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Lund J, Lähteenmäki E, Eklund T, Bakke HG, Thoresen GH, Pirinen E, Jauhiainen M, Rustan AC, Lehti M. Human HDL subclasses modulate energy metabolism in skeletal muscle cells. J Lipid Res 2024; 65:100481. [PMID: 38008260 PMCID: PMC10770614 DOI: 10.1016/j.jlr.2023.100481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 11/20/2023] [Accepted: 11/22/2023] [Indexed: 11/28/2023] Open
Abstract
In addition to its antiatherogenic role, HDL reportedly modulates energy metabolism at the whole-body level. HDL functionality is associated with its structure and composition, and functional activities can differ between HDL subclasses. Therefore, we studied if HDL2 and HDL3, the two major HDL subclasses, are able to modulate energy metabolism of skeletal muscle cells. Differentiated mouse and primary human skeletal muscle myotubes were used to investigate the influences of human HDL2 and HDL3 on glucose and fatty uptake and oxidation. HDL-induced changes in lipid distribution and mRNA expression of genes related to energy substrate metabolism, mitochondrial function, and HDL receptors were studied with human myotubes. Additionally, we examined the effects of apoA-I and discoidal, reconstituted HDL particles on substrate metabolism. In mouse myotubes, HDL subclasses strongly enhanced glycolysis upon high and low glucose concentrations. HDL3 caused a minor increase in ATP-linked respiration upon glucose conditioning but HDL2 improved complex I-mediated mitochondrial respiration upon fatty acid treatment. In human myotubes, glucose metabolism was attenuated but fatty acid uptake and oxidation were markedly increased by both HDL subclasses, which also increased mRNA expression of genes related to fatty acid metabolism and HDL receptors. Finally, both HDL subclasses induced incorporation of oleic acid into different lipid classes. These results, demonstrating that HDL subclasses enhance fatty acid oxidation in human myotubes but improve anaerobic metabolism in mouse myotubes, support the role of HDL as a circulating modulator of energy metabolism. Exact mechanisms and components of HDL causing the change, require further investigation.
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Affiliation(s)
- Jenny Lund
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Oslo, Norway
| | - Emilia Lähteenmäki
- Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland.
| | - Tiia Eklund
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Hege G Bakke
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Oslo, Norway
| | - G Hege Thoresen
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Oslo, Norway; Department of Pharmacology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Eija Pirinen
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Research Unit for Biomedicine and Internal Medicine, Faculty of Medicine, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Matti Jauhiainen
- Department of Public Health and Welfare, Minerva Foundation Institute for Medical Research and Finnish Institute for Health and Welfare, Helsinki, Finland
| | - Arild C Rustan
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Oslo, Norway
| | - Maarit Lehti
- Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
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James JK, Norland K, Johar AS, Kullo IJ. Deep generative models of LDLR protein structure to predict variant pathogenicity. J Lipid Res 2023; 64:100455. [PMID: 37821076 PMCID: PMC10696256 DOI: 10.1016/j.jlr.2023.100455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 09/16/2023] [Accepted: 10/05/2023] [Indexed: 10/13/2023] Open
Abstract
The complex structure and function of low density lipoprotein receptor (LDLR) makes classification of protein-coding missense variants challenging. Deep generative models, including Evolutionary model of Variant Effect (EVE), Evolutionary Scale Modeling (ESM), and AlphaFold 2 (AF2), have enabled significant progress in the prediction of protein structure and function. ESM and EVE directly estimate the likelihood of a variant sequence but are purely data-driven and challenging to interpret. AF2 predicts LDLR structures, but variant effects are explicitly modeled by estimating changes in stability. We tested the effectiveness of these models for predicting variant pathogenicity compared to established methods. AF2 produced two distinct conformations based on a novel hinge mechanism. Within ESM's hidden space, benign and pathogenic variants had different distributions. In EVE, these distributions were similar. EVE and ESM were comparable to Polyphen-2, SIFT, REVEL, and Primate AI for predicting binary classifications in ClinVar. However, they were more strongly correlated with experimental measures of LDL uptake. AF2 poorly performed in these tasks. Using the UK Biobank to compare association with clinical phenotypes, ESM and EVE were more strongly associated with serum LDL-C than Polyphen-2. ESM was able to identify variants with more extreme LDL-C levels than EVE and had a significantly stronger association with atherosclerotic cardiovascular disease. In conclusion, AF2 predicted LDLR structures do not accurately model variant pathogenicity. ESM and EVE are competitive with prior scoring methods for prediction based on binary classifications in ClinVar but are superior based on correlations with experimental assays and clinical phenotypes.
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Affiliation(s)
- Jose K James
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Kristjan Norland
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Angad S Johar
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Iftikhar J Kullo
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA; Gonda Vascular Center, Mayo Clinic, Rochester, MN, USA.
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Mitok KA, Schueler KL, King SM, Orr J, Ryan KA, Keller MP, Krauss RM, Mitchell BD, Shuldiner AR, Attie AD. Missense variants in SORT1 are associated with LDL-C in an Amish population. J Lipid Res 2023; 64:100468. [PMID: 37913995 PMCID: PMC10711479 DOI: 10.1016/j.jlr.2023.100468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/23/2023] [Accepted: 10/26/2023] [Indexed: 11/03/2023] Open
Abstract
Common noncoding variants at the human 1p13.3 locus associated with SORT1 expression are among those most strongly associated with low-density lipoprotein cholesterol (LDL-C) in human genome-wide association studies. However, validation studies in mice and cell lines have produced variable results regarding the directionality of the effect of SORT1 on LDL-C. This, together with the fact that the 1p13.3 variants are associated with expression of several genes, has raised the question of whether SORT1 is the causal gene at this locus. Using whole exome sequencing in members of an Amish population, we identified coding variants in SORT1 that are associated with increased (rs141749679, K302E) and decreased (rs149456022, Q225H) LDL-C. Further, analysis of plasma lipoprotein particle subclasses by ion mobility in a subset of rs141749679 (K302E) carriers revealed higher levels of large LDL particles compared to noncarriers. In contrast to the effect of these variants in the Amish, the sortilin K302E mutation introduced into a C57BL/6J mouse via CRISPR/Cas9 resulted in decreased non-high-density lipoprotein cholesterol, and the sortilin Q225H mutation did not alter cholesterol levels in mice. This is indicative of different effects of these mutations on cholesterol metabolism in the two species. To our knowledge, this is the first evidence that naturally occurring coding variants in SORT1 are associated with LDL-C, thus supporting SORT1 as the gene responsible for the association of the 1p13.3 locus with LDL-C.
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Affiliation(s)
- Kelly A Mitok
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Kathryn L Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Sarah M King
- Department of Pediatrics, University of California-San Francisco, San Francisco, CA, USA
| | - Joseph Orr
- Department of Pediatrics, University of California-San Francisco, San Francisco, CA, USA
| | - Kathleen A Ryan
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Ronald M Krauss
- Department of Pediatrics, University of California-San Francisco, San Francisco, CA, USA
| | - Braxton D Mitchell
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Alan R Shuldiner
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA; Regeneron Genetics Center, Tarrytown, NY, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
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Jaeschke A, Haller A, Cash JG, Nam C, Igel E, Roebroek AJM, Hui DY. Mutation in the distal NPxY motif of LRP1 alleviates dietary cholesterol-induced dyslipidemia and tissue inflammation. J Lipid Res 2020; 62:100012. [PMID: 33500241 PMCID: PMC7859857 DOI: 10.1194/jlr.ra120001141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 12/01/2020] [Accepted: 12/09/2020] [Indexed: 12/23/2022] Open
Abstract
The impairment of LDL receptor-related protein-1 (LRP1) in numerous cell types is associated with obesity, diabetes, and fatty liver disease. Here, we compared the metabolic phenotype of C57BL/6J wild-type and LRP1 knock-in mice carrying an inactivating mutation in the distal NPxY motif after feeding a low-fat diet or high-fat (HF) diet with cholesterol supplementation (HFHC) or HF diet without cholesterol supplementation. In response to HF feeding, both groups developed hyperglycemia, hyperinsulinemia, hyperlipidemia, increased adiposity, and adipose tissue inflammation and liver steatosis. However, LRP1 NPxY mutation prevents HFHC diet-induced hypercholesterolemia, reduces adipose tissue and brain inflammation, and limits liver progression to steatohepatitis. Nevertheless, this mutation does not protect against HFHC diet-induced insulin resistance. The selective metabolic improvement observed in HFHC diet-fed LRP1 NPxY mutant mice is due to an apparent increase of hepatic LDL receptor levels, leading to an elevated rate of plasma lipoprotein clearance and lower hepatic cholesterol levels. The unique metabolic phenotypes displayed by LRP1 NPxY mutant mice indicate an LRP1-cholesterol axis in modulating tissue inflammation. The LRP1 NPxY mutant mouse phenotype differs from phenotypes observed in mice with tissue-specific LRP1 inactivation, thus highlighting the importance of an integrative approach to evaluate how global LRP1 dysfunction contributes to metabolic disease development.
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Affiliation(s)
- Anja Jaeschke
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - April Haller
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - James G Cash
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Christopher Nam
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Emily Igel
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Anton J M Roebroek
- Laboratory for Experimental Mouse Genetics, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | - David Y Hui
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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Dong H, Zhao Z, LeBrun DG, Michaely P. Identification of roles for H264, H306, H439, and H635 in acid-dependent lipoprotein release by the LDL receptor. J Lipid Res 2016; 58:364-374. [PMID: 27895090 DOI: 10.1194/jlr.m070938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 11/19/2016] [Indexed: 11/20/2022] Open
Abstract
Lipoproteins internalized by the LDL receptor (LDLR) are released from this receptor in endosomes through a process that involves acid-dependent conformational changes in the receptor ectodomain. How acidic pH promotes this release process is not well understood. Here, we assessed roles for six histidine residues for which either genetic or structural data suggested a possible role in the acid-responsiveness of the LDLR. Using assays that measured conformational change, acid-dependent lipoprotein release, LDLR recycling, and net lipoprotein uptake, we show that H635 plays important roles in acid-dependent conformational change and lipoprotein release, while H264, H306, and H439 play ancillary roles in the response of the LDLR to acidic pH.
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Affiliation(s)
- Hongyun Dong
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Zhenze Zhao
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Drake G LeBrun
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Peter Michaely
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
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Ruscica M, Ferri N, Macchi C, Meroni M, Lanti C, Ricci C, Maggioni M, Fracanzani AL, Badiali S, Fargion S, Magni P, Valenti L, Dongiovanni P. Liver fat accumulation is associated with circulating PCSK9. Ann Med 2016; 48:384-91. [PMID: 27222915 DOI: 10.1080/07853890.2016.1188328] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Nonalcoholic fatty liver disease (NAFLD) associates with cardiovascular disease independently of classic risk factors. Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) is secreted by hepatocytes and inhibits the uptake of low-density lipoproteins by targeting the receptor for degradation, and possibly lipogenesis. PCSK9 loss-of-function mutations and anti-PCKS9 drugs reduce LDL-cholesterol. AIM To evaluate whether hepatic fat content is associated with circulating PCSK9. MATERIALS AND METHODS In 201 consecutive patients biopsied for suspected nonalcoholic steatohepatitis, liver damage was quantified by NAFLD activity score, circulating PCSK9 by ELISA, and hepatic mRNA by qRT-PCR in a subset (n = 76). RESULTS Circulating PCSK9 was associated with steatosis grade (p = 0.0011), necroinflammation (p < 0.001), ballooning (p = 0.005), and fibrosis stage (p = 0.001). At multivariate analysis, PCSK9 was associated with steatosis grade (p = 0.012), older age and lower BMI, independently of sex, hyperglycemia, and fibrosis/inflammation. Circulating PCSK9 was associated with hepatic expression of SREBP-1c (p = 0.0002) and FAS (p = 0.03). PCSK9 mRNA levels were also correlated with steatosis severity (p = 0.04) and hepatic APOB (p < 0.001), SREBP-1c (p = 0.047) and FAS expression (p = 0.001). CONCLUSIONS Circulating PCSK9 increases with hepatic fat accumulation and correlates with the severity of steatosis, independently of metabolic confounders and liver damage. Modulation of PCSK9 synthesis and release might be involved in NAFLD pathogenesis. Key Messages Circulating PCSK9 levels increase with hepatic fat accumulation. Circulating PCSK9 levels are associated with increased de novo lipogenesis. Hepatic PCSK9 expression is associated with steatosis severity and activation of lipogenesis.
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Affiliation(s)
- Massimiliano Ruscica
- a Department of Pharmacological and Biomolecular Sciences , Università Degli Studi Di Milano , Milano , Italy
| | - Nicola Ferri
- b Department of Pharmaceutical and Pharmacological Sciences , Università di Padova , Padova , Italy
| | - Chiara Macchi
- a Department of Pharmacological and Biomolecular Sciences , Università Degli Studi Di Milano , Milano , Italy
| | - Marica Meroni
- c Department of Pathophysiology and Transplantation , Università Degli Studi Di Milano , Milano , Italy
| | - Claudia Lanti
- d Internal Medicine and Metabolic Diseases , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
| | - Chiara Ricci
- a Department of Pharmacological and Biomolecular Sciences , Università Degli Studi Di Milano , Milano , Italy
| | - Marco Maggioni
- e Department of Pathology , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
| | - Anna Ludovica Fracanzani
- c Department of Pathophysiology and Transplantation , Università Degli Studi Di Milano , Milano , Italy ;,d Internal Medicine and Metabolic Diseases , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
| | - Sara Badiali
- f Department of Surgery , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
| | - Silvia Fargion
- c Department of Pathophysiology and Transplantation , Università Degli Studi Di Milano , Milano , Italy ;,d Internal Medicine and Metabolic Diseases , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
| | - Paolo Magni
- a Department of Pharmacological and Biomolecular Sciences , Università Degli Studi Di Milano , Milano , Italy
| | - Luca Valenti
- c Department of Pathophysiology and Transplantation , Università Degli Studi Di Milano , Milano , Italy ;,d Internal Medicine and Metabolic Diseases , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
| | - Paola Dongiovanni
- d Internal Medicine and Metabolic Diseases , Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milano , Italy
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Roubtsova A, Chamberland A, Marcinkiewicz J, Essalmani R, Fazel A, Bergeron JJ, Seidah NG, Prat A. PCSK9 deficiency unmasks a sex- and tissue-specific subcellular distribution of the LDL and VLDL receptors in mice. J Lipid Res 2015; 56:2133-42. [PMID: 26323289 DOI: 10.1194/jlr.m061952] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Indexed: 01/01/2023] Open
Abstract
Proprotein convertase subtilisin kexin type 9 (PCSK9), the last member of the family of Proprotein Convertases related to Subtilisin and Kexin, regulates LDL-cholesterol by promoting the endosomal/lysosomal degradation of the LDL receptor (LDLR). Herein, we show that the LDLR cell surface levels dramatically increase in the liver and pancreatic islets of PCSK9 KO male but not female mice. In contrast, in KO female mice, the LDLR is more abundant at the cell surface enterocytes, as is the VLDL receptor (VLDLR) at the cell surface of adipocytes. Ovariectomy of KO female mice led to a typical KO male pattern, whereas 17β-estradiol (E2) treatment restored the female pattern without concomitant changes in LDLR adaptor protein 1 (also known as ARH), disabled-2, or inducible degrader of the LDLR expression levels. We also show that this E2-mediated regulation, which is observed only in the absence of PCSK9, is abolished upon feeding the mice a high-cholesterol diet. The latter dramatically represses PCSK9 expression and leads to high surface levels of the LDLR in the hepatocytes of all sexes and genotypes. In conclusion, the absence of PCSK9 results in a sex- and tissue-specific subcellular distribution of the LDLR and VLDLR, which is determined by E2 levels.
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Affiliation(s)
- Anna Roubtsova
- Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal (affiliated with the University of Montreal), Montreal, Quebec, Canada
| | - Ann Chamberland
- Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal (affiliated with the University of Montreal), Montreal, Quebec, Canada
| | - Jadwiga Marcinkiewicz
- Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal (affiliated with the University of Montreal), Montreal, Quebec, Canada
| | - Rachid Essalmani
- Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal (affiliated with the University of Montreal), Montreal, Quebec, Canada
| | - Ali Fazel
- Department of Medicine, McGill University Hospital Research Institute, Montreal, Quebec, Canada
| | - John J Bergeron
- Department of Medicine, McGill University Hospital Research Institute, Montreal, Quebec, Canada
| | - Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal (affiliated with the University of Montreal), Montreal, Quebec, Canada
| | - Annik Prat
- Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal (affiliated with the University of Montreal), Montreal, Quebec, Canada
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Starr AE, Lemieux V, Noad J, Moore JI, Dewpura T, Raymond A, Chrétien M, Figeys D, Mayne J. β-Estradiol results in a proprotein convertase subtilisin/kexin type 9-dependent increase in low-density lipoprotein receptor levels in human hepatic HuH7 cells. FEBS J 2015; 282:2682-96. [PMID: 25913303 PMCID: PMC5008176 DOI: 10.1111/febs.13309] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 03/28/2015] [Accepted: 04/22/2015] [Indexed: 12/23/2022]
Abstract
The lower risk of coronary artery disease in premenopausal women than in men and postmenopausal women implicates sex steroids in cardioprotective processes. β-Estradiol upregulates liver low-density lipoprotein receptor (LDLR), which, in turn, decreases circulating levels of low-density lipoprotein, which is a risk factor for coronary artery disease. Conversely, LDLR protein is negatively regulated by proprotein convertase subtilisin/kexin type 9 (PCSK9). Herein, we investigated PCSK9 regulation by β-estradiol and its impact on LDLR in human hepatocarcinoma HuH7 cells grown in the presence or absence of β-estradiol. Immunoblot analysis showed upregulation of LDLR at 3 μm β-estradiol (140%), and the upregulation reached 220% at 10 μm β-estradiol; only at the latter dose was an increase in LDLR mRNA detected by qPCR, suggesting post-translational regulation of LDLR. No changes in PCSK9 mRNA or secreted protein levels were detected by qPCR or ELISA, respectively. β-estradiol-conditioned medium devoid of PCSK9 failed to upregulate LDLR. Similarly, PCSK9 knockdown cells showed no upregulation of LDLR by β-estradiol. Together, these results indicate a requirement for PCSK9 in the β-estradiol-induced upregulation of LDLR. A radiolabeling assay showed a significant, dose-dependent decrease in the ratio of secreted phosphoPCSK9 to total secreted PCSK9 with increasing β-estradiol levels, suggesting a change in the functional state of PCSK9 in the presence of β-estradiol. Our results indicate that the protein upregulation of LDLR at subtranscriptionally effective doses of β-estradiol, and its supratranscriptional upregulation at 10 μm β-estradiol, occur through an extracellular PCSK9-dependent mechanism.
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Affiliation(s)
- Amanda E Starr
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Valérie Lemieux
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Jenny Noad
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Jasmine I Moore
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Thilina Dewpura
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Angela Raymond
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Michel Chrétien
- Chronic Disease Program, Ottawa Hospital Research Institute, The Ottawa Hospital, Ontario, Canada.,Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Quebec, Canada
| | - Daniel Figeys
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
| | - Janice Mayne
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada
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