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Vasseur S, Guillaumond F. [Pancreatic adenocarcinoma: a tumor highly dependent on lipoproteins]. Med Sci (Paris) 2015; 31:728-30. [PMID: 26340830 DOI: 10.1051/medsci/20153108009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sophie Vasseur
- Inserm U1068, Centre de recherche en cancérologie de Marseille, F-13288 Marseille, France - Institut Paoli-Calmettes, F-13009 Marseille, France - CNRS, UMR7258, F-13009 Marseille, France - Université Aix-Marseille, F-13009 Marseille, France
| | - Fabienne Guillaumond
- Inserm U1068, Centre de recherche en cancérologie de Marseille, F-13288 Marseille, France - Institut Paoli-Calmettes, F-13009 Marseille, France - CNRS, UMR7258, F-13009 Marseille, France - Université Aix-Marseille, F-13009 Marseille, France
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52
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Gu HM, Zhang DW. Hypercholesterolemia, low density lipoprotein receptor and proprotein convertase subtilisin/kexin-type 9. J Biomed Res 2015; 29:356-61. [PMID: 26445568 PMCID: PMC4585429 DOI: 10.7555/jbr.29.20150067] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Accepted: 06/09/2015] [Indexed: 01/15/2023] Open
Abstract
Atherosclerotic cardiovascular disease is the main cause of mortality and morbidity in the world. Plasma levels of low density lipoprotein cholesterol (LDL-C) are positively correlated with the risk of atherosclerosis. High plasma LDL concentrations in patients with hypercholesterolemia lead to build-up of LDL in the inner walls of the arteries, which becomes oxidized and promotes the formation of foam cells, consequently initiating atherosclerosis. Plasma LDL is mainly cleared through the LDL receptor (LDLR) pathway. Mutations in the LDLR cause familiar hypercholesterolemia and increase the risk of premature coronary heart disease. The expression of LDLR is regulated at the transcriptional level via the sterol regulatory element binding protein 2 (SREBP-2) and at the posttranslational levels mainly through proprotein convertase subtilisin/kexin-type 9 (PCSK9) and inducible degrader of the LDLR (IDOL). In this review, we summarize the latest advances in the studies of PCSK9.
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Affiliation(s)
- Hong-Mei Gu
- Departments of Pediatrics and Biochemistry, Group on the Molecular and Cell Biology of Lipids, University of Alberta , Edmonton, Alberta, T6G 2S2 , Canada
| | - Da-Wei Zhang
- Departments of Pediatrics and Biochemistry, Group on the Molecular and Cell Biology of Lipids, University of Alberta , Edmonton, Alberta, T6G 2S2 , Canada
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53
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Butkinaree C, Canuel M, Essalmani R, Poirier S, Benjannet S, Asselin MC, Roubtsova A, Hamelin J, Marcinkiewicz J, Chamberland A, Guillemot J, Mayer G, Sisodia SS, Jacob Y, Prat A, Seidah NG. Amyloid Precursor-like Protein 2 and Sortilin Do Not Regulate the PCSK9 Convertase-mediated Low Density Lipoprotein Receptor Degradation but Interact with Each Other. J Biol Chem 2015; 290:18609-20. [PMID: 26085104 DOI: 10.1074/jbc.m115.647180] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Indexed: 01/07/2023] Open
Abstract
Amyloid precursor-like protein 2 (APLP2) and sortilin were reported to individually bind the proprotein convertase subtilisin/kexin type 9 (PCSK9) and regulate its activity on the low-density lipoprotein receptor (LDLR). The data presented herein demonstrate that mRNA knockdowns of APLP2, sortilin, or both in the human hepatocyte cell lines HepG2 and Huh7 do not affect the ability of extracellular PCSK9 to enhance the degradation of the LDLR. Furthermore, mice deficient in APLP2 or sortilin do not exhibit significant changes in liver LDLR or plasma total cholesterol levels. Moreover, cellular overexpression of one or both proteins does not alter PCSK9 secretion, or its activity on the LDLR. We conclude that PCSK9 enhances the degradation of the LDLR independently of either APLP2 or sortilin both ex vivo and in mice. Interestingly, when co-expressed with PCSK9, both APLP2 and sortilin were targeted for lysosomal degradation. Using chemiluminescence proximity and co-immunoprecipitation assays, as well as biosynthetic analysis, we discovered that sortilin binds and stabilizes APLP2, and hence could regulate its intracellular functions on other targets.
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Affiliation(s)
- Chutikarn Butkinaree
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Maryssa Canuel
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Rachid Essalmani
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Steve Poirier
- the Laboratory of Molecular Cell Biology, Montreal Heart Institute, 5000 Bélanger, Montréal, Quebec H1T 1C8, Canada
| | - Suzanne Benjannet
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Marie-Claude Asselin
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Anna Roubtsova
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Josée Hamelin
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Jadwiga Marcinkiewicz
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Ann Chamberland
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Johann Guillemot
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Gaétan Mayer
- the Laboratory of Molecular Cell Biology, Montreal Heart Institute, 5000 Bélanger, Montréal, Quebec H1T 1C8, Canada
| | - Sangram S Sisodia
- the Department of Neurobiology, University of Chicago, Chicago, Illinois 60637
| | - Yves Jacob
- the Département de Virologie, Institut Pasteur, Unité de Génétique Moléculaire des Virus à ARN, F-75015 Paris, France, the CNRS, URA3015, F-75015 Paris, France, and the Université Paris Diderot, Sorbonne Paris Cité, Unité de Génétique Moléculaire des Virus à ARN, F-75015 Paris, France
| | - Annik Prat
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Nabil G Seidah
- From the Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec H2W 1R7, Canada,
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Romagnuolo R, Scipione CA, Boffa MB, Marcovina SM, Seidah NG, Koschinsky ML. Lipoprotein(a) catabolism is regulated by proprotein convertase subtilisin/kexin type 9 through the low density lipoprotein receptor. J Biol Chem 2015; 290:11649-62. [PMID: 25778403 DOI: 10.1074/jbc.m114.611988] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Indexed: 01/07/2023] Open
Abstract
Elevated levels of lipoprotein(a) (Lp(a)) have been identified as an independent risk factor for coronary heart disease. Plasma Lp(a) levels are reduced by monoclonal antibodies targeting proprotein convertase subtilisin/kexin type 9 (PCSK9). However, the mechanism of Lp(a) catabolism in vivo and the role of PCSK9 in this process are unknown. We report that Lp(a) internalization by hepatic HepG2 cells and primary human fibroblasts was effectively reduced by PCSK9. Overexpression of the low density lipoprotein (LDL) receptor (LDLR) in HepG2 cells dramatically increased the internalization of Lp(a). Internalization of Lp(a) was markedly reduced following treatment of HepG2 cells with a function-blocking monoclonal antibody against the LDLR or the use of primary human fibroblasts from an individual with familial hypercholesterolemia; in both cases, Lp(a) internalization was not affected by PCSK9. Optimal Lp(a) internalization in both hepatic and primary human fibroblasts was dependent on the LDL rather than the apolipoprotein(a) component of Lp(a). Lp(a) internalization was also dependent on clathrin-coated pits, and Lp(a) was targeted for lysosomal and not proteasomal degradation. Our data provide strong evidence that the LDLR plays a role in Lp(a) catabolism and that this process can be modulated by PCSK9. These results provide a direct mechanism underlying the therapeutic potential of PCSK9 in effectively lowering Lp(a) levels.
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Affiliation(s)
- Rocco Romagnuolo
- From the Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | - Corey A Scipione
- From the Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | - Michael B Boffa
- From the Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | - Santica M Marcovina
- the Northwest Lipid Metabolism and Diabetes Research Laboratories, University of Washington, Seattle, Washington 98109, and
| | - Nabil G Seidah
- the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, Montréal, Québec H2W 1R7, Canada
| | - Marlys L Koschinsky
- From the Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada,
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55
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Liu J, Ma KL, Zhang Y, Wu Y, Hu ZB, Lv LL, Tang RN, Liu H, Ruan XZ, Liu BC. Activation of mTORC1 disrupted LDL receptor pathway: a potential new mechanism for the progression of non-alcoholic fatty liver disease. Int J Biochem Cell Biol 2015; 61:8-19. [PMID: 25622557 DOI: 10.1016/j.biocel.2015.01.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 12/22/2014] [Accepted: 01/16/2015] [Indexed: 10/24/2022]
Abstract
Our previous studies demonstrated that inflammation exacerbates the progression of non-alcoholic fatty liver disease (NAFLD) by disrupting cholesterol homeostasis. This study aimed to investigate the role of mammalian target of rapamycin complex 1 (mTORC1) in NAFLD under conditions of inflammation. Chronic inflammation was induced by using subcutaneous injections of 10% casein in apolipoprotein E knockout (ApoE KO) mice in vivo and interleukin-1β stimulation of the HepG2 hepatoblastoma cell line in vitro. Results demonstrated that inflammation increased lipid accumulation in HepG2 cells and in livers of apolipoprotein E knockout mice. These effects were correlated with an increase in low density lipoprotein receptor (LDLR) gene transcription, which was mediated through the up-regulation of sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), SREBP-2, and through enhanced translocation of the SCAP/SREBP-2 complex from endoplasmic reticulum (ER) to Golgi. In addition, our data indicated that inflammation down-regulated the expression of proprotein convertase subtilisin kexin 9 (PCSK9) and prevented the degradation of LDLR protein via posttranscriptional mechanisms. Further analysis showed that inflammation increased the protein phosphorylation of mTOR, eukaryotic initiation factor 4E-binding protein 1, and p70 S6 kinase. Interestingly, blocking mTORC1 activity inhibited the translocation of SCAP/SREBP-2 complex from the ER to the Golgi and decreased the expression of LDLR, SCAP, and SREBP-2. These effects were accompanied by an increase in the expression of PCSK9 and accelerated LDLR degradation. Our findings demonstrated that increased mTORC1 activity exacerbated the progression of NAFLD by disrupting LDLR expression via transcriptional and posttranscriptional mechanisms.
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Affiliation(s)
- Jing Liu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Kun Ling Ma
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China.
| | - Yang Zhang
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Yu Wu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Ze Bo Hu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Lin Li Lv
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Ri Ning Tang
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Hong Liu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
| | - Xiong Zhong Ruan
- Centre for Nephrology, University College London (UCL) Medical School, Royal Free Campus, UK
| | - Bi Cheng Liu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing City, Jiangsu Province, China
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Schulz R, Schlüter KD, Laufs U. Molecular and cellular function of the proprotein convertase subtilisin/kexin type 9 (PCSK9). Basic Res Cardiol 2015; 110:4. [PMID: 25600226 PMCID: PMC4298671 DOI: 10.1007/s00395-015-0463-z] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/04/2015] [Accepted: 01/07/2015] [Indexed: 12/16/2022]
Abstract
The proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a promising treatment target to lower serum cholesterol, a major risk factor of cardiovascular diseases. Gain-of-function mutations of PCSK9 are associated with hypercholesterolemia and increased risk of cardiovascular events. Conversely, loss-of-function mutations cause low-plasma LDL-C levels and a reduction of cardiovascular risk without known unwanted effects on individual health. Experimental studies have revealed that PCSK9 reduces the hepatic uptake of LDL-C by increasing the endosomal and lysosomal degradation of LDL receptors (LDLR). A number of clinical studies have demonstrated that inhibition of PCSK9 alone and in addition to statins potently reduces serum LDL-C concentrations. This review summarizes the current data on the regulation of PCSK9, its molecular function in lipid homeostasis and the emerging evidence on the extra-hepatic effects of PCSK9.
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Affiliation(s)
- Rainer Schulz
- Physiologisches Institut, Justus-Liebig Universität Giessen, Aulweg 129, 35392, Giessen, Germany,
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57
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Kwiterovich PO. Detection and Treatment of Children and Adolescents with Dyslipidemia. DYSLIPIDEMIAS 2015. [DOI: 10.1007/978-1-60761-424-1_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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58
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PCSK9 inhibition in LDL cholesterol reduction: Genetics and therapeutic implications of very low plasma lipoprotein levels. Pharmacol Ther 2015; 145:58-66. [DOI: 10.1016/j.pharmthera.2014.07.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 07/11/2014] [Indexed: 01/15/2023]
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Affiliation(s)
- Murray W Huff
- From the Department of Medicine, Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
| | - Julia M Assini
- From the Department of Medicine, Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Robert A Hegele
- From the Department of Medicine, Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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60
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Sharpe LJ, Cook ECL, Zelcer N, Brown AJ. The UPS and downs of cholesterol homeostasis. Trends Biochem Sci 2014; 39:527-35. [PMID: 25220377 DOI: 10.1016/j.tibs.2014.08.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/18/2014] [Accepted: 08/21/2014] [Indexed: 11/26/2022]
Abstract
An emerging theme in the regulation of cholesterol homeostasis is the role of the ubiquitin proteasome system (UPS), through which proteins are ubiquitylated and then degraded in response to specific signals. The UPS controls all aspects of cholesterol metabolism including its synthesis, uptake, and efflux. We review here recent work uncovering the ubiquitylation and degradation of key players in cholesterol homeostasis. This includes the low-density lipoprotein (LDL) receptor, transcription factors (sterol regulatory element binding proteins and liver X receptors), flux-controlling enzymes in cholesterol synthesis (3-hydroxy-3-methylglutaryl-CoA reductase and squalene monooxygenase), and cholesterol exporters (ATP-binding cassette transporters ABCA1 and ABCG1). We explore which E3 ligases are involved, and identify areas deserving of further research.
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Affiliation(s)
- Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Emma C L Cook
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands
| | - Noam Zelcer
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands.
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia.
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61
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Sorting an LDL receptor with bound PCSK9 to intracellular degradation. Atherosclerosis 2014; 237:76-81. [PMID: 25222343 DOI: 10.1016/j.atherosclerosis.2014.08.038] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/28/2014] [Accepted: 08/19/2014] [Indexed: 11/21/2022]
Abstract
OBJECTIVE This article reviews the mechanism by which the low density lipoprotein receptor (LDLR) that has bound proprotein convertase subtilisin/kexin type 9 (PCSK9), is rerouted to intracellular degradation instead of being recycled. METHODS A search of relevant published literature has been conducted. RESULTS PCSK9 binds to the LDLR at the cell surface. It is the catalytic domain of PCSK9 that binds to the epidermal growth factor repeat A of the LDLR. The LDLR:PCSK9 complex is internalized through clathrin-mediated endocytosis. Due to an additional electrostatic interaction at acidic pH between the C-terminal domain of PCSK9 and the ligand-binding domain of the LDLR, PCSK9 remains bound to the LDLR in the sorting endosome. As a consequence, the LDLR fails to adopt a closed conformation and is degraded instead of being recycled. The mechanism for the failure of the LDLR to recycle appears to involve ectodomain cleavage of the extended LDLR by a cysteine cathepsin in the sorting endosome. The cleaved LDLR ectodomain will be confined to the vesicular part of the sorting endosome for degradation in the endosomal/lysosomal tract. CONCLUSION Ectodomain cleavage of an LDLR with bound PCSK9 in the sorting endosome disrupts the normal recycling of the LDLR.
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Layeghkhavidaki H, Lanhers MC, Akbar S, Gregory-Pauron L, Oster T, Grova N, Appenzeller B, Jasniewski J, Feidt C, Corbier C, Yen FT. Inhibitory action of benzo[α]pyrene on hepatic lipoprotein receptors in vitro and on liver lipid homeostasis in mice. PLoS One 2014; 9:e102991. [PMID: 25054229 PMCID: PMC4108373 DOI: 10.1371/journal.pone.0102991] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 06/25/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Dyslipidemia associated with obesity often manifests as increased plasma LDL and triglyceride-rich lipoprotein levels suggesting changes in hepatic lipoprotein receptor status. Persistent organic pollutants have been recently postulated to contribute to the obesity etiology by increasing adipogenesis, but little information is available on their potential effect on hepatic lipoprotein metabolism. OBJECTIVE The objective of this study was to investigate the effect of the common environmental pollutant, benzo[α]pyrene (B[α]P) on two lipoprotein receptors, the LDL-receptor and the lipolysis-stimulated lipoprotein receptor (LSR) as well as the ATP-binding cassette transporter A1 (ABCA1) using cell and animal models. RESULTS LSR, LDL-receptor as well as ABCA1 protein levels were significantly decreased by 26-48% in Hepa1-6 cells incubated (<2 h) in the presence of B[α]P (≤1 µM). Real-time PCR analysis and lactacystin studies revealed that this effect was due primarily to increased proteasome, and not lysosomal-mediated degradation rather than decreased transcription. Furthermore, ligand blots revealed that lipoproteins exposed to 1 or 5 µM B[α]P displayed markedly decreased (42-86%) binding to LSR or LDL-receptor. B[α]P-treated (0.5 mg/kg/48 h, i.p. 15 days) C57BL/6J mice displayed higher weight gain, associated with significant increases in plasma cholesterol, triglycerides, and liver cholesterol content, and decreased hepatic LDL-receptor and ABCA1 levels. Furthermore, correlational analysis revealed that B[α]P abolished the positive association observed in control mice between the LSR and LDL-receptor. Interestingly, levels of other proteins involved in liver cholesterol metabolism, ATP-binding cassette transporter G1 and scavenger receptor-BI, were decreased, while those of acyl-CoA:cholesterol acyltransferase 1 and 2 were increased in B[α]P-treated mice. CONCLUSIONS B[α]P demonstrates inhibitory action on LSR and LDL-R, as well as ABCA1, which we propose leads to modified lipid status in B[α]P-treated mice, thus providing new insight into mechanisms underlying the involvement of pollutants in the disruption of lipid homeostasis, potentially contributing to dyslipidemia associated with obesity.
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Affiliation(s)
- Hamed Layeghkhavidaki
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Marie-Claire Lanhers
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Samina Akbar
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Lynn Gregory-Pauron
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Thierry Oster
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Nathalie Grova
- Laboratory of Analytical Human Biomonitoring, Centre de Recherche Public de la Santé, Luxembourg, Luxembourg
| | - Brice Appenzeller
- Laboratory of Analytical Human Biomonitoring, Centre de Recherche Public de la Santé, Luxembourg, Luxembourg
| | - Jordane Jasniewski
- Laboratoire d'Ingenérie des Biomolécules, Université de Lorraine, Vandœuvre-lès-Nancy, France
| | - Cyril Feidt
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Catherine Corbier
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
| | - Frances T. Yen
- Unité de Recherche Animal et Fonctionnalités des Produits Animaux EA3998, Université de Lorraine, Vandœuvre-lès-Nancy, France
- Institut National de Recherche Agronomique USC 0340, Vandœuvre-lès-Nancy, France
- Institut National de la Santé et de la Recherche Médicale, Vandœuvre-lès-Nancy, France
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Somanathan S, Jacobs F, Wang Q, Hanlon AL, Wilson JM, Rader DJ. AAV vectors expressing LDLR gain-of-function variants demonstrate increased efficacy in mouse models of familial hypercholesterolemia. Circ Res 2014; 115:591-9. [PMID: 25023731 DOI: 10.1161/circresaha.115.304008] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
RATIONALE Familial hypercholesterolemia is a genetic disorder that arises because of loss-of-function mutations in the low-density lipoprotein receptor (LDLR) and homozygous familial hypercholesterolemia is a candidate for gene therapy using adeno-associated viral vectors. Proprotein convertase subtilisin/kexin type 9 (PCSK9) and inducible degrader of LDLR (IDOL) negatively regulate LDLR protein and could dampen adeno-associated viral vector encoded LDLR expression. OBJECTIVE We sought to create vectors expressing gain-of-function human LDLR variants that are resistant to degradation by human PCSK9 (hPCSK9) and IDOL and thereby enhance hepatic LDLR protein abundance and plasma LDL cholesterol reduction. METHODS AND RESULTS Amino acid substitutions were introduced into the coding sequence of human LDLR cDNA to reduce interaction with hPCSK9 and human IDOL. A panel of mutant human LDLRs was initially screened in vitro for escape from PCSK9. The variant human LDLR-L318D was further evaluated using a mouse model of homozygous familial hypercholesterolemia lacking endogenous LDLR and apolipoprotein B mRNA editing enzyme catalytic, APOBEC-1 (double knockout). Administration of wild-type human LDLR to double knockout mice, expressing hPCSK9, led to diminished LDLR activity. However, LDLR-L318D was resistant to hPCSK9-mediated degradation and effectively reduced cholesterol levels. Similarly, the LDLR-K809R\C818A construct avoided human IDOL regulation and achieved stable reductions in serum cholesterol. An adeno-associated viral vector serotype 8.LDLR-L318D\K809R\C818A vector that carried all 3 amino acid substitutions conferred partial resistance to both hPCSK9- and human IDOL-mediated degradation. CONCLUSIONS Amino acid substitutions in the human LDLR confer partial resistance to PCSK9 and IDOL regulatory pathways with improved reduction in cholesterol levels and improve on a potential gene therapeutic approach to treat homozygous familial hypercholesterolemia subjects.
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Affiliation(s)
- Suryanarayan Somanathan
- From the Gene Therapy Program, Department of Pathology and Laboratory Medicine (S.S., F.J., Q.W., J.M.W.), Department of Nursing Research, School of Nursing (A.L.H.), and Departments of Medicine and Genetics and Cardiovascular Institute (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; and Discovery Sciences, Janssen, Pharmaceutical companies of Johnson and Johnson, Beerse, Belgium (F.J.)
| | - Frank Jacobs
- From the Gene Therapy Program, Department of Pathology and Laboratory Medicine (S.S., F.J., Q.W., J.M.W.), Department of Nursing Research, School of Nursing (A.L.H.), and Departments of Medicine and Genetics and Cardiovascular Institute (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; and Discovery Sciences, Janssen, Pharmaceutical companies of Johnson and Johnson, Beerse, Belgium (F.J.)
| | - Qiang Wang
- From the Gene Therapy Program, Department of Pathology and Laboratory Medicine (S.S., F.J., Q.W., J.M.W.), Department of Nursing Research, School of Nursing (A.L.H.), and Departments of Medicine and Genetics and Cardiovascular Institute (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; and Discovery Sciences, Janssen, Pharmaceutical companies of Johnson and Johnson, Beerse, Belgium (F.J.)
| | - Alexandra L Hanlon
- From the Gene Therapy Program, Department of Pathology and Laboratory Medicine (S.S., F.J., Q.W., J.M.W.), Department of Nursing Research, School of Nursing (A.L.H.), and Departments of Medicine and Genetics and Cardiovascular Institute (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; and Discovery Sciences, Janssen, Pharmaceutical companies of Johnson and Johnson, Beerse, Belgium (F.J.)
| | - James M Wilson
- From the Gene Therapy Program, Department of Pathology and Laboratory Medicine (S.S., F.J., Q.W., J.M.W.), Department of Nursing Research, School of Nursing (A.L.H.), and Departments of Medicine and Genetics and Cardiovascular Institute (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; and Discovery Sciences, Janssen, Pharmaceutical companies of Johnson and Johnson, Beerse, Belgium (F.J.).
| | - Daniel J Rader
- From the Gene Therapy Program, Department of Pathology and Laboratory Medicine (S.S., F.J., Q.W., J.M.W.), Department of Nursing Research, School of Nursing (A.L.H.), and Departments of Medicine and Genetics and Cardiovascular Institute (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; and Discovery Sciences, Janssen, Pharmaceutical companies of Johnson and Johnson, Beerse, Belgium (F.J.)
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Getz GS. PCSK9 in South African variants of familial hypercholesterolemia. J Am Coll Cardiol 2014; 63:2374-5. [PMID: 24632264 DOI: 10.1016/j.jacc.2014.01.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 01/13/2014] [Indexed: 10/25/2022]
Affiliation(s)
- Godfrey S Getz
- Department of Pathology, University of Chicago, Chicago, Illinois.
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Jia YJ, Xu RX, Sun J, Tang Y, Li JJ. Enhanced circulating PCSK9 concentration by berberine through SREBP-2 pathway in high fat diet-fed rats. J Transl Med 2014; 12:103. [PMID: 24755036 PMCID: PMC4000533 DOI: 10.1186/1479-5876-12-103] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 04/14/2014] [Indexed: 11/28/2022] Open
Abstract
Background Berberine (BBR), a natural plant extract, has been shown to improve lipid metabolism. However, its effects on PCSK9, a key factor involving in the lipid metabolism, have not yet been evaluated in vivo. The aim of the present study was to investigate the effect of BBR on PCSK9 expression in high fat diet-fed (HFD) rats. Methods Thirty-two male Sprague Dawley (SD) rats were randomized into the four groups (n = 8): normal diet (Control), HFD, HFD + simvastatin (Sim, 2 mg/kg/d) and HDF + BBR (400 mg/kg/d) for 6 weeks. The following parameters were determined: 1) body weight; 2) serum lipid profile; 3) serum PCSK9 measured by enzyme-linked immuno sorbent assay (ELISA) ; 4) hepatic expressions of low-density lipoprotein receptor (LDLR), sterol regulatory element binding protein-2 (SREBP-2) and hepatocyte nuclear factor 1 (HNF1) were examined by real time quantitative polymerase chain reaction (RT-PCR) and western blotting analysis. Results Compared with HFD rats, Sim and BBR significantly reduced body weight gain and improved lipid profile (P < 0.05 respectively). In addition, either of drug treatment for 6 weeks could increase serum concentration of PCSK9 in HFD rats (P < 0.05). This enhanced PCSK9 expression was demonstrated to be associated with the up-regulation of hepatic expression of LDLR and SREBP-2 and the down-regulation of hepatic expression of HNF1 (P < 0.05 respectively). Conclusions The data provided the first line of the evidence that BBR, similar to the Sim, could increase the expression of PCSK9 levels in HFD rats through SREBP-2 activation, suggesting that impacts of BBR on lipid profile may also be linked to SREBP-2 pathway.
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Affiliation(s)
| | | | | | - Yue Tang
- Division of Dyslipidemia, State Key Laboratory of Cardiovascular Disease, Fu Wai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.
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Lambert G, Petrides F, Chatelais M, Blom DJ, Choque B, Tabet F, Wong G, Rye KA, Hooper AJ, Burnett JR, Barter PJ, Marais AD. Elevated plasma PCSK9 level is equally detrimental for patients with nonfamilial hypercholesterolemia and heterozygous familial hypercholesterolemia, irrespective of low-density lipoprotein receptor defects. J Am Coll Cardiol 2014; 63:2365-73. [PMID: 24632287 DOI: 10.1016/j.jacc.2014.02.538] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 01/09/2014] [Accepted: 02/11/2014] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Do elevated proprotein convertase subtilisin/kexin type 9 (PCSK9) levels constitute an even greater risk for patients who already have reduced low-density lipoprotein receptor (LDLR) levels, such as those with heterozygous familial hypercholesterolemia (HeFH)? BACKGROUND As a circulating inhibitor of LDLR, PCSK9 is an attractive target for lowering LDL-cholesterol (LDL-C) levels. METHODS Circulating PCSK9 levels were measured by enzyme-linked immunosorbent assay in nontreated patients with HeFH carrying a D206E (n = 237), V408M (n = 117), or D154N (n = 38) LDLR missense mutation and in normolipidemic controls (n = 152). Skin fibroblasts and lymphocytes were isolated from a subset of patients and grown in 0.5% serum and mevastatin with increasing amounts of recombinant PCSK9. LDLR abundance at the cell surface was determined by flow cytometry. RESULTS PCSK9 reduced LDLR expression in a dose-dependent manner in control and FH fibroblasts to similar extents, by up to 77 ± 8% and 82 ± 7%, respectively. Likewise, PCSK9 reduced LDLR abundance by 39 ± 8% in nonfamilial hypercholesterolemia (non-FH) and by 45 ± 10% in HeFH lymphocytes, irrespective of their LDLR mutation status. We found positive correlations of the same magnitude between PCSK9 and LDL-C levels in controls (beta = 0.22; p = 0.0003), D206E (beta = 0.20; p = 0.0002), V408M (beta = 0.24; p = 0.0002), and D154N (beta = 0.25; p = 0.048) patients with HeFH. The strengths of these associations were all similar. CONCLUSIONS Elevated PCSK9 levels are equally detrimental for patients with HeFH or non-FH: a 100-ng/ml increase in PCSK9 will lead to an increase in LDL-C of 0.20 to 0.25 mmol/l in controls and HeFH alike, irrespective of their LDLR mutation. This explains why patients with non-FH or HeFH respond equally well to monoclonal antibodies targeting PCSK9.
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Affiliation(s)
- Gilles Lambert
- Faculté de Médecine, Université de Nantes, UMR PhAN 1280, Nantes, France; Lipid Research Group, Heart Research Institute, Sydney, Australia.
| | - Francine Petrides
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Mathias Chatelais
- Faculté de Médecine, Université de Nantes, UMR PhAN 1280, Nantes, France
| | - Dirk J Blom
- Lipidology Division of Internal Medicine, MRC Cape Heart Group, University of Cape Town Health Science Faculty, Cape Town, South Africa
| | - Benjamin Choque
- Lipid Research Group, Heart Research Institute, Sydney, Australia
| | - Fatiha Tabet
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Gida Wong
- Lipid Research Group, Heart Research Institute, Sydney, Australia
| | - Kerry-Anne Rye
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Amanda J Hooper
- Royal Perth Hospital, Department of Clinical Biochemistry, PathWest Laboratory of Medicine WA, Perth, Australia; School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia; School of Medicine and Pharmacology, University of Western Australia, Perth, Australia
| | - John R Burnett
- Royal Perth Hospital, Department of Clinical Biochemistry, PathWest Laboratory of Medicine WA, Perth, Australia; School of Medicine and Pharmacology, University of Western Australia, Perth, Australia
| | - Philip J Barter
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - A David Marais
- Chemical Pathology Division of Clinical Laboratory Sciences, MRC Cape Heart Group, University of Cape Town Health Science Faculty, Cape Town, South Africa
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Nguyen MA, Kosenko T, Lagace TA. Internalized PCSK9 dissociates from recycling LDL receptors in PCSK9-resistant SV-589 fibroblasts. J Lipid Res 2013; 55:266-75. [PMID: 24296664 PMCID: PMC3886665 DOI: 10.1194/jlr.m044156] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Secreted PCSK9 binds to cell surface LDL receptor (LDLR) and directs the receptor for lysosomal degradation. PCSK9 is potent at inducing LDLR degradation in cultured liver-derived cells, but it is considerably less active in immortalized fibroblasts. We examined PCSK9 trafficking in SV-589 human skin fibroblasts incubated with purified recombinant wild-type PCSK9 or gain-of-function mutant PCSK9-D374Y with increased LDLR binding affinity. Despite LDLR-dependent PCSK9 uptake, cell surface LDLR levels in SV-589 fibroblasts were only modestly reduced by wild-type PCSK9, even at high nonphysiological concentrations (20 µg/ml). Internalized 125I-labeled wild-type PCSK9 underwent lysosomal degradation at high levels, indicating its dissociation from recycling LDLRs. PCSK9-D374Y (2 µg/ml) reduced cell surface LDLRs by approximately 50%, but this effect was still blunted compared with HepG2 hepatoma cells. Radioiodinated PCSK9-D374Y was degraded less efficiently in SV-589 fibroblasts, and Alexa488-labeled PCSK9-D374Y trafficked to both lysosomes and endocytic recycling compartments. Endocytic recycling assays showed that more than 50% of internalized PCSK9-D374Y recycled to the cell surface compared with less than 10% for wild-type PCSK9. These data support that wild-type PCSK9 readily dissociates from the LDLR within early endosomes of SV-589 fibroblasts, contributing to PCSK9-resistance. Although a large proportion of gain-of-function PCSK9-D374Y remains bound to LDLR in these cells, degradative activity is still diminished.
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Affiliation(s)
- My-Anh Nguyen
- Department of Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario, Canada K1Y 4W7
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Abstract
The three major pathways of lipoprotein metabolism provide a superb paradigm to delineate systematically the familial dyslipoproteinemias. Such understanding leads to improved diagnosis and treatment of patients. In the exogenous (intestinal) pathway, defects in LPL, apoC-II, APOA-V, and GPIHBP1 disrupt the catabolism of chylomicrons and hepatic uptake of their remnants, producing very high TG. In the endogenous (hepatic) pathway, six disorders affect the activity of the LDLR and markedly increase LDL. These include FH, FDB, ARH, PCSK9 gain-of-function mutations, sitosterolemia and loss of 7 alpha hydroxylase. Hepatic overproduction of VLDL occurs in FCHL, hyperapoB, LDL subclass pattern B, FDH and syndrome X, often due to insulin resistance and resulting in high TG, elevated small LDL particles and low HDL-C. Defects in APOB-100 and loss-of-function mutations in PCSK9 are associated with low LDL-C, decreased CVD and longevity. An absence of MTP leads to marked reduction in chylomicrons and VLDL, causing abetalipoproteinemia. In the reverse cholesterol pathway, deletions or nonsense mutations in apoA-I or ABCA1 transporter disrupt the formation of the nascent HDL particle. Mutations in LCAT disrupt esterification of cholesterol in nascent HDL by LCAT and apoA-1, and formation of spherical HDL. Mutations in either CETP or SR-B1 and familial high HDL lead to increased large HDL particles, the effect of which on CVD is not resolved. The major goal is to prevent or ameliorate the major complications of many familial dyslipoproteinemias, namely, premature CVD or pancreatitis. Dietary and drug treatment specific for each inherited disorder is reviewed.
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Affiliation(s)
- Peter O Kwiterovich
- Lipid Research Atherosclerosis Center, Helen Taussig Center, The Johns Hopkins University School of Medicine, David Rubenstein Building, Suite 3093, 200 N Wolfe St, Baltimore, MD 21287, USA.
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Gu HM, Adijiang A, Mah M, Zhang DW. Characterization of the role of EGF-A of low density lipoprotein receptor in PCSK9 binding. J Lipid Res 2013; 54:3345-57. [PMID: 24103783 DOI: 10.1194/jlr.m041129] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Proprotein convertase subtilisin kexin-like 9 (PCSK9) promotes the degradation of low density lipoprotein receptor (LDLR) and plays an important role in regulating plasma LDL-cholesterol levels. We have shown that the epidermal growth factor precursor homology domain A (EGF-A) of the LDLR is critical for PCSK9 binding at the cell surface (pH 7.4). Here, we further characterized the role of EGF-A in binding of PCSK9 to the LDLR. We found that PCSK9 efficiently bound to the LDLR but not to other LDLR family members. Replacement of EGF-A in the very low density lipoprotein receptor (VLDLR) with EGF-A of the LDLR promoted the degradation of the mutant VLDLR induced by PCSK9. Furthermore, we found that PCSK9 bound to recombinant EGF-A in a pH-dependent manner with stronger binding at pH 6.0. We also identified amino acid residues in EGF-A of the LDLR important for PCSK9 binding. Mutations G293H, D299V, L318D, and L318H reduced PCSK9 binding to the LDLR at neutral pH without effect at pH 6.0, while mutations R329P and E332G reduced PCSK9 binding at both pH values. Thus, our findings reveal that EGF-A of the LDLR is critical for PCSK9 binding at the cell surface (neutral pH) and at the acidic endosomal environment (pH 6.0), but different determinants contribute to efficient PCSK9 binding in different pH environments.
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Affiliation(s)
- Hong-mei Gu
- Departments of Pediatrics and Biochemistry, Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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Poirier S, Mayer G. The biology of PCSK9 from the endoplasmic reticulum to lysosomes: new and emerging therapeutics to control low-density lipoprotein cholesterol. DRUG DESIGN DEVELOPMENT AND THERAPY 2013; 7:1135-48. [PMID: 24115837 PMCID: PMC3793591 DOI: 10.2147/dddt.s36984] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Proprotein convertase subtilisin/kexin type 9 (PCSK9) directly binds to the epidermal growth factor-like repeat A domain of low-density lipoprotein receptor and induces its degradation, thereby controlling circulating low-density lipoprotein cholesterol (LDL-C) concentration. Heterozygous loss-of-function mutations in PCSK9 can decrease the incidence of coronary heart disease by up to 88%, owing to lifelong reduction of LDL-C. Moreover, two subjects with PCSK9 loss-of-function mutations on both alleles, resulting in a total absence of functional PCSK9, were found to have extremely low circulating LDL-C levels without other apparent abnormalities. Accordingly, PCSK9 could represent a safe and effective pharmacological target to increase clearance of LDL-C and to reduce the risk of coronary heart disease. Recent clinical trials using anti-PCSK9 monoclonal antibodies that block the PCSK9:low-density lipoprotein receptor interaction were shown to considerably reduce LDL-C levels by up to 65% when given alone and by up to 72% in patients already receiving statin therapy. In this review, we will discuss how major scientific breakthroughs in PCSK9 cell biology have led to the development of new and forthcoming LDL-C-lowering pharmacological agents.
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Affiliation(s)
- Steve Poirier
- Laboratory of Molecular Cell Biology, Montreal Heart institute, Montréal, QC, Canada ; Départements de Pharmacologie, Montréal, Université de Montréal, Montréal, QC, Canada
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Abstract
PURPOSE OF REVIEW In the past 10 years, the LDL receptor inhibitor proprotein convertase subtilisin kexin type 9 (PCSK9) has emerged as a validated target for lowering plasma LDL cholesterol levels. Here we review the most recent reports on PCSK9 out of a total of 500 publications published in print or online before March 2013 and indexed on PubMed. RECENT FINDINGS All published in 2012, phase I and II clinical trials demonstrate that fully human monoclonal antibodies targeting PCSK9 dramatically reduce LDL-C and enable patients to reach their target goals, without severe or serious safety issues. SUMMARY This review summarizes the discovery of PCSK9, its original mode of action as a secreted inhibitor of the LDL receptor, as well as its genetic regulation by statins. We then focus on the major results from the 2012 phase I and II PCSK9 inhibitor clinical trials. We also review the recent in-vivo studies demonstrating the potential cardiovascular benefits of long-term PCSK9 inhibition and discuss its potential side-effects.
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Affiliation(s)
- Francine Petrides
- The University of New South Wales, Sydney, New South Wales, Australia
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Stein EA, Swergold GD. Potential of proprotein convertase subtilisin/kexin type 9 based therapeutics. Curr Atheroscler Rep 2013; 15:310. [PMID: 23371064 DOI: 10.1007/s11883-013-0310-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The link between proprotein convertase subtilisin/kexin type 9 (PCSK9) and cholesterol metabolism was established only in 2003 when genetic mapping and positional cloning in patients with autosomal dominant hypercholesterolemia in which linkage to the loci coding for the LDL receptor and apolipoprotein B had been excluded identified the genetic defect missense as mutations in PCSK9, a protein/enzyme previously unknown to be related to lipid metabolism. Laboratory-based investigations confirmed that these were gain-of-function mutations. Further studies in cohorts with low LDL cholesterol (LDLc) levels from large epidemiological cardiovascular studies reported that loss-of-function mutations in PCSK9 were associated with protection from cardiovascular disease. An additional critical observation provided evidence that the interaction of PCSK9 and the LDL receptor was through circulating, not intracellular, PCSK9, which bound to the receptor, and then mediated the recycling of the LDL receptor. These findings established PSCK9 as a potential therapeutic target and resulted in biopharmaceutical companies developing interventions designed to lower LDLc levels. Clinical development programs for monoclonal antibodies against PCSK9 have advanced rapidly with completion of comprehensive phase 1 and 2 trials with both REGN727/SAR236553 (REGN727) and AMG 145, clearly demonstrating substantial reductions in LDLc levels in patients receiving diet alone, low, moderate, and high doses of statins, or statin combined with ezetimibe, and both heterozygous familial hypercholesterolemia and nonfamilial hypercholesterolemia subjects. Concomitant and parallel reductions in the levels of apolipoprotein B and its related lipoproteins, and small but significant increases in HDL cholesterol levels were seen as anticipated. An unanticipated and robust decrease in lipoprotein(a) levels was also noted. Although these trials have been relatively short term, no significant safety issues or target organs of interest have emerged. Larger and much longer phase 3 trials are now in progress to assess the long-term tolerability, safety, and impact on cardiovascular disease events of these very effective LDLc lowering compounds.
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Affiliation(s)
- Evan A Stein
- Metabolic & Atherosclerosis Research Center and Medpace Reference Laboratories, 5355 Medpace Way, Cincinnati, OH, USA.
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Pietiäinen V, Vassilev B, Blom T, Wang W, Nelson J, Bittman R, Bäck N, Zelcer N, Ikonen E. NDRG1 functions in LDL receptor trafficking by regulating endosomal recycling and degradation. J Cell Sci 2013; 126:3961-71. [PMID: 23813961 DOI: 10.1242/jcs.128132] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
N-myc downstream-regulated gene 1 (NDRG1) mutations cause Charcot-Marie-Tooth disease type 4D (CMT4D). However, the cellular function of NDRG1 and how it causes CMT4D are poorly understood. We report that NDRG1 silencing in epithelial cells results in decreased uptake of low-density lipoprotein (LDL) due to reduced LDL receptor (LDLR) abundance at the plasma membrane. This is accompanied by the accumulation of LDLR in enlarged EEA1-positive endosomes that contain numerous intraluminal vesicles and sequester ceramide. Concomitantly, LDLR ubiquitylation is increased but its degradation is reduced and ESCRT (endosomal sorting complex required for transport) proteins are downregulated. Co-depletion of IDOL (inducible degrader of the LDLR), which ubiquitylates the LDLR and promotes its degradation, rescues plasma membrane LDLR levels and LDL uptake. In murine oligodendrocytes, Ndrg1 silencing not only results in reduced LDL uptake but also in downregulation of the oligodendrocyte differentiation factor Olig2. Both phenotypes are rescued by co-silencing of Idol, suggesting that ligand uptake through LDLR family members controls oligodendrocyte differentiation. These findings identify NDRG1 as a novel regulator of multivesicular body formation and endosomal LDLR trafficking. The deficiency of functional NDRG1 in CMT4D might impair lipid processing and differentiation of myelinating cells.
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Affiliation(s)
- Vilja Pietiäinen
- Institute of Biomedicine, Anatomy, University of Helsinki, Helsinki, Finland.
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Sorrentino V, Nelson JK, Maspero E, Marques ARA, Scheer L, Polo S, Zelcer N. The LXR-IDOL axis defines a clathrin-, caveolae-, and dynamin-independent endocytic route for LDLR internalization and lysosomal degradation. J Lipid Res 2013; 54:2174-2184. [PMID: 23733886 DOI: 10.1194/jlr.m037713] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Low density lipoprotein (LDL) cholesterol is taken up into cells via clathrin-mediated endocytosis of the LDL receptor (LDLR). Following dissociation of the LDLR-LDL complex, LDL is directed to lysosomes whereas the LDLR recycles to the plasma membrane. Activation of the sterol-sensing nuclear receptors liver X receptors (LXRs) enhances degradation of the LDLR. This depends on the LXR target gene inducible degrader of the LDLR (IDOL), an E3-ubiquitin ligase that promotes ubiquitylation and lysosomal degradation of the LDLR. How ubiquitylation of the LDLR by IDOL controls its endocytic trafficking is currently unknown. Using genetic- and pharmacological-based approaches coupled to functional assessment of LDL uptake, we show that the LXR-IDOL axis targets a LDLR pool present in lipid rafts. IDOL-dependent internalization of the LDLR is independent of clathrin, caveolin, macroautophagy, and dynamin. Rather, it depends on the endocytic protein epsin. Consistent with LDLR ubiquitylation acting as a sorting signal, degradation of the receptor can be blocked by perturbing the endosomal sorting complex required for transport (ESCRT) or by USP8, a deubiquitylase implicated in sorting ubiquitylated cargo to multivesicular bodies. In summary, we provide evidence for the existence of an LXR-IDOL-mediated internalization pathway for the LDLR that is distinct from that used for lipoprotein uptake.
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Affiliation(s)
- Vincenzo Sorrentino
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Jessica K Nelson
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Elena Maspero
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, 20139 Milan, Italy; and
| | - André R A Marques
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Lilith Scheer
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Simona Polo
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, 20139 Milan, Italy; and; Dipartimento di Scienze della Salute, Universita' degli Studi di Milano, 20122 Milan, Italy
| | - Noam Zelcer
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands.
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Affiliation(s)
- Jonathan C Cohen
- Departments of Internal Medicine and Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Sniderman A, Kwiterovich PO. Update on the detection and treatment of atherogenic low-density lipoproteins. Curr Opin Endocrinol Diabetes Obes 2013; 20:140-7. [PMID: 23422241 DOI: 10.1097/med.0b013e32835ed9cb] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
PURPOSE OF REVIEW To explain why epidemiological studies have reached such diverse views as to whether apolipoprotein B (apoB) and/or low-density lipoprotein particle number (LDL-P) are more accurate markers of the risk of cardiovascular disease than LDL-C or non-high-density lipoprotein cholesterol (HDL-C) and to review the treatment options to lower LDL. RECENT FINDINGS The Emerging Risk Factor Collaboration, a large prospective participant level analysis, a meta-analysis of statin clinical trials, and the Heart Protection Study have each reported that apoB does not add significantly to the cholesterol markers as indices of cardiovascular risk. By contrast, a meta-analysis of published prospective studies demonstrated that non-HDL-C was superior to LDL-C, and apoB was superior to non-HDL-C. As well, three studies using discordance analysis each demonstrated that apoB and LDL-P were superior to the cholesterol markers. Two approaches to resolve these differences are brought to bear in this article: first, which results are credible and second, how does taking the known differences in LDL composition into account, help resolve them. The best identification of individuals at risk of coronary artery disease or with coronary artery disease allows the most efficacious treatment of elevated LDL-P and will permit a more extensive use of some of the more novel LDL-lowering agents. SUMMARY Much of the controversy vanishes once the physiologically driven differences in the composition of the apoB lipoprotein particles are taken into account, illustrating that epidemiology, not directed by physiology, is like shooting without aiming.
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Affiliation(s)
- Allan Sniderman
- Division of Cardiology, McGill University Health Centre, Montreal, Quebec, Canada
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Tveten K, Str M TB, Berge KE, Leren TP. PCSK9-mediated degradation of the LDL receptor generates a 17 kDa C-terminal LDL receptor fragment. J Lipid Res 2013; 54:1560-1566. [PMID: 23509406 DOI: 10.1194/jlr.m034371] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the LDL receptor (LDLR) at the cell surface and reroutes the internalized LDLR to intracellular degradation. In this study, we have shown that PCSK9-mediated degradation of the full-length 160 kDa LDLR generates a 17 kDa C-terminal LDLR fragment. This fragment was not generated from mutant LDLRs resistant to PCSK9-mediated degradation or when degradation was prevented by chemicals such as ammonium chloride or the cysteine cathepsin inhibitor E64d. The observation that the 17 kDa fragment was only detected when the cells were cultured in the presence of the γ-secretase inhibitor DAPT indicates that this 17 kDa fragment undergoes γ-secretase cleavage within the transmembrane domain. The failure to detect the complementary 143 kDa ectodomain fragment is likely to be due to its rapid degradation in the endosomal lumen. The 17 kDa C-terminal LDLR fragment was also generated from a Class 5 mutant LDLR undergoing intracellular degradation. Thus, one may speculate that an LDLR with bound PCSK9 and a Class 5 LDLR with bound LDL are degraded by a similar mechanism that could involve ectodomain cleavage in the endosome.
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Affiliation(s)
- Kristian Tveten
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Thea Bismo Str M
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Knut Erik Berge
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Trond P Leren
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway.
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78
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DeVay RM, Shelton DL, Liang H. Characterization of proprotein convertase subtilisin/kexin type 9 (PCSK9) trafficking reveals a novel lysosomal targeting mechanism via amyloid precursor-like protein 2 (APLP2). J Biol Chem 2013; 288:10805-18. [PMID: 23430252 PMCID: PMC3624461 DOI: 10.1074/jbc.m113.453373] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates low density lipoprotein receptor protein levels by diverting it to lysosomes. Monoclonal antibody therapeutics aimed to neutralize PCSK9 have been shown to successfully lower serum LDL levels; however, we previously found that such therapeutic antibodies are subject to PCSK9-mediated clearance. In this study, we discovered that PCSK9 interacts via its C-terminal domain directly and in a pH-dependent manner with amyloid precursor protein as well as its closely related family member, amyloid precursor protein-like protein 2. Furthermore, we determined that amyloid precursor protein-like protein-2, but not amyloid precursor protein, is involved in mediating postendocytic delivery of PCSK9 to lysosomes and is therefore important for PCSK9 function. Based on our data, we propose a model for a lysosomal transport complex by which a soluble protein can target another protein for degradation from the luminal side of the membrane by bridging it to a lysosomally targeted transmembrane protein.
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Affiliation(s)
- Rachel M DeVay
- Rinat-Pfizer Inc., South San Francisco, California 94080, USA
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79
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IDOL stimulates clathrin-independent endocytosis and multivesicular body-mediated lysosomal degradation of the low-density lipoprotein receptor. Mol Cell Biol 2013; 33:1503-14. [PMID: 23382078 DOI: 10.1128/mcb.01716-12] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The low-density lipoprotein receptor (LDLR) is a critical determinant of plasma cholesterol levels that internalizes lipoprotein cargo via clathrin-mediated endocytosis. Here, we show that the E3 ubiquitin ligase IDOL stimulates a previously unrecognized, clathrin-independent pathway for LDLR internalization. Real-time single-particle tracking and electron microscopy reveal that IDOL is recruited to the plasma membrane by LDLR, promotes LDLR internalization in the absence of clathrin or caveolae, and facilitates LDLR degradation by shuttling it into the multivesicular body (MVB) protein-sorting pathway. The IDOL-dependent degradation pathway is distinct from that mediated by PCSK9 as only IDOL employs ESCRT (endosomal-sorting complex required for transport) complexes to recognize and traffic LDLR to lysosomes. Small interfering RNA (siRNA)-mediated knockdown of ESCRT-0 (HGS) or ESCRT-I (TSG101) components prevents IDOL-mediated LDLR degradation. We further show that USP8 acts downstream of IDOL to deubiquitinate LDLR and that USP8 is required for LDLR entry into the MVB pathway. These results provide key mechanistic insights into an evolutionarily conserved pathway for the control of lipoprotein receptor expression and cellular lipid uptake.
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