Publications by authors named "Alexander D Dergunov"

26 Publications

  • Page 1 of 1

Interaction of lipid-free apolipoprotein A-I with cholesterol revealed by molecular modeling.

Biochim Biophys Acta Proteins Proteom 2021 05 3;1869(5):140614. Epub 2021 Feb 3.

Laboratory of Structural Fundamentals of Lipoprotein Metabolism, National Research Centre for Preventive Medicine, Moscow, Russia. Electronic address:

We report the modeling of the interaction of differently self-associated lipid-free apoA-I with cholesterol monomer and tail-to-tail (TT) or face-to-face (FF) cholesterol dimer. Cholesterol dimerization is exploited to reconcile the existing experimental data on cholesterol binding to apoA-I with extremely low critical micelle concentration of cholesterol. Two crystal structures of 1-43 N-truncated apolipoprotein Δ(1-43)A-I tetramer (PDB ID: 1AV1, structure B), 185-243 C-truncated apolipoprotein Δ(185-243)A-I dimer (PDB ID: 3R2P, structure M) were analyzed. Cholesterol monomers bind to multiple binding sites in apoA-I monomer, dimer and tetramer with low, moderate and high energy (-10 to -28 kJ/mol with Schrödinger package), still insufficient to overcome the thermodynamic restriction by cholesterol micellization (-52.8 kJ/mol). The binding sites partially coincide with the putative cholesterol-binding motifs. However, apoA-I monomer and dimer existing in structure B, that contain nonoverlapping and non-interacting pairs of binding sites with high affinity for TT and FF cholesterol dimers, can bind in common 14 cholesterol molecules that correspond to existing values. ApoA-I monomer and dimer in structure M can bind in common 6 cholesterol molecules. The values of respective total energy of cholesterol binding up to 64.5 and 67.0 kJ/mol for both B and M structures exceed the free energy of cholesterol micellization. We hypothesize that cholesterol dimers may simultaneously interact with extracellular monomer and dimer of lipid-free apoA-I, that accumulate at acid pH in atheroma. The thermodynamically allowed apolipoprotein-cholesterol interaction outside the macrophage may represent a new mechanism of cholesterol transport by apoA-I from atheroma, in addition to ABCA1-mediated cholesterol efflux.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbapap.2021.140614DOI Listing
May 2021

HDL cholesterol is associated with PBMC expression of genes involved in HDL metabolism and atherogenesis.

J Med Biochem 2020 Sep;39(3):372-383

National Research Centre for Preventive Medicine, Laboratory of Structural Fundamentals of Lipoprotein Metabolism, Moscow, Russia.

Background: To reveal the association of plasma level of high density lipoprotein cholesterol (HDL-C) level with the transcript level of annotated genes in peripheral blood mononuclear cells (PBMC) and involved in HDL metabolism and atherogenesis at the absence of morphologically evident coronary stenosis.

Methods: Transcript levels of 63 genes in PBMC from 38 male patients 40-60 years without coronary atherosclerosis with widely varied HDL-C level were measured. The protein interactions were analyzed with STRING database.

Results: Among 22 HDL-related genes, the transcript levels for 10 genes ( and ) negatively correlated with HDL-C, while positively for APOA1 gene. Among 41 atherosclerosis-prone genes, the transcript levels for 11 genes ( and ) negatively correlated with HDL-C only, not with LDL-C and plasma TG. The protein products efficiently interacted within each cluster while only two intersection nodes existed between clusters.

Conclusions: Coordinate regulation of cholesterol influx and efflux in PBMC in atherosclerosis-free subjects with widely varied HDL-C level is suggested. The decreased synthesis and transport of cholesteryl ester to the liver may contribute to hyperalphalipoproteinemia. HDL-C increase is associated with the decrease of expression of innate immunity and inflammation genes. Visualization of 22 responder genes is suggested to be useful in the validation of HDL functionality and atherogenesis even at the absence of morphologically evident coronary stenosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2478/jomb-2019-0052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7682810PMC
September 2020

Denaturation of human plasma high-density lipoproteins by urea studied by apolipoprotein A-I dissociation.

Biochim Biophys Acta Mol Cell Biol Lipids 2021 01 19;1866(1):158814. Epub 2020 Sep 19.

Laboratory of Functional Genomics, Institute of Molecular Genetics of the Russian Academy of Sciences, Moscow, Russia.

We studied the mechanism of HDL denaturation with concomitant apoA-I dissociation with HDL preparations from 48 patients with a wide range of plasma HDL-C and evaluated the contribution of lipid-free apoA-I into cholesterol efflux from macrophage, in particular, mediated by cholesterol transporter ABCA1. We prepared HDL by precipitation of apoB-containing lipoproteins by polyethylene glycol and used the chaotropic agent urea to denature HDL preparations. Apo-I dissociation from urea-treated HDL was assessed by the increase of preβ-band fraction with agarose gel electrophoresis followed by electro transfer and immunodetection and by the increase of ABCA1-mediated efflux of fluorescent analogue BODIPY-Cholesterol from RAW 264.7 macrophages. The HDL denaturation is governed by a single transition to fully dissociated apoA-I and the transition cooperativity decreases with increasing HDL-C. The apoA-I release depends on phospholipid concentration of HDL preparation and HDL compositional and structural heterogeneity and is well described by apolipoprotein partition between aqueous and lipid phases. Dissociated apoA-I determines the increase of ABCA1-mediated efflux of BODIPY-Cholesterol from RAW 264.7 macrophages to patient HDL. The increase in apoA-I dissociation is associated with the increase of ABCA1 gene transcript in peripheral blood mononuclear cells from patients. The low level of plasma HDL particles may be compensated by their increased potency for apoA-I release, thus suggesting apoA-I dissociation as a new HDL functional property.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbalip.2020.158814DOI Listing
January 2021

Analysis of Low Molecular Weight Substances and Related Processes Influencing Cellular Cholesterol Efflux.

Pharmaceut Med 2019 12;33(6):465-498

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990, Moscow, Russia.

Cholesterol efflux is the key process protecting the vascular system from the development of atherosclerotic lesions. Various extracellular and intracellular events affect the ability of the cell to efflux excess cholesterol. To explore the possible pathways and processes that promote or inhibit cholesterol efflux, we applied a combined cheminformatic and bioinformatic approach. We performed a comprehensive analysis of published data on the various substances influencing cholesterol efflux and found 153 low molecular weight substances that are included in the Chemical Entities of Biological Interest (ChEBI) database. Pathway enrichment was performed for substances identified within the Reactome database, and 45 substances were selected in 93 significant pathways. The most common pathways included the energy-dependent processes related to active cholesterol transport from the cell, lipoprotein metabolism and lipid transport, and signaling pathways. The activators and inhibitors of cholesterol efflux were non-uniformly distributed among the different pathways: the substances influencing 'biological oxidations' activate cholesterol efflux and the substances influencing 'Signaling by GPCR and PTK6' inhibit efflux. This analysis may be used in the search and design of efflux effectors for therapies targeting structural and functional high-density lipoprotein deficiency.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s40290-019-00308-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7101889PMC
December 2019

Significance of Cholesterol-Binding Motifs in ABCA1, ABCG1, and SR-B1 Structure.

J Membr Biol 2019 02 6;252(1):41-60. Epub 2018 Dec 6.

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, Moscow, Russia, 101990.

ABCA1, ABCG1 transporters, and SR-B1 receptor are the major proteins involved in cholesterol efflux from cells. We superposed in silico the location of putative cholesterol (Chol)-binding motifs CRAC/CARC and CCM in human ABCA1, ABCG1, and SR-B1 with (1) transmembrane protein topology, (2) a profile of structural order of protein, and (3) with an influence of single amino acid substitutions on protein structure and function. ABCA1, ABCG1, and SR-B1 molecules contain 50, 19, and 13 Chol-binding motifs, respectively, that are localized either in membrane helices, or at membrane-water interface, or in water-exposed protein regions. Arginine residues in motifs that coincide with molecular recognition features within intrinsically disordered regions of the transporters are suggested to be important in cholesterol binding; cholesterol-arginine interaction may result in the induction of local order in protein structure. Chol-binding motifs in membrane helices may immobilize cholesterol, while motifs at membrane-water interface may be involved into the efflux of "active" cholesterol. Cholesterol may interfere with ATP binding in both nucleotide-binding domains of ABCA1 structure. For ABCA1 and ABCG1, but not for SR-B1, the presence of mirror code as a CARC-CRAC vector couple in the C-terminal helices controlling protein-cholesterol interactions in the outer and inner membrane leaflets was evidenced. We propose the role of Chol-binding motifs with different immersion in membrane in transport of different cholesterol pools by ABCA1 and ABCG1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00232-018-0056-5DOI Listing
February 2019

Relation of High-Density Lipoprotein Charge Heterogeneity, Cholesterol Efflux Capacity, and the Expression of High-Density Lipoprotein-Related Genes in Mononuclear Cells to the HDL-Cholesterol Level.

Lipids 2018 10 15;53(10):979-991. Epub 2018 Nov 15.

Institute of Molecular Genetics of the Russian Academy of Sciences, 2, Kurchatov Square, 123182, Moscow, Russia.

The heterogeneity and content of human plasma high-density lipoprotein (HDL) related to their atheroprotective properties determined by various molecular and cellular mechanisms still remain to be completely clarified. For 29 atherosclerosis-free male subjects, we studied the relationship of plasma lipid levels and the content of apolipoprotein A-I (apoA-I)-containing HDL with preβ-electrophoretic mobility, the efficiency of BODIPY-cholesterol efflux from RAW 264.7 macrophages to apolipoprotein B (apoB)-deficient plasma, and the expression level of 22 genes related to HDL metabolism in mononuclear cells. A significant decrease in the absolute content of apoA-I in preβ-HDL was found in subjects with hypoalphalipoproteinemia compared with the subjects with hyperalphalipoproteinemia. The preβ-to-α-ratio of the apoA-I content was constant within the HDL-cholesterol (HDL-C) range 0.59 to 2.24 mM. However, this ratio was significantly increased with an increase in the plasma triacylglycerol (TAG) content from 0.59 to 3.42 mM. A correlation of the level of preβ-HDL with the basal and ABCA1-mediated efflux of cholesterol is shown. The transcript levels for six HDL-metabolizing genes (LDLR, LCAT, ABCA1, SCARB1, ZDHHC8, and BMP1) were decreased, while the transcript level of APOA1 gene was increased in mononuclear cells of subjects with hyperalphalipoproteinemia as compared with subjects with hypoalphalipoproteinemia. A reduction of the intracellular cholesterol level and inhibition of the expression of cholesterol transporters by nascent HDL in mononuclear cells from subjects with hyperalphalipoproteinemia are suggested. Hyperalphalipoproteinemia can be a driving force of the decreased flux of cholesteryl ester to the liver and the increased TAG hydrolysis. The atheroprotective effect of preβ-HDL in hypertriglyceridemia is proposed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/lipd.12104DOI Listing
October 2018

Intracellular and Plasma Membrane Events in Cholesterol Transport and Homeostasis.

J Lipids 2018 6;2018:3965054. Epub 2018 Aug 6.

National Research Centre for Preventive Medicine, 10 Petroverigsky Street, 101990 Moscow, Russia.

Cholesterol transport between intracellular compartments proceeds by both energy- and non-energy-dependent processes. Energy-dependent vesicular traffic partly contributes to cholesterol flux between endoplasmic reticulum, plasma membrane, and endocytic vesicles. Membrane contact sites and lipid transfer proteins are involved in nonvesicular lipid traffic. Only "active" cholesterol molecules outside of cholesterol-rich regions and partially exposed in water phase are able to fast transfer. The dissociation of partially exposed cholesterol molecules in water determines the rate of passive aqueous diffusion of cholesterol out of plasma membrane. ATP hydrolysis with concomitant conformational transition is required to cholesterol efflux by ABCA1 and ABCG1 transporters. Besides, scavenger receptor SR-B1 is involved also in cholesterol efflux by facilitated diffusion via hydrophobic tunnel within the molecule. Direct interaction of ABCA1 with apolipoprotein A-I (apoA-I) or apoA-I binding to high capacity binding sites in plasma membrane is important in cholesterol escape to free apoA-I. ABCG1-mediated efflux to fully lipidated apoA-I within high density lipoprotein particle proceeds more likely through the increase of "active" cholesterol level. Putative cholesterol-binding linear motifs within the structure of all three proteins ABCA1, ABCG1, and SR-B1 are suggested to contribute to the binding and transfer of cholesterol molecules from cytoplasmic to outer leaflets of lipid bilayer. Together, plasma membrane events and intracellular cholesterol metabolism and traffic determine the capacity of the cell for cholesterol efflux.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1155/2018/3965054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6106919PMC
August 2018

Cholesterol Efflux and Reverse Cholesterol Transport: Experimental Approaches.

Curr Med Chem 2016 ;23(34):3883-3908

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990 Moscow, Russia.

Background: Cholesterol efflux as a key event in reverse cholesterol transport (RCT) is considered now as both diagnostic tool and a promising target for the treatment of atherosclerosis. Radioactive in vitro cholesterol efflux assay (CEA) is the gold standard for determination of efflux at cellular level. Fluorescent tracers and stable isotope-labeled cholesterol gradually come into use as convenient tools for non-radioactive CEAs.

Results: We review the use of various tracer-based and tracer-free methods for CEAs and for measuring RCT with focus on macrophage-specific cholesterol efflux. CEA utilizing stable isotope-labeled cholesterol is equally reliable with radioactive assay and especially well suited for the determination of both cholesterol efflux and net cholesterol flux. Fluorescent tracers cannot fully mimic cholesterol; however, they are successfully applied in CEA in specific well-defined conditions. Fluorescent CEAs can be high throughput and can provide unique information on efflux from fast cholesterol pools or with single cell resolution. Enzymatic and chromatographic CEAs are net cholesterol flux assays, and they can be applied as efflux assays when used with specific acceptors only. In vivo tests are suited for studies of cholesterol efflux and RCT at the level of the organism. They include injection of tracer-loaded macrophages, a method suitable at present for animal models only, and recently invented modification of whole body tracer kinetics with multicompartment modeling that is capable to determine cholesterol efflux from macrophages.

Conclusion: Despite the decisive role of in vitro assays in our understanding of cholesterol efflux mechanism, the in vivo assays are highly desired to study cholesterol efflux in atherosclerotic lesions and RCT in whole body.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/0929867323666160809093009DOI Listing
February 2017

Significance of Lipid-Free and Lipid-Associated ApoA-I in Cellular Cho-lesterol Efflux.

Curr Protein Pept Sci 2017 ;18(1):92-99

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990 Moscow, Russia.

The structure and stability of apolipoprotein (apo)A-I, the major apolipoprotein of human plasma high-density lipoproteins (HDL), determine the efficiency of the protein in the process of HDL generation and affect HDL properties in binding and exchanging its constituents, thus playing an essential role in reverse cholesterol transport. The equilibrium stability of an apoA-I molecule at the lipid interface (12.7 kcal/mol) predicted by a thermodynamic cycle for apolipoprotein folding-unfolding in water and at interface, largely exceeds apoA-I helix stability in HDL against chemical denaturation (3-5 kcal/mol). An ensemble of structures of lipid-bound apoA-I with different stabilities is assumed to exist. The conformational transitions between apoA-I conformers in water and lipid phases correspond to Lumry-Eyring model OL ⇔ CL ⇒ MW, where OL and CL are open and closed structures of HDLbound apoA-I, and MW is the molten globule in water. The model includes the reversible foldingunfolding transitions of N- and C-domains at HDL interface and apolipoprotein irreversible dissociation. We gathered published data on cholesterol efflux for apoA-I proteins with missense mutations in C-domain and calculated the stability of these mutants as a change of free energy relative to a wild type protein. Significant negative correlation was found between this stability and the efficiency of cAMP-stimulated cholesterol efflux. Thus, besides the known role of C-domain hydrophobicity, structure-destabilizing changes may significantly contribute to ABCA1-mediated cholesterol efflux by free apolipoprotein.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/1389203717666160713150223DOI Listing
February 2017

Cholesteryl ester diffusion, location and self-association constraints determine CETP activity with discoidal HDL: excimer probe study.

Arch Biochem Biophys 2014 Dec 22;564:211-8. Epub 2014 Oct 22.

Research Institute for Physical Chemical Medicine, 119828 Moscow, Russia.

The transfer of cholesteryl ester by recombinant cholesteryl ester transfer protein (CETP) between reconstituted discoidal high-density lipoprotein (rHDL) was studied. Particles contained apolipoprotein A-I, unsaturated POPC or saturated DPPC and cholesteryl ester as cholesteryl 1-pyrenedecanoate (CPD) or cholesteryl laurate (CL) in donor and acceptor rHDL, respectively. Probe dynamics fulfilled the quenching sphere-of-action model. The cholesteryl ester exchange between donor and acceptor particles was characterized by a heterogeneous kinetics; the fast exchanging CPD pool was much higher in a case of POPC compared to DPPC complexes. Probe fraction accessible to CETP increased with temperature, suggesting a more homogeneous probe distribution. Noncompetitive inhibition of probe transfer by acceptor particles was observed. The values of Vmax (0.063μMmin(-1)) and catalytic rate constant kcat (0.42s(-1)) together with a similarity of Km (0.9μM CPD) and KI (2.8μM CL) values for POPC-containing rHDL suggest the efficient cholesteryl ester transfer between nascent HDL with unsaturated phosphatidylcholine in vivo. The phospholipid matrix in discoidal HDL may underlie CETP activity through the self-association, diffusivity and location of cholesteryl ester in the bilayer, the accessibility of cholesteryl ester to cholesterol-binding site in apoA-I structure and the binding of cholesteryl ester, positionable by apoA-I, to CETP.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.abb.2014.09.019DOI Listing
December 2014

Prediction of the influences of missense mutations on cholesteryl ester transfer protein structure.

Arch Biochem Biophys 2014 Dec 6;564:67-73. Epub 2014 Sep 6.

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990 Moscow, Russia. Electronic address:

The structure of human plasma cholesteryl ester transfer protein (CETP) was mapped in silico by a search of the structural effects of missense mutations in the CETP gene. Sixteen deleterious substitutions were chosen among 54 known missense mutations and further ranked by stability change score into six structural and ten functional mutations with large and small stability changes, respectively. A cluster of eight mutations in a central region spanning residues 184-296 with exclusively destabilizing effects was evident. Moreover, the mutations were differently distributed between ordered and highly fluctuating regions. Putative cholesterol-binding regions, mostly unique for CETP in a whole CETP-including protein family, were identified. Three of six structural mutations influence cholesteryl ester and phosphatidylcholine binding by CETP. The local partially disordered structure of some putative cholesterol-binding regions is suggested to be differently influenced by cholesterol binding. This may underlie the impairment of the local ordering effect of cholesterol by the L261R substitution. Also, cholesterol may competitively inhibit cholesteryl ester binding to the CETP molecule, with triglyceride binding being largely undisturbed. This analysis may contribute to the ongoing design and mechanistic studies of new CETP inhibitors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.abb.2014.08.018DOI Listing
December 2014

Mutation mapping of apolipoprotein A-I structure assisted with the putative cholesterol recognition regions.

Biochim Biophys Acta 2013 Oct 24;1834(10):2030-5. Epub 2013 Jun 24.

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990 Moscow, Russia. Electronic address:

Twenty-nine from 52 missense mutations in apoA-I gene are predicted to be deleterious by both SIFT and PolyPhen-2 algorithms. Among those, eight mutations with a prominent change in structure stability as modeled by the SDM tool for both lipid-free (Mei and Atkinson (2011) PDB ID: 3R2P) and HDL-bound (Wu et al. (2009) PDB ID: 3K2S) apoA-I, are referred as structural. The remaining mutations with a preferential location in a long intrinsically disordered region, predicted by the SPINE-D and DNdisorder tools, may influence the functional sites. Among structural mutations, five amyloidosis-only-related mutations, significant in a lipid-free structure, are located in 1-90 region. Six amyloidosis- and hypoalphalipoproteinemia-associated mutations, differently significant in two chains of lipid-bound apoA-I, are distributed among the N-domain. Six cholesterol recognition putative motifs (5 CRAC/1 CCM) in apoA-I structure are suggested to interact with cholesterol. Among those, the K40-W50 partially conserved CCM sequence with a putative recognition feature, predicted by the MoRF tool, may underlie cholesterol binding to lipid-free apoA-I, the binding triggering the disorder-to-order transition within MoRF. Thus, the impairment of helix formation and accelerated protein aggregation may underlie the amyloidogenic effect of W50R substitution. Also, D102H substitution in conserved CRAC2 V97-K106 sequence may be harmful in reverse cholesterol transport. With PDBe Motifs and Sites algorithm, cholesterol is a ligand for L101, F104 and W108 residues in HDL-bound apoA-I. The influence of specific mutation on apoA-I structure and mutated apolipoprotein switch between different pathologies is suggested to depend on the surrounding phase properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbapap.2013.06.011DOI Listing
October 2013

Sequence-specific apolipoprotein A-I effects on lecithin:cholesterol acyltransferase activity.

Mol Cell Biochem 2013 Jun 21;378(1-2):283-90. Epub 2013 Mar 21.

National Research Centre for Preventive Medicine, Moscow, Russia.

Existing kinetic data of cholesteryl ester formation by lecithin:cholesterol acyltransferase in discoidal high-density lipoproteins with 34 mutations of apoA-I that involved all putative helices were grouped by cluster analysis into four noncoincident regions with mutations both without any functional impairment and with profound isolated (V- and K-mutations) or common (VK-mutations) effect on V(max)(app) and K(m)(app). Data were analyzed with a new kinetic model of LCAT activity at interface that exploits the efficiency of LCAT binding to the particle, particle dimensions, and surface concentrations of phosphatidylcholine and cholesterol. V-mutations with major location in the central part and C-domain affected the second-order rate constant of cholesteryl ester formation at the solvolysis of acyl-enzyme intermediate by cholesterol as nucleophile. The central region in apoA-I sequence is suggested to influence the proper positioning of cholesterol molecule toward LCAT active center with major contribution of arginine residue(s). K-mutations with major location in N-domain may affect binding and stability of enzyme-phosphatidylcholine complex. VK-mutations may possess mixed effects; the independent binding measurement may segregate individual steps.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11010-013-1619-5DOI Listing
June 2013

A mechanistic model of lecithin:cholesterol acyltransferase activity exploits discoidal HDL composition and structure.

Arch Biochem Biophys 2012 Apr 21;520(2):81-7. Epub 2012 Feb 21.

National Research Centre for Preventive Medicine, Moscow, Russia.

Lecithin:cholesterol acyltransferase (LCAT) activity towards discoidal HDL with apoA-I was analyzed in conjunction with re-evaluation of conformational stability of apoA-I (Sparks et al., 1993). The reaction at water-lipid interface involves the formation of acyl-enzyme and cholesterol (Chol) as a nucleophilic agent can compete with water at deacylation step. Raw data on apparent kinetic parameters for LCAT activity toward discoidal HDL with fixed (Sparks et al., 1995) or varying (Sparks et al., 1998) palmitoyloleoylphosphatidylcholine (POPC) content fit the kinetic equation derived. At the increase of Chol content in complexes with fixed POPC, interfacial dissociation constant K(d)(∗) for LCAT penetration decreased and interfacial Michaelis constant K(m)(∗) did not change. Also, differences in stability and unfolding cooperativity between two domains in apoA-I molecule increased. At the increase of surface area of the complexes with varying POPC, K(d)(∗) increased, while K(m)(∗) decreased. For both lipidation states the rate constant of acyl-LCAT formation did not vary and any changes in K(m)(∗) are postulated to originate from the change(s) in association/dissociation rate constants of enzyme-substrate complex. Then, at the increase of POPC, the LCAT-POPC complex becomes more stable. ApoA-I seems to "activate" substrate by increasing the exposure of POPC ester bond to active center of LCAT.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.abb.2012.02.006DOI Listing
April 2012

Kinetic analysis of lecithin:cholesterol acyltransferase activity toward discoidal HDL.

Lipids 2011 Nov 24;46(11):1075-9. Epub 2011 Sep 24.

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990, Moscow, Russia.

The kinetics of lecithin:cholesterol acyltransferase(LCAT, EC 2.3.1.43)-catalyzed generation of cholesteryl ester in discoidal high density lipoproteins (HDL) was analyzed in terms of initial binding of LCAT to the disc surface followed by a three-state reaction of the hydrolysis of phosphatidylcholine sn-2 ester bond and acyl-enzyme formation. Cholesterol was considered as alcoholic nucleophile that increases the solvolysis rate of acyl-LCAT. The raw kinetic data of Sparks et al. (J Biol Chem 270:5151-5157, 1995) for four preparations of reconstituted discoidal HDL with a constant level of apolipoprotein A-I and palmitoyloleoylphosphatidylcholine per disc but with cholesterol in a lipid phase continuously increasing from 2.1 to 12.5 mol%, were analyzed in terms of the kinetic equation and a complete set of rate constants was obtained. Data at high cholesterol content do not indicate a saturation phenomenon, thus giving no evidence for a binding of cholesterol to the enzyme. This analysis may be used in the study of LCAT activation by exchangeable apolipoproteins and contribution of the HDL structure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11745-011-3613-6DOI Listing
November 2011

Local/bulk determinants of conformational stability of exchangeable apolipoproteins.

Biochim Biophys Acta 2011 Sep 10;1814(9):1169-77. Epub 2011 May 10.

National Research Centre for Preventive Medicine, Moscow, Russia.

GuHCl-induced denaturation of human plasma apoA-I, apoA-II, apoA-IV, apoE3 and three recombinant apoE isoforms in solution and discoidal complexes with phosphatidylcholine (only plasma proteins) was studied. The protein conformational stability (ΔG(H(2)O)) and a slope of linear dependence of free energy of unfolding on GuHCl concentration (m-value) were estimated with the three equilibrium schemes. The data for all proteins, except apoA-II, fit with the three-state model, thus evidencing two-domain structure. The predicted folding rate of the four apoE in solution correlated with conformational stability. The dependence disappeared at the inclusion of apoA-I and apoA-IV into analysis and the m-values, adjusted for residue number in helices (m(rh)), differed between those for apoE and apoA-I/apoA-IV. However, the m(rh)-values for six proteins correlated positively with the fractional change in accessible surface area at unfolding for Phe, Lys and Asn, while negatively for Arg, Ala and Gly residues. The difference between the adjusted ΔG(rh)(H(2)O) values for apolipoproteins in complexes and in solution decreased at the increase of reduced temperature (T(obs)-T(t))/T(t). The induction of intrinsic disorder by arginine residues may be of primary importance in metabolism and function of exchangeable apolipoproteins, while their stability in nascent discoidal HDL is controlled by the physical state of phosphatidylcholine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbapap.2011.05.001DOI Listing
September 2011

Composition, structure and substrate properties of reconstituted discoidal HDL with apolipoprotein A-I and cholesteryl ester.

Spectrochim Acta A Mol Biomol Spectrosc 2010 Mar 4;75(3):1100-7. Epub 2010 Jan 4.

National Research Centre for Preventive Medicine, Moscow, Russia.

To investigate the influence of lipid unsaturation and neutral lipid on the maturation of high density lipoproteins, the discoidal complexes of apoA-I, phosphatidylcholine and cholesteryl ester (CE) were prepared. Saturated dipalmitoylphosphatidylcholine (DPPC) and unsaturated palmitoyllinoleoylphosphatidylcholine (PLPC), palmitoyloleoylphosphatidylcholine (POPC), and fluorescent probe cholesteryl 1-pyrenedecanoate (CPD) that forms in a diffusion- and concentration-dependent manner short-lived dimer of unexcited and excited molecules (excimer) were used. The apoA-I/DPPC/CPD complexes were heterogeneous by size, composition and probe location. CPD molecules incorporated more efficiently into larger complexes and accumulated in a central part of the discs. The apoA-I/POPC(PLPC)/CPD were also heterogeneous, however, probe molecules distributed preferentially into smaller complexes and accumulated at disc periphery. The kinetics of CPD transfer by recombinant cholesteryl ester transfer protein (CETP) to human plasma LDL is well described by two-exponential decay, the fast component with a shorter transfer time being more populated in PLPC compared to DPPC complexes. The presence of CE molecules in discoidal HDL results in particle heterogeneity. ApoA-I influences the CETP activity modulating the properties of apolipoprotein-phospholipid interface. This may include CE molecules accumulation in the boundary lipid in unsaturated phosphatidylcholine and cluster formation in the bulk bilayer in saturated phosphatidylcholine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.saa.2009.12.064DOI Listing
March 2010

Capillary isotachophoresis study of lipoprotein network sensitive to apolipoprotein E phenotype. 2. ApoE and apoC-III relations in triglyceride clearance.

Mol Cell Biochem 2009 May 13;325(1-2):25-40. Epub 2009 Jan 13.

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990, Moscow, Russia.

The plasma (P), VLDL (V) triglyceride and apoB (B) clearance rates were measured both as 'mass' clearance (k (1)) and 'within the particle' clearance in three patient groups (E33, E23 and E34 phenotypes) at heparin-induced lipolysis in vivo. The lipid (C)- and apoE (E)-specific lipoprotein profiles both before and after heparin were followed by capillary isotachophoresis. The displacement of apoE by exogenous apoC-III at plasma titration in vitro was measured as well. The phenotype-sensitive lipoprotein networks were constructed based on an established set of metabolic rules. The k (1)(V) values did not differ between the three groups, but the lower k (1)(P) values showed significant differences. The k (1)(P) values for E33 and E23 groups were twofold higher compared to E34. A twofold increase in the rate constant for VLDL triglyceride clearance within the particle in E34 group compared to E23 reflected the inhibition of lipolysis by apoE2. For E33 group, (i) the k (1)(V) value was negatively correlated to the size of non-displaceable apoE pool in 2E lipoprotein and to the maximal apoE sorbtion capacity for 2E and 3E lipoproteins; (ii) the k (1)(P) value was not associated to the apoE binding parameters; (iii) the k (1)(V) value was positively correlated to the 4C level and the magnitude of apoC-III removal from VLDL particle; (iv) the k (1)(P) value was positively correlated to the content of apoE, while negatively with apoC-III, in VLDL remnants. For E34 group, the k (1)(V) value was positively correlated to 11C and 1-7C pool levels. Lipolysis- and receptor-mediated TG runways seem to be mostly balanced in E33 group, and VLDL TG clearance may be controlled by HDL through apoE dissociation from VLDLs and apolipoprotein accumulation within 'fast' HDLs at lipolysis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11010-008-0017-xDOI Listing
May 2009

Capillary isotachophoresis study of lipoprotein network sensitive to apolipoprotein E phenotype. 1. ApoE distribution between lipoproteins.

Mol Cell Biochem 2009 May 13;325(1-2):41-51. Epub 2009 Jan 13.

National Research Centre for Preventive Medicine, 10, Petroverigsky street, 101990, Moscow, Russia.

Sixteen patients differing widely in plasma triglyceride content were divided into three groups by their apolipoprotein E (apoE) phenotype-E33 homozygotes, E23, and E34 heterozygotes. The plasma lipid and apoE distribution between individual lipoproteins was followed by capillary isotachophoresis (CITP) of plasma samples pre-stained with lipid fluorescent probe NBD-C6-ceramide and by fluorescein-labeled apoE, respectively. Among 12 peaks visualized by ceramide staining, an individual peak with very low density lipoproteins (VLDL) was identified. The VLDL cholesterol and apoE content determined by CITP directly in whole plasma were significantly related to their content as determined by conventional analysis with isolated VLDL. The ceramide distribution among lipoprotein pools was insensitive to apoE phenotype (49-53 : 7-11 : 39-43% for HDL, VLDL, and IDL/LDL, respectively) while the preferential binding of apoE to VLDL was observed in E34 patients compared to E33 (62 : 19 : 20 vs. 70 : 9 : 22%). In a study of apoE/F displacement from lipoproteins at plasma titration by apoC-III in vitro, apoE was found to bind more tightly to VLDL from E34 compared to E33 patients as evidenced by both the increased non-displaceable apoE pool, the increased VLDL sorbtion capacity for apoE, and the decreased displacement parameter in a "container" model of lipoprotein binding. Two different types of apoE package in a whole lipoprotein profile were observed. ApoE structure in a particular lipoprotein may underlie the phenotype-sensitive apoE distribution and apoC-III interference in hypertriglyceridemia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11010-008-0018-9DOI Listing
May 2009

Statins as effectors of key activities involved in apoE-dependent VLDL metabolism: review and hypothesis.

Vascul Pharmacol 2008 Feb-Mar;48(2-3):70-5. Epub 2007 Dec 15.

National Research Centre for Preventive Medicine, 10, Petroverigsky street, 101990 Moscow, Russia.

Statins influence the major reactions of TG and HDL metabolism controlled, in part, by apoE level and its isoforms on the transcriptional, translational and post-translational levels. The existing unexplained maximal and minimal lipid responses (lowering TG and rising HDL-C) for varepsilon2 and varepsilon4 APOE alleles, respectively, following statin therapy may be completely described by the minimal set of the effects that follow: (i) the lowest and the highest efficiency of the binding of apoE2 and apoE4, respectively, to the LDL receptor; (ii) the increased competition of apoE4-containing VLDL with LDL for the LDL receptor; (iii) the isoform-independent induction by statin of the LDL receptor expression; (iv) the highest inhibition of hepatic lipase and the highest activation of lipoprotein lipase-directed lipolytic pathways for varepsilon2-bearing patients by statins; and (v) the increased clearance of large apoE-containing HDL, specifically with apoE4, at highest statin doses. These effects may be modulated additionally by apoE-controlled TG secretion. The molecular targets demonstrating an isoform-dependent sensitivity to statin therapy are outlined.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vph.2007.12.001DOI Listing
July 2008

The structure of human apolipoprotein E2, E3 and E4 in solution 1. Tertiary and quaternary structure.

Biophys Chem 2006 Jan 2;119(2):158-69. Epub 2005 Sep 2.

Centre du Médicament, Université Henri Poincaré Nancy 1, 30 rue Lionnois, 54000 Nancy, France.

Three recombinant apoE isoforms fused with an amino-terminal extension of 43 amino acids were produced in a heterologous expression system in E. coli. Their state of association in aqueous phase was analyzed by size-exclusion liquid chromatography, sedimentation velocity and sedimentation equilibrium experiments. By liquid chromatography, all three isoforms consisted of three major species with Stokes radii of 4.0, 5.0 and 6.6 nm. Sedimentation velocity confirmed the presence of monomers, dimers and tetramers as major species of each isoform. The association schemes established by sedimentation equilibrium experiments corresponded to monomer-dimer-tetramer-octamer for apoE2, monomer-dimer-tetramer for apoE3 and monomer-dimer-tetramer-octamer for apoE4. Each of the three isoforms exhibits a distinct self-association pattern. The apolipoprotein multi-domain structure was mapped by limited proteolysis with trypsin, chymotrypsin, elastase, subtilisin and Staphylococcus aureus V8 protease. All five enzymes produced stable intermediates during the degradation of the three apoE isoforms, as described for plasma apoE3. The recombinant apoE isoforms, thus, consist of N- and C-terminal domains. The presence of the fusion peptide did not appear to alter the apolipoprotein tertiary organization. However, a 30 kDa amino-terminal fragment appeared during the degradation of the recombinant apoE isoforms resulting from cleavage in the 273-278 region. This region, not accessible in plasma apoE3, results from a different conformation of the C-terminal domain in the recombinant isoforms. A specific pattern for the apoE4 C-terminal domain was observed during the proteolysis. The region 230-260 in apoE4, in contrast to that of apoE3 and apoE2, was not accessible to proteases, probably due to the existence of a longer helix in this region of apoE4 stabilized by an interdomain interaction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bpc.2005.07.010DOI Listing
January 2006

The structure of human apolipoprotein E2, E3 and E4 in solution. 2. Multidomain organization correlates with the stability of apoE structure.

Biophys Chem 2006 Jan 25;119(2):170-85. Epub 2005 Aug 25.

Centre de Génétique Moléculaire UPR 2167, Centre National de la Recherche Scientifique, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France.

The stabilities toward thermal and chemical denaturation of three recombinant isoforms of human apolipoprotein E (r-apoE2, r-apoE3 and r-apoE4), human plasma apoE3, the recombinant amino-terminal (NT) and the carboxyl-terminal (CT) domains of plasma apoE3 at pH 7 were studied using near and far ultraviolet circular dichroism (UV CD), fluorescence and size-exclusion chromatography. By far UV CD, thermal unfolding was irreversible for the intact apoE isoforms and consisted of a single transition. The r-apoE3 was found to be less stable as compared to the plasma protein and the stability of recombinant isoforms was r-apoE4
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bpc.2005.07.009DOI Listing
January 2006

The composition, structural properties and binding of very-low-density and low-density lipoproteins to the LDL receptor in normo- and hypertriglyceridemia: relation to the apolipoprotein E phenotype.

Biol Chem 2005 May;386(5):441-52

National Research Center for Preventive Medicine, Petroverigsky Street 10, 101953 Moscow, Russia.

The composition, apolipoprotein structure and lipoprotein binding to the LDL receptor were studied for very-low-density (VLDL) and low-density lipoprotein (LDL) particles isolated from subjects with apoE phenotype E3/3 (E3), E2/2 or E2/3 (E2+) and E3/4 or E4/4 (E4+) and a wide range of plasma triglyceride (TG) contents. The data combined for all three phenotype groups can be summarized as follows. (i) A decrease in accessibility of VLDL tryptophan residues to I- anions with a decrease in tryptophan surface density, concomitant with an increase in VLDL dimensions, reflects the increased efficiency of protein-protein interactions. (ii) A gradual increase in the quenching constant for LDL apoB fluorescence with an increase in TG/cholesterol (Chol) ratio reflects the 'freezing' effect of Chol molecules on apoB dynamics. (iii) Different mechanisms specific for a particular lipoprotein from E3/3 or E2/3 subjects are responsible for apoE-mediated VLDL binding and apoB-mediated LDL binding to the LDL receptor in a solid-phase binding assay. (iv) The 'spacing' effect of apoC-III molecules on apoE-mediated VLDL binding results in a decrease in the number of binding sites. (v) The maximum of the dependence of the LDL binding affinity constant on relative tryptophan density corresponds to LDL intermediate size. VLDL particles from hypertriglyceridemic E2/3 heterozygotic individuals had remnant-like properties (increased cholesterol, apoE and decreased apoC-III content) while their binding efficiency was unchanged. Based on the affinity constant value and LDL-Chol content, increased competition between VLDL and LDL for the binding to the LDL receptor upon increase in plasma TG is suggested, and LDL from hypertriglyceridemic E3/3 homozygotic individuals is the most efficient competitor.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1515/BC.2005.053DOI Listing
May 2005

Time-dependent lipid response on fluvastatin therapy of patients with hypercholesterolemia sensitive to apoE phenotype.

Vascul Pharmacol 2003 Dec;40(5):237-45

National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101953 Moscow, Russia.

Sixty-seven male patients with hypercholesterolemia, divided into three groups according to apolipoprotein E phenotype (33 with apoE3/ 3 phenotype, E3 group; 23 with 2/2 or 2/3, E2+ group; 11 with 4/4 or 4/3, E4+ group), received daily 20-40 mg of fluvastatin for 12 weeks. The levels of triglyceride (TG), cholesterol (Chol), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured after 0, 4, 8 and 12 weeks on fluvastatin and after 4 weeks washout period. Lipid percentage changes (delta) were not associated with apoE phenotype for any treatment time. Cholesterol decreased by 14% after 12 weeks and HDL-C increased by 14-16% after 12 weeks for three phenotype groups. deltaTG, deltaChol, deltaLDL-C were associated positively, while negatively for deltaHDL-C, with the corresponding basal lipid values for the three groups. The positive deltaTG values occurred at a low basal TG0 level and became negative at TG0 > 1.6-1.9 mM. For E3 and E4+ groups, only a single parameter contributed significantly into a variation of lipid percentage changes. For the E2+ group, TG0 and Chol0 contributed in a reciprocal manner into deltaTG12/0, both positively into deltaChol8/0; Chol0 and HDL-C0 both negatively contributed into deltaHDL-C12/0. HDL-C0 contributed reciprocally into LDL-C variability for E2+ and E4+ groups. Three effects seem to contribute differently into lipid response among patients with different apoE phenotype: the inhibition of hepatic and lipoprotein lipase activities, the competition between TG-rich and low-density lipoproteins for LDL-receptor and the accumulation of intermediate-density lipoproteins in patients bearing E2 isoform.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vph.2003.09.002DOI Listing
December 2003

Homo- and hetero-complexes of exchangeable apolipoproteins in solution and in lipid-bound form.

Spectrochim Acta A Mol Biomol Spectrosc 2003 Mar;59(5):1127-37

National Research Center for Preventive Medicine, 10, Petroverigsky street, 101953 Moscow, Russia.

The self-association state of human plasma apolipoprotein E (apoE) in solution and in complexes with dimyristoylphosphatidylcholine (DMPC) varying in stoichiometry was studied in sub-micromolar concentration range by gel filtration, fluorescence anisotropy, fluorescence quenching and energy transfer measurements with apolipoprotein labeled with lysine-specific fluorescent dyes. Together, these results confirm the equilibrium scheme for various apoE structures in solution: oligomer (in aged preparations) <==> 'closed' tetramer <==> 'open' tetramer ('molten globule' state) <==> native or partially denatured monomer <==> fully denatured monomer. Within DMPC:apoE discoidal complex (125:1) the apolipoprotein association state seems to be intermediate between that in solution and in larger vesicular complex (1000:1); for both complexes, the degree of exposure of fluorescein chromophores into water phase decreased. Hetero-associates of apoA-I and apoC-III-1 in solution and in the complexes with DMPC appear to behave similarly to apoE. When extrapolated to native HDL particles, 'molten globule' state seems to be a structure responsible for the interaction of exchangeable apolipoproteins with phospholipid. For a first time, the location of various apolipoprotein molecules on disc periphery was confirmed. The lysine residue(s) seems to locate closely to reacting residue(s) within apolipoprotein molecules in associates, however, with different package constraints for discoidal versus vesicular complexes with phospholipid.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/s1386-1425(02)00298-6DOI Listing
March 2003

Charge-based heterogeneity of human plasma lipoproteins at hypertriglyceridemia: capillary isotachophoresis study.

Int J Biochem Cell Biol 2003 Apr;35(4):530-43

National Research Centre for Preventive Medicine, 10, Petroverigsky street, 101953, Moscow, Russia.

To reveal the metabolic links between and within pools of pro-atherogenic triglyceride(TG)-rich lipoproteins and anti-atherogenic high density lipoproteins (HDL), the changes in lipoprotein profile at hypertriglyceridemia were analyzed by capillary isotachophoresis. Plasma samples from patients with apoE3/3 phenotype were stained with a fluorescent probe NBD-C6-ceramide and lipoproteins resolved into six H-, one (V+I) and four L-components which belong to HDL, very low and intermediate density (VLDL+IDL) and low density lipoproteins (LDL), respectively. The expected correlation between the relative size of the combined fractions and lipid and apolipoprotein values was obtained confirming the validity of the approach. The new findings were obtained as follows. (1) The fast L-component correlated inversely with HDL-cholesterol (Chol), while intermediate and slow H-components correlated inversely with plasma and LDL-Chol and apoB. (2) The content of intermediate and slow H-components increased within H-pool and decreased relative TG-rich lipoproteins as hypertriglyceridemia rose due to the impairment of triglyceride hydrolysis by lipoprotein lipase within TG-rich particles. (3) A predictive value of the ratios of fast to slow H-components as an indicator of lecithin:cholesterol acyltransferase activity was demonstrated which tended to decrease at hypertriglyceridemia. (4) The L1/L2 ratio may be considered as an indicator of the accumulation of small dense LDL, which is a feature of clinically manifested atherogenic B-pattern. The competition between H(DL) and L(DL) particles for hepatic lipase and significant contribution of apoE to functional deficiency of H(DL) particles at hypertriglyceridemia are suggested.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/s1357-2725(02)00359-xDOI Listing
April 2003
-->