| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- van der Harst, Pim, et al.
(författare)
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Seventy-five genetic loci influencing the human red blood cell
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 492:7429, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- Anaemia is a chief determinant of global ill health, contributing to cognitive impairment, growth retardation and impaired physical capacity. To understand further the genetic factors influencing red blood cells, we carried out a genome-wide association study of haemoglobin concentration and related parameters in up to 135,367 individuals. Here we identify 75 independent genetic loci associated with one or more red blood cell phenotypes at P < 10(-8), which together explain 4-9% of the phenotypic variance per trait. Using expression quantitative trait loci and bioinformatic strategies, we identify 121 candidate genes enriched in functions relevant to red blood cell biology. The candidate genes are expressed preferentially in red blood cell precursors, and 43 have haematopoietic phenotypes in Mus musculus or Drosophila melanogaster. Through open-chromatin and coding-variant analyses we identify potential causal genetic variants at 41 loci. Our findings provide extensive new insights into genetic mechanisms and biological pathways controlling red blood cell formation and function.
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| 3. |
- den Hartigh, Laura J., et al.
(författare)
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Postprandial apoE Isoform and Conformational Changes Associated with VLDL Lipolysis Products Modulate Monocyte Inflammation
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Postprandial hyperlipemia, characterized by increased circulating very low-density lipoproteins (VLDL) and circulating lipopolysaccharide (LPS), has been proposed as a mechanism of vascular injury. Our goal was to examine the interactions between postprandial lipoproteins, LPS, and apoE3 and apoE4 on monocyte activation. Methods and Results: We showed that apoE3 complexed to phospholipid vesicles attenuates LPS-induced THP-1 monocyte cytokine expression, while apoE4 increases expression. ELISA revealed that apoE3 binds to LPS with higher affinity than apoE4. Electron paramagnetic resonance (EPR) spectroscopy of site-directed spin labels placed on specific amino acids of apoE3 showed that LPS interferes with conformational changes normally associated with lipid binding. Specifically, compared to apoE4, apoE bearing the E3-like R112 -> Ser mutation displays increased self association when exposed to LPS, consistent with a stronger apoE3-LPS interaction. Additionally, lipolysis of fasting VLDL from normal human donors attenuated LPS-induced TNF alpha secretion from monocytes to a greater extent than postprandial VLDL, an effect partially reversed by blocking apoE. This effect was reproduced using fasting VLDL lipolysis products from e3/e3 donors, but not from e4/e4 subjects, suggesting that apoE3 on fasting VLDL prevents LPS-induced inflammation more readily than apoE4. Conclusion: Postprandial apoE isoform and conformational changes associated with VLDL dramatically modulate vascular inflammation.
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| 4. |
- Sriram, Renuka, et al.
(författare)
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Imaging apolipoprotein AI in vivo
- 2011
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Ingår i: NMR in Biomedicine. - : Wiley. - 0952-3480. ; 24:7, s. 916-924
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Tidskriftsartikel (refereegranskat)abstract
- Coronary disease risk increases inversely with high-density lipoprotein (HDL) level. The measurement of the biodistribution and clearance of HDL in vivo, however, has posed a technical challenge. This study presents an approach to the development of a lipoprotein MRI agent by linking gadolinium methanethiosulfonate (Gd[MTS-ADO3A]) to a selective cysteine mutation in position 55 of apo AI, the major protein of HDL. The contrast agent targets both liver and kidney, the sites of HDL catabolism, whereas the standard MRI contrast agent, gadolinium-diethylenetriaminepentaacetic acid-bismethylamide (GdDTPA-BMA, gadodiamide), enhances only the kidney image. Using a modified apolipoprotein AI to create an HDL contrast agent provides a new approach to investigate HDL biodistribution, metabolism and regulation in vivo. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 5. |
- Lagerstedt, Jens, et al.
(författare)
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Structure of apolipoprotein A-I's N-terminus on nascent high density lipoprotein.
- 2011
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 286:4, s. 2966-2975
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein A-I (apoA-I) is the major protein component of high density lipoproteins (HDL) and a critical element of cholesterol metabolism. To better elucidate the role of apoA-I structure-function in cholesterol metabolism, the conformation of apoA-I's N-terminus (residues 6-98) on nascent HDL was examined by electron paramagnetic resonance (EPR) spectroscopic analysis. A series of 93 apoA-I variants bearing single nitroxide spin label at positions 6-98 was reconstituted onto 9.6 nm HDL particles (rHDL). These particles were subjected to EPR spectral analysis, measuring regional flexibility and side chain solvent accessibility. Secondary structure was elucidated from side-chain mobility and molecular accessibility, wherein two major α-helical domains were localized to residues 6-34 and 50-98. We identified an unstructured segment (residues 35-39) and a β-strand (residues 40-49) between the two helices. Residues 14, 19, 34, 37, 41 and 58 were examined by EPR on 7.8, 8.4, and 9.6 nm rHDL to assess the effect of particle size on N-terminal structure. Residues 14, 19 and 58 showed no significant rHDL size-dependent spectral or accessibility differences, whereas residues 34, 37, and 41, displayed moderate spectral changes along with substantial rHDL size-dependent differences in molecular accessibility. We have elucidated the secondary structure of the N-terminal domain of apoA-I on 9.6 nm rHDL (residues 6-98) and identified residues in this region that are affected by particle size. We conclude that the inter-helical segment (residues 35-49) plays a role in apoA-I's adaptation to HDL particle size.
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| 6. |
- Lagerstedt, Jens, et al.
(författare)
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The "beta-clasp" model of apolipoprotein A-I - A lipid-free solution structure determined by electron paramagnetic resonance spectroscopy.
- 2012
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002. ; 1821:3, s. 448-455
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein A-I (apoA-I) is the major protein component of high density lipoproteins (HDL) and plays a central role in cholesterol metabolism. The lipid-free/lipid-poor form of apoA-I is the preferred substrate for the ATP-binding cassette transporter A1 (ABCA1). The interaction of apoA-I with ABCA1 leads to the formation of cholesterol laden high density lipoprotein (HDL) particles, a key step in reverse cholesterol transport and the maintenance of cholesterol homeostasis. Knowledge of the structure of lipid-free apoA-I is essential to understanding its critical interaction with ABCA1 and the molecular mechanisms underlying HDL biogenesis. We therefore examined the structure of lipid-free apoA-I by electron paramagnetic resonance spectroscopy (EPR). Through site directed spin label EPR, we mapped the secondary structure of apoA-I and identified sites of spin coupling as residues 26, 44, 64, 167, 217 and 226. We capitalize on the fact that lipid-free apoA-I self-associates in an anti-parallel manner in solution. We employed these sites of spin coupling to define the central plane in the dimeric apoA-I complex. Applying both the constraints of dipolar coupling with the EPR-derived pattern of solvent accessibility, we assembled the secondary structure into a tertiary context, providing a solution structure for lipid-free apoA-I. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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| 7. |
- Myers, William K., et al.
(författare)
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Double Electron-Electron Resonance Probes Ca2+-Induced Conformational Changes and Dimerization of Recoverin
- 2013
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 52:34, s. 5800-5808
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Tidskriftsartikel (refereegranskat)abstract
- Recoverin a member of the neuronal calcium sensor (NCS) branch of the calmodulin superfamily, is expressed in retinal photoreceptor cells and serves as a calcium sensor in vision. Ca2+-induced conformational changes in recoverin cause extrusion of its covalently attached myristate (termed Ca2+-myristoyl switch) that promotes translocation of recoverin to disk membranes during phototransduction in retinal rod cells. Here we report double electron electron resonance (DEER) experiments on recoverin that probe Ca2+-induced changes in distance as measured by the dipolar coupling between spin-labels strategically positioned at engineered cysteine residues on the protein surface. The DEER distance between nitroxide spin-labels attached at C39 and N120C is 2.5 +/- 0.1 nm for Ca2+-free recoverin and 3.7 +/- 0.1 nm for Ca2+-bound recoverin. An additional DEER distance (5-6 nm) observed for Ca2+-bound recoverin may represent an intermolecular distance between C39 and N120. N-15 NMR relaxation analysis and CW-EPR experiments both confirm that Ca2+-bound recoverin forms a dimer at protein concentrations above 100 mu M, whereas Ca2+-free recoverin is monomeric We propose that Ca2+-induced dimerization of recoverin at the disk membrane surface may play a role in regulating Ca2+-dependent phosphorylation of dimeric rhodopsin. The DEER approach will be useful for elucidating dimeric structures of NCS proteins in general for which Ca2+-induced dimerization is functionally important but not well understood.
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| 8. |
- Nygaard, Eva B., et al.
(författare)
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Structural Modeling and Electron Paramagnetic Resonance Spectroscopy of the Human Na+/H+ Exchanger Isoform 1, NHE1
- 2011
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 286:1, s. 634-648
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Tidskriftsartikel (refereegranskat)abstract
- We previously presented evidence that transmembrane domain (TM) IV and TM X-XI are important for inhibitor binding and ion transport by the human Na+/H+ exchanger, hNHE1 (Pedersen, S. F., King, S. A., Nygaard, E. B., Rigor, R. R., and Cala, P. M. (2007) J. Biol. Chem. 282, 19716-19727). Here, we present a structural model of the transmembrane part of hNHE1 that further supports this conclusion. The hNHE1 model was based on the crystal structure of the Escherichia coli Na+/H+ antiporter, NhaA, and previous cysteine scanning accessibility studies of hNHE1 and was validated by EPR spectroscopy of spin labels in TM IV and TM XI, as well as by functional analysis of hNHE1 mutants. Removal of all endogenous cysteines in hNHE1, introduction of the mutations A173C (TM IV) and/or I461C (TM XI), and expression of the constructs in mammalian cells resulted in functional hNHE1 proteins. The distance between these spin labels was similar to 15 A, confirming that TM IV and TM XI are in close proximity. This distance was decreased both at pH 5.1 and in the presence of the NHE1 inhibitor cariporide. A similar TM IV.TM XI distance and a similar change upon a pH shift were found for the cariporide-insensitive Pleuronectes americanus (pa) NHE1; however, in paNHE1, cariporide had no effect on TM IV.TM XI distance. The central role of the TM IV.TM XI arrangement was confirmed by the partial loss of function upon mutation of Arg(425), which the model predicts stabilizes this arrangement. The data are consistent with a role for TM IV and TM XI rearrangements coincident with ion translocation and inhibitor binding by hNHE1.
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| 9. |
- Oda, Michael N., et al.
(författare)
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The secondary structure of apolipoprotein A-I on 9.6-nm reconstituted high-density lipoprotein determined by EPR spectroscopy
- 2013
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 280:14, s. 3416-3424
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Tidskriftsartikel (refereegranskat)abstract
- ApolipoproteinA-I (ApoA-I) is the major protein component of high-density lipoprotein (HDL), and is critical for maintenance of cholesterol homeostasis. During reverse cholesterol transport, HDL transitions between an array of subclasses, differing in size and composition. This process requires ApoA-I to adapt to changes in the shape of the HDL particle, transiting from an apolipoprotein to a myriad of HDL subclass-specific conformations. Changes in ApoA-I structure cause alterations in HDL-specific enzyme and receptor-binding properties, and thereby direct the HDL particle through the reverse cholesterol transport pathway. In this study, we used site-directed spin label spectroscopy to examine the conformational details of the ApoA-I central domain on HDL. The motional dynamics and accessibility to hydrophobic/hydrophilic relaxation agents of ApoA-I residues99-163 on 9.6-nm reconstituted HDL was analyzed by EPR. In previous analyses, we examined residues6-98 and 164-238 (of ApoA-I's 243 residues), and combining these findings with the current results, we have generated a full-length map of the backbone structure of reconstituted HDL-associated ApoA-I. Remarkably, given that the majority of ApoA-I's length is composed of amphipathic helices, we have identified nonhelical residues, specifically the presence of a -strand (residues149-157). The significance of these nonhelical residues is discussed, along with the other features, in the context of ApoA-I function in contrast to recent models derived by other methods.
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| 10. |
- Petrlova, Jitka, et al.
(författare)
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Molecular crowding impacts the structure of apolipoprotein A-I with potential implications on in vivo metabolism and function
- 2016
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Ingår i: Biopolymers. - : Wiley. - 0006-3525. ; 105:10, s. 683-692
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Tidskriftsartikel (refereegranskat)abstract
- The effect molecular crowding, defined as the volume exclusion exerted by one soluble inert molecule upon another soluble molecule, has on the structure and self-interaction of lipid-free apoA-I were explored. The influence of molecular crowding on lipid-free apoA-I oligomerization and internal dynamics has been analyzed using electron paramagnetic resonance (EPR) spectroscopy measurements of nitroxide spin label at selected positions throughout the protein sequence and at varying concentrations of the crowding agent Ficoll-70. The targeted positions include sites previously shown to be sensitive for detecting intermolecular interaction via spin–spin coupling. Circular dichroism was used to study secondary structural changes in lipid-free apoA-I imposed by increasing concentrations of the crowding agent. Crosslinking and SDS-PAGE gel analysis was employed to further characterize the role molecular crowding plays in inducing apoA-I oligomerization. It was concluded that the dynamic apoA-I structure and oligomeric state was altered in the presence of the crowding agent. It was also found that the C-terminal was slightly more sensitive to molecular crowding. Finally, the data described the region around residue 217 in the C-terminal domain of apoA-I as the most sensitive reporter of the crowding-induced self-association of apoA-I. The implications of this behavior to in vivo functionality are discussed.
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