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Sacher S, Mukherjee A, Ray A. Deciphering structural aspects of reverse cholesterol transport: mapping the knowns and unknowns. Biol Rev Camb Philos Soc 2023; 98:1160-1183. [PMID: 36880422 DOI: 10.1111/brv.12948] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 02/03/2023] [Accepted: 02/24/2023] [Indexed: 03/08/2023]
Abstract
Atherosclerosis is a major contributor to the onset and progression of cardiovascular disease (CVD). Cholesterol-loaded foam cells play a pivotal role in forming atherosclerotic plaques. Induction of cholesterol efflux from these cells may be a promising approach in treating CVD. The reverse cholesterol transport (RCT) pathway delivers cholesteryl ester (CE) packaged in high-density lipoproteins (HDL) from non-hepatic cells to the liver, thereby minimising cholesterol load of peripheral cells. RCT takes place via a well-organised interplay amongst apolipoprotein A1 (ApoA1), lecithin cholesterol acyltransferase (LCAT), ATP binding cassette transporter A1 (ABCA1), scavenger receptor-B1 (SR-B1), and the amount of free cholesterol. Unfortunately, modulation of RCT for treating atherosclerosis has failed in clinical trials owing to our lack of understanding of the relationship between HDL function and RCT. The fate of non-hepatic CEs in HDL is dependent on their access to proteins involved in remodelling and can be regulated at the structural level. An inadequate understanding of this inhibits the design of rational strategies for therapeutic interventions. Herein we extensively review the structure-function relationships that are essential for RCT. We also focus on genetic mutations that disturb the structural stability of proteins involved in RCT, rendering them partially or completely non-functional. Further studies are necessary for understanding the structural aspects of RCT pathway completely, and this review highlights alternative theories and unanswered questions.
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Affiliation(s)
- Sukriti Sacher
- Department of Computational Biology, Indraprastha Institute of Information Technology, Okhla Phase III, New Delhi, 110019, India
| | - Abhishek Mukherjee
- Dhiti Life Sciences Pvt Ltd, B-107, Okhla Phase I, New Delhi, 110020, India
| | - Arjun Ray
- Department of Computational Biology, Indraprastha Institute of Information Technology, Okhla Phase III, New Delhi, 110019, India
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2
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Fukuda R, Saito M, Shibukawa S, Sumino A, Nakano M, Murakami T. Urea-Assisted Reconstitution of Discoidal High-Density Lipoprotein. Biochemistry 2020; 59:1455-1464. [DOI: 10.1021/acs.biochem.0c00075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Ryosuke Fukuda
- Department of Biotechnology, Graduate School of Engineering, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan
| | - Mio Saito
- Department of Biotechnology, Graduate School of Engineering, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan
| | - Shiori Shibukawa
- Department of Pharmaceutical Engineering, Faculty of Engineering, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan
| | - Ayumi Sumino
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa 920-1192, Japan
- Institute for Frontier Science Initiative, Kanazawa University, Kanazawa 920-1192, Japan
| | - Minoru Nakano
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Toyama 930-0194, Japan
| | - Tatsuya Murakami
- Department of Biotechnology, Graduate School of Engineering, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan
- Department of Pharmaceutical Engineering, Faculty of Engineering, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan
- Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University Institute for Advanced Study (KUIAS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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3
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Alshehab M, Budamagunta MS, Voss JC, Nitin N. Real-time measurements of milk fat globule membrane modulation during simulated intestinal digestion using electron paramagnetic resonance spectroscopy. Colloids Surf B Biointerfaces 2019; 184:110511. [PMID: 31600680 DOI: 10.1016/j.colsurfb.2019.110511] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 09/13/2019] [Accepted: 09/15/2019] [Indexed: 12/14/2022]
Abstract
Milk Fat Globules with their unique interfacial structure and membrane composition are a key nutritional source for mammalian infants, however, there is a limited understanding of the dynamics of fat digestion in these structures. Lipid digestion is an interfacial process involving interactions of enzymes and bile salts with the interface of suspended lipid droplets in an aqueous environment. In this study, we have developed an electron paramagnetic resonance spectroscopy approach to evaluate real time dynamics of milk fat globules interfacial structure during simulated intestinal digestion. To measure these dynamics, natural milk fat globule membrane was labeled with EPR-active probe, partitioning of EPR probes into MFGs membrane was validated using saturation-recovery measurements and calculation of the depth parameter Φ. After validation, the selected spin probe was used to evaluate the membrane's fluidity as a measure of the interface's modulation in the presence of bile salts and pancreatic lipase. Independently, bile salts were found to have a rigidifying effect on the spin probed MFGM, while pancreatic lipase resulted in an increase in membrane fluidity. When combined, the effect of lipase appears to be diminished in the presence of bile salts. These results indicate the efficacy of EPR in providing an insight into small time scale molecular dynamics of phospholipid interfaces in milk fat globules. Understanding interfacial dynamics of naturally occurring complex structures can significantly aid in understanding the role of interfacial composition and structural complexity in delivery of nutrients during digestion.
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Affiliation(s)
- Maha Alshehab
- Department of Food Science and Technology, University of California-Davis, Davis, CA 95616, United States
| | - Madhu S Budamagunta
- Department of Biochemistry and Molecular Medicine, University of California-Davis, Davis, CA 95616, United States
| | - John C Voss
- Department of Biochemistry and Molecular Medicine, University of California-Davis, Davis, CA 95616, United States
| | - Nitin Nitin
- Department of Food Science and Technology, University of California-Davis, Davis, CA 95616, United States.
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4
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Domingo-Espín J, Nilsson O, Bernfur K, Del Giudice R, Lagerstedt JO. Site-specific glycations of apolipoprotein A-I lead to differentiated functional effects on lipid-binding and on glucose metabolism. Biochim Biophys Acta Mol Basis Dis 2018; 1864:2822-2834. [PMID: 29802959 DOI: 10.1016/j.bbadis.2018.05.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 05/17/2018] [Accepted: 05/22/2018] [Indexed: 02/06/2023]
Abstract
Prolonged hyperglycemia in poorly controlled diabetes leads to an increase in reactive glucose metabolites that covalently modify proteins by non-enzymatic glycation reactions. Apolipoprotein A-I (apoA-I) of high-density lipoprotein (HDL) is one of the proteins that becomes glycated in hyperglycemia. The impact of glycation on apoA-I protein structure and function in lipid and glucose metabolism were investigated. ApoA-I was chemically glycated by two different glucose metabolites (methylglyoxal and glycolaldehyde). Synchrotron radiation and conventional circular dichroism spectroscopy were used to study apoA-I structure and stability. The ability to bind lipids was measured by lipid-clearance assay and native gel analysis, and cholesterol efflux was measured by using lipid-laden J774 macrophages. Diet induced obese mice with established insulin resistance, L6 rat and C2C12 mouse myocytes, as well as INS-1E rat insulinoma cells, were used to determine in vivo and in vitro glucose uptake and insulin secretion. Site-specific, covalent modifications of apoA-I (lysines or arginines) led to altered protein structure, reduced lipid binding capability and a reduced ability to catalyze cholesterol efflux from macrophages, partly in a modification-specific manner. The stimulatory effects of apoA-I on the in vivo glucose clearance were negatively affected when apoA-I was modified with methylglyoxal, but not with glycolaldehyde. The in vitro data showed that both glucose uptake in muscle cells and insulin secretion from beta cells were affected. Taken together, glycation modifications impair the apoA-I protein functionality in lipid and glucose metabolism, which is expected to have implications for diabetes patients with poorly controlled blood glucose.
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Affiliation(s)
- Joan Domingo-Espín
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
| | - Oktawia Nilsson
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
| | - Katja Bernfur
- Department of Biochemistry and Structural Biology, Lund University, S-221 84 Lund, Sweden
| | - Rita Del Giudice
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
| | - Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden.
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5
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Oda MN. Lipid-free apoA-I structure - Origins of model diversity. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:221-233. [PMID: 27890580 DOI: 10.1016/j.bbalip.2016.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 10/20/2016] [Accepted: 11/20/2016] [Indexed: 01/22/2023]
Abstract
Apolipoprotein A-I (apoA-I) is a prominent member of the exchangeable apolipoprotein class of proteins, capable of transitioning between lipid-bound and lipid-free states. It is the primary structural and functional protein of high density lipoprotein (HDL). Lipid-free apoA-I is critical to de novo HDL formation as it is the preferred substrate of the lipid transporter, ATP Binding Cassette Transporter A1 (ABCA1) Remaley et al. (2001) [1]. Lipid-free apoA-I is an important element in reverse cholesterol transport and comprehension of its structure is a core issue in our understanding of cholesterol metabolism. However, lipid-free apoA-I is highly conformationally dynamic making it a challenging subject for structural analysis. Over the past 20years there have been significant advances in overcoming the dynamic nature of lipid-free apoA-I, which have resulted in a multitude of proposed conformational models.
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Affiliation(s)
- Michael N Oda
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, United States.
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6
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Petrlova J, Hilt S, Budamagunta M, Domingo-Espín J, Voss JC, Lagerstedt JO. Molecular crowding impacts the structure of apolipoprotein A-I with potential implications on in vivo metabolism and function. Biopolymers 2016; 105:683-92. [PMID: 27122373 DOI: 10.1002/bip.22865] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 03/14/2016] [Accepted: 04/25/2016] [Indexed: 11/08/2022]
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. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 683-692, 2016.
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Affiliation(s)
- Jitka Petrlova
- Department of Experimental Medical Science, Lund University, Lund, S-221 84, Sweden
| | - Silvia Hilt
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, 95616
| | - Madhu Budamagunta
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, 95616
| | - Joan Domingo-Espín
- Department of Experimental Medical Science, Lund University, Lund, S-221 84, Sweden
| | - John C Voss
- Department of Experimental Medical Science, Lund University, Lund, S-221 84, Sweden.,Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, 95616
| | - Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, Lund, S-221 84, Sweden
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7
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Dalla-Riva J, Lagerstedt JO, Petrlova J. Structural and Functional Analysis of the ApolipoproteinA-I A164S Variant. PLoS One 2015; 10:e0143915. [PMID: 26605794 PMCID: PMC4659549 DOI: 10.1371/journal.pone.0143915] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 11/11/2015] [Indexed: 01/15/2023] Open
Abstract
Apolipoprotein A-I (apoA-I) is the main protein involved in the formation of high-density lipoprotein (HDL), it is the principal mediator of the reverse cholesterol transfer (RCT) pathway and provides cardio-protection. In addition to functional wild-type apoA-I, several variants have been shown to associate with hereditary amyloidosis. In this study we have performed biophysical and biochemical analyses of the structure and functional properties of the A164S variant of apoA-I (1:500 in the Danish general population), which is the first known mutation of apoA-I that leads to an increased risk of ischaemic heart disease (IHD), myocardial infarction and mortality without associated low HDL cholesterol levels. Despite the fact that epidemiologically IHD is associated with low plasma levels of HDL, the A164S mutation is linked to normal plasma levels of lipids, HDL and apoA-I, suggesting impaired functionality of this variant. Using biophysical techniques (e.g., circular dichroism spectroscopy and electron microscopy) to determine secondary structure, stability and pro-amyloidogenic property of the lipid free A164S apoA-I variant, our observations suggest similarity in structural properties between apoA-I WT and apoA-I A164S. However, the A164S apoA-I variant exhibits lower binding affinity to lipids but forms similar sized HDL particles to those produced by WT.
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Affiliation(s)
| | - Jens O. Lagerstedt
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail:
| | - Jitka Petrlova
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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8
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9
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Petrlova J, Bhattacherjee A, Boomsma W, Wallin S, Lagerstedt JO, Irbäck A. Conformational and aggregation properties of the 1-93 fragment of apolipoprotein A-I. Protein Sci 2014; 23:1559-71. [PMID: 25131953 DOI: 10.1002/pro.2534] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/11/2014] [Accepted: 08/04/2014] [Indexed: 11/12/2022]
Abstract
Several disease-linked mutations of apolipoprotein A-I, the major protein in high-density lipoprotein (HDL), are known to be amyloidogenic, and the fibrils often contain N-terminal fragments of the protein. Here, we present a combined computational and experimental study of the fibril-associated disordered 1-93 fragment of this protein, in wild-type and mutated (G26R, S36A, K40L, W50R) forms. In atomic-level Monte Carlo simulations of the free monomer, validated by circular dichroism spectroscopy, we observe changes in the position-dependent β-strand probability induced by mutations. We find that these conformational shifts match well with the effects of these mutations in thioflavin T fluorescence and transmission electron microscopy experiments. Together, our results point to molecular mechanisms that may have a key role in disease-linked aggregation of apolipoprotein A-I.
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Affiliation(s)
- Jitka Petrlova
- Department of Experimental Medical Science, Lund University, BMC Floor C12, SE-221 84, Lund, Sweden
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10
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Microenvironmentally controlled secondary structure motifs of apolipoprotein A-I derived peptides. Mol Cell Biochem 2014; 393:99-109. [PMID: 24748322 PMCID: PMC4067536 DOI: 10.1007/s11010-014-2050-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 04/02/2014] [Indexed: 11/12/2022]
Abstract
The structure of apolipoprotein A-I (apoA-I), the major protein of HDL, has been extensively studied in past years. Nevertheless, its corresponding three-dimensional structure has been difficult to obtain due to the frequent conformational changes observed depending on the microenvironment. Although the function of each helical segment of this protein remains unclear, it has been observed that the apoA-I amino (N) and carboxy-end (C) domains are directly involved in receptor-recognition, processes that determine the diameter for HDL particles. In addition, it has been observed that the high structural plasticity of these segments might be related to several amyloidogenic processes. In this work, we studied a series of peptides derived from the N- and C-terminal domains representing the most hydrophobic segments of apoA-I. Measurements carried out using circular dichroism in all tested peptides evidenced that the lipid environment promotes the formation of α-helical structures, whereas an aqueous environment facilitates a strong tendency to adopt β-sheet/disordered conformations. Electron microscopy observations showed the formation of amyloid-like structures similar to those found in other well-defined amyloidogenic proteins. Interestingly, when the apoA-I peptides were incubated under conditions that promote stable globular structures, two of the peptides studied were cytotoxic to microglia and mouse macrophage cells. Our findings provide an insight into the physicochemical properties of key segments contained in apoA-I which may be implicated in disorder-to-order transitions that in turn maintain the delicate equilibrium between both, native and abnormal conformations, and therefore control its propensity to become involved in pathological processes.
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11
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Lagerstedt JO, Petrlova J, Hilt S, Marek A, Chung Y, Sriram R, Budamagunta MS, Desreux JF, Thonon D, Jue T, Smirnov AI, Voss JC. EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels. CONTRAST MEDIA & MOLECULAR IMAGING 2013; 8:252-64. [PMID: 23606429 DOI: 10.1002/cmmi.1518] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 10/30/2012] [Accepted: 11/03/2012] [Indexed: 11/06/2022]
Abstract
We have engineered apolipoprotein A-I (apoA-I), a major protein constituent of high-density lipoprotein (HDL), to contain DOTA-chelated Gd(III) as an MRI contrast agent for the purpose of imaging reconstituted HDL (rHDL) biodistribution, metabolism and regulation in vivo. This protein contrast agent was obtained by attaching the thiol-reactive Gd[MTS-ADO3A] label at Cys residues replaced at four distinct positions (52, 55, 76 and 80) in apoA-I. MRI of infused mice previously showed that the Gd-labeled apoA-I migrates to both the liver and the kidney, the organs responsible for HDL catabolism; however, the contrast properties of apoA-I are superior when the ADO3A moiety is located at position 55, compared with the protein labeled at positions 52, 76 or 80. It is shown here that continuous wave X-band (9 GHz) electron paramagnetic resonance (EPR) spectroscopy is capable of detecting differences in the Gd(III) signal when comparing the labeled protein in the lipid-free with the rHDL state. Furthermore, the values of NMR relaxivity obtained for labeled variants in both the lipid-free and rHDL states correlate to the product of the X-band Gd(III) spectral width and the collision frequency between a nitroxide spin label and a polar relaxation agent. Consistent with its superior relaxivity measured by NMR, the rHDL-associated apoA-I containing the Gd[MTS-ADO3A] probe attached to position 55 displays favorable dynamic and water accessibility properties as determined by X-band EPR. While room temperature EPR requires >1 m m Gd(III)-labeled and only >10 µ m nitroxide-labeled protein to resolve the spectrum, the volume requirement is exceptionally low (~5 µl). Thus, X-band EPR provides a practical assessment for the suitability of imaging candidates containing the site-directed ADO3A contrast probe.
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Affiliation(s)
- Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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12
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Borja MS, Zhao L, Hammerson B, Tang C, Yang R, Carson N, Fernando G, Liu X, Budamagunta MS, Genest J, Shearer GC, Duclos F, Oda MN. HDL-apoA-I exchange: rapid detection and association with atherosclerosis. PLoS One 2013; 8:e71541. [PMID: 24015188 PMCID: PMC3756009 DOI: 10.1371/journal.pone.0071541] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 06/28/2013] [Indexed: 01/23/2023] Open
Abstract
High density lipoprotein (HDL) cholesterol levels are associated with decreased risk of cardiovascular disease, but not all HDL are functionally equivalent. A primary determinant of HDL functional status is the conformational adaptability of its main protein component, apoA-I, an exchangeable apolipoprotein. Chemical modification of apoA-I, as may occur under conditions of inflammation or diabetes, can severely impair HDL function and is associated with the presence of cardiovascular disease. Chemical modification of apoA-I also impairs its ability to exchange on and off HDL, a critical process in reverse cholesterol transport. In this study, we developed a method using electron paramagnetic resonance spectroscopy (EPR) to quantify HDL-apoA-I exchange. Using this approach, we measured the degree of HDL-apoA-I exchange for HDL isolated from rabbits fed a high fat, high cholesterol diet, as well as human subjects with acute coronary syndrome and metabolic syndrome. We observed that HDL-apoA-I exchange was markedly reduced when atherosclerosis was present, or when the subject carries at least one risk factor of cardiovascular disease. These results show that HDL-apoA-I exchange is a clinically relevant measure of HDL function pertinent to cardiovascular disease.
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Affiliation(s)
- Mark S. Borja
- Children's Hospital Oakland Research Institute, Oakland, California, United States of America
| | - Lei Zhao
- Cardiovascular Drug Discovery, Bristol-Myers Squibb Company, Pennington, New Jersey, United States of America
| | - Bradley Hammerson
- Accent Assays, Inc., Sacramento, California, United States of America
| | - Chongren Tang
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
| | - Richard Yang
- Cardiovascular Drug Discovery, Bristol-Myers Squibb Company, Pennington, New Jersey, United States of America
| | - Nancy Carson
- Cardiovascular Drug Discovery, Bristol-Myers Squibb Company, Pennington, New Jersey, United States of America
| | - Gayani Fernando
- Cardiovascular Drug Discovery, Bristol-Myers Squibb Company, Pennington, New Jersey, United States of America
| | - Xiaoqin Liu
- Cardiovascular Drug Discovery, Bristol-Myers Squibb Company, Pennington, New Jersey, United States of America
| | - Madhu S. Budamagunta
- Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, California, United States of America
| | - Jacques Genest
- Royal Victoria Hospital, McGill University Health Centre, Montreal, Quebec, Canada
| | - Gregory C. Shearer
- Cardiovascular Health Research Center, Sanford Research/USD, Sioux Falls, South Dakota, United States of America
- Department of Internal Medicine and Department of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Sioux Falls, South Dakota, United States of America
| | - Franck Duclos
- Cardiovascular Drug Discovery, Bristol-Myers Squibb Company, Pennington, New Jersey, United States of America
| | - Michael N. Oda
- Children's Hospital Oakland Research Institute, Oakland, California, United States of America
- * E-mail:
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13
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Oda MN, Budamagunta MS, Borja MS, Petrlova J, Voss JC, Lagerstedt JO. The secondary structure of apolipoprotein A-I on 9.6-nm reconstituted high-density lipoprotein determined by EPR spectroscopy. FEBS J 2013; 280:3416-24. [PMID: 23668303 PMCID: PMC3906832 DOI: 10.1111/febs.12334] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 05/09/2013] [Accepted: 05/09/2013] [Indexed: 01/09/2023]
Abstract
Apolipoprotein A-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 residues 99–163 on 9.6-nm reconstituted HDL was analyzed by EPR. In previous analyses, we examined residues 6–98 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 β-strand (residues 149–157). 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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Affiliation(s)
- Michael N Oda
- Children's Hospital Oakland Research Institute, CA, USA
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14
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Dalla-Riva J, Stenkula KG, Petrlova J, Lagerstedt JO. Discoidal HDL and apoA-I-derived peptides improve glucose uptake in skeletal muscle. J Lipid Res 2013; 54:1275-82. [PMID: 23471027 PMCID: PMC3653404 DOI: 10.1194/jlr.m032904] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Lipid-free apoA-I and mature spherical HDL have been shown to induce glucose uptake in skeletal muscle. To exploit apoA-I and HDL states for diabetes therapy, further understanding of interaction between muscle and apoA-I is required. This study has examined whether nascent discoidal HDL, in which apoA-I attains a different conformation from mature HDL and lipid-free states, could induce muscle glucose uptake and whether a specific domain of apoA-I can mediate this effect. Using L6 myotubes stimulated with synthetic reconstituted discoidal HDL (rHDL), we show a glucose uptake effect comparable to insulin. Increased plasma membrane GLUT4 levels in ex vivo rHDL-stimulated myofibers from HA-GLUT4-GFP transgenic mice support this observation. rHDL increased phosphorylation of AMP kinase (AMPK) and acetyl-coA carboxylase (ACC) but not Akt. A survey of domain-specific peptides of apoA-I showed that the lipid-free C-terminal 190-243 fragment increases plasma membrane GLUT4, promotes glucose uptake, and activates AMPK signaling but not Akt. This may be explained by changes in α-helical content of 190-243 fragment versus full-length lipid-free apoA-I as assessed by circular dichroism spectroscopy. Discoidal HDL and the 190-243 peptide of apoA-I are potent agonists of glucose uptake in skeletal muscle, and the C-terminal α-helical content of apoA-I may be an important determinant of this effect.
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Affiliation(s)
- Jonathan Dalla-Riva
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
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15
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Loavenbruck AJ, Chaudhry V, Zeldenrust SR, Spinner RJ, Theis JD, Klein CJ. Mass spectrometry analysis reveals non-mutated apolipoprotein A1 lumbosacral radiculoplexus amyloidoma. Muscle Nerve 2012; 46:817-22. [PMID: 23055319 DOI: 10.1002/mus.23415] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION In rare instances, amyloidosis presents as a focal, macroscopic lesion involving peripheral neural tissues (amyloidoma). In all known reported cases, peripheral nerve amyloidomas have had immunoglobulin light-chain fibril composition and occurred in the context of paraproteinemia. METHODS A 46-year-old man presented with progressive insidious-onset right lumbosacral radiculoplexus neuropathy without paraproteinemia. MRI-targeted fascicular nerve biopsy was performed on an enlarged sciatic nerve after earlier distal fibular nerve biopsy was nondiagnostic. Laser dissected mass spectroscopy of the discovered amyloid protein was performed after immunohistochemistry failed to identify the specific amyloid protein. Complete gene sequencing of apolipoprotein A1 (ApoA1) was performed. RESULTS Only wild-type ApoA1 amyloid was found in the congophilic component in the nerve. CONCLUSIONS This case highlights the utility of MRI-guided fascicular nerve biopsy combined with laser-dissected mass spectrometric analysis. Importantly, the case expands the known causes of amyloidomas to include wild-type ApoA1.
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Affiliation(s)
- Adam J Loavenbruck
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
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16
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Phillips MC. New insights into the determination of HDL structure by apolipoproteins: Thematic review series: high density lipoprotein structure, function, and metabolism. J Lipid Res 2012; 54:2034-2048. [PMID: 23230082 DOI: 10.1194/jlr.r034025] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Apolipoprotein (apo)A-I is the principal protein component of HDL, and because of its conformational adaptability, it can stabilize all HDL subclasses. The amphipathic α-helix is the structural motif that enables apoA-I to achieve this functionality. In the lipid-free state, the helical segments unfold and refold in seconds and are located in the N-terminal two thirds of the molecule where they are loosely packed as a dynamic, four-helix bundle. The C-terminal third of the protein forms an intrinsically disordered domain that mediates initial binding to phospholipid surfaces, which occurs with coupled α-helix formation. The lipid affinity of apoA-I confers detergent-like properties; it can solubilize vesicular phospholipids to create discoidal HDL particles with diameters of approximately 10 nm. Such particles contain a segment of phospholipid bilayer and are stabilized by two apoA-I molecules that are arranged in an anti-parallel, double-belt conformation around the edge of the disc, shielding the hydrophobic phospholipid acyl chains from exposure to water. The apoA-I molecules are in a highly dynamic state, and they stabilize discoidal particles of different sizes by certain segments forming loops that detach reversibly from the particle surface. The flexible apoA-I molecule adapts to the surface of spherical HDL particles by bending and forming a stabilizing trefoil scaffold structure. The above characteristics of apoA-I enable it to partner with ABCA1 in mediating efflux of cellular phospholipid and cholesterol and formation of a heterogeneous population of nascent HDL particles. Novel insights into the structure-function relationships of apoA-I should help reveal mechanisms by which HDL subclass distribution can be manipulated.
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Affiliation(s)
- Michael C Phillips
- Lipid Research Group, Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA.
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17
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Francis DJ, Hubbell WL, Klug CS. Probing Protein Secondary Structure using EPR: Investigating a Dynamic Region of Visual Arrestin. APPLIED MAGNETIC RESONANCE 2012; 43:405-419. [PMID: 25419051 PMCID: PMC4240029 DOI: 10.1007/s00723-012-0369-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
One key application of site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is the determination of sequence-specific secondary structure in proteins. Regular secondary structure leads to a periodic variation in both side chain motion and solvent accessibility, two properties easily monitored by EPR techniques. Specifically, saturation recovery (SR) EPR spectroscopy has proven to be useful for making accessibility measurements for multiple protein structure populations by determining individual accessibilities and is therefore well suited to study the structure of proteins exhibiting multiple conformations in equilibrium. Here we employ both continuous wave and SR EPR spectroscopy in combination to examine the secondary structure of a short sequence showing conformational heterogeneity in visual rod arrestin. The EPR data presented here clearly distinguish between the unstructured loop and the helical structure formed in the crystallographic tetramer of visual arrestin and show that this region is unstructured in solution.
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Affiliation(s)
- Derek J. Francis
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Wayne L. Hubbell
- Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095
| | - Candice S. Klug
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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18
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Sorci-Thomas MG, Owen JS, Fulp B, Bhat S, Zhu X, Parks JS, Shah D, Jerome WG, Gerelus M, Zabalawi M, Thomas MJ. Nascent high density lipoproteins formed by ABCA1 resemble lipid rafts and are structurally organized by three apoA-I monomers. J Lipid Res 2012; 53:1890-909. [PMID: 22750655 PMCID: PMC3413229 DOI: 10.1194/jlr.m026674] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/29/2012] [Indexed: 12/29/2022] Open
Abstract
This report details the lipid composition of nascent HDL (nHDL) particles formed by the action of the ATP binding cassette transporter A1 (ABCA1) on apolipoprotein A-I (apoA-I). nHDL particles of different size (average diameters of ∼ 12, 10, 7.5, and <6 nm) and composition were purified by size-exclusion chromatography. Electron microscopy suggested that the nHDL were mostly spheroidal. The proportions of the principal nHDL lipids, free cholesterol, glycerophosphocholine, and sphingomyelin were similar to that of lipid rafts, suggesting that the lipid originated from a raft-like region of the cell. Smaller amounts of glucosylceramides, cholesteryl esters, and other glycerophospholipid classes were also present. The largest particles, ∼ 12 nm and 10 nm diameter, contained ∼ 43% free cholesterol, 2-3% cholesteryl ester, and three apoA-I molecules. Using chemical cross-linking chemistry combined with mass spectrometry, we found that three molecules of apoA-I in the ∼ 9-14 nm nHDL adopted a belt-like conformation. The smaller (7.5 nm diameter) spheroidal nHDL particles carried 30% free cholesterol and two molecules of apoA-I in a twisted, antiparallel, double-belt conformation. Overall, these new data offer fresh insights into the biogenesis and structural constraints involved in forming nascent HDL from ABCA1.
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Affiliation(s)
- Mary G Sorci-Thomas
- Department of Pathology, Section on Lipid Sciences, Wake Forest Baptist Medical Center, Winston-Salem, NC 27157, USA.
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19
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Niedziela-Majka A, Lad L, Chisholm JW, Lagpacan L, Schwartz K, Hung M, Jin D, Fung W, Brendza KM, Liu X, Pagratis N, Sakowicz R. Lipid-sensing high-throughput ApoA-I assays. ACTA ACUST UNITED AC 2012; 17:1050-61. [PMID: 22811478 DOI: 10.1177/1087057112451923] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Apolipoprotein A-I (ApoA-I), a primary protein component of high-density lipoprotein (HDL), plays an important role in cholesterol metabolism mediating the formation of HDL and the efflux of cellular cholesterol from macrophage foam cells in arterial walls. Lipidation of ApoA-I is mediated by adenosine triphosphate (ATP) binding cassette A1 (ABCA1). Insufficient ABCA1 activity may lead to increased risk of atherosclerosis due to reduced HDL formation and cholesterol efflux. The standard radioactive assay for measuring cholesterol transport to ApoA-I has low throughput and poor dynamic range, and it fails to measure phospholipid transfer. We describe the development of two sensitive, nonradioactive high-throughput assays that report on the lipidation of ApoA-I: a homogeneous assay based on time-resolved fluorescence resonance energy transfer (TR-FRET) and a discontinuous assay that uses the label-free Epic platform. The TR-FRET assay employs HiLyte Fluor 647-labeled ApoA-I with N-terminal biotin bound to streptavidin-terbium. When fluorescent ApoA-I was incorporated into HDL, TR-FRET decreased proportionally to the increase in the ratio of lipids to ApoA-I, demonstrating that the assay was sensitive to the amount of lipid bound to ApoA-I. In the Epic assay, biotinylated ApoA-I was captured on a streptavidin-coated biosensor. Measured resonant wavelength shift was proportional to the amount of lipids associated with ApoA-I, indicating that the assay senses ApoA-I lipidation.
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20
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Apolipoprotein A-I helical structure and stability in discoidal high-density lipoprotein (HDL) particles by hydrogen exchange and mass spectrometry. Proc Natl Acad Sci U S A 2012; 109:11687-92. [PMID: 22745166 DOI: 10.1073/pnas.1209305109] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
To understand high-density lipoprotein (HDL) structure at the molecular level, the location and stability of α-helical segments in human apolipoprotein (apo) A-I in large (9.6 nm) and small (7.8 nm) discoidal HDL particles were determined by hydrogen-deuterium exchange (HX) and mass spectrometry methods. The measured HX kinetics of some 100 apoA-I peptides specify, at close to amino acid resolution, the structural condition of segments throughout the protein sequence and changes in structure and stability that occur on incorporation into lipoprotein particles. When incorporated into the large HDL particle, the nonhelical regions in lipid-free apoA-I (residues 45-53, 66-69, 116-146, and 179-236) change conformation from random coil to α-helix so that nearly the entire apoA-I molecule adopts helical structure (except for the terminal residues 1-6 and 237-243). The amphipathic α-helices have relatively low stability, in the range 3-5 kcal/mol, indicating high flexibility and dynamic unfolding and refolding in seconds or less. A segment encompassed by residues 125-158 exhibits bimodal HX labeling indicating co-existing helical and disordered loop conformations that interchange on a time scale of minutes. When incorporated around the edge of the smaller HDL particle, the increase in packing density of the two apoA-I molecules forces about 20% more residues out of direct contact with the phospholipid molecules to form disordered loops, and these are the same segments that form loops in the lipid-free state. The region of disc-associated apoA-I that binds the lecithin-cholesterol acyltransferase enzyme is well structured and not a protruding unstructured loop as reported by others.
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21
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Lagerstedt JO, Budamagunta MS, Liu GS, DeValle NC, Voss JC, Oda MN. The "beta-clasp" model of apolipoprotein A-I--a lipid-free solution structure determined by electron paramagnetic resonance spectroscopy. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:448-55. [PMID: 22245143 DOI: 10.1016/j.bbalip.2011.12.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2011] [Revised: 12/06/2011] [Accepted: 12/20/2011] [Indexed: 02/02/2023]
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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Affiliation(s)
- Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
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22
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Petrlova J, Duong T, Cochran MC, Axelsson A, Mörgelin M, Roberts LM, Lagerstedt JO. The fibrillogenic L178H variant of apolipoprotein A-I forms helical fibrils. J Lipid Res 2011; 53:390-398. [PMID: 22184756 PMCID: PMC3276462 DOI: 10.1194/jlr.m020883] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
A number of amyloidogenic variants of apoA-I have been discovered but most have not
been analyzed. Previously, we showed that the G26R mutation of apoA-I leads to
increased β-strand structure, increased N-terminal protease susceptibility, and
increased fibril formation after several days of incubation. In vivo, this and other
variants mutated in the N-terminal domain (residues 26 to ∼90) lead to renal and
hepatic accumulation. In contrast, several mutations identified within residues 170
to 178 lead to cardiac, laryngeal, and cutaneous protein deposition. Here, we
describe the structural changes in the fibrillogenic variant L178H. Like G26R, the
initial structure of the protein exhibits altered tertiary conformation relative to
wild-type protein along with decreased stability and an altered lipid binding
profile. However, in contrast to G26R, L178H undergoes an increase in helical
structure upon incubation at 37°C with a half time (t1/2) of about 12
days. Upon prolonged incubation, the L178H mutant forms fibrils of a diameter of 10
nm that ranges in length from 30 to 120 nm. These results show that apoA-I, known for
its dynamic properties, has the ability to form multiple fibrillar conformations,
which may play a role in the tissue-specific deposition of the individual
variants.
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Affiliation(s)
- Jitka Petrlova
- Department of Experimental Medical Sciences, Lund University, S-221 84 Lund, Sweden; and
| | - Trang Duong
- Department of Chemistry, California State University Sacramento, Sacramento, CA 95819
| | - Megan C Cochran
- Department of Chemistry, California State University Sacramento, Sacramento, CA 95819
| | - Annika Axelsson
- Department of Experimental Medical Sciences, Lund University, S-221 84 Lund, Sweden; and
| | - Matthias Mörgelin
- Department of Experimental Medical Sciences, and Department of Infection Medicine, Lund University, S-221 84 Lund, Sweden; and
| | - Linda M Roberts
- Department of Chemistry, California State University Sacramento, Sacramento, CA 95819.
| | - Jens O Lagerstedt
- Department of Experimental Medical Sciences, Lund University, S-221 84 Lund, Sweden; and.
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23
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Ly S, Petrlova J, Huser T, Fore S, Gao T, Voss J, Laurence TA. Stoichiometry of reconstituted high-density lipoproteins in the hydrated state determined by photon antibunching. Biophys J 2011; 101:970-5. [PMID: 21843489 DOI: 10.1016/j.bpj.2011.06.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 06/28/2011] [Accepted: 06/29/2011] [Indexed: 10/17/2022] Open
Abstract
Apolipoprotein A-I plays a central role in the solution structure of high-density lipoproteins. Determining the stoichiometry of lipid-bound apo A-I in the hydrated state is therefore fundamental to understanding how high-density lipoproteins form and function. Here, we use the quantum optical phenomenon of photon antibunching to determine the number of apo A-I molecules bound to discoidal lipoproteins and compare this with values obtained by photon-counting histogram analysis. Both the photon antibunching and photon-counting analyses show that reconstituted high-density lipoprotein particles contain two apo A-I molecules, which is in agreement with the commonly accepted double-belt model.
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Affiliation(s)
- Sonny Ly
- Physical and Life Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
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24
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Jayaraman S, Abe-Dohmae S, Yokoyama S, Cavigiolio G. Impact of self-association on function of apolipoprotein A-I. J Biol Chem 2011; 286:35610-35623. [PMID: 21835924 DOI: 10.1074/jbc.m111.262485] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Self-association is an inherent property of the lipid-free forms of several exchangeable apolipoproteins, including apolipoprotein A-I (apoA-I), the main protein component of high density lipoproteins (HDL) and an established antiatherogenic factor. Monomeric lipid-free apoA-I is believed to be the biologically active species, but abnormal conditions, such as specific natural mutations or oxidation, produce an altered state of self-association that may contribute to apoA-I dysfunction. Replacement of the tryptophans of apoA-I with phenylalanines (ΔW-apoA-I) leads to unusually large and stable self-associated species. We took advantage of this unique solution property of ΔW-apoA-I to analyze the role of self-association in determining the structure and lipid-binding properties of apoA-I as well as ATP-binding cassette A1 (ABCA1)-mediated cellular lipid release, a relevant pathway in atherosclerosis. Monomeric ΔW-apoA-I and wild-type apoA-I activated ABCA1-mediated cellular lipid release with similar efficiencies, whereas the efficiency of high order self-associated species was reduced to less than 50%. Analysis of specific self-associated subclasses revealed that different factors influence the rate of HDL formation in vitro and ABCA1-mediated lipid release efficiency. The α-helix-forming ability of apoA-I is the main determinant of in vitro lipid solubilization rates, whereas loss of cellular lipid release efficiency is mainly caused by reduced structural flexibility by formation of stable quaternary interactions. Thus, stabilization of self-associated species impairs apoA-I biological activity through an ABCA1-mediated mechanism. These results afford mechanistic insights into the ABCA1 reaction and suggest self-association as a functional feature of apoA-I. Physiologic mechanisms may alter the native self-association state and contribute to apoA-I dysfunction.
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Affiliation(s)
- Shobini Jayaraman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Sumiko Abe-Dohmae
- Department of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Shinji Yokoyama
- Department of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Giorgio Cavigiolio
- Children's Hospital Oakland Research Institute, Oakland, California 94609.
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25
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Sriram R, Lagerstedt JO, Petrlova J, Samardzic H, Kreutzer U, Xie H, Kaysen GA, Desreux JF, Thonon D, Jacques V, Van Loan M, Rutledge JC, Oda MN, Voss JC, Jue T. Imaging apolipoprotein AI in vivo. NMR IN BIOMEDICINE 2011; 24:916-24. [PMID: 21264979 PMCID: PMC3726305 DOI: 10.1002/nbm.1650] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 10/20/2010] [Accepted: 10/31/2010] [Indexed: 05/30/2023]
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.
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Affiliation(s)
- Renuka Sriram
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | | | - Jitka Petrlova
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Haris Samardzic
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Ulrike Kreutzer
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Hongtao Xie
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - George A. Kaysen
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Jean F. Desreux
- Coordination and Radiochemistry, University of Liege, Liege, Belgium
| | - David Thonon
- Coordination and Radiochemistry, University of Liege, Liege, Belgium
| | | | - Martha Van Loan
- Nutrition Department, University of California Davis, Davis, CA, USA
| | - John C. Rutledge
- Division of Endocrinology, Clinical Nutrition and Vascular Medicine, Department of Internal Medicine, University of California Davis, Davis, CA, USA
| | - Michael N. Oda
- Children’s Hospital Oakland Research Institute, Oakland, CA, USA
| | - John C. Voss
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Thomas Jue
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
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26
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Morgan CR, Hebling CM, Rand KD, Stafford DW, Jorgenson JW, Engen JR. Conformational transitions in the membrane scaffold protein of phospholipid bilayer nanodiscs. Mol Cell Proteomics 2011; 10:M111.010876. [PMID: 21715319 DOI: 10.1074/mcp.m111.010876] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Phospholipid bilayer nanodiscs are model membrane systems that provide an environment where membrane proteins are highly stable and monodisperse without the use of detergents or liposomes. Nanodiscs consist of a discoidal phospholipid bilayer encircled by two copies of an amphipathic alpha helical membrane scaffold protein, which is modeled from apolipoprotein A-1. Hydrogen exchange mass spectrometry was used to probe the structure and dynamics of the scaffold protein in the presence and absence of lipid. On nanodisc self-assembly, the entire scaffold protein gained significant protection from exchange, consistent with a large, protein-wide, structural rearrangement. This protection was short-lived and the scaffold protein was highly deuterated within 2 h. Several regions of the scaffold protein, in both the lipid-free and lipid-associated states, displayed EX1 unfolding kinetics. The rapid deuteration of the scaffold protein and the presence of correlated unfolding events both indicate that nanodiscs are dynamic rather than rigid bodies in solution. This work provides a catalog of the expected scaffold protein peptic peptides in a nanodisc-hydrogen exchange mass spectrometry experiment and their deuterium uptake signatures, data that can be used as a benchmark to verify correct assembly and nanodisc structure. Such reference data will be useful control data for all hydrogen exchange mass spectrometry experiments involving nanodiscs in which transmembrane or lipid-associated proteins are the primary molecule(s) of interest.
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Affiliation(s)
- Christopher R Morgan
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
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27
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Petrlova J, Hong HS, Bricarello DA, Harishchandra G, Lorigan GA, Jin LW, Voss JC. A differential association of Apolipoprotein E isoforms with the amyloid-β oligomer in solution. Proteins 2011; 79:402-16. [PMID: 21069870 DOI: 10.1002/prot.22891] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The molecular pathogenesis of disorders arising from protein misfolding and aggregation is difficult to elucidate, involving a complex ensemble of intermediates, whose toxicity depends upon their state of progression along distinct processing pathways. To address the complex misfolding and aggregation that initiates the toxic cascade resulting in Alzheimer's disease (AD), we have developed a 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid spin-labeled amyloid-β (Aβ) peptide to observe its isoform-dependent interaction with the apoE protein. Although most individuals carry the E3 isoform of apoE, ∼15% of humans carry the E4 isoform, which is recognized as the most significant genetic determinant for Alzheimer's. ApoE is consistently associated with the amyloid plaque marker for AD. A vital question centers on the influence of the two predominant isoforms, E3 and E4, on Aβ peptide processing and hence Aβ toxicity. We used electron paramagnetic resonance (EPR) spectroscopy of incorporated spin labels to investigate the interaction of apoE with the toxic oligomeric species of Aβ in solution. EPR spectra of the spin-labeled side chain report on side chain and backbone dynamics as well as the spatial proximity of spins in an assembly. Our results indicate oligomer binding involves the C-terminal domain of apoE, with apoE3 reporting a much greater response through this conformational marker. Coupled with SPR binding measurements, apoE3 displays a higher affinity and capacity for the toxic Aβ oligomer. These findings support the hypothesis that apoE polymorphism and Alzheimer's risk can largely be attributed to the reduced ability of apoE4 to function as a clearance vehicle for the toxic form of Aβ.
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Affiliation(s)
- Jitka Petrlova
- Department of Biochemistry and Molecular Medicine, University of California Davis, California, USA
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28
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Raimondi S, Guglielmi F, Giorgetti S, Gaetano SD, Arciello A, Monti DM, Relini A, Nichino D, Doglia SM, Natalello A, Pucci P, Mangione P, Obici L, Merlini G, Stoppini M, Robustelli P, Tartaglia GG, Vendruscolo M, Dobson CM, Piccoli R, Bellotti V. Effects of the Known Pathogenic Mutations on the Aggregation Pathway of the Amyloidogenic Peptide of Apolipoprotein A-I. J Mol Biol 2011; 407:465-76. [DOI: 10.1016/j.jmb.2011.01.044] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 12/22/2010] [Accepted: 01/23/2011] [Indexed: 11/30/2022]
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29
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Lagerstedt JO, Cavigiolio G, Budamagunta MS, Pagani I, Voss JC, Oda MN. Structure of apolipoprotein A-I N terminus on nascent high density lipoproteins. J Biol Chem 2010; 286:2966-75. [PMID: 21047795 DOI: 10.1074/jbc.m110.163097] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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 the apoA-I structure-function in cholesterol metabolism, the conformation of the apoA-I 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 the 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 the adaptation of apoA-I to the particle size of HDL.
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Affiliation(s)
- Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
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30
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Tanaka M, Dhanasekaran P, Nguyen D, Nickel M, Takechi Y, Lund-Katz S, Phillips MC, Saito H. Influence of N-terminal helix bundle stability on the lipid-binding properties of human apolipoprotein A-I. Biochim Biophys Acta Mol Cell Biol Lipids 2010; 1811:25-30. [PMID: 21040803 DOI: 10.1016/j.bbalip.2010.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 10/19/2010] [Accepted: 10/24/2010] [Indexed: 11/26/2022]
Abstract
As the principal component of high-density lipoprotein (HDL), apolipoprotein (apo) A-I plays essential roles in lipid transport and metabolism. Because of its intrinsic conformational plasticity and flexibility, the molecular details of the tertiary structure of lipid-free apoA-I have not been fully elucidated. Previously, we demonstrated that the stability of the N-terminal helix bundle structure is modulated by proline substitution at the most hydrophobic region (residues around Y18) in the N-terminal domain. Here we examine the effect of proline substitution at S55 located in another relatively hydrophobic region compared to most of the helix bundle domain to elucidate the influences on the helix bundle structure and lipid interaction. Fluorescence measurements revealed that the S55P mutation had a modest effect on the stability of the bundle structure, indicating that residues around S55 are not pivotally involved in the helix bundle formation, in contrast to the insertion of proline at position 18. Although truncation of the C-terminal domain (Δ190-243) diminishes the lipid binding of apoA-I molecule, the mutation S55P in addition to the C-terminal truncation (S55P/Δ190-243) restored the lipid binding, suggesting that the S55P mutation causes a partial unfolding of the helix bundle to facilitate lipid binding. Furthermore, additional proline substitution at Y18 (Y18P/S55P/Δ190-243), which leads to a drastic unfolding of the helix bundle structure, yielded a greater lipid binding ability. Thus, proline substitutions in the N-terminal domain of apoA-I that destabilized the helix bundle promoted lipid solubilization. These results suggest that not only the hydrophobic C-terminal helical domain but also the stability of the N-terminal helix bundle in apoA-I are important modulators of the spontaneous solubilization of membrane lipids by apoA-I, a process that leads to the generation of nascent HDL particles.
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Affiliation(s)
- Masafumi Tanaka
- Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan.
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31
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Jones MK, Zhang L, Catte A, Li L, Oda MN, Ren G, Segrest JP. Assessment of the validity of the double superhelix model for reconstituted high density lipoproteins: a combined computational-experimental approach. J Biol Chem 2010; 285:41161-71. [PMID: 20974855 DOI: 10.1074/jbc.m110.187799] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
For several decades, the standard model for high density lipoprotein (HDL) particles reconstituted from apolipoprotein A-I (apoA-I) and phospholipid (apoA-I/HDL) has been a discoidal particle ∼100 Å in diameter and the thickness of a phospholipid bilayer. Recently, Wu et al. (Wu, Z., Gogonea, V., Lee, X., Wagner, M. A., Li, X. M., Huang, Y., Undurti, A., May, R. P., Haertlein, M., Moulin, M., Gutsche, I., Zaccai, G., Didonato, J. A., and Hazen, S. L. (2009) J. Biol. Chem. 284, 36605-36619) used small angle neutron scattering to develop a new model they termed double superhelix (DSH) apoA-I that is dramatically different from the standard model. Their model possesses an open helical shape that wraps around a prolate ellipsoidal type I hexagonal lyotropic liquid crystalline phase. Here, we used three independent approaches, molecular dynamics, EM tomography, and fluorescence resonance energy transfer spectroscopy (FRET) to assess the validity of the DSH model. (i) By using molecular dynamics, two different approaches, all-atom simulated annealing and coarse-grained simulation, show that initial ellipsoidal DSH particles rapidly collapse to discoidal bilayer structures. These results suggest that, compatible with current knowledge of lipid phase diagrams, apoA-I cannot stabilize hexagonal I phase particles of phospholipid. (ii) By using EM, two different approaches, negative stain and cryo-EM tomography, show that reconstituted apoA-I/HDL particles are discoidal in shape. (iii) By using FRET, reconstituted apoA-I/HDL particles show a 28-34-Å intermolecular separation between terminal domain residues 40 and 240, a distance that is incompatible with the dimensions of the DSH model. Therefore, we suggest that, although novel, the DSH model is energetically unfavorable and not likely to be correct. Rather, we conclude that all evidence supports the likelihood that reconstituted apoA-I/HDL particles, in general, are discoidal in shape.
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Affiliation(s)
- Martin K Jones
- Department of Medicine and Atherosclerosis Research Unit, University of Alabama, Birmingham, Alabama 35294, USA
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Weers PMM, Patel AB, Wan LCP, Guigard E, Kay CM, Hafiane A, McPherson R, Marcel YL, Kiss RS. Novel N-terminal mutation of human apolipoprotein A-I reduces self-association and impairs LCAT activation. J Lipid Res 2010; 52:35-44. [PMID: 20884842 PMCID: PMC2999918 DOI: 10.1194/jlr.m007500] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We have identified a novel mutation in apoA-I (serine 36 to alanine; S36A) in a human subject with severe hypoalphalipoproteinemia. The mutation is located in the N-terminal region of the protein, which has been implicated in several functions, including lipid binding and lecithin:cholesterol acyltransferase (LCAT) activity. In the present study, the S36A protein was produced recombinantly and characterized both structurally and functionally. While the helical content of the mutant protein was lower compared with wild-type (WT) apoA-I, it retained its helical character. The protein stability, measured as the resistance to guanidine-induced denaturation, decreased significantly. Interestingly, native gel electrophoresis, cross-linking, and sedimentation equilibrium analysis showed that the S36A mutant was primarily present as a monomer, notably different from the WT protein, which showed considerable oligomeric forms. Although the ability of S36A apoA-I to solubilize phosphatidylcholine vesicles and bind to lipoprotein surfaces was not altered, a significantly impaired LCAT activation compared with the WT protein was observed. These results implicate a region around S36 in apoA-I self-association, independent of the intact C terminus. Furthermore, the region around S36 in the N-terminus of human apoA-I is necessary for LCAT activation.
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Affiliation(s)
- Paul M M Weers
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, CA, USA
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Varkey J, Isas JM, Mizuno N, Jensen MB, Bhatia VK, Jao CC, Petrlova J, Voss JC, Stamou DG, Steven AC, Langen R. Membrane curvature induction and tubulation are common features of synucleins and apolipoproteins. J Biol Chem 2010; 285:32486-93. [PMID: 20693280 DOI: 10.1074/jbc.m110.139576] [Citation(s) in RCA: 236] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synucleins and apolipoproteins have been implicated in a number of membrane and lipid trafficking events. Lipid interaction for both types of proteins is mediated by 11 amino acid repeats that form amphipathic helices. This similarity suggests that synucleins and apolipoproteins might have comparable effects on lipid membranes, but this has not been shown directly. Here, we find that α-synuclein, β-synuclein, and apolipoprotein A-1 have the conserved functional ability to induce membrane curvature and to convert large vesicles into highly curved membrane tubules and vesicles. The resulting structures are morphologically similar to those generated by amphiphysin, a curvature-inducing protein involved in endocytosis. Unlike amphiphysin, however, synucleins and apolipoproteins do not require any scaffolding domains and curvature induction is mediated by the membrane insertion and wedging of amphipathic helices alone. Moreover, we frequently observed that α-synuclein caused membrane structures that had the appearance of nascent budding vesicles. The ability to function as a minimal machinery for vesicle budding agrees well with recent findings that α-synuclein plays a role in vesicle trafficking and enhances endocytosis. Induction of membrane curvature must be under strict regulation in vivo; however, as we find it can also cause disruption of membrane integrity. Because the degree of membrane curvature induction depends on the concerted action of multiple proteins, controlling the local protein density of tubulating proteins may be important. How cellular safeguarding mechanisms prevent such potentially toxic events and whether they go awry in disease remains to be determined.
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Affiliation(s)
- Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, USA
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Bhat S, Sorci-Thomas MG, Calabresi L, Samuel MP, Thomas MJ. Conformation of dimeric apolipoprotein A-I milano on recombinant lipoprotein particles. Biochemistry 2010; 49:5213-24. [PMID: 20524691 DOI: 10.1021/bi1003734] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Apolipoprotein A-I Milano (apoA-I(Milano)) is a naturally occurring human mutation of wild-type apolipoprotein A-I (apoA-I(WT)) having cystine substituted for arginine(173). Two molecules of apo-I(WT) form disks with phospholipid having a defined relationship between the apoA-I(WT) molecules. ApoA-I(Milano) forms cystine homodimers that would not allow the protein to adopt the conformation reported for apoA-I(WT). The conformational constraints for dimeric apoA-I(Milano) recombinant high-density lipoprotein (rHDL) disks made with phospholipid were deduced from a combination of chemical cross-linking and mass spectrometry. Lysine-selective homobifunctional cross-linkers were reacted with homogeneous rHDL having diameters of 78 and 125 A. After reduction, cross-linked apoA-I(Milano) was separated from monomeric apoprotein by gel electrophoresis and then subjected to in-gel trypsin digest. Cross-linked peptides were confirmed by MS/MS sequencing. The cross-links provided distance constraints that were used to refine models of lipid-bound dimeric apoA-I(Milano). These studies suggest that a single dimeric apoA-I(Milano) on 78 A diameter rHDL girdles the edge of a phospholipid disk assuming a "belt" conformation similar to the "belt" region of apoA-I(WT) on rHDL. However, the C-terminal end of dimeric apoA-I(Milano) wraps around the periphery of the particle to shield the fatty acid chains from water rather than folding back onto the "belt" as does apoA-I(WT). The two apoA-I(Milano) dimers on a 125 A diameter rHDL do not encircle the periphery of a phospholipid disk but appear to reside on the surface of a laminar micelle.
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Affiliation(s)
- Shaila Bhat
- Department of Pathology, Center for Lipid Science, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
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35
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Smoak KA, Aloor JJ, Madenspacher J, Merrick BA, Collins JB, Zhu X, Cavigiolio G, Oda MN, Parks JS, Fessler MB. Myeloid differentiation primary response protein 88 couples reverse cholesterol transport to inflammation. Cell Metab 2010; 11:493-502. [PMID: 20519121 PMCID: PMC3091482 DOI: 10.1016/j.cmet.2010.04.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 02/03/2010] [Accepted: 04/05/2010] [Indexed: 02/06/2023]
Abstract
Crosstalk exists in mammalian cells between cholesterol trafficking and innate immune signaling. Apolipoprotein A-I (apoA-I), a serum apolipoprotein that induces antiatherogenic efflux of macrophage cholesterol, is widely described as anti-inflammatory because it neutralizes bacterial lipopolysaccharide. Conversely, lipopolysaccharide-induced inflammation is proatherogenic. However, whether innate immunity plays an endogenous, physiological role in host cholesterol homeostasis in the absence of infection is undetermined. We report that apoA-I signals in the macrophage through Toll-like receptor (TLR)2, TLR4, and CD14, utilizing myeloid differentiation primary response protein 88 (MyD88)-dependent and -independent pathways, to activate nuclear factor-kappaB and induce cytokines. MyD88 plays a critical role in reverse cholesterol transport in vitro and in vivo, in part through promoting ATP-binding cassette A1 transporter upregulation. Taken together, this work identifies apoA-I as an endogenous stimulus of innate immunity that couples cholesterol trafficking to inflammation through MyD88 and identifies innate immunity as a physiologic signal in cholesterol homeostasis.
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Affiliation(s)
- Kathleen A. Smoak
- Laboratory of Respiratory Biology, NIEHS, Research Triangle Park, NC 27709 U.S.A
| | - Jim J. Aloor
- Laboratory of Respiratory Biology, NIEHS, Research Triangle Park, NC 27709 U.S.A
| | | | - B. Alex Merrick
- Laboratory of Respiratory Biology, NIEHS, Research Triangle Park, NC 27709 U.S.A
| | | | - Xuewei Zhu
- Department of Pathology/Section on Lipid Sciences, Wake Forest University Health Sciences, Winston-Salem, NC 27157 U.S.A
| | | | - Michael N. Oda
- Children's Hospital Oakland Research Institute, Oakland, CA 94609 U.S.A
| | - John S. Parks
- Department of Pathology/Section on Lipid Sciences, Wake Forest University Health Sciences, Winston-Salem, NC 27157 U.S.A
| | - Michael B. Fessler
- Laboratory of Respiratory Biology, NIEHS, Research Triangle Park, NC 27709 U.S.A
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Cavigiolio G, Geier EG, Shao B, Heinecke JW, Oda MN. Exchange of apolipoprotein A-I between lipid-associated and lipid-free states: a potential target for oxidative generation of dysfunctional high density lipoproteins. J Biol Chem 2010; 285:18847-57. [PMID: 20385548 DOI: 10.1074/jbc.m109.098434] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
An important event in cholesterol metabolism is the efflux of cellular cholesterol by apolipoprotein A-I (apoA-I), the major protein of high density lipoproteins (HDL). Lipid-free apoA-I is the preferred substrate for ATP-binding cassette A1, which promotes cholesterol efflux from macrophage foam cells in the arterial wall. However, the vast majority of apoA-I in plasma is associated with HDL, and the mechanisms for the generation of lipid-free apoA-I remain poorly understood. In the current study, we used fluorescently labeled apoA-I that exhibits a distinct fluorescence emission spectrum when in different states of lipid association to establish the kinetics of apoA-I transition between the lipid-associated and lipid-free states. This approach characterized the spontaneous and rapid exchange of apoA-I between the lipid-associated and lipid-free states. In contrast, the kinetics of apoA-I exchange were significantly reduced when apoA-I on HDL was cross-linked with a bi-functional reagent or oxidized by myeloperoxidase. Our observations support the hypothesis that oxidative damage to apoA-I by myeloperoxidase limits the ability of apoA-I to be liberated in a lipid-free form from HDL. This impairment of apoA-I exchange reaction may be a trait of dysfunctional HDL contributing to reduced ATP-binding cassette A1-mediated cholesterol efflux and atherosclerosis.
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Affiliation(s)
- Giorgio Cavigiolio
- Children's Hospital Oakland Research Institute, Oakland, California 94609, USA
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37
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Shao B, Pennathur S, Pagani I, Oda MN, Witztum JL, Oram JF, Heinecke JW. Modifying apolipoprotein A-I by malondialdehyde, but not by an array of other reactive carbonyls, blocks cholesterol efflux by the ABCA1 pathway. J Biol Chem 2010; 285:18473-84. [PMID: 20378541 DOI: 10.1074/jbc.m110.118182] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Dysfunctional high density lipoprotein (HDL) is implicated in the pathogenesis of cardiovascular disease, but the underlying pathways remain poorly understood. One potential mechanism involves covalent modification by reactive carbonyls of apolipoprotein A-I (apoA-I), the major HDL protein. We therefore determined whether carbonyls resulting from lipid peroxidation (malondialdehyde (MDA) and hydroxynonenal) or carbohydrate oxidation (glycolaldehyde, glyoxal, and methylglyoxal) covalently modify lipid-free apoA-I and inhibit its ability to promote cellular cholesterol efflux by the ABCA1 pathway. MDA markedly impaired the ABCA1 activity of apoA-I. In striking contrast, none of the other four carbonyls were effective. Liquid chromatography-electrospray ionization-tandem mass spectrometry of MDA-modified apoA-I revealed that Lys residues at specific sites had been modified. The chief adducts were MDA-Lys and a Lys-MDA-Lys cross-link. Lys residues in the C terminus of apoA-I were targeted for cross-linking in high yield, and this process may hinder the interaction of apoA-I with lipids and ABCA1, two key steps in reverse cholesterol transport. Moreover, levels of MDA-protein adducts were elevated in HDL isolated from human atherosclerotic lesions, suggesting that lipid peroxidation might render HDL dysfunctional in vivo. Taken together, our observations indicate that MDA damages apoA-I by a pathway that generates lysine adducts at specific sites on the protein. Such damage may facilitate the formation of macrophage foam cells by impairing cholesterol efflux by the ABCA1 pathway.
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Affiliation(s)
- Baohai Shao
- Department of Medicine, University of Washington, Seattle, Washington 98195, USA.
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38
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Koyama M, Tanaka M, Dhanasekaran P, Lund-Katz S, Phillips MC, Saito H. Interaction between the N- and C-terminal domains modulates the stability and lipid binding of apolipoprotein A-I. Biochemistry 2010; 48:2529-37. [PMID: 19239199 DOI: 10.1021/bi802317v] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The tertiary structures of human and mouse apolipoprotein A-I (apoA-I) are comprised of an N-terminal helix bundle and a separate C-terminal domain. To define the possible intramolecular interaction between the N- and the C-terminal domains, we examined the effects on protein stability and lipid-binding properties of exchanging either the C-terminal domain or helix between human and mouse apoA-I. Chemical denaturation experiments demonstrated that replacement of the C-terminal domain or helical segment in human apoA-I with the mouse counterparts largely destabilizes the N-terminal helix bundle. Removal of the C-terminal domain or alpha-helix in human apoA-I had a similar effect on the destabilization of the helix bundle against urea denaturation, indicating that the C-terminal helical segment mainly contributes to stabilizing the N-terminal helix bundle structure in the apoA-I molecule. Consistent with this, KI quenching experiments indicated that removal or replacement of the C-terminal domain or helix in human apoA-I causes Trp residues in the N-terminal domain to become exposed to solvent. Measurements of the heats of binding to egg phosphatidylcholine (PC) vesicles and the kinetics of solubilization of dimyristoyl PC vesicles demonstrated that the destabilized human N-terminal helix bundle can strongly interact with lipids without the hydrophobic C-terminal helix. In addition, site-specific labeling of the N- and C-terminal helices by acrylodan to probe the conformational stability and the spatial proximity of the two domains indicated that the C-terminal helix is located near the N-terminal helix bundle, leading to a relatively less solvent-exposed, more organized conformation of the C-terminal domain. Taken together, these results suggest that interaction between the N- and C-terminal tertiary structure domains in apoA-I modulates the stability and lipid-binding properties of the N-terminal helix bundle.
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Affiliation(s)
- Mao Koyama
- Department of Biophysical Chemistry, Kobe Pharmaceutical University, 4-19-1 Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan
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Shao B, Tang C, Heinecke JW, Oram JF. Oxidation of apolipoprotein A-I by myeloperoxidase impairs the initial interactions with ABCA1 required for signaling and cholesterol export. J Lipid Res 2010; 51:1849-58. [PMID: 20064972 DOI: 10.1194/jlr.m004085] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A key cardioprotective effect of high-density lipoprotein involves the interaction of its major protein, apolipoprotein A-I (apoA-I) with ATP-binding cassette transporter A1 (ABCA1), a macrophage cholesterol exporter. ApoA-I is thought to remove cholesterol from macrophages by a cascade of events. First it binds directly to ABCA1, activating signaling pathways, and then it binds to and solubilizes lipid domains generated by ABCA1. HDL isolated from human atherosclerotic lesions and blood of subjects with established coronary artery disease contains elevated levels of 3-chlorotyrosine and 3-nitrotyrosine, two characteristic products of myeloperoxidase (MPO), a heme protein secreted by macrophages. Here we show that chlorination (but not nitration) of apoA-I by the MPO pathway impairs its ability to interact directly with ABCA1, to activate the Janus kinase 2 signaling pathway, and to promote efflux of cellular cholesterol. In contrast, oxidation of apoA-I has little effect on its ability to stabilize ABCA1 protein or to solubilize phospholipids. Our results indicate that chlorination of apoA-I by the MPO pathway selectively inhibits two critical early events in cholesterol efflux: (1) the binding of apoA-I to ABCA1 and (2) the activation of a key signaling pathway. Therefore, oxidation of apoA-I in the artery wall by MPO-generated chlorinating intermediates may contribute to atherogenesis by impairing cholesterol efflux from macrophages.
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Affiliation(s)
- Baohai Shao
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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40
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Helical structure and stability in human apolipoprotein A-I by hydrogen exchange and mass spectrometry. Proc Natl Acad Sci U S A 2009; 106:19005-10. [PMID: 19850866 DOI: 10.1073/pnas.0909708106] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Apolipoprotein A-I (apoA-I) stabilizes anti-atherogenic high density lipoprotein particles (HDL) in the circulation and governs their biogenesis, metabolism, and functional interactions. To decipher these important structure-function relationships, it will be necessary to understand the structure, stability, and plasticity of the apoA-I molecule. Biophysical studies show that lipid-free apoA-I contains a large amount of alpha-helical structure but the location of this structure and its properties are not established. We used hydrogen-deuterium exchange coupled with a fragmentation-separation method and mass spectrometric analysis to study human lipid-free apoA-I in its physiologically pertinent monomeric form. The acquisition of approximately 100 overlapping peptide fragments that redundantly cover the 243-residue apoA-I polypeptide made it possible to define the positions and stabilities of helical segments and to draw inferences about their interactions and dynamic properties. Residues 7-44, 54-65, 70-78, 81-115, and 147-178 form alpha-helices, accounting for a helical content of 48 +/- 3%, in agreement with circular dichroism measurements (49%). At 3 to 5 kcal/mol in free energy of stabilization, the helices are far more stable than could be achieved in isolation, indicating mutually stabilizing helix bundle interactions. However the helical structure is dynamic, unfolding and refolding in seconds, allowing facile apoA-I reorganization during HDL particle formation and remodeling.
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41
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Narayanaswami V, Kiss RS, Weers PMM. The helix bundle: a reversible lipid binding motif. Comp Biochem Physiol A Mol Integr Physiol 2009; 155:123-33. [PMID: 19770066 DOI: 10.1016/j.cbpa.2009.09.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 09/09/2009] [Accepted: 09/11/2009] [Indexed: 01/01/2023]
Abstract
Apolipoproteins are the protein components of lipoproteins that have the innate ability to inter convert between a lipid-free and a lipid-bound form in a facile manner, a remarkable property conferred by the helix bundle motif. Composed of a series of four or five amphipathic alpha-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the alpha-helices in the protein interior in the lipid-free state. A conformational switch then permits helix-helix interactions to be substituted by helix-lipid interactions upon lipid binding interaction. This review compares the apolipoprotein high-resolution structures and the factors that trigger this switch in insect apolipophorin III and the mammalian apolipoproteins, apolipoprotein E and apolipoprotein A-I, pointing out the commonalities and key differences in the mode of lipid interaction. Further insights into the lipid-bound conformation of apolipoproteins are required to fully understand their functional role under physiological conditions.
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Affiliation(s)
- Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach CA 90840, USA
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42
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Jones MK, Catte A, Patterson JC, Gu F, Chen J, Li L, Segrest JP. Thermal stability of apolipoprotein A-I in high-density lipoproteins by molecular dynamics. Biophys J 2009; 96:354-71. [PMID: 19167289 DOI: 10.1016/j.bpj.2008.09.041] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Accepted: 09/22/2008] [Indexed: 02/06/2023] Open
Abstract
Apolipoprotein (apo) A-I is an unusually flexible protein whose lipid-associated structure is poorly understood. Thermal denaturation, which is used to measure the global helix stability of high-density lipoprotein (HDL)-associated apoA-I, provides no information about local helix stability. Here we report the use of temperature jump molecular dynamics (MD) simulations to scan the per-residue helix stability of apoA-I in phospholipid-rich HDL. When three 20 ns MD simulations were performed at 500 K on each of two particles created by MD simulations at 310 K, bilayers remained intact but expanded by 40%, and total apoA-I helicity decreased from 95% to 72%. Of significance, the conformations of the overlapping N- and C-terminal domains of apoA-I in the particles were unusually mobile, exposing hydrocarbon regions of the phospholipid to solvent; a lack of buried interhelical salt bridges in the terminal domains correlated with increased mobility. Nondenaturing gradient gels show that 40% expansion of the phospholipid surface of 100:2 particles by addition of palmitoyloleoylphosphatidylcholine exceeds the threshold of particle stability. As a unifying hypothesis, we propose that the terminal domains of apoA-I are phospholipid concentration-sensitive molecular triggers for fusion/remodeling of HDL particles. Since HDL remodeling is necessary for cholesterol transport, our model for remodeling has substantial biomedical implications.
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Affiliation(s)
- Martin K Jones
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
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Tanaka M, Tanaka T, Ohta S, Kawakami T, Konno H, Akaji K, Aimoto S, Saito H. Evaluation of lipid-binding properties of the N-terminal helical segments in human apolipoprotein A-I using fragment peptides. J Pept Sci 2009; 15:36-42. [DOI: 10.1002/psc.1092] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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44
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Hatters DM, Voss JC, Budamagunta MS, Newhouse YN, Weisgraber KH. Insight on the molecular envelope of lipid-bound apolipoprotein E from electron paramagnetic resonance spectroscopy. J Mol Biol 2008; 386:261-71. [PMID: 19124026 DOI: 10.1016/j.jmb.2008.12.040] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 12/04/2008] [Accepted: 12/10/2008] [Indexed: 10/21/2022]
Abstract
Although a high-resolution X-ray structure for the N-terminal domain of apolipoprotein E (apoE) in the lipid-free state has been solved, our knowledge of the structure of full-length apoE in a lipid-bound state is limited to an X-ray model fitting a molecular envelope at 10-A resolution. To add molecular detail to the molecular envelope, we used cysteine mutagenesis to incorporate spin labels for analysis with electron paramagnetic resonance (EPR) spectroscopy. Twelve cysteine residues were introduced singly and in pairs at unique locations throughout apoE4 and labeled with an EPR spin probe. The labeled apoE4 was combined with dipalmitoylphosphatidylcholine, the particles were purified, and spectra were determined for 24 combinations (single and double) of the cysteine mutants. Data on the conformation, mobility, distance, and surface exposure of regions revealed by the cysteine probes were modeled into the molecular envelope of apoE bound to dipalmitoylphosphatidylcholine that had been determined by X-ray analysis. This EPR model of apoE in a native lipid-bound state validates the structural model derived from X-ray analysis and provides additional insight into apoE structure-function relationships.
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Affiliation(s)
- Danny M Hatters
- Gladstone Institutes of Cardiovascular and Neurological Diseases, 1650 Owens Street, San Francisco, CA 94158, USA
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45
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Tubb MR, Silva RAGD, Fang J, Tso P, Davidson WS. A three-dimensional homology model of lipid-free apolipoprotein A-IV using cross-linking and mass spectrometry. J Biol Chem 2008; 283:17314-23. [PMID: 18430727 PMCID: PMC2427326 DOI: 10.1074/jbc.m800036200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Revised: 04/10/2008] [Indexed: 11/06/2022] Open
Abstract
Human apolipoprotein A-IV (apoA-IV) is a 46-kDa exchangeable plasma protein with many proposed functions. It is involved in chylomicron assembly and secretion, protection from atherosclerosis through a variety of mechanisms, and inhibition of food intake. There is little structural basis for these proposed functions due to the lack of a solved three-dimensional structure of the protein by x-ray crystallography or NMR. Based on previous studies, we hypothesized that lipid-free apoA-IV exists in a helical bundle, like other apolipoprotein family members and that regions near the N and C termini may interact. Utilizing a homobifunctional lysine cross-linking agent, we identified 21 intramolecular cross-links by mass spectrometry. These cross-links were used to constrain the building of a sequence threaded homology model using the I-TASSER server. Our results indicate that lipid-free apoA-IV does indeed exist as a complex helical bundle with the N and C termini in close proximity. This first structural model of lipid-free apoA-IV should prove useful for designing studies aimed at understanding how apoA-IV interacts with lipids and possibly with unknown protein partners.
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Affiliation(s)
- Matthew R Tubb
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237, USA
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46
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Thomas MJ, Bhat S, Sorci-Thomas MG. Three-dimensional models of HDL apoA-I: implications for its assembly and function. J Lipid Res 2008; 49:1875-83. [PMID: 18515783 DOI: 10.1194/jlr.r800010-jlr200] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The purpose of this review is to highlight recent advances toward the refinement of a three-dimensional structure for lipid-bound apolipoprotein A-I (apoA-I) on recombinant HDL. Recently, X-ray crystallography has yielded a new structure for full-length, lipid-free apoA-I. Although this approach has not yet been successful in solving the three-dimensional structure of lipid-bound apoA-I, analysis of the X-ray structures has been of immense help in the interpretation of structural data obtained from other methods that yield structural information. Recent studies emphasize the use of mass spectrometry to unambiguously identify cross-linked peptides or to quantify solvent accessibility using hydrogen-deuterium exchange. The combination of mass spectrometry, molecular modeling, molecular dynamic analysis, and small-angle X-ray diffraction has provided additional structural information on apoA-I folding that complements previous approaches.
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Affiliation(s)
- Michael J Thomas
- Department of Biochemistry, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
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47
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Vaisar T, Shao B, Green PS, Oda MN, Oram JF, Heinecke JW. Myeloperoxidase and inflammatory proteins: pathways for generating dysfunctional high-density lipoprotein in humans. Curr Atheroscler Rep 2008; 9:417-24. [PMID: 18001626 DOI: 10.1007/s11883-007-0054-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
High-density lipoprotein (HDL) inhibits atherosclerosis by removing cholesterol from artery wall macrophages. Additionally, HDL is anti-inflammatory in animal studies, suggesting that this property might also be important for its cardioprotective effects. Recent studies in subjects with established cardiovascular disease (CVD) demonstrate that myeloperoxidase targets HDL for oxidation and blocks the lipoprotein's ability to remove excess cholesterol from cells, raising the possibility that the enzyme provides a specific mechanism for generating dysfunctional HDL in humans. Shotgun proteomic analysis of HDL identified multiple complement regulatory proteins, protease inhibitors, and acute-phase response proteins, supporting a central role for HDL in inflammation. Mass spectrometry and biochemical analyses demonstrated that HDL(3) from CVD subjects was selectively enriched in apolipoprotein E, suggesting that it carries a unique cargo of proteins in humans with clinically significant CVD. Thus, oxidative modifications to HDL and changes in its protein composition might be useful biomarkers-and perhaps mediators-of CVD.
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Affiliation(s)
- Tomás Vaisar
- Department of Medicine, HSB-BB512, Box 356426, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
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48
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Lagerstedt JO, Cavigiolio G, Roberts LM, Hong HS, Jin LW, Fitzgerald P, Oda MN, Voss JC. Mapping the structural transition in an amyloidogenic apolipoprotein A-I. Biochemistry 2007; 46:9693-9. [PMID: 17665932 PMCID: PMC3650831 DOI: 10.1021/bi7005493] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The single amino acid mutation G26R in human apolipoprotein A-I (apoA-IIOWA) leads to the formation of beta-secondary structure rich amyloid fibrils in vivo. Here we show that full-length apoA-IIOWA has a decreased lipid-binding capability, an increased amino-terminal sensitivity to protease, and a propensity to form annular protofibrils visible by electron microscopy. The molecular basis for the conversion of apolipoprotein A-I to a proamyloidogenic form was examined by electron paramagnetic resonance spectroscopy. Our recent findings [Lagerstedt, J. O., Budamagunta, M. S., Oda, M. N., and Voss, J. C. (2007) J. Biol. Chem. 282, 9143-9149] indicate that Gly26 in the native apoprotein separates a preceding beta-strand structure (residues 20-25) from a downstream largely alpha-helical region. The current study demonstrates that the G26R variant promotes a structural transition of positions 27-56 to a mixture of coil and beta-strand secondary structure. Microscopy and staining by amyloidophilic dyes suggest that this alteration extends throughout the protein within 1 week of incubation in vitro, leading to insoluble aggregates of distinct morphology. The severe consequences of the Iowa mutation likely arise from the combination of losing the contribution of the native Gly residue in terminating beta-strand propagation and the promotion of beta-structure when an Arg is introduced adjacent to the succeeding residue of identical charge and size, Arg27.
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Affiliation(s)
- Jens O. Lagerstedt
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616
- Department of Internal Medicine, University of California, Davis, CA 95616
| | - Giorgio Cavigiolio
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616
| | - Linda M. Roberts
- Department of Chemistry California State University, Sacramento, CA 95819
| | - Hyun-Seok Hong
- Department of Pathology, University of California, Davis, CA 95616
| | - Lee-Way Jin
- Department of Pathology, University of California, Davis, CA 95616
| | - Paul Fitzgerald
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616
| | - Michael N. Oda
- Children’s Hospital Oakland Research Institute, Oakland, CA 94609
| | - John C. Voss
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616
- Corresponding author: Tel: +1 530 754 7583; Fax: +1 530 752 3516;
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49
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Bhat S, Sorci-Thomas MG, Tuladhar R, Samuel MP, Thomas MJ. Conformational adaptation of apolipoprotein A-I to discretely sized phospholipid complexes. Biochemistry 2007; 46:7811-21. [PMID: 17563120 PMCID: PMC2553278 DOI: 10.1021/bi700384t] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The conformational constraints for apoA-I bound to recombinant phospholipid complexes (rHDL) were attained from a combination of chemical cross-linking and mass spectrometry. Molecular distances were then used to refine models of lipid-bound apoA-I on both 80 and 96 A diameter rHDL particles. To obtain molecular constraints on the protein bound to phospholipid complexes, three different lysine-selective homo-bifunctional cross-linkers with increasing spacer arm lengths (i.e., 7.7, 12.0, and 16.1 A) were reacted with purified, homogeneous recombinant 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) apoA-I rHDL complexes of each diameter. Cross-linked dimeric apoA-I products were separated from monomeric apoprotein using 12% SDS-PAGE, then subjected to in-gel trypsin digest, and identified by MS/MS sequencing. These studies aid in the refinement of our previously published molecular model of two apoA-I molecules bound to approximately 150 molecules of POPC and suggest that the protein hydrophobic interactions at the N- and C-terminal domains decrease as the number of phospholipid molecules or "lipidation state" of apoA-I increases. Thus, it appears that these incremental changes in the interaction between the N- and C-terminal ends of apoA-I stabilize its tertiary conformation in the lipid-free state as well as allowing it to unfold and sequester discrete amounts of phospholipid molecules.
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Affiliation(s)
- Shaila Bhat
- Department of Pathology, Center for Lipid Science, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Mary G Sorci-Thomas
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
- Department of Pathology, Center for Lipid Science, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Rubina Tuladhar
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Michael P. Samuel
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Michael J. Thomas
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
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50
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Davidson WS, Thompson TB. The structure of apolipoprotein A-I in high density lipoproteins. J Biol Chem 2007; 282:22249-53. [PMID: 17526499 DOI: 10.1074/jbc.r700014200] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, OH 45237, USA.
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