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Muralidharan K, Van Camp MM, Lyon AM. Structure and regulation of phospholipase Cβ and ε at the membrane. Chem Phys Lipids 2021; 235:105050. [PMID: 33422547 DOI: 10.1016/j.chemphyslip.2021.105050] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 10/28/2020] [Accepted: 01/04/2021] [Indexed: 12/28/2022]
Abstract
Phospholipase C (PLC) β and ε enzymes hydrolyze phosphatidylinositol (PI) lipids in response to direct interactions with heterotrimeric G protein subunits and small GTPases, which are activated downstream of G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). PI hydrolysis generates second messengers that increase the intracellular Ca2+ concentration and activate protein kinase C (PKC), thereby regulating numerous physiological processes. PLCβ and PLCε share a highly conserved core required for lipase activity, but use different strategies and structural elements to autoinhibit basal activity, bind membranes, and engage G protein activators. In this review, we discuss recent structural insights into these enzymes and the implications for how they engage membranes alone or in complex with their G protein regulators.
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Affiliation(s)
- Kaushik Muralidharan
- Department of Biological Sciences, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States.
| | - Michelle M Van Camp
- Department of Chemistry, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States.
| | - Angeline M Lyon
- Department of Biological Sciences, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States; Department of Chemistry, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States.
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Hudson BN, Jessup RE, Prahalad KK, Lyon AM. Gα q and the Phospholipase Cβ3 X-Y Linker Regulate Adsorption and Activity on Compressed Lipid Monolayers. Biochemistry 2019; 58:3454-3467. [PMID: 31322863 DOI: 10.1021/acs.biochem.9b00441] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Phospholipase Cβ (PLCβ) enzymes are peripheral membrane proteins required for normal cardiovascular function. PLCβ hydrolyzes phosphatidylinositol 4,5-bisphosphate, producing second messengers that increase intracellular Ca2+ level and activate protein kinase C. Under basal conditions, PLCβ is autoinhibited by its C-terminal domains and by the X-Y linker, which contains a stretch of conserved acidic residues required for interfacial activation. Following stimulation of G protein-coupled receptors, the heterotrimeric G protein subunit Gαq allosterically activates PLCβ and helps orient the activated complex at the membrane for efficient lipid hydrolysis. However, the molecular basis for how the PLCβ X-Y linker, its C-terminal domains, Gαq, and the membrane coordinately regulate activity is not well understood. Using compressed lipid monolayers and atomic force microscopy, we found that a highly conserved acidic region of the X-Y linker is sufficient to regulate adsorption. Regulation of adsorption and activity by the X-Y linker also occurs independently of the C-terminal domains. We next investigated whether Gαq-dependent activation of PLCβ altered interactions with the model membrane. Gαq increased PLCβ adsorption in a manner that was independent of the PLCβ regulatory elements and targeted adsorption to specific regions of the monolayer in the absence of the C-terminal domains. Thus, the mechanism of Gαq-dependent activation likely includes a spatial component.
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Hudson BN, Hyun SH, Thompson DH, Lyon AM. Phospholipase Cβ3 Membrane Adsorption and Activation Are Regulated by Its C-Terminal Domains and Phosphatidylinositol 4,5-Bisphosphate. Biochemistry 2017; 56:5604-5614. [PMID: 28945350 DOI: 10.1021/acs.biochem.7b00547] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Phospholipase Cβ (PLCβ) enzymes hydrolyze phosphatidylinositol 4,5-bisphosphate to produce second messengers that regulate intracellular Ca2+, cell proliferation, and survival. Their activity is dependent upon interfacial activation that occurs upon localization to cell membranes. However, the molecular basis for how these enzymes productively interact with the membrane is poorly understood. Herein, atomic force microscopy demonstrates that the ∼300-residue C-terminal domain promotes adsorption to monolayers and is required for spatial organization of the protein on the monolayer surface. PLCβ variants lacking this C-terminal domain display differences in their distribution on the surface. In addition, a previously identified autoinhibitory helix that binds to the PLCβ catalytic core negatively impacts membrane binding, providing an additional level of regulation for membrane adsorption. Lastly, defects in phosphatidylinositol 4,5-bisphosphate hydrolysis also alter monolayer adsorption, reflecting a role for the active site in this process. Together, these findings support a model in which multiple elements of PLCβ modulate adsorption, distribution, and catalysis at the cell membrane.
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Affiliation(s)
- Brianna N Hudson
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
| | - Seok-Hee Hyun
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
| | - David H Thompson
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
| | - Angeline M Lyon
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
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Andreeva TD, Castano S, Krumova S, Lecomte S, Taneva SG. Effect of Protonation on the Secondary Structure and Orientation of Plant Light-Harvesting Complex II Studied by PM-IRRAS. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:11583-11590. [PMID: 26473578 DOI: 10.1021/acs.langmuir.5b02653] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The major light-harvesting pigment-protein complex of photosystem II, LHCII, has a crucial role in the distribution of the light energy between the two photosystems, the efficient light capturing and protection of the reaction centers and antennae from overexcitation. In this work direct structural information on the effect of LHCII protonation, which mimics the switch from light-harvesting to photoprotective state of the protein, was revealed by polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). PM-IRRAS on LHCII monolayers verified that the native helical structure of the protein is preserved in both partly deprotonated (pH 7.8, LHCII) and protonated (pH 5.2, p-LHCII) states. At low surface pressure, 10 mN/m, the orientation of the α-helices in these two LHCII states is different-tilted (θ ≈ 40°) in LHCII and nearly vertical (θ ≈ 90°) in p-LHCII monolayers; the partly deprotonated complex is more hydrophilic than the protonated one and exhibits stronger intertrimer interactions. At higher surface pressure, 30 mN/m, which is typical for biological membranes, the protonation affects neither the secondary structure nor the orientation of the transmembrane α-helices (tilted ∼45° relative to the membrane surface in both LHCII states) but weakens the intermolecular interactions within and/or between the trimers.
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Affiliation(s)
- Tonya D Andreeva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., bl. 21, 1113 Sofia, Bulgaria
| | - Sabine Castano
- CBMN-Univ. Bordeaux, UMR 5248 , Allée Geoffroy Saint Hilaire, 33600 Pessac, France
| | - Sashka Krumova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., bl. 21, 1113 Sofia, Bulgaria
| | - Sophie Lecomte
- CBMN-Univ. Bordeaux, UMR 5248 , Allée Geoffroy Saint Hilaire, 33600 Pessac, France
| | - Stefka G Taneva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., bl. 21, 1113 Sofia, Bulgaria
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Sonne J, Jensen MØ, Hansen FY, Hemmingsen L, Peters GH. Reparameterization of all-atom dipalmitoylphosphatidylcholine lipid parameters enables simulation of fluid bilayers at zero tension. Biophys J 2007; 92:4157-67. [PMID: 17400696 PMCID: PMC1877764 DOI: 10.1529/biophysj.106.087130] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular dynamics simulations of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers using the CHARMM27 force field in the tensionless isothermal-isobaric (NPT) ensemble give highly ordered, gel-like bilayers with an area per lipid of approximately 48 A(2). To obtain fluid (L(alpha)) phase properties of DPPC bilayers represented by the CHARMM energy function in this ensemble, we reparameterized the atomic partial charges in the lipid headgroup and upper parts of the acyl chains. The new charges were determined from the electron structure using both the Mulliken method and the restricted electrostatic potential fitting method. We tested the derived charges in molecular dynamics simulations of a fully hydrated DPPC bilayer. Only the simulation with the new restricted electrostatic potential charges shows significant improvements compared with simulations using the original CHARMM27 force field resulting in an area per lipid of 60.4 +/- 0.1 A(2). Compared to the 48 A(2), the new value of 60.4 A(2) is in fair agreement with the experimental value of 64 A(2). In addition, the simulated order parameter profile and electron density profile are in satisfactory agreement with experimental data. Thus, the biologically more interesting fluid phase of DPPC bilayers can now be simulated in all-atom simulations in the NPT ensemble by employing our modified CHARMM27 force field.
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Affiliation(s)
- Jacob Sonne
- Department of Chemistry, Technical University of Denmark, Lyngby, Denmark
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Joshi RP, Hu Q, Schoenbach KH, Hjalmarson HP. Improved energy model for membrane electroporation in biological cells subjected to electrical pulses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:041920. [PMID: 12005886 DOI: 10.1103/physreve.65.041920] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2001] [Revised: 02/01/2002] [Indexed: 05/23/2023]
Abstract
A self-consistent model analysis of electroporation in biological cells has been carried out based on an improved energy model. The simple energy model used in the literature is somewhat incorrect and unphysical for a variety of reasons. Our model for the pore formation energy E(r) includes a dependence on pore population and density. It also allows for variable surface tension, incorporates the effects of finite conductivity on the electrostatic correction term, and is dynamic in nature. Self-consistent calculations, based on a coupled scheme involving the Smoluchowski equation and the improved energy model, are presented. It is shown that E(r) becomes self-adjusting with variations in its magnitude and profile, in response to pore population, and inhibits uncontrolled pore growth and expansion. This theory can be augmented to include pore-pore interactions to move beyond the independent pore picture.
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Affiliation(s)
- R P Joshi
- Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529-0246, USA
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Burger KN, Demel RA, Schmid SL, de Kruijff B. Dynamin is membrane-active: lipid insertion is induced by phosphoinositides and phosphatidic acid. Biochemistry 2000; 39:12485-93. [PMID: 11015230 DOI: 10.1021/bi000971r] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamin is a large GTPase involved in the regulation of membrane constriction and fission during receptor-mediated endocytosis. Dynamin contains a pleckstrin-homology domain which is essential for endocytosis and which binds to anionic phospholipids. Here, we show for the first time that dynamin is a membrane-active molecule capable of penetrating into the acyl chain region of membrane lipids. Lipid penetration is strongly stimulated by phosphatidic acid (PA), phosphatidylinositol 4-phosphate, and phosphatidylinositol 4, 5-bisphosphate. Though binding is more efficient in the presence of the phosphoinositides, a much larger part of the dynamin molecule penetrates into PA-containing mixed-lipid systems. Thus, local lipid metabolism will dramatically influence dynamin-lipid interactions, and dynamin-lipid interactions are likely to play an important role in dynamin-dependent endocytosis. Our data suggest that dynamin is directly involved in membrane destabilization, a prerequisite to membrane fission.
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Affiliation(s)
- K N Burger
- Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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Hernandez-Sotomayor SM, Munoz-Sanchez JA, Loyola-Vargas VM. Kinetic analysis of phospholipase C from catharanthus roseus transformed roots using different assays. PLANT PHYSIOLOGY 1999; 120:1075-82. [PMID: 10444091 PMCID: PMC59341 DOI: 10.1104/pp.120.4.1075] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/1999] [Accepted: 05/12/1999] [Indexed: 05/21/2023]
Abstract
The properties of phospholipase C (PLC) partially purified from Catharanthus roseus transformed roots were analyzed using substrate lipids dispersed in phospholipid vesicles, phospholipid-detergent mixed micelles, and phospholipid monolayers spread at an air-water interface. Using [(33)P]phosphatidylinositol 4,5-bisphosphate (PIP(2)) of high specific radioactivity, PLC activity was monitored directly by measuring the loss of radioactivity from monolayers as a result of the release of inositol phosphate and its subsequent dissolution on quenching in the subphase. PLC activity was markedly affected by the surface pressure of the monolayer, with reduced activity at extremes of initial pressure. The optimum surface pressure for PIP(2) hydrolysis was 20 mN/m. Depletion of PLC from solution by incubation with sucrose-loaded PIP(2) vesicles followed by ultracentrifugation demonstrated stable attachment of PLC to the vesicles. A mixed micellar system was established to assay PLC activity using deoxycholate. Kinetic analyses were performed to determine whether PLC activity was dependent on both bulk PIP(2) and PIP(2) surface concentrations in the micelles. The interfacial Michaelis constant was calculated to be 0.0518 mol fraction, and the equilibrium dissociation constant of PLC for the lipid was 45.5 &mgr;M. These findings will add to our understanding of the mechanisms of regulation of plant PLC.
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Affiliation(s)
- SM Hernandez-Sotomayor
- Unidad de Biologia Experimental, Centro de Investigacion Cientifica de Yucatan, Apartado Postal 87 Cordemex 97310, Merida, Yucatan, Mexico
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Ellis MV, James SR, Perisic O, Downes CP, Williams RL, Katan M. Catalytic domain of phosphoinositide-specific phospholipase C (PLC). Mutational analysis of residues within the active site and hydrophobic ridge of plcdelta1. J Biol Chem 1998; 273:11650-9. [PMID: 9565585 DOI: 10.1074/jbc.273.19.11650] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Structural studies of phospholipase C delta1 (PLCdelta1) in complexes with the inositol-lipid headgroup and calcium identified residues within the catalytic domain that could be involved in substrate recognition, calcium binding, and catalysis. In addition, the structure of the PLCdelta1 catalytic domain revealed a cluster of hydrophobic residues at the rim of the active site opening (hydrophobic ridge). To assess a role of each of these residues, we have expressed, purified, and characterized enzymes with the point mutations of putative active site residues (His311, Asn312, Glu341, Asp343, His356, Glu390, Lys438, Lys440, Ser522, Arg549, and Tyr551) and residues from the hydrophobic ridge (Leu320, Phe360, and Trp555). The replacements of most active site residues by alanine resulted in a great reduction (1,000-200,000-fold) of PLC activity analyzed in an inositol lipid/sodium cholate mixed micelle assay. Measurements of the enzyme activity toward phosphatidylinositol, phosphatidylinositol 4-monophosphate, and phosphatidylinositol 4, 5-bis-phosphate (PIP2) identified Ser522, Lys438, and Arg549 as important for preferential hydrolysis of polyphosphoinositides, whereas replacement of Lys440 selectively affected only hydrolysis of PIP2. When PLC activity was analyzed at different calcium concentrations, substitutions of Asn312, Glu390, Glu341, and Asp343 resulted in a shift toward higher calcium concentrations required for PIP2 hydrolysis, suggesting that all these residues contribute toward Ca2+ binding. Mutational analysis also confirmed the importance of His311 ( approximately 20,000-fold reduction) and His356 ( approximately 6,000-fold reduction) for the catalysis. Mutations within the hydrophobic ridge, which had little effect on PIP2 hydrolysis in the mixed-micelles, resulted in an enzyme that was less dependent on the surface pressure when analyzed in a monolayer. This systematic mutational analysis provides further insights into the structural basis for the substrate specificity, requirement for Ca2+ ion, catalysis, and surface pressure/activity dependence, with general implications for eukaryotic phosphoinositide-specific PLCs.
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Affiliation(s)
- M V Ellis
- Cancer Research Campaign Centre for Cell and Molecular Biology, Chester Beatty Laboratories, Fulham Road, London SW3 6JB, United Kingdom
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Hickinson DM, Lucocq JM, Towler MC, Clough S, James J, James SR, Downes CP, Ponnambalam S. Association of a phosphatidylinositol-specific 3-kinase with a human trans-Golgi network resident protein. Curr Biol 1997; 7:987-90. [PMID: 9382841 DOI: 10.1016/s0960-9822(06)00418-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The eukaryotic trans-Golgi network (TGN) is a key site for the formation of transport vesicles destined for different intracellular compartments [1]. A key marker for the mammalian TGN is TGN38/46 [2]. This integral membrane glycoprotein cycles between the TGN and the cell surface and is implicated in recruitment of cytosolic factors and regulation of at least one type of vesicle formation at the mammalian TGN [2] [3]. In this study, we have identified a phosphatidylinositol (PtdIns)-specific 3-kinase activity associated with the human orthologue (TGN46), which is sensitive to lipid kinase inhibitors. Treatment of HeLa cells with low levels of these inhibitors reveals subtle morphological changes in TGN46-positive compartments. Our findings suggest a role for PtdIns 3-kinases and presumably for the product, PtdIns 3-phosphate (PtdIns3P), in the formation of secretory transport vesicles by mechanisms conserved in yeast and mammals.
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Affiliation(s)
- D M Hickinson
- Department of Biochemistry, Medical Sciences Institute, University of Dundee, Dundee DD1 4HN, UK
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11
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Abstract
The biochemical factors that lead to membrane targeting of the Ser/Thr protein phosphatase calcineurin were examined using model phospholipid membranes. The interaction of myristoyl- and non-myristoylcalcineurin with lipid surfaces was investigated as a function of negatively charged phospholipids, diacylglycerol, Ca2+, and calmodulin. The data indicate that calcineurin binding to phospholipid monolayers both is myristoyl-independent and is mediated by anionic phospholipids and/or diacylglycerol. Although the effect of Ca2+ on calcineurin-lipid binding is minor, calmodulin altered the binding of calcineurin to the lipid membrane in a Ca2+-dependent manner. Experiments with a constitutively active form of calcineurin that does not bind calmodulin indicated that the effect required the interaction of calcineurin with calmodulin. Our results suggest that phosphatidylserine, diaclyglycerol, and calmodulin may mediate the lipid binding properties of calcineurin in vivo.
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Affiliation(s)
- M T Kennedy
- Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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12
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James SR, Downes CP. Structural and mechanistic features of phospholipases C: effectors of inositol phospholipid-mediated signal transduction. Cell Signal 1997; 9:329-36. [PMID: 9376212 DOI: 10.1016/s0898-6568(96)00175-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The production of the intracellular second messengers inositol (1,4,5)-trisphosphate (InsP3) and sn 1,2-diacylglycerol (DG) in response to a wide variety of extracellular primary messengers is achieved by an extended family of inositol phospholipid phosphodiesterases termed phospholipases C (PLC, E.C. 3.1.4.11). This family has been the subject of extensive research and it is clear that the different isoenzymes exhibit some common characteristics (e.g., interactions with substrates) and other distinctive features (e.g., modes of regulation). The recent description of the X-ray crystal structure of a mammalian PLC has served to clarify much about the behaviour of the PLCs, emphasising the "modular" structure of these enzymes. The main focus of this review will concern the specific adaptations of PLC molecules which make them efficient lipid-metabolising enzymes. We also describe what is known about how these enzymes interact with their lipid substrates, which will serve as a basis for considering how PLCs may be activated.
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Affiliation(s)
- S R James
- Department of Biochemistry, Medical Sciences Institute, University of Dundee, Scotland, UK.
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Tang X, Downes CP. Purification and characterization of Gbetagamma-responsive phosphoinositide 3-kinases from pig platelet cytosol. J Biol Chem 1997; 272:14193-9. [PMID: 9162050 DOI: 10.1074/jbc.272.22.14193] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A G-protein betagamma subunit (Gbetagamma)-responsive phosphoinositide 3-kinase (PI 3-kinase) was purified approximately 5000-fold from pig platelet cytosol. The enzyme was purified by polyethylene glycol precipitation of the cytosol followed by column chromatography on Q-Sepharose fast flow, gel filtration, heparin-Sepharose, and hydroxyapatite. The major Gbetagamma-responsive PI 3-kinase is distinct from p85 containing PI 3-kinase as the activities can be distinguished chromatographically and immunologically and is related to p110gamma as it cross-reacts with anti-p110gamma-specific antibodies. The p110gamma-related PI 3-kinase cannot be activated by G-protein alphai/o subunits, and it has an apparent native molecular mass of 210 kDa. The p110gamma-related PI 3-kinase phosphorylates phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdIns4P), and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). The apparent Km values for ATP were found to be 25 microM with PtdIns, 44 microM with PtdIns4P, and 37 microM with PtdIns(4,5)P2 as the substrate. Gbetagamma subunits did not alter the Km of the enzyme for ATP; however, Vmax increased 2-fold with PtdIns as substrate, 3.5-fold with PtdIns4P, and 10-fold with PtdIns(4,5)P2. Under basal conditions the apparent Km values for lipid substrates were 64, 10, and 15 microM for PtdIns, PtdIns4P, and PtdIns(4,5)P2, respectively. In the presence of Gbetagamma subunits the dependence of PI 3-kinase activity on the concentrations of lipid substrates became complex with the highest level of stimulation occurring at high substrate concentration, suggesting that the binding of Gbetagamma and lipid substrate (particularly PtdIns(4,5)P2) may be mutually cooperative. Wortmannin and LY294002 inhibit the Gbetagamma-responsive PI 3-kinase activity with IC50 values of 10 nM and 2 microM, respectively. Unlike the p85 containing PI 3-kinase in platelets, the p110gamma-related PI 3-kinase is not associated with a PtdIns(3,4,5)P3 specific 5-phosphatase. The p85-associated PI 3-kinase was not activated by Gbetagamma alone but could be synergistically activated by Gbetagamma and phosphotyrosyl platelet-derived growth factor receptor peptides. This may represent a form of coincidence detection through which the effects of tyrosine kinase and G-protein-linked receptors might be coordinated.
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Affiliation(s)
- X Tang
- Department of Biochemistry, University of Dundee, Dundee DD1 4HN, Scotland
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14
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Alessi DR, James SR, Downes CP, Holmes AB, Gaffney PR, Reese CB, Cohen P. Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha. Curr Biol 1997; 7:261-9. [PMID: 9094314 DOI: 10.1016/s0960-9822(06)00122-9] [Citation(s) in RCA: 2181] [Impact Index Per Article: 80.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Protein kinase B (PKB), also known as c-Akt, is activated rapidly when mammalian cells are stimulated with insulin and growth factors, and much of the current interest in this enzyme stems from the observation that it lies 'downstream' of phosphoinositide 3-kinase on intracellular signalling pathways. We recently showed that insulin or insulin-like growth factor 1 induce the phosphorylation of PKB at two residues, Thr308 and Ser473. The phosphorylation of both residues is required for maximal activation of PKB. The kinases that phosphorylate PKB are, however, unknown. RESULTS We have purified 500 000-fold from rabbit skeletal muscle extracts a protein kinase which phosphorylates PKBalpha at Thr308 and increases its activity over 30-fold. We tested the kinase in the presence of several inositol phospholipids and found that only low micromolar concentrations of the D enantiomers of either phosphatidylinositol 3,4,5-triphosphate (PtdIns(3,4,5)P3) or PtdIns(3,4)P2 were effective in potently activating the kinase, which has been named PtdIns(3,4,5)P3-dependent protein kinase-1 (PDK1). None of the inositol phospholipids tested activated or inhibited PKBalpha or induced its phosphorylation under the conditions used. PDK1 activity was not affected by wortmannin, indicating that it is not likely to be a member of the phosphoinositide 3-kinase family. CONLCUSIONS: PDK1 is likely to be one of the protein kinases that mediate the activation of PKB by insulin and growth factors. PDK1 may, therefore, play a key role in mediating many of the actions of the second messenger(s) PtdIns(3,4, 5)P3 and/or PtdIns(3,4)P2.
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Affiliation(s)
- D R Alessi
- Medical Research Council Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, Dundee, DD1 4HN, Scotland.
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15
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James SR, Paterson A, Harden TK, Demel RA, Downes CP. Dependence of the activity of phospholipase C beta on surface pressure and surface composition in phospholipid monolayers and its implications for their regulation. Biochemistry 1997; 36:848-55. [PMID: 9020783 DOI: 10.1021/bi962108q] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have examined the influence of surface pressure and phospholipid composition on hydrolysis of phosphatidylinositol (4,5)-bisphosphate (PIP2) by phospholipase C beta 1 (PLC beta 1) and PLC beta 2 in mixed composition phospholipid monolayers. Increasing the monolayer surface pressure from 15 to 36 mN/m reduced the rate at which PIP2 was hydrolyzed by PLC beta 1 and PLC beta 2 by 4-6-fold, although PLC beta 1 was more active than PLC beta 2, even at high surface pressure. Reduced enzyme activity was accompanied by an increase in reaction induction times, suggesting that increasing surface pressure reduced the penetration rate of the enzymes into the monolayer. Quantitation of interfacial enzyme concentration using 35S-labeled PLC beta 1 confirmed that less enzyme was associated with the monolayer at higher pressures. The relationship between PLC activity and substrate concentration was examined at a single surface pressure of 30 mN/m. This relationship was not hyperbolic, and increases in the mole percentage (mol %) of PIP2 in the monolayer resulted in an upwardly-curving increase in PLC activity. Thus, PLC beta 1 activity increased 7-fold and PLC beta 2 activity increased 4-fold when the mol % of PIP2 in the monolayer increased from 17.9% to 29%, increasing further thereafter. Paradoxically, increasing the mol % of PIP2 from 0 to 60% was accompanied by a 3-fold decrease in interfacial enzyme concentrations. Taken together, these data show that the catalytic activity of PLC beta involves some element of penetration of lipid interfaces, and suggest that the organization of the substrate facilitates PLC activity, giving credence to the substrate theory of interfacial activation of phospholipases. We present a hypothesis suggesting that PIP2 molecules coalesce into enriched lateral domains which favor PLC beta activity.
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Affiliation(s)
- S R James
- Department of Biochemistry, University of Dundee, Scotland, U.K.
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16
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Scarlata S, Gupta R, Garcia P, Keach H, Shah S, Kasireddy CR, Bittman R, Rebecchi MJ. Inhibition of phospholipase C-delta 1 catalytic activity by sphingomyelin. Biochemistry 1996; 35:14882-8. [PMID: 8942652 DOI: 10.1021/bi961072z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We measured the ability of sphingomyelin (SPM) to inhibit phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] hydrolysis catalyzed by human phospholipase C-delta 1 (PLC-delta 1) in model membranes and detergent phospholipid mixed micelles. SPM strongly inhibited PLC-delta 1 catalytic activity measured in large unilamellar vesicles (LUVs) composed of egg phosphatidylcholine (PC), PI(4,5)P2, and SPM from brain or egg. At 37 or 45 degrees C, the rate of PI(4,5)P2 hydrolysis in PC/SPM/PI(4,5)P2 vesicles (15:80:5 mol:mol) was less than 25% of that observed in PC/PI(4,5)P2 vesicles (95:5). By contrast, catalysis was only weakly inhibited by equivalent concentrations of the SPM analog, 3-deoxy-2-O-stearoyl-SPM, which lacks hydrogen bond-donating groups at the C-3 and C-2 positions of the sphingolipid backbone. Inhibition by SPM was not observed in detergent/phospholipid mixed micelles. The binding affinity of PLC-delta 1 for vesicles containing PC and PI(4,5)P2 was slightly diminished by inclusion of SPM in the lipid mixture, but not enough to account for the decreased rate of catalysis. We could find no evidence of specific binding of the enzyme to SPM, which argues against a simple negative allosteric mechanism. To understand the cause of inhibition, the effects of SPM and 3-deoxy-2-O-stearoyl-SPM on the bulk properties of the substrate bilayers were examined. Increasing the mole fraction of SPM altered the fluorescence emission spectra of two sets of head group probes, 6-lauronyl(N,N-dimethylamino)naphthalene and N-[5-(dimethylamino)naphthalene-1-sulfonyl]-1,2-dihexadecanoyl-sn- glycero-3-phosphoethanolamine, that are sensitive to water content at the membrane/solution interface. Results obtained with both probes suggested a reduction in hydration with increasing SPM content. Vesicles containing 3-deoxy-2-O-stearoyl-SPM produced intermediate changes. Our results are most consistent with a model in which SPM inhibits PLC by increasing interlipid hydrogen bonding and by decreasing membrane hydration; both factors raise the energy barrier for activation of PLC-delta 1 at the membrane/protein microinterface.
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Affiliation(s)
- S Scarlata
- Department of Anesthesiology, State University of New York at Stony Brook 11794, USA.
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17
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Affiliation(s)
- B Roux
- Department de Physique, Université de Montréal, Québec, Canada.
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18
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Waldo GL, Paterson A, Boyer JL, Nicholas RA, Harden TK. Molecular cloning, expression and regulatory activity of G alpha 11- and beta gamma-subunit-stimulated phospholipase C-beta from avian erythrocytes. Biochem J 1996; 316 ( Pt 2):559-68. [PMID: 8687401 PMCID: PMC1217385 DOI: 10.1042/bj3160559] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A turkey erythrocyte phospholipase C (PLC) has been instrumental in delineating the role of G-proteins in receptor-regulated inositol lipid signalling. This isoenzyme is uniquely regulated both by alpha-subunits of the Gq family and by G-protein beta gamma-subunits. A 4819 bp cDNA encoding this PLC has been cloned from a turkey erythrocyte cDNA library. The open reading frame of this cDNA encodes a 1211-amino-acid protein (calculated molecular mass 139050 Da) that contains amino acid sequences of 16 peptides sequenced from the turkey erythrocyte PLC. The predicted sequence of the turkey PLC shows considerable similarity with the sequences of previously cloned members of the PLC-beta family, with the highest identity (71%) shared with PLC-beta 2 and lesser identities observed with PLC-beta 1 (49%), PLC-beta 3 (46%) and PLC-beta 4 (37%). The largest differences in sequence between the turkey PLC-beta and other PLC-beta isoenzymes occur in the C-terminal domain and in the region between the X- and Y-domains. The turkey isoenzyme and PLC-beta 2, which differ in their regulation by G-protein alpha-subunits, are only 44% similar across the approx. 400 amino acid residues of the C-terminal domain that has been implicated in alpha q activation of these proteins. Recombinant turkey PLC-beta was purified to homogeneity following expression from a recombinant baculovirus in Sf9 insect cells. The immunoreactivity and mobility on SDS/PAGE of the recombinant enzyme were the same as observed with native turkey erythrocyte PLC-beta. Moreover, the catalytic activities of the recombinant enzyme were indistinguishable from those of native turkey erythrocyte PLC-beta in assays carried out in the presence of cholate and Ca2+, or in assays of activity after reconstitution with G alpha 11 or G-protein beta gamma-subunits. The turkey PLC-beta was more sensitive to activation by G alpha 11 than was PLC-beta 2, and was more sensitive to activation by beta gamma-subunits than either PLC-beta 2 or PLC-beta 1.
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Affiliation(s)
- G L Waldo
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill 27599-7365, USA
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19
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James SR, Downes CP, Gigg R, Grove SJ, Holmes AB, Alessi DR. Specific binding of the Akt-1 protein kinase to phosphatidylinositol 3,4,5-trisphosphate without subsequent activation. Biochem J 1996; 315 ( Pt 3):709-13. [PMID: 8645147 PMCID: PMC1217264 DOI: 10.1042/bj3150709] [Citation(s) in RCA: 262] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Recent evidence has suggested that activation of phosphoinositide 3-kinase (PI 3-kinase) is required for the activation of Akt-1 by growth factors and insulin. Here we demonstrate by two independent methods that Akt-1 from L6 myotubes binds to PtdIns(3,4,5)P3, PtdIns(3,4)P2 and PtdIns(4,5)P2 when presented against a background of phosphatidylserine (PtdSer) or a 1:1 mixture of PtdSer and phosphatidylcholine (PtdCho). No binding was observed with the lipids PtdIns(3,5)P2, PtdIns4P and PtdIns3P or background lipids. Activated, hyperphosphorylated forms of Akt-1 from insulin-stimulated L6 myotubes bound to PtdIns(3,4,5)P3 in a similar manner as inactive Akt-1. Quantitative analysis using surface plasmon resonance showed that the equilibrium association constant for the binding of Akt-1 to PtdIns(3,4,5)P3 was submicromolar and that PtdIns(3,4)P2 and PtdIns(4,5)P2 bound to Akt-1 with 3- and 6-fold lower affinities respectively. Interaction of Akt-1 with PtdIns(3,4,5)P3 did not activate the protein kinase activity, either before or after incubation with MgATP. A model is presented in which PtdIns(3,4,5)P3 may prime Akt-1 for activation by another protein kinase, perhaps by recruiting it to the plasma membrane.
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Affiliation(s)
- S R James
- Department of Biochemistry, University of Dundee, Scotland
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20
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James SR, Smith S, Paterson A, Harden TK, Downes CP. Time-dependent inhibition of phospholipase C beta-catalysed phosphoinositide hydrolysis: a comparison of different assays. Biochem J 1996; 314 ( Pt 3):917-21. [PMID: 8615789 PMCID: PMC1217144 DOI: 10.1042/bj3140917] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The properties of three different beta-isoforms of phospholipase C (PLC) were analysed using substrate lipids dispersed in phospholipid vesicles, phospholipid-detergent mixed micelles and phospholipid monolayers spread at an air-water interface. Phosphatidylinositol 4,5-bisphosphate hydrolysis went virtually to completion in monolayers, but inositol trisphosphate production was curtailed prematurely in vesicular and micellar assays. Assays were linear for less than 2 min with vesicles; the linear portion could be significantly extended in micelles by increasing the ratio of micelles to enzyme molecules. However, onset of a second lower rate of substrate hydrolysis always occurred when < or = 10% of PtdIns(4,5)P(2) had been utilized. This was not due to enzyme inactivation in the micellar interface, determined by addition of fresh substrate or fresh enzyme after the slow phase of activity had started, nor was it due to overt product inhibition of PLC or apparent entrapment of PLC at the micelle surface. These results are similar to those seen in assays using bacterial PLC and we suggest that the biphasic kinetics may be due to product-dependent changes in the presentation of substrate lipic to PLC in lamellar assays, leading to reduced activity.
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Affiliation(s)
- S R James
- Department of Biochemistry, Medical Sciences Institute, University of Dundee, U.K
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21
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Diakonova M, Payrastre B, van Velzen AG, Hage WJ, van Bergen en Henegouwen PM, Boonstra J, Cremers FF, Humbel BM. Epidermal growth factor induces rapid and transient association of phospholipase C-gamma 1 with EGF-receptor and filamentous actin at membrane ruffles of A431 cells. J Cell Sci 1995; 108 ( Pt 6):2499-509. [PMID: 7673364 DOI: 10.1242/jcs.108.6.2499] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Addition of epidermal growth factor to A431 cells results in dramatic changes in cell morphology. Initially the cells form membrane ruffles accompanied by increased actin polymerization, followed by cell rounding. Activation of the tyrosine kinase of the receptor by binding epidermal growth factor leads also to phosphorylation and activation of phospholipase C-gamma 1, a key enzyme in the phosphoinositide pathway. In this study we have investigated the localization of phospholipase C-gamma 1 during cell activation by epidermal growth factor. It is shown that addition of the growth factor to A431 cells leads to a translocation of phospholipase C-gamma 1 from the cytosol to the membrane fraction. Interestingly, this relocation is exclusively directed to the membrane ruffles. Most of the phospholipase C-gamma 1 associates to the membrane and a small fraction to the underlying skeleton. Immunocytochemical studies demonstrated that phospholipase C-gamma 1 co-localizes with the epidermal growth factor receptor and also filamentous actin at the membrane ruffles. Moreover, using anti-phosphotyrosine antibodies we found that the membrane ruffles are significantly enriched in phosphotyrosyl proteins. Between 5 and 10 minutes after stimulation the membrane ruffles disappear and also the co-localization of phospholipase C-gamma 1 with the epidermal growth factor receptor and filamentous actin. These results support the notion that activation of A431 cells by epidermal growth factor leads to the formation of a signalling complex of its receptor, phospholipase C-gamma 1 and filamentous actin which is primarily localized at membrane ruffles.
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Affiliation(s)
- M Diakonova
- Institute of Cytology, Academy of Science, St Petersburg, Russia
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22
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James SR, Paterson A, Harden TK, Downes CP. Kinetic analysis of phospholipase C beta isoforms using phospholipid-detergent mixed micelles. Evidence for interfacial catalysis involving distinct micelle binding and catalytic steps. J Biol Chem 1995; 270:11872-81. [PMID: 7744837 DOI: 10.1074/jbc.270.20.11872] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PtdIns (4,5)-P2) hydrolysis by three different beta-isoforms of phospholipase C (PLC) was examined to investigate the catalytic action of these extracellular signal-regulated enzymes. Depletion of phospholipase C from solution by incubation with sucrose-loaded vesicles of differing compositions followed by ultracentrifugation demonstrated stable attachment of PLC to the vesicles from which an equilibrium association constant of PLC with PtdIns (4,5)P2 could be determined. A mixed micellar system was established to assay PLC activity using dodecyl maltoside, which behaved as an essentially inert diluent of PtdIns (4,5)P2 with respect to PLC beta activity. Kinetic analyses were performed to test whether PLC beta activity was dependent on both bulk PtdIns (4,5)P2 concentration and surface concentration in the micelles as has been shown for other lipid metabolising enzymes. Each of the PLC beta isoforms behaved similarly in these analyses, which indicated the involvement of at least two binding events. Interfacial Michaelis constants were calculated to be between 0.1-0.2 mol fraction for all three enzymes, and Ks (the equilibrium dissociation constant of PLC for lipid) ranged between 100-200 microM. The apparent multiple interfacial binding events did not appear to result from lipid-induced PLC beta oligomerization implying that PLC beta monomers possess more than one lipid-binding site. Surface dilution of PLC-catalyzed PtdIns (4,5)P2 hydrolysis was assessed in the presence of increasing concentrations of various nonsubstrate phospholipids, which profoundly reduced PLC activity, suggesting that these lipids may inhibit enzyme action. The data indicate that G protein-regulated isoforms of PLC operate with separate lipid binding and catalytic steps and imply that under physiological conditions, PLC beta isoforms operate under first-order conditions. These findings may have implications for the mechanisms of regulation of PLC beta s by G protein subunits.
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Affiliation(s)
- S R James
- Department of Biochemistry, University of Dundee, Tayside, Scotland, United Kingdom
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23
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Simões AP, Reed J, Schnabel P, Camps M, Gierschik P. Characterization of putative polyphosphoinositide binding motifs from phospholipase C beta 2. Biochemistry 1995; 34:5113-9. [PMID: 7711030 DOI: 10.1021/bi00015a023] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Several phosphatidylinositol 4,5-bisphosphate (PtdInsP2)-regulated actin-binding proteins and most phosphoinositide-specific phospholipases C (PI-PLCs) comprise a basic amino acid motif (KxxxKxKK, where x denotes any amino acid), which was previously suggested to represent a PtdInsP2-binding site commonly present in these proteins. We have shown earlier that a peptide corresponding to amino acids 448-464 of human PLC beta 2 (LPSPEDLRGKILIKNKK, peptide P1) markedly and specifically stimulated the activity of this enzyme [Simões et al. (1993) FEBS Lett. 331, 248]. Here, we present a detailed analysis of the effects of various peptides related to peptide P1 aimed at understanding the mechanisms of peptide-mediated PLC beta 2 stimulation. Peptide KILIKNKK (P2), which comprises only the basic amino acid consensus motif, also stimulated PLC beta 2, although higher concentrations were required to observe this stimulatory effect. The effects of P1 and P2 were not additive, indicating that the two peptides affect PLC beta 2 activity via the same mechanism. Peptide LPSPEDLRG (P3), composed of the amino-terminal half of P1, did not affect the activity of PLC beta 2. Peptide KILIKNKKQFSGPTSS (P4), which includes the nine amino acids flanking the carboxy-terminus of the KILIKNKK motif within the sequence of PLC beta 2, stimulated the enzyme but was indistinguishable in potency from P2. Circular dichroism analysis revealed that peptide P1 changes its conformation in the presence of PtdInsP2 but not in the presence of other phospholipids including phosphatidylinositol 4-phosphate. The results suggest that the basic amino acid sequence physically interacts with PtdInsP2.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A P Simões
- German Cancer Research Center, Heidelberg, Germany
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