consists of three domains: a pleckstrin homology (PH) domain at both termini and a central DEP (Dishevelled, Egl-1, Pleckstrin) domain. Here, we report the solution nuclear magnetic resonance (NMR) structure of the C-terminal PH domain (C-PH) of human pleckstrin-1. We show that this PH domain binds phosphatidylinositol-3,4-bisphosphate (PtdIns(3,4)P2) with high specificity in protein lipid overlay assays. Using NMR titration experiments and mutational analysis, residues involved in binding to PtdIns(3,4)P2 are identified. The binding site is formed by a patch of basic residues from the beta1 and beta2 strands and the beta1-beta2 loop. Since PtdIns(3,4)P2 is an important signaling molecule in platelets, our data suggest a C-PH dependent regulation of pleckstrin function in response to PtdIns(3,4)P2.
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Allam A, Marshall AJ. Role of the adaptor proteins Bam32, TAPP1 and TAPP2 in lymphocyte activation. Immunol Lett 2005; 97:7-17. [PMID: 15626471 DOI: 10.1016/j.imlet.2004.09.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2004] [Revised: 09/28/2004] [Accepted: 09/29/2004] [Indexed: 01/13/2023]
Abstract
Adaptor proteins play critical roles in lymphocyte activation by mediating intermolecular interactions and assembling signaling complexes at the activated plasma membrane. Bam32/DAPP1 and the related adaptor proteins TAPP1 and TAPP2 were identified by multiple groups about 5 years ago and considerable progress has been made in elucidating the structure, interaction partners and function of these molecules. These cytoplasmic adaptor proteins are recruited to the plasma membrane through interaction of their PH domains with the lipid products of phosphatidylinositol 3-kinases. They share a unique mode of regulation in that they bind with high affinity to phosphatidylinositol-3,4-bisphosphate and their recruitment is enhanced rather than inhibited by the lipid phosphatase SHIP. Two knockout mouse studies and several gain-and-loss of function studies in cell lines have recently been published, demonstrating multiple functions of Bam32 in B cell activation. Bam32 is required for biological responses including B cell antigen receptor (BCR)-induced proliferation and antibody responses to type II T-independent antigens. Bam32 regulates multiple BCR signaling events including activation of the mitogen activated protein kinases ERK and JNK, remodeling of the actin cytoskeleton through the GTPase Rac1 and BCR internalization. Several studies have emerged suggesting that TAPP1 and TAPP2 may play roles in B and T cell activation; however, the biological functions regulated by these molecules remain to be defined. Here we will comprehensively review the available data on the structure and function of Bam32, TAPP1 and TAPP2 and present an integrated working model for Bam32 function in B cell activation and a general model for distinct effector pathways of PI 3-kinases.
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Affiliation(s)
- Atef Allam
- Department of Immunology, University of Manitoba, 611 Basic Medical Sciences Building, 730 William Avenue, Winnipeg, Man., R3E-0W3, Canada
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Downes CP, Gray A, Lucocq JM. Probing phosphoinositide functions in signaling and membrane trafficking. Trends Cell Biol 2005; 15:259-68. [PMID: 15866030 DOI: 10.1016/j.tcb.2005.03.008] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The inositol phospholipids (PIs) comprise a family of eight species with different combinations of phosphate groups arranged around the inositol ring. PIs are among the most versatile signaling molecules known, with key roles in receptor-mediated signal transduction, actin remodeling and membrane trafficking. Recent studies have identified effector proteins and specific lipid-binding domains through which PIs signal. These lipid-binding domains can be used as probes to further our understanding of the spatial and temporal control of individual PI species. New layers of complexity revealed by the use of such probes include the occurrence of PIs at intracellular locations, the identification of phosphatidylinositol signaling hotspots and the presence of non-membrane pools of PIs in cell nuclei.
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Affiliation(s)
- C Peter Downes
- Division of Cell Signalling, School of Life Sciences, MSI/WTB Complex, University of Dundee, Dundee DD1 5EH, Scotland, UK.
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Komander D, Fairservice A, Deak M, Kular GS, Prescott AR, Peter Downes C, Safrany ST, Alessi DR, van Aalten DMF. Structural insights into the regulation of PDK1 by phosphoinositides and inositol phosphates. EMBO J 2004; 23:3918-28. [PMID: 15457207 PMCID: PMC524332 DOI: 10.1038/sj.emboj.7600379] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 07/29/2004] [Indexed: 11/08/2022] Open
Abstract
3-phosphoinositide-dependent protein kinase-1 (PDK1) phosphorylates and activates many kinases belonging to the AGC subfamily. PDK1 possesses a C-terminal pleckstrin homology (PH) domain that interacts with PtdIns(3,4,5)P3/PtdIns(3,4)P2 and with lower affinity to PtdIns(4,5)P2. We describe the crystal structure of the PDK1 PH domain, in the absence and presence of PtdIns(3,4,5)P3 and Ins(1,3,4,5)P4. The structures reveal a 'budded' PH domain fold, possessing an N-terminal extension forming an integral part of the overall fold, and display an unusually spacious ligand-binding site. Mutagenesis and lipid-binding studies were used to define the contribution of residues involved in phosphoinositide binding. Using a novel quantitative binding assay, we found that Ins(1,3,4,5,6)P5 and InsP6, which are present at micromolar levels in the cytosol, interact with full-length PDK1 with nanomolar affinities. Utilising the isolated PDK1 PH domain, which has reduced affinity for Ins(1,3,4,5,6)P5/InsP6, we perform localisation studies that suggest that these inositol phosphates serve to anchor a portion of cellular PDK1 in the cytosol, where it could activate its substrates such as p70 S6-kinase and p90 ribosomal S6 kinase that do not interact with phosphoinositides.
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Affiliation(s)
- David Komander
- Division of Biological Chemistry & Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
- MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Alison Fairservice
- Division of Cell Signalling, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Maria Deak
- MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Gursant S Kular
- MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Alan R Prescott
- Division of Cell Biology and Immunology, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - C Peter Downes
- Division of Cell Signalling, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Stephen T Safrany
- Division of Cell Signalling, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Dario R Alessi
- MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Daan M F van Aalten
- Division of Biological Chemistry & Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
- Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, MSI/WTB Complex, Dundee DD1 5EH, UK. Tel.: +44 1382 344 979; Fax: +44 1382 345 764; E-mail:
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34
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Affiliation(s)
- Robin Irvine
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, UK
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35
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Favier AL, Burmeister WP, Chroboczek J. Unique physicochemical properties of human enteric Ad41 responsible for its survival and replication in the gastrointestinal tract. Virology 2004; 322:93-104. [PMID: 15063120 PMCID: PMC7172780 DOI: 10.1016/j.virol.2004.01.020] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2003] [Revised: 12/08/2003] [Accepted: 01/13/2004] [Indexed: 01/30/2023]
Abstract
Human enteric adenovirus Ad41 is associated with children gastroenteritis. To infect gastrointestinal cells, the invading virus must be acid-stable and resistant to inactivation by bile salts and proteases. In addition, it has to cross the mucus barrier before it infects mucosa cells. We show that Ad41 infectivity is not diminished by acid exposure, a condition limiting the infectivity of the respiratory Ad. This feature can be attributed to a large extent to the global basic charge of enteric Ad virions and to the stability of Ad41 fiber, a viral protein mediating virus attachment. Upon exposure to pH shock, the respiratory Ad2 loses its ability to interact with lipids while enteric Ad41 still binds to the major phospholipids of gastric and intestine mucus. In addition, contrary to respiratory Ad, enteric Ad41 interacts with several sphingolipid components of plasma membranes. These results show that the molecular bases of the Ad41 enteric tropism stem from its particular physicochemical properties.
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Affiliation(s)
| | - Wilhelm P Burmeister
- Virologie Moléculaire et Structurale, UFR de Pharmacie, Université Joseph Fourier, et EMBL, Grenoble, France
| | - Jadwiga Chroboczek
- Institut de Biologie Structurale, 38027 Grenoble Cedex 1, France
- Corresponding author. Institut de Biologie Structurale, 41, rue Jules Horowitz, 38027 Grenoble Cedex 1, France. Fax: +33-4-38-78-54-94.
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36
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Watt SA, Kimber WA, Fleming IN, Leslie NR, Downes CP, Lucocq JM. Detection of novel intracellular agonist responsive pools of phosphatidylinositol 3,4-bisphosphate using the TAPP1 pleckstrin homology domain in immunoelectron microscopy. Biochem J 2004; 377:653-63. [PMID: 14604433 PMCID: PMC1223916 DOI: 10.1042/bj20031397] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2003] [Revised: 10/31/2003] [Accepted: 11/03/2003] [Indexed: 11/17/2022]
Abstract
PtdIns(3,4) P (2), a breakdown product of the lipid second messenger PtdIns(3,4,5) P (3), is a key signalling molecule in pathways controlling various cellular events. Cellular levels of PtdIns(3,4) P (2) are elevated upon agonist stimulation, mediating downstream signalling pathways by recruiting proteins containing specialized lipid-binding modules, such as the pleckstrin homology (PH) domain. A recently identified protein, TAPP1 (tandem-PH-domain-containing protein 1), has been shown to interact in vitro with high affinity and specificity with PtdIns(3,4) P (2) through its C-terminal PH domain. In the present study, we have utilized this PH domain tagged with glutathione S-transferase (GST-TAPP1-PH) as a probe in an on-section immunoelectron microscopy labelling procedure, mapping the subcellular distribution of PtdIns(3,4) P (2). As expected, we found accumulation of PtdIns(3,4) P (2) at the plasma membrane in response to the agonists platelet-derived growth factor and hydrogen peroxide. Importantly, however, we also found agonist stimulated PtdIns(3,4) P (2) labelling of intracellular organelles, including the endoplasmic reticulum and multivesicular endosomes. Expression of the 3-phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10) in PTEN-null U87MG cells revealed differential sensitivity of these lipid pools to the enzyme. These data suggest a role for PtdIns(3,4) P (2) in endomembrane function.
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Affiliation(s)
- Stephen A Watt
- Division of Cell Biology and Immunology, School of Life Sciences, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
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37
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Hilpelä P, Vartiainen MK, Lappalainen P. Regulation of the Actin Cytoskeleton by PI(4,5)P2 and PI(3,4,5)P3. Curr Top Microbiol Immunol 2004; 282:117-63. [PMID: 14594216 DOI: 10.1007/978-3-642-18805-3_5] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The actin cytoskeleton is fundamental for various motile and morphogenetic processes in cells. The structure and dynamics of the actin cytoskeleton are regulated by a wide array of actin-binding proteins, whose activities are controlled by various signal transduction pathways. Recent studies have shown that certain membrane phospholipids, especially PI(4,5)P2 and PI(3,4,5)P3, regulate actin filament assembly in cells and in cell extracts. PI(4,5)P2 appears to be a general regulator of actin polymerization at the plasma membrane or at membrane microdomains, whereas PI(3,4,5)P3 promotes the assembly of specialized actin filament structures in response to some growth factors. Biochemical studies have demonstrated that the activities of many proteins promoting actin assembly are upregulated by PI(4,5)P2, whereas proteins that inhibit actin assembly or promote filament disassembly are down-regulated by PI(4,5)P2. PI(3,4,5)P3 promotes its effects on the actin cytoskeleton mainly through activation of the Rho family of small GTPases. In addition to their effects on actin dynamics, both PI(4,5)P2 and PI(3,4,5)P3 promote the formation of specific actin filament structures through activation/inactivation of actin filament cross-linking proteins and proteins that mediate cytoskeleton-plasma membrane interactions.
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Affiliation(s)
- P Hilpelä
- Program in Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
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38
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Abstract
Modular domains that recognize and target intracellular membranes play a critical role in the assembly, localization, and function of signaling and trafficking complexes in eukaryotic cells. Large domain families, including PH, FYVE, PX, PHD, and C2 domains, combine specific, nonspecific, and multivalent interactions to achieve selective membrane targeting. Despite structural and functional diversity, general features of lipid recognition are evident in the various membrane-targeting mechanisms.
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Affiliation(s)
- Jonathan P DiNitto
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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39
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Kimber WA, Deak M, Prescott AR, Alessi DR. Interaction of the protein tyrosine phosphatase PTPL1 with the PtdIns(3,4)P2-binding adaptor protein TAPP1. Biochem J 2003; 376:525-35. [PMID: 14516276 PMCID: PMC1223793 DOI: 10.1042/bj20031154] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2003] [Revised: 09/19/2003] [Accepted: 09/29/2003] [Indexed: 12/22/2022]
Abstract
It has been postulated that PtdIns(3,4) P (2), one of the immediate breakdown products of PtdIns(3,4,5) P (3), functions as a signalling molecule in insulin- and growth-factor-stimulated pathways. To date, the t andem- P H-domain-containing p rotein- 1 (TAPP1) and related TAPP2 are still the only known PH-domain-containing proteins that interact strongly and specifically with PtdIns(3,4) P (2). In this study we demonstrate that endogenously expressed TAPP1, is constitutively associated with the protein-tyrosine-phosphatase-like protein-1 (PTPL1 also known as FAP-1). We show that PTPL1 binds to TAPP1 and TAPP2, principally though its first PDZ domain [where PDZ is postsynaptic density protein ( P SD-95)/ Drosophila disc large tumour suppressor ( d lg)/tight junction protein ( Z O1)] and show that this renders PTPL1 capable of associating with PtdIns(3,4) P (2) in vitro. Our data suggest that the binding of TAPP1 to PTPL1 does not influence PTPL1 phosphatase activity, but instead functions to maintain PTPL1 in the cytoplasm. Following stimulation of cells with hydrogen peroxide to induce PtdIns(3,4) P (2) production, PTPL1, complexed to TAPP1, translocates to the plasma membrane. This study provides the first evidence that TAPP1 and PtdIns(3,4) P (2) could function to regulate the membrane localization of PTPL1. We speculate that if PTPL1 was recruited to the plasma membrane by increasing levels of PtdIns(3,4) P (2), it could trigger a negative feedback loop in which phosphoinositide-3-kinase-dependent or other signalling pathways could be switched off by the phosphatase-catalysed dephosphorylation of receptor tyrosine kinases or tyrosine phosphorylated adaptor proteins such as IRS1 or IRS2. Consistent with this notion we observed RNA-interference-mediated knock-down of TAPP1 in HEK-293 cells, enhanced activation and phosphorylation of PKB following IGF1 stimulation.
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Affiliation(s)
- Wendy A Kimber
- MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK.
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40
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Singh SM, Murray D. Molecular modeling of the membrane targeting of phospholipase C pleckstrin homology domains. Protein Sci 2003; 12:1934-53. [PMID: 12930993 PMCID: PMC2323991 DOI: 10.1110/ps.0358803] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Phospholipases C (PLCs) reversibly associate with membranes to hydrolyze phosphatidylinositol-4, 5-bisphosphate (PI[4,5]P(2)) and comprise four main classes: beta, gamma, delta, and epsilon. Most eukaryotic PLCs contain a single, N-terminal pleckstrin homology (PH) domain, which is thought to play an important role in membrane targeting. The structure of a single PLC PH domain, that from PLCdelta1, has been determined; this PH domain binds PI(4,5)P(2) with high affinity and stereospecificity and has served as a paradigm for PH domain functionality. However, experimental studies demonstrate that PH domains from different PLC classes exhibit diverse modes of membrane interaction, reflecting the dissimilarity in their amino acid sequences. To elucidate the structural basis for their differential membrane-binding specificities, we modeled the three-dimensional structures of all mammalian PLC PH domains by using bioinformatic tools and calculated their biophysical properties by using continuum electrostatic approaches. Our computational analysis accounts for a large body of experimental data, provides predictions for those PH domains with unknown functions, and indicates functional roles for regions other than the canonical lipid-binding site identified in the PLCdelta1-PH structure. In particular, our calculations predict that (1). members from each of the four PLC classes exhibit strikingly different electrostatic profiles than those ordinarily observed for PH domains in general, (2). nonspecific electrostatic interactions contribute to the membrane localization of PLCdelta-, PLCgamma-, and PLCbeta-PH domains, and (3). phosphorylation regulates the interaction of PLCbeta-PH with its effectors through electrostatic repulsion. Our molecular models for PH domains from all of the PLC classes clearly demonstrate how a common structural fold can serve as a scaffold for a wide range of surface features and biophysical properties that support distinctive functional roles.
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Affiliation(s)
- Shaneen M Singh
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021, USA
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41
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Hilpelä P, Oberbanscheidt P, Hahne P, Hund M, Kalhammer G, Small JV, Bähler M. SWAP-70 identifies a transitional subset of actin filaments in motile cells. Mol Biol Cell 2003; 14:3242-53. [PMID: 12925760 PMCID: PMC181564 DOI: 10.1091/mbc.e03-01-0043] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Functionally different subsets of actin filament arrays contribute to cellular organization and motility. We report the identification of a novel subset of loose actin filament arrays through regulated association with the widely expressed protein SWAP-70. These loose actin filament arrays were commonly located behind protruding lamellipodia and membrane ruffles. Visualization of these loose actin filament arrays was dependent on lamellipodial protrusion and the binding of the SWAP-70 PH-domain to a 3'-phosphoinositide. SWAP-70 with a functional pleckstrin homology-domain lacking the C-terminal 60 residues was targeted to the area of the loose actin filament arrays, but it did not associate with actin filaments. The C-terminal 60 residues were sufficient for actin filament association, but they provided no specificity for the subset of loose actin filament arrays. These results identify SWAP-70 as a phosphoinositide 3-kinase signaling-dependent marker for a distinct, hitherto unrecognized, array of actin filaments. Overexpression of SWAP-70 altered the actin organization and lamellipodial morphology. These alterations were dependent on a proper subcellular targeting of SWAP-70. We propose that SWAP-70 regulates the actin cytoskeleton as an effector or adaptor protein in response to agonist stimulated phosphatidylinositol (3,4)-bisphosphate production and cell protrusion.
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Affiliation(s)
- Pirta Hilpelä
- Institut für Allgemeine Zoologie und Genetik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany
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Karathanassis D, Stahelin RV, Bravo J, Perisic O, Pacold CM, Cho W, Williams RL. Binding of the PX domain of p47(phox) to phosphatidylinositol 3,4-bisphosphate and phosphatidic acid is masked by an intramolecular interaction. EMBO J 2002; 21:5057-68. [PMID: 12356722 PMCID: PMC129041 DOI: 10.1093/emboj/cdf519] [Citation(s) in RCA: 258] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
p47(phox) is a key cytosolic subunit required for activation of phagocyte NADPH oxidase. The X-ray structure of the p47(phox) PX domain revealed two distinct basic pockets on the membrane-binding surface, each occupied by a sulfate. These two pockets have different specificities: one preferentially binds phosphatidylinositol 3,4-bisphosphate [PtdIns(3,4)P(2)] and is analogous to the phophatidylinositol 3-phosphate (PtdIns3P)-binding pocket of p40(phox), while the other binds anionic phospholipids such as phosphatidic acid (PtdOH) or phosphatidylserine. The preference of this second site for PtdOH may be related to previously observed activation of NADPH oxidase by PtdOH. Simultaneous occupancy of the two phospholipid-binding pockets radically increases membrane affinity. Strikingly, measurements for full-length p47(phox) show that membrane interaction by the PX domain is masked by an intramolecular association with the C-terminal SH3 domain (C-SH3). Either a site-specific mutation in C-SH3 (W263R) or a mimic of the phosphorylated form of p47(phox) [Ser(303, 304, 328, 359, 370)Glu] cause a transition from a closed to an open conformation that binds membranes with a greater affinity than the isolated PX domain.
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Affiliation(s)
- Dimitrios Karathanassis
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
| | - Robert V. Stahelin
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
| | - Jerónimo Bravo
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
| | - Olga Perisic
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
| | - Christine M. Pacold
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
| | - Wonhwa Cho
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
| | - Roger L. Williams
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA Present address: Structural Biology Program, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, E-28029 Madrid, Spain Corresponding author e-mail:
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Thomas CC, Deak M, Alessi DR, van Aalten DMF. High-resolution structure of the pleckstrin homology domain of protein kinase b/akt bound to phosphatidylinositol (3,4,5)-trisphosphate. Curr Biol 2002; 12:1256-62. [PMID: 12176338 DOI: 10.1016/s0960-9822(02)00972-7] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The products of PI 3-kinase activation, PtdIns(3,4,5)P3 and its immediate breakdown product PtdIns(3,4)P2, trigger physiological processes, by interacting with proteins possessing pleckstrin homology (PH) domains. One of the best characterized PtdIns(3,4,5)P3/PtdIns(3,4)P2 effector proteins is protein kinase B (PKB), also known as Akt. PKB possesses a PH domain located at its N terminus, and this domain binds specifically to PtdIns(3,4,5)P3 and PtdIns(3,4)P2 with similar affinity. Following activation of PI 3-kinase, PKB is recruited to the plasma membrane by virtue of its interaction with PtdIns(3,4,5)P3/PtdIns(3,4)P2. PKB is then activated by the 3-phosphoinositide-dependent pro-tein kinase-1 (PDK1), which like PKB, possesses a PtdIns(3,4,5)P3/PtdIns(3,4)P2 binding PH domain. Here, we describe the high-resolution crystal structure of the isolated PH domain of PKB(alpha) in complex with the head group of PtdIns(3,4,5)P3. The head group has a significantly different orientation and location compared to other Ins(1,3,4,5)P4 binding PH domains. Mutagenesis of the basic residues that form ionic interactions with the D3 and D4 phosphate groups reduces or abolishes the ability of PKB to interact with PtdIns(3,4,5)P3 and PtdIns(3,4)P2. The D5 phosphate faces the solvent and forms no significant interactions with any residue on the PH domain, and this explains why PKB interacts with similar affinity with both PtdIns(3,4,5)P3 and PtdIns(3,4)P2.
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Affiliation(s)
- Christine C Thomas
- Division of Biological Chemistry and Molecular Microbiology, Scotland, United Kingdom
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Dowler S, Kular G, Alessi DR. Protein lipid overlay assay. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2002; 2002:pl6. [PMID: 11972359 DOI: 10.1126/stke.2002.129.pl6] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Protein Lipid Overlay (PLO) assay enables the identification of the lipid ligands with which lipid binding proteins interact. This assay also provides qualitative information on the relative affinity with which a protein binds to a lipid. In the PLO assay, serial dilutions of different lipids are spotted onto a nitrocellulose membrane to which they attach. These membranes are then incubated with a lipid binding protein possessing an epitope tag. The membranes are washed and the protein, still bound to the membrane by virtue of its interaction with lipid(s), is detected by immunoblotting with an antibody recognizing the epitope tag. This procedure requires only a few micrograms of protein and is quicker and cheaper to perform than other methods that have been developed to assess protein-lipid interactions. The reagents required for the PLO assay are readily available from commercial sources and the assay can be performed in any laboratory, even by those with no prior expertise in this area.
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Affiliation(s)
- Simon Dowler
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB Complex University of Dundee, Dow Street, Dundee DD1 5EH, Scotland
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Kimber WA, Trinkle-Mulcahy L, Cheung PCF, Deak M, Marsden LJ, Kieloch A, Watt S, Javier RT, Gray A, Downes CP, Lucocq JM, Alessi DR. Evidence that the tandem-pleckstrin-homology-domain-containing protein TAPP1 interacts with Ptd(3,4)P2 and the multi-PDZ-domain-containing protein MUPP1 in vivo. Biochem J 2002; 361:525-36. [PMID: 11802782 PMCID: PMC1222335 DOI: 10.1042/0264-6021:3610525] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
PtdIns(3,4,5)P3 is an established second messenger of growth-factor and insulin-induced signalling pathways. There is increasing evidence that one of the immediate breakdown products of PtdIns(3,4,5)P3, namely PtdIns(3,4)P2, whose levels are elevated by numerous extracellular agonists, might also function as a signalling molecule. Recently, we identified two related pleckstrin-homology (PH)-domain-containing proteins, termed 'tandem-PH-domain-containing protein-1' (TAPP1) and TAPP2, which interacted in vitro with high affinity with PtdIns(3,4)P2, but did not bind PtdIns(3,4,5)P3 or other phosphoinositides. In the present study we demonstrate that stimulation of Swiss 3T3 or 293 cells with agonists that stimulate PtdIns(3,4)P2 production results in the marked translocation of TAPP1 to the plasma membrane. This recruitment is dependent on a functional PtdIns(3,4)P2-binding PH domain and is inhibited by wortmannin, a phosphoinositide 3-kinase inhibitor that prevents PtdIns(3,4)P2 generation. A search for proteins that interact with TAPP1 identified the multi-PDZ-containing protein termed 'MUPP1', a protein possessing 13 PDZ domains and no other known modular or catalytic domains [PDZ is postsynaptic density protein (PSD-95)/Drosophila disc large tumour suppressor (dlg)/tight junction protein (ZO1)]. We demonstrate that immunoprecipitation of endogenously expressed TAPP1 from 293-cell lysates results in the co-immunoprecipitation of endogenous MUPP1, indicating that these proteins are likely to interact with each other physiologically. We show that TAPP1 and TAPP2 interact with the 10th and 13th PDZ domain of MUPP1 through their C-terminal amino acids. The results of the present study suggest that TAPP1 and TAPP2 could function in cells as adapter proteins to recruit MUPP1, or other proteins that they may interact with, to the plasma membrane in response to signals that elevate PtdIns(3,4)P2.
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Affiliation(s)
- Wendy A Kimber
- MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK.
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