140 results on '"Remaley AT"'
Search Results
2. PCSK9 vaccines: a promising new strategy for the treatment of hypercholesterolemia?
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Chackerian, Bryce, primary and Remaley, Alan T., additional
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- 2024
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3. Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood
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Ryunosuke Ohkawa, Hann Low, Nigora Mukhamedova, Ying Fu, Shao-Jui Lai, Mai Sasaoka, Ayuko Hara, Azusa Yamazaki, Takahiro Kameda, Yuna Horiuchi, Peter J. Meikle, Gerard Pernes, Graeme Lancaster, Michael Ditiatkovski, Paul Nestel, Boris Vaisman, Denis Sviridov, Andrew Murphy, Alan T. Remaley, Dmitri Sviridov, and Minoru Tozuka
- Subjects
adenosine 5′-triphosphate binding cassette transporter A1 ,apolipoprotein A-I ,cholesterol/metabolism ,cholesterol flux ,erythrocyte ,high density lipoprotein ,Biochemistry ,QD415-436 - Abstract
Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1+/+ and Abca1−/− mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.
- Published
- 2020
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4. Transgelin: a new gene involved in LDL endocytosis identified by a genome-wide CRISPR-Cas9 screen
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Diego Lucero, Ozan Dikilitas, Michael M. Mendelson, Zahra Aligabi, Promotto Islam, Edward B. Neufeld, Aruna T. Bansal, Lita A. Freeman, Boris Vaisman, Jingrong Tang, Christian A. Combs, Yuesheng Li, Szilard Voros, Iftikhar J. Kullo, and Alan T. Remaley
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transgelin ,LDL ,LDL receptor ,endocytosis ,whole-genome CRISPR-Cas9 screen ,cellular LDL uptake ,Biochemistry ,QD415-436 - Abstract
A significant proportion of patients with elevated LDL and a clinical presentation of familial hypercholesterolemia do not carry known genetic mutations associated with hypercholesterolemia, such as defects in the LDL receptor. To identify new genes involved in the cellular uptake of LDL, we developed a novel whole-genome clustered regularly interspaced short palindromic repeat-Cas9 KO screen in HepG2 cells. We identified transgelin (TAGLN), an actin-binding protein, as a potentially new gene involved in LDL endocytosis. In silico validation demonstrated that genetically predicted differences in expression of TAGLN in human populations were significantly associated with elevated plasma lipids (triglycerides, total cholesterol, and LDL-C) in the Global Lipids Genetics Consortium and lipid-related phenotypes in the UK Biobank. In biochemical studies, TAGLN-KO HepG2 cells showed a reduction in cellular LDL uptake, as measured by flow cytometry. In confocal microscopy imaging, TAGLN-KO cells had disrupted actin filaments as well as an accumulation of LDL receptor on their surface because of decreased receptor internalization. Furthermore, TAGLN-KO cells exhibited a reduction in total and free cholesterol content, activation of SREBP2, and a compensatory increase in cholesterol biosynthesis. TAGLN deficiency also disrupted the uptake of VLDL and transferrin, other known cargoes for receptors that depend upon clathrin-mediated endocytosis. Our data suggest that TAGLN is a novel factor involved in the actin-dependent phase of clathrin-mediated endocytosis of LDL. The identification of novel genes involved in the endocytic uptake of LDL may improve the diagnosis of hypercholesterolemia and provide future therapeutic targets for the prevention of cardiovascular disease.
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- 2022
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5. Lecithin:cholesterol acyltransferase: symposium on 50 years of biomedical research from its discovery to latest findings
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Kaare R. Norum, Alan T. Remaley, Helena E. Miettinen, Erik H. Strøm, Bruno E.P. Balbo, Carlos A.T.L. Sampaio, Ingrid Wiig, Jan Albert Kuivenhoven, Laura Calabresi, John J. Tesmer, Mingyue Zhou, Dominic S. Ng, Bjørn Skeie, Sotirios K. Karathanasis, Kelly A. Manthei, and Kjetil Retterstøl
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HDL cholesterol ,lipoprotein ,cardiovascular heart disease ,lipoprotein X ,Biochemistry ,QD415-436 - Abstract
LCAT converts free cholesterol to cholesteryl esters in the process of reverse cholesterol transport. Familial LCAT deficiency (FLD) is a genetic disease that was first described by Kaare R. Norum and Egil Gjone in 1967. This report is a summary from a 2017 symposium where Dr. Norum recounted the history of FLD and leading experts on LCAT shared their results. The Tesmer laboratory shared structural findings on LCAT and the close homolog, lysosomal phospholipase A2. Results from studies of FLD patients in Finland, Brazil, Norway, and Italy were presented, as well as the status of a patient registry. Drs. Kuivenhoven and Calabresi presented data from carriers of genetic mutations suggesting that FLD does not necessarily accelerate atherosclerosis. Dr. Ng shared that LCAT-null mice were protected from diet-induced obesity, insulin resistance, and nonalcoholic fatty liver disease. Dr. Zhou presented multiple innovations for increasing LCAT activity for therapeutic purposes, whereas Dr. Remaley showed results from treatment of an FLD patient with recombinant human LCAT (rhLCAT). Dr. Karathanasis showed that rhLCAT infusion in mice stimulates cholesterol efflux and suggested that it could also enhance cholesterol efflux from macrophages. While the role of LCAT in atherosclerosis remains elusive, the consensus is that a continued study of both the enzyme and disease will lead toward better treatments for patients with heart disease and FLD.
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- 2020
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6. Plasma lipoprotein-X quantification on filipin-stained gels: monitoring recombinant LCAT treatment ex vivo
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Lita A. Freeman, Robert D. Shamburek, Maureen L. Sampson, Edward B. Neufeld, Masaki Sato, Sotirios K. Karathanasis, and Alan T. Remaley
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lecithin:cholesterol acyltransferase ,familial lecithin:cholesterol acyltransferase deficiency ,fish-eye disease ,cholesterol ,phospholipids ,high density lipoprotein ,Biochemistry ,QD415-436 - Abstract
Familial LCAT deficiency (FLD) patients accumulate lipoprotein-X (LP-X), an abnormal nephrotoxic lipoprotein enriched in free cholesterol (FC). The low neutral lipid content of LP-X limits the ability to detect it after separation by lipoprotein electrophoresis and staining with Sudan Black or other neutral lipid stains. A sensitive and accurate method for quantitating LP-X would be useful to examine the relationship between plasma LP-X and renal disease progression in FLD patients and could also serve as a biomarker for monitoring recombinant human LCAT (rhLCAT) therapy. Plasma lipoproteins were separated by agarose gel electrophoresis and cathodal migrating bands corresponding to LP-X were quantified after staining with filipin, which fluoresces with FC, but not with neutral lipids. rhLCAT was incubated with FLD plasma and lipoproteins and LP-X changes were analyzed by agarose gel electrophoresis. Filipin detects synthetic LP-X quantitatively (linearity 20–200 mg/dl FC; coefficient of variation
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- 2019
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7. Coexpression of novel furin-resistant LPL variants with lipase maturation factor 1 enhances LPL secretion and activity
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Ming Jing Wu, Anna Wolska, Benjamin S. Roberts, Ellis M. Pearson, Aspen R. Gutgsell, Alan T. Remaley, and Saskia B. Neher
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lipoprotein lipase ,protein purification ,trafficking ,Biochemistry ,QD415-436 - Abstract
LPL is a secreted enzyme that hydrolyzes triglycerides from circulating lipoproteins. Individuals lacking LPL suffer from severe hypertriglyceridemia, a risk factor for acute pancreatitis. One potential treatment is to administer recombinant LPL as a protein therapeutic. However, use of LPL as a protein therapeutic is limited because it is an unstable enzyme that is difficult to produce in large quantities. Furthermore, these considerations also limit structural and biochemical studies that are needed for large-scale drug discovery efforts. We demonstrate that the yield of purified LPL can be dramatically enhanced by coexpressing its maturation factor, LMF1, and by introducing novel mutations into the LPL sequence to render it resistant to proteolytic cleavage by furin. One of these mutations introduces a motif for addition of an N-linked glycan to the furin-recognition site. Furin-resistant LPL has previously been reported, but is not commonly used. We show that our modifications do not adversely alter LPL's enzymatic activity, stability, or in vivo function. Together, these data show that furin-resistant LPL is a useful reagent for both biochemical and biomedical studies.
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- 2018
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8. Perioperative high density lipoproteins, oxidative stress, and kidney injury after cardiac surgery
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Loren E. Smith, Derek K. Smith, Patricia G. Yancey, Valentina Kon, Alan T. Remaley, Frederic T. Billings, IV, and MacRae F. Linton
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cardiovascular disease ,cholesterol ,eicosanoids ,HDL function ,paraoxonase ,renal disease ,Biochemistry ,QD415-436 - Abstract
Oxidative stress promotes acute kidney injury (AKI). Higher HDL cholesterol concentrations are associated with less AKI. To test the hypothesis that HDL antioxidant activity is associated with AKI after cardiac surgery, we quantified HDL particle (HDL-P) size and number, paraoxonase-1 (PON-1) activity, and isofuran concentrations in 75 patients who developed AKI and 75 matched control patients. Higher preoperative HDL-P was associated with less AKI (OR: 0.80; 95% CI, 0.71–0.91; P = 0.001), higher PON-1 activity ( P < 0.001), and lower plasma concentrations of isofurans immediately after surgery (P = 0.02). Similarly, higher preoperative small HDL-P was associated with less AKI, higher PON-1 activity, and lower isofuran concentrations. Higher intraoperative particle losses were associated with less AKI (OR: 0.79; 95% CI 0.67–0.93; P = 0.005), and with decreased postoperative isofuran concentrations (P = 0.04) . Additionally, higher preoperative small HDL-P and increased intraoperative small particle loss were associated with improved long-term renal function (P = 0.003, 0.01, respectively). In conclusion, a higher preoperative concentration of HDL-P, particularly small particles, is associated with lower oxidative damage and less AKI. Perioperative changes in HDL-P concentrations are also associated with AKI. Small HDL-P may represent a novel modifiable risk factor for AKI.
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- 2021
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9. Pregnancy is accompanied by larger high density lipoprotein particles and compositionally distinct subspecies
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John T. Melchior, Debi K. Swertfeger, Jamie Morris, Scott E. Street, Carri R. Warshak, Jeffrey A. Welge, Alan T. Remaley, Janet M. Catov, W. Sean Davidson, and Laura A. Woollett
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dyslipidemia ,nuclear magnetic resonance spectroscopy ,lipoprotein ,proteomics ,mass spectrometry ,pregnancy ,Biochemistry ,QD415-436 - Abstract
Pregnancy is accompanied by significant physiological changes, which can impact the health and development of the fetus and mother. Pregnancy-induced changes in plasma lipoproteins are well documented, with modest to no impact observed on the generic measure of high density lipoprotein (HDL) cholesterol. However, the impact of pregnancy on the concentration and composition of HDL subspecies has not been examined in depth. In this prospective study, we collected plasma from 24 nonpregnant and 19 pregnant women in their second trimester. Using nuclear magnetic resonance (NMR), we quantified 11 different lipoprotein subspecies from plasma by size, including three in the HDL class. We observed an increase in the number of larger HDL particles in pregnant women, which were confirmed by tracking phospholipids across lipoproteins using high-resolution gel-filtration chromatography. Using liquid chromatography-mass spectrometry (LC-MS), we identified 87 lipid-associated proteins across size-speciated fractions. We report drastic shifts in multiple protein clusters across different HDL size fractions in pregnant females compared with nonpregnant controls that have major implications on HDL function. These findings significantly elevate our understanding of how changes in lipoprotein metabolism during pregnancy could impact the health of both the fetus and the mother.
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- 2021
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10. A thumbwheel mechanism for APOA1 activation of LCAT activity in HDL[S]
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Allison L. Cooke, Jamie Morris, John T. Melchior, Scott E. Street, W.Gray Jerome, Rong Huang, Andrew B. Herr, Loren E. Smith, Jere P. Segrest, Alan T. Remaley, Amy S. Shah, Thomas B. Thompson, and W.Sean Davidson
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apolipoproteins ,cholesterol metabolism ,lecithin:cholesterol acyltransferase ,high density lipoprotein metabolism ,high density lipoprotein ,proteomics ,Biochemistry ,QD415-436 - Abstract
APOA1 is the most abundant protein in HDL. It modulates interactions that affect HDL';s cardioprotective functions, in part via its activation of the enzyme, LCAT. On nascent discoidal HDL, APOA1 comprises 10 α-helical repeats arranged in an anti-parallel stacked-ring structure that encapsulates a lipid bilayer. Previous chemical cross-linking studies suggested that these APOA1 rings can adopt at least two different orientations, or registries, with respect to each other; however, the functional impact of these structural changes is unknown. Here, we placed cysteine residues at locations predicted to form disulfide bonds in each orientation and then measured APOA1';s ability to adopt the two registries during HDL particle formation. We found that most APOA1 oriented with the fifth helix of one molecule across from fifth helix of the other (5/5 helical registry), but a fraction adopted a 5/2 registry. Engineered HDLs that were locked in 5/5 or 5/2 registries by disulfide bonds equally promoted cholesterol efflux from macrophages, indicating functional particles. However, unlike the 5/5 registry or the WT, the 5/2 registry impaired LCAT cholesteryl esterification activity (P< 0.001), despite LCAT binding equally to all particles. Chemical cross-linking studies suggest that full LCAT activity requires a hybrid epitope composed of helices 5–7 on one APOA1 molecule and helices 3–4 on the other. Thus, APOA1 may use a reciprocating thumbwheel-like mechanism to activate HDL-remodeling proteins.
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- 2018
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11. High density lipoproteins and type 2 inflammatory biomarkers are negatively correlated in atopic asthmatics
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Amisha V. Barochia, Elizabeth M. Gordon, Maryann Kaler, Rosemarie A. Cuento, Patricia Theard, Debbie M. Figueroa, Xianglan Yao, Nargues A. Weir, Maureen L. Sampson, Mario Stylianou, David F. Choy, Cecile T.J. Holweg, Alan T. Remaley, and Stewart J. Levine
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apolipoproteins ,immunology ,clinical studies ,lung ,inflammation ,eosinophils ,Biochemistry ,QD415-436 - Abstract
Blood eosinophil counts and serum periostin levels are biomarkers of type 2 inflammation. Although serum levels of HDL and apoA-I have been associated with less severe airflow obstruction in asthma, it is not known whether serum lipids or lipoprotein particles are correlated with type 2 inflammation in asthmatics. Here, we assessed whether serum lipids and lipoproteins correlated with blood eosinophil counts or serum periostin levels in 165 atopic asthmatics and 163 nonasthmatic subjects with and without atopy. Serum lipids and lipoproteins were quantified using standard laboratory assays and NMR spectroscopy. Absolute blood eosinophils were quantified by complete blood counts. Periostin levels were measured using the Elecsys® periostin assay. In atopic asthmatics, blood eosinophils negatively correlated with serum HDL cholesterol and total HDL particles measured by NMR spectroscopy (HDLNMR). Serum periostin levels negatively correlated with total HDLNMR. In contrast, blood eosinophil counts positively correlated with serum triglyceride levels. This study demonstrates for the first time that HDL particles were negatively correlated, whereas serum triglycerides were positively correlated, with blood eosinophils in atopic asthmatics. This supports the concept that serum levels of HDL and triglycerides may be linked to systemic type 2 inflammation in atopic asthma.
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- 2017
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12. ABCA1 contributes to macrophage deposition of extracellular cholesterol
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Xueting Jin, Sebastian R. Freeman, Boris Vaisman, Ying Liu, Janet Chang, Neta Varsano, Lia Addadi, Alan Remaley, and Howard S. Kruth
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atherosclerosis ,apolipoprotein A-I ,high density lipoprotein ,probucol ,TO901317 ,ATP binding cassette transporter A1 ,Biochemistry ,QD415-436 - Abstract
We previously reported that cholesterol-enriched macrophages excrete cholesterol into the extracellular matrix. A monoclonal antibody that detects cholesterol microdomains labels the deposited extracellular particles. Macrophage deposition of extracellular cholesterol depends, in part, on ABCG1, and this cholesterol can be mobilized by HDL components of the reverse cholesterol transport process. The objective of the current study was to determine whether ABCA1 also contributes to macrophage deposition of extracellular cholesterol. ABCA1 functioned in extracellular cholesterol deposition. The liver X receptor agonist, TO901317 (TO9), an ABCA1-inducing factor, restored cholesterol deposition that was absent in cholesterol-enriched ABCG1−/− mouse macrophages. In addition, the ABCA1 inhibitor, probucol, blocked the increment in cholesterol deposited by TO9-treated wild-type macrophages, and completely inhibited deposition from TO9-treated ABCG1−/− macrophages. Lastly, ABCA1−/− macrophages deposited much less extracellular cholesterol than wild-type macrophages. These findings demonstrate a novel function of ABCA1 in contributing to macrophage export of cholesterol into the extracellular matrix.
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- 2015
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13. The effect of phospholipid composition of reconstituted HDL on its cholesterol efflux and anti-inflammatory properties[S]
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Anna Schwendeman, Denis O. Sviridov, Wenmin Yuan, Yanhong Guo, Emily E. Morin, Yue Yuan, John Stonik, Lita Freeman, Alice Ossoli, Seth Thacker, Salena Killion, Milton Pryor, Y.Eugene Chen, Scott Turner, and Alan T. Remaley
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high density lipoprotein ,apolipoprotein A-I ,sphingomyelin ,peptides ,inflammation ,atherosclerosis ,Biochemistry ,QD415-436 - Abstract
The goal of this study was to understand how the reconstituted HDL (rHDL) phospholipid (PL) composition affects its cholesterol efflux and anti-inflammatory properties. An ApoA-I mimetic peptide, 5A, was combined with either SM or POPC. Both lipid formulations exhibited similar in vitro cholesterol efflux by ABCA1, but 5A-SM exhibited higher ABCG1- and SR-BI-mediated efflux relative to 5A-POPC (P < 0.05). Injection of both rHDLs in rats resulted in mobilization of plasma cholesterol, although the relative potency was 3-fold higher for the same doses of 5A-SM than for 5A-POPC. Formation of preβ HDL was observed following incubation of rHDLs with both human and rat plasma in vitro, with 5A-SM inducing a higher extent of preβ formation relative to 5A-POPC. Both rHDLs exhibited anti-inflammatory properties, but 5A-SM showed higher inhibition of TNF-α, IL-6, and IL-1β release than did 5A-POPC (P < 0.05). Both 5A-SM and 5A-POPC showed reduction in total plaque area in ApoE−/− mice, but only 5A-SM showed a statistically significant reduction over placebo control and baseline (P < 0.01). The type of PL used to reconstitute peptide has significant influence on rHDL's anti-inflammatory and anti-atherosclerosis properties.
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- 2015
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14. Increased plasma cholesterol esterification by LCAT reduces diet-induced atherosclerosis in SR-BI knockout mice[S]
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Seth G. Thacker, Xavier Rousset, Safiya Esmail, Abdalrahman Zarzour, Xueting Jin, Heidi L. Collins, Maureen Sampson, John Stonik, Stephen Demosky, Daniela A. Malide, Lita Freeman, Boris L. Vaisman, Howard S. Kruth, Steven J. Adelman, and Alan T. Remaley
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lecithin:cholesterol acyltransferase ,scavenger receptor class B member I ,knockout ,Biochemistry ,QD415-436 - Abstract
LCAT, a plasma enzyme that esterifies cholesterol, has been proposed to play an antiatherogenic role, but animal and epidemiologic studies have yielded conflicting results. To gain insight into LCAT and the role of free cholesterol (FC) in atherosclerosis, we examined the effect of LCAT over- and underexpression in diet-induced atherosclerosis in scavenger receptor class B member I-deficient [Scarab(−/−)] mice, which have a secondary defect in cholesterol esterification. Scarab(−/−)×LCAT-null [Lcat(−/−)] mice had a decrease in HDL-cholesterol and a high plasma ratio of FC/total cholesterol (TC) (0.88 ± 0.033) and a marked increase in VLDL-cholesterol (VLDL-C) on a high-fat diet. Scarab(−/−)×LCAT-transgenic (Tg) mice had lower levels of VLDL-C and a normal plasma FC/TC ratio (0.28 ± 0.005). Plasma from Scarab(−/−)×LCAT-Tg mice also showed an increase in cholesterol esterification during in vitro cholesterol efflux, but increased esterification did not appear to affect the overall rate of cholesterol efflux or hepatic uptake of cholesterol. Scarab(−/−)×LCAT-Tg mice also displayed a 51% decrease in aortic sinus atherosclerosis compared with Scarab(−/−) mice (P < 0.05). In summary, we demonstrate that increased cholesterol esterification by LCAT is atheroprotective, most likely through its ability to increase HDL levels and decrease pro-atherogenic apoB-containing lipoprotein particles.
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- 2015
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15. LCAT deficiency does not impair amyloid metabolism in APP/PS1 mice[S]
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Sophie Stukas, Lita Freeman, Michael Lee, Anna Wilkinson, Alice Ossoli, Boris Vaisman, Stephen Demosky, Jeniffer Chan, Veronica Hirsch-Reinshagen, Alan T. Remaley, and Cheryl L. Wellington
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lecithin:cholesterol acyltransferase ,high density lipoprotein metabolism ,apolipoproteins ,Alzheimer's disease ,Biochemistry ,QD415-436 - Abstract
A key step in plasma HDL maturation from discoidal to spherical particles is the esterification of cholesterol to cholesteryl ester, which is catalyzed by LCAT. HDL-like lipoproteins in cerebrospinal fluid (CSF) are also spherical, whereas nascent lipoprotein particles secreted from astrocytes are discoidal, suggesting that LCAT may play a similar role in the CNS. In plasma, apoA-I is the main LCAT activator, while in the CNS, it is believed to be apoE. apoE is directly involved in the pathological progression of Alzheimer's disease, including facilitating β-amyloid (Aβ) clearance from the brain, a function that requires its lipidation by ABCA1. However, whether apoE particle maturation by LCAT is also required for Aβ clearance is unknown. Here we characterized the impact of LCAT deficiency on CNS lipoprotein metabolism and amyloid pathology. Deletion of LCAT from APP/PS1 mice resulted in a pronounced decrease of apoA-I in plasma that was paralleled by decreased apoA-I levels in CSF and brain tissue, whereas apoE levels were unaffected. Furthermore, LCAT deficiency did not increase Aβ or amyloid in APP/PS1 LCAT−/− mice. Finally, LCAT expression and plasma activity were unaffected by age or the onset of Alzheimer's-like pathology in APP/PS1 mice. Taken together, these results suggest that apoE-containing discoidal HDLs do not require LCAT-dependent maturation to mediate efficient Aβ clearance.
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- 2014
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16. HDL and cholesterol: life after the divorce?
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Kasey C. Vickers and Alan T. Remaley
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microRNA ,extracellular miRNA ,small RNA carrier ,Biochemistry ,QD415-436 - Abstract
For decades, HDL and HDL-cholesterol (HDL-C) levels were viewed as synonymous, and modulation of HDL-C levels by drug therapy held great promise for the prevention and treatment of cardiovascular disease. Nevertheless, recent failures of drugs that raise HDL-C to reduce cardiovascular risk and the now greater understanding of the complexity of HDL composition and biology have prompted researchers in the field to redefine HDL. As such, the focus of HDL has now started to shift away from a cholesterol-centric view toward HDL particle number, subclasses, and other alternative metrics of HDL. Many of the recently discovered functions of HDL are, in fact, not strictly conferred by its ability to promote cholesterol flux but by the other molecules it transports, including a diverse set of proteins, small RNAs, hormones, carotenoids, vitamins, and bioactive lipids. Based on HDL's ability to interact with almost all cells and transport and deliver fat-soluble cargo, HDL has the remarkable capacity to affect a wide variety of endocrine-like systems. In this review, we characterize HDL's unique cargo and address the functional relevance and consequences of HDL transport and delivery of noncholesterol molecules to recipient cells and tissues.
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- 2014
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17. Tomatoes, lysophosphatidic acid, and the small intestine: new pieces in the puzzle of apolipoprotein mimetic peptides?1
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A.T. Remaley
- Subjects
Biochemistry ,QD415-436 - Published
- 2013
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18. Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood
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Graeme I. Lancaster, Denis Sviridov, Nigora Mukhamedova, Takahiro Kameda, Gerard Pernes, Peter J. Meikle, Ryunosuke Ohkawa, Boris L. Vaisman, Andrew J. Murphy, Ayuko Hara, Ying Fu, Michael Ditiatkovski, Shao-Jui Lai, Paul J. Nestel, Alan T. Remaley, Hann Low, Dmitri Sviridov, Minoru Tozuka, Yuna Horiuchi, Mai Sasaoka, and Azusa Yamazaki
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0301 basic medicine ,cholesterol flux ,medicine.medical_specialty ,Erythrocytes ,Lipoproteins ,apolipoprotein A-I ,cholesterol/metabolism ,QD415-436 ,030204 cardiovascular system & hematology ,Biochemistry ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Endocrinology ,High-density lipoprotein ,Internal medicine ,hemic and lymphatic diseases ,Translocator protein ,medicine ,Humans ,Research Articles ,Lipoprotein lipase ,biology ,Cholesterol ,Reverse cholesterol transport ,Computational Biology ,Biological Transport ,hemic and immune systems ,Cell Biology ,adenosine 5′-triphosphate binding cassette transporter A1 ,030104 developmental biology ,chemistry ,high density lipoprotein ,Low-density lipoprotein ,ABCA1 ,LDL receptor ,biology.protein ,lipids (amino acids, peptides, and proteins) ,erythrocyte ,circulatory and respiratory physiology - Abstract
Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1(+/+) and Abca1(−/−) mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.
- Published
- 2020
19. Scavenger receptor-BI is a receptor for lipoprotein(a)
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Xiao-Ping Yang, Marcelo J. Amar, Boris Vaisman, Alexander V. Bocharov, Tatyana G. Vishnyakova, Lita A. Freeman, Roger J. Kurlander, Amy P. Patterson, Lewis C. Becker, and Alan T. Remaley
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lipoprotein receptors ,atherosclerosis ,apolipoprotein(a) ,oxidized lipids ,selective uptake ,Biochemistry ,QD415-436 - Abstract
Scavenger receptor class B type I (SR-BI) is a multi-ligand receptor that binds a variety of lipoproteins, including high density lipoprotein (HDL) and low density lipoprotein (LDL), but lipoprotein(a) [Lp(a)] has not been investigated as a possible ligand. Stable cell lines (HEK293 and HeLa) expressing human SR-BI were incubated with protein- or lipid-labeled Lp(a) to investigate SR-BI-dependent Lp(a) cell association. SR-BI expression enhanced the association of both 125I- and Alexa Fluor-labeled protein from Lp(a). By confocal microscopy, SR-BI was also found to promote the internalization of fluorescent lipids (BODIPY-cholesteryl ester (CE)- and DiI-labeled) from Lp(a), and by immunocytochemistry the cellular internalization of apolipoprotein(a) and apolipoprotein B. When dual-labeled (3H-cholesteryl ether,125I-protein) Lp(a) was added to cells expressing SR-BI, there was a greater relative increase in lipid uptake over protein, indicating that SR-BI mediates selective lipid uptake from Lp(a). Compared with C57BL/6 control mice, transgenic mice overexpressing human SR-BI in liver were found to have increased plasma clearance of 3H-CE-Lp(a), whereas mouse scavenger receptor class B type I knockout (Sr-b1-KO) mice had decreased plasma clearance (fractional catabolic rate: 0.63 ± 0.08/day, 1.64 ± 0.62/day, and 4.64 ± 0.40/day for Sr-b1-KO, C57BL/6, and human scavenger receptor class B type I transgenic mice, respectively). We conclude that Lp(a) is a novel ligand for SR-BI and that SR-BI mediates selective uptake of Lp(a)-associated lipids.
- Published
- 2013
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20. Complexity of microRNA function and the role of isomiRs in lipid homeostasis
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Kasey C. Vickers, Praveen Sethupathy, Jeanette Baran-Gale, and Alan T. Remaley
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microRNA isoform ,lipid metabolism ,nontemplated additions ,Biochemistry ,QD415-436 - Abstract
MicroRNAs (miRNAs) are key posttranscriptional regulators of biological pathways that govern lipid metabolic phenotypes. Recent advances in high-throughput small RNA sequencing technology have revealed the complex and dynamic repertoire of miRNAs. Specifically, it has been demonstrated that a single genomic locus can give rise to multiple, functionally distinct miRNA isoforms (isomiR). There are several mechanisms by which isomiRs can be generated, including processing heterogeneity and posttranscriptional modifications, such as RNA editing, exonuclease-mediated nucleotide trimming, and/or nontemplated nucleotide addition (NTA). NTAs are dominant at the 3′-end of a miRNA, are most commonly uridylation or adenlyation events, and are catalyzed by one or more of several nucleotidyl transferase enzymes. 3′ NTAs can affect miRNA stability and/or activity and are physiologically regulated, whereas modifications to the 5′-ends of miRNAs likely alter miRNA targeting activity. Recent evidence also suggests that the biogenesis of specific miRNAs, or small RNAs that act as miRNAs, can occur through unconventional mechanisms that circumvent key canonical miRNA processing steps. The unveiling of miRNA diversity has significantly added to our view of the complexity of miRNA function. In this review we present the current understanding of the biological relevance of isomiRs and their potential role in regulating lipid metabolism.
- Published
- 2013
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21. Transgelin: a new gene involved in LDL endocytosis identified by a genome-wide CRISPR-Cas9 screen
- Author
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Lucero, Diego, primary, Dikilitas, Ozan, additional, Mendelson, Michael M., additional, Aligabi, Zahra, additional, Islam, Promotto, additional, Neufeld, Edward B., additional, Bansal, Aruna T., additional, Freeman, Lita A., additional, Vaisman, Boris, additional, Tang, Jingrong, additional, Combs, Christian A., additional, Li, Yuesheng, additional, Voros, Szilard, additional, Kullo, Iftikhar J., additional, and Remaley, Alan T., additional
- Published
- 2022
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22. Endothelial expression of human ABCA1 in mice increases plasma HDL cholesterol and reduces diet-induced atherosclerosis[S]
- Author
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Boris L. Vaisman, Stephen J. Demosky, John A. Stonik, Mona Ghias, Cathy L. Knapper, Maureen L. Sampson, Cuilian Dai, Stewart J. Levine, and Alan T. Remaley
- Subjects
endothelial cells ,cholesterol efflux ,reverse cholesterol transport ,high density lipoprotein ,ATP binding cassette transporter A1 ,Biochemistry ,QD415-436 - Abstract
The role of endothelial ABCA1 expression in reverse cholesterol transport (RCT) was examined in transgenic mice, using the endothelial-specific Tie2 promoter. Human ABCA1 (hABCA1) was significantly expressed in endothelial cells (EC) of most tissues except the liver. Increased expression of ABCA1 was not observed in resident peritoneal macrophages. ApoA-I-mediated cholesterol efflux from aortic EC was 2.6-fold higher (P < 0.0001) for cells from transgenic versus control mice. On normal chow diet, Tie2 hABCA1 transgenic mice had a 25% (P < 0.0001) increase in HDL-cholesterol (HDL-C) and more than a 2-fold increase of eNOS mRNA in the aorta (P < 0.04). After 6 months on a high-fat, high-cholesterol (HFHC) diet, transgenic mice compared with controls had a 40% increase in plasma HDL-C (P < 0.003) and close to 40% decrease in aortic lesions (P < 0.02). Aortas from HFHC-fed transgenic mice also showed gene expression changes consistent with decreased inflammation and apoptosis. Beneficial effects of the ABCA1 transgene on HDL-C levels or on atherosclerosis were absent when the transgene was transferred onto ApoE or Abca1 knockout mice. In summary, expression of hABCA1 in EC appears to play a role in decreasing diet-induced atherosclerosis in mice and is associated with increased plasma HDL-C levels and beneficial gene expression changes in EC.
- Published
- 2012
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23. Hepatic ABCG5/G8 overexpression reduces apoB-lipoproteins and atherosclerosis when cholesterol absorption is inhibited
- Author
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Federica Basso, Lita A. Freeman, Carol Ko, Charles Joyce, Marcelo J. Amar, Robert D. Shamburek, Terese Tansey, Fairwell Thomas, Justina Wu, Beverly Paigen, Alan T. Remaley, Silvia Santamarina-Fojo, and H. Bryan Brewer, Jr.
- Subjects
ABC transporters ,ABCG subfamily ,ezetimibe ,non-HDL-cholesterol ,biliary sterol secretion ,hepatic cholesterol homeostasis ,Biochemistry ,QD415-436 - Abstract
We previously reported that liver-specific overexpression of ABCG5/G8 in mice is not atheroprotective, suggesting that increased biliary cholesterol secretion must be coupled with decreased intestinal cholesterol absorption to increase net sterol loss from the body and reduce atherosclerosis. To evaluate this hypothesis, we fed low density lipoprotein receptor-knockout (LDLr-KO) control and ABCG5/G8-transgenic (ABCG5/G8-Tg)×LDLr-KO mice, which overexpress ABCG5/G8 only in liver, a Western diet containing ezetimibe to reduce intestinal cholesterol absorption. On this dietary regimen, liver-specific ABCG5/G8 overexpression increased hepatobiliary cholesterol concentration and secretion rates (1.5-fold and 1.9-fold, respectively), resulting in 1.6-fold increased fecal cholesterol excretion, decreased hepatic cholesterol, and increased (4.4-fold) de novo hepatic cholesterol synthesis versus LDLr-KO mice. Plasma lipids decreased (total cholesterol, 32%; cholesteryl ester, 32%; free cholesterol, 30%), mostly as a result of reduced non-high density lipoprotein-cholesterol and apolipoprotein B (apoB; 36% and 25%, respectively). ApoB-containing lipoproteins were smaller and lipid-depleted in ABCG5/G8-Tg×LDLr-KO mice. Kinetic studies revealed similar 125I-apoB intermediate density lipoprotein/LDL fractional catabolic rates, but apoB production rates were decreased 37% in ABCG5/G8-Tg×LDLr-KO mice. Proximal aortic atherosclerosis decreased by 52% (male) and 59% (female) in ABCG5/G8-Tg×LDLr-KO versus LDLr-KO mice fed the Western/ezetimibe diet. Thus, increased biliary secretion, resulting from hepatic ABCG5/G8 overexpression, reduces atherogenic risk in LDLr-KO mice fed a Western diet containing ezetimibe. These findings identify distinct roles for liver and intestinal ABCG5/G8 in modulating sterol metabolism and atherosclerosis.
- Published
- 2007
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24. Apolipoprotein A-I activates Cdc42 signaling through the ABCA1 transporter
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Jerzy-Roch Nofer, Alan T. Remaley, Renata Feuerborn, Iza Wolinnéska, Thomas Engel, Arnold von Eckardstein, and Gerd Assmann
- Subjects
ATP binding cassette transporter A1 ,high density lipoproteins ,cholesterol efflux ,Biochemistry ,QD415-436 - Abstract
It has been suggested that the signal transduction initiated by apolipoprotein A-I (apoA-I) activates key proteins involved in cholesterol efflux. ABCA1 serves as a binding partner for apoA-I, but its participation in apoA-I-induced signaling remains uncertain. We show that the exposure of human fibroblasts to ABCA1 ligands (apolipoproteins and amphipathic helical peptides) results in the generation of intracellular signals, including activation of the small G-protein Cdc42, protein kinases (PAK-1 and p54JNK), and actin polymerization. ApoA-I-induced signaling was abrogated by glyburide, an inhibitor of the ABC transporter family, and in fibroblasts from patients with Tangier disease, which do not express ABCA1. Conversely, induction of ABCA1 expression with the liver X receptor agonist, T0901317, and the retinoid X receptor agonist, R0264456, potentiated apoA-I-induced signaling. Similar effects were observed in HEK293 cells overexpressing ABCA1-green fluorescent protein (GFP) fusion protein, but not ABCA1-GFP (K939M), which fails to hydrolyze ATP, or a nonfunctional ABCA1-GFP with a truncated C terminus. We further found that Cdc42 coimmunoprecipitates with ABCA1 in ABCA1-GFP-expressing HEK293 cells exposed to apoA-I but not in cells expressing ABCA1 mutants. We conclude that ABCA1 transduces signals from apoA-I by complexing and activating Cdc42 and downstream kinases and, therefore, acts as a full apoA-I receptor.
- Published
- 2006
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25. The orphan nuclear receptor LRH-1 activates the ABCG5/ABCG8 intergenic promoter
- Author
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Lita A. Freeman, Arion Kennedy, Justina Wu, Samantha Bark, Alan T. Remaley, Silvia Santamarina-Fojo, and H. Bryan Brewer, Jr.
- Subjects
ATP binding cassette transporter ,CPF ,liver receptor homolog-1 ,FTF ,FXR ,SHP ,Biochemistry ,QD415-436 - Abstract
The ATP binding cassette (ABC) half-transporters ABCG5 and ABCG8 facilitate biliary and intestinal removal of neutral sterols. Here, we identify a binding site for the orphan nuclear receptor liver receptor homolog-1 (LRH-1) at nt 134–142 of the ABCG5/ABCG8 intergenic region necessary for the activity of both the ABCG5 and ABCG8 promoters. Mutating this LRH-1 binding site reduced promoter activity of the human ABCG5/ABCG8 intergenic region more than 7-fold in HepG2 and Caco2 cells. Electrophoretic mobility shift assays with HepG2 nuclear extracts demonstrated specific binding of LRH-1 to the LRH-1 binding motif in the human ABCG5/ABCG8 intergenic region. LRH-1 overexpression increased promoter activity up to 1.6-fold and 3-fold in Caco2 and 293 cells, respectively. Finally, deoxycholic acid repressed the ABCG5 and ABCG8 promoters, consistent with bile acid regulation via the farnesoid X receptor-small heterodimeric partner-LRH-1 pathway.These results demonstrate that LRH-1 is a positive transcription factor for ABCG5 and ABCG8 and, in conjunction with studies on LRH-1 activation of other promoters, identify LRH-1 as a “master regulator” for genes involved in sterol and bile acid secretion from liver and intestine.
- Published
- 2004
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26. Synthetic amphipathic helical peptides promote lipid efflux from cells by an ABCA1-dependent and an ABCA1-independent pathway
- Author
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Alan T. Remaley, Fairwell Thomas, John A. Stonik, Steve J. Demosky, Samantha E. Bark, Edward B. Neufeld, Alexander V. Bocharov, Tatyana G. Vishnyakova, Amy P. Patterson, Thomas L. Eggerman, Silvia Santamarina-Fojo, and H.Bryan Brewer
- Subjects
ATP binding cassette transporter ,apolipoprotein A-I ,high density lipoprotein ,Biochemistry ,QD415-436 - Abstract
In order to examine the necessary structural features for a protein to promote lipid efflux by the ABCA1 transporter, synthetic peptides were tested on ABCA1-transfected cells (ABCA1 cells) and on control cells. L-37pA, an l amino acid peptide that contains two class-A amphipathic helices linked by proline, showed a 4-fold increase in cholesterol and phospholipid efflux from ABCA1 cells compared to control cells. The same peptide synthesized with a mixture of l and d amino acids was less effective than L-37pA in solubilizing dimyristoyl phosphatidyl choline vesicles and in effluxing lipids. In contrast, the 37pA peptide synthesized with all d amino acids (D-37pA) was as effective as L-37pA. Unlike apoA-I, L-37pA and D-37pA were also capable, although at a reduced rate, of causing lipid efflux independent of ABCA1 from control cells, Tangier disease cells, and paraformaldehyde fixed ABCA1 cells. The ability of peptides to bind to cells correlated with their lipid affinity.In summary, the amphipathic helix was found to be a key structural motif for peptide-mediated lipid efflux from ABCA1, but there was no stereoselective requirement. In addition, unlike apoA-I, synthetic peptides can also efflux lipid by a passive, energy-independent pathway that does not involve ABCA1 but does depend upon their lipid affinity.
- Published
- 2003
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27. Role of the hepatic ABCA1 transporter in modulating intrahepatic cholesterol and plasma HDL cholesterol concentrations
- Author
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Federica Basso, Lita Freeman, Catherine L. Knapper, Alan Remaley, John Stonik, Edward B. Neufeld, Terese Tansey, Marcelo J.A. Amar, Jamila Fruchart-Najib, Nicholas Duverger, Silvia Santamarina-Fojo, and H.Bryan Brewer, Jr.
- Subjects
reverse cholesterol transport ,lipoprotein ,cholesterol ,Tangier disease ,Biochemistry ,QD415-436 - Abstract
The current model for reverse cholesterol transport proposes that HDL transports excess cholesterol derived primarily from peripheral cells to the liver for removal. However, recent studies in ABCA1 transgenic mice suggest that the liver itself may be a major source of HDL cholesterol (HDL-C). To directly investigate the hepatic contribution to plasma HDL-C levels, we generated an adenovirus (rABCA1-GFP-AdV) that targets expression of mouse ABCA1-GFP in vivo to the liver. Compared with mice injected with control AdV, infusion of rABCA1-GFP-AdV into C57Bl/6 mice resulted in increased expression of mouse ABCA1 mRNA and protein in the liver. ApoA-I-dependent cholesterol efflux was increased 2.6-fold in primary hepatocytes isolated 1 day after rABCA1-GFP-AdV infusion. Hepatic ABCA1 expression in C57Bl/6 mice (n = 15) raised baseline levels of TC, PL, FC, HDL-C, apoE, and apoA-I by 150–300% (P < 0.05 all). ABCA1 expression led to significant compensatory changes in expression of genes that increase hepatic cholesterol, including HMG-CoA reductase (3.5-fold), LDLr (2.1-fold), and LRP (5-fold) in the liver.These combined results demonstrate that ABCA1 plays a key role in hepatic cholesterol efflux, inducing pathways that modulate cholesterol homeostasis in the liver, and establish the liver as a major source of plasma HDL-C.
- Published
- 2003
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28. The E-box motif in the proximal ABCA1 promoter mediates transcriptional repression of the ABCA1 gene
- Author
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Xiao-Ping Yang, Lita A. Freeman, Catherine L. Knapper, Marcelo J.A. Amar, Alan Remaley, H. Bryan Brewer, Jr., and Silvia Santamarina-Fojo
- Subjects
high density lipoproteins ,ATP-binding cassette transporter ,E-box ,Biochemistry ,QD415-436 - Abstract
To identify regulatory elements in the proximal human ATP-binding cassette transporter A1 (hABCA1) gene promoter we transfected RAW cells with plasmids containing mutations in the E-box, AP1, and liver X receptor (LXR) elements as well as the two Sp1 motifs. Point mutations in either Sp1 site or in the AP1 site had only a minor effect whereas mutation of the LXR element decreased promoter activity. In contrast, mutation or deletion of the E-box motif caused a 3-fold increase in transcriptional activity under basal conditions. Gel shift and DNaseI footprint analysis showed binding of a protein or protein complex to this region. Preincubation of nuclear extracts with antibodies established that USF1, USF2, and fos related antigen (Fra) 2 bind to DNA sequences in the human ABCA1 promoter that contains the intact E-box but not the mutant or deleted E-box. Co-transfection of USF1 and USF2 enhanced, but Fra2 repressed, ABCA1 promoter activity. Thus, a complex consisting of USF1, USF2, and Fra2 binds the E-box motif 147 bp upstream of the transcriptional start site and facilitates repression of the human ABCA1 promoter. These combined studies identify a novel site in the human ABCA1 promoter involved in the regulation of ABCA1 gene expression.—Yang, X-P., L. A. Freeman, C. L. Knapper, M. J. A. Amar, A. Remaley, H. B. Brewer, Jr., and S. Santamarina-Fojo. The E-box motif in the proximal ABCA1 promoter mediates transcriptional repression of the ABCA1 gene.
- Published
- 2002
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29. Coexpression of novel furin-resistant LPL variants with lipase maturation factor 1 enhances LPL secretion and activity
- Author
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Ellis M. Pearson, Ming Jing Wu, Aspen R. Gutgsell, Alan T. Remaley, Anna Wolska, Saskia B. Neher, and Benjamin S. Roberts
- Subjects
Male ,0301 basic medicine ,Glycan ,Blotting, Western ,QD415-436 ,Biochemistry ,law.invention ,Mice ,03 medical and health sciences ,Endocrinology ,trafficking ,In vivo ,law ,protein purification ,Protein purification ,Methods ,Animals ,Humans ,Secretion ,Furin ,chemistry.chemical_classification ,Lipoprotein lipase ,biology ,Chemistry ,digestive, oral, and skin physiology ,Membrane Proteins ,nutritional and metabolic diseases ,Biological Transport ,Cell Biology ,Lipoprotein Lipase ,030104 developmental biology ,Enzyme ,biology.protein ,Recombinant DNA ,lipids (amino acids, peptides, and proteins) - Abstract
LPL is a secreted enzyme that hydrolyzes triglycerides from circulating lipoproteins. Individuals lacking LPL suffer from severe hypertriglyceridemia, a risk factor for acute pancreatitis. One potential treatment is to administer recombinant LPL as a protein therapeutic. However, use of LPL as a protein therapeutic is limited because it is an unstable enzyme that is difficult to produce in large quantities. Furthermore, these considerations also limit structural and biochemical studies that are needed for large-scale drug discovery efforts. We demonstrate that the yield of purified LPL can be dramatically enhanced by coexpressing its maturation factor, LMF1, and by introducing novel mutations into the LPL sequence to render it resistant to proteolytic cleavage by furin. One of these mutations introduces a motif for addition of an N-linked glycan to the furin-recognition site. Furin-resistant LPL has previously been reported, but is not commonly used. We show that our modifications do not adversely alter LPL's enzymatic activity, stability, or in vivo function. Together, these data show that furin-resistant LPL is a useful reagent for both biochemical and biomedical studies.
- Published
- 2018
30. Regulation and intracellular trafficking of the ABCA1 transporter
- Author
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Silvia Santamarina-Fojo, Alan T. Remaley, Edward B. Neufeld, and H. Bryan Brewer, Jr.
- Subjects
Tangier disease ,HDL ,ABC transporters ,Biochemistry ,QD415-436 - Abstract
The discovery of the role of the ATP-binding cassette transporter A1 (ABCA1) in mediating apolipoprotein A-I-mediated efflux has led to a dramatic increase in our knowledge of the molecular mechanisms involved in cholesterol efflux and cellular metabolism. In this review, we discuss several aspects of ABCA1 regulation including i) transcriptional regulation, ii) substrate specificity and availability, iii) accessory proteins, iv) acceptor specificity and availability, and v) protein trafficking. The majority of studies of ABCA1 regulation to date have focused on the identification of promoter elements that determine ABCA1 gene transcription. Here we also review the potential functional role of ABCA1 in reverse cholesterol transport. Given the key role that ABCA1 plays in cholesterol homeostasis, it is likely that there are multiple mechanisms for controlling the overall transporter activity of ABCA1. —Santamarina-Fojo, S., A. T. Remaley, E. B. Neufeld, and H. B. Brewer, Jr. Regulation and intracellular trafficking of the ABCA1 transporter.
- Published
- 2001
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31. Transgelin: a new gene involved in LDL endocytosis identified by a genome-wide CRISPR-Cas9 screen
- Author
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Ozan Dikilitas, Michael M. Mendelson, Jingrong Tang, Alan T. Remaley, Aruna T. Bansal, Szilard Voros, Boris L. Vaisman, Iftikhar J. Kullo, Promotto Islam, Edward B. Neufeld, Christian A. Combs, Diego Lucero, Lita A. Freeman, and Yuesheng Li
- Subjects
transgelin ,cellular LDL uptake ,Cas9 ,In silico ,Microfilament Proteins ,LDL receptor ,Muscle Proteins ,QD415-436 ,Cell Biology ,Biology ,Endocytosis ,Phenotype ,Genome ,Biochemistry ,LDL ,Cell biology ,Endocrinology ,endocytosis ,CRISPR ,lipids (amino acids, peptides, and proteins) ,whole-genome CRISPR-Cas9 screen ,Gene ,Lipoprotein - Abstract
A significant proportion of patients with elevated LDL and a clinical presentation of familial hypercholesterolemia do not carry known genetic mutations associated with hypercholesterolemia, such as defects in the LDL receptor. To identify new genes involved in the cellular uptake of LDL, we developed a novel whole-genome clustered regularly interspaced short palindromic repeat-Cas9 KO screen in HepG2 cells. We identified transgelin (TAGLN), an actin-binding protein, as a potentially new gene involved in LDL endocytosis. In silico validation demonstrated that genetically predicted differences in expression of TAGLN in human populations were significantly associated with elevated plasma lipids (triglycerides, total cholesterol, and LDL-C) in the Global Lipids Genetics Consortium and lipid-related phenotypes in the UK Biobank. In biochemical studies, TAGLN-KO HepG2 cells showed a reduction in cellular LDL uptake, as measured by flow cytometry. In confocal microscopy imaging, TAGLN-KO cells had disrupted actin filaments as well as an accumulation of LDL receptor on their surface because of decreased receptor internalization. Furthermore, TAGLN-KO cells exhibited a reduction in total and free cholesterol content, activation of SREBP2, and a compensatory increase in cholesterol biosynthesis. TAGLN deficiency also disrupted the uptake of VLDL and transferrin, other known cargoes for receptors that depend upon clathrin-mediated endocytosis. Our data suggest that TAGLN is a novel factor involved in the actin-dependent phase of clathrin-mediated endocytosis of LDL. The identification of novel genes involved in the endocytic uptake of LDL may improve the diagnosis of hypercholesterolemia and provide future therapeutic targets for the prevention of cardiovascular disease.
- Published
- 2022
32. Differential rate of cholesterol efflux from the apical and basolateral membranes of MDCK cells
- Author
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A.T. Remaley, B.D. Farsi, A.C. Shirali, J.M. Hoeg, and H.B. Brewer, Jr.
- Subjects
cholesterol efflux ,high density lipoprotein ,cholesterol ,atherosclerosis ,Biochemistry ,QD415-436 - Abstract
Epithelial cells contain two distinct membrane surfaces, the apical and basolateral plasma membranes, which have different lipid and protein compositions. In order to assess the effect of the compositional differences of the apical and basolateral membranes on their ability to undergo cholesterol efflux, MDCK cells were radiolabeled with [3H]cholesterol and grown as a polarized monolayer on filter inserts, that separate the upper apical compartment from the lower basolateral compartment. The rate of cholesterol efflux from the basolateral membrane into media containing HDL in the basolateral compartment was 6.3%/h ± 0.7, whereas HDL-mediated efflux from the apical membrane was approximately 3-fold slower (1.9%/h ± 0.3). In contrast, Fu5AH cells, which do not form distinct polarized membrane domains, had a similar rate of HDL-mediated cholesterol efflux into the apical and basolateral compartments. Similar to HDL, other cholesterol acceptors, namely LDL, bovine serum albumin, and a lipid emulsion, also showed a decreased rate of cholesterol efflux from the apical membrane surface versus the basolateral membrane. Compared to the basolateral membrane, the apical membrane was also found to be more resistant to cholesterol oxidase treatment, to bind less HDL, and to take up less cholesterol from the medium. In conclusion, cholesterol efflux occurred less readily from the apical membrane than from the basolateral membrane for all types of acceptors tested. These results suggest that differences in the composition of the apical and basolateral membrane lead to a relative decrease in cholesterol desorption from the apical membrane and hence a reduced rate of cholesterol efflux.—Remaley, A. T., B. D. Farsi, A. C. Shirali, J. M. Hoeg, and H. B. Brewer, Jr. Differential rate of cholesterol efflux from the apical and basolateral membranes of MDCK cells. J. Lipid Res. 1998. 39: 1231–1238.
- Published
- 1998
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33. Perioperative high density lipoproteins, oxidative stress, and kidney injury after cardiac surgery
- Author
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Smith, Loren E., primary, Smith, Derek K., additional, Yancey, Patricia G., additional, Kon, Valentina, additional, Remaley, Alan T., additional, Billings, Frederic T., additional, and Linton, MacRae F., additional
- Published
- 2021
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34. Pregnancy is accompanied by larger high density lipoprotein particles and compositionally distinct subspecies
- Author
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Melchior, John T., primary, Swertfeger, Debi K., additional, Morris, Jamie, additional, Street, Scott E., additional, Warshak, Carri R., additional, Welge, Jeffrey A., additional, Remaley, Alan T., additional, Catov, Janet M., additional, Davidson, W. Sean, additional, and Woollett, Laura A., additional
- Published
- 2021
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- View/download PDF
35. Polarized secretion of apoA-I and apoA-II by transfected MDCK cells.
- Author
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A T Remaley and J M Hoeg
- Subjects
Biochemistry ,QD415-436 - Abstract
Apolipoproteins (apo) are secreted preferentially from the basolateral surface of hepatocytes and enterocytes. The polarized secretion of proteins is either mediated by a protein-dependent sorting signal or by a cell-dependent default pathway. In order to determine the mechanism for the polarized secretion of apolipoproteins, we examined the secretion of apoA-I and apoA-II in transfected Madin-Darby canine kidney (MDCK) cells. Transfected MDCK cells and Caco-2 cells were grown as a polarized monolayer on tissue culture inserts, which separate an upper apical compartment from the lower basolateral compartment, and the secretion of apoA-I and apoA-II into the apical and basolateral compartments was quantitated by immunoprecipitation. Caco-2 cells almost exclusively secreted apoA-I and apoA-II basolaterally, with an apical to basolateral ratio of 18:82 for apoA-I, and 11:89 for apoA-II. In contrast, transfected MDCK cells secreted significant amounts of apoA-I and apoA-II into both compartments, but with a bias toward apical secretion and an apical to basolateral ratio of 66:34 and 68:32, respectively. The polarized secretion of MDCK cells was not due to transcytosis, diffusion, or differential recovery. As assessed by density gradient ultracentrifugation, apoA-I and apoA-II secreted from either the apical or basolateral surface were relatively lipid-poor. Overall, these results suggest that the polarized secretion of apoA-I and apoA-II does not occur by a protein-dependent sorting signal, but by a cell-dependent default pathway that leads to preferential basolateral secretion by Caco-2 cells and both apical and basolateral secretion in MDCK cells, but with a bias toward apical secretion.
- Published
- 1995
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36. Identification of novel differentially expressed hepatic genes in cholesterol-fed rabbits by a non-targeted gene approach.
- Author
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A T Remaley, U K Schumacher, H R Amouzadeh, H B Brewer, and J M Hoeg
- Subjects
Biochemistry ,QD415-436 - Abstract
Several key genes involved in cholesterol metabolism are known to be directly regulated by cholesterol. The possible indirect effect, however, of increased levels of cellular cholesterol on gene expression and its possible role in cholesterol metabolism and atherosclerosis has not been thoroughly explored. In order to determine the overall effect of cholesterol on gene expression, we isolated differentially expressed genes from a PCR-based subtraction library prepared from the liver of chow-fed and cholesterol-fed rabbits. A total of nine upregulated and four down-regulated cDNA fragments were isolated. As determined by Northern blot analysis, the expression of the isolated cDNAs began to change as early as the first week on the cholesterol-rich diet or as late as 4 weeks, which corresponded with hepatic cholesterol accumulation. Three of the cDNAs were identified by DNA sequence homology, whereas the remaining cDNAs had no significant homology match. CYP1A1, a cytochrome P450 isoenzyme, was found to be down-regulated in hepatocytes by cholesterol feeding. Osteopontin and Mac-2, which are produced by macrophages, were found to be up-regulated in Kupffer cells by cholesterol feeding. Overall these results demonstrate the usefulness of the subtraction library approach for identifying new candidate genes for exploring the pathogenesis of atherosclerosis.
- Published
- 1995
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37. Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood
- Author
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Ohkawa, Ryunosuke, primary, Low, Hann, additional, Mukhamedova, Nigora, additional, Fu, Ying, additional, Lai, Shao-Jui, additional, Sasaoka, Mai, additional, Hara, Ayuko, additional, Yamazaki, Azusa, additional, Kameda, Takahiro, additional, Horiuchi, Yuna, additional, Meikle, Peter J., additional, Pernes, Gerard, additional, Lancaster, Graeme, additional, Ditiatkovski, Michael, additional, Nestel, Paul, additional, Vaisman, Boris, additional, Sviridov, Denis, additional, Murphy, Andrew, additional, Remaley, Alan T., additional, Sviridov, Dmitri, additional, and Tozuka, Minoru, additional
- Published
- 2020
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- View/download PDF
38. Lecithin:cholesterol acyltransferase: symposium on 50 years of biomedical research from its discovery to latest findings
- Author
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Norum, Kaare R., primary, Remaley, Alan T., additional, Miettinen, Helena E., additional, Strøm, Erik H., additional, Balbo, Bruno E.P., additional, Sampaio, Carlos A.T.L., additional, Wiig, Ingrid, additional, Kuivenhoven, Jan Albert, additional, Calabresi, Laura, additional, Tesmer, John J., additional, Zhou, Mingyue, additional, Ng, Dominic S., additional, Skeie, Bjørn, additional, Karathanasis, Sotirios K., additional, Manthei, Kelly A., additional, and Retterstøl, Kjetil, additional
- Published
- 2020
- Full Text
- View/download PDF
39. Pregnancy is accompanied by larger high density lipoprotein particles and compositionally distinct subspecies
- Author
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Jeffrey A. Welge, Carri R. Warshak, Janet M. Catov, Debi K. Swertfeger, Scott E. Street, Jamie Morris, John T. Melchior, Laura A. Woollett, Alan T. Remaley, and W. Sean Davidson
- Subjects
Adult ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Adolescent ,Proteome ,QD415-436 ,Biochemistry ,APOA4, apolipoprotein A-IV ,lipoprotein size ,AGT, angiotensinogen ,Young Adult ,APOA4 ,chemistry.chemical_compound ,proteomics ,Endocrinology ,High-density lipoprotein ,Internal medicine ,medicine ,Humans ,Particle Size ,ALB, albumin ,phospholipids ,nuclear magnetic resonance spectroscopy ,mass spectrometry ,lipoprotein metabolism ,Fetus ,Pregnancy ,Cholesterol ,PZP, pregnancy zone protein ,HDL-C, high density lipoprotein-cholesterol ,dyslipidemia ,lipoprotein ,Albumin ,LFQ, label-free quantification ,CFB, complement factor B ,Cell Biology ,medicine.disease ,LC-MS ,PREGNANCY ZONE PROTEIN ,chemistry ,Female ,lipids (amino acids, peptides, and proteins) ,pregnancy ,Lipoproteins, HDL ,Research Article ,Chromatography, Liquid ,Lipoprotein - Abstract
Pregnancy is accompanied by significant physiological changes, which can impact the health and development of the fetus and mother. Pregnancy-induced changes in plasma lipoproteins are well documented, with modest to no impact observed on the generic measure of high density lipoprotein (HDL) cholesterol. However, the impact of pregnancy on the concentration and composition of HDL subspecies has not been examined in depth. In this prospective study, we collected plasma from 24 nonpregnant and 19 pregnant women in their second trimester. Using nuclear magnetic resonance (NMR), we quantified 11 different lipoprotein subspecies from plasma by size, including three in the HDL class. We observed an increase in the number of larger HDL particles in pregnant women, which were confirmed by tracking phospholipids across lipoproteins using high-resolution gel-filtration chromatography. Using liquid chromatography-mass spectrometry (LC-MS), we identified 87 lipid-associated proteins across size-speciated fractions. We report drastic shifts in multiple protein clusters across different HDL size fractions in pregnant females compared with nonpregnant controls that have major implications on HDL function. These findings significantly elevate our understanding of how changes in lipoprotein metabolism during pregnancy could impact the health of both the fetus and the mother.
- Published
- 2021
40. A thumbwheel mechanism for APOA1 activation of LCAT activity in HDL
- Author
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Loren E. Smith, Amy S. Shah, W. Gray Jerome, Alan T. Remaley, Jamie Morris, Scott E. Street, John T. Melchior, Allison L Cooke, W. Sean Davidson, Andrew B. Herr, Thomas B. Thompson, Rong Huang, and Jere P. Segrest
- Subjects
0301 basic medicine ,lecithin:cholesterol acyltransferase ,high density lipoprotein metabolism ,Stereochemistry ,QD415-436 ,Biochemistry ,Epitope ,Phosphatidylcholine-Sterol O-Acyltransferase ,03 medical and health sciences ,chemistry.chemical_compound ,Endocrinology ,High-density lipoprotein ,proteomics ,Molecule ,Humans ,Lipid bilayer ,Research Articles ,chemistry.chemical_classification ,030102 biochemistry & molecular biology ,Apolipoprotein A-I ,Cholesterol ,Cholesterol, HDL ,Cell Biology ,Enzyme Activation ,030104 developmental biology ,Enzyme ,chemistry ,high density lipoprotein ,Helix ,Mutation ,cholesterol metabolism ,lipids (amino acids, peptides, and proteins) ,apolipoproteins ,Cysteine - Abstract
APOA1 is the most abundant protein in HDL. It modulates interactions that affect HDL';s cardioprotective functions, in part via its activation of the enzyme, LCAT. On nascent discoidal HDL, APOA1 comprises 10 α-helical repeats arranged in an anti-parallel stacked-ring structure that encapsulates a lipid bilayer. Previous chemical cross-linking studies suggested that these APOA1 rings can adopt at least two different orientations, or registries, with respect to each other; however, the functional impact of these structural changes is unknown. Here, we placed cysteine residues at locations predicted to form disulfide bonds in each orientation and then measured APOA1';s ability to adopt the two registries during HDL particle formation. We found that most APOA1 oriented with the fifth helix of one molecule across from fifth helix of the other (5/5 helical registry), but a fraction adopted a 5/2 registry. Engineered HDLs that were locked in 5/5 or 5/2 registries by disulfide bonds equally promoted cholesterol efflux from macrophages, indicating functional particles. However, unlike the 5/5 registry or the WT, the 5/2 registry impaired LCAT cholesteryl esterification activity (P< 0.001), despite LCAT binding equally to all particles. Chemical cross-linking studies suggest that full LCAT activity requires a hybrid epitope composed of helices 5–7 on one APOA1 molecule and helices 3–4 on the other. Thus, APOA1 may use a reciprocating thumbwheel-like mechanism to activate HDL-remodeling proteins.
- Published
- 2018
41. Plasma lipoprotein-X quantification on filipin-stained gels: monitoring recombinant LCAT treatment ex vivo
- Author
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Freeman, Lita A., primary, Shamburek, Robert D., additional, Sampson, Maureen L., additional, Neufeld, Edward B., additional, Sato, Masaki, additional, Karathanasis, Sotirios K., additional, and Remaley, Alan T., additional
- Published
- 2019
- Full Text
- View/download PDF
42. Coexpression of novel furin-resistant LPL variants with lipase maturation factor 1 enhances LPL secretion and activity
- Author
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Wu, Ming Jing, primary, Wolska, Anna, additional, Roberts, Benjamin S., additional, Pearson, Ellis M., additional, Gutgsell, Aspen R., additional, Remaley, Alan T., additional, and Neher, Saskia B., additional
- Published
- 2018
- Full Text
- View/download PDF
43. A thumbwheel mechanism for APOA1 activation of LCAT activity in HDL[S]
- Author
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Cooke, Allison L., primary, Morris, Jamie, additional, Melchior, John T., additional, Street, Scott E., additional, Jerome, W.Gray, additional, Huang, Rong, additional, Herr, Andrew B., additional, Smith, Loren E., additional, Segrest, Jere P., additional, Remaley, Alan T., additional, Shah, Amy S., additional, Thompson, Thomas B., additional, and Davidson, W.Sean, additional
- Published
- 2018
- Full Text
- View/download PDF
44. Complexity of microRNA function and the role of isomiRs in lipid homeostasis
- Author
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Praveen Sethupathy, Jeanette Baran-Gale, Alan T. Remaley, and Kasey C. Vickers
- Subjects
Gene isoform ,Genetics ,Regulation of gene expression ,Small RNA ,microRNA isoform ,Genetic Variation ,Cell Biology ,Computational biology ,QD415-436 ,Biology ,nontemplated additions ,Biochemistry ,MicroRNAs ,Endocrinology ,IsomiR ,Gene Expression Regulation ,Liver ,RNA editing ,microRNA ,Thematic Review: microRNAs ,lipid metabolism ,Gene silencing ,Homeostasis ,Humans ,Biogenesis - Abstract
MicroRNAs (miRNAs) are key posttranscriptional regulators of biological pathways that govern lipid metabolic phenotypes. Recent advances in high-throughput small RNA sequencing technology have revealed the complex and dynamic repertoire of miRNAs. Specifically, it has been demonstrated that a single genomic locus can give rise to multiple, functionally distinct miRNA isoforms (isomiR). There are several mechanisms by which isomiRs can be generated, including processing heterogeneity and posttranscriptional modifications, such as RNA editing, exonuclease-mediated nucleotide trimming, and/or nontemplated nucleotide addition (NTA). NTAs are dominant at the 3′-end of a miRNA, are most commonly uridylation or adenlyation events, and are catalyzed by one or more of several nucleotidyl transferase enzymes. 3′ NTAs can affect miRNA stability and/or activity and are physiologically regulated, whereas modifications to the 5′-ends of miRNAs likely alter miRNA targeting activity. Recent evidence also suggests that the biogenesis of specific miRNAs, or small RNAs that act as miRNAs, can occur through unconventional mechanisms that circumvent key canonical miRNA processing steps. The unveiling of miRNA diversity has significantly added to our view of the complexity of miRNA function. In this review we present the current understanding of the biological relevance of isomiRs and their potential role in regulating lipid metabolism.
- Published
- 2013
45. Endothelial expression of human ABCA1 in mice increases plasma HDL cholesterol and reduces diet-induced atherosclerosis
- Author
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Mona Ghias, Stewart J. Levine, Stephen J. Demosky, Cuilian Dai, Boris L. Vaisman, John A. Stonik, Alan T. Remaley, Maureen Sampson, and Cathy Knapper
- Subjects
Genetically modified mouse ,Apolipoprotein E ,medicine.medical_specialty ,Endothelium ,Transgene ,Mice, Transgenic ,Inflammation ,QD415-436 ,Biology ,Biochemistry ,Cholesterol, Dietary ,Mice ,chemistry.chemical_compound ,Endocrinology ,Internal medicine ,medicine ,Animals ,Humans ,Aorta ,Apolipoprotein A-I ,Cholesterol ,Cholesterol, HDL ,Reverse cholesterol transport ,Cell Biology ,Atherosclerosis ,Dietary Fats ,endothelial cells ,reverse cholesterol transport ,medicine.anatomical_structure ,chemistry ,high density lipoprotein ,ABCA1 ,biology.protein ,ATP-Binding Cassette Transporters ,Female ,lipids (amino acids, peptides, and proteins) ,Endothelium, Vascular ,ATP binding cassette transporter A1 ,medicine.symptom ,Patient-Oriented and Epidemiological Research ,cholesterol efflux ,ATP Binding Cassette Transporter 1 - Abstract
The role of endothelial ABCA1 expression in reverse cholesterol transport (RCT) was examined in transgenic mice, using the endothelial-specific Tie2 promoter. Human ABCA1 (hABCA1) was significantly expressed in endothelial cells (EC) of most tissues except the liver. Increased expression of ABCA1 was not observed in resident peritoneal macrophages. ApoA-I-mediated cholesterol efflux from aortic EC was 2.6-fold higher (P < 0.0001) for cells from transgenic versus control mice. On normal chow diet, Tie2 hABCA1 transgenic mice had a 25% (P < 0.0001) increase in HDL-cholesterol (HDL-C) and more than a 2-fold increase of eNOS mRNA in the aorta (P < 0.04). After 6 months on a high-fat, high-cholesterol (HFHC) diet, transgenic mice compared with controls had a 40% increase in plasma HDL-C (P < 0.003) and close to 40% decrease in aortic lesions (P < 0.02). Aortas from HFHC-fed transgenic mice also showed gene expression changes consistent with decreased inflammation and apoptosis. Beneficial effects of the ABCA1 transgene on HDL-C levels or on atherosclerosis were absent when the transgene was transferred onto ApoE or Abca1 knockout mice. In summary, expression of hABCA1 in EC appears to play a role in decreasing diet-induced atherosclerosis in mice and is associated with increased plasma HDL-C levels and beneficial gene expression changes in EC.
- Published
- 2012
46. High density lipoproteins and type 2 inflammatory biomarkers are negatively correlated in atopic asthmatics
- Author
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Barochia, Amisha V., primary, Gordon, Elizabeth M., additional, Kaler, Maryann, additional, Cuento, Rosemarie A., additional, Theard, Patricia, additional, Figueroa, Debbie M., additional, Yao, Xianglan, additional, Weir, Nargues A., additional, Sampson, Maureen L., additional, Stylianou, Mario, additional, Choy, David F., additional, Holweg, Cecile T.J., additional, Remaley, Alan T., additional, and Levine, Stewart J., additional
- Published
- 2017
- Full Text
- View/download PDF
47. Role of the hepatic ABCA1 transporter in modulating intrahepatic cholesterol and plasma HDL cholesterol concentrations
- Author
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Silvia Santamarina-Fojo, Marcelo Amar, Nicholas Duverger, Alan T. Remaley, Federica Basso, H. Bryan Brewer, Edward B. Neufeld, Catherine L. Knapper, John A. Stonik, Terese Tansey, Lita A. Freeman, and Jamila Fruchart-Najib
- Subjects
Male ,Apolipoprotein E ,Genetically modified mouse ,medicine.medical_specialty ,Lipoproteins ,Recombinant Fusion Proteins ,Tangier disease ,QD415-436 ,Biology ,Biochemistry ,Adenoviridae ,Mice ,chemistry.chemical_compound ,Endocrinology ,Internal medicine ,medicine ,Animals ,Liver X receptor ,Cells, Cultured ,Cholesterol ,Cholesterol, HDL ,Reverse cholesterol transport ,lipoprotein ,nutritional and metabolic diseases ,cholesterol ,Cell Biology ,medicine.disease ,Lipids ,reverse cholesterol transport ,Mice, Inbred C57BL ,Liver ,chemistry ,ABCA1 ,Hepatocytes ,biology.protein ,ATP-Binding Cassette Transporters ,lipids (amino acids, peptides, and proteins) ,ATP Binding Cassette Transporter 1 ,Lipoprotein - Abstract
The current model for reverse cholesterol transport proposes that HDL transports excess cholesterol derived primarily from peripheral cells to the liver for removal. However, recent studies in ABCA1 transgenic mice suggest that the liver itself may be a major source of HDL cholesterol (HDL-C). To directly investigate the hepatic contribution to plasma HDL-C levels, we generated an adenovirus (rABCA1-GFP-AdV) that targets expression of mouse ABCA1-GFP in vivo to the liver. Compared with mice injected with control AdV, infusion of rABCA1-GFP-AdV into C57Bl/6 mice resulted in increased expression of mouse ABCA1 mRNA and protein in the liver. ApoA-I-dependent cholesterol efflux was increased 2.6-fold in primary hepatocytes isolated 1 day after rABCA1-GFP-AdV infusion. Hepatic ABCA1 expression in C57Bl/6 mice (n = 15) raised baseline levels of TC, PL, FC, HDL-C, apoE, and apoA-I by 150–300% (P < 0.05 all). ABCA1 expression led to significant compensatory changes in expression of genes that increase hepatic cholesterol, including HMG-CoA reductase (3.5-fold), LDLr (2.1-fold), and LRP (5-fold) in the liver.These combined results demonstrate that ABCA1 plays a key role in hepatic cholesterol efflux, inducing pathways that modulate cholesterol homeostasis in the liver, and establish the liver as a major source of plasma HDL-C.
- Published
- 2003
48. The E-box motif in the proximal ABCA1 promoter mediates transcriptional repression of the ABCA1 gene
- Author
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Lita A. Freeman, Alan T. Remaley, Xiao-Ping Yang, H. Bryan Brewer, Catherine L. Knapper, Silvia Santamarina-Fojo, and Marcelo Amar
- Subjects
Point mutation ,Mutant ,USF2 ,Promoter ,E-box ,QD415-436 ,Cell Biology ,Biology ,Biochemistry ,Molecular biology ,AP-1 transcription factor ,Endocrinology ,ATP-binding cassette transporter ,ABCA1 Gene ,lipids (amino acids, peptides, and proteins) ,high density lipoproteins ,Psychological repression - Abstract
To identify regulatory elements in the proximal human ATP-binding cassette transporter A1 (hABCA1) gene promoter we transfected RAW cells with plasmids contain- ing mutations in the E-box, AP1, and liver X receptor (LXR) elements as well as the two Sp1 motifs. Point mutations in either Sp1 site or in the AP1 site had only a minor effect whereas mutation of the LXR element decreased promoter activity. In contrast, mutation or deletion of the E-box motif caused a 3-fold increase in transcriptional activity under basal conditions. Gel shift and DNaseI footprint analysis showed binding of a protein or protein complex to this re- gion. Preincubation of nuclear extracts with antibodies es- tablished that USF1, USF2, and fos related antigen (Fra) 2 bind to DNA sequences in the human ABCA1 promoter that contains the intact E-box but not the mutant or deleted E-box. Co-transfection of USF1 and USF2 enhanced, but Fra2 repressed, ABCA1 promoter activity. Thus, a complex consisting of USF1, USF2, and Fra2 binds the E-box motif 147 bp upstream of the transcriptional start site and facilitates repression of the human ABCA1 promoter. These com- bined studies identify a novel site in the human ABCA1 pro- moter involved in the regulation of ABCA1 gene expression. — Yang, X-P., L. A. Freeman, C. L. Knapper, M. J. A. Amar, A. Remaley, H. B. Brewer, Jr., and S. Santamarina-Fojo. The E-box motif in the proximal ABCA1 promoter mediates transcriptional repression of the ABCA1 gene. J. Lipid Res. 2002. 43: 297-306.
- Published
- 2002
49. LCAT deficiency does not impair amyloid metabolism in APP/PS1 mice
- Author
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Jeniffer Chan, Stephen J. Demosky, Veronica Hirsch-Reinshagen, Boris L. Vaisman, Cheryl L. Wellington, Michael Lee, Alan T. Remaley, Alice Ossoli, Anna Wilkinson, Sophie Stukas, and Lita A. Freeman
- Subjects
Apolipoprotein E ,medicine.medical_specialty ,lecithin:cholesterol acyltransferase ,high density lipoprotein metabolism ,Amyloid ,QD415-436 ,Biochemistry ,Phosphatidylcholine-Sterol O-Acyltransferase ,chemistry.chemical_compound ,Mice ,Endocrinology ,Cerebrospinal fluid ,Lecithin Cholesterol Acyltransferase Deficiency ,Internal medicine ,mental disorders ,medicine ,Animals ,Research Articles ,Mice, Knockout ,Amyloid beta-Peptides ,biology ,Apolipoprotein A-I ,Activator (genetics) ,Cholesterol ,Cell Biology ,Alzheimer's disease ,chemistry ,ABCA1 ,biology.protein ,Cholesteryl ester ,lipids (amino acids, peptides, and proteins) ,apolipoproteins ,Lipoprotein - Abstract
A key step in plasma HDL maturation from discoidal to spherical particles is the esterification of cholesterol to cholesteryl ester, which is catalyzed by LCAT. HDL-like lipoproteins in cerebrospinal fluid (CSF) are also spherical, whereas nascent lipoprotein particles secreted from astrocytes are discoidal, suggesting that LCAT may play a similar role in the CNS. In plasma, apoA-I is the main LCAT activator, while in the CNS, it is believed to be apoE. apoE is directly involved in the pathological progression of Alzheimer's disease, including facilitating β-amyloid (Aβ) clearance from the brain, a function that requires its lipidation by ABCA1. However, whether apoE particle maturation by LCAT is also required for Aβ clearance is unknown. Here we characterized the impact of LCAT deficiency on CNS lipoprotein metabolism and amyloid pathology. Deletion of LCAT from APP/PS1 mice resulted in a pronounced decrease of apoA-I in plasma that was paralleled by decreased apoA-I levels in CSF and brain tissue, whereas apoE levels were unaffected. Furthermore, LCAT deficiency did not increase Aβ or amyloid in APP/PS1 LCAT(-/-) mice. Finally, LCAT expression and plasma activity were unaffected by age or the onset of Alzheimer's-like pathology in APP/PS1 mice. Taken together, these results suggest that apoE-containing discoidal HDLs do not require LCAT-dependent maturation to mediate efficient Aβ clearance.
- Published
- 2014
50. Regulation and intracellular trafficking of the ABCA1 transporter
- Author
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H. Bryan Brewer, Alan T. Remaley, Silvia Santamarina-Fojo, and Edward B. Neufeld
- Subjects
HDL ,Reverse cholesterol transport ,Tangier disease ,nutritional and metabolic diseases ,Transporter ,ATP-binding cassette transporter ,hemic and immune systems ,Cell Biology ,QD415-436 ,Biology ,Biochemistry ,Cell biology ,Endocrinology ,ATP Binding Cassette Transporter 1 ,ABC transporters ,ABCA1 ,Transcriptional regulation ,ABCA1 Gene ,biology.protein ,polycyclic compounds ,lipids (amino acids, peptides, and proteins) ,Efflux ,cardiovascular diseases - Abstract
The discovery of the role of the ATP-binding cassette transporter A1 (ABCA1) in mediating apolipoprotein A-I-mediated efflux has led to a dramatic increase in our knowledge of the molecular mechanisms involved in cholesterol efflux and cellular metabolism. In this review, we discuss several aspects of ABCA1 regulation including i) transcriptional regulation, ii) substrate specificity and availability, iii) accessory proteins, iv) acceptor specificity and availability, and v) protein trafficking. The majority of studies of ABCA1 regulation to date have focused on the identification of promoter elements that determine ABCA1 gene transcription. Here we also review the potential functional role of ABCA1 in reverse cholesterol transport. Given the key role that ABCA1 plays in cholesterol homeostasis, it is likely that there are multiple mechanisms for controlling the overall transporter activity of ABCA1. —Santamarina-Fojo, S., A. T. Remaley, E. B. Neufeld, and H. B. Brewer, Jr. Regulation and intracellular trafficking of the ABCA1 transporter.
- Published
- 2001
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