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Jiménez-Osorio AS, Carreón-Torres E, Correa-Solís E, Ángel-García J, Arias-Rico J, Jiménez-Garza O, Morales-Castillejos L, Díaz-Zuleta HA, Baltazar-Tellez RM, Sánchez-Padilla ML, Flores-Chávez OR, Estrada-Luna D. Inflammation and Oxidative Stress Induced by Obesity, Gestational Diabetes, and Preeclampsia in Pregnancy: Role of High-Density Lipoproteins as Vectors for Bioactive Compounds. Antioxidants (Basel) 2023; 12:1894. [PMID: 37891973 PMCID: PMC10604737 DOI: 10.3390/antiox12101894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/05/2023] [Accepted: 10/13/2023] [Indexed: 10/29/2023] Open
Abstract
Inflammation and oxidative stress are essential components in a myriad of pathogenic entities that lead to metabolic and chronic diseases. Moreover, inflammation in its different phases is necessary for the initiation and maintenance of a healthy pregnancy. Therefore, an equilibrium between a necessary/pathologic level of inflammation and oxidative stress during pregnancy is needed to avoid disease development. High-density lipoproteins (HDL) are important for a healthy pregnancy and a good neonatal outcome. Their role in fetal development during challenging situations is vital for maintaining the equilibrium. However, in certain conditions, such as obesity, diabetes, and other cardiovascular diseases, it has been observed that HDL loses its protective properties, becoming dysfunctional. Bioactive compounds have been widely studied as mediators of inflammation and oxidative stress in different diseases, but their mechanisms of action are still unknown. Nonetheless, these agents, which are obtained from functional foods, increase the concentration of HDL, TRC, and antioxidant activity. Therefore, this review first summarizes several mechanisms of HDL participation in the equilibrium between inflammation and oxidative stress. Second, it gives an insight into how HDL may act as a vector for bioactive compounds. Third, it describes the relationships between the inflammation process in pregnancy and HDL activity. Consequently, different databases were used, including MEDLINE, PubMed, and Scopus, where scientific articles published in the English language up to 2023 were identified.
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Affiliation(s)
- Angélica Saraí Jiménez-Osorio
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - Elizabeth Carreón-Torres
- Department of Molecular Biology, Instituto Nacional de Cardiología “Ignacio Chávez”, Juan Badiano 1, Sección XVI, Tlalpan, Mexico City 14080, Mexico;
| | - Emmanuel Correa-Solís
- Instituto de Farmacobiología, Universidad de la Cañada, Carretera Teotitlán-San Antonio Nanahuatipán Km 1.7 s/n., Paraje Titlacuatitla, Teotitlán de Flores Magón 68540, Oaxaca, Mexico;
| | - Julieta Ángel-García
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - José Arias-Rico
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - Octavio Jiménez-Garza
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - Lizbeth Morales-Castillejos
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - Hugo Alexander Díaz-Zuleta
- Facultad de Ciencias de la Salud, Universidad de Ciencias Aplicadas y Ambientales, Cl. 222 #54-21, Bogotá 111166, Colombia;
| | - Rosa María Baltazar-Tellez
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - María Luisa Sánchez-Padilla
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - Olga Rocío Flores-Chávez
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
| | - Diego Estrada-Luna
- Área Académica de Enfermería, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado Hida go, Circuito Ex Hacienda La Concepción S/N, Carretera Pachuca-Actopan, San Agustín Tlaxiaca 42160, Hidalgo, Mexico; (A.S.J.-O.); (J.Á.-G.); (J.A.-R.); (O.J.-G.); (L.M.-C.); (R.M.B.-T.); (M.L.S.-P.); (O.R.F.-C.)
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2
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Chen R, Chen Q, Zheng J, Zeng Z, Chen M, Li L, Zhang S. Serum amyloid protein A in inflammatory bowel disease: from bench to bedside. Cell Death Discov 2023; 9:154. [PMID: 37164984 PMCID: PMC10172326 DOI: 10.1038/s41420-023-01455-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 04/18/2023] [Accepted: 04/27/2023] [Indexed: 05/12/2023] Open
Abstract
Inflammatory bowel diseases (IBD) is featured by gastrointestinal inflammation and a disease course with alternating recurrence and remission. The global burden caused by IBD has significantly boosted in recent years, necessitating treatment optimization. Serum amyloid A (SAA) is a class of 104 amino acid conservative acute-phase proteins, which is essential in immune-mediated inflammatory processes, like IBD. The SAA monomeric structure is composed of four α-helical regions and a C-terminal amorphous tail. Its disordered structure enables multiple bindings to different ligands and permits multiple functions. It has been proven that SAA has dual roles in the inflammatory process. SAA stimulates the pro-inflammatory cytokine expression and promotes the pathogenic differentiation of TH17 cells. In addition, SAA can remove toxic lipids produced during inflammatory responses and membrane debris from dead cells, redirect HDL, and recycle cholesterol for tissue repair. In IBD, SAA acts on gut epithelium barriers, induces T-cell differentiation, and promotes phagocytosis of Gram-negative bacteria. Owing to the tight connection between SAA and IBD, several clinical studies have taken SAA for a biomarker for diagnosis, assessing disease activity, and predicting prognosis in IBD. Furthermore, 5-MER peptide, a drug specifically targeting SAA, has shown anti-inflammatory effects in some SAA-dependent animal models, providing novel insights into the therapeutic targets of IBD.
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Affiliation(s)
- Rirong Chen
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Qia Chen
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Jieqi Zheng
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Zhirong Zeng
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Minhu Chen
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Li Li
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
| | - Shenghong Zhang
- Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
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Benfrid S, Park K, Dellarole M, Voss JE, Tamietti C, Pehau‐Arnaudet G, Raynal B, Brûlé S, England P, Zhang X, Mikhailova A, Hasan M, Ungeheuer M, Petres S, Biering SB, Harris E, Sakuntabhai A, Buchy P, Duong V, Dussart P, Coulibaly F, Bontems F, Rey FA, Flamand M. Dengue virus NS1 protein conveys pro-inflammatory signals by docking onto high-density lipoproteins. EMBO Rep 2022; 23:e53600. [PMID: 35607830 PMCID: PMC10549233 DOI: 10.15252/embr.202153600] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 04/24/2022] [Accepted: 04/27/2022] [Indexed: 10/05/2023] Open
Abstract
The dengue virus nonstructural protein 1 (NS1) is a secreted virulence factor that modulates complement, activates immune cells and alters endothelial barriers. The molecular basis of these events remains incompletely understood. Here we describe a functional high affinity complex formed between NS1 and human high-density lipoproteins (HDL). Collapse of the soluble NS1 hexamer upon binding to the lipoprotein particle leads to the anchoring of amphipathic NS1 dimeric subunits into the HDL outer layer. The stable complex can be visualized by electron microscopy as a spherical HDL with rod-shaped NS1 dimers protruding from the surface. We further show that the assembly of NS1-HDL complexes triggers the production of pro-inflammatory cytokines in human primary macrophages while NS1 or HDL alone do not. Finally, we detect NS1 in complex with HDL and low-density lipoprotein (LDL) particles in the plasma of hospitalized dengue patients and observe NS1-apolipoprotein E-positive complexes accumulating overtime. The functional reprogramming of endogenous lipoprotein particles by NS1 as a means to exacerbate systemic inflammation during viral infection provides a new paradigm in dengue pathogenesis.
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Affiliation(s)
- Souheyla Benfrid
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
- Université Paris Descartes SorbonneParis CitéFrance
- Present address:
Laboratoire de Santé AnimaleANSES, INRA, ENVA, UMR 1161Université Paris‐EstMaisons‐AlfortFrance
| | - Kyu‐Ho Park
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
- Present address:
Applied Molecular VirologyInstitut Pasteur KoreaSeongnam‐siKorea
| | - Mariano Dellarole
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
- Present address:
Virus Biophysics LaboratoryBionanosciences Research Center (CIBION)National Scientific and Technical Research Council (CONICET)Ciudad Autónoma de Buenos AiresArgentina
| | - James E Voss
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
- Present address:
Department of Immunology and MicrobiologyThe Scripps Research InstituteLa JollaCAUSA
| | - Carole Tamietti
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
| | | | - Bertrand Raynal
- Molecular Biophysics FacilityCNRS UMR 3528Institut PasteurParisFrance
| | - Sébastien Brûlé
- Molecular Biophysics FacilityCNRS UMR 3528Institut PasteurParisFrance
| | - Patrick England
- Molecular Biophysics FacilityCNRS UMR 3528Institut PasteurParisFrance
| | - Xiaokang Zhang
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
- Present address:
Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, CAS Key Laboratory of Brain Connectome and Manipulationthe Brain Cognition and Brain Disease Institute (BCBDI)Shenzhen Institutes of Advanced TechnologyChinese Academy of SciencesShenzhen‐Hong Kong Institute of Brain Science‐Shenzhen Fundamental Research InstitutionsShenzhenChina
| | - Anastassia Mikhailova
- HIV Inflammation et PersistanceInstitut PasteurParisFrance
- Present address:
Division of Molecular NeurobiologyDepartment of Medical Biochemistry and BiophysicsKarolinska InstituteStockholmSweden
| | - Milena Hasan
- Cytometry and Biomarkers Unit of Technology and ServiceCB UTechSParisFrance
| | | | - Stéphane Petres
- Production and Purification of Recombinant Proteins FacilityInstitut PasteurParisFrance
| | - Scott B Biering
- Division of Infectious Diseases and VaccinologySchool of Public HealthUniversity of CaliforniaBerkeleyCAUSA
| | - Eva Harris
- Division of Infectious Diseases and VaccinologySchool of Public HealthUniversity of CaliforniaBerkeleyCAUSA
| | | | - Philippe Buchy
- Virology UnitInstitut Pasteur du CambodgeInstitut Pasteur International NetworkPhnom PenhCambodia
- Present address:
GlaxoSmithKline Vaccines R&DSingaporeSingapore
| | - Veasna Duong
- Virology UnitInstitut Pasteur du CambodgeInstitut Pasteur International NetworkPhnom PenhCambodia
| | - Philippe Dussart
- Virology UnitInstitut Pasteur du CambodgeInstitut Pasteur International NetworkPhnom PenhCambodia
| | - Fasséli Coulibaly
- Department of Biochemistry and Molecular BiologyMonash UniversityClaytonVic.Australia
| | - François Bontems
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
- Département de Biologie et Chimie StructuralesInstitut de Chimie des Substances Naturelles, CNRS UPR2301Gif‐sur‐YvetteFrance
| | - Félix A Rey
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
| | - Marie Flamand
- Unité de Virologie StructuraleInstitut Pasteur and CNRS UMR3569ParisFrance
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4
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Human Serum Amyloid a Impaired Structural Stability of High-Density Lipoproteins (HDL) and Apolipoprotein (Apo) A-I and Exacerbated Glycation Susceptibility of ApoA-I and HDL. Molecules 2022; 27:molecules27134255. [PMID: 35807498 PMCID: PMC9268363 DOI: 10.3390/molecules27134255] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/24/2022] [Accepted: 06/30/2022] [Indexed: 02/04/2023] Open
Abstract
Human serum amyloid A (SAA) is an exchangeable apolipoprotein (apo) in high-density lipoprotein (HDL) that influences HDL quality and functionality, particularly in the acute phase of inflammation. On the other hand, the structural and functional correlations of HDL containing SAA and apoA-I have not been reported. The current study was designed to compare the change in HDL quality with increasing SAA content in the lipid-free and lipid-bound states in reconstituted HDL (rHDL). The expressed recombinant human SAA1 (13 kDa) was purified to at least 98% and characterized in the lipid-free and lipid-bound states with apoA-I. The dimyristoyl phosphatidylcholine (DMPC) binding ability of apoA-I was impaired severely by the addition of SAA, while SAA alone could not bind with DMPC. The recombinant human SAA1 was incorporated into the rHDL (molar ratio 95:5:1, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC): cholesterol: apoA-I) with various apoA-I:SAA molar ratios from 1:0 to 1:0.5, 1:1 and 1:2. With increasing SAA1 content, the rHDL particle size was reduced from 98 Å to 93 Å, and the α-helicity of apoA-I:SAA was decreased from 73% to 40% for (1:0) and (1:2), respectively. The wavelength maximum fluorescence (WMF) of tryptophan in rHDL was red-shifted from 339 nm to 345 nm for (1:0) and (1:2) of apoA-I:SAA, respectively, indicating that the addition of SAA to rHDL destabilized the secondary structure of apoA-I. Upon denaturation by urea treatment from 0 M to 8 M, SAA showed only a 3 nm red-shift in WMF, while apoA-I showed a 16 nm red-shift in WMF, indicating that SAA is resistant to denaturation and apoA-I had higher conformational flexibility than SAA. The glycation reaction of apoA-I in the presence of fructose was accelerated up to 1.8-fold by adding SAA in a dose-dependent manner than that of apoA-I alone. In conclusion, the incorporation of SAA in rHDL impaired the structural stability of apoA-I and exacerbated glycation of HDL and apoA-I.
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Lewkowicz E, Gursky O. Dynamic protein structures in normal function and pathologic misfolding in systemic amyloidosis. Biophys Chem 2022; 280:106699. [PMID: 34773861 PMCID: PMC9416430 DOI: 10.1016/j.bpc.2021.106699] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 10/08/2021] [Accepted: 10/08/2021] [Indexed: 02/08/2023]
Abstract
Dynamic and disordered regions in native proteins are often critical for their function, particularly in ligand binding and signaling. In certain proteins, however, such regions can contribute to misfolding and pathologic deposition as amyloid fibrils in vivo. For example, dynamic and disordered regions can promote amyloid formation by destabilizing the native structure, by directly triggering the aggregation, by promoting protein condensation, or by acting as sites of early proteolytic cleavage that favor a release of aggregation-prone fragments or facilitate fibril maturation. At the same time, enhanced dynamics in the native protein state accelerates proteolytic degradation that counteracts amyloid accumulation in vivo. Therefore, the functional need for dynamic protein regions must be balanced against their inherently labile nature. How exactly this balance is achieved and how is it shifted upon amyloidogenic mutations or post-translational modifications? To illustrate possible scenarios, here we review the beneficial and pathologic roles of dynamic and disordered regions in the native states of three families of human plasma proteins that form amyloid precursors in systemic amyloidoses: immunoglobulin light chain, apolipoproteins, and serum amyloid A. Analysis of structure, stability and local dynamics of these diverse proteins and their amyloidogenic variants exemplifies how disordered/dynamic regions can provide a functional advantage as well as an Achilles heel in pathologic amyloid formation.
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Zheng JJ, Agus JK, Hong BV, Tang X, Rhodes CH, Houts HE, Zhu C, Kang JW, Wong M, Xie Y, Lebrilla CB, Mallick E, Witwer KW, Zivkovic AM. Isolation of HDL by sequential flotation ultracentrifugation followed by size exclusion chromatography reveals size-based enrichment of HDL-associated proteins. Sci Rep 2021; 11:16086. [PMID: 34373542 PMCID: PMC8352908 DOI: 10.1038/s41598-021-95451-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 07/23/2021] [Indexed: 01/02/2023] Open
Abstract
High-density lipoprotein (HDL) particles have multiple beneficial and cardioprotective roles, yet our understanding of their full structural and functional repertoire is limited due to challenges in separating HDL particles from contaminating plasma proteins and other lipid-carrying particles that overlap HDL in size and/or density. Here we describe a method for isolating HDL particles using a combination of sequential flotation density ultracentrifugation and fast protein liquid chromatography with a size exclusion column. Purity was visualized by polyacrylamide gel electrophoresis and verified by proteomics, while size and structural integrity were confirmed by transmission electron microscopy. This HDL isolation method can be used to isolate a high yield of purified HDL from a low starting plasma volume for functional analyses. This method also enables investigators to select their specific HDL fraction of interest: from the least inclusive but highest purity HDL fraction eluting in the middle of the HDL peak, to pooling all of the fractions to capture the breadth of HDL particles in the original plasma sample. We show that certain proteins such as lecithin cholesterol acyltransferase (LCAT), phospholipid transfer protein (PLTP), and clusterin (CLUS) are enriched in large HDL particles whereas proteins such as alpha-2HS-glycoprotein (A2HSG), alpha-1 antitrypsin (A1AT), and vitamin D binding protein (VDBP) are enriched or found exclusively in small HDL particles.
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Affiliation(s)
| | - Joanne K Agus
- Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Brian V Hong
- Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Xinyu Tang
- Department of Nutrition, University of California, Davis, Davis, CA, USA
| | | | - Hannah E Houts
- Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Chenghao Zhu
- Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Jea Woo Kang
- Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Maurice Wong
- Department of Chemistry, University of California, Davis, Davis, CA, USA
| | - Yixuan Xie
- Department of Chemistry, University of California, Davis, Davis, CA, USA
| | - Carlito B Lebrilla
- Department of Chemistry, University of California, Davis, Davis, CA, USA
| | - Emily Mallick
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Kenneth W Witwer
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Angela M Zivkovic
- Department of Nutrition, University of California, Davis, Davis, CA, USA.
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Trp Fluorescence Redshift during HDL Apolipoprotein Denaturation Is Increased in Patients with Coronary Syndrome in Acute Phase: A New Assay to Evaluate HDL Stability. Int J Mol Sci 2021; 22:ijms22157819. [PMID: 34360583 PMCID: PMC8345965 DOI: 10.3390/ijms22157819] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/14/2021] [Accepted: 07/20/2021] [Indexed: 12/30/2022] Open
Abstract
High-density lipoproteins' (HDL) stability is a determinant of their residence times in plasma and consequently an important parameter that influences the beneficial properties of these lipoproteins. Since there are no accessible procedures for this purpose, here, we describe the methodological conditions to assess the stability of the HDL based on the redshift of the fluorescence spectrum of tryptophans contained in the structure of HDL-apolipoproteins during incubation with urea 8M. Along the HDL denaturation kinetics, the main variations of fluorescence were observed at the wavelengths of 330, 344, and 365 nm at room temperature. Therefore, HDL denaturation was estimated using the tryptophan (Trp)-ratio of fluorescence intensity (rfi) at such wavelengths. By setting 100% of the measurable denaturation at 26 h, HDL reached 50% after 8 h of incubation with urea. Then, for further analyses we determined the percentage of HDL denaturation at 8 h as an estimation of the stability of these lipoproteins. To explore the potential usefulness of this test, we analyzed the stability of HDL isolated from the plasma of 24 patients diagnosed with acute coronary syndrome (ACS). These HDL presented significantly higher percentages of denaturation (64.9% (58.7-78.4)) than HDLs of healthy individuals (23.3% (20.3-27.0)). These results indicate that HDL in ACS are less stable than in control subjects. Moreover, the percentage of denaturation of HDL correlated with body mass index and aspartate transaminase plasma activity. Furthermore, apo-I, HDL-cholesterol, HDL-triglycerides, and apo A-I-to-triglycerides ratio correlated with the percentage of HDL denaturation, suggesting that the lipoprotein composition is a main determinant of HDL stability. Finally, the percentage of HDL denaturation is the parameter that predicted the presence of ACS as determined by a machine learning procedure and logistic regression analysis. In conclusion, we established the methodological conditions to assess the stability of HDL by a fluorescence-based method that merits exploration in prospective studies for evaluating the coronary artery disease risk.
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8
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Methods to study the structure of misfolded protein states in systemic amyloidosis. Biochem Soc Trans 2021; 49:977-985. [PMID: 33929491 DOI: 10.1042/bst20201022] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 04/08/2021] [Accepted: 04/12/2021] [Indexed: 12/19/2022]
Abstract
Systemic amyloidosis is defined as a protein misfolding disease in which the amyloid is not necessarily deposited within the same organ that produces the fibril precursor protein. There are different types of systemic amyloidosis, depending on the protein constructing the fibrils. This review will focus on recent advances made in the understanding of the structural basis of three major forms of systemic amyloidosis: systemic AA, AL and ATTR amyloidosis. The three diseases arise from the misfolding of serum amyloid A protein, immunoglobulin light chains or transthyretin. The presented advances in understanding were enabled by recent progress in the methodology available to study amyloid structures and protein misfolding, in particular concerning cryo-electron microscopy (cryo-EM) and nuclear magnetic resonance (NMR) spectroscopy. An important observation made with these techniques is that the structures of previously described in vitro formed amyloid fibrils did not correlate with the structures of amyloid fibrils extracted from diseased tissue, and that in vitro fibrils were typically more protease sensitive. It is thus possible that ex vivo fibrils were selected in vivo by their proteolytic stability.
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9
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Tárraga WA, Falomir-Lockhart LJ, Garda HA, González MC. Analysis of pyrene-labelled apolipoprotein A-I oligomerization in solution: Spectra deconvolution and changes in P-value and excimer formation. Arch Biochem Biophys 2021; 699:108748. [PMID: 33444627 DOI: 10.1016/j.abb.2020.108748] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 12/22/2020] [Accepted: 12/28/2020] [Indexed: 11/15/2022]
Abstract
ApoA-I is the main protein of HDL which has anti-atherogenic properties attributed to reverse cholesterol transport. It shares with other exchangeable apolipoproteins a high level of structural plasticity. In the lipid-free state, the apolipoprotein amphipathic α-helices interact intra- and inter-molecularly, providing structural stabilization by a complex self-association mechanism. In this study, we employed a multi-parametric fluorescent probe to study the self-association of apoA-I. We constructed six single cysteine mutants spanning positions along three helices: F104C, K107C (H4), K133C, L137C (H5), F225C and K226C (H10); and labelled them with N-Maleimide Pyrene. Taking advantage of its spectral properties, namely formation of an excited dimer (excimer) and polarity-dependent changes in its fluorescence fine structure (P-value), we monitored the apoA-I self-association in its lipid-free form as a function of its concentration. Interactions in helices H5 (K133C) and H10 (F225C and K226C) were highlighted by excimer emission; while polarity changes were reported in helix H4 (K107C), as well as in helices H5 and H10. Mathematical models were developed to enrich data analysis and estimate association constants (KA) and oligomeric species distribution. Furthermore, we briefly discuss the usefulness of the multi-parametric fluorescent probe to monitor different equilibria, even at a single labelling position. Results suggest that apoA-I self-association must be considered to fully understand its physiological roles. Particularly, some contacts that stabilize discoidal HDL particles seem to be already present in the lipid-free apoA-I oligomers.
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Affiliation(s)
- Wilson A Tárraga
- Instituto de Investigaciones Bioquímica de La Plata (INIBIOLP), Centro Científico Tecnológico-La Plata, Calle 60 y 120 s/n, 1900, La Plata, Argentina.
| | - Lisandro J Falomir-Lockhart
- Instituto de Investigaciones Bioquímica de La Plata (INIBIOLP), Centro Científico Tecnológico-La Plata, Calle 60 y 120 s/n, 1900, La Plata, Argentina; Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115 s/n, 1900, La Plata, Argentina.
| | - Horacio A Garda
- Instituto de Investigaciones Bioquímica de La Plata (INIBIOLP), Centro Científico Tecnológico-La Plata, Calle 60 y 120 s/n, 1900, La Plata, Argentina; Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120 s/n, 1900, La Plata, Argentina.
| | - Marina C González
- Instituto de Investigaciones Bioquímica de La Plata (INIBIOLP), Centro Científico Tecnológico-La Plata, Calle 60 y 120 s/n, 1900, La Plata, Argentina; Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120 s/n, 1900, La Plata, Argentina.
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10
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Structural Basis for Vital Function and Malfunction of Serum Amyloid A: an Acute-Phase Protein that Wears Hydrophobicity on Its Sleeve. Curr Atheroscler Rep 2020; 22:69. [PMID: 32968930 PMCID: PMC7511256 DOI: 10.1007/s11883-020-00888-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2020] [Indexed: 12/13/2022]
Abstract
PURPOSE OF REVIEW This review addresses normal and pathologic functions of serum amyloid A (SAA), an enigmatic biomarker of inflammation and protein precursor of AA amyloidosis, a life-threatening complication of chronic inflammation. SAA is a small, highly evolutionarily conserved acute-phase protein whose plasma levels increase up to one thousand-fold in inflammation, infection, or after trauma. The advantage of this dramatic but transient increase is unclear, and the complex role of SAA in immune response is intensely investigated. This review summarizes recent advances in our understanding of the structure-function relationship of this intrinsically disordered protein, outlines its newly emerging beneficial roles in lipid transport and inflammation control, and discusses factors that critically influence its misfolding in AA amyloidosis. RECENT FINDINGS High-resolution structures of lipid-free SAA in crystals and fibrils have been determined by x-ray crystallography and electron cryo-microscopy. Low-resolution structural studies of SAA-lipid complexes, together with biochemical, cell-based, animal model, genetic, and clinical studies, have provided surprising new insights into a wide range of SAA functions. An emerging vital role of SAA is lipid encapsulation to remove cell membrane debris from sites of injury. The structural basis for this role has been proposed. The lysosomal origin of AA amyloidosis has solidified, and its molecular and cellular mechanisms have emerged. Recent studies have revealed molecular underpinnings for understanding complex functions of this Cambrian protein in lipid transport, immune response, and amyloid formation. These findings help guide the search for much-needed targeted therapies to block the protein deposition in AA amyloidosis.
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11
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Frame NM, Kumanan M, Wales TE, Bandara A, Fändrich M, Straub JE, Engen JR, Gursky O. Structural Basis for Lipid Binding and Function by an Evolutionarily Conserved Protein, Serum Amyloid A. J Mol Biol 2020; 432:1978-1995. [PMID: 32035904 PMCID: PMC7225066 DOI: 10.1016/j.jmb.2020.01.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 01/21/2020] [Accepted: 01/21/2020] [Indexed: 01/28/2023]
Abstract
Serum amyloid A (SAA) is a plasma protein that transports lipids during inflammation. To explore SAA solution conformations and lipid-binding mechanism, we used hydrogen-deuterium exchange mass spectrometry, lipoprotein reconstitution, amino acid sequence analysis, and molecular dynamics simulations. Solution conformations of lipid-bound and lipid-free mSAA1 at pH~7.4 agreed in details with the crystal structures but also showed important differences. The results revealed that amphipathic α-helices h1 and h3 comprise a lipid-binding site that is partially pre-formed in solution, is stabilized upon binding lipids, and shows lipid-induced folding of h3. This site sequesters apolar ligands via a concave hydrophobic surface in SAA oligomers. The largely disordered/dynamic C-terminal region is conjectured to mediate the promiscuous binding of other ligands. The h1-h2 linker region is predicted to form an unexpected β-hairpin that may represent an early amyloidogenic intermediate. The results help establish structural underpinnings for understanding SAA interactions with its key functional ligands, its evolutional conservation, and its transition to amyloid.
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Affiliation(s)
- Nicholas M Frame
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA, 02118, United States
| | - Meera Kumanan
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215, United States
| | - Thomas E Wales
- Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, MA, 02115, United States
| | - Asanga Bandara
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215, United States
| | - Marcus Fändrich
- Institute of Protein Biochemistry, Ulm University, Ulm, 89081, Germany
| | - John E Straub
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215, United States.
| | - John R Engen
- Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, MA, 02115, United States.
| | - Olga Gursky
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA, 02118, United States; Amyloidosis Treatment and Research Center, Boston University School of Medicine, Boston, MA, 02118, United States.
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12
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Takase H, Tanaka M, Nakamura Y, Morita SY, Yamada T, Mukai T. Effects of lipid composition on the structural properties of human serum amyloid A in reconstituted high-density lipoprotein particles. Chem Phys Lipids 2019; 221:8-14. [DOI: 10.1016/j.chemphyslip.2019.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 02/27/2019] [Accepted: 03/01/2019] [Indexed: 12/13/2022]
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13
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Randeria SN, Thomson GJA, Nell TA, Roberts T, Pretorius E. Inflammatory cytokines in type 2 diabetes mellitus as facilitators of hypercoagulation and abnormal clot formation. Cardiovasc Diabetol 2019; 18:72. [PMID: 31164120 PMCID: PMC6549308 DOI: 10.1186/s12933-019-0870-9] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 05/16/2019] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The global burden of type 2 diabetes mellitus (T2DM), together with the presence of cardiovascular risk in this population, is reaching pandemic levels. A prominent feature of T2DM is chronic and systemic inflammation, with the accompanying presence of circulating and dysregulated inflammatory biomarkers; which in turn is associated with abnormal clot formation. METHODS Here, we investigate the correlation between abnormal blood clotting, using thromboelastography (TEG), clot ultrastructure using scanning electron microscopy (SEM) and the presence of a dysregulated inflammatory cytokine profile, by examining various circulating biomarkers. RESULTS Our results show that many biomarkers, across TEG, cytokine and lipid groups, were greatly dysregulated in the T2DM sample. Furthermore, our T2DM sample's coagulation profiles were significantly more hypercoagulable when compared to our heathy sample, and ultrastructural analysis confirmed a matted and denser clot structure in the T2DM sample. CONCLUSIONS We suggest that dysregulated circulating molecules may in part be responsible for a hypercoagulable state and vascular dysfunction in the T2DM sample. We propose further that a personalized approach could be of great value when planning treatment and tracking the patient health status after embarking on a treatment regimes, and that looking to novel inflammatory and vascular biomarkers might be crucial.
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Affiliation(s)
- Shehan N Randeria
- Department of Physiological Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Greig J A Thomson
- Department of Physiological Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Theo A Nell
- Department of Physiological Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Timothy Roberts
- Department of Physiological Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
- Department of Biochemistry, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool, L69 7ZB, UK.
| | - Etheresia Pretorius
- Department of Physiological Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
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14
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Jayaraman S, Fändrich M, Gursky O. Synergy between serum amyloid A and secretory phospholipase A 2. eLife 2019; 8:46630. [PMID: 31111824 PMCID: PMC6557629 DOI: 10.7554/elife.46630] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 05/14/2019] [Indexed: 12/30/2022] Open
Abstract
Serum amyloid A (SAA) is an evolutionally conserved enigmatic biomarker of inflammation. In acute inflammation, SAA plasma levels increase ~1,000 fold, suggesting that this protein family has a vital beneficial role. SAA increases simultaneously with secretory phospholipase A2 (sPLA2), compelling us to determine how SAA influences sPLA2 hydrolysis of lipoproteins. SAA solubilized phospholipid bilayers to form lipoproteins that provided substrates for sPLA2. Moreover, SAA sequestered free fatty acids and lysophospholipids to form stable proteolysis-resistant complexes. Unlike albumin, SAA effectively removed free fatty acids under acidic conditions, which characterize inflammation sites. Therefore, SAA solubilized lipid bilayers to generate substrates for sPLA2 and removed its bioactive products. Consequently, SAA and sPLA2 can act synergistically to remove cellular membrane debris from injured sites, which is a prerequisite for tissue healing. We postulate that the removal of lipids and their degradation products constitutes a vital primordial role of SAA in innate immunity; this role remains to be tested in vivo. Cell boundaries are made up of fatty substances known as lipids. When cells get severely damaged, their lipid membranes break apart. These broken fragments of membrane become highly toxic, and must be removed as soon as possible to allow the tissue to heal. A small protein called serum amyloid A, SAA for short, was recently proposed to play a pivotal role in this process. In humans, SAA levels in the blood rapidly spike to over a thousand times their normal level following inflammation, injury or infection. Combined with the fact SAA has been conserved for over 500 million years, this suggests that SAA must be important for survival. But, it is not entirely clear how this protein works. One clue for how SAA works is its relationship to another ancient protein called secretory phospholipase A2. This protein, also known as sPLA2, is part of a big family of enzymes that break down lipids in the cell membrane. Notably, sPLA2 levels rise at the same time and place as SAA during inflammation. This led Jayaraman et al. to ask whether SAA and sPLA2 might be working together to clean up the cell membrane debris. To find out, Jayaraman et al. mixed mouse SAA with vesicles of membrane lipids, and then added sPLA2. This revealed that SAA reshapes the lipid membrane into smaller ‘nanoparticles’ with tightly curved surfaces that are easier for sPLA2 to break down. As the sPLA2 breaks up these particles, SAA then gathers up and gets rid of the leftover toxic fragments. This suggests that SAA has two roles: helping sPLA2 break down the membrane, and removing any toxic debris. Clearing debris after injury is essential for proper healing. So, understanding how it works is crucial to find new ways to treat inflammation. Further work to understand SAA and sPLA2 could improve our understanding of how to treat acute and chronic inflammation and its life-threatening complications.
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Affiliation(s)
- Shobini Jayaraman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, United States
| | - Marcus Fändrich
- Institute of Protein Biochemistry, Ulm University, Ulm, Germany
| | - Olga Gursky
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, United States.,Amyloidosis Treatment and Research Center, Boston University School of Medicine, Boston, United States
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15
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Wilson PG, Thompson JC, Shridas P, McNamara PJ, de Beer MC, de Beer FC, Webb NR, Tannock LR. Serum Amyloid A Is an Exchangeable Apolipoprotein. Arterioscler Thromb Vasc Biol 2018; 38:1890-1900. [PMID: 29976766 PMCID: PMC6202200 DOI: 10.1161/atvbaha.118.310979] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Objective- SAA (serum amyloid A) is a family of acute-phase reactants that have proinflammatory and proatherogenic activities. SAA is more lipophilic than apoA-I (apolipoprotein A-I), and during an acute-phase response, <10% of plasma SAA is found lipid-free. In most reports, SAA is found exclusively associated with high-density lipoprotein; however, we and others have reported SAA on apoB (apolipoprotein B)-containing lipoproteins in both mice and humans. The goal of this study was to determine whether SAA is an exchangeable apolipoprotein. Approach and Results- Delipidated human SAA was incubated with SAA-free human lipoproteins; then, samples were reisolated by fast protein liquid chromatography, and SAA analyzed by ELISA and immunoblot. Both in vitro and in vivo, we show that SAA associates with any lipoprotein and does not remain in a lipid-free form. Although SAA is preferentially found on high-density lipoprotein, it can exchange between lipoproteins. In the presence of CETP (cholesterol ester transfer protein), there is greater exchange of SAA between lipoproteins. Subjects with diabetes mellitus, but not those with metabolic syndrome, showed altered SAA lipoprotein distribution postprandially. Proteoglycan-mediated lipoprotein retention is thought to be an underlying mechanism for atherosclerosis development. SAA has a proteoglycan-binding domain. Lipoproteins containing SAA had increased proteoglycan binding compared with SAA-free lipoproteins. Conclusions- Thus, SAA is an exchangeable apolipoprotein and increases apoB-containing lipoproteins' proteoglycan binding. We and others have previously reported the presence of SAA on low-density lipoprotein in individuals with obesity, diabetes mellitus, and metabolic syndrome. We propose that the presence of SAA on apoB-containing lipoproteins may contribute to cardiovascular disease development in these populations.
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Affiliation(s)
- Patricia G Wilson
- Department of Veterans Affairs, Lexington, KY
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Joel C Thompson
- Department of Veterans Affairs, Lexington, KY
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Preetha Shridas
- Department of Internal Medicine, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Patrick J McNamara
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky
| | - Maria C de Beer
- Department of Physiology, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Frederick C de Beer
- Department of Internal Medicine, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Nancy R Webb
- Department of Veterans Affairs, Lexington, KY
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Lisa R Tannock
- Department of Veterans Affairs, Lexington, KY
- Department of Internal Medicine, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
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16
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Shridas P, De Beer MC, Webb NR. High-density lipoprotein inhibits serum amyloid A-mediated reactive oxygen species generation and NLRP3 inflammasome activation. J Biol Chem 2018; 293:13257-13269. [PMID: 29976759 DOI: 10.1074/jbc.ra118.002428] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 06/18/2018] [Indexed: 12/11/2022] Open
Abstract
Serum amyloid A (SAA) is a high-density apolipoprotein whose plasma levels can increase more than 1000-fold during a severe acute-phase inflammatory response and are more modestly elevated in chronic inflammation. SAA is thought to play important roles in innate immunity, but its biological activities have not been completely delineated. We previously reported that SAA deficiency protects mice from developing abdominal aortic aneurysms (AAAs) induced by chronic angiotensin II (AngII) infusion. Here, we report that SAA is required for AngII-induced increases in interleukin-1β (IL-1β), a potent proinflammatory cytokine that is tightly controlled by the Nod-like receptor protein 3 (NLRP3) inflammasome and caspase-1 and has been implicated in both human and mouse AAAs. We determined that purified SAA stimulates IL-1β secretion in murine J774 and bone marrow-derived macrophages through a mechanism that depends on NLRP3 expression and caspase-1 activity, but is independent of P2X7 nucleotide receptor (P2X7R) activation. Inhibiting reactive oxygen species (ROS) by N-acetyl-l-cysteine or mito-TEMPO and inhibiting activation of cathepsin B by CA-074 blocked SAA-mediated inflammasome activation and IL-1β secretion. Moreover, inhibiting cellular potassium efflux with glyburide or increasing extracellular potassium also significantly reduced SAA-mediated IL-1β secretion. Of note, incorporating SAA into high-density lipoprotein (HDL) prior to its use in cell treatments completely abolished its ability to stimulate ROS generation and inflammasome activation. These results provide detailed insights into SAA-mediated IL-1β production and highlight HDL's role in regulating SAA's proinflammatory effects.
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Affiliation(s)
- Preetha Shridas
- From the Departments of Internal Medicine, .,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536
| | - Maria C De Beer
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536.,Physiology, and.,Pharmacology and Nutritional Sciences
| | - Nancy R Webb
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536.,Pharmacology and Nutritional Sciences.,Saha Cardiovascular Research Center, and
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17
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Jayaraman S, Gantz DL, Haupt C, Fändrich M, Gursky O. Serum amyloid A sequesters diverse phospholipids and their hydrolytic products, hampering fibril formation and proteolysis in a lipid-dependent manner. Chem Commun (Camb) 2018; 54:3532-3535. [PMID: 29565436 DOI: 10.1039/c8cc01424h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Serum amyloid A action in immune response and deposition in inflammation-linked amyloidosis involve SAA-lipid interactions. We show that SAA sequesters neutral and anionic phospholipids and their hydrolytic products to form nanoparticles, suggesting a synergy with phospholipase A2. The lipid charge and shape affect SAA protection from proteolysis, aggregation and fibrillogenesis.
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Affiliation(s)
- Shobini Jayaraman
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., W302, Boston, MA 02118, USA.
| | - Donald L Gantz
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., W302, Boston, MA 02118, USA.
| | - Christian Haupt
- Institute of Protein Biochemistry, Ulm University, Helmholtzstraße 8/1, 89081, Ulm, Germany
| | - Marcus Fändrich
- Institute of Protein Biochemistry, Ulm University, Helmholtzstraße 8/1, 89081, Ulm, Germany
| | - Olga Gursky
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., W302, Boston, MA 02118, USA.
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18
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Serum amyloid A forms stable oligomers that disrupt vesicles at lysosomal pH and contribute to the pathogenesis of reactive amyloidosis. Proc Natl Acad Sci U S A 2017; 114:E6507-E6515. [PMID: 28743750 DOI: 10.1073/pnas.1707120114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Serum amyloid A (SAA) is an acute-phase plasma protein that functions in innate immunity and lipid homeostasis. SAA is a protein precursor of reactive AA amyloidosis, the major complication of chronic inflammation and one of the most common human systemic amyloid diseases worldwide. Most circulating SAA is protected from proteolysis and misfolding by binding to plasma high-density lipoproteins. However, unbound soluble SAA is intrinsically disordered and is either rapidly degraded or forms amyloid in a lysosome-initiated process. Although acidic pH promotes amyloid fibril formation by this and many other proteins, the molecular underpinnings are unclear. We used an array of spectroscopic, biochemical, and structural methods to uncover that at pH 3.5-4.5, murine SAA1 forms stable soluble oligomers that are maximally folded at pH 4.3 with ∼35% α-helix and are unusually resistant to proteolysis. In solution, these oligomers neither readily convert into mature fibrils nor bind lipid surfaces via their amphipathic α-helices in a manner typical of apolipoproteins. Rather, these oligomers undergo an α-helix to β-sheet conversion catalyzed by lipid vesicles and disrupt these vesicles, suggesting a membranolytic potential. Our results provide an explanation for the lysosomal origin of AA amyloidosis. They suggest that high structural stability and resistance to proteolysis of SAA oligomers at pH 3.5-4.5 help them escape lysosomal degradation, promote SAA accumulation in lysosomes, and ultimately damage cellular membranes and liberate intracellular amyloid. We posit that these soluble prefibrillar oligomers provide a missing link in our understanding of the development of AA amyloidosis.
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19
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Rennegarbe M, Lenter I, Schierhorn A, Sawilla R, Haupt C. Influence of C-terminal truncation of murine Serum amyloid A on fibril structure. Sci Rep 2017; 7:6170. [PMID: 28733641 PMCID: PMC5522423 DOI: 10.1038/s41598-017-06419-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 06/13/2017] [Indexed: 12/18/2022] Open
Abstract
Amyloid A (AA) amyloidosis is a systemic protein misfolding disease affecting humans and other vertebrates. While the protein precursor in humans and mice is the acute-phase reactant serum amyloid A (SAA) 1.1, the deposited fibrils consist mainly of C-terminally truncated SAA fragments, termed AA proteins. For yet unknown reasons, phenotypic variations in the AA amyloid distribution pattern are clearly associated with specific AA proteins. Here we describe a bacterial expression system and chromatographic strategies to obtain significant amounts of C-terminally truncated fragments of murine SAA1.1 that correspond in truncation position to relevant pathological AA proteins found in humans. This enables us to investigate systematically structural features of derived fibrils. All fragments form fibrils under nearly physiological conditions that show similar morphological appearance and amyloid-like properties as evident from amyloid-specific dye binding, transmission electron microscopy and infrared spectroscopy. However, infrared spectroscopy suggests variations in the structural organization of the amyloid fibrils that might be derived from a modulating role of the C-terminus for the fibril structure. These results provide insights, which can help to get a better understanding of the molecular mechanisms underlying the different clinical phenotypes of AA amyloidosis.
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Affiliation(s)
- Matthies Rennegarbe
- Institute of Protein Biochemistry, Ulm University, Helmholtzstraße 8/1, 89081, Ulm, Germany
| | - Inga Lenter
- Max Planck Research Unit for Enzymology of Protein Folding, Weinbergweg 22, 06120, Halle (Saale), Germany
| | - Angelika Schierhorn
- Institute of Biochemistry and Biotechnology, Martin-Luther-University, Kurt-Mothes-Straße 3, 06120, Halle (Saale), Germany
| | - Romy Sawilla
- Institute of Protein Biochemistry, Ulm University, Helmholtzstraße 8/1, 89081, Ulm, Germany
| | - Christian Haupt
- Institute of Protein Biochemistry, Ulm University, Helmholtzstraße 8/1, 89081, Ulm, Germany.
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20
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Claus S, Meinhardt K, Aumüller T, Puscalau-Girtu I, Linder J, Haupt C, Walther P, Syrovets T, Simmet T, Fändrich M. Cellular mechanism of fibril formation from serum amyloid A1 protein. EMBO Rep 2017. [PMID: 28637682 DOI: 10.15252/embr.201643411] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Serum amyloid A1 (SAA1) is an apolipoprotein that binds to the high-density lipoprotein (HDL) fraction of the serum and constitutes the fibril precursor protein in systemic AA amyloidosis. We here show that HDL binding blocks fibril formation from soluble SAA1 protein, whereas internalization into mononuclear phagocytes leads to the formation of amyloid. SAA1 aggregation in the cell model disturbs the integrity of vesicular membranes and leads to lysosomal leakage and apoptotic death. The formed amyloid becomes deposited outside the cell where it can seed the fibrillation of extracellular SAA1. Our data imply that cells are transiently required in the amyloidogenic cascade and promote the initial nucleation of the deposits. This mechanism reconciles previous evidence for the extracellular location of deposits and amyloid precursor protein with observations the cells are crucial for the formation of amyloid.
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Affiliation(s)
- Stephanie Claus
- Institute of Protein Biochemistry, Ulm University, Ulm, Germany
| | | | - Tobias Aumüller
- Institute of Protein Biochemistry, Ulm University, Ulm, Germany
| | | | - Julia Linder
- Institute of Protein Biochemistry, Ulm University, Ulm, Germany
| | - Christian Haupt
- Institute of Protein Biochemistry, Ulm University, Ulm, Germany
| | - Paul Walther
- Central Electron Microscopy Facility, Ulm University, Ulm, Germany
| | - Tatiana Syrovets
- Institute of Pharmacology of Natural Products & Clinical Pharmacology, Ulm University, Ulm, Germany
| | - Thomas Simmet
- Institute of Pharmacology of Natural Products & Clinical Pharmacology, Ulm University, Ulm, Germany
| | - Marcus Fändrich
- Institute of Protein Biochemistry, Ulm University, Ulm, Germany
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21
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Frame NM, Jayaraman S, Gantz DL, Gursky O. Serum amyloid A self-assembles with phospholipids to form stable protein-rich nanoparticles with a distinct structure: A hypothetical function of SAA as a "molecular mop" in immune response. J Struct Biol 2017. [PMID: 28645735 DOI: 10.1016/j.jsb.2017.06.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Serum amyloid A (SAA) is an acute-phase protein whose action in innate immunity and lipid homeostasis is unclear. Most circulating SAA binds plasma high-density lipoproteins (HDL) and reroutes lipid transport. In vivo SAA binds existing lipoproteins or generates them de novo upon lipid uptake from cells. We explored the products of SAA-lipid interactions and lipoprotein remodeling in vitro. SAA complexes with palmitoyl-oleoyl phosphocholine (POPC) were analyzed for structure and stability using circular dichroism and fluorescence spectroscopy, electron microscopy, gel electrophoresis and gel filtration. The results revealed the formation of 8-11nm lipoproteins that were∼50% α-helical and stable at near-physiological conditions but were irreversibly remodeled at Tm∼52°C. Similar HDL-size nanoparticles formed spontaneously at ambient conditions or upon thermal remodeling of parent lipoproteins containing various amounts of proteins and lipids, including POPC and cholesterol. Therefore, such HDL-size particles formed stable kinetically accessible structures in a wide range of conditions. Based on their size and stoichiometry, each particle contained about 12 SAA and 72 POPC molecules, with a protein:lipid weight ratio circa 2.5:1, suggesting a structure distinct from HDL. High stability of these nanoparticles and their HDL-like size suggest that similar lipoproteins may form in vivo during inflammation or injury when SAA concentration is high and membranes from dead cells require rapid removal. We speculate that solubilization of membranes by SAA to generate lipoproteins in a spontaneous energy-independent process constitutes the primordial function of this ancient protein, providing the first line of defense in clearing cell debris from the injured sites.
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Affiliation(s)
- Nicholas M Frame
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., Boston, MA 02118, USA.
| | - Shobini Jayaraman
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., Boston, MA 02118, USA.
| | - Donald L Gantz
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., Boston, MA 02118, USA.
| | - Olga Gursky
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany St., Boston, MA 02118, USA.
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22
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Jayaraman S, Haupt C, Gursky O. Paradoxical effects of SAA on lipoprotein oxidation suggest a new antioxidant function for SAA. J Lipid Res 2016; 57:2138-2149. [PMID: 27744369 DOI: 10.1194/jlr.m071191] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 10/12/2016] [Indexed: 01/01/2023] Open
Abstract
Oxidative stress and inflammation, which involve a dramatic increase in serum amyloid A (SAA) levels, are critical in the development of atherosclerosis. Most SAA circulates on plasma HDL particles, altering their cardioprotective properties. SAA-enriched HDL has diminished anti-oxidant effects on LDL, which may contribute to atherogenesis. We determined combined effects of SAA enrichment and oxidation on biochemical changes in HDL. Normal human HDLs were incubated with SAA, oxidized by various factors (Cu2+, myeloperoxidase, H2O2, OCl-), and analyzed for lipid and protein modifications and biophysical remodeling. Three novel findings are reported: addition of SAA reduces oxidation of HDL and LDL lipids; oxidation of SAA-containing HDL in the presence of OCl- generates a covalent heterodimer of SAA and apoA-I that resists the release from HDL; and mild oxidation promotes spontaneous release of proteins (SAA and apoA-I) from SAA-enriched HDL. We show that the anti-oxidant effects of SAA extend to various oxidants and are mediated mainly by the unbound protein. We propose that free SAA sequesters lipid hydroperoxides and delays lipoprotein oxidation, though much less efficiently than other anti-oxidant proteins, such as apoA-I, that SAA displaces from HDL. These findings prompt us to reconsider the role of SAA in lipid oxidation in vivo.
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Affiliation(s)
- Shobini Jayaraman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - Christian Haupt
- Institute of Protein Biochemistry, University of Ulm, 89081 Ulm, Germany
| | - Olga Gursky
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
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23
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Zhao D, Yang LY, Wang XH, Yuan SS, Yu CG, Wang ZW, Lang JN, Feng YM. Different relationship between ANGPTL3 and HDL components in female non-diabetic subjects and type-2 diabetic patients. Cardiovasc Diabetol 2016; 15:132. [PMID: 27620179 PMCID: PMC5020513 DOI: 10.1186/s12933-016-0450-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 09/03/2016] [Indexed: 01/03/2023] Open
Abstract
Background Angiopoietin-like protein 3 (ANGPTL3) is a major lipoprotein regulator and shows positive correlation with high-density lipoprotein-cholesterol (HDL-c) in population studies and ANGPTL3 mutated subjects. However, no study has looked its correlation with HDL components nor with HDL function in patients with type 2 diabetes mellitus (T2DM). Methods We studied 298 non-diabetic subjects and 300 T2DM patients who were randomly recruited in the tertiary referral centre. Plasma levels of ANGPTL3 were quantified by ELISA. Plasma samples were fractionated to obtain HDLs. HDL components including apolipoprotein A-I (apoA-I), triglyceride, serum amyloid A (SAA), phospholipid and Sphingosine-1-phosphate were measured. HDLs were isolated from female controls and T2DM patients by ultracentrifugation to assess cholesterol efflux against HDLs. A Pearson unadjusted correlation analysis and a linear regression analysis adjusting for age, body mass index and lipid lowering drugs were performed in male or female non-diabetic participants or diabetic patients, respectively. Results We demonstrated that plasma level of ANGPTL3 was lower in female T2DM patients than female controls although no difference of ANGPTL3 levels was detected between male controls and T2DM patients. After adjusting for confounding factors, one SD increase of ANGPTL3 (164.6 ng/ml) associated with increase of 2.57 mg/dL cholesterol and 1.14 μg/mL apoA-I but decrease of 47.07 μg/L of SAA in HDL particles of non-diabetic females (p < 0.05 for cholesterol and SAA; p < 0.0001 for apoA-I). By contrast, 1-SD increase of ANGPTL3 (159.9 ng/ml) associated with increase of 1.69 mg/dl cholesterol and 1.25 μg/mL apoA-I but decrease of 11.70 μg/L of SAA in HDL particles of female diabetic patients (p < 0.05 for cholesterol; p < 0.0001 for apoA-I; p = 0.676 for SAA). Moreover, one SD increase of ANGPTL3 associated with increase of 2.11 % cholesterol efflux against HDLs in non-diabetic females (p = 0.071) but decrease of 1.46 % in female T2DM patients (p = 0.13) after adjusting for confounding factors. Conclusions ANGPTL3 is specifically correlated with HDL-c, apoA-I, SAA and HDL function in female non-diabetic participants. The decrease of ANGPTL3 level in female T2DM patients might contribute to its weak association to HDL components and function. ANGPTL3 could be considered as a novel therapeutic target for HDL metabolism for treating diabetes. Electronic supplementary material The online version of this article (doi:10.1186/s12933-016-0450-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dong Zhao
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Long-Yan Yang
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Xu-Hong Wang
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Sha-Sha Yuan
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Cai-Guo Yu
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Zong-Wei Wang
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Jia-Nan Lang
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China
| | - Ying-Mei Feng
- Beijing Key Laboratory of Diabetes Prevention and Research, Department of Endocrinology, Lu He Hospital, Capital Medical University, Beijing, 101149, China. .,Stem Cell Institute, University of Leuven, 3000, Louvain, Belgium.
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24
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Digre A, Nan J, Frank M, Li JP. Heparin interactions with apoA1 and SAA in inflammation-associated HDL. Biochem Biophys Res Commun 2016; 474:309-314. [PMID: 27105909 DOI: 10.1016/j.bbrc.2016.04.092] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 04/18/2016] [Indexed: 12/23/2022]
Abstract
Apolipoprotein A1 (apoA1) is the main protein component responsible for transportation of cholesterol on high-density lipoprotein (HDL). Serum amyloid A (SAA) is an acute phase protein associated with HDL. Apart from their physiological functions, both apoA1 and SAA have been identified as 'amyloidogenic peptides'. We report herein that the polysaccharide heparin interacts with both apoA1 and SAA in HDL isolated from plasma of inflamed mice. The reaction is rapid, forming complex aggregates composed of heparin, apoA1 and SAA as revealed by gel electrophoresis. This interaction is dependent on the size and concentration of added heparin. Mass spectrometry analysis of peptides derived from chemically crosslinked HDL-SAA particles detected multiple crosslinks between apoA1 and SAA, indicating close proximity (within 25 Å) of these two proteins on the HDL surface, providing a molecular and structural mechanism for the simultaneous binding of heparin to apoA1 and SAA.
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Affiliation(s)
- Andreas Digre
- Department of Medical Biochemistry and Microbiology/SciLifeLab, University of Uppsala, The Biomedical Center, Box 582, SE-751 23 Uppsala, Sweden
| | - Jie Nan
- MAX IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden
| | | | - Jin-Ping Li
- Department of Medical Biochemistry and Microbiology/SciLifeLab, University of Uppsala, The Biomedical Center, Box 582, SE-751 23 Uppsala, Sweden.
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25
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Kim MH, de Beer MC, Wroblewski JM, Charnigo RJ, Ji A, Webb NR, de Beer FC, van der Westhuyzen DR. Impact of individual acute phase serum amyloid A isoforms on HDL metabolism in mice. J Lipid Res 2016; 57:969-79. [PMID: 27018443 DOI: 10.1194/jlr.m062174] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Indexed: 01/12/2023] Open
Abstract
The acute phase (AP) reactant serum amyloid A (SAA), an HDL apolipoprotein, exhibits pro-inflammatory activities, but its physiological function(s) are poorly understood. Functional differences between SAA1.1 and SAA2.1, the two major SAA isoforms, are unclear. Mice deficient in either isoform were used to investigate plasma isoform effects on HDL structure, composition, and apolipoprotein catabolism. Lack of either isoform did not affect the size of HDL, normally enlarged in the AP, and did not significantly change HDL composition. Plasma clearance rates of HDL apolipoproteins were determined using native HDL particles. The fractional clearance rates (FCRs) of apoA-I, apoA-II, and SAA were distinct, indicating that HDL is not cleared as intact particles. The FCRs of SAA1.1 and SAA2.1 in AP mice were similar, suggesting that the selective deposition of SAA1.1 in amyloid plaques is not associated with a difference in the rates of plasma clearance of the isoforms. Although the clearance rate of SAA was reduced in the absence of the HDL receptor, scavenger receptor class B type I (SR-BI), it remained significantly faster compared with that of apoA-I and apoA-II, indicating a relatively minor role of SR-BI in SAA's rapid clearance. These studies enhance our understanding of SAA metabolism and SAA's effects on AP-HDL composition and catabolism.
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Affiliation(s)
- Myung-Hee Kim
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY 40536
| | - Maria C de Beer
- Physiology, University of Kentucky Medical Center, Lexington, KY 40536 Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY 40536
| | - Joanne M Wroblewski
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY 40536 Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY 40536
| | - Richard J Charnigo
- Departments of Statistics and Biostatistics, University of Kentucky, Lexington, KY 40506
| | - Ailing Ji
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY 40536 Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY 40536
| | - Nancy R Webb
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY 40536 Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY 40536
| | - Frederick C de Beer
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY 40536 Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY 40536
| | - Deneys R van der Westhuyzen
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY 40536 Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY 40536 Molecular and Cellular Biochemistry, University of Kentucky Medical Center, Lexington, KY 40536
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26
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Frame NM, Gursky O. Structure of serum amyloid A suggests a mechanism for selective lipoprotein binding and functions: SAA as a hub in macromolecular interaction networks. FEBS Lett 2016; 590:866-79. [PMID: 26918388 DOI: 10.1002/1873-3468.12116] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 02/19/2016] [Accepted: 02/19/2016] [Indexed: 01/19/2023]
Abstract
Serum amyloid A is a major acute-phase plasma protein that modulates innate immunity and cholesterol homeostasis. We combine sequence analysis with x-ray crystal structures to postulate that SAA acts as an intrinsically disordered hub mediating interactions among proteins, lipids and proteoglycans. A structural model of lipoprotein-bound SAA monomer is proposed wherein two α-helices from the N-domain form a concave hydrophobic surface that binds lipoproteins. A C-domain, connected to the N-domain via a flexible linker, binds polar/charged ligands including cell receptors, bridging them with lipoproteins and rerouting cholesterol transport. Our model is supported by the SAA cleavage in the interdomain linker to generate the 1-76 fragment deposited in reactive amyloidosis. This model sheds new light on functions of this enigmatic protein.
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Affiliation(s)
- Nicholas M Frame
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - Olga Gursky
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA, USA
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