LIPA Variants in Genome-Wide Association Studies of Coronary Artery Diseases
2017; Lippincott Williams & Wilkins; Volume: 37; Issue: 6 Linguagem: Inglês
10.1161/atvbaha.117.309344
ISSN1524-4636
AutoresHanrui Zhang, Muredach P. Reilly,
Tópico(s)Cholesterol and Lipid Metabolism
ResumoHomeArteriosclerosis, Thrombosis, and Vascular BiologyVol. 37, No. 6LIPA Variants in Genome-Wide Association Studies of Coronary Artery Diseases Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBLIPA Variants in Genome-Wide Association Studies of Coronary Artery DiseasesLoss-of-Function or Gain-of-Function? Hanrui Zhang and Muredach P. Reilly Hanrui ZhangHanrui Zhang From the Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York (H.Z., M.P.R.); and Irving Institute for Clinical and Translational Research, Columbia University, New York (M.P.R.). and Muredach P. ReillyMuredach P. Reilly From the Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York (H.Z., M.P.R.); and Irving Institute for Clinical and Translational Research, Columbia University, New York (M.P.R.). Originally published1 Jun 2017https://doi.org/10.1161/ATVBAHA.117.309344Arteriosclerosis, Thrombosis, and Vascular Biology. 2017;37:1015–1017AbstractDownload figureDownload PowerPointGenome-wide association studies (GWASs) have identified multiple coronary artery disease (CAD) risk loci,1 yet moving from association to mechanistic insights and therapeutic translation remains a major challenge.2 Several GWASs have identified LIPA as a novel locus for CAD.3–5LIPA encodes lysosomal acid lipase (LAL), the major lysosomal enzyme hydrolyzing cholesteryl esters (CEs) and triglycerides derived from lipoproteins taken up by cells.6 Before its GWAS discovery for CAD, loss-of-function (LOF) mutations in LIPA were identified as the cause of rare Mendelian disorders, including Wolman disease, an infantile-onset disorder due to complete LOF mutations, as well as cholesteryl ester storage disease (CESD), a later-onset disorder with residual LAL activity resulting in hepatosplenomegaly, hyperlipidemia, liver failure, and premature atherosclerosis.7,8 Although rare LIPA LOF alleles in CESD are linked to accelerated atherosclerosis and hyperlipidemia, surprisingly the common LIPA CAD risk alleles are not associated with altered plasma lipids,9 liver traits,9 or reduced expression of LIPA in liver.10 Indeed, the CAD risk alleles have no expression quantitative trait locus (eQTL) in liver tissue10 yet do, however, have eQTLs for higherLIPA mRNA in monocytes3,11 and macrophages.12See accompanying article on page 1050These paradoxical data raise important questions for the field, particularly as LAL enzyme replacement therapy is approved for clinical use in Wolman disease and CESD, but whether this will ameliorate premature atherosclerosis and affect cardiovascular outcomes remains to be determined.13,14 First, what is the directionality of CAD causal variant(s) at the LIPA GWAS locus—are they LOF as might be anticipated based on the effects of rare Mendelian variants that cause CESD and atherosclerosis, or are these unexpectedly gain of function variants that increase LIPA expression and function in monocytes/macrophages, as suggested by the eQTL studies? If gain-of-function or LOF variants in monocytes/macrophages contribute to CAD in the general population, what is the underlying biological mechanism? Second, is the CAD-associated actions of the LIPA GWAS locus cell specific, restricted to actions in monocytes/macrophages and not active in hepatocytes, as one might surmise based on cell-specific eQTL data? Third, what is the genetic mechanism of the CAD locus in the disease-relevant cells—and is there one or many functional variants that contribute to the GWAS CAD signal?In this issue, Morris et al15 have begun to tackle these intriguing questions in their study of the potential causal variant for CAD at the GWAS LIPA locus and the directionality of its actions (Figure). They report that rs1051338 (NM_000235.3: c.46A>C, p.Thr16Pro), a coding variant in high linkage disequilibrium with the GWAS lead single-nucleotide polymorphisms (SNPs), may serve as the potential causal variant at the LIPA locus for CAD. By using in silico prediction, overexpression of LAL in COS7 cell lines, and comparing LAL expression and activity in primary macrophages from risk allele and nonrisk allele carriers, the authors propose that the risk allele (C) at rs1051338, which encodes a nonsynonymous threonine to proline change (Thr16Pro) within the signal peptide of LAL, may impair LAL protein translocation from the endoplasmic reticulum resulting in proteosomal degradation and reduced LAL protein and activity in macrophages. The results also showed that lysosomal LAL activity in the risk allele carriers was lower than that in the nonrisk allele carriers and that this was associated with a trend toward reduced efflux after [3H]-cholesterol–labeled acetylated low-density lipoprotein loading. Thus, they propose that the GWAS risk locus for CAD is indeed LOF and mediated by the rs1051338 LIPA variant.Download figureDownload PowerPointFigure. The LIPA paradox. Genome-wide association studies (GWAS) have identified LIPA as a novel locus for coronary artery disease (CAD). Rare loss-of-function (LOF) mutations of LIPA result in Wolman disease and cholesteryl ester storage disease with hepatomegaly, hyperlipidemia, and premature atherosclerosis. Surprisingly, the common LIPA CAD–GWAS risk alleles do not associate with altered plasma lipids or hepatic LIPA mRNA levels but relate to higher LIPA mRNA in monocytes and macrophages. The study by Morris et al15 suggests that rs1051338, a coding variant in high linkage disequilibrium with the GWAS lead single-nucleotide polymorphisms, causing a threonine to proline missense mutation within the signal peptide of lysosomal acid lipase (LAL), leads to increased degradation and, therefore, reduced LAL activity. However, the directionality of LIPA CAD variants—whether LOF as suggested by Morris et al15 and based on the rare Mendelian variants or unexpected gain of function in monocytes/macrophages as suggested by expression quantitative trait loci (eQTL) analysis warrants further studies. The causal variant(s) and the functional impact and mechanisms of the variants on macrophage phenotypes remain to be fully defined.Although these data are highly suggestive, they are not yet definitive for rs1051338 being "the" causal variant at the LIPA GWAS locus. The effects of the variant on LAL protein degradation were determined by exogenous LAL overexpression in COS7 cell line, a line that is not a disease-relevant cell type and the results mainly relied on the use of pharmacological inhibitors. Some experiments were repeated using human monocyte–derived macrophages but only in 4 homozygous risk allele and nonrisk allele carriers, which is a small sample size for detection of the modest effects expected of a common variant for a complex trait identified by GWAS. Indeed, this is revealed by the lack of difference in LIPA expression in the monocytes3,11 and macrophages12 in the presented data despite the published eQTL for rs1051338 and other linked GWAS lead SNPs at the locus. Furthermore, the functional impact of the variant examined in this study focused only on the efflux capacity of [3H]-cholesterol–labeled acetylated low-density lipoprotein and failed to show a statistically significant difference by allele groups. Other phenotypes relevant to the LOF of LIPA, such as lysosomal CE hydrolysis,16 autophagy,17 and macrophage alternative activation18 were not studied.In addition to rs1051338, there are other linked SNPs at the LIPA locus, including those of similar allele frequency yet showing stronger association with increased risk of CAD and also with higher mRNA expression in eQTLs.3,11 Some of these SNPs overlie open chromatin marks and other epigenetic features suggesting regulatory actions that might increase LIPA expression and contribute to CAD. This study does not exclude this alternative hypothesis, one that is supported indirectly by data showing that increasing free cholesterol levels in lysosomes inhibit lysosome acidification and function and subsequent hydrolysis of lipoprotein CE,19,20 and that extracellular lysosomal synapse can degrade aggregated low-density lipoprotein and contribute to foam cell formation.21–23 The functional effects, or lack thereof, of the linked SNPs in the region on LIPA transcription and mRNA expression in both monocytes and macrophages remain to be studied. This is particularly important, as this study did not address the published and surprising eQTL data of higher LIPA mRNA levels if the rs1051338 coding variant is indeed causal for CAD and encodes LOF of LAL activity.Studying cell lines with endogenous LIPA expression on an isogenic background when the only genetic difference is each individual SNP will provide more reliable data than studying endogenous cells where the effects of individual variants in high linkage disequilibrium at the locus cannot be separated—as is the case for the current studies by Morris et al.15 Gene editing of human-induced pluripotent stem cells to introduce separately each risk allele or to correct each risk allele, ideally differentiating the human-induced pluripotent stem cell lines to macrophages for functional studies,24 is ultimately required to provide definitive data in support of causal effects of any individual or combination of SNP variants.In summary, Morris et al15 present important data suggesting that the rs1051338 Thr16Pro variant, in the LAL signal peptide, may be a causal LOF variant at the LIPA GWAS locus. Yet these studies do not address fully the LIPA paradox. Ultimately, gene editing25 of isogenic human-induced pluripotent stem cell with differentiation to macrophages (and other LIPA and CAD-relevant cells) coupled to study the primary macrophages of much larger numbers of risk and nonrisk allele carriers is warranted to parse the individual effects of each of the linked variants at the LIPA GWAS locus. Targeted mouse models with knockin of human LIPA CAD alleles will also help to reveal the in vivo effects of specific variants at this GWAS locus on atherosclerosis. Further mechanistic study of macrophage LIPA in CAD risk will shed light on the potential for benefit and risk in therapeutic targeting of LIPA in CAD, particularly in the context of the availability of LAL replacement therapy currently approved for use in patients with CESD.Sources of FundingThis work is supported by National Institutes of Health (NIH) grants R01-HL-113147 and K24-HL-107643 (to M.P. Reilly), and partially supported by American Heart Association Postdoctoral Fellowship 15POST25620017 and NIH grant K99-HL-130574 (to H. Zhang). M.P. Reilly is also supported by R01-HL-111694.DisclosuresNone.FootnotesCorrespondence to Muredach P. Reilly, MB BCh, MSCE, Irving Institute for Clinical and Translational Research, Columbia University Medical Center, 622 W 168th St, PH10-305, New York, NY 10032. E-mail [email protected]References1. Khera AV, Kathiresan S. Genetics of coronary artery disease: discovery, biology and clinical translation [published online ahead of print March 13, 2017].Nat Rev Genet. doi: 10.1038/nrg.2016.160. https://www.nature.com/nrg/journal/vaop/ncurrent/full/nrg.2016.160.html.Google Scholar2. Nurnberg ST, Zhang H, Hand NJ, Bauer RC, Saleheen D, Reilly MP, Rader DJ. From loci to biology: functional genomics of genome-wide association for coronary disease.Circ Res. 2016; 118:586–606. doi: 10.1161/CIRCRESAHA.115.306464.LinkGoogle Scholar3. Wild PS, Zeller T, Schillert A, et al. A genome-wide association study identifies LIPA as a susceptibility gene for coronary artery disease.Circ Cardiovasc Genet. 2011; 4:403–412. doi: 10.1161/CIRCGENETICS.110.958728.LinkGoogle Scholar4. Deloukas P, Kanoni S, Willenborg C, et al; CARDIoGRAMplusC4D Consortium; DIAGRAM Consortium; CARDIOGENICS Consortium; MuTHER Consortium; Wellcome Trust Case Control Consortium. Large-scale association analysis identifies new risk loci for coronary artery disease.Nat Genet. 2013; 45:25–33. doi: 10.1038/ng.2480.CrossrefMedlineGoogle Scholar5. Coronary Artery Disease Genetics C. A genome-wide association study in europeans and south asians identifies five new loci for coronary artery disease.Nature Genet. 2011; 43:339–344.CrossrefMedlineGoogle Scholar6. Dubland JA, Francis GA. Lysosomal acid lipase: at the crossroads of normal and atherogenic cholesterol metabolism.Front Cell Dev Biol. 2015; 3:3. doi: 10.3389/fcell.2015.00003.CrossrefMedlineGoogle Scholar7. Bernstein DL, Hülkova H, Bialer MG, Desnick RJ. Cholesteryl ester storage disease: review of the findings in 135 reported patients with an underdiagnosed disease.J Hepatol. 2013; 58:1230–1243. doi: 10.1016/j.jhep.2013.02.014.CrossrefMedlineGoogle Scholar8. Du H, Schiavi S, Levine M, Mishra J, Heur M, Grabowski GA. Enzyme therapy for lysosomal acid lipase deficiency in the mouse.Hum Mol Genet. 2001; 10:1639–1648.CrossrefMedlineGoogle Scholar9. Willer CJ, Schmidt EM, Sengupta S, et al; Global Lipids Genetics Consortium. Discovery and refinement of loci associated with lipid levels.Nat Genet. 2013; 45:1274–1283. doi: 10.1038/ng.2797.CrossrefMedlineGoogle Scholar10. HumanGenomics. The genotype-tissue expression (gtex) pilot analysis: multitissue gene regulation in humans.Science. 2015; 348:648–660.CrossrefMedlineGoogle Scholar11. The IBC 50K CAD Consortium. Large-scale gene-centric analysis identifies novel variants for coronary artery disease.PLoS Genet. 2011; 7:e1002260.CrossrefMedlineGoogle Scholar12. Nédélec Y, Sanz J, Baharian G, et al. Genetic Ancestry and Natural Selection Drive Population Differences in Immune Responses to Pathogens.Cell. 2016; 167:657.e21–669.e21. doi: 10.1016/j.cell.2016.09.025.CrossrefGoogle Scholar13. Burton BK, Balwani M, Feillet F, et al. A Phase 3 Trial of sebelipase alfa in lysosomal acid lipase deficiency.N Engl J Med. 2015; 373:1010–1020. doi: 10.1056/NEJMoa1501365.CrossrefMedlineGoogle Scholar14. Jones SA, Rojas-Caro S, Quinn AG, et al. Survival in infants treated with sebelipase Alfa for lysosomal acid lipase deficiency: an open-label, multicenter, dose-escalation study.Orphanet J Rare Dis. 2017; 12:25. doi: 10.1186/s13023-017-0587-3.CrossrefMedlineGoogle Scholar15. Morris GE, Braund PS, Moore JS, Samani NJ, Codd V, Webb TR. Coronary artery disease–associated LIPA coding variant rs1051338 reduces lysosomal acid lipase levels and activity in lysosomes.Arterioscler Thromb Vasc Biol. 2017; 37:1050–1057. doi: 10.1161/ATVBAHA.116.308734.LinkGoogle Scholar16. Goldstein JL, Dana SE, Faust JR, Beaudet AL, Brown MS. Role of lysosomal acid lipase in the metabolism of plasma low density lipoprotein. Observations in cultured fibroblasts from a patient with cholesteryl ester storage disease.J Biol Chem. 1975; 250:8487–8495.CrossrefMedlineGoogle Scholar17. Ouimet M, Franklin V, Mak E, Liao X, Tabas I, Marcel YL. Autophagy regulates cholesterol efflux from macrophage foam cells via lysosomal acid lipase.Cell Metab. 2011; 13:655–667. doi: 10.1016/j.cmet.2011.03.023.CrossrefMedlineGoogle Scholar18. Huang SC, Everts B, Ivanova Y, et al. Cell-intrinsic lysosomal lipolysis is essential for alternative activation of macrophages.Nat Immunol. 2014; 15:846–855. doi: 10.1038/ni.2956.CrossrefMedlineGoogle Scholar19. Cox BE, Griffin EE, Ullery JC, Jerome WG. Effects of cellular cholesterol loading on macrophage foam cell lysosome acidification.J Lipid Res. 2007; 48:1012–1021. doi: 10.1194/jlr.M600390-JLR200.CrossrefMedlineGoogle Scholar20. Jerome WG, Cox BE, Griffin EE, Ullery JC. Lysosomal cholesterol accumulation inhibits subsequent hydrolysis of lipoprotein cholesteryl ester.Microsc Microanal. 2008; 14:138–149. doi: 10.1017/S1431927608080069.CrossrefMedlineGoogle Scholar21. Singh RK, Barbosa-Lorenzi VC, Lund FW, Grosheva I, Maxfield FR, Haka AS. Degradation of aggregated LDL occurs in complex extracellular sub-compartments of the lysosomal synapse.J Cell Sci. 2016; 129:1072–1082. doi: 10.1242/jcs.181743.CrossrefMedlineGoogle Scholar22. Haka AS, Singh RK, Grosheva I, Hoffner H, Capetillo-Zarate E, Chin HF, Anandasabapathy N, Maxfield FR. Monocyte-derived dendritic cells upregulate extracellular catabolism of aggregated low-density lipoprotein on maturation, leading to foam cell formation.Arterioscler Thromb Vasc Biol. 2015; 35:2092–2103. doi: 10.1161/ATVBAHA.115.305843.LinkGoogle Scholar23. Haka AS, Grosheva I, Chiang E, Buxbaum AR, Baird BA, Pierini LM, Maxfield FR. Macrophages create an acidic extracellular hydrolytic compartment to digest aggregated lipoproteins.Mol Biol Cell. 2009; 20:4932–4940. doi: 10.1091/mbc.E09-07-0559.CrossrefMedlineGoogle Scholar24. Zhang H, Xue C, Shah R, et al. Functional analysis and transcriptomic profiling of iPSC-derived macrophages and their application in modeling Mendelian disease.Circ Res. 2015; 117:17–28. doi: 10.1161/CIRCRESAHA.117.305860.LinkGoogle Scholar25. Musunuru K. Genome editing of human pluripotent stem cells to generate human cellular disease models.Dis Model Mech. 2013; 6:896–904. doi: 10.1242/dmm.012054.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsCited By Besler K, Blanchard V and Francis G (2022) Lysosomal acid lipase deficiency: A rare inherited dyslipidemia but potential ubiquitous factor in the development of atherosclerosis and fatty liver disease, Frontiers in Genetics, 10.3389/fgene.2022.1013266, 13 Evans T, Zhang X, Clark R, Alisio A, Song E, Zhang H, Reilly M, Stitziel N and Razani B (2019) Functional Characterization of LIPA (Lysosomal Acid Lipase) Variants Associated With Coronary Artery Disease, Arteriosclerosis, Thrombosis, and Vascular Biology, 39:12, (2480-2491), Online publication date: 1-Dec-2019.Li F, Shi J, Lu H and Zhang H (2019) Functional Genomics and CRISPR Applied to Cardiovascular Research and Medicine, Arteriosclerosis, Thrombosis, and Vascular Biology, 39:9, (e188-e194), Online publication date: 1-Sep-2019. Yvan-Charvet L, Bonacina F, Guinamard R and Norata G (2019) Immunometabolic function of cholesterol in cardiovascular disease and beyond, Cardiovascular Research, 10.1093/cvr/cvz127, 115:9, (1393-1407), Online publication date: 15-Jul-2019. Çalışkan M, Manduchi E, Rao H, Segert J, Beltrame M, Trizzino M, Park Y, Baker S, Chesi A, Johnson M, Hodge K, Leonard M, Loza B, Xin D, Berrido A, Hand N, Bauer R, Wells A, Olthoff K, Shaked A, Rader D, Grant S and Brown C (2019) Genetic and Epigenetic Fine Mapping of Complex Trait Associated Loci in the Human Liver, The American Journal of Human Genetics, 10.1016/j.ajhg.2019.05.010, 105:1, (89-107), Online publication date: 1-Jul-2019. Ouimet M, Barrett T and Fisher E (2019) HDL and Reverse Cholesterol Transport, Circulation Research, 124:10, (1505-1518), Online publication date: 10-May-2019.Li F and Zhang H (2019) Lysosomal Acid Lipase in Lipid Metabolism and Beyond, Arteriosclerosis, Thrombosis, and Vascular Biology, 39:5, (850-856), Online publication date: 1-May-2019. Li Y, Li L, Bi L, Xu X, Cheng W, Yu B and Zhang Y (2018) Lipid-associated genetic polymorphisms are associated with FBP and LDL-c levels among myocardial infarction patients in Chinese population, Gene, 10.1016/j.gene.2018.07.016, 676, (22-28), Online publication date: 1-Nov-2018. Zhang H (2018) Lysosomal acid lipase and lipid metabolism, Current Opinion in Lipidology, 10.1097/MOL.0000000000000507, 29:3, (218-223), Online publication date: 1-Jun-2018. Thiriet M (2018) Hyperlipidemias and Obesity Vasculopathies, 10.1007/978-3-319-89315-0_5, (331-548), . June 2017Vol 37, Issue 6 Advertisement Article InformationMetrics © 2017 American Heart Association, Inc.https://doi.org/10.1161/ATVBAHA.117.309344PMID: 28539489 Originally publishedJune 1, 2017 KeywordsatherosclerosisEditorialsmacrophagegeneticscoronary artery diseasecholesteryl estersPDF download Advertisement
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