1
|
Janmey PA, Bucki R, Radhakrishnan R. Regulation of actin assembly by PI(4,5)P2 and other inositol phospholipids: An update on possible mechanisms. Biochem Biophys Res Commun 2018; 506:307-314. [PMID: 30139519 DOI: 10.1016/j.bbrc.2018.07.155] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Revised: 06/21/2018] [Accepted: 07/31/2018] [Indexed: 01/15/2023]
Abstract
Actin cytoskeleton dynamics depend on a tight regulation of actin filament formation from an intracellular pool of monomers, followed by their linkage to each other or to cell membranes, followed by their depolymerization into a fresh pool of actin monomers. The ubiquitous requirement for continuous actin remodeling that is necessary for many cellular functions is orchestrated in large part by actin binding proteins whose affinity for actin is altered by inositol phospholipids, most prominently PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate). The kinetics of PI(4,5)P2 synthesis and hydrolysis, its lateral distribution within the lipid bilayer, and coincident detection of PI(4,5)P2 and another signal, all play a role in determining when and where a particular PI(4,5)P2-regulated protein is inactivated or activated to exert its effect on the actin cytoskeleton. This review summarizes a range of models that have been developed to explain how PI(4,5)P2 might function in the complex chemical and structural environment of the cell based on a combination of experiment and computational studies.
Collapse
Affiliation(s)
- Paul A Janmey
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA; Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
| | - Robert Bucki
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA; Department of Microbiological and Nanobiomedical Engineering, Medical University of Bialystok, Bialystok, Poland
| | - Ravi Radhakrishnan
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
| |
Collapse
|
2
|
Steringer JP, Lange S, Čujová S, Šachl R, Poojari C, Lolicato F, Beutel O, Müller HM, Unger S, Coskun Ü, Honigmann A, Vattulainen I, Hof M, Freund C, Nickel W. Key steps in unconventional secretion of fibroblast growth factor 2 reconstituted with purified components. eLife 2017; 6. [PMID: 28722655 PMCID: PMC5601999 DOI: 10.7554/elife.28985] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/14/2017] [Indexed: 12/31/2022] Open
Abstract
FGF2 is secreted from cells by an unconventional secretory pathway. This process is mediated by direct translocation across the plasma membrane. Here, we define the minimal molecular machinery required for FGF2 membrane translocation in a fully reconstituted inside-out vesicle system. FGF2 membrane translocation is thermodynamically driven by PI(4,5)P2-induced membrane insertion of FGF2 oligomers. The latter serve as dynamic translocation intermediates of FGF2 with a subunit number in the range of 8-12 FGF2 molecules. Vectorial translocation of FGF2 across the membrane is governed by sequential and mutually exclusive interactions with PI(4,5)P2 and heparan sulfates on opposing sides of the membrane. Based on atomistic molecular dynamics simulations, we propose a mechanism that drives PI(4,5)P2 dependent oligomerization of FGF2. Our combined findings establish a novel type of self-sustained protein translocation across membranes revealing the molecular basis of the unconventional secretory pathway of FGF2. DOI:http://dx.doi.org/10.7554/eLife.28985.001
Collapse
Affiliation(s)
| | - Sascha Lange
- Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany
| | - Sabína Čujová
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Chetan Poojari
- Department of Physics, University of Helsinki, Helsinki, Finland.,Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Fabio Lolicato
- Department of Physics, University of Helsinki, Helsinki, Finland.,Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Oliver Beutel
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | | | - Sebastian Unger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Ünal Coskun
- Paul Langerhans Institute Dresden, Helmholtz Zentrum München, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,Deutsches Zentrum fur Diabetesforschung, Neuherberg, Germany
| | - Alf Honigmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, Helsinki, Finland.,Department of Physics, Tampere University of Technology, Tampere, Finland.,MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark, Denmark, United Kingdom
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Christian Freund
- Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| |
Collapse
|
3
|
Slone EA, Pope MR, Fleming SD. Phospholipid scramblase 1 is required for β2-glycoprotein I binding in hypoxia and reoxygenation-induced endothelial inflammation. J Leukoc Biol 2015. [PMID: 26216936 DOI: 10.1189/jlb.3a1014-480r] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Multiple pathologic conditions, including hemorrhage, tumor angiogenesis, and ischemia-reperfusion events, will result in hypoxia and subsequent reperfusion. Previous studies have analyzed the lipid changes within whole tissues and indicated that ischemia-reperfusion altered tissue and cellular phospholipids. Using an in vitro cell culture model of hypoxia and reoxygenation, we examined the endothelial lipid changes. We hypothesized that phospholipid scramblase 1, a protein that regulates bilayer asymmetry, is involved in altering the phospholipids of endothelial cells during hypoxia, a component of ischemia, leading to β2-glycoprotein I and IgM binding and subsequent lipid-mediated, inflammatory responses. We have completed the first comprehensive study of steady-state phospholipid scramblase 1 mRNA levels, protein expression, and activity under conditions of hypoxia and reoxygenation. Phospholipid scramblase 1 regulates phosphatidylserine exposure in response to oxygen stress, leading to β2-glycoprotein I and IgM binding and lipid-mediated, inflammatory responses.
Collapse
Affiliation(s)
| | - Michael R Pope
- Division of Biology, Kansas State University, Manhattan, Kansas, USA
| | - Sherry D Fleming
- Division of Biology, Kansas State University, Manhattan, Kansas, USA
| |
Collapse
|
4
|
Jiao CY, Delaroche D, Burlina F, Alves ID, Chassaing G, Sagan S. Translocation and endocytosis for cell-penetrating peptide internalization. J Biol Chem 2009; 284:33957-65. [PMID: 19833724 DOI: 10.1074/jbc.m109.056309] [Citation(s) in RCA: 248] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell-penetrating peptides (CPPs) share the property of cellular internalization. The question of how these peptides reach the cytoplasm of cells is still widely debated. Herein, we have used a mass spectrometry-based method that enables quantification of internalized and membrane-bound peptides. Internalization of the most used CPP was studied at 37 degrees C (endocytosis and translocation) and 4 degrees C (translocation) in wild type and proteoglycan-deficient Chinese hamster ovary cells. Both translocation and endocytosis are internalization pathways used by CPP. The choice of one pathway versus the other depends on the peptide sequence (not the number of positive changes), the extracellular peptide concentration, and the membrane components. There is no relationship between the high affinity of these peptides for the cell membrane and their internalization efficacy. Translocation occurs at low extracellular peptide concentration, whereas endocytosis, a saturable and cooperative phenomenon, is activated at higher concentrations. Translocation operates in a narrow time window, which implies a specific lipid/peptide co-import in cells.
Collapse
Affiliation(s)
- Chen-Yu Jiao
- Laboratoire des Biomolécules, Université Pierre et Marie Curie (Paris 6), 75005 Paris, France
| | | | | | | | | | | |
Collapse
|
5
|
Aminoglycoside-induced phosphatidylserine externalization in sensory hair cells is regionally restricted, rapid, and reversible. J Neurosci 2008; 28:9939-52. [PMID: 18829952 DOI: 10.1523/jneurosci.1124-08.2008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The aminophospholipid phosphatidylserine (PS) is normally restricted to the inner leaflet of the plasma membrane. During certain cellular processes, including apoptosis, PS translocates to the outer leaflet and can be labeled with externally applied annexin V, a calcium-dependent PS-binding protein. In mouse cochlear cultures, annexin V labeling reveals that the aminoglycoside antibiotic neomycin induces rapid PS externalization, specifically on the apical surface of hair cells. PS externalization is observed within approximately 75 s of neomycin perfusion, first on the hair bundle and then on membrane blebs forming around the apical surface. Whole-cell capacitance also increases significantly within minutes of neomycin application, indicating that blebbing is accompanied by membrane addition to the hair cell surface. PS externalization and membrane blebbing can, nonetheless, occur independently. Pretreating hair cells with calcium chelators, a procedure that blocks mechanotransduction, or overexpressing a phosphatidylinositol 4,5-biphosphate (PIP2)-binding pleckstrin homology domain, can reduce neomycin-induced PS externalization, suggesting that neomycin enters hair cells via transduction channels, clusters PIP2, and thereby activates lipid scrambling. The effects of short-term neomycin treatment are reversible. After neomycin washout, PS is no longer detected on the apical surface, apical membrane blebs disappear, and surface-bound annexin V is internalized, distributing throughout the supranuclear cytoplasm of the hair cell. Hair cells can therefore repair, and recover from, neomycin-induced surface damage. Hair cells lacking myosin VI, a minus-end directed actin-based motor implicated in endocytosis, can also recover from brief neomycin treatment. Internalized annexin V, however, remains below the apical surface, thereby pinpointing a critical role for myosin VI in the transport of endocytosed material away from the periphery of the hair cell.
Collapse
|
6
|
Hermelink A, Brezesinski G. Do unsaturated phosphoinositides mix with ordered phosphadidylcholine model membranes? J Lipid Res 2008; 49:1918-25. [DOI: 10.1194/jlr.m700527-jlr200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
7
|
Yaradanakul A, Wang TM, Lariccia V, Lin MJ, Shen C, Liu X, Hilgemann DW. Massive Ca-induced membrane fusion and phospholipid changes triggered by reverse Na/Ca exchange in BHK fibroblasts. ACTA ACUST UNITED AC 2008; 132:29-50. [PMID: 18562498 PMCID: PMC2442179 DOI: 10.1085/jgp.200709865] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Baby hamster kidney (BHK) fibroblasts increase their cell capacitance by 25-100% within 5 s upon activating maximal Ca influx via constitutively expressed cardiac Na/Ca exchangers (NCX1). Free Ca, measured with fluo-5N, transiently exceeds 0.2 mM with total Ca influx amounting to approximately 5 mmol/liter cell volume. Capacitance responses are half-maximal when NCX1 promotes a free cytoplasmic Ca of 0.12 mM (Hill coefficient approximately 2). Capacitance can return to baseline in 1-3 min, and responses can be repeated several times. The membrane tracer, FM 4-64, is taken up during recovery and can be released at a subsequent Ca influx episode. Given recent interest in signaling lipids in membrane fusion, we used green fluorescent protein (GFP) fusions with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and diacylglycerol (DAG) binding domains to analyze phospholipid changes in relation to these responses. PI(4,5)P(2) is rapidly cleaved upon activating Ca influx and recovers within 2 min. However, PI(4,5)P(2) depletion by activation of overexpressed hM1 muscarinic receptors causes only little membrane fusion, and subsequent fusion in response to Ca influx remains massive. Two results suggest that DAG may be generated from sources other than PI(4,5)P in these protocols. First, acylglycerols are generated in response to elevated Ca, even when PI(4,5)P(2) is metabolically depleted. Second, DAG-binding C1A-GFP domains, which are brought to the cell surface by exogenous ligands, translocate rapidly back to the cytoplasm in response to Ca influx. Nevertheless, inhibitors of PLCs and cPLA2, PI(4,5)P(2)-binding peptides, and PLD modification by butanol do not block membrane fusion. The cationic agents, FM 4-64 and heptalysine, bind profusely to the extracellular cell surface during membrane fusion. While this binding might reflect phosphatidylserine (PS) "scrambling" between monolayers, it is unaffected by a PS-binding protein, lactadherin, and by polylysine from the cytoplasmic side. Furthermore, the PS indicator, annexin-V, binds only slowly after fusion. Therefore, we suggest that the luminal surfaces of membrane vesicles that fuse to the plasmalemma may be rather anionic. In summary, our results provide no support for any regulatory or modulatory role of phospholipids in Ca-induced membrane fusion in fibroblasts.
Collapse
Affiliation(s)
- Alp Yaradanakul
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | | | | | | | | | | | | |
Collapse
|
8
|
Chung SM, Bae ON, Lim KM, Noh JY, Lee MY, Jung YS, Chung JH. Lysophosphatidic Acid Induces Thrombogenic Activity Through Phosphatidylserine Exposure and Procoagulant Microvesicle Generation in Human Erythrocytes. Arterioscler Thromb Vasc Biol 2007; 27:414-21. [PMID: 17110600 DOI: 10.1161/01.atv.0000252898.48084.6a] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
OBJECTIVE Although erythrocytes have been suggested to play a role in blood clotting, mediated through phosphatidylserine (PS) exposure and/or PS-bearing microvesicle generation, an endogenous substance that triggers the membrane alterations leading to a procoagulant activity in erythrocytes has not been reported. We now demonstrated that lysophosphatidic acid (LPA), an important lipid mediator in various pathophysiological processes, induces PS exposure and procoagulant microvesicle generation in erythrocytes, which represent a biological significance resulting in induction of thrombogenic activity. METHODS AND RESULTS In human erythrocytes, LPA treatment resulted in PS exposure on remnant cells and PS-bearing microvesicle generation in a concentration-dependent manner. Consistent with the microvesicle generation, scanning electron microscopic study revealed that LPA treatment induced surface changes, alteration of normal discocytic shape into echinocytes followed by spherocytes. Surprisingly, chelation of intracellular calcium did not affect LPA-induced PS exposure and microvesicle generation. On the other hand, protein kinase C (PKC) inhibitors significantly reduced PS exposure and microvesicle generation induced by LPA, reflecting the role of calcium-independent PKC. Activation of PKC was confirmed by Western blot analysis showing translocation of calcium-independent isoform, PKCzeta, to erythrocyte membrane. The activity of flippase, which is important in the maintenance of membrane asymmetry, was also inhibited by LPA. Furthermore, LPA-exposed erythrocytes actually potentiated the thrombin generation as determined by prothrombinase assay and accelerated the coagulation process initiated by recombinant human tissue factor in plasma. The adherence of erythrocytes to endothelial cells, another important feature of thrombogenic process, was also stimulated by LPA treatment. CONCLUSIONS These results suggested that LPA-exposed erythrocytes could make an important contribution to thrombosis mediated through PS exposure and procoagulant microvesicle generation.
Collapse
Affiliation(s)
- Seung-Min Chung
- College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | | | | | | | | | | | | |
Collapse
|
9
|
Janmey PA, Kinnunen PKJ. Biophysical properties of lipids and dynamic membranes. Trends Cell Biol 2006; 16:538-46. [PMID: 16962778 DOI: 10.1016/j.tcb.2006.08.009] [Citation(s) in RCA: 281] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 08/14/2006] [Accepted: 08/24/2006] [Indexed: 10/24/2022]
Abstract
The lipid bilayer is a 3D assembly with a rich variety of physical features that modulate cell signaling and protein function. Lateral and transverse forces within the membrane are significant and change rapidly as the membrane is bent or stretched and as new constituents are added, removed or chemically modified. Recent studies have revealed how differences in structure between the two leaflets of the bilayer and between different areas of the bilayer can interact together with membrane deformation to alter the activities of transmembrane channels and peripheral membrane binding proteins. Here, we highlight some recent reports that the physical properties of the membrane can help control the function of transmembrane proteins and the motor-dependent elongation of internal organelles, such as the endoplasmic reticulum.
Collapse
Affiliation(s)
- P A Janmey
- Institute for Medicine and Engineering, Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | | |
Collapse
|
10
|
Bucki R, Pastore JJ, Giraud F, Janmey PA, Sulpice JC. Involvement of the Na+/H+ exchanger in membrane phosphatidylserine exposure during human platelet activation. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:195-204. [PMID: 16459134 PMCID: PMC3118474 DOI: 10.1016/j.bbalip.2005.12.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Revised: 11/29/2005] [Accepted: 12/20/2005] [Indexed: 11/29/2022]
Abstract
Platelet membrane phosphatidylserine (PS) exposure that regulates the production of thrombin represents an important link between platelet activation and the coagulation cascade. Here, we have evaluated the involvement of the Na+/H+ exchanger (NHE) in this process in human platelets. PS exposure induced in human platelets by thrombin, TRAP, collagen or TRAP+ collagen was abolished in a Na+ -free medium. Inhibition of the Na+/H+ exchanger (NHE) by 5-(N-Ethyl-N-Isopropyl) Amiloride (EIPA) reduced significantly PS exposure, whereas monensin or nigericin, which mimic or cause activation of NHE, respectively, reproduced the agonist effect. These data suggest a role for Na+ influx through NHE activation in the mechanism of PS exposure. This newly identified pathway does not discount a role for Ca2+, whose cytosolic concentration varies together with that of Na+ after agonist stimulation. Ca2+ deprivation from the incubation medium only attenuated PS exposure induced by thrombin, measured from the uptake of FM1-43 (a marker of phospholipid scrambling independent of external Ca2+). Surprisingly, removal of external Ca2+ partially reduced FM1-43 uptake induced by A23187, known as a Ca2+ ionophore. The residual effect can be attributed to an increase in [Na+]i mediated by the ionophore due to a lack of its specificity. Finally, phosphatidylinositol 4,5-bisphosphate (PIP2), previously reported as a target for Ca2+ in the induction of phospholipid scrambling, was involved in PS exposure through a regulation of NHE activity. All these results would indicate that the mechanism that results in PS exposure uses redundant pathways inextricably linked to the physio-pathological requirements of this process.
Collapse
Affiliation(s)
- Robert Bucki
- University of Pennsylvania, Department of Physiology, Institute for Medicine and Engineering, 1010 Vagelos Research Laboratories, 3340 Smith Walk, Philadelphia, PA 19104, USA.
| | | | | | | | | |
Collapse
|
11
|
Melik-Nubarov N, Krylova O. The Control of Membrane Properties by Synthetic Polymers. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s1554-4516(05)02005-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
|
12
|
Martínez MC, Kunzelmann C, Freyssinet JM. [Plasma membrane remodelling and cell stimulation]. Med Sci (Paris) 2004; 20:189-95. [PMID: 14997439 DOI: 10.1051/medsci/2004202189] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
For a long time the plasma membrane has been considered as a simple barrier between the extracellular and intracellular milieu. Now, it is well accepted that it plays a pivotal role in many physiological processes allowing the communication of cells with their environment. On the one hand, the plasma membrane directly participates in intracellular signaling, on the other hand, changes in membrane structure contribute to the transcellular transfer of biological information. This review analyses the most recent features concerning the plasma membrane plasticity, with a special focus on the intracellular signaling pathways involved in the regulation of the loss of membrane phospholipid asymmetry during cell activation. The pathophysiologic consequences of microparticle/microvesicle shedding from membrane blebs are briefly exposed.
Collapse
Affiliation(s)
- Maria Carmen Martínez
- Institut d'Hématologie et d'Immunologie, Faculté de Médecine, Université Louis Pasteur, 4, rue Kirschleger, 67085 Strasbourg Cedex, France
| | | | | |
Collapse
|
13
|
Courageot MP, Lépine S, Hours M, Giraud F, Sulpice JC. Involvement of sodium in early phosphatidylserine exposure and phospholipid scrambling induced by P2X7 purinoceptor activation in thymocytes. J Biol Chem 2004; 279:21815-23. [PMID: 14996828 DOI: 10.1074/jbc.m401426200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Extracellular ATP (ATP(ec)), a possible effector in thymocyte selection, induces thymocyte death via purinoceptor activation. We show that ATP(ec) induced cell death by apoptosis, rather than lysis, and early phosphatidylserine (PS) exposure and phospholipid scrambling in a limited thymocyte population (35-40%). PS externalization resulted from the activation of the cationic channel P2X7 (formerly P2Z) receptor and was triggered in all thymocyte subsets although to different proportions in each one. Phospholipid movement was dependent on ATP(ec)-induced Ca(2+) and/or Na(+) influx. At physiological external Na(+) concentration, without external Ca(2+), PS was exposed in all ATP(ec)-responsive cells. In contrast, without external Na(+), physiological external Ca(2+) concentration promoted a submaximal response. Altogether these data show that Na(+) influx plays a major role in the rapid PS exposure induced by P2X7 receptor activation in thymocytes.
Collapse
Affiliation(s)
- Marie-Pierre Courageot
- Laboratoire des Biomembranes et Messagers Cellulaires, CNRS UMR 8619 and Service de cytométrie, Institut Fédératif de Recherches 46, bât 440, Université Paris XI, 91405 Orsay Cedex, France
| | | | | | | | | |
Collapse
|
14
|
Bucki R, Pastore JJ, Giraud F, Sulpice JC, Janmey PA. Flavonoid inhibition of platelet procoagulant activity and phosphoinositide synthesis. J Thromb Haemost 2003; 1:1820-8. [PMID: 12911599 DOI: 10.1046/j.1538-7836.2003.00294.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dietary flavonoids are known for their antiplatelet activity resulting in cardiovascular protection. Phosphatidylinositol 4,5-bisphosphate (PIP2) was previously reported to play a direct role in phosphatidylserine (PS) exposure, as a Ca2+ target. Thrombin formation and platelet procoagulant activity are dependent on PS exposure. As flavonoids can inhibit phosphoinositide (PPI) kinases, we examined whether changes in PPI metabolism in flavonoid-treated platelets could be involved in their antiplatelet effects. Treatment with the flavonoids quercetin or catechin reduced PS exposure, thrombin formation, PIP2 level and resynthesis after platelet activation with collagen, thrombin or calcium ionophore. Flavonoids also prevented [Ca2+]i increase induced by collagen, but not by the ionophore. The ability of flavonoids to decrease PS exposure induced by ionophore treatment could result from the diminution of PIP2 levels, whereas PS exposure induced by collagen could also be diminished by flavonoids' effects on calcium signaling dependent on PIP2 hydrolysis. These data favor a role for PIP2 in the antiplatelet effects of flavonoids.
Collapse
Affiliation(s)
- R Bucki
- University of Pennsylvania, Institute for Medicine and Engineering, 1010 Vagelos Research Laboratories, Philadelphia, PA 19104, USA.
| | | | | | | | | |
Collapse
|
15
|
Liepiņa I, Czaplewski C, Janmey P, Liwo A. Molecular dynamics study of a gelsolin-derived peptide binding to a lipid bilayer containing phosphatidylinositol 4,5-bisphosphate. Biopolymers 2003; 71:49-70. [PMID: 12712500 DOI: 10.1002/bip.10375] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Gelsolin is an actin-severing protein whose action is initiated by Ca(2+) and inhibited by binding to phosphorylated inositol lipid or phosphoinositides. The regions of gelsolin responsible for phosphoinositide binding are comprised of residues 150-169 (G150-169) and 135-142 (G135-142). The corresponding peptides possess similar binding potency as native gelsolin. Their common feature is the presence of arginine and lysine residues that can bind to negatively charged phosphate groups of phosphoinositides. In this work the binding of the G150-169 peptide to a phosphatidylinositol 4,5-bisphosphate (PIP2) cluster in a lipid membrane model was investigated by molecular dynamics calculations (MD) with the AMBER 4.1 force field, taking into account explicit solvent molecules. Initially the structure of G150-169 was simulated by using the electrostatically driven Monte Carlo (EDMC) and MD methods, and the resulting structure agreed within 3.7 A backbone-atom root mean square deviation with the corresponding experimentally derived structure (PDB code: 1SOL). Using this model for the peptide, a subsequent MD simulation of G150-169 in a periodic box containing a model of dimyristoyl-phosphatidylcholine (DMPC) lipids with a cluster of four PIP2 molecules was carried out. During the simulation G150-169 interacted strongly with PIP2 molecules, initially by formation of salt bridges between its N-terminal basic groups and the phosphate groups of PIP2, followed by formation of hydrophobic bonds between the hydrophobic side chains of the peptide and the fatty acid tail of the lipid. As a result of the formation of hydrophobic bonds, the PIP2 molecules were pulled out from the lipid bilayer. This mode of binding differs from those of other PIP2-binding protein motifs such as PH domains that interact solely with the hydrophilic head group of PIP2. These results suggest that dissociation of gelsolin from actin by PIP2 lipids may involve entering of the PIP2 molecules to the gelsolin-actin interface, thereby weakening the interactions between these proteins.
Collapse
Affiliation(s)
- Inta Liepiņa
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, LV1006, Latvia
| | | | | | | |
Collapse
|
16
|
Abstract
Microparticles are fragments released from the plasma membrane of most stimulated or apoptotic cells. After having long been considered inert cell debris, of possible value for the diagnosis of cell activation or death, there is increasing documented evidence that they can interact with neighboring or remote cells, in which case they acquire a pathophysiologic potential. On the one hand, deleterious microparticles stemming from activated cells can elicit an adverse response from other cells, themselves undergoing membrane vesiculation, leading to pathogenic amplification. On the other hand, since they are thought to reflect a balance between cell stimulation, proliferation, and death, it is conceivable that they are discerned as sensors for the maintenance of homeostasis in multicellular organisms. Because vesiculation is an integral part of the plasma-membrane remodeling process, with the transverse migration of procoagulant phosphatidylserine from the cytoplasmic to the exoplasmic leaflet as the central event, the majority of released microparticles are thought to fulfill a hemostatic function under physiologic conditions. This is particularly true when they originate from platelets, with possible deviation towards thrombosis when produced in excess. Owing to these procoagulant properties, the hemostasis laboratory offers the most appropriate tools for the assessment of the in vivo significance of microparticles.
Collapse
Affiliation(s)
- J-M Freyssinet
- Unité 143 INSERM, Hôpital de Bicêtre, Le Kremlin-Bicêtre, Strasbourg, France.
| |
Collapse
|
17
|
Abstract
Phosphoinositides [PPIs, which collectively refer to phosphorylated derivatives of phosphatidylinositol (PI)] have a pivotal role as precursors to important second messengers and as bona fide signaling and scaffold targeting molecules. This review focuses on recent advances that elucidate how PPIs, particularly PI(4,5)P2 (PIP2), directly regulate the actin cytoskeleton in vivo by modulating the activity and targeting of actin regulatory proteins. The role of PIP2 in stimulating actin polymerization and in establishing cytoskeleton-plasma membrane linkages is emphasized. In addition, the review presents tantalizing evidence that suggests how binding of selected cytoskeletal proteins to membrane PPIs may promote PPI clustering into raft lipid microdomains, alter their accessibility to other proteins, and even distort the bilayer conformation. These actions have profound implications for many other PPI-regulated membrane functions that are beginning to be uncovered, and they suggest how PPIs can mediate crosstalk between the actin cytoskeleton and an expanding spectrum of essential cellular functions.
Collapse
Affiliation(s)
- Helen L Yin
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA.
| | | |
Collapse
|
18
|
Parmryd I, Adler J, Patel R, Magee AI. Imaging metabolism of phosphatidylinositol 4,5-bisphosphate in T-cell GM1-enriched domains containing Ras proteins. Exp Cell Res 2003; 285:27-38. [PMID: 12681284 DOI: 10.1016/s0014-4827(02)00048-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and Ras proteins are involved in signalling pathways originating at the plasma membrane. The localisation and metabolism of PI(4,5)P(2) was studied in Jurkat T cells using fluorescence microscopic imaging with EGFP-tagged and antibody probes. Software was developed to objectively quantitate colocalisation and was used to show that plasma membrane PI(4,5)P(2) was enriched in lipid raft-containing patches of GM1 ganglioside, formed by crosslinking cholera toxin B-subunit (CT-B). The PI(4,5)P(2) metabolites phosphatidylinositol 3,4,5-trisphosphate and diacylglycerol appeared in plasma membrane CT-B-GM1 patches upon induction of signalling. Transferrin receptor and the CD45 tyrosine phosphatase did not colocalise with CT-B-GM1 patches, whereas the tyrosine kinase Lck, the scaffolding protein LAT, and endogenous Ras proteins did partially colocalise with CT-B-GM1 patches as did transfected EGFP-K-Ras(4B) and EGFP-H-Ras. The results demonstrate that T-cell PI(4,5)P(2) metabolism is occurring in GM1-enriched domains and that Ras proteins are present in these domains in vivo.
Collapse
Affiliation(s)
- Ingela Parmryd
- Division of Membrane Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
| | | | | | | |
Collapse
|
19
|
Williamson P, Schlegel RA. Transbilayer phospholipid movement and the clearance of apoptotic cells. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1585:53-63. [PMID: 12531537 DOI: 10.1016/s1388-1981(02)00324-4] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
When lymphocytes (and other cells) die by apoptosis, they orchestrate their own orderly removal by macrophages, and thereby prevent the inflammation that would otherwise attend cell lysis. As part of their demise, apoptotic cells disrupt the normal asymmetric distribution of phospholipids across their plasma membranes, an asymmetry normally maintained by an aminophospholipid translocase. This disruption of asymmetry, mediated by an activity known as the scramblase, generates ligands on the cell surface that trigger phagocytosis of the dying cell before lysis can occur. This crucial alteration of the plasma membrane is not dependent on caspase-mediated proteolysis, but quite unexpectedly, it is required both on the apoptotic target cell and on the phagocyte that engulfs it. At least in the phagocyte, this rearrangement may depend on the activity of an ABC ATPase, termed ABC1 in mammals and ced-7 in C. elegans.
Collapse
|