1
|
Stark T, Lieblein T, Pohland M, Kalden E, Freund P, Zangl R, Grewal R, Heilemann M, Eckert GP, Morgner N, Göbel MW. Peptidomimetics That Inhibit and Partially Reverse the Aggregation of Aβ1–42. Biochemistry 2017; 56:4840-4849. [DOI: 10.1021/acs.biochem.7b00223] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
| | | | | | | | | | | | - Rekha Grewal
- Institute
of Nutritional Sciences, Justus-Liebig-University Giessen, Wilhelmstrasse
20, D-35392 Giessen, Germany
| | | | | | | | | |
Collapse
|
2
|
Significantly shorter Fe-S bond in cytochrome P450-I is consistent with greater reactivity relative to chloroperoxidase. Nat Chem 2015; 7:696-702. [PMID: 26291940 PMCID: PMC4580274 DOI: 10.1038/nchem.2306] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 06/19/2015] [Indexed: 11/16/2022]
Abstract
Cytochrome P450 (P450) and chloroperoxidase (CPO) are thiolate ligated heme proteins that catalyze the activation of carbon hydrogen bonds. The principal intermediate in these reactions is a ferryl radical species called compound I. P450 compound I (P450-I) is significantly more reactive than CPO-I, which only cleaves activated C-H bonds. To provide insight into the differing reactivities of these intermediates, we examined CPO-I and P450-I with variable temperature Mössbauer and X-ray absorption spectroscopies. These measurements indicate that the Fe-S bond is significantly shorter in P450-I than in CPO-I. This difference in Fe-S bond lengths can be understood in terms of variations in hydrogen bonding patterns within the “cys-pocket” (a portion of the proximal helix that encircles the thiolate ligand). Weaker hydrogen bonding in P450-I results in a shorter Fe-S bond, which enables greater electron donation from the axial-thiolate ligand. This observation may in part explain P450's greater propensity for C-H bond activation.
Collapse
|
3
|
Shin YG, Hamm L, Murakami S, Buirst K, Buonarati MH, Cox A, Regal K, Hunt KW, Scearce-Levie K, Watts RJ, Liu X. Qualification and application of a liquid chromatography–tandem mass spectrometric method for the determination of human Aβ1-40 and Aβ1-42 peptides in transgenic mouse plasma using micro-elution solid phase extraction. Arch Pharm Res 2013; 37:636-44. [DOI: 10.1007/s12272-013-0215-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 07/11/2013] [Indexed: 11/29/2022]
|
4
|
Grasso G. The use of mass spectrometry to study amyloid-β peptides. MASS SPECTROMETRY REVIEWS 2011; 30:347-365. [PMID: 21500241 DOI: 10.1002/mas.20281] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/06/2009] [Accepted: 11/06/2009] [Indexed: 05/30/2023]
Abstract
Amyloid-β peptide (Aβ) varies in size from 39 to 43 amino acids and arises from sequential β- and γ-secretase processing of the amyloid precursor protein. Whereas the non-pathological role for Aβ is yet to be established, there is no disputing that Aβ is now widely regarded as central to the development of Alzheimer's disease (AD). The so named "amyloid cascade hypothesis" states that disease progression is the result of an increased Aβ burden in affected areas of the brain. To elucidate the Aβ role in AD, many analytical approaches have been proposed as suitable tools to investigate not only the total Aβ load but also many other issues that are considered crucial for AD, such as: (i) the aggregation state in which Aβ is present; (ii) its interaction with other species or metals; (iii) its ability to induce oxidative stress; and (iv) its degradative pathways. This review provides an insight into the use of mass spectrometry (MS) in the field of Aβ investigation aimed to assess its role in AD. In particular, the different MS-based approaches applied in vitro and in vivo that can provide detailed information on the above-mentioned issues are reviewed. Moreover, the advantages offered by the MS methods over all the other techniques are highlighted, together with the recent developments and uses of combined analytical approaches to detect and characterize Aβ.
Collapse
Affiliation(s)
- Giuseppe Grasso
- Chemistry Department, Università di Catania, Viale Andrea Doria 6, Catania 95125, Italy.
| |
Collapse
|
5
|
Zhang A, Qi W, Good TA, Fernandez EJ. Structural differences between Abeta(1-40) intermediate oligomers and fibrils elucidated by proteolytic fragmentation and hydrogen/deuterium exchange. Biophys J 2009; 96:1091-104. [PMID: 19186145 DOI: 10.1016/j.bpj.2008.10.022] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Accepted: 10/09/2008] [Indexed: 12/24/2022] Open
Abstract
The aggregation of amyloid-beta protein (Abeta) in vivo is a critical pathological event in Alzheimer's disease. Although more and more evidence shows that the intermediate oligomers are the primary neurotoxic species in Alzheimer's disease, the particular structural features responsible for the toxicity of these intermediates are poorly understood. We measured the peptide level solvent accessibility of multiple Abeta(1-40) aggregated states using hydrogen exchange detected by mass spectrometry. A gradual reduction in solvent accessibility, spreading from the C-terminal region to the N-terminal region was observed with ever more aggregated states of Abeta peptide. The observed hydrogen exchange protection begins with reporter peptides 20-34 and 35-40 in low molecular weight oligomers found in fresh samples and culminates with increasing solvent protection of reporter peptide 1-16 in long time aged fibrillar species. The more solvent exposed structure of intermediate oligomers in the N-termini relative to well-developed fibrils provides a novel explanation for the structure-dependent neurotoxicity of soluble oligomers reported previously.
Collapse
Affiliation(s)
- Aming Zhang
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904, USA
| | | | | | | |
Collapse
|
6
|
Qi W, Zhang A, Patel D, Lee S, Harrington JL, Zhao L, Schaefer D, Good TA, Fernandez EJ. Simultaneous monitoring of peptide aggregate distributions, structure, and kinetics using amide hydrogen exchange: application to Abeta(1-40) fibrillogenesis. Biotechnol Bioeng 2008; 100:1214-27. [PMID: 18351682 DOI: 10.1002/bit.21846] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Increasing evidence indicates that soluble aggregates of amyloid beta protein (Abeta) are neurotoxic. However, difficulty in isolating these unstable, dynamic species impedes studies of Abeta and other aggregating peptides and proteins. In this study, hydrogen-deuterium exchange (HX) detected by mass spectrometry (MS) was used to measure Abeta(1-40) aggregate distributions without purification or modification that might alter the aggregate structure or distribution. Different peaks in the mass spectra were assigned to monomer, low molecular weight oligomer, intermediate, and fibril based on HX labeling behavior and complementary assays. After 1 h labeling, the intermediates incorporated approximately ten more deuterons relative to fibrils, indicating a more solvent exposed structure of such intermediates. HX-MS also showed that the intermediate species dissociated much more slowly to monomer than did the very low molecular weight oligomers that were formed at very early times in Abeta aggregation. Atomic force microscopy (AFM) measurements revealed the intermediates were roughly spherical with relatively homogenous diameters of 30-50 nm. Quantitative analysis of the HX mass spectra showed that the amount of intermediate species was correlated with Abeta toxicity patterns reported in a previous study under the same conditions. This study also demonstrates the potential of the HX-MS approach to characterizing complex, multi-component oligomer distributions of aggregating peptides and proteins.
Collapse
Affiliation(s)
- Wei Qi
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Bazoti FN, Bergquist J, Markides KE, Tsarbopoulos A. Noncovalent interaction between amyloid-beta-peptide (1-40) and oleuropein studied by electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:568-75. [PMID: 16503156 DOI: 10.1016/j.jasms.2005.11.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 11/18/2005] [Accepted: 11/24/2005] [Indexed: 05/06/2023]
Abstract
Beta amyloid peptide (Abeta) is the major proteinaceous component of senile plaques formed in Alzheimer's disease (AD) brain. The aggregation of Abeta is associated with neurodegeneration, loss of cognitive ability, and premature death. It has been suggested that oxidative stress and generation of free radical species have implications in the fibrillation of Abeta and its subsequent neurotoxicity. For this reason, it is proposed that antioxidants may offer a protective or therapeutic alternative against amyloidosis. This study is the first report of the formation of the noncovalent complex between Abeta or its oxidized form and the natural derived antioxidant oleuropein (OE) by electrospray ionization mass spectrometry (ESI MS). ESI MS allowed the real time monitoring of the complex formation between Abeta, OE, and variants thereof. Several experimental conditions, such as elevated orifice potential, low pH values, presence of organic modifier, and ligand concentration were examined, to assess the specificity and the stability of the formed noncovalent complexes.
Collapse
Affiliation(s)
- Fotini N Bazoti
- Department of Pharmacy, Laboratory of Pharmaceutical Analysis, University of Patras, Rio, Greece
| | | | | | | |
Collapse
|
8
|
Jablonowska A, Bakun M, Kupniewska-Kozak A, Dadlez M. Alzheimer's Disease Aβ Peptide Fragment 10–30 Forms a Spectrum of Metastable Oligomers with Marked Preference for N to N and C to C Monomer Termini Proximity. J Mol Biol 2004; 344:1037-49. [PMID: 15544811 DOI: 10.1016/j.jmb.2004.09.083] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2004] [Revised: 08/18/2004] [Accepted: 09/22/2004] [Indexed: 12/11/2022]
Abstract
Oligomers of Abeta peptide have been indicated recently as a possible main causative agent of Alzheimer's disease. However, information concerning their structural properties is very limited. Here Abeta oligomers are studied by non-covalent complexes mass spectrometry and disulfide rearrangement. As a model molecule, an Abeta fragment spanning residues 10-30 (Abeta10-30) has been used. This model peptide is known to contain the core region responsible for Abeta aggregation to fibrils. Non-covalent complexes mass spectrometry indicates that, at neutral pH, monomers are accompanied by oligomers up to hexamers of gradually decreasing population. H-2H exchange studies and direct monomer exchange rate measurements with the use of 15N labeled peptides and mass spectrometry show a fast exchange of monomeric units between oligomers. Disulfide exchange studies of cysteine tagged Abeta10-30 and its mutant show proximity of N-N and C-C termini of monomers in oligomers. The presented data underscore a dynamic character for pre-nucleation forms of Abeta, however, with a marked tendency for parallel strand orientation in oligomers.
Collapse
Affiliation(s)
- Agnieszka Jablonowska
- Department of Biophysics, Institute of Biochemistry and Biophysics, PAS, ul. Pawińskiego 5A, 02-106 Warsaw, Poland
| | | | | | | |
Collapse
|
9
|
Rzepecki P, Nagel-Steger L, Feuerstein S, Linne U, Molt O, Zadmard R, Aschermann K, Wehner M, Schrader T, Riesner D. Prevention of Alzheimer's Disease-associated Aβ Aggregation by Rationally Designed Nonpeptidic β-Sheet Ligands. J Biol Chem 2004; 279:47497-505. [PMID: 15322133 DOI: 10.1074/jbc.m405914200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A new concept is introduced for the rational design of beta-sheet ligands, which prevent protein aggregation. Oligomeric acylated aminopyrazoles with a donor-acceptor-donor (DAD) hydrogen bond pattern complementary to that of a beta-sheet efficiently block the solvent-exposed beta-sheet portions in Abeta-(1-40) and thereby prevent formation of insoluble protein aggregates. Density gradient centrifugation revealed that in the initial phase, the size of Abeta aggregates was efficiently kept between the trimeric and 15-meric state, whereas after 5 days an additional high molecular weight fraction appeared. With fluorescence correlation spectroscopy (FCS) exactly those two, i.e. a dimeric aminopyrazole with an oxalyl spacer and a trimeric head-to-tail connected aminopyrazole, of nine similar aminopyrazole ligands were identified as efficient aggregation retardants whose minimum energy conformations showed a perfect complementarity to a beta-sheet. The concentration dependence of the inhibitory effect of a trimeric aminopyrazole derivative allowed an estimation of the dissociation constant in the range of 10(-5) m. Finally, electrospray ionization mass spectrometry (ESI-MS) was used to determine the aggregation kinetics of Abeta-(1-40) in the absence and in the presence of the ligands. From the comparable decrease in Abeta monomer concentration, we conclude that these beta-sheet ligands do not prevent the initial oligomerization of monomeric Abeta but rather block further aggregation of spontaneously formed small oligomers. Together with the results from density gradient centrifugation and fluorescence correlation spectroscopy it is now possible to restrict the approximate size of soluble Abeta aggregates formed in the presence of both inhibitors from 3- to 15-mers.
Collapse
Affiliation(s)
- Petra Rzepecki
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Li A, Fenselau C. Contact regions in the dimer of Alzheimer beta-amyloid domain [1-28] studied by mass spectrometry. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2004; 10:309-316. [PMID: 15103108 DOI: 10.1255/ejms.642] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Information is provided about the amino acid residues in the [1-28] domain of the Alzheimer b- amyloid protein, which participate in interstrand pairing and initiate fibillogenesis. The study was carried out using electrospray ionization on a four sector mass spectrometer, measuring kinetic energy release for a fragmentation process, and modeling the transition state with molecular dynamics calculations. The results eliminate the sequence [11-24] proposed earlier as the central core, and are consistent with, but do not distinguish between, residues [17-28] and [17-23] proposed by others based on biochemical studies.
Collapse
Affiliation(s)
- Aiqun Li
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Catonsville, MD 21250, USA
| | | |
Collapse
|
11
|
Varesio E, Rudaz S, Krause KH, Veuthey JL. Nanoscale liquid chromatography and capillary electrophoresis coupled to electrospray mass spectrometry for the detection of amyloid-beta peptide related to Alzheimer's disease. J Chromatogr A 2002; 974:135-42. [PMID: 12458933 DOI: 10.1016/s0021-9673(02)01241-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Alzeihmer's disease (AD) is a neurodegenerative disorder which is pathologically characterized by the progressive deposit in the brain of a specific form of amyloid, amyloid-beta peptides (Abeta). As the latter circulate in the blood, their quantitation in plasma could allow a simple diagnosis of AD. Abeta are present in different variants, one of which contains 40 amino acid residues (Abeta1-40). In this work, nanoscale liquid chromatography (nano-LC) and capillary electrophoresis (CE) coupled to mass spectrometry (MS) were compared to determine the most appropriate technique for reaching the usual Abeta1-40 concentration in plasma or serum. Both a 50 microm I.D. CE capillary and a 75 microm I.D. nano-LC column were coupled to a single quadrupole mass spectrometer with a sheath-liquid electrospray (ESI) interface or a homemade nanospray interface, respectively. Capillary zone electrophoresis is a powerful separation technique, but its low sensitivity limits its use in the analysis of biological matrices. However, a column-switching set-up with a precolumn of 1 mm x 300 microm I.D. packed with a C18 PepMap (3 microm) stationary phase and a nanocolumn of 15 cm x 75 microm I.D. packed with the same stationary phase was found to be a successful technique which allowed detection of Abeta1-40 at the ng ml(-1) level (a few hundred femtomoles injected) because of its higher sample loading capability.
Collapse
Affiliation(s)
- Emmanuel Varesio
- Laboratory of Pharmaceutical Analytical Chemistry, School of Pharmacy, University of Geneva, Boulevard d'Yvoy 20, 1211 Geneva 4, Switzerland
| | | | | | | |
Collapse
|
12
|
Palmblad M, Westlind-Danielsson A, Bergquist J. Oxidation of methionine 35 attenuates formation of amyloid beta -peptide 1-40 oligomers. J Biol Chem 2002; 277:19506-10. [PMID: 11912198 DOI: 10.1074/jbc.m112218200] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Amyloid plaques formed by aggregation of the amyloid beta-peptide (Abeta) are an intrinsic component of Alzheimer disease pathogenesis. It has been suggested that oxidation of methionine 35 in Abeta has implications for Alzheimer disease, and it has been shown that oxidation of Met-35 significantly inhibits aggregation in vitro. In this study, the aggregational properties of Abeta-(1-40) before and after Met-35 oxidation were investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The results show that Abeta-(1-40)Met-35(O) trimer and tetramer formation is significantly attenuated as compared with Abeta-(1-40). This suggests that oxidation of Met-35 inhibits a conformational switch in Abeta-(1-40) necessary for trimer but not dimer formation. Random incorporation of Abeta-(1-40) and Abeta-(1-40)Met-35(O) in homo- and heterooligomers could also be observed. This is the first report of an early rate-limiting step in Abeta-(1-40) aggregation. Slowing of the fibrillization process at this early step is likely to support prolonged solubility and clearance of Abeta from brain and may reduce disease progression.
Collapse
Affiliation(s)
- Magnus Palmblad
- Division of Ion Physics, The Angström Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
| | | | | |
Collapse
|
13
|
Skribanek Z, Baláspiri L, Mák M. Interaction between synthetic amyloid-beta-peptide (1-40) and its aggregation inhibitors studied by electrospray ionization mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:1226-1229. [PMID: 11747119 DOI: 10.1002/jms.243] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It is generally postulated that amyloid-beta-peptides play a central role in the progressive neurodegeneration observed in Alzheimer's disease. Important pathological properties of these peptides, such as neurotoxicity and resistance to proteolytic degradation, depend on the ability of amyloid-beta-peptides to form beta-sheet structures and/or amyloid fibrils. Amyloid-beta-peptides are known to aggregate spontaneously in vitro with the formation of amyloid fibrils. The intervention on the amyloid-beta-peptides aggregation process can be envisaged as an approach to stopping or slowing the progression of Alzheimer's disease. In the last few years a number of small molecules have been reported to interfere with the in vitro aggregation of amyloid-beta-peptides. Melatonin, a hormone recently found to protect neurons against amyloid-beta-peptide toxicity, interacts with amyloid-beta-peptide (1-40) and amyloid-beta-peptide (1-42) and inhibits the progressive formation of beta-sheet and/or amyloid fibrils. These interactions between melatonin and the amyloid peptides have been demonstrated by circular dichroism (CD) and electron microscopy for amyloid-beta-peptide (1-40) and amyloid-beta-peptide (1-42) and by nuclear magnetic resonance (NMR) spectroscopy for amyloid-beta-peptide (1-40). Our electrospray ionization mass spectrometric (ESI-MS) studies also proved that there is a hydrophobic interaction between amyloid-beta-peptide (1-40) and melatonin and the proteolytic investigations suggested that the interaction took place on the 29-40 amyloid-beta-peptide segment. The wide-ranging application of these results would provide further information and help in biological research.
Collapse
Affiliation(s)
- Z Skribanek
- Gedeon Richter Ltd, P.O. Box 27, H-1475 Budapest 10, Hungary.
| | | | | |
Collapse
|
14
|
DeVoe D, Dalleck L. Reliability and validity of the tritrac-R3D accelerometer during backpacking: a case study. Percept Mot Skills 2001; 93:37-46. [PMID: 11693704 DOI: 10.2466/pms.2001.93.1.37] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This study investigated the utility of the Tritrac-R3D accelerometer as a reliable and valid instrument in the quantification of physical activity while backpacking in the field and to evaluate heart-rate responses and oxygen consumption to assess the feasibility of using the Tritrac-R3D to estimate caloric expenditure. Two 7-day backpacking expeditions were conducted in two consecutive years by a single subject at Grand Canyon National Park, Arizona. The average hiking heart rate ranged front 60% to 77% HRmax during the expeditions. The average rate of estimated caloric cost ranged from 6.8 to 11.7 kcals x min.(-1) (equivalent to 408 to 702 kcals x hr.(-1)), indicating a relatively moderate to high level of exertion. The Tritrac had adequate consistency and reliability in the field between the two expeditions in recorded activity counts. The Tritrac underestimated caloric expenditure during backpacking with changes in terrain, and hiking speed contributed to even greater disparity in accuracy.
Collapse
Affiliation(s)
- D DeVoe
- Department of Health and Exercise Science, Colorado State University, Fort Collins 80523, USA.
| | | |
Collapse
|
15
|
DEVOE DALE. RELIABILITY AND VALIDITY OF THE TRITRAC-R3D ACCELEROMETER DURING BACKPACKING: A CASE STUDY. Percept Mot Skills 2001. [DOI: 10.2466/pms.93.5.37-46] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
16
|
Chrambach A, Chrambach A, Brining SK. Gel electrophoretic distinction between Congo Red nonreactive beta-amyloid (1-42) and beta-amyloid (1-40). Electrophoresis 2000; 21:760-1. [PMID: 10733218 DOI: 10.1002/(sici)1522-2683(20000301)21:4<760::aid-elps760>3.0.co;2-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Congo-Red nonreactive beta-amyloid (1-42) exhibits in gel electrophoresis (pH 8.82, 0.01 M ionic strength, 2 degree C) a surface charge density larger than that of the corresponding peptide of length (1-40), and a size indistinguishable from that of (1-40).
Collapse
Affiliation(s)
- A Chrambach
- Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1580, USA.
| | | | | |
Collapse
|
17
|
Abstract
The in vitro toxicity of synthetic beta-amyloid (1-40) correlates with its binding to Congo red (CR). Potentially, therefore, CR binding to the beta-amyloid containing neuritic plaques in Alzheimer's disease could be used diagnostically. Using polyacrylamide under nondenaturing conditions, the present study shows that both CR binding and nonbinding synthetic beta-amyloid exhibits multiple charge-isomeric and size-isomeric species. The CR binding species exhibit values of free electrophoretic mobility, related to the surface charge density of the protein, which are less than those of the CR non-binding species within 95% confidence limits. Since surface net charge and solubility are correlated, the decreased solubility of the CR binding species may be responsible for the relative abundance and CR binding of beta-amyloid in the neuritic plaques of Alzheimer patients.
Collapse
Affiliation(s)
- S K Brining
- Section on Macromolecular Analysis, Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1580, USA.
| | | | | | | |
Collapse
|
18
|
Schalinske KL, Chen OS, Eisenstein RS. Iron differentially stimulates translation of mitochondrial aconitase and ferritin mRNAs in mammalian cells. Implications for iron regulatory proteins as regulators of mitochondrial citrate utilization. J Biol Chem 1998; 273:3740-6. [PMID: 9452506 DOI: 10.1074/jbc.273.6.3740] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Utilization of mRNAs containing iron-responsive elements (IREs) is modulated by iron-regulated RNA-binding proteins (iron regulatory proteins). We examine herein whether iron differentially affects translation of ferritin and mitochondrial aconitase (m-Acon) mRNAs because they contain a similar but not identical IRE in their 5'-untranslated regions. First, we demonstrate that m-Acon synthesis is iron-regulated in mammalian cells. In HL-60 cells, hemin (an iron source) stimulated m-Acon synthesis 3-fold after 4 h compared with cells treated with an iron chelator (Desferal). Furthermore, hemin stimulated m-Acon synthesis 2-4-fold in several cell lines. Second, we show that iron modulates the polysomal association of m-Acon mRNA. We observed m-Acon mRNA in both ribonucleoprotein and polyribosomal fractions of HL-60 cells. Hemin significantly increased the polyribosomal association and decreased the ribonucleoprotein abundance of m-Acon mRNA in HL-60 cells. Third, our results indicate that iron differentially regulates translation of m-Acon and ferritin mRNAs. A dose response to hemin in HL-60 cells elicited a 2-2.4-fold increase in m-Acon synthesis within 5 h compared with untreated cells, whereas ferritin synthesis was stimulated 20-100-fold. We conclude that iron modulates m-Acon synthesis at the translational level and that iron regulatory proteins appear to differentially affect translation of IRE-containing mRNAs.
Collapse
Affiliation(s)
- K L Schalinske
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA
| | | | | |
Collapse
|