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Lu KY, Pasaje CFA, Srivastava T, Loiselle DR, Niles JC, Derbyshire E. Phosphatidylinositol 3-phosphate and Hsp70 protect Plasmodium falciparum from heat-induced cell death. eLife 2020; 9:e56773. [PMID: 32975513 PMCID: PMC7518890 DOI: 10.7554/elife.56773] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 09/14/2020] [Indexed: 12/12/2022] Open
Abstract
Phosphatidylinositol 3-phosphate (PI(3)P) levels in Plasmodium falciparum correlate with tolerance to cellular stresses caused by artemisinin and environmental factors. However, PI(3)P function during the Plasmodium stress response was unknown. Here, we used PI3K inhibitors and antimalarial agents to examine the importance of PI(3)P under thermal conditions recapitulating malarial fever. Live cell microscopy using chemical and genetic reporters revealed that PI(3)P stabilizes the digestive vacuole (DV) under heat stress. We demonstrate that heat-induced DV destabilization in PI(3)P-deficient P. falciparum precedes cell death and is reversible after withdrawal of the stress condition and the PI3K inhibitor. A chemoproteomic approach identified PfHsp70-1 as a PI(3)P-binding protein. An Hsp70 inhibitor and knockdown of PfHsp70-1 phenocopy PI(3)P-deficient parasites under heat shock. Furthermore, PfHsp70-1 downregulation hypersensitizes parasites to heat shock and PI3K inhibitors. Our findings underscore a mechanistic link between PI(3)P and PfHsp70-1 and present a novel PI(3)P function in DV stabilization during heat stress.
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Affiliation(s)
- Kuan-Yi Lu
- Department of Molecular Genetics and Microbiology, School of Medicine, Duke UniversityDurhamUnited States
- Department of Chemistry, Duke UniversityDurhamUnited States
| | | | | | - David R Loiselle
- Department of Pharmacology and Cancer Biology, School of Medicine, Duke UniversityDurhamUnited States
| | - Jacquin C Niles
- Department of Biological Engineering, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Emily Derbyshire
- Department of Molecular Genetics and Microbiology, School of Medicine, Duke UniversityDurhamUnited States
- Department of Chemistry, Duke UniversityDurhamUnited States
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2
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Pike CM, Boyer-Andersen R, Kinch LN, Caplan JL, Neunuebel MR. The Legionella effector RavD binds phosphatidylinositol-3-phosphate and helps suppress endolysosomal maturation of the Legionella-containing vacuole. J Biol Chem 2019; 294:6405-6415. [PMID: 30733336 PMCID: PMC6484141 DOI: 10.1074/jbc.ra118.007086] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 01/17/2019] [Indexed: 12/25/2022] Open
Abstract
Upon phagocytosis into macrophages, the intracellular bacterial pathogen Legionella pneumophila secretes effector proteins that manipulate host cell components, enabling it to evade lysosomal degradation. However, the bacterial proteins involved in this evasion are incompletely characterized. Here we show that the L. pneumophila effector protein RavD targets host membrane compartments and contributes to the molecular mechanism the pathogen uses to prevent encounters with lysosomes. Protein-lipid binding assays revealed that RavD selectively binds phosphatidylinositol-3-phosphate (PI(3)P) in vitro We further determined that a C-terminal RavD region mediates the interaction with PI(3)P and that this interaction requires Arg-292. In transiently transfected mammalian cells, mCherry-RavD colocalized with the early endosome marker EGFP-Rab5 as well as the PI(3)P biosensor EGFP-2×FYVE. However, treatment with the phosphoinositide 3-kinase inhibitor wortmannin did not disrupt localization of mCherry-RavD to endosomal compartments, suggesting that RavD's interaction with PI(3)P is not necessary to anchor RavD to endosomal membranes. Using superresolution and immunogold transmission EM, we observed that, upon translocation into macrophages, RavD was retained onto the Legionella-containing vacuole and was also present on small vesicles adjacent to the vacuole. We also report that despite no detectable effects on intracellular growth of L. pneumophila within macrophages or amebae, the lack of RavD significantly increased the number of vacuoles that accumulate the late endosome/lysosome marker LAMP-1 during macrophage infection. Together, our findings suggest that, although not required for intracellular replication of L. pneumophila, RavD is a part of the molecular mechanism that steers the Legionella-containing vacuole away from endolysosomal maturation pathways.
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Affiliation(s)
| | | | - Lisa N Kinch
- the Howard Hughes Medical Institute, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Jeffrey L Caplan
- From the Delaware Biotechnology Institute and
- Departments of Biological Sciences and
- Plant and Soil Sciences, University of Delaware, Newark, Delaware 19716 and
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3
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Hirano T, Munnik T, Sato MH. Inhibition of phosphatidylinositol 3,5-bisphosphate production has pleiotropic effects on various membrane trafficking routes in Arabidopsis. Plant Cell Physiol 2017; 58:120-129. [PMID: 27803131 DOI: 10.1093/pcp/pcw164] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 09/15/2016] [Indexed: 06/06/2023]
Abstract
Phosphoinositides play an important role in various membrane trafficking events in eukaryotes. One of them, however, phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2], has not been studied widely in plants. Using a combination of fluorescent reporter proteins and the PI(3,5)P2-specific inhibitor YM202636, here we demonstrated that in Arabidopsis thaliana, PI(3,5)P2 affects various membrane trafficking events, mostly in the post-Golgi routes. We found that YM201636 treatment effectively reduced PI(3,5)P2 concentration not only in the wild type but also in FAB1A-overexpressing Arabidopsis plants. In particular, reduced PI(3,5)P2 levels caused abnormal membrane dynamics of plasma membrane proteins, AUX1 and BOR1, with different trafficking patterns. Secretion and morphological characteristics of late endosomes and vacuoles were also affected by the decreased PI(3,5)P2 production. These pleiotropic defects in the post-Golgi trafficking events were caused by the inhibition of PI(3,5)P2 production. This effect is probably mediated by the inhibition of maturation of FAB1-positive late endosomes, thereby impairing late endosome function. In conclusion, our results imply that in Arabidopsis, late endosomes are involved in multiple post-Golgi membrane trafficking routes including not only vacuolar trafficking and endocytosis but also secretion.
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Affiliation(s)
- Tomoko Hirano
- Laboratory of Cellular Dynamics, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Teun Munnik
- Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Masa H Sato
- Laboratory of Cellular Dynamics, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
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4
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Fernandes F, Chen K, Ehrlich LS, Jin J, Chen MH, Medina GN, Symons M, Montelaro R, Donaldson J, Tjandra N, Carter CA. Phosphoinositides direct equine infectious anemia virus gag trafficking and release. Traffic 2011; 12:438-51. [PMID: 21176037 PMCID: PMC3064743 DOI: 10.1111/j.1600-0854.2010.01153.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphatidylinositol 4,5-biphosphate [PI(4,5)P(2) ], the predominant phosphoinositide (PI) on the plasma membrane, binds the matrix (MA) protein of human immunodeficiency virus type 1 (HIV-1) and equine infectious anemia virus (EIAV) with similar affinities in vitro. Interaction with PI(4,5)P(2) is critical for HIV-1 assembly on the plasma membrane. EIAV has been shown to localize in internal compartments; hence, the significance of its interaction with PI(4,5)P(2) is unclear. We therefore investigated the binding in vitro of other PIs to EIAV MA and whether intracellular association with compartments bearing these PIs was important for assembly and release of virus-like particles (VLPs) formed by Gag. In vitro, EIAV MA bound phosphatidylinositol 3-phosphate [PI(3)P] with higher affinity than PI(4,5)P(2) as revealed by nuclear magnetic resonance (NMR) spectra upon lipid titration. Gag was detected on the plasma membrane and in compartments enriched in phosphatidylinositol 3,5-biphosphate [PI(3,5)P(2) ]. Treatment of cells with YM201636, a kinase inhibitor that blocks production of PI(3,5)P(2) from PI(3)P, caused Gag to colocalize with aberrant compartments and inhibited VLP release. In contrast to HIV-1, release of EIAV VLPs was not significantly diminished by coexpression with 5-phosphatase IV, an enzyme that specifically depletes PI(4,5)P(2) from the plasma membrane. However, coexpression with synaptojanin 2, a phosphatase with broader specificity, diminished VLP production. PI-binding pocket mutations caused striking budding defects, as revealed by electron microscopy. One of the mutations also modified Gag-Gag interaction, as suggested by altered bimolecular fluorescence complementation. We conclude that PI-mediated targeting to peripheral and internal membranes is a critical factor in EIAV assembly and release.
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Affiliation(s)
- Fiona Fernandes
- Dept. of Molecular Genetics & Microbiology, S.U.N.Y, Stony Brook, NY 11727, USA
| | - Kang Chen
- Laboratory of Molecular Biophysics, NHLBI-NIH, Bethesda, MD 20892, USA
| | - Lorna S. Ehrlich
- Dept. of Molecular Genetics & Microbiology, S.U.N.Y, Stony Brook, NY 11727, USA
| | - Jing Jin
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Min H. Chen
- Dept. of Molecular Genetics & Microbiology, S.U.N.Y, Stony Brook, NY 11727, USA
| | - Gisselle N. Medina
- Dept. of Molecular Genetics & Microbiology, S.U.N.Y, Stony Brook, NY 11727, USA
| | - Marc Symons
- Feinstein Institute, Manhasset, NY 11030, USA
| | - Ronald Montelaro
- Dept. of Microbiology and Molecular Genetics, Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA 15261
| | - Julie Donaldson
- Laboratory of Cell Biology, NHLBI-NIH, Bethesda, MD 20892, USA
| | - Nico Tjandra
- Laboratory of Molecular Biophysics, NHLBI-NIH, Bethesda, MD 20892, USA
| | - Carol A. Carter
- Dept. of Molecular Genetics & Microbiology, S.U.N.Y, Stony Brook, NY 11727, USA
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Keizer-Gunnink I, Kortholt A, Van Haastert PJM. Chemoattractants and chemorepellents act by inducing opposite polarity in phospholipase C and PI3-kinase signaling. ACTA ACUST UNITED AC 2007; 177:579-85. [PMID: 17517960 PMCID: PMC2064204 DOI: 10.1083/jcb.200611046] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
During embryonic development, cell movement is orchestrated by a multitude of attractants and repellents. Chemoattractants applied as a gradient, such as cAMP with Dictyostelium discoideum or fMLP with neutrophils, induce the activation of phospholipase C (PLC) and phosphoinositide 3 (PI3)-kinase at the front of the cell, leading to the localized depletion of phosphatidylinositol 4,5-bisphosphate (PI[4,5]P2) and the accumulation of phosphatidylinositol-3,4,5-trisphosphate (PI[3,4,5]P3). Using D. discoideum, we show that chemorepellent cAMP analogues induce localized inhibition of PLC, thereby reversing the polarity of PI(4,5)P2. This leads to the accumulation of PI(3,4,5)P3 at the rear of the cell, and chemotaxis occurs away from the source. We conclude that a PLC polarity switch controls the response to attractants and repellents.
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Affiliation(s)
- Ineke Keizer-Gunnink
- Department of Molecular Cell Biology, University of Groningen, Haren, Netherlands
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6
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DeKroon R, Robinette JB, Hjelmeland AB, Wiggins E, Blackwell M, Mihovilovic M, Fujii M, York J, Hart J, Kontos C, Rich J, Strittmatter WJ. APOE4-VLDL inhibits the HDL-activated phosphatidylinositol 3-kinase/Akt Pathway via the phosphoinositol phosphatase SHIP2. Circ Res 2006; 99:829-36. [PMID: 16973905 DOI: 10.1161/01.res.0000245479.03190.9f] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Endothelial cell dysfunction and apoptosis are critical in the pathogenesis of atherosclerotic cardiovascular disease (CVD). Both endothelial cell apoptosis and atherosclerosis are reduced by high-density lipoprotein (HDL). Low HDL levels increase the risk of CVD and are also a key characteristic of the metabolic syndrome. The apolipoprotein E4 (APOE4) allele also increases the risk of atherosclerosis and CVD. We previously demonstrated that the antiapoptotic activity of HDL is inhibited by APOE4 very-low-density lipoprotein (APOE4-VLDL) in endothelial cells, an effect similar to reducing the levels of HDL. Here we establish the intracellular mechanism by which APOE4-VLDL inhibits the antiapoptotic pathway activated by HDL. We show that APOE4-VLDL diminishes the phosphorylation of Akt by HDL but does not alter phosphorylation of c-Jun N-terminal kinase, p38, or Src family kinases by HDL. Furthermore APOE4-VLDL inhibits Akt phosphorylation by reducing the phosphatidylinositol 3-kinase product phosphatidylinositol-(3,4,5)-triphosphate (PI[3,4,5]P3). We further demonstrate that APOE4-VLDL reduces PI(3,4,5)P3, through the phosphoinositol phosphatase SHIP2, and not through PTEN. SHIP2 is already implicated as an independent risk factor for type II diabetes, hypertension and obesity, which are also all components of the metabolic syndrome and independent risk factors for CVD. Significantly, the association between CVD and type 2 diabetes or hypertension is further increased by the APOE4 allele. Therefore the activation of SHIP2 by APOE4-VLDL, with the subsequent inhibition of the HDL/Akt pathway, is a novel and significant biological mechanism and may be a critical intermediate by which APOE4 increases the risk of atherosclerotic CVD.
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Affiliation(s)
- Robert DeKroon
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
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7
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Abstract
Modulation of voltage-gated L-type Ca2+ channels by phosphoinositide 3-kinase (PI3K) regulates Ca2+ entry and plays a crucial role in vascular excitation-contraction coupling. Angiotensin II (Ang II) activates Ca2+ entry by stimulating L-type Ca2+ channels through Gbeta-sensitive PI3K in portal vein myocytes. Moreover, PI3K and Ca2+ entry activation have been reported to be necessary for receptor tyrosine kinase-coupled and G protein-coupled receptor-induced DNA synthesis in vascular cells. We have previously shown that tyrosine kinase-regulated class Ia and G protein-regulated class Ib PI3Ks are able to modulate vascular L-type Ca2+ channels. PI3Ks display 2 enzymatic activities: a lipid-kinase activity leading to the formation of phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3 or PIP3] and a serine-kinase activity. Here we show that exogenous PIP3 applied into the cell through the patch pipette is able to reproduce the Ca2+ channel-stimulating effect of Ang II and PI3Ks. Moreover, the Ang II-induced PI3K-mediated stimulation of Ca2+ channel and the resulting increase in cytosolic Ca2+ concentration are blocked by the anti-PIP3 antibody. Mutants of PI3K transfected into vascular myocytes also revealed the essential role of the lipid-kinase activity of PI3K in Ang II-induced Ca2+ responses. These results suggest that PIP3 is necessary and sufficient to activate a Ca2+ influx in vascular myocytes stimulated by Ang II.
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MESH Headings
- Androstadienes/pharmacology
- Angiotensin II/pharmacology
- Animals
- Barium/metabolism
- Calcium/metabolism
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/physiology
- Calmodulin-Binding Proteins/pharmacology
- Cells, Cultured/drug effects
- Cells, Cultured/physiology
- Class Ib Phosphatidylinositol 3-Kinase
- Cytosol/metabolism
- Dihydropyridines/pharmacology
- Enzyme Inhibitors/pharmacology
- Ion Channel Gating/drug effects
- Ion Transport/drug effects
- Isoenzymes/antagonists & inhibitors
- Isoenzymes/genetics
- Isoenzymes/physiology
- Lipid Metabolism
- Membrane Potentials/drug effects
- Muscle, Smooth, Vascular/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/physiology
- Nerve Tissue Proteins/pharmacology
- Neurogranin
- Patch-Clamp Techniques
- Phosphatidylinositol 3-Kinases/genetics
- Phosphatidylinositol 3-Kinases/physiology
- Phosphatidylinositol Phosphates/antagonists & inhibitors
- Phosphatidylinositol Phosphates/pharmacology
- Phosphatidylinositol Phosphates/physiology
- Phosphoinositide-3 Kinase Inhibitors
- Phosphorylation/drug effects
- Portal Vein
- Protein Processing, Post-Translational/drug effects
- Rats
- Rats, Wistar
- Recombinant Fusion Proteins/physiology
- Substrate Specificity
- Transfection
- Wortmannin
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Affiliation(s)
- Catherine Le Blanc
- Laboratoire de Signalisation et Interactions Cellulaires, Université de Bordeaux II, Bordeaux, France
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8
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Abstract
Vanadate is a commonly used Ca2+ pump blocker, exerting a substantial effect on Ca2+ extrusion at millimolar concentrations in human red cells. At such levels, vanadate also seems to open an L type-like Ca2+ channel in these cells (J Biol Chem 257 (1982) 7414; Gen Physiol Biophys 16 (1997) 359). Since neither a dose-dependence effect nor a metabolic requirement for the latter action could be found in the literature, we have addressed this matter in the present work. Accordingly, vanadate action on Ca2+ entry was systematically investigated in both young and old human red cells after metabolic depletion. Although vanadate enhanced Ca2+ entry indifferently in either cell type, a distinct over-all effect was paradoxically found depending on whether or not metabolic substrates that give rise to ATP were present. In ATP-depleted cells, unlike with ATP-containing cells, vanadate-stimulated Ca2+ entry was neither blocked by raising external K+ nor by adding voltage-dependent Ca2+ channel blockers (nifedipine, calciseptine, FTX3.3) or compounds affecting polyphosphoinositide metabolism (Li+, neomycin). Likewise, full substitution of external Na+ by other cations did not inhibit vanadate-enhanced Ca2+ entry. Regardless of the cell age, stimulation by vanadate depended strongly on internal Na+ (0-30 mM). Vanadate stimulation was significantly reduced (about 55%) by heparin (10 mg/ml) only in young cells and by ryanodine (about 35%, 250 microM) in old cells. The results suggest presence of a new vanadate-induced Ca2+ entry pathway in ATP-depleted cells.
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Affiliation(s)
- Pedro J Romero
- Laboratory of Membrane Physiology, Institute of Experimental Biology, Faculty of Sciences, Central University of Venezuela, Aptdo. 47114, Caracas 1041-A, Venezuela.
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Huynh H, Wang X, Li W, Bottini N, Williams S, Nika K, Ishihara H, Godzik A, Mustelin T. Homotypic secretory vesicle fusion induced by the protein tyrosine phosphatase MEG2 depends on polyphosphoinositides in T cells. J Immunol 2004; 171:6661-71. [PMID: 14662869 DOI: 10.4049/jimmunol.171.12.6661] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Sec14p homology domains are found in a large number of proteins from plants, yeast, invertebrates, and higher eukaryotes. We report that the N-terminal Sec14p homology domain of the human protein tyrosine phosphatase PTP-MEG2 binds phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) in vitro and colocalizes with this lipid on secretory vesicle membranes in intact cells. Point mutations that prevented PtdIns(3,4,5)P(3) binding abrogated the capacity of PTP-MEG2 to induce homotypic secretory vesicle fusion in cells. Inhibition of cellular PtdIns(3,4,5)P(3) synthesis also rapidly reversed the effect of PTP-MEG2 on secretory vesicles. Finally, we show that several different phosphoinositide kinases colocalize with PTP-MEG2, thus allowing for local synthesis of PtdIns(3,4,5)P(3) in secretory vesicle membranes. We suggest that PTP-MEG2 through its Sec14p homology domain couples inositide phosphorylation to tyrosine dephosphorylation and the regulation of intracellular traffic of the secretory pathway in T cells.
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Affiliation(s)
- Huong Huynh
- Program of Signal Transduction, Cancer Research Center, The Burnham Institute, La Jolla, CA 92037, USA
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Momose H, Kurosu H, Tsujimoto N, Kontani K, Tsujita K, Nishina H, Katada T. Dual Phosphorylation of Phosphoinositide 3-Kinase Adaptor Grb2-Associated Binder 2 Is Responsible for Superoxide Formation Synergistically Stimulated by Fcγ and Formyl-Methionyl-Leucyl-Phenylalanine Receptors in Differentiated THP-1 Cells. J Immunol 2003; 171:4227-34. [PMID: 14530346 DOI: 10.4049/jimmunol.171.8.4227] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The class Ia phosphoinositide (PI) 3-kinase consisting of p110 catalytic and p85 regulatory subunits is activated by Tyr kinase-linked membrane receptors such as FcgammaRII through the association of p85 with the phosphorylated receptors or adaptors. The heterodimeric PI 3-kinase is also activated by G protein-coupled chemotactic fMLP receptors, and activation of the lipid kinase plays an important role in various immune responses, including superoxide formation in neutrophils. Although fMLP-induced superoxide formation is markedly enhanced in FcgammaRII-primed neutrophils, the molecular mechanisms remain poorly characterized. In this study, we identified two Tyr-phosphorylated proteins, c-Cbl (Casitas B-lineage lymphoma) and Grb2-associated binder 2 (Gab2), as PI 3-kinase adaptors that are Tyr phosphorylated upon the stimulation of FcgammaRII in differentiated neutrophil-like THP-1 cells. Interestingly, Gab2 was, but c-Cbl was not, further Ser/Thr phosphorylated by fMLP. Thus, the adaptor Gab2 appeared to be dually phosphorylated at the Ser/Thr and Tyr residues through the two different types of membrane receptors. The Ser/Thr phosphorylation of Gab2 required the activation of extracellular signal-regulated kinase, and fMLP receptor stimulation indeed activated extracellular signal-regulated kinase in the cells. Enhanced superoxide formation in response to Fcgamma and fMLP was markedly attenuated when the Gab2 Ser/Thr phosphorylation was inhibited. These results show the importance of the dual phosphorylation of PI 3-kinase adaptor Gab2 for the enhanced superoxide formation in neutrophil-type cells.
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Affiliation(s)
- Haruka Momose
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
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11
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Zambrzycka A, Kacprzak M. Apolipoprotein E4 and A beta peptide 1-42 inhibit polyphosphoinositide biosynthesis in rat brain cortex. Pol J Pharmacol 2003; 55:911-3. [PMID: 14704486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Revised: 11/03/2003] [Indexed: 04/27/2023]
Abstract
Polyphosphoinositides synthesized by phosphatidylinositol 4-kinase, EC 2.7.1.67 (PI4K) and phosphatidylinositol 4-phosphate 5-kinase, EC 2.7.1.68 (PIP5K) are involved in cell signaling and cytoskeleton function. In this study, the effect of apolipoprotein E4 (apoE4) and amyloid beta peptide A beta 1-42 on PI4K and PIP5K activity in cortical synaptic plasma membranes from rat brain was investigated. The results indicated that 0.25 microM apoE4 inhibited PI4K and PIP5K by 40% and 30%, respectively, but 25 microM A beta 1-42 decreased exclusively PI4K activity by 20%. Although the mechanism of apoE4 and A beta action is unknown and needs future investigation, this study suggests that free radical-dependent protein oxidation may be involved in alteration of these enzymes.
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Affiliation(s)
- Agata Zambrzycka
- Department of Cellular Signaling, Medical Research Center, Polish Academy of Sciences, Pawińskiego 5, PL 02-106 Warsaw, Poland.
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12
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Abstract
Phosphatidylinositol-3-phosphate (PtdIns-3-P) is considered as a lipid constitutively present on endosomes; it does not seem to have a dynamic role in signalling. In contrast, phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P(3)) plays a crucial role in different signalling pathways including translocation of the glucose transporter protein GLUT4 to the plasma membrane upon insulin receptor activation. GLUT4 translocation requires activation of two distinct pathways involving phosphatidylinositol 3-kinase (PI 3-K) and the small GTP-binding protein TC10, respectively. The contribution of each pathway remains to be elucidated. Here we show that insulin specifically induces the formation of PtdIns-3-P in insulin- responsive cells. The insulin-mediated formation of PtdIns-3-P occurs through the activation of TC10 at the lipid rafts subdomain of the plasma membrane. Exogenous PtdIns-3-P induces the plasma membrane translocation of both overexpressed and endogenous GLUT4. These data indicate that PtdIns-3-P is specifically produced downstream from insulin-mediated activation of TC10 to promote the plasma membrane translocation of GLUT4. These results give a new insight into the intracellular role of PtdIns-3-P and shed light on some aspects of insulin signalling so far not completely understood.
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Affiliation(s)
- Tania Maffucci
- The Sackler Institute, University College London, 5 University Street, London WC1E 6JJ, UK
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13
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Abstract
The monomeric GTPase Rac and the lipid kinase phosphoinositide 3-kinase (PI3K) are intracellular signalling enzymes that each regulate a huge range of cellular functions. Their signalling pathways overlap. Several pathways lead from PI3K activation via the production of the lipid second messenger phosphatidylinositol (3,4,5)-triphosphate (PtdIns(3,4,5)P(3)) to the activation of guanine-nucleotide exchange factors (GEFs) that activate Rac. Vice versa, Rac can also stimulate the activation of PI3K, although the mechanism for this is unclear. We review here the evidence that links PI3K and Rac signalling pathways.
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Affiliation(s)
- Heidi C E Welch
- Inositide Laboratory, Signalling Programme, The Babraham Institute, Cambridge CB2 4AT, UK.
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14
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Jung JY, Kim YW, Kwak JM, Hwang JU, Young J, Schroeder JI, Hwang I, Lee Y. Phosphatidylinositol 3- and 4-phosphate are required for normal stomatal movements. Plant Cell 2002; 14:2399-412. [PMID: 12368494 PMCID: PMC151225 DOI: 10.1105/tpc.004143] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2002] [Accepted: 07/01/2002] [Indexed: 05/18/2023]
Abstract
Phosphatidylinositol (PI) metabolism plays a central role in signaling pathways in both animals and higher plants. Stomatal guard cells have been reported to contain PI 3-phosphate (PI3P) and PI 4-phosphate (PI4P), the products of PI 3-kinase (PI3K) and PI 4-kinase (PI4K) activities. In this study, we tested the roles of PI3P and PI4P in stomatal movements. Both wortmannin (WM) and LY294002 inhibited PI3K and PI4K activities in guard cells and promoted stomatal opening induced by white light or the circadian clock. WM and LY294002 also inhibited stomatal closing induced by abscisic acid (ABA). Furthermore, overexpression in guard cells of GFP:EBD (green fluorescent protein:endosome binding domain of human EEA1) or GFP:FAPP1PH (PI-four-P adaptor protein-1 pleckstrin homology domain), which bind to PI3P and PI4P, respectively, increased stomatal apertures under darkness and white light and partially inhibited stomatal closing induced by ABA. The reduction in ABA-induced stomatal closing with reduced levels of PI monophosphate seemed to be attributable, at least in part, to impaired Ca(2+) signaling, because WM and LY294002 inhibited ABA-induced cytosolic Ca(2+) increases in guard cells. These results suggest that PI3P and PI4P play an important role in the modulation of stomatal closing and that reductions in the levels of functional PI3P and PI4P enhance stomatal opening.
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Affiliation(s)
- Ji-Yul Jung
- Division of Molecular Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
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Naga Prasad SV, Laporte SA, Chamberlain D, Caron MG, Barak L, Rockman HA. Phosphoinositide 3-kinase regulates beta2-adrenergic receptor endocytosis by AP-2 recruitment to the receptor/beta-arrestin complex. J Cell Biol 2002; 158:563-75. [PMID: 12163475 PMCID: PMC2173831 DOI: 10.1083/jcb.200202113] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Internalization of beta-adrenergic receptors (betaARs) occurs by the sequential binding of beta-arrestin, the clathrin adaptor AP-2, and clathrin. D-3 phosphoinositides, generated by the action of phosphoinositide 3-kinase (PI3K) may regulate the endocytic process; however, the precise molecular mechanism is unknown. Here we demonstrate that betaARKinase1 directly interacts with the PIK domain of PI3K to form a cytosolic complex. Overexpression of the PIK domain displaces endogenous PI3K from betaARK1 and prevents betaARK1-mediated translocation of PI3K to activated beta2ARs. Furthermore, disruption of the betaARK1/PI3K interaction inhibits agonist-stimulated AP-2 adaptor protein recruitment to the beta2AR and receptor endocytosis without affecting the internalization of other clathrin dependent processes such as internalization of the transferrin receptor. In contrast, AP-2 recruitment is enhanced in the presence of D-3 phospholipids, and receptor internalization is blocked in presence of the specific phosphatidylinositol-3,4,5-trisphosphate lipid phosphatase PTEN. These findings provide a molecular mechanism for the agonist-dependent recruitment of PI3K to betaARs, and support a role for the localized generation of D-3 phosphoinositides in regulating the recruitment of the receptor/cargo to clathrin-coated pits.
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16
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Brauweiler A, Tamir I, Marschner S, Helgason CD, Cambier JC. Partially distinct molecular mechanisms mediate inhibitory FcgammaRIIB signaling in resting and activated B cells. J Immunol 2001; 167:204-11. [PMID: 11418650 DOI: 10.4049/jimmunol.167.1.204] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
FcgammaRIIB functions as an inhibitory receptor to dampen B cell Ag receptor signals and immune responses. Accumulating evidence indicates that ex vivo B cells require the inositol 5-phosphatase, Src homology domain 2-containing inositol 5-phosphatase (SHIP), for FcgammaRIIB-mediated inhibitory signaling. However, we report here that LPS-activated primary B cells do not require SHIP and thus differ from resting B cells. SHIP-deficient B cell blasts display efficient FcgammaRIIB-dependent inhibition of calcium mobilization as well as Akt and extracellular signal-related protein kinase phosphorylation. Surprisingly, FcgammaRIIB-dependent degradation of phosphatidylinositol 3,4,5-trisphosphate and conversion into phosphatidylinositol 3,4-bisphosphate occur in SHIP-deficient B cell blasts, demonstrating the function of an additional inositol 5-phosphatase. Further analysis reveals that while resting cells express only SHIP, B cell blasts also express the recently described inositol 5-phosphatase, SHIP-2. Finally, data suggest that both SHIP-2 and SHIP can mediate downstream biologic consequences of FcgammaRIIB signaling, including inhibition of the proliferative response.
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Affiliation(s)
- A Brauweiler
- Department of Immunology, National Jewish Medical and Research Center, Denver, CO 80206, USA
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17
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Venkateswarlu K, Cullen PJ. Signalling via ADP-ribosylation factor 6 lies downstream of phosphatidylinositide 3-kinase. Biochem J 2000; 345 Pt 3:719-24. [PMID: 10642533 PMCID: PMC1220809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
ADP-ribosylation factor (ARF) 6 regulates plasma membrane trafficking and cortical actin formation by cycling between inactive GDP and active GTP-bound conformations. Here we show that agonist stimulation of phosphatidylinositide 3-kinase (PI 3-kinase) activates a pathway that leads to ARF6 activation. We also describe experiments that propose a central role in this pathway for the PI 3-kinase-dependent plasma membrane recruitment of the cytohesin-1 family of PtdIns(3,4,5)P(3)-binding ARF-exchange factors.
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Affiliation(s)
- K Venkateswarlu
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, U.K
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18
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Nakamura K, Brauweiler A, Cambier JC. Effects of Src homology domain 2 (SH2)-containing inositol phosphatase (SHIP), SH2-containing phosphotyrosine phosphatase (SHP)-1, and SHP-2 SH2 decoy proteins on Fc gamma RIIB1-effector interactions and inhibitory functions. J Immunol 2000; 164:631-8. [PMID: 10623804 DOI: 10.4049/jimmunol.164.2.631] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Coaggregation of Fc gamma RIIB1 with B cell Ag receptors (BCR) leads to inhibition of BCR-mediated signaling via recruitment of Src homology domain 2 (SH2)-containing phosphatases. In vitro peptide binding experiments using phosphotyrosine-containing sequences derived from the immunoreceptor tyrosine-based inhibitory motif (ITIM) known to mediate Fc gamma RIIB1 effects suggest that the receptor uses SH2-containing inositol phosphatase (SHIP) and SH2-containing phosphotyrosine phosphatase (SHP)-1, as well as SHP-2 as effectors. In contrast, coimmunoprecipitation studies of receptor-effector associations suggest that the predominant Fc gamma RIIB1 effector protein is SHIP. However, biologically significant interactions may be lost in such studies if reactants' dissociation rates (Kd) are high. Thus, it is unclear to what extent these assays reflect the relative recruitment of SHIP, SHP-1, and SHP-2 to the receptor in vivo. As an alternative approach to this question, we have studied the effects of ectopically expressed SHIP, SHP-1, or SHP-2 SH2-containing decoy proteins on Fc gamma RIIB1 signaling. Results demonstrate the SHIP is the predominant intracellular ligand for the phosphorylated Fc gamma RIIB1 ITIM, although the SHP-2 decoy exhibits some ability to bind Fc gamma RIIB1 and block Fc receptor function. The SHIP SH2, while not affecting Fc gamma RIIB1 tyrosyl phosphorylation, blocks receptor-mediated recruitment of SHIP, SHIP phosphorylation, recruitment of p52 Shc, phosphatidylinositol 3,4,5-trisphosphate hydrolysis, inhibition of mitogen-activated protein kinase activation, and, albeit more modestly, Fc gamma RIIB1 inhibition of Ca2+ mobilization. Taken together, results implicate ITIM interactions with SHIP as a major mechanism of Fc gamma RIIB1-mediated inhibitory signaling.
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MESH Headings
- Animals
- Calcium/antagonists & inhibitors
- Calcium/metabolism
- Cell Line
- Hydrolysis
- Intracellular Signaling Peptides and Proteins
- Lymphoma, B-Cell/enzymology
- Lymphoma, B-Cell/genetics
- Mice
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Mitogen-Activated Protein Kinases/metabolism
- Oligopeptides
- Peptides/genetics
- Phosphatidylinositol Phosphates/antagonists & inhibitors
- Phosphatidylinositol Phosphates/metabolism
- Phosphoric Monoester Hydrolases/antagonists & inhibitors
- Phosphoric Monoester Hydrolases/genetics
- Phosphoric Monoester Hydrolases/immunology
- Phosphorylation
- Protein Binding/immunology
- Protein Tyrosine Phosphatase, Non-Receptor Type 11
- Protein Tyrosine Phosphatase, Non-Receptor Type 6
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Protein Tyrosine Phosphatases/biosynthesis
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/immunology
- Receptor Aggregation/immunology
- Receptors, Antigen, B-Cell/metabolism
- Receptors, IgG/antagonists & inhibitors
- Receptors, IgG/metabolism
- Receptors, IgG/physiology
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/pharmacology
- SH2 Domain-Containing Protein Tyrosine Phosphatases
- Tumor Cells, Cultured
- Tyrosine/antagonists & inhibitors
- Tyrosine/metabolism
- src Homology Domains/genetics
- src Homology Domains/immunology
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Affiliation(s)
- K Nakamura
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA
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19
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Sorensen SD, Linseman DA, McEwen EL, Heacock AM, Fisher SK. Inhibition of beta(2)-adrenergic and muscarinic cholinergic receptor endocytosis after depletion of phosphatidylinositol bisphosphate. J Pharmacol Exp Ther 1999; 290:603-10. [PMID: 10411568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023] Open
Abstract
Recent evidence supporting a role for phosphoinositides in the endocytosis of phospholipase C-coupled receptors has prompted an investigation of whether there exists a similar requirement for the internalization of adenylyl cyclase-linked receptors. When 1321N1 astrocytoma cells, which possess both muscarinic cholinergic receptors (mAChRs) that couple to phospholipase C and beta-adrenergic receptors (beta(2)-ARs) linked to adenylyl cyclase, were pretreated with wortmannin (WT) at a concentration known to inhibit phosphatidylinositol 4-kinase activity, the labeling of both phosphatidylinositol 4-phosphate and phosphatidylinositol 4, 5-bisphosphate (PIP(2)) was reduced. Stimulation of phosphoinositide breakdown by activation of mAChRs in WT-pretreated cells led to a further depletion of PIP(2). As previously demonstrated for SH-SY5Y neuroblastoma, inclusion of WT inhibited the endocytosis of mAChRs in 1321N1 cells by >85%. In contrast, the internalization of beta(2)-ARs was only partially ( approximately 30%) prevented. However, when the concentration of PIP(2) was further reduced by exposure of WT-pretreated 1321N1 cells to a muscarinic agonist, the endocytosis of beta(2)-ARs was substantially inhibited (>70%). Lower concentrations of WT (100 nM) that were sufficient to fully inhibit phosphatidylinositol 3-kinase activity had no effect on either phosphoinositide synthesis or receptor endocytosis. The results indicate that the agonist-induced endocytosis of an adenylyl cyclase-linked receptor such as the beta(2)-AR, like that of the phospholipase C-coupled mAChR, is dependent on the synthesis of phosphoinositides and, in particular, that of PIP(2).
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Affiliation(s)
- S D Sorensen
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
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20
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Niggli V, Keller H. The phosphatidylinositol 3-kinase inhibitor wortmannin markedly reduces chemotactic peptide-induced locomotion and increases in cytoskeletal actin in human neutrophils. Eur J Pharmacol 1997; 335:43-52. [PMID: 9371545 DOI: 10.1016/s0014-2999(97)01169-2] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To define a possible role of the enzyme phosphatidylinositol 3-kinase (PI 3-kinase) in motile functions of neutrophils, we have used a potent inhibitor of this enzyme, [1S-(1alpha,6b alpha,9a beta,11alpha,11bbeta)]-1-(acetyloxy)-1,6b,7,8,9a,10,11 ,11b-octahydro-1-(methoxymethyl)-9a,11b-dimethyl-3H-furo[4,3,2-de]indeno [4,5-h]-2-benzopyran-3,6,9-trione (wortmannin). Wortmannin markedly attenuated chemotactic peptide-induced development of polarity, locomotion and increases in cytoskeletal actin and alpha-actinin in human neutrophils at low, nM, concentrations (ED50 = 4-40 nM; 0.4-3 pmol/10(6) cells). The increase in cytoskeletal actin induced by phorbol-12-myristate-13-acetate in contrast was not affected by wortmannin (18 pmol/10[6] cells). Moreover, the increase in total F-actin induced by an incubation for 1 min with chemotactic peptide was much less sensitive to wortmannin than increases in cytoskeletal actin; 80 pmol/10(6) cells were necessary for half-maximal inhibition. Wortmannin thus appears to primarily affect F-actin organization, rather than polymerization. Inhibition of development of polarity by wortmannin correlated with inhibition of production of phosphatidylinositol 3,4,5-trisphosphate. According to our findings, activation of a wortmannin-sensitive target, very likely PI 3-kinase, is required for optimal chemotactic peptide-induced neutrophil motility.
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Affiliation(s)
- V Niggli
- Department of Pathology, University of Bern, Switzerland.
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21
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Montsarrat N, Racaud-Sultan C, Mauco G, Plantavid M, Payrastre B, Breton-Douillon M, Chap H. Calpains are involved in phosphatidylinositol 3',4'-bisphosphate synthesis dependent on the alpha IIb beta 3 integrin engagement in thrombin-stimulated platelets. FEBS Lett 1997; 404:23-6. [PMID: 9074630 DOI: 10.1016/s0014-5793(97)00079-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In thrombin-stimulated platelets alpha IIb beta 3 integrin engagement triggers both phosphatidylinositol 3',4'-bisphosphate synthesis and calpain activation. We checked the possible involvement of calpains in phosphatidylinositol 3-kinase signalling pathway using a cell permeant specific inhibitor of calpains, calpeptin. In conditions where thrombin-induced platelet aggregation and secretion were not impaired, we found a dose-dependent inhibition of phosphatidylinositol 3,4-bisphosphate synthesis by calpeptin from 50 micrograms/ml. Moreover, pretreatment of platelets by both calpeptin and the peptide RGDS, an inhibitor of fibrinogen binding to activated alpha IIb beta 3 integrin, did not induce additive effects on phosphatidylinositol 3,4-bisphosphate inhibition. Finally, the p85 regulatory subunit of phosphatidylinositol 3-kinase was still translocated to the cytoskeleton in calpeptin-treated platelets. These data indicate that calpains are involved in the regulation of alpha IIb beta 3 integrin-dependent phosphatidylinositol 3-kinase signalling pathway.
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Affiliation(s)
- N Montsarrat
- Institut Fédératif de Recherche en Immunologie Cellulaire et Moléculaire, INSERM, Unité 326, Hôpital Purpan, Toulouse, France
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22
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Herrera-Velit P, Reiner NE. Bacterial lipopolysaccharide induces the association and coordinate activation of p53/56lyn and phosphatidylinositol 3-kinase in human monocytes. J Immunol 1996; 156:1157-65. [PMID: 8557993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
p53/56lyn and other src family tyrosine kinases become activated in monocytes treated with LPS. In a variety of systems, phosphatidylinositol 3-kinase (PI 3-kinase) is believed to be a downstream effector of tyrosine kinases, and activation of PI 3-kinase results in increased levels of D3-phosphorylated metabolites of phosphatidylinositol (PtdIns). To examine whether LPS activates PI 3-kinase, freshly isolated human, peripheral blood monocytes were labeled in vitro with [32P]orthophosphate, and inositol phospholipids were detected after extraction and separation of lipids by TLC. Levels of PtdIns 3,4,5-trisphosphate (PtdIns 3,4,5-P3) were elevated within minutes of exposure of cells to LPS. Analysis of 32P-labeled lipid extracts of U937 cells by HPLC confirmed that levels of PtdIns 3,4,5-P3 increased rapidly following LPS treatment. Increased levels of PtdIns 3,4,5-P3 in LPS-treated cells resulted from an increase in the specific activity of PI 3-kinase. Thus, anti-PI 3-kinase immunoprecipitates prepared from unlabeled monocytes and assayed in an in vitro phosphorylation assay, using PtdIns as substrate, showed higher enzymatic activity when these were prepared from lysates of LPS-treated cells as compared with control cells. PI 3-kinase activity in immunoprecipitates was elevated as early as 2 min after LPS exposure and was dose dependent, with increased activity being observed at LPS concentrations as low as 10 pg/ml. Activation of PI 3-kinase involved signaling through the monocyte cell surface molecule CD14, since pretreatment of cells with Abs to CD14 abrogated LPS-induced increases in PtdIns 3,4,5-P3. Immunoprecipitates of p53/56lyn from LPS-treated cells showed a time-dependent and transient increase in PI 3-kinase activity assayed in vitro, coordinate with activation of p53/56lyn, indicating that LPS induces the association and simultaneous activation of these two enzymes in vivo. These findings indicate that monocytes respond to LPS with the rapid activation of PI 3-kinase, resulting in transient increases in levels of PtdIns 3,4,5-P3. This process is CD14 dependent and involves the physical association of PI 3-kinase with activated p53/56lyn.
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Affiliation(s)
- P Herrera-Velit
- Department of Medicine (Division of Infectious Diseases), University of British Columbia Faculties of Medicine and Science, Canada
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23
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Kozikowski AP, Kiddle JJ, Frew T, Berggren M, Powis G. Synthesis and biology of 1D-3-deoxyphosphatidylinositol: a putative antimetabolite of phosphatidylinositol-3-phosphate and an inhibitor of cancer cell colony formation. J Med Chem 1995; 38:1053-6. [PMID: 7707307 DOI: 10.1021/jm00007a001] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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24
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Abstract
The aim of these experiments was to investigate whether inositol lipids might mediate some of the effects of extracellular matrix (ECM) on cellular form and functions. The lipid phosphatidylinositol bisphosphate (PIP2) plays a role in cytoskeletal regulation while its hydrolysis products, diacylglycerol and inositol triphosphate, serve as second messengers. We therefore measured the effect of adhesion to fibronectin (FN) on PIP2 and its hydrolysis products, in the presence and absence of the soluble mitogen PDGF. PDGF induced a threefold increase in release of water-soluble inositol phosphates in C3H 10T1/2 fibroblasts when cells were attached to FN, but had little effect in suspended cells. Suppression of inositol phosphate release in unattached cells was not due to dysfunction of the PDGF receptor or failure to activate phospholipase C-gamma; PDGF induced similar tyrosine phosphorylation of PLC-gamma under both conditions. By contrast, the total mass of phosphatidylinositol bisphosphate (PIP2), the substrate for PLC-gamma, was found to decrease by approximately 80% when cells were detached from their ECM attachments and placed in suspension in the absence of PDGF. PIP2 levels were restored when suspended cells were replated on FN, demonstrating that the effect was reversible. Furthermore, a dramatic increase in synthesis of PIP2 could be measured in cells within 2 min after reattachment to FN in the absence of PDGF. These results show that FN acts directly to stimulate PIP2 synthesis, and that it also enhances PIP2 hydrolysis in response to PDGF. The increase in PIP2 induced by adhesion may mediate some of the known effects of FN on cell shape and cytoskeletal organization, while regulation of inositol lipid hydrolysis may provide a means for integrating hormone- and ECM-dependent signaling pathways.
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Affiliation(s)
- H P McNamee
- Program in Cell and Developmental Biology, Harvard Medical School, Boston, Massachusetts
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