Advertisement
J. Lipid Res.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Originally published In Press as doi:10.1194/jlr.C500022-JLR200 on January 23, 2006

Papers In Press, published online ahead of print April 1, 2006
J. Lipid Res., doi:10.1194/jlr.C500022-JLR200
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Supplemental Data
Right arrow All Versions of this Article:
C500022-JLR200v1
47/4/755    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wilson, L. M.
Right arrow Articles by Howlett, G. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wilson, L. M.
Right arrow Articles by Howlett, G. J.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

Journal of Lipid Research, Vol. 47, 755-760, April 2006
Copyright © 2006 by American Society for Biochemistry and Molecular Biology

High density lipoproteins bind Aß and apolipoprotein C-II amyloid fibrilsboxs

Leanne M. Wilson*, Chi L. L. Pham*, Alicia J. Jenkins{dagger}, John D. Wade§, Andrew F. Hill*,**, Matthew A. Perugini* and Geoffrey J. Howlett1,*

* Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
{dagger} Department of Medicine, University of Melbourne, St. Vincent's Hospital, Fitzroy, Victoria 3065, Australia
§ Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria 3010, Australia
** Department of Pathology, University of Melbourne, Parkville, Victoria 3010, Australia, and Mental Health Research Institute of Victoria, Parkville, Victoria 3052, Australia

boxs The online version of this article (available at http://www.jlr.org) contains an additional table. Back

Published, JLR Papers in Press, January 23, 2006.

1 To whom correspondence should be addressed. e-mail: ghowlett{at}unimelb.edu.au


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Disease-associated amyloid deposits contain both fibrillar and nonfibrillar components. The majority of these amyloid components originate or coexist in the bloodstream. To understand the nature of the interaction between the nonfibrillar and fibrillar components, we have developed a centrifugation method to isolate fibril binding proteins from human serum. Amyloid fibrils composed of either Aß peptide or apolipoprotein C-II (apoC-II) cosedimented with specific serum proteins. Gel electrophoresis, mass spectrometry peptide fingerprinting, and Western analysis identified the major binding species as proteins found in HDL particles, including apoA-I, apoA-II, apoE, clusterin, and serum amyloid A. Sedimentation analysis showed that purified human HDL and recombinant apoA-I lipid particles bound directly to Aß and apoC-II amyloid fibrils. These studies reveal a novel function of HDL that may contribute to the well-established protective effect of this lipoprotein class in heart disease.

Supplementary key words amyloidosis • apolipoprotein A-I • atherosclerosis • human serum • lipid • nonfibrillar component • protein aggregation • protein folding

Abbreviations: apoC-II, apolipoprotein C-II; SAA, serum amyloid A; SAP, serum amyloid P component


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Amyloid deposits are associated with a large number of debilitating disorders, including Alzheimer's and Parkinson's diseases, transmissible spongiform encephalopathies, type II diabetes, and systemic amyloidoses (1). More than 20 different polypeptides and proteins form amyloid fibrils in vivo; the majority of these are derived from the bloodstream and are deposited extracellularly (2). Amyloid fibrils are universally characterized by their interaction with the dyes thioflavin T and Congo Red and by their cross-ß structure, as revealed by X-ray diffraction. Recent work has focused on the molecular structure of amyloid fibrils, with a particular focus on the organization of the cross-ß sheets formed by the Aß peptide (3) and the X-ray crystallography of amyloid fibrils composed of small peptides (4, 5).

Less attention has been focused on the nonfibrillar components of amyloid deposits, such as serum amyloid P component (SAP), apolipoprotein E (apoE), clusterin (apoJ), and glycoproteins such as laminin and agrin (6). Although several potential roles for these molecules in the deposition of amyloid plaques have been proposed, conflicting data have confused their precise function. For example, studies with the Aß peptide show that apoE and SAP promote Aß fibril formation (7, 8), whereas other work shows that apoE and SAP inhibit Aß fibril formation (9, 10). Nonfibrillar components may also affect the stability and interaction within amyloid deposits. SAP protects serum amyloid A (SAA) and Aß amyloid fibrils from proteolysis by trypsin, chymotrypsin, and pronase (11), whereas apoE and SAP also mediate the self-association and tangling of apoC-II amyloid fibrils (12). Another potential role for nonfibrillar components such as SAP is to affect the recognition of toxic oligomeric amyloid precursors (13) by the innate immune response. Amyloid deposits are often localized to specific tissues, with peptides accumulating in restricted locations (1). The Aß peptide, for example, is found in a variety of tissues but is deposited as fibrils only in synapses and the basement membranes of brain blood vessels (14). Such specificity suggests that there are factors, other than the nature of the fibril-forming proteins, that control amyloid deposition.

Because the majority of nonfibrillar components in amyloid deposits are derived from, or at least coexist in, the bloodstream, we initiated a search for serum proteins that bind amyloid fibrils. Amyloid fibrils composed of Aß peptide, {alpha}-synuclein, and apoC-II were chosen for this study. Aß amyloid fibrils are formed from the Aß peptide, which is cleaved from the amyloid precursor protein and deposited in plaques associated with neuronal dysfunction in Alzheimer's disease (15). {alpha}-Synuclein is the major component of Lewy bodies, the fibrillar intraneuronal inclusions associated with Parkinson's disease. Soluble {alpha}-synuclein has class A amphipathic helices and binds lipid in a similar manner to apolipoproteins (16). Human apoC-II is a component of very low density lipoproteins, in which it plays an essential role in activating lipoprotein lipase during lipid metabolism. ApoC-II readily aggregates in lipid-free conditions to form homogeneous amyloid fibrils (17). ApoC-II aggregates are present in human atherosclerotic plaques, and apoC-II fibrils initiate macrophage inflammatory responses (18). Our results identify a subset of serum proteins that bind Aß and apoC-II amyloid fibrils.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Materials
Aß peptide was synthesized and {alpha}-synuclein and apoC-II were expressed and purified as described previously (17, 19, 20). Amyloid fibrils were prepared by incubation in phosphate buffer [100 mM sodium phosphate, 0.1% (w/v) sodium azide, pH 7.4] using final concentrations of 0.4 mg/ml (Aß), 3 mg/ml ({alpha}-synuclein), and 0.4 mg/ml (apoC-II) at 37°C with shaking for 5 days for Aß and {alpha}-synuclein (1,400 rpm Thermomixer; Eppendorf, Hamburg, Germany) and at room temperature without shaking for 5 days for apoC-II. The presence of amyloid fibrils was confirmed using the dye thioflavin T, as described previously (17). Initial studies were conducted with one fasted serum sample from a healthy volunteer. Serum samples with increased SAA levels were provided by consenting patients from a previous study conducted at St. Vincent's Hospital, Melbourne (21). SAA levels were determined by immunonephelometry (BN-II nephelometer; Dade-Behring, Marburg, Germany). Human HDL, rabbit anti-human apoA-I antibodies, goat anti-human apoA-II antibodies, and goat anti-rabbit peroxidase-conjugated secondary antibodies were purchased from Calbiochem (La Jolla, CA). Human apoA-I was purchased from Sigma (St. Louis, MO). Goat anti-human apoE antibodies, goat anti-human clusterin antibodies (apoJ), and rabbit anti-goat horseradish peroxidase secondary antibodies were purchased from Chemicon (Temecula, CA). Reconstituted HDL (22) was kindly provided by CSL Bioplasma (Melbourne, Australia).

Binding of serum proteins to amyloid fibrils
Human serum diluted 10-fold in phosphate buffer (350 µl) or purified lipoprotein (300 µl, 0.1 mg/ml) was mixed, by brief vortexing, with amyloid fibrils (100 µl) or phosphate buffer (100 µl) at room temperature and immediately layered on top of 20% sucrose (500 µl) in phosphate buffer in a 1 ml polycarbonate ultracentrifuge tube. The samples were then centrifuged in a TL100 benchtop ultracentrifuge (Beckman Coulter, Fullerton, CA) at 100,000 rpm (355,000 g) for 10 min at 20°C. The supernatants of both serum-alone controls and serum amyloid fibril mixtures were removed, and the pellets were gently washed twice with 500 µl of phosphate buffer and resuspended in gel-loading buffer (60 µl). The samples (30 µl) were analyzed using 16% Tris-Tricine SDS-PAGE gels or Tris-glycine 4–20% gradient SDS-PAGE gels (Gradipore) and stained with Coomassie Brilliant Blue R250 or colloidal silver (Plus One silver stain; Amersham, Piscataway, NJ), as indicated.

Mass spectrometry
Gel slices corresponding to specific protein bands were rinsed (25 mM ammonium bicarbonate) and incubated in 10 mM dithiothreitol for 1 h at 56°C, then alkylated with 55 mM iodoacetamide for 45 min in the dark. Gel pieces were dried and incubated in trypsin (Promega, Madison, WI; 20 µl of 12.5 ng/µl in 25 mM ammonium bicarbonate) at 37°C overnight. The supernatant was collected and mixed in a 5:2 ratio with {alpha}-cyano-4-hydroxycinnamic acid in 50% acetonitrile and 1% trifluoroacetic acid for mass spectrometry analysis. The instrument used was a Voyager-DE STR Perkin-Elmer Applied Biosystems (Foster City, CA) time-of-flight mass spectrometer equipped with a 337 nm N2 laser matrix-assisted laser desorption ionization source. Parent ions were measured in reflector and positive modes. Mass spectrometry fingerprint spectra were analyzed using MS-FIT (http://prospector.ucsf.edu/).

Western analysis
Samples were transferred from SDS-PAGE gels to nitrocellulose membranes by electroblotting. The membranes were incubated in blocking buffer (5% skim milk 10 mM Tris, 150 mM sodium chloride, and 0.01% Tween 20, pH 7.4) at 4°C overnight, followed by 1 h at room temperature in a 1:1,000 dilution of primary antibody in blocking buffer, three washes in 10 mM Tris, 150 mM sodium chloride, and 0.01% Tween 20, pH 7.4, and then 1 h at room temperature in secondary antibody, diluted 1:10,000. Bound antibody was visualized using insoluble tetramethylbenzidine.

Analytical ultracentrifugation
Sedimentation velocity analysis was performed using a Beckman model XL-A analytical ultracentrifuge, as described previously (12). ApoC-II amyloid fibrils and HDL samples were centrifuged at 7,000 rpm (4,000 g), with radial absorbance data acquired at 280 nm. Data were fitted to a least-squares g*(s) distribution model, ls-g*(s), using the program SEDFIT (23).

Electron microscopy
Samples were applied to freshly glow-discharged carbon-coated copper grids, negatively stained with 2% (w/v) potassium phosphotungstate, pH 6.8, and examined using a FEI Tecnai 12 transmission electron microscope equipped with a Soft Imaging System MegaView III charge-coupled device camera. Micrographs were recorded at nominal magnifications of 150,000x.

Phospholipid assay
Total phospholipid levels of pellet fractions were measured using the phospholipid C assay for the determination of phospholipids in serum (Wako, Osaka, Japan). Total pellet fractions (60 µl, resuspended in phosphate buffer) of apoC-II amyloid fibrils spun alone, apoC-II amyloid fibrils spun in the presence of serum, and serum spun alone were analyzed.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Mixtures of human serum and preformed {alpha}-synuclein, Aß peptide, or apoC-II amyloid fibrils were centrifuged through a 20% sucrose solution, and the pellet fraction was analyzed by SDS-PAGE. Serum proteins that do not interact with amyloid fibrils remain in the supernatant fraction (data not shown). Figure 1A shows the results obtained, together with control samples containing serum centrifuged alone. Under the conditions used, there was no specific binding of serum proteins to {alpha}-synuclein fibrils. In contrast, Aß and apoC-II fibrils bound and sedimented with a selective and common set of serum proteins. There was a small subset of proteins from serum that sedimented through the 20% sucrose in the absence of amyloid fibrils; these protein bands were not analyzed further. Similar results were obtained using human plasma (data not shown). The results shown in Fig. 1A were sensitive to the amount of serum present in the initial mixture. Serum dilutions of 1:10 and 1:50 yielded different amounts of protein in the pellet fraction (Fig. 1B).


Figure 1
View larger version (37K):
[in this window]
[in a new window]
  		Fig. 1. Analysis of the binding of serum proteins to amyloid fibrils. All samples were centrifuged through 20% sucrose for 10 min at 355,000 g. Samples centrifuged in the presence of amyloid fibrils are marked A, whereas control serum samples centrifuged alone are also shown (C). A: Pellet fractions from a serum sample centrifuged in the presence of amyloid fibrils composed of {alpha}-synuclein ({alpha}-syn), Aß, and apolipoprotein C-II (apoC-II) were analyzed by 4–20% Tris-glycine gradient SDS-PAGE and silver staining. Lowercase letters identify specific bands. Bands a, b, and c indicate the position of Aß, apoC-II, and {alpha}-synuclein, respectively. Bands d–g were analyzed further (Table 1). The positions of molecular mass makers in kDa are shown. B: Pellet fraction serum (diluted 1:10 and 1:50) centrifuged in the presence of amyloid fibrils composed of apoC-II and analyzed by 4–20% Tris-glycine gradient SDS-PAGE and silver staining. C: Western analysis of amyloid binding proteins from serum. Pellet fractions were analyzed using peroxidase conjugate antibodies to apoA-I, apoA-II, apoE, and apoJ (clusterin), as indicated. The bands correspond to known mobilities of apoA-I, apoA-II, apoE, and apoJ. D: Analysis of apoC-II amyloid binding proteins in different serum samples (1–4). Each different serum sample was mixed with apoC-II amyloid fibrils and centrifuged, and the pellet fraction was analyzed using 16% Tris-Tricine SDS-PAGE with Coomassie Brilliant Blue staining. The band labeled a corresponds to apoC-II, and the band labeled i was analyzed further (Table 1). Serum amyloid A (SAA) levels are shown for each sample in mg/l. E: Total phospholipid content of the pellet fractions of apoC-II amyloid binding samples from human serum. Pellet fractions of apoC-II amyloid alone, apoC-II and serum, and serum alone were centrifuged and analyzed for total phospholipid. Error bars indicate SEM (n = 3).

 

View this table:
[in this window]
[in a new window]
  		TABLE 1. Identification of amyloid binding proteins

 
The identities of the serum proteins that interact with Aß and apoC-II amyloid fibrils were investigated using mass spectrometry (Table 1 ) (see also supplementary data). Bands labeled d–g in Fig. 1 were identified as apoA-I, apoE, apoA-IV, and clusterin, respectively. These identifications were based on the measured masses of between 6 and 21 tryptic peptides derived from the individual bands. The identifications were made using MS-FIT and searching the SwissProt database; in each case, there was one predominant match to a human serum protein that was consistent with the known mobility of the denatured protein using SDS-PAGE. The proteins identified are all components of serum HDL. Western analysis confirmed the identity of apoA-I and apoE as amyloid binding proteins (Fig. 1C). In addition, the binding of apoA-II, another HDL protein component, which was not initially identified by mass peptide fingerprinting, was also demonstrated by Western analysis. Clusterin was also identified in the apoC-II amyloid serum pellet fraction by Western analysis and to a lesser extent in the serum-alone pellet fraction.

During inflammation, there is a large increase in SAA levels and a corresponding increase in the levels of SAA in HDL (24). We analyzed four different serum samples with SAA levels of 103, 109, 133, and 1,000 mg/l (Fig. 1D). SDS-PAGE analysis of the pellet fraction for the sample with the highest SAA level revealed an additional band (i) at a mobility corresponding to SAA (lane 2). Mass spectrometry confirmed this band as SAA (Table 1). Control serum-alone spins did not show the presence of SAA in any of the pellet fractions.

Figure 1E shows the phospholipid content of the pellet fractions. Samples of apoC-II amyloid fibrils alone or serum alone contained negligible phospholipid levels. In contrast, phospholipid levels were much higher in the pellet fractions for apoC-II amyloid fibrils centrifuged in the presence of serum. Comparisons with serum samples before centrifugation (data not shown) suggest that ~3% of serum phospholipid sediments with apoC-II amyloid fibrils.

The sucrose sedimentation method was used to investigate the direct interaction of HDL with apoC-II amyloid fibrils. Sedimentation experiments with purified human HDL demonstrate that HDL binds to apoC-II amyloid fibrils, as shown by protein bands at 28 and 18 kDa corresponding to apoA-I and dimeric apoA-II (Fig. 2A ). These protein bands were not observed in the HDL-alone control sample. Under the conditions used (50 µg/ml HDL, 100 µg/ml apoC-II fibrils), a significant amount of HDL remained in the supernatant. The interaction of reconstituted HDL, composed of apoA-I combined with soy phospholipid, with apoC-II amyloid fibrils was also investigated. The results shown in Fig. 2A demonstrate the presence of a protein band in the pellet fraction corresponding to the mobility of apoA-I that was not present in the sample containing reconstituted HDL alone. Additional experiments showed that lipid-free purified human apoA-I did not bind amyloid fibrils under these conditions (Fig. 2A). Electron micrographs of the apoC-II amyloid fibril control pellet (Fig. 2B) and the pellet fraction for apoC-II fibrils sedimented in the presence of HDL (Fig. 2C) show particles both free in solution and bound to the fibrils when HDL is present. The average size of the particles associated with the fibrils was 10.8 nm, consistent with the size of intact HDL particles.


Figure 2
View larger version (51K):
[in this window]
[in a new window]
  		Fig. 2. Interaction of apoC-II amyloid fibrils with HDL and reconstituted apoA-I lipid particles (rHDL). A: Samples were centrifuged through 20% sucrose for 10 min at 355,000 g, analyzed by 16% Tris-Tricine SDS-PAGE, and stained with Coomassie Brilliant Blue. The positions of molecular mass makers in kDa are shown. Lanes labeled HDL: Pellet fractions of apoC-II amyloid fibrils centrifuged in the presence of human HDL (50 µg/ml) (A) and the control human HDL sample (50 µg/ml) (C) sedimented alone. The supernatant fraction for the human HDL and apoC-II sample is shown (S/N). Lanes labeled rHDL: Pellet fractions of rHDL (50 µg/ml) centrifuged in the presence of apoC-II amyloid fibrils (A) and the control (C) rHDL sedimented alone. Lanes labeled apoA-I: Pellet fractions of human apoA-I (40 µg/ml) centrifuged in the presence of apoC-II amyloid fibrils (A) and the control (C) apoA-I sedimented alone. B: Transmission electron micrograph of apoC-II amyloid fibrils (0.4 mg/ml; 100 mM sodium phosphate, pH 7.4, 0.1% NaN3) centrifuged alone. C: Transmission electron micrograph of apoC-II amyloid fibrils centrifuged in the presence of human HDL (50 µg/ml). Bars = 100 nm.

 
We investigated whether the binding of purified HDL to apoC-II fibrils produced a change in the rate of fibril sedimentation (Fig. 3 ). HDL causes a concentration-dependent increase in the average sedimentation rate of apoC-II fibrils, as observed previously for apoE and SAP and attributed to fibril-fibril interactions and tangling (12).


Figure 3
View larger version (11K):
[in this window]
[in a new window]
  		Fig. 3. Sedimentation velocity analysis of apoC-II amyloid fibrils. ApoC-II amyloid fibrils and HDL were centrifuged at 4,000 g in an analytical ultracentrifuge. Continuous sedimentation coefficient distributions [ls-g*(s)] are shown for apoC-II amyloid fibrils (solid line) and apoC-II amyloid fibrils in the presence of HDL at concentrations of 0.18 mg/ml (dashed line) and 0.32 mg/ml (dashed-dotted line).

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
This study examines the direct interaction of serum proteins with preformed amyloid fibrils. The results shown in Fig. 1 demonstrate that HDL is a major species in human serum that binds amyloid fibrils composed of Aß and apoC-II. In contrast, serum proteins did not bind {alpha}-synuclein fibrils. {alpha}-Synuclein amyloid fibrils are deposited intracellularly, which may account for the difference in binding properties. Although the results shown in Fig. 1 indicate that HDL apolipoproteins are the principal low molecular weight serum proteins that bind Aß and apoC-II amyloid fibrils, it is important to note that several unresolved high molecular weight species also bind. We cannot preclude the possibility that apoB, a high molecular weight protein marker of LDL and VLDL, is one of these proteins. An unexpected finding of this study was the lack of evidence for an interaction between SAP and either Aß or apoC-II fibrils. SAP is a nonfibrillar component of amyloid deposits and is present in human serum at a concentration of ~40 µg/ml (25). Western analysis also failed to detect the binding of SAP to the fibrils, although SAP was detected in serum (data not shown). Possible explanations for the lack of an interaction are that SAP is complexed to other components in serum or that HDL competes more efficiently for fibril binding.

The protein composition of HDL changes during inflammation (24), and the results shown in Fig. 1D indicate that these changes are reflected in the amyloid binding protein profiles. The identification of SAA as an amyloid binding protein suggests that the protein composition of HDL during inflammation could affect the metabolism of the amyloid fibrils. Moreover, these results suggest that the composition of HDL in serum determines the amyloid binding protein profile. This implies that HDL binds as a single entity rather than as the binding of individual components. Phospholipid assays demonstrate the presence of lipid in the pellet fractions for apoC-II amyloid serum spins, supporting the conclusion that whole HDL particles are associated with amyloid fibrils, not just the protein components. We cannot discount the possibility that there is some disruption of the HDL particles on association with the amyloid fibrils. However, the presence of such an extensive list of HDL protein components in the pellet fraction and the electron micrographs of pellet fractions showing particles corresponding to the expected size of HDL (10 nm in diameter) suggest that relatively intact HDL particles sediment with amyloid fibrils. The question arises of what determines the recognition of amyloid fibrils by HDL. Our results show that reconstituted apoA-I lipid particles, but not lipid-free apoA-I, bind amyloid fibrils, indicating either that lipid bound apoA-I or lipid is sufficient to mediate this binding.

Previous studies have demonstrated interactions between HDL components and soluble amyloidogenic proteins. Soluble Aß peptide interacts with HDL via apoA-I, apoA-II, apoE, and apoJ (26), whereas soluble transthyretin, another amyloidogenic protein, interacts with HDL via apoA-I (27). Immobilized Aß peptide binds clusterin (apoJ) from plasma and cerebrospinal fluid (28), and soluble Aß in human serum associates with HDL and VLDL lipoprotein particles (29). Purified apoA-I interacts with the Aß peptide and inhibits fibril formation (30). The ability of HDL components to interact with monomeric and fibrillar proteins may control the kinetics of formation and equilibrium between the soluble and fibrillar disease forms of amyloidogenic proteins.

HDL has been widely studied as a negative risk factor for heart disease. Most attention has focused on the proposed role of HDL in reverse cholesterol transport (31). Support for this role is provided by studies with transgenic animals, in which a loss of the HDL receptor responsible for reverse cholesterol transport, scavenger receptor class B type I, leads to increased atherosclerosis (32). However, despite extensive studies, it has not been possible to unequivocally demonstrate a link between reverse cholesterol transport and the development of heart disease. Recent studies demonstrate that HDL therapy using HDL and reconstituted HDL can limit the progression of atherosclerosis in both animal and human trials (33–35). This study identifies a novel function for HDL: the specific binding of HDL to amyloid fibrils composed of apoC-II and Aß. Recently, it was shown that amyloid fibrils composed of Aß or apoC-II interact with the CD36 receptor of macrophages (18, 36) and promote cell signaling pathways, an early event in the conversion of macrophages to foam cells and the development of atherosclerosis. Lipoproteins are widely observed in atherosclerotic plaques, and apoA-I, apoB, and apoE are part of the response-to-retention hypothesis, which proposes that retained plasma lipoproteins promote foam cell formation (37). The binding of HDL to amyloid fibrils may inhibit macrophage activation via the CD36 receptor, leading to protection from foam cell formation and heart disease. This ability of HDL to bind to amyloid fibrils may also influence the rate of formation, stability, and tangling of amyloid fibrils. Therefore, these effects may contribute to the well-established protective role of HDL in the development of heart disease.


   ACKNOWLEDGMENTS
 
The authors are grateful to Dr. S. J. Richardson for valuable suggestions during the preparation of the manuscript. This work was supported by the Australian Research Council (Grant DP0449510) and the National Health and Medical Research Council (Grant 350229).

Submitted on September 30, 2005
Revised on November 21, 2005 and in re-revised form December 21, 2005


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
  1. Selkoe, D. J. 2003. Folding proteins in fatal ways. Nature. 426: 900–904.[CrossRef][Medline]

  2. Westermark, P., M. D. Benson, J. N. Buxbaum, A. S. Cohen, B. Frangione, S. Ikeda, C. L. Masters, G. Merlini, M. J. Saraiva, and J. D. Sipe. 2005. Amyloid: toward terminology clarification. Report from the Nomenclature Committee of the International Society of Amyloidosis. Amyloid. 12: 1–4.[Medline]

  3. Tycko, R. 2004. Progress towards a molecular-level structural understanding of amyloid fibrils. Curr. Opin. Struct. Biol. 14: 96–103.[CrossRef][Medline]

  4. Makin, O. S., E. Atkins, P. Sikorski, J. Johansson, and L. C. Serpell. 2005. Molecular basis for amyloid fibril formation and stability. Proc. Natl. Acad. Sci. USA. 102: 315–320.[Abstract/Free Full Text]

  5. Nelson, R., M. R. Sawaya, M. Balbirnie, A. O. Madsen, C. Riekel, R. Grothe, and D. Eisenberg. 2005. Structure of the cross-beta spine of amyloid-like fibrils. Nature. 435: 773–778.[CrossRef][Medline]

  6. Alexandrescu, A. T. 2005. Amyloid accomplices and enforcers. Protein Sci. 14: 1–12.[CrossRef][Medline]

  7. Castano, E. M., F. Prelli, T. Wisniewski, A. Golabek, R. A. Kumar, C. Soto, and B. Frangione. 1995. Fibrillogenesis in Alzheimer's disease of amyloid beta peptides and apolipoprotein E. Biochem. J. 306: 599–604.[Medline]

  8. Hamazaki, H. 1995. Amyloid P component promotes aggregation of Alzheimer's beta-amyloid peptide. Biochem. Biophys. Res. Commun. 211: 349–353.[CrossRef][Medline]

  9. Evans, K. C., E. P. Berger, C. G. Cho, K. H. Weisgraber, and P. T. Lansbury, Jr. 1995. Apolipoprotein E is a kinetic but not a thermodynamic inhibitor of amyloid formation: implications for the pathogenesis and treatment of Alzheimer disease. Proc. Natl. Acad. Sci. USA. 92: 763–767.[Abstract/Free Full Text]

  10. Janciauskiene, S., P. Garcia de Frutos, E. Carlemalm, B. Dahlback, and S. Eriksson. 1995. Inhibition of Alzheimer beta-peptide fibril formation by serum amyloid P component. J. Biol. Chem. 270: 26041–26044.[Abstract/Free Full Text]

  11. Tennent, G. A., L. B. Lovat, M. B. Pepys, E. M. Castano, F. Prelli, T. Wisniewski, A. Golabek, R. A. Kumar, C. Soto, and B. Frangione. 1995. Serum amyloid P component prevents proteolysis of the amyloid fibrils of Alzheimer disease and systemic amyloidosis. Proc. Natl. Acad. Sci. USA. 92: 4299–4303.[Abstract/Free Full Text]

  12. MacRaild, C. A., C. R. Stewart, Y. F. Mok, M. J. Gunzburg, M. A. Perugini, L. J. Lawrence, V. Tirtaatmadja, J. J. Cooper-White, and G. J. Howlett. 2004. Non-fibrillar components of amyloid deposits mediate the self-association and tangling of amyloid fibrils. J. Biol. Chem. 279: 21038–21045.[Abstract/Free Full Text]

  13. Kirkitadze, M. D., M. M. Condron, and D. B. Teplow. 2001. Identification and characterization of key kinetic intermediates in amyloid beta-protein fibrillogenesis. J. Mol. Biol. 312: 1103–1119.[CrossRef][Medline]

  14. Bush, A. I. 2002. Metal complexing agents as therapies for Alzheimer's disease. Neurobiol. Aging. 23: 1031–1038.[CrossRef][Medline]

  15. Marchesi, V. T. 2005. An alternative interpretation of the amyloid A-beta hypothesis with regard to the pathogenesis of Alzheimer's disease. Proc. Natl. Acad. Sci. USA. 102: 9093–9098.[Abstract/Free Full Text]

  16. Cookson, M. R. 2005. The biochemistry of Parkinson's disease. Annu. Rev. Biochem. 74: 29–52.[CrossRef][Medline]

  17. Hatters, D. M., C. E. MacPhee, L. J. Lawrence, W. H. Sawyer, and G. J. Howlett. 2000. Human apolipoprotein C-II forms twisted amyloid ribbons and closed loops. Biochemistry. 39: 8276–8283.[CrossRef][Medline]

  18. Medeiros, L. A., T. Khan, J. B. El Khoury, C. L. Pham, D. M. Hatters, G. J. Howlett, R. Lopez, K. D. O'Brien, and K. J. Moore. 2004. Fibrillar amyloid protein present in atheroma activates CD36 signal transduction. J. Biol. Chem. 279: 10643–10648.[Abstract/Free Full Text]

  19. Tickler, A. K., C. J. Barrow, and J. D. Wade. 2001. Improved preparation of amyloid-beta peptides using DBU as Nalpha-Fmoc deprotection reagent. J. Pept. Sci. 7: 488–494.[CrossRef][Medline]

  20. Cappai, R., S. L. Leck, D. J. Tew, N. A. Williamson, D. P. Smith, D. Galatis, R. A. Sharples, C. C. Curtain, F. E. Ali, R. A. Cherny, et al. 2005. Dopamine promotes alpha-synuclein aggregation into SDS-resistant soluble oligomers via a distinct folding pathway. FASEB J. 19: 1377–1379.[Abstract/Free Full Text]

  21. Wong, M., L. Toh, A. Wilson, K. Rowley, C. Karschimkus, D. Prior, E. Romas, L. Clemens, G. Dragicevic, H. Harianto, et al. 2003. Reduced arterial elasticity in rheumatoid arthritis and the relationship to vascular disease risk factors and inflammation. Arthritis Rheum. 48: 81–89.[CrossRef][Medline]

  22. Lerch, P. G., V. Fortsch, G. Hodler, and R. Bolli. 1996. Production and characterization of a reconstituted high density lipoprotein for therapeutic applications. Vox Sang. 71: 155–164.[CrossRef][Medline]

  23. Schuck, P. 2000. Size-distribution analysis of macromolecules by sedimentation velocity ultracentrifugation and Lamm equation modeling. Biophys. J. 78: 1606–1619.[Medline]

  24. Chait, A., C. Y. Han, J. F. Oram, and J. W. Heinecke. 2005. The immune system and atherogenesis. Lipoprotein-associated inflammatory proteins: markers or mediators of cardiovascular disease? J. Lipid Res. 46: 389–403.[Abstract/Free Full Text]

  25. Pepys, M. B., R. F. Dyck, F. C. de Beer, M. Skinner, and A. S. Cohen. 1979. Binding of serum amyloid P-component (SAP) by amyloid fibrils. Clin. Exp. Immunol. 38: 284–293.[Medline]

  26. Koudinov, A. R., T. T. Berezov, A. Kumar, and N. V. Koudinova. 1998. Alzheimer's amyloid beta interaction with normal human plasma high density lipoprotein: association with apolipoprotein and lipids. Clin. Chim. Acta. 270: 75–84.[CrossRef][Medline]

  27. Sousa, M. M., L. Berglund, and M. J. Saraiva. 2000. Transthyretin in high density lipoproteins: association with apolipoprotein A-I. J. Lipid Res. 41: 58–65.[Abstract/Free Full Text]

  28. Matsubara, E., B. Frangione, and J. Ghiso. 1995. Characterization of apolipoprotein J-Alzheimer's A beta interaction. J. Biol. Chem. 270: 7563–7567.[Abstract/Free Full Text]

  29. Koudinov, A., E. Matsubara, B. Frangione, and J. Ghiso. 1994. The soluble form of Alzheimer's amyloid beta protein is complexed to high density lipoprotein 3 and very high density lipoprotein in normal human plasma. Biochem. Biophys. Res. Commun. 205: 1164–1171.[CrossRef][Medline]

  30. Koldamova, R. P., I. M. Lefterov, M. I. Lefterova, and J. S. Lazo. 2001. Apolipoprotein A-I directly interacts with amyloid precursor protein and inhibits A beta aggregation and toxicity. Biochemistry. 40: 3553–3560.[CrossRef][Medline]

  31. Lewis, G. F., and D. J. Rader. 2005. New insights into the regulation of HDL metabolism and reverse cholesterol transport. Circ. Res. 96: 1221–1232.[Abstract/Free Full Text]

  32. Trigatti, B. L., M. Krieger, and A. Rigotti. 2003. Influence of the HDL receptor SR-BI on lipoprotein metabolism and atherosclerosis. Arterioscler. Thromb. Vasc. Biol. 23: 1732–1738.[Abstract/Free Full Text]

  33. Nissen, S. E., T. Tsunoda, E. M. Tuzcu, P. Schoenhagen, C. J. Cooper, M. Yasin, G. M. Eaton, M. A. Lauer, W. S. Sheldon, C. L. Grines, et al. 2003. Effect of recombinant ApoA-I Milano on coronary atherosclerosis in patients with acute coronary syndromes: a randomized controlled trial. J. Am. Med. Assoc. 290: 2292–2300.[Abstract/Free Full Text]

  34. Nicholls, S. J., B. Cutri, S. G. Worthley, P. Kee, K. A. Rye, S. Bao, and P. J. Barter. 2005. Impact of short-term administration of high-density lipoproteins and atorvastatin on atherosclerosis in rabbits. Arterioscler. Thromb. Vasc. Biol. 11: 2416–2421.

  35. Chung, B. H., F. Franklin, P. Liang, S. Doran, B. H. Cho, and C. A. Curcio. 2005. Phosphatidylcholine-rich acceptors, but not native HDL or its apolipoproteins, mobilize cholesterol from cholesterol-rich insoluble components of human atherosclerotic plaques. Biochim. Biophys. Acta. 1733: 76–89.[Medline]

  36. El Khoury, J. B., K. J. Moore, T. K. Means, J. Leung, K. Terada, M. Toft, M. W. Freeman, and A. D. Luster. 2003. CD36 mediates the innate host response to beta-amyloid. J. Exp. Med. 197: 1657–1666.[Abstract/Free Full Text]

  37. Williams, K. J., and I. Tabas. 1995. The response-to-retention hypothesis of early atherogenesis. Arterioscler. Thromb. Vasc. Biol. 15: 551–561.[Free Full Text]


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
 J. Lipid Res.Home page
C. R. Stewart, A. Haw III, R. Lopez, T. O. McDonald, J. M. Callaghan, M. J. McConville, K. J. Moore, G. J. Howlett, and K. D. O'Brien
Serum amyloid P colocalizes with apolipoproteins in human atheroma: functional implications
J. Lipid Res., October 1, 2007; 48(10): 2162 - 2171.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Supplemental Data
Right arrow All Versions of this Article:
C500022-JLR200v1
47/4/755    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wilson, L. M.
Right arrow Articles by Howlett, G. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wilson, L. M.
Right arrow Articles by Howlett, G. J.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 All ASBMB Journals   Journal of Biological Chemistry 
 Molecular and Cellular Proteomics   ASBMB Today 
Advertisement
spacer
Advertisement
Advertisement