1
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Zhang L, Shi Y, Liang B, Li X. An overview of the cholesterol metabolism and its proinflammatory role in the development of MASLD. Hepatol Commun 2024; 8:e0434. [PMID: 38696365 PMCID: PMC11068152 DOI: 10.1097/hc9.0000000000000434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 03/05/2024] [Indexed: 05/04/2024] Open
Abstract
Cholesterol is an essential lipid molecule in mammalian cells. It is not only involved in the formation of cell membranes but also serves as a raw material for the synthesis of bile acids, vitamin D, and steroid hormones. Additionally, it acts as a covalent modifier of proteins and plays a crucial role in numerous life processes. Generally, the metabolic processes of cholesterol absorption, synthesis, conversion, and efflux are strictly regulated. Excessive accumulation of cholesterol in the body is a risk factor for metabolic diseases such as cardiovascular disease, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). In this review, we first provide an overview of the discovery of cholesterol and the fundamental process of cholesterol metabolism. We then summarize the relationship between dietary cholesterol intake and the risk of developing MASLD, and also the animal models of MASLD specifically established with a cholesterol-containing diet. In the end, the role of cholesterol-induced inflammation in the initiation and development of MASLD is discussed.
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Affiliation(s)
- Linqiang Zhang
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing, China
| | - Yongqiong Shi
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing, China
| | - Bin Liang
- Center for Life Sciences, Yunnan Key Laboratory of Cell Metabolism and Diseases, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
| | - Xi Li
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing, China
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2
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Aamer W, Al-Maraghi A, Syed N, Gandhi GD, Aliyev E, Al-Kurbi AA, Al-Saei O, Kohailan M, Krishnamoorthy N, Palaniswamy S, Al-Malki K, Abbasi S, Agrebi N, Abbaszadeh F, Akil ASAS, Badii R, Ben-Omran T, Lo B, Mokrab Y, Fakhro KA. Burden of Mendelian disorders in a large Middle Eastern biobank. Genome Med 2024; 16:46. [PMID: 38584274 PMCID: PMC11000384 DOI: 10.1186/s13073-024-01307-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 02/19/2024] [Indexed: 04/09/2024] Open
Abstract
BACKGROUND Genome sequencing of large biobanks from under-represented ancestries provides a valuable resource for the interrogation of Mendelian disease burden at world population level, complementing small-scale familial studies. METHODS Here, we interrogate 6045 whole genomes from Qatar-a Middle Eastern population with high consanguinity and understudied mutational burden-enrolled at the national Biobank and phenotyped for 58 clinically-relevant quantitative traits. We examine a curated set of 2648 Mendelian genes from 20 panels, annotating known and novel pathogenic variants and assessing their penetrance and impact on the measured traits. RESULTS We find that 62.5% of participants are carriers of at least 1 known pathogenic variant relating to recessive conditions, with homozygosity observed in 1 in 150 subjects (0.6%) for which Peninsular Arabs are particularly enriched versus other ancestries (5.8-fold). On average, 52.3 loss-of-function variants were found per genome, 6.5 of which affect a known Mendelian gene. Several variants annotated in ClinVar/HGMD as pathogenic appeared at intermediate frequencies in this cohort (1-3%), highlighting Arab founder effect, while others have exceedingly high frequencies (> 5%) prompting reconsideration as benign. Furthermore, cumulative gene burden analysis revealed 56 genes having gene carrier frequency > 1/50, including 5 ACMG Tier 3 panel genes which would be candidates for adding to newborn screening in the country. Additionally, leveraging 58 biobank traits, we systematically assess the impact of novel/rare variants on phenotypes and discover 39 candidate large-effect variants associating with extreme quantitative traits. Furthermore, through rare variant burden testing, we discover 13 genes with high mutational load, including 5 with impact on traits relevant to disease conditions, including metabolic disorder and type 2 diabetes, consistent with the high prevalence of these conditions in the region. CONCLUSIONS This study on the first phase of the growing Qatar Genome Program cohort provides a comprehensive resource from a Middle Eastern population to understand the global mutational burden in Mendelian genes and their impact on traits in seemingly healthy individuals in high consanguinity settings.
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Affiliation(s)
- Waleed Aamer
- Department of Human Genetics, Sidra Medicine, Doha, Qatar
| | | | - Najeeb Syed
- Applied Bioinformatics Core, Sidra Medicine, Doha, Qatar
| | | | - Elbay Aliyev
- Department of Human Genetics, Sidra Medicine, Doha, Qatar
| | | | - Omayma Al-Saei
- Department of Human Genetics, Sidra Medicine, Doha, Qatar
| | | | | | | | | | - Saleha Abbasi
- Department of Human Genetics, Sidra Medicine, Doha, Qatar
| | - Nourhen Agrebi
- Department of Human Genetics, Sidra Medicine, Doha, Qatar
| | | | | | - Ramin Badii
- Diagnostic Genomic Division, Hamad Medical Corporation, Doha, Qatar
| | - Tawfeg Ben-Omran
- Section of Clinical and Metabolic Genetics, Department of pediatrics, Hamad Medical Corporation, Doha, Qatar
- Department of Pediatric, Weill Cornell Medical College, Doha, Qatar
- Division of Genetic & Genomics Medicine, Sidra Medicine, Doha, Qatar
| | - Bernice Lo
- Department of Human Genetics, Sidra Medicine, Doha, Qatar
- College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
| | - Younes Mokrab
- Department of Human Genetics, Sidra Medicine, Doha, Qatar.
- Department of Genetic Medicine, Weill Cornell Medicine-Qatar, Doha, Qatar.
- College of Health Sciences, Qatar University, Doha, Qatar.
| | - Khalid A Fakhro
- Department of Human Genetics, Sidra Medicine, Doha, Qatar.
- College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar.
- Department of Genetic Medicine, Weill Cornell Medicine-Qatar, Doha, Qatar.
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3
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Ashby G, Keng KE, Hayden CC, Gollapudi S, Houser JR, Jamal S, Stachowiak JC. Selective Endocytic Uptake of Targeted Liposomes Occurs within a Narrow Range of Liposome Diameters. ACS APPLIED MATERIALS & INTERFACES 2023; 15:49988-50001. [PMID: 37862704 DOI: 10.1021/acsami.3c09399] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2023]
Abstract
Cell surface receptors facilitate signaling and nutrient uptake. These processes are dynamic, requiring receptors to be actively recycled by endocytosis. Due to their differential expression in disease states, receptors are often the target of drug-carrier particles, which are adorned with ligands that bind specifically to receptors. These targeted particles are taken into the cell by multiple routes of internalization, where the best-characterized pathway is clathrin-mediated endocytosis. Most studies of particle uptake have utilized bulk assays rather than observing individual endocytic events. As a result, the detailed mechanisms of particle uptake remain obscure. To address this gap, we employed a live-cell imaging approach to study the uptake of individual liposomes as they interact with clathrin-coated structures. By tracking individual internalization events, we find that the size of liposomes rather than the density of the ligands on their surfaces primarily determines their probability of uptake. Interestingly, targeting has the greatest impact on endocytosis of liposomes of intermediate diameters, with the smallest and largest liposomes being internalized or excluded, respectively, regardless of whether they are targeted. These findings, which highlight a previously unexplored limitation of targeted delivery, can be used to design more effective drug carriers.
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Affiliation(s)
- Grant Ashby
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Kayla E Keng
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Carl C Hayden
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sadhana Gollapudi
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Justin R Houser
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sabah Jamal
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
- Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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4
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Ho TWW, Henry A, Lee WL. LDL Transcytosis by the Arterial Endothelium-Atherosclerosis by a Thousand Cuts? Curr Atheroscler Rep 2023; 25:457-465. [PMID: 37358804 DOI: 10.1007/s11883-023-01118-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2023] [Indexed: 06/27/2023]
Abstract
PURPOSE OF REVIEW The accumulation of LDL in the arterial intima is an initiating event in atherosclerosis. After decades of controversy, it is now clear that transcytosis of LDL across an intact endothelial monolayer contributes to its intimal deposition. We review recent observations in this field and address the question of whether LDL transcytosis can be manipulated therapeutically. RECENT FINDINGS The development of a live-cell imaging method for studying transcytosis using total internal reflection fluorescence (TIRF) microscopy has catalyzed recent discoveries. LDL transcytosis is mediated by SR-BI and ALK1. Estrogen down-regulates SR-BI and inhibits LDL transcytosis, while the nuclear structural protein HMGB1 promotes LDL transcytosis. LDL transcytosis by ALK1 is independent of the receptor's kinase activity and is antagonized by BMP9, ALK1's canonical ligand. Inflammation stimulates LDL transcytosis. Identifying the function and mechanisms of LDL transcytosis may ultimately permit its therapeutic manipulation.
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Affiliation(s)
- Tse Wing Winnie Ho
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, Toronto, Canada
| | - Andria Henry
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, Toronto, Canada
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Warren L Lee
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, Toronto, Canada.
- Department of Biochemistry, University of Toronto, Toronto, Canada.
- Department of Medicine and the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.
- St. Michael's Hospital, Unity Health Toronto, 30 Bond Street, Toronto, ON, M5B 1W8, Canada.
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5
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Ashby G, Keng KE, Hayden CC, Gollapudi S, Houser JR, Jamal S, Stachowiak JC. Selective endocytic uptake of targeted liposomes occurs within a narrow range of liposome diameter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.06.548000. [PMID: 37461728 PMCID: PMC10350051 DOI: 10.1101/2023.07.06.548000] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/27/2023]
Abstract
Cell surface receptors facilitate signaling and nutrient uptake. These processes are dynamic, requiring receptors to be actively recycled by endocytosis. Due to their differential expression in disease states, receptors are often the target of drug-carrier particles, which are adorned with ligands that bind specifically to receptors. These targeted particles are taken into the cell by multiple routes of internalization, where the best-characterized pathway is clathrin-mediated endocytosis. Most studies of particle uptake have utilized bulk assays, rather than observing individual endocytic events. As a result, the detailed mechanisms of particle uptake remain obscure. To address this gap, we have employed a live-cell imaging approach to study the uptake of individual liposomes as they interact with clathrin-coated structures. By tracking individual internalization events, we find that the size of liposomes, rather than the density of the ligands on their surfaces, primarily determines their probability of uptake. Interestingly, targeting has the greatest impact on endocytosis of liposomes of intermediate diameters, with the smallest and largest liposomes being internalized or excluded, respectively, regardless of whether they are targeted. These findings, which highlight a previously unexplored limitation of targeted delivery, can be used to design more effective drug carriers.
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Affiliation(s)
- Grant Ashby
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Kayla E Keng
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Carl C Hayden
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Sadhana Gollapudi
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Justin R Houser
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Sabah Jamal
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin
- Department of Chemical Engineering, The University of Texas at Austin
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6
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Puddu A, Montecucco F, Maggi D. Caveolin-1 and Atherosclerosis: Regulation of LDLs Fate in Endothelial Cells. Int J Mol Sci 2023; 24:ijms24108869. [PMID: 37240214 DOI: 10.3390/ijms24108869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 04/28/2023] [Accepted: 05/15/2023] [Indexed: 05/28/2023] Open
Abstract
Caveolae are 50-100 nm cell surface plasma membrane invaginations observed in terminally differentiated cells. They are characterized by the presence of the protein marker caveolin-1. Caveolae and caveolin-1 are involved in regulating several signal transduction pathways and processes. It is well recognized that they have a central role as regulators of atherosclerosis. Caveolin-1 and caveolae are present in most of the cells involved in the development of atherosclerosis, including endothelial cells, macrophages, and smooth muscle cells, with evidence of either pro- or anti-atherogenic functions depending on the cell type examined. Here, we focused on the role of caveolin-1 in the regulation of the LDLs' fate in endothelial cells.
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Affiliation(s)
- Alessandra Puddu
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 6, 16132 Genoa, Italy
| | - Fabrizio Montecucco
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 6, 16132 Genoa, Italy
- IRCCS Ospedale Policlinico San Martino Genoa, Italian Cardiovascular Network, Largo Rosanna Benzi 10, 16132 Genoa, Italy
| | - Davide Maggi
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 6, 16132 Genoa, Italy
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7
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Liu JT, Doueiry C, Jiang YL, Blaszkiewicz J, Lamprecht MP, Heslop JA, Peterson YK, Carten JD, Traktman P, Yuan Y, Khetani SR, Twal WO, Duncan SA. A human iPSC-derived hepatocyte screen identifies compounds that inhibit production of Apolipoprotein B. Commun Biol 2023; 6:452. [PMID: 37095219 PMCID: PMC10125972 DOI: 10.1038/s42003-023-04739-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 03/21/2023] [Indexed: 04/26/2023] Open
Abstract
Familial hypercholesterolemia (FH) patients suffer from excessively high levels of Low Density Lipoprotein Cholesterol (LDL-C), which can cause severe cardiovascular disease. Statins, bile acid sequestrants, PCSK9 inhibitors, and cholesterol absorption inhibitors are all inefficient at treating FH patients with homozygous LDLR gene mutations (hoFH). Drugs approved for hoFH treatment control lipoprotein production by regulating steady-state Apolipoprotein B (apoB) levels. Unfortunately, these drugs have side effects including accumulation of liver triglycerides, hepatic steatosis, and elevated liver enzyme levels. To identify safer compounds, we used an iPSC-derived hepatocyte platform to screen a structurally representative set of 10,000 small molecules from a proprietary library of 130,000 compounds. The screen revealed molecules that could reduce the secretion of apoB from cultured hepatocytes and from humanized livers in mice. These small molecules are highly effective, do not cause abnormal lipid accumulation, and share a chemical structure that is distinct from any known cholesterol lowering drug.
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Affiliation(s)
- Jui-Tung Liu
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Caren Doueiry
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Yu-Lin Jiang
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Josef Blaszkiewicz
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Mary Paige Lamprecht
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - James A Heslop
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Yuri K Peterson
- Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Juliana Debrito Carten
- Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Paula Traktman
- Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Yang Yuan
- Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Salman R Khetani
- Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | | | - Stephen A Duncan
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA.
- Grùthan Biosciences LLC, Hollywood, SC, 29449, USA.
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8
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Mani I, Singh V. An overview of receptor endocytosis and signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 194:1-18. [PMID: 36631188 DOI: 10.1016/bs.pmbts.2022.06.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Endocytosis is a cellular process which mediates receptor internalization, nutrient uptake, and the regulation of cell signaling. Microorganisms (many bacteria and viruses) and toxins also use the same process and enter the cells. Generally, endocytosis is considered in the three forms such as phagocytosis (cell eating), pinocytosis (cell drinking), and highly selective receptor-mediated endocytosis (clathrin-dependent and independent). Several endocytic routes exist in an analogous, achieving diverse functions. Most studies on endocytosis have used transformed cells in culture. To visualize the receptor internalization, trafficking, and signaling in subcellular organelles, a green fluorescent protein-tagged receptor has been utilized. It also helps to visualize the endocytosis effects in live-cell imaging. Confocal laser microscopy increases our understanding of receptor endocytosis and signaling. Site-directed mutagenesis studies demonstrated that many short-sequence motifs of the cytoplasmic domain of receptors significantly play a vital role in receptor internalization, subcellular trafficking, and signaling. However, other factors also regulate receptor internalization through clathrin-coated vesicles. Receptor endocytosis can occur through clathrin-dependent and clathrin-independent pathways. This chapter briefly discusses the internalization, trafficking, and signaling of various receptors in normal conditions. In addition, it also highlights the malfunction of the receptor in disease conditions.
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Affiliation(s)
- Indra Mani
- Department of Microbiology, Gargi College, University of Delhi, New Delhi, India.
| | - Vijai Singh
- Department of Biosciences, School of Science, Indrashil University, Rajpur, Mehsana, Gujarat, India
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9
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Wang M, Alabi A, Gu HM, Gill G, Zhang Z, Jarad S, Xia XD, Shen Y, Wang GQ, Zhang DW. Identification of amino acid residues in the MT-loop of MT1-MMP critical for its ability to cleave low-density lipoprotein receptor. Front Cardiovasc Med 2022; 9:917238. [PMID: 36093157 PMCID: PMC9452735 DOI: 10.3389/fcvm.2022.917238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 08/01/2022] [Indexed: 11/13/2022] Open
Abstract
Low-density lipoprotein receptor (LDLR) mediates clearance of plasma LDL cholesterol, preventing the development of atherosclerosis. We previously demonstrated that membrane type 1-matrix metalloproteinase (MT1-MMP) cleaves LDLR and exacerbates the development of atherosclerosis. Here, we investigated determinants in LDLR and MT1-MMP that were critical for MT1-MMP-induced LDLR cleavage. We observed that deletion of various functional domains in LDLR or removal of each of the five predicted cleavage sites of MT1-MMP on LDLR did not affect MT1-MMP-induced cleavage of the receptor. Removal of the hemopexin domain or the C-terminal cytoplasmic tail of MT1-MMP also did not impair its ability to cleave LDLR. On the other hand, mutant MT1-MMP, in which the catalytic domain or the MT-loop was deleted, could not cleave LDLR. Further Ala-scanning analysis revealed an important role for Ile at position 167 of the MT-loop in MT1-MMP’s action on LDLR. Replacement of Ile167 with Ala, Thr, Glu, or Lys resulted in a marked loss of the ability to cleave LDLR, whereas mutation of Ile167 to a non-polar amino acid residue, including Leu, Val, Met, and Phe, had no effect. Therefore, our studies indicate that MT1-MMP does not require a specific cleavage site on LDLR. In contrast, an amino acid residue with a hydrophobic side chain at position 167 in the MT-loop is critical for MT1-MMP-induced LDLR cleavage.
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Affiliation(s)
- Maggie Wang
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Adekunle Alabi
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Hong-mei Gu
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Govind Gill
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Ziyang Zhang
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Suha Jarad
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Xiao-dan Xia
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Orthopedics, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People’s Hospital, Qingyuan, China
| | - Yishi Shen
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
| | - Gui-qing Wang
- Department of Orthopedics, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People’s Hospital, Qingyuan, China
| | - Da-wei Zhang
- The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada
- *Correspondence: Da-wei Zhang,
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10
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Anderson RH, Sochacki KA, Vuppula H, Scott BL, Bailey EM, Schultz MM, Kerkvliet JG, Taraska JW, Hoppe AD, Francis KR. Sterols lower energetic barriers of membrane bending and fission necessary for efficient clathrin-mediated endocytosis. Cell Rep 2021; 37:110008. [PMID: 34788623 PMCID: PMC8620193 DOI: 10.1016/j.celrep.2021.110008] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 08/03/2021] [Accepted: 10/26/2021] [Indexed: 01/16/2023] Open
Abstract
Clathrin-mediated endocytosis (CME) is critical for cellular signal transduction, receptor recycling, and membrane homeostasis in mammalian cells. Acute depletion of cholesterol disrupts CME, motivating analysis of CME dynamics in the context of human disorders of cholesterol metabolism. We report that inhibition of post-squalene cholesterol biosynthesis impairs CME. Imaging of membrane bending dynamics and the CME pit ultrastructure reveals prolonged clathrin pit lifetimes and shallow clathrin-coated structures, suggesting progressive impairment of curvature generation correlates with diminishing sterol abundance. Sterol structural requirements for efficient CME include 3′ polar head group and B-ring conformation, resembling the sterol structural prerequisites for tight lipid packing and polarity. Furthermore, Smith-Lemli-Opitz fibroblasts with low cholesterol abundance exhibit deficits in CME-mediated transferrin internalization. We conclude that sterols lower the energetic costs of membrane bending during pit formation and vesicular scission during CME and suggest that reduced CME activity may contribute to cellular phenotypes observed within disorders of cholesterol metabolism. Anderson et al. demonstrate that sterol abundance and identity play a dominant role in facilitating clathrin-mediated endocytosis. Detailed analyses of clathrin-coated pits under sterol depletion support a requirement for sterol-mediated membrane bending during multiple stages of endocytosis, implicating endocytic dysfunction within the pathogenesis of disorders of cholesterol metabolism.
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Affiliation(s)
- Ruthellen H Anderson
- Sanford School of Medicine, University of South Dakota, Sioux Falls, SD 57105, USA; Cellular Therapies and Stem Cell Biology Group, Sanford Research, Sioux Falls, SD 57104, USA
| | - Kem A Sochacki
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA
| | - Harika Vuppula
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA; BioSystems Networks and Translational Research Center, Brookings, SD 57007, USA
| | - Brandon L Scott
- Nanoscience and Nanoengineering, South Dakota School of Mines & Technology, Rapid City, SD 57701, USA
| | - Elizabeth M Bailey
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA; BioSystems Networks and Translational Research Center, Brookings, SD 57007, USA
| | - Maycie M Schultz
- Cellular Therapies and Stem Cell Biology Group, Sanford Research, Sioux Falls, SD 57104, USA
| | - Jason G Kerkvliet
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA; BioSystems Networks and Translational Research Center, Brookings, SD 57007, USA
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA
| | - Adam D Hoppe
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA; BioSystems Networks and Translational Research Center, Brookings, SD 57007, USA.
| | - Kevin R Francis
- Cellular Therapies and Stem Cell Biology Group, Sanford Research, Sioux Falls, SD 57104, USA; Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD 57105, USA.
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11
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DeGroot ACM, Gollapudi S, Zhao C, LaMonica MF, Stachowiak JC. Weakly Internalized Receptors Use Coated Vesicle Heterogeneity to Evade Competition during Endocytosis. Biochemistry 2021; 60:2195-2205. [PMID: 34170686 PMCID: PMC8483609 DOI: 10.1021/acs.biochem.1c00268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The uptake of receptors by clathrin-mediated endocytosis underlies signaling, nutrient import, and recycling of transmembrane proteins and lipids. In the complex, crowded environment of the plasma membrane, receptors are internalized when they bind to components of the clathrin coat, such as the major adaptor protein, AP2. Receptors with higher affinity for AP2 are known to be more strongly internalized compared to receptors with lower affinity. However, it remains unclear how receptors with different affinities compete for space within crowded endocytic structures. To address this question, we constructed receptors with varying affinities for AP2 and allowed them to compete against one another during internalization. As expected, the internalization of a receptor with high affinity for AP2 was reduced when it was coexpressed with a competing receptor of similar affinity. However, receptors of low affinity for AP2 were surprisingly difficult to displace from endocytic structures, even when expressed alongside receptors with much higher affinity. To understand how these low-affinity receptors are protected from competition, we looked at AP2 heterogeneity across clathrin-coated structures. When we examined structures with lower-than-average AP2 content, we found that they were relatively enriched in cargo of low affinity for AP2 and depleted of cargo with high affinity. These findings suggest that the heterogeneity of adaptor protein content across the population of endocytic structures enables the internalization of diverse receptors. Given the critical role that internalization plays in signaling, this effect may help to prevent strongly internalized receptors from interfering with the cell's ability to process signals from weakly internalized receptors.
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Affiliation(s)
| | - Sadhana Gollapudi
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Chi Zhao
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Megan F. LaMonica
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Jeanne C. Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin
- Institute for Cellular and Molecular Biology, The University of Texas at Austin
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12
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Arora D, Damme DV. Motif-based endomembrane trafficking. PLANT PHYSIOLOGY 2021; 186:221-238. [PMID: 33605419 PMCID: PMC8154067 DOI: 10.1093/plphys/kiab077] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/17/2021] [Indexed: 05/08/2023]
Abstract
Endomembrane trafficking, which allows proteins and lipids to flow between the different endomembrane compartments, largely occurs by vesicle-mediated transport. Transmembrane proteins intended for transport are concentrated into a vesicle or carrier by undulation of a donor membrane. This is followed by vesicle scission, uncoating, and finally, fusion at the target membrane. Three major trafficking pathways operate inside eukaryotic cells: anterograde, retrograde, and endocytic. Each pathway involves a unique set of machinery and coat proteins that pack the transmembrane proteins, along with their associated lipids, into specific carriers. Adaptor and coatomer complexes are major facilitators that function in anterograde transport and in endocytosis. These complexes recognize the transmembrane cargoes destined for transport and recruit the coat proteins that help form the carriers. These complexes use either linear motifs or posttranslational modifications to recognize the cargoes, which are then packaged and delivered along the trafficking pathways. In this review, we focus on the different trafficking complexes that share a common evolutionary branch in Arabidopsis (Arabidopsis thaliana), and we discuss up-to-date knowledge about the cargo recognition motifs they use.
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Affiliation(s)
- Deepanksha Arora
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, Ghent 9052, Belgium
- VIB Center for Plant Systems Biology, Technologiepark 71, Ghent 9052, Belgium
| | - Daniёl Van Damme
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, Ghent 9052, Belgium
- VIB Center for Plant Systems Biology, Technologiepark 71, Ghent 9052, Belgium
- Author for communication:
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13
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Zaghmi A, Drouin-Ouellet J, Brambilla D, Gauthier MA. Treating brain diseases using systemic parenterally-administered protein therapeutics: Dysfunction of the brain barriers and potential strategies. Biomaterials 2020; 269:120461. [PMID: 33218788 DOI: 10.1016/j.biomaterials.2020.120461] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 09/23/2020] [Accepted: 10/18/2020] [Indexed: 12/12/2022]
Abstract
The parenteral administration of protein therapeutics is increasingly gaining importance for the treatment of human diseases. However, the presence of practically impermeable blood-brain barriers greatly restricts access of such pharmaceutics to the brain. Treating brain disorders with proteins thus remains a great challenge, and the slow clinical translation of these therapeutics may be largely ascribed to the lack of appropriate brain delivery system. Exploring new approaches to deliver proteins to the brain by circumventing physiological barriers is thus of great interest. Moreover, parallel advances in the molecular neurosciences are important for better characterizing blood-brain interfaces, particularly under different pathological conditions (e.g., stroke, multiple sclerosis, Parkinson's disease, and Alzheimer's disease). This review presents the current state of knowledge of the structure and the function of the main physiological barriers of the brain, the mechanisms of transport across these interfaces, as well as alterations to these concomitant with brain disorders. Further, the different strategies to promote protein delivery into the brain are presented, including the use of molecular Trojan horses, the formulation of nanosystems conjugated/loaded with proteins, protein-engineering technologies, the conjugation of proteins to polymers, and the modulation of intercellular junctions. Additionally, therapeutic approaches for brain diseases that do not involve targeting to the brain are presented (i.e., sink and scavenging mechanisms).
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Affiliation(s)
- A Zaghmi
- Institut National de la Recherche Scientifique (INRS), EMT Research Center, Varennes, QC, J3X 1S2, Canada
| | - J Drouin-Ouellet
- Faculty of Pharmacy, Université de Montréal, CP 6128, succ. Centre-ville, Montréal, QC, H3C 3J7, Canada
| | - D Brambilla
- Faculty of Pharmacy, Université de Montréal, CP 6128, succ. Centre-ville, Montréal, QC, H3C 3J7, Canada
| | - M A Gauthier
- Institut National de la Recherche Scientifique (INRS), EMT Research Center, Varennes, QC, J3X 1S2, Canada.
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14
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Jang E, Robert J, Rohrer L, von Eckardstein A, Lee WL. Transendothelial transport of lipoproteins. Atherosclerosis 2020; 315:111-125. [PMID: 33032832 DOI: 10.1016/j.atherosclerosis.2020.09.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/15/2020] [Accepted: 09/18/2020] [Indexed: 02/06/2023]
Abstract
The accumulation of low-density lipoproteins (LDL) in the arterial wall plays a pivotal role in the initiation and pathogenesis of atherosclerosis. Conversely, the removal of cholesterol from the intima by cholesterol efflux to high density lipoproteins (HDL) and subsequent reverse cholesterol transport shall confer protection against atherosclerosis. To reach the subendothelial space, both LDL and HDL must cross the intact endothelium. Traditionally, this transit is explained by passive filtration. This dogma has been challenged by the identification of several rate-limiting factors namely scavenger receptor SR-BI, activin like kinase 1, and caveolin-1 for LDL as well as SR-BI, ATP binding cassette transporter G1, and endothelial lipase for HDL. In addition, estradiol, vascular endothelial growth factor, interleukins 6 and 17, purinergic signals, and sphingosine-1-phosphate were found to regulate transendothelial transport of either LDL or HDL. Thorough understanding of transendothelial lipoprotein transport is expected to elucidate new therapeutic targets for the treatment or prevention of atherosclerotic cardiovascular disease and the development of strategies for the local delivery of drugs or diagnostic tracers into diseased tissues including atherosclerotic lesions.
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Affiliation(s)
- Erika Jang
- Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada
| | - Jerome Robert
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland
| | - Lucia Rohrer
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland.
| | - Warren L Lee
- Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada; Interdepartmental Division of Critical Care, Department of Medicine, University of Toronto, Canada; Department of Biochemistry, University of Toronto, Canada; Institute of Medical Science, University of Toronto, Canada.
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15
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Yarwood R, Hellicar J, Woodman PG, Lowe M. Membrane trafficking in health and disease. Dis Model Mech 2020; 13:13/4/dmm043448. [PMID: 32433026 PMCID: PMC7197876 DOI: 10.1242/dmm.043448] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Membrane trafficking pathways are essential for the viability and growth of cells, and play a major role in the interaction of cells with their environment. In this At a Glance article and accompanying poster, we outline the major cellular trafficking pathways and discuss how defects in the function of the molecular machinery that mediates this transport lead to various diseases in humans. We also briefly discuss possible therapeutic approaches that may be used in the future treatment of trafficking-based disorders. Summary: This At a Glance article and poster summarise the major intracellular membrane trafficking pathways and associated molecular machineries, and describe how defects in these give rise to disease in humans.
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Affiliation(s)
- Rebecca Yarwood
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - John Hellicar
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Philip G Woodman
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Martin Lowe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
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16
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Hsiung YC, Lin PC, Chen CS, Tung YC, Yang WS, Chen PL, Su TC. Identification of a novel LDLR disease-causing variant using capture-based next-generation sequencing screening of familial hypercholesterolemia patients in Taiwan. Atherosclerosis 2019; 277:440-447. [PMID: 30270083 DOI: 10.1016/j.atherosclerosis.2018.08.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 08/10/2018] [Accepted: 08/21/2018] [Indexed: 12/30/2022]
Abstract
BACKGROUND AND AIMS Familial hypercholesterolemia (FH) is an autosomal dominant disorder with paramount health impacts. However, less than 1% FH patients in Taiwan were formally diagnosed, partly due to the lack of reliable cost-effective genetic testing. We aimed at using a next-generation sequencing (NGS) platform as the clinical genetic testing method for FH. METHODS We designed probes to capture the whole LDLR gene and all coding sequences of APOB and PCSK9, and then sequenced with Illumina MiSeq platform (2 × 300 bps). The entire pipeline was tested on 13 DNA samples with known causative variants (including 3 large duplications and 2 large deletions). Then we enrolled a new cohort of 28 unrelated FH patients with Dutch Lipid Clinic Network score ≥5. Relatives were included in the cascade screening. RESULTS From the 13 DNA samples, we correctly identify all the variants, including big duplications and deletions. From the new cohort, we identified the causative variants in 21 of the 28 unrelated probands; five of them carrying a novel splice site variant c.1186+2T>G in LDLR. Among the family members, the concentration of LDL cholesterol was 7.82 ± 2.13 mmol/l in LDLR c.1186+2T>G carrier group (n = 26), and was significantly higher than 3.18 ± 1.36 mmol/l in the non-carrier group (n = 25). CONCLUSIONS This is the first capture-based NGS testing for FH to cover the whole LDLR genomic region, and therefore making reliable structural variation detection. This panel can comprehensively detect disease-causing variants in LDLR, APOB, and PCSK9 for FH patients.
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Affiliation(s)
- Yun-Chieh Hsiung
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Po-Chih Lin
- Department of Internal Medicine and Cardiovascular Center, National Taiwan University Hospital, Taipei, Taiwan
| | - Chih-Shan Chen
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Yi-Ching Tung
- Department of Pediatrics, National Taiwan University Hospital and College of Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Wei-Shiung Yang
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan; Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan; Division of Endocrinology and Metabolism, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan; Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, Taiwan; Department of Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Pei-Lung Chen
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan; Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan; Division of Endocrinology and Metabolism, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan; Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, Taiwan; Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan.
| | - Ta-Chen Su
- Department of Internal Medicine and Cardiovascular Center, National Taiwan University Hospital, Taipei, Taiwan; Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University College of Public Health, Taipei, Taiwan.
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17
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Sanger A, Hirst J, Davies AK, Robinson MS. Adaptor protein complexes and disease at a glance. J Cell Sci 2019; 132:132/20/jcs222992. [PMID: 31636158 DOI: 10.1242/jcs.222992] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Adaptor protein (AP) complexes are heterotetramers that select cargo for inclusion into transport vesicles. Five AP complexes (AP-1 to AP-5) have been described, each with a distinct localisation and function. Furthermore, patients with a range of disorders, particularly involving the nervous system, have now been identified with mutations in each of the AP complexes. In many cases this has been correlated with aberrantly localised membrane proteins. In this Cell Science at a Glance article and the accompanying poster, we summarize what is known about the five AP complexes and discuss how this helps to explain the clinical features of the different genetic disorders.
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Affiliation(s)
- Anneri Sanger
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Jennifer Hirst
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Alexandra K Davies
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Margaret S Robinson
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
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18
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DeGroot ACM, Zhao C, LaMonica MF, Hayden CC, Stachowiak JC. Molecular thermodynamics of receptor competition for endocytic uptake. SOFT MATTER 2019; 15:7448-7461. [PMID: 31502617 PMCID: PMC6918483 DOI: 10.1039/c9sm00876d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Endocytic uptake of receptors from the cell surface plays an important role in diverse processes from cell signaling to nutrient internalization. Understanding the mechanisms by which endocytic structures select receptors for internalization is of fundamental importance to our understanding of cellular physiology. Binding of receptors to the endocytic protein machinery is known to facilitate receptor loading into endocytic structures. However, many receptor species use the same small set of biochemical motifs to interact with the endocytic machinery, suggesting that receptors may compete for a limited number of binding sites within endocytic structures. Previous studies have shown that such competition can substantially modify receptor uptake. However, a predictive biophysical understanding of this phenomenon is currently lacking. Toward addressing this gap, here we employ quantitative imaging and statistical thermodynamics to measure and predict the competition between two distinct receptor species that are internalized simultaneously from the cell surface. Our studies demonstrate that when receptors compete for the same interactions with the endocytic machinery, their uptake is fundamentally coupled. Importantly, we find that these trends can be quantitatively predicted by a simple thermodynamic analysis. These results suggest that multiple receptor species reach an equilibrium partitioning between endocytic structures and the surrounding plasma membrane as the receptors compete for occupancy within dynamic endocytic structures. More broadly, this work provides a quantitative framework for predicting the impact of competition on receptor uptake, an effect which has the potential to physically couple signaling pathways that impact diverse aspects of cellular physiology.
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Affiliation(s)
- Andre C M DeGroot
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
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19
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Zhao C, DeGroot ACM, Hayden CC, Houser JR, Ali HA, LaMonica MF, Stachowiak JC. Receptor Heterodimerization Modulates Endocytosis through Collaborative and Competitive Mechanisms. Biophys J 2019; 117:646-658. [PMID: 31358286 PMCID: PMC6712433 DOI: 10.1016/j.bpj.2019.07.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 06/05/2019] [Accepted: 07/08/2019] [Indexed: 12/20/2022] Open
Abstract
Recruitment of receptors into clathrin-coated structures is essential to signal transduction and nutrient uptake. Among the many receptors involved in these processes, a significant fraction forms dimers. Dimerization of identical partners has generally been thought to promote receptor recruitment for uptake because of increased affinity of the dimer for the endocytic machinery. But what happens when receptors with substantially different affinities for the endocytic machinery come together to form a heterodimer? Evidence from diverse receptor classes, including G-protein-coupled receptors and receptor tyrosine kinases, suggests that heterodimerization with a strongly recruited receptor can drive significant recruitment of a receptor that lacks direct interactions with the endocytic machinery. However, a systematic biophysical understanding of this effect has yet to be established. Motivated by the potential of such events to influence cell signaling, here, we investigate the impact of receptor heterodimerization on endocytic recruitment using a family of engineered model receptors. As expected, we find that dimerization of a weakly recruited receptor with a strongly recruited receptor promotes incorporation of the weakly recruited receptor to endocytic structures. However, the effectiveness of this collaborative mechanism depends heavily on the relative strengths of endocytic recruitment of the two receptors that make up the dimer. Specifically, as the strength of endocytic recruitment of the weakly recruited receptor approaches that of the strongly recruited receptor, monomers of each receptor compete with heterodimers for space within endocytic structures. In this regime, the presence of the strongly recruited receptor drives a reduction in incorporation of the weakly recruited receptor into clathrin-coated structures. Similarly, as the strength of the dimer bond between the two receptors is progressively weakened, competition begins to dominate over collaboration. Collectively, these results demonstrate that the impact of receptor heterodimerization on endocytic recruitment is controlled by a delicate balance between collaborative and competitive mechanisms.
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Affiliation(s)
- Chi Zhao
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Andre C M DeGroot
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Carl C Hayden
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Justin R Houser
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Hisham A Ali
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Megan F LaMonica
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas; Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas.
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20
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Abstract
On January 21, 2017, I received an E-mail from Herb Tabor that I had been simultaneously hoping for and dreading for several years: an invitation to write a "Reflections" article for the Journal of Biological Chemistry On the one hand, I was honored to receive an invitation from Herb, a man I have admired for over 40 years, known for 24 years, and worked with as a member of the Editorial Board and Associate Editor of the Journal of Biological Chemistry for 17 years. On the other hand, the invitation marked the waning of my career as an academic scientist. With these conflicting emotions, I wrote this article with the goals of recording my career history and recognizing the many mentors, trainees, and colleagues who have contributed to it and, perhaps with pretension, with the desire that students who are beginning a career in research will find inspiration in the path I have taken and appreciate the importance of luck.
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Affiliation(s)
- David W Russell
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046
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21
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DeGroot ACM, Busch DJ, Hayden CC, Mihelic SA, Alpar AT, Behar M, Stachowiak JC. Entropic Control of Receptor Recycling Using Engineered Ligands. Biophys J 2019; 114:1377-1388. [PMID: 29590595 DOI: 10.1016/j.bpj.2018.01.036] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/16/2018] [Accepted: 01/23/2018] [Indexed: 01/04/2023] Open
Abstract
Receptor internalization by endocytosis regulates diverse cellular processes, from the rate of nutrient uptake to the timescale of essential signaling events. The established view is that internalization is tightly controlled by specific protein-binding interactions. However, recent work suggests that physical aspects of receptors influence the process in ways that cannot be explained by biochemistry alone. Specifically, work from several groups suggests that increasing the steric bulk of receptors may inhibit their uptake by multiple types of trafficking vesicles. How do biochemical and biophysical factors work together to control internalization? Here, we show that receptor uptake is well described by a thermodynamic trade-off between receptor-vesicle binding energy and the entropic cost of confining receptors within endocytic vesicles. Specifically, using large ligands to acutely increase the size of engineered variants of the transferrin receptor, we demonstrate that an increase in the steric bulk of a receptor dramatically decreases its probability of uptake by clathrin-coated structures. Further, in agreement with a simple thermodynamic analysis, all data collapse onto a single trend relating fractional occupancy of the endocytic structure to fractional occupancy of the surrounding plasma membrane, independent of receptor size. This fundamental scaling law provides a simple tool for predicting the impact of receptor expression level, steric bulk, and the size of endocytic structures on receptor uptake. More broadly, this work suggests that bulky ligands could be used to drive the accumulation of specific receptors at the plasma membrane surface, providing a biophysical tool for targeted modulation of signaling and metabolism from outside the cell.
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Affiliation(s)
- Andre C M DeGroot
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - David J Busch
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Carl C Hayden
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Samuel A Mihelic
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Aaron T Alpar
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Marcelo Behar
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas; Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas.
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22
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Mani I, Pandey KN. Emerging concepts of receptor endocytosis and concurrent intracellular signaling: Mechanisms of guanylyl cyclase/natriuretic peptide receptor-A activation and trafficking. Cell Signal 2019; 60:17-30. [PMID: 30951863 DOI: 10.1016/j.cellsig.2019.03.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/27/2019] [Accepted: 03/28/2019] [Indexed: 12/15/2022]
Abstract
Endocytosis is a prominent clathrin-mediated mechanism for concentrated uptake and internalization of ligand-receptor complexes, also known as cargo. Internalization of cargo is the fundamental mechanism for receptor-dependent regulation of cell membrane function, intracellular signal transduction, and neurotransmission, as well as other biological and physiological activities. However, the intrinsic mechanisms of receptor endocytosis and contemporaneous intracellular signaling are not well understood. We review emerging concepts of receptor endocytosis with concurrent intracellular signaling, using a typical example of guanylyl cyclase/natriuretic peptide receptor-A (NPRA) internalization, subcellular trafficking, and simultaneous generation of second-messenger cGMP and signaling in intact cells. We highlight the role of short-signal motifs located in the carboxyl-terminal regions of membrane receptors during their internalization and subsequent receptor trafficking in organelles that are not traditionally studied in this context, including nuclei and mitochondria. This review sheds light on the importance of future investigations of receptor endocytosis and trafficking in live cells and intact animals in vivo in physiological context.
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Affiliation(s)
- Indra Mani
- Department of Physiology, Tulane University Health Sciences Center and School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States
| | - Kailash N Pandey
- Department of Physiology, Tulane University Health Sciences Center and School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States.
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23
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Hori M, Miyauchi E, Son C, Harada-Shiba M. Detection of the benign c.2579C>T (p.A860V) variant of the LDLR gene in a pedigree-based genetic analysis of familial hypercholesterolemia. J Clin Lipidol 2019; 13:335-339. [DOI: 10.1016/j.jacl.2019.01.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/09/2019] [Accepted: 01/10/2019] [Indexed: 12/21/2022]
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24
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Ma S, Sun W, Gao L, Liu S. Therapeutic targets of hypercholesterolemia: HMGCR and LDLR. Diabetes Metab Syndr Obes 2019; 12:1543-1553. [PMID: 31686875 PMCID: PMC6709517 DOI: 10.2147/dmso.s219013] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 07/25/2019] [Indexed: 12/14/2022] Open
Abstract
Cholesterol homeostasis is critical and necessary for the body's functions. Hypercholesterolemia can lead to significant clinical problems, such as cardiovascular disease (CVD). 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and low-density lipoprotein cholesterol receptor (LDLR) are major points of control in cholesterol homeostasis. We summarize the regulatory mechanisms of HMGCR and LDLR, which may provide insight for new drug design and development.
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Affiliation(s)
- Shizhan Ma
- Department of Endocrinology and Metabolism, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan250021, People’s Republic of China
- Department of Endocrinology and Metabolism, Shandong Provincial Hospital Affiliated to Shandong University, Jinan250021, People’s Republic of China
| | - Wenxiu Sun
- Department of Pharmacy, Taishan Vocational College of Nursing, Taian271000, People’s Republic of China
| | - Ling Gao
- Department of Endocrinology and Metabolism, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan250021, People’s Republic of China
- Scientific Center, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan250021, People’s Republic of China
- Scientific Center, Shandong Provincial Hospital Affiliated to Shandong University, Jinan250021, People’s Republic of China
- Correspondence: Ling GaoScientific Center, Shandong Provincial Hospital Affiliated to Shandong University, 324 Jing 5 Road, Jinan, Shandong Province250021, People’s Republic of ChinaTel +86 531 6877 6910Email
| | - Shudong Liu
- Department of Endocrinology, Shandong Rongjun General Hospital, Jinan250013, People’s Republic of China
- Shudong LiuDepartment of Endocrinology, Shandong Rongjun General Hospital, 23 Jiefang Road, Jinan, Shandong Province250013, People’s Republic of ChinaTel +86 531 8238 2351Email
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Validation of LDLr Activity as a Tool to Improve Genetic Diagnosis of Familial Hypercholesterolemia: A Retrospective on Functional Characterization of LDLr Variants. Int J Mol Sci 2018; 19:ijms19061676. [PMID: 29874871 PMCID: PMC6032215 DOI: 10.3390/ijms19061676] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 05/28/2018] [Accepted: 06/04/2018] [Indexed: 12/11/2022] Open
Abstract
Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by high blood-cholesterol levels mostly caused by mutations in the low-density lipoprotein receptor (LDLr). With a prevalence as high as 1/200 in some populations, genetic screening for pathogenic LDLr mutations is a cost-effective approach in families classified as ‘definite’ or ‘probable’ FH and can help to early diagnosis. However, with over 2000 LDLr variants identified, distinguishing pathogenic mutations from benign mutations is a long-standing challenge in the field. In 1998, the World Health Organization (WHO) highlighted the importance of improving the diagnosis and prognosis of FH patients thus, identifying LDLr pathogenic variants is a longstanding challenge to provide an accurate genetic diagnosis and personalized treatments. In recent years, accessible methodologies have been developed to assess LDLr activity in vitro, providing experimental reproducibility between laboratories all over the world that ensures rigorous analysis of all functional studies. In this review we present a broad spectrum of functionally characterized missense LDLr variants identified in patients with FH, which is mandatory for a definite diagnosis of FH.
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A novel indel variant in LDLR responsible for familial hypercholesterolemia in a Chinese family. PLoS One 2017; 12:e0189316. [PMID: 29228028 PMCID: PMC5724832 DOI: 10.1371/journal.pone.0189316] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/22/2017] [Indexed: 01/10/2023] Open
Abstract
Familial hypercholesterolemia (FH) is an inherited disorder characterized by elevation of serum cholesterol bound to low-density lipoprotein. Mutations in LDLR are the major factors responsible for FH. In this study, we recruited a four-generation Chinese family with FH and identified the clinical features of hypercholesterolemia. All affected individuals shared a novel indel mutation (c.1885_1889delinsGATCATCAACC) in exon 13 of LDLR. The mutation segregated with the hypercholesterolemia phenotype in the family. To analyze the function of the indel, we established stable clones of mutant and wild-type LDLR in Hep G2 cells. The mutant LDLR was retained in the endoplasmic reticulum (ER) and failed to glycosylate via the Golgi. Moreover, the membrane LDLR was reduced and lost the ability to take up LDL. Our data also expand the spectrum of known LDLR mutations.
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Naeli P, Mirzadeh Azad F, Malakootian M, Seidah NG, Mowla SJ. Post-transcriptional Regulation of PCSK9 by miR-191, miR-222, and miR-224. Front Genet 2017; 8:189. [PMID: 29230236 PMCID: PMC5711823 DOI: 10.3389/fgene.2017.00189] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Accepted: 11/13/2017] [Indexed: 12/24/2022] Open
Abstract
Since proprotein convertase subtilisin kexin 9 (PCSK9) discovery, a gene involved in LDL metabolism regulation and cardiovascular diseases (CVD), many therapeutic strategies have been introduced for direct targeting of PCSK9. The main goal of these strategies has been to reduce PCSK9 protein level either by application of antibodies or inhibition of its production. In this study, we have tried to discover microRNAs (miRNAs) which can target, and hence regulate, PCSK9 expression. Using bioinformatics tools, we selected three microRNAs with binding sites on 3′-UTR of PCSK9. The expression level of these miRNAs was examined in three different cell lines using real-time RT-PCR. We observed a reciprocal expression pattern between expression level of miR-191, miR-222, and miR-224 with that of PCSK9. Accordingly, the expression levels were highest in Huh7 cells which expressed the lowest level of PCSK9, compared to HepG2 and A549 cell lines. PCSK9 mRNA level also showed a significant decline in HepG2 cells transfected with the vectors overexpressing the aforementioned miRNAs. Furthermore, the miRNAs target sites were cloned in psiCHECK-2 vector, and a direct interaction of the miRNAs and the PCSK9 3′-UTR putative target sites was investigated by means of luciferase assay. Our findings revealed that miR-191, miR-222, and miR-224 can directly interact with PCSK9 3′-UTR and regulate its expression. In conclusion, our data introduces a role for miRNAs to regulate PCSK9 expression.
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Affiliation(s)
- Parisa Naeli
- Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Fatemeh Mirzadeh Azad
- Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mahshid Malakootian
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, QC, Canada
| | - Seyed J Mowla
- Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
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Cayo MA, Mallanna SK, Di Furio F, Jing R, Tolliver LB, Bures M, Urick A, Noto FK, Pashos EE, Greseth MD, Czarnecki M, Traktman P, Yang W, Morrisey EE, Grompe M, Rader DJ, Duncan SA. A Drug Screen using Human iPSC-Derived Hepatocyte-like Cells Reveals Cardiac Glycosides as a Potential Treatment for Hypercholesterolemia. Cell Stem Cell 2017; 20:478-489.e5. [PMID: 28388428 DOI: 10.1016/j.stem.2017.01.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 12/22/2016] [Accepted: 01/27/2017] [Indexed: 12/17/2022]
Abstract
Efforts to identify pharmaceuticals to treat heritable metabolic liver diseases have been hampered by the lack of models. However, cells with hepatocyte characteristics can be produced from induced pluripotent stem cells (iPSCs). Here, we have used hepatocyte-like cells generated from homozygous familial hypercholesterolemia (hoFH) iPSCs to identify drugs that can potentially be repurposed to lower serum LDL-C. We found that cardiac glycosides reduce the production of apolipoprotein B (apoB) from human hepatocytes in culture and the serum of avatar mice harboring humanized livers. The drugs act by increasing the turnover of apoB protein. Analyses of patient medical records revealed that the treatment of patients with cardiac glycosides reduced serum LDL-C levels. These studies highlight the effectiveness of using iPSCs to screen for potential treatments for inborn errors of hepatic metabolism and suggest that cardiac glycosides could provide an approach for reducing hepatocyte production of apoB and treating hypercholesterolemia.
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Affiliation(s)
- Max A Cayo
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Sunil K Mallanna
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Francesca Di Furio
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Ran Jing
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Lauren B Tolliver
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Matthew Bures
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Amanda Urick
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Fallon K Noto
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Evanthia E Pashos
- Departments of Medicine and Genetics and the Institute for Translational Medicine and Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matthew D Greseth
- Department of Microbiology and Immunology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Maciej Czarnecki
- Department of Microbiology and Immunology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA; Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Paula Traktman
- Department of Microbiology and Immunology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA; Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, MSC 955, Charleston, SC 29425, USA
| | - Wenli Yang
- Department of Medicine and Penn Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Edward E Morrisey
- Department of Medicine and Penn Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Markus Grompe
- Papé Family Pediatric Research Institute, Oregon Health & Science University, 3181 South West Sam Jackson Park Road/L321, Portland, OR 97239, USA
| | - Daniel J Rader
- Departments of Medicine and Genetics and the Institute for Translational Medicine and Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Stephen A Duncan
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, MSC 955, Charleston, SC 29425, USA.
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Zhang Y, Cao G, Zhu L, Chen F, Zar MS, Wang S, Hu X, Wei Y, Xue R, Gong C. Integrin beta and receptor for activated protein kinase C are involved in the cell entry of Bombyx mori cypovirus. Appl Microbiol Biotechnol 2017; 101:3703-3716. [PMID: 28175946 DOI: 10.1007/s00253-017-8158-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/23/2017] [Accepted: 01/25/2017] [Indexed: 12/22/2022]
Abstract
Receptor-mediated endocytosis using a β1 integrin-dependent internalization was considered as the primary mechanism for the initiation of mammalian reovirus infection. Bombyx mori cypovirus (BmCPV) is a member of Reoviridae family which mainly infects the midgut epithelium of silkworm; the cell entry of BmCPV is poorly explored. In this study, co-immunoprecipitation (Co-IP), virus overlay protein binding assay (VOPBA), and BmCPV-protein interaction on the polyvinylidene difluoride membrane (BmCPV-PI-PVDF) methods were employed to screen the interacting proteins of BmCPV, and several proteins including integrin beta and receptor for activated protein kinase C (RACK1) were identified as the candidate interacting proteins for establishing the infection of BmCPV. The infectivity of BmCPV was investigated in vivo and in vitro by RNA interference (RNAi) and antibody blocking methods, and the results showed that the infectivity of BmCPV was significantly reduced by either small interfering RNA-mediated silencing of integrin beta and RACK1 or antibody blocking of integrin beta and RACK1. The expression level of integrin beta or RACK1 is not the highest in the silkworm midgut which is a principal target tissue of BmCPV, suggesting that the molecules other than integrin beta or RACK1 might play a key role in determining the tissue tropism of BmCPV infection. The establishment of BmCPV infection depends on other factors, and these factors interacted with integrin beta and RACK1 to form receptor complex for the cell entry of BmCPV.
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Affiliation(s)
- Yiling Zhang
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
- Suzhou Municipal Key Laboratory of Molecular Diagnostics and Therapeutics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, 215163, People's Republic of China
| | - Guangli Cao
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
- National Engineering Laboratory for Modern Silk, Soochow University, Postal address: No. 199 Ren'ai Road, Suzhou Industrial Park, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Liyuan Zhu
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Fei Chen
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Mian Sahib Zar
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Simei Wang
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
- Department of Hematology, The First Affiliated Hospital of Gannan Medical College, Ganzhou, 341000, Jiangxi, People's Republic of China
| | - Xiaolong Hu
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
- National Engineering Laboratory for Modern Silk, Soochow University, Postal address: No. 199 Ren'ai Road, Suzhou Industrial Park, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Yuhong Wei
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Renyu Xue
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China
- National Engineering Laboratory for Modern Silk, Soochow University, Postal address: No. 199 Ren'ai Road, Suzhou Industrial Park, Suzhou, 215123, Jiangsu, People's Republic of China
| | - Chengliang Gong
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, Jiangsu, People's Republic of China.
- National Engineering Laboratory for Modern Silk, Soochow University, Postal address: No. 199 Ren'ai Road, Suzhou Industrial Park, Suzhou, 215123, Jiangsu, People's Republic of China.
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Tam JHK, Cobb MR, Seah C, Pasternak SH. Tyrosine Binding Protein Sites Regulate the Intracellular Trafficking and Processing of Amyloid Precursor Protein through a Novel Lysosome-Directed Pathway. PLoS One 2016; 11:e0161445. [PMID: 27776132 PMCID: PMC5077117 DOI: 10.1371/journal.pone.0161445] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 08/07/2016] [Indexed: 01/18/2023] Open
Abstract
The amyloid hypothesis posits that the production of β-amyloid (Aβ) aggregates leads to neurodegeneration and cognitive decline associated with AD. Aβ is produced by sequential cleavage of the amyloid precursor protein (APP) by β- and γ-secretase. While nascent APP is well known to transit to the endosomal/ lysosomal system via the cell surface, we have recently shown that APP can also traffic to lysosomes intracellularly via its interaction with AP-3. Because AP-3 interacts with cargo protein via interaction with tyrosine motifs, we mutated the three tyrosines motif in the cytoplasmic tail of APP. Here, we show that the YTSI motif interacts with AP-3, and phosphorylation of the serine in this motif disrupts the interaction and decreases APP trafficking to lysosomes. Furthermore, we show that phosphorylation at this motif can decrease the production of neurotoxic Aβ 42. This demonstrates that reducing APP trafficking to lysosomes may be a strategy to reduce Aβ 42 in Alzheimer’s disease.
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Affiliation(s)
- Joshua H. K. Tam
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, Western University, London Ontario, Canada, N6A 5B7
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada, N6A 5B7
| | - M. Rebecca Cobb
- Program in Neuroscience, Western University, London, Ontario, Canada, N6A 5B7
| | - Claudia Seah
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, Western University, London Ontario, Canada, N6A 5B7
| | - Stephen H. Pasternak
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, Western University, London Ontario, Canada, N6A 5B7
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada, N6A 5B7
- Program in Neuroscience, Western University, London, Ontario, Canada, N6A 5B7
- Department of Clinical Neurological Sciences, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada, N6A 5B7
- * E-mail:
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31
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Tao W, Moore R, Meng Y, Smith ER, Xu XX. Endocytic adaptors Arh and Dab2 control homeostasis of circulatory cholesterol. J Lipid Res 2016; 57:809-17. [PMID: 27005486 DOI: 10.1194/jlr.m063065] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Indexed: 11/20/2022] Open
Abstract
High serum cholesterol (hypercholesterolemia) strongly associates with cardiovascular diseases as the atherogenic LDLs promote atheroma development in arteries (atherosclerosis). LDL clearance from the circulation by LDL receptor (LDLR)-mediated endocytosis by hepatic and peripheral tissues and subsequent feedback regulation of endogenous synthesis of cholesterol is a key determinant of serum LDL level. Human mutation analysis revealed that autosomal recessive hypercholesterolemia (ARH), an LDLR endocytic adaptor, perturbs LDLR function and thus impacts serum cholesterol levels. In our genetic analysis of mutant mice, we found that deletion of another LDLR endocytic adaptor, Disabled-2 (Dab2), only slightly affected serum cholesterol levels. However, elimination of both arh and dab2 genes in mice resulted in profound hypercholesterolemia similar to that resulting from ldlr homozygous deletion. In the liver, Dab2 is expressed in sinusoid endothelial cells but not in hepatocytes. When deleting both Dab2 and Arh, HMG-CoA reductase level increased to the level similar to that of ldlr knockout. Thus, in the absence of Arh, Dab2 in liver endothelial cells regulates cholesterol synthesis in hepatocytes. We conclude that the combination of Arh and Dab2 is responsible for the majority of adaptor function in LDLR endocytosis and LDLR-mediated cholesterol homeostasis.
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Affiliation(s)
- Wensi Tao
- Department of Cell Biology, Molecular Cell and Developmental Biology Graduate Program, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Robert Moore
- Department of Cell Biology, Molecular Cell and Developmental Biology Graduate Program, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Yue Meng
- Department of Cell Biology, Molecular Cell and Developmental Biology Graduate Program, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Elizabeth R Smith
- Department of Cell Biology, Molecular Cell and Developmental Biology Graduate Program, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Xiang-Xi Xu
- Department of Cell Biology, Molecular Cell and Developmental Biology Graduate Program, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136
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32
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Robinson MS. Forty Years of Clathrin-coated Vesicles. Traffic 2015; 16:1210-38. [PMID: 26403691 DOI: 10.1111/tra.12335] [Citation(s) in RCA: 221] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 09/16/2015] [Accepted: 09/16/2015] [Indexed: 12/11/2022]
Abstract
The purification of coated vesicles and the discovery of clathrin by Barbara Pearse in 1975 was a landmark in cell biology. Over the past 40 years, work from many labs has uncovered the molecular details of clathrin and its associated proteins, including how they assemble into a coated vesicle and how they select cargo. Unexpected connections have been found with signalling, development, neuronal transmission, infection, immunity and genetic disorders. But there are still a number of unanswered questions, including how clathrin-mediated trafficking is regulated and how the machinery evolved.
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Affiliation(s)
- Margaret S Robinson
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
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Radovica-Spalvina I, Latkovskis G, Silamikelis I, Fridmanis D, Elbere I, Ventins K, Ozola G, Erglis A, Klovins J. Next-generation-sequencing-based identification of familial hypercholesterolemia-related mutations in subjects with increased LDL-C levels in a latvian population. BMC MEDICAL GENETICS 2015; 16:86. [PMID: 26415676 PMCID: PMC4587402 DOI: 10.1186/s12881-015-0230-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 09/15/2015] [Indexed: 12/30/2022]
Abstract
BACKGROUND Familial hypercholesterolemia (FH) is one of the commonest monogenic disorders, predominantly inherited as an autosomal dominant trait. When untreated, it results in early coronary heart disease. The vast majority of FH remains undiagnosed in Latvia. The identification and early treatment of affected individuals remain a challenge worldwide. Most cases of FH are caused by mutations in one of four genes, APOB, LDLR, PCSK9, or LDLRAP1. The spectrum of disease-causing variants is very diverse and the variation detection panels usually used in its diagnosis cover only a minority of the disease-causing gene variants. However, DNA-based tests may provide an FH diagnosis for FH patients with no physical symptoms and with no known family history of the disease. Here, we evaluate the use of targeted next-generation sequencing (NGS) to identify cases of FH in a cohort of patients with coronary artery disease (CAD) and individuals with abnormal low-density lipoprotein-cholesterol (LDL-C) levels. METHODS We used targeted amplification of the coding regions of LDLR, APOB, PCSK9, and LDLRAP1, followed by NGS, in 42 CAD patients (LDL-C, 4.1-7.2 mmol/L) and 50 individuals from a population-based cohort (LDL-C, 5.1-9.7 mmol/L). RESULTS In total, 22 synonymous and 31 nonsynonymous variants, eight variants in close proximity (10 bp) to intron-exon boundaries, and 50 other variants were found. We identified four pathogenic mutations (p.(Arg3527Gln) in APOB, and p.(Gly20Arg), p.(Arg350*), and c.1706-10G > A in LDLR) in seven patients (7.6 %). Three possible pathogenic variants were also found in four patients. CONCLUSION NGS-based methods can be used to detect FH in high-risk individuals when they do not meet the defined clinical criteria.
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Affiliation(s)
- Ilze Radovica-Spalvina
- Latvian Biomedical Research and Study Center, Ratsupites Street 1, Riga, LV-1067, Latvia.
| | - Gustavs Latkovskis
- Latvian Center of Cardiology, Pauls Stradins Clinical University Hospital, Pilsonu Street 13, Riga, LV-1002, Latvia. .,Faculty of Medicine, University of Latvia, Raina Blvd. 19, Riga, LV-1586, Latvia. .,Research Institute of Cardiology, University of Latvia, Pilsonu Street 13, Riga, LV-1002, Latvia.
| | - Ivars Silamikelis
- Latvian Biomedical Research and Study Center, Ratsupites Street 1, Riga, LV-1067, Latvia.
| | - Davids Fridmanis
- Latvian Biomedical Research and Study Center, Ratsupites Street 1, Riga, LV-1067, Latvia.
| | - Ilze Elbere
- Latvian Biomedical Research and Study Center, Ratsupites Street 1, Riga, LV-1067, Latvia.
| | - Karlis Ventins
- Vidzemes Hospital, Jumaras Street 195, Valmiera, LV-4201, Latvia.
| | - Guna Ozola
- Latvian Center of Cardiology, Pauls Stradins Clinical University Hospital, Pilsonu Street 13, Riga, LV-1002, Latvia.
| | - Andrejs Erglis
- Latvian Center of Cardiology, Pauls Stradins Clinical University Hospital, Pilsonu Street 13, Riga, LV-1002, Latvia. .,Faculty of Medicine, University of Latvia, Raina Blvd. 19, Riga, LV-1586, Latvia. .,Research Institute of Cardiology, University of Latvia, Pilsonu Street 13, Riga, LV-1002, Latvia.
| | - Janis Klovins
- Latvian Biomedical Research and Study Center, Ratsupites Street 1, Riga, LV-1067, Latvia.
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Endocytosis and Trafficking of Natriuretic Peptide Receptor-A: Potential Role of Short Sequence Motifs. MEMBRANES 2015; 5:253-87. [PMID: 26151885 PMCID: PMC4584282 DOI: 10.3390/membranes5030253] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 06/25/2015] [Accepted: 06/25/2015] [Indexed: 12/19/2022]
Abstract
The targeted endocytosis and redistribution of transmembrane receptors among membrane-bound subcellular organelles are vital for their correct signaling and physiological functions. Membrane receptors committed for internalization and trafficking pathways are sorted into coated vesicles. Cardiac hormones, atrial and brain natriuretic peptides (ANP and BNP) bind to guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) and elicit the generation of intracellular second messenger cyclic guanosine 3',5'-monophosphate (cGMP), which lowers blood pressure and incidence of heart failure. After ligand binding, the receptor is rapidly internalized, sequestrated, and redistributed into intracellular locations. Thus, NPRA is considered a dynamic cellular macromolecule that traverses different subcellular locations through its lifetime. The utilization of pharmacologic and molecular perturbants has helped in delineating the pathways of endocytosis, trafficking, down-regulation, and degradation of membrane receptors in intact cells. This review describes the investigation of the mechanisms of internalization, trafficking, and redistribution of NPRA compared with other cell surface receptors from the plasma membrane into the cell interior. The roles of different short-signal peptide sequence motifs in the internalization and trafficking of other membrane receptors have been briefly reviewed and their potential significance in the internalization and trafficking of NPRA is discussed.
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36
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Thormaehlen AS, Schuberth C, Won HH, Blattmann P, Joggerst-Thomalla B, Theiss S, Asselta R, Duga S, Merlini PA, Ardissino D, Lander ES, Gabriel S, Rader DJ, Peloso GM, Pepperkok R, Kathiresan S, Runz H. Systematic cell-based phenotyping of missense alleles empowers rare variant association studies: a case for LDLR and myocardial infarction. PLoS Genet 2015; 11:e1004855. [PMID: 25647241 PMCID: PMC4409815 DOI: 10.1371/journal.pgen.1004855] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/27/2014] [Indexed: 01/08/2023] Open
Abstract
A fundamental challenge to contemporary genetics is to distinguish rare missense alleles that disrupt protein functions from the majority of alleles neutral on protein activities. High-throughput experimental tools to securely discriminate between disruptive and non-disruptive missense alleles are currently missing. Here we establish a scalable cell-based strategy to profile the biological effects and likely disease relevance of rare missense variants in vitro. We apply this strategy to systematically characterize missense alleles in the low-density lipoprotein receptor (LDLR) gene identified through exome sequencing of 3,235 individuals and exome-chip profiling of 39,186 individuals. Our strategy reliably identifies disruptive missense alleles, and disruptive-allele carriers have higher plasma LDL-cholesterol (LDL-C). Importantly, considering experimental data refined the risk of rare LDLR allele carriers from 4.5- to 25.3-fold for high LDL-C, and from 2.1- to 20-fold for early-onset myocardial infarction. Our study generates proof-of-concept that systematic functional variant profiling may empower rare variant-association studies by orders of magnitude. Exome sequencing has proven powerful to identify protein-coding variation across the human genome, unravel the basis of monogenic diseases and discover rare alleles that confer risk for complex disease. Nevertheless, two key challenges limit its application to complex phenotypes: first, most alleles identified in a population are extremely rare; and second, most alleles are neutral on protein activities. Consequently, association tests that rely on enumerating rare alleles in cases and controls (termed rare variant association studies, RVAS) are typically underpowered, as the many neutral alleles dampen signals that arise from the few alleles that disrupt protein functions. Strategies to securely discriminate disruptive from neutral variants are immature, in particular for missense variants. Here we show that the statistical power of RVAS improves dramatically if variants are stratified according to their in vitro ascertained functions. We establish scalable technology to objectively profile the biological effects of exome-identified missense variants in the low-density lipoprotein receptor (LDLR) through systematic overexpression and complementation experiments in cells. We demonstrate that carriers of LDLR alleles, which our experiments identify as “disruptive-missense”, have higher plasma LDL-C, and that considering in vitro data may make it possible to reduce RVAS sample sizes by more than 2-fold.
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Affiliation(s)
- Aenne S. Thormaehlen
- Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany
- Molecular Medicine Partnership Unit (MMPU), University of Heidelberg/ EMBL, Heidelberg, Germany
| | - Christian Schuberth
- Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany
- Molecular Medicine Partnership Unit (MMPU), University of Heidelberg/ EMBL, Heidelberg, Germany
| | - Hong-Hee Won
- Center of Human Genetic Research (CHGR), Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Peter Blattmann
- Molecular Medicine Partnership Unit (MMPU), University of Heidelberg/ EMBL, Heidelberg, Germany
- Cell Biology/Biophysics Unit, European Molecular Biological Laboratory, Heidelberg, Germany
| | - Brigitte Joggerst-Thomalla
- Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany
- Molecular Medicine Partnership Unit (MMPU), University of Heidelberg/ EMBL, Heidelberg, Germany
| | - Susanne Theiss
- Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany
| | | | | | | | | | - Eric S. Lander
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Stacey Gabriel
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Daniel J. Rader
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Gina M. Peloso
- Center of Human Genetic Research (CHGR), Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Rainer Pepperkok
- Molecular Medicine Partnership Unit (MMPU), University of Heidelberg/ EMBL, Heidelberg, Germany
- Cell Biology/Biophysics Unit, European Molecular Biological Laboratory, Heidelberg, Germany
| | - Sekar Kathiresan
- Center of Human Genetic Research (CHGR), Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Division of Cardiology, Ospedale Niguarda, Milan, Italy
| | - Heiko Runz
- Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany
- Molecular Medicine Partnership Unit (MMPU), University of Heidelberg/ EMBL, Heidelberg, Germany
- Center of Human Genetic Research (CHGR), Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- * E-mail:
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37
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Wei J, Fu ZY, Li PS, Miao HH, Li BL, Ma YT, Song BL. The clathrin adaptor proteins ARH, Dab2, and numb play distinct roles in Niemann-Pick C1-Like 1 versus low density lipoprotein receptor-mediated cholesterol uptake. J Biol Chem 2014; 289:33689-700. [PMID: 25331956 PMCID: PMC4246119 DOI: 10.1074/jbc.m114.593764] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Revised: 10/08/2014] [Indexed: 12/21/2022] Open
Abstract
The uptake of circulating low density lipoproteins (LDL) is mediated by LDL receptor (LDLR) through clathrin-dependent endocytosis. At the early stage of this process, adaptor proteins ARH and Dab2 specifically bind the endocytic signal motif in LDLR and recruit clathrin/AP2 to initiate internalization. On the other hand, intestinal cholesterol is absorbed by Niemann-Pick C1-Like 1 (NPC1L1) through clathrin-dependent endocytosis. Another adaptor protein, Numb recognizes the endocytic motif in NPC1L1 C terminus and couples NPC1L1 to endocytic machinery. The ARH, Dab2, and Numb proteins contain a homogeneous phosphotyrosine binding (PTB) domain that directly binds endocytic motifs. Because ARH, Dab2, and Numb are all PTB domain family members, the emerging mystery is whether these adaptors act complementally in LDLR and NPC1L1 endocytosis. Here, we found that ARH and Dab2 did not bind NPC1L1 and were not required for NPC1L1 internalization. Similarly, Numb lacked the ability to interact with the LDLR C terminus and was dispensable for LDL uptake. Only the Numb isoforms with shorter PTB domain could facilitate NPC1L1 endocytosis. Besides the reported function in intestinal cholesterol absorption, Numb also mediated cholesterol reabsorption from bile in liver. We further identified a Numb variant with G595D substitution in humans of low blood LDL-cholesterol. The G595D substitution impaired NPC1L1 internalization and cholesterol reabsorption, due to attenuating affinity of Numb to clathrin/AP2. These results demonstrate that Numb specifically regulates NPC1L1-mediated cholesterol absorption both in human intestine and liver, distinct from ARH and Dab2, which selectively participate in LDLR-mediated LDL uptake.
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Affiliation(s)
- Jian Wei
- From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031
| | - Zhen-Yan Fu
- the Department of Cardiovascular Medicine, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, and
| | - Pei-Shan Li
- From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031
| | - Hong-Hua Miao
- From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031
| | - Bo-Liang Li
- From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031
| | - Yi-Tong Ma
- the Department of Cardiovascular Medicine, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, and
| | - Bao-Liang Song
- From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, the College of Life Sciences, Wuhan University, Wuhan 430072, China
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38
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Etxebarria A, Benito-Vicente A, Palacios L, Stef M, Cenarro A, Civeira F, Ostolaza H, Martin C. Functional Characterization and Classification of Frequent Low-Density Lipoprotein Receptor Variants. Hum Mutat 2014; 36:129-41. [DOI: 10.1002/humu.22721] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 10/24/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Aitor Etxebarria
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
| | - Asier Benito-Vicente
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
| | | | | | - Ana Cenarro
- Unidad de Lípidos and Laboratorio de Investigación Molecular; Hospital Universitario Miguel Servet; Instituto Aragonés de Ciencias de la Salud (IACS); Zaragoza Spain
| | - Fernando Civeira
- Unidad de Lípidos and Laboratorio de Investigación Molecular; Hospital Universitario Miguel Servet; Instituto Aragonés de Ciencias de la Salud (IACS); Zaragoza Spain
| | - Helena Ostolaza
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
| | - Cesar Martin
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
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39
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Etxebarria A, Benito-Vicente A, Alves AC, Ostolaza H, Bourbon M, Martin C. Advantages and versatility of fluorescence-based methodology to characterize the functionality of LDLR and class mutation assignment. PLoS One 2014; 9:e112677. [PMID: 25386756 PMCID: PMC4227843 DOI: 10.1371/journal.pone.0112677] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 10/10/2014] [Indexed: 12/16/2022] Open
Abstract
Familial hypercholesterolemia (FH) is a common autosomal codominant disease with a frequency of 1:500 individuals in its heterozygous form. The genetic basis of FH is most commonly mutations within the LDLR gene. Assessing the pathogenicity of LDLR variants is particularly important to give a patient a definitive diagnosis of FH. Current studies of LDLR activity ex vivo are based on the analysis of 125I-labeled lipoproteins (reference method) or fluorescent-labelled LDL. The main purpose of this study was to compare the effectiveness of these two methods to assess LDLR functionality in order to validate a functional assay to analyse LDLR mutations. LDLR activity of different variants has been studied by flow cytometry using FITC-labelled LDL and compared with studies performed previously with 125I-labeled lipoproteins. Flow cytometry results are in full agreement with the data obtained by the 125I methodology. Additionally confocal microscopy allowed the assignment of different class mutation to the variants assayed. Use of fluorescence yielded similar results than 125I-labeled lipoproteins concerning LDLR activity determination, and also allows class mutation classification. The use of FITC-labelled LDL is easier in handling and disposal, cheaper than radioactivity and can be routinely performed by any group doing LDLR functional validations.
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Affiliation(s)
- Aitor Etxebarria
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain
| | - Asier Benito-Vicente
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain
| | - Ana C. Alves
- Grupo de Investigação Cardiovascular, Unidade I&D, Departamento de Promoção da Saúde e Prevenção de Doenças Não Transmissíveis, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa 1649-040, Portugal
- Centre for Biodiversity, Functional and Integrative Genomics, Faculty of Sciences, University of Lisboa, 1749-016 Lisboa, Portugal
| | - Helena Ostolaza
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain
| | - Mafalda Bourbon
- Grupo de Investigação Cardiovascular, Unidade I&D, Departamento de Promoção da Saúde e Prevenção de Doenças Não Transmissíveis, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa 1649-040, Portugal
- Centre for Biodiversity, Functional and Integrative Genomics, Faculty of Sciences, University of Lisboa, 1749-016 Lisboa, Portugal
| | - Cesar Martin
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain
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40
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Antonescu CN, McGraw TE, Klip A. Reciprocal regulation of endocytosis and metabolism. Cold Spring Harb Perspect Biol 2014; 6:a016964. [PMID: 24984778 DOI: 10.1101/cshperspect.a016964] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The cellular uptake of many nutrients and micronutrients governs both their cellular availability and their systemic homeostasis. The cellular rate of nutrient or ion uptake (e.g., glucose, Fe(3+), K(+)) or efflux (e.g., Na(+)) is governed by a complement of membrane transporters and receptors that show dynamic localization at both the plasma membrane and defined intracellular membrane compartments. Regulation of the rate and mechanism of endocytosis controls the amounts of these proteins on the cell surface, which in many cases determines nutrient uptake or secretion. Moreover, the metabolic action of diverse hormones is initiated upon binding to surface receptors that then undergo regulated endocytosis and show distinct signaling patterns once internalized. Here, we examine how the endocytosis of nutrient transporters and carriers as well as signaling receptors governs cellular metabolism and thereby systemic (whole-body) metabolite homeostasis.
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Affiliation(s)
- Costin N Antonescu
- Department of Chemistry and Biology, Ryerson University, Toronto, Ontario M5B 2K3, Canada
| | - Timothy E McGraw
- Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10065
| | - Amira Klip
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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41
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Van Roey K, Uyar B, Weatheritt RJ, Dinkel H, Seiler M, Budd A, Gibson TJ, Davey NE. Short Linear Motifs: Ubiquitous and Functionally Diverse Protein Interaction Modules Directing Cell Regulation. Chem Rev 2014; 114:6733-78. [DOI: 10.1021/cr400585q] [Citation(s) in RCA: 293] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Kim Van Roey
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Bora Uyar
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Robert J. Weatheritt
- MRC
Laboratory of Molecular Biology (LMB), Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, United Kingdom
| | - Holger Dinkel
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Markus Seiler
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Aidan Budd
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Toby J. Gibson
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Norman E. Davey
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Department
of Physiology, University of California, San Francisco, San Francisco, California 94143, United States
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42
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Pieper-Fürst U, Lammert F. Low-density lipoprotein receptors in liver: old acquaintances and a newcomer. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1191-8. [PMID: 24046859 DOI: 10.1016/j.bbalip.2013.03.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The lipoprotein receptors low-density lipoprotein receptor (LDLR), the low-density lipoprotein receptor-related protein 1 (LRP1) and megalin/LRP2 share characteristic structural elements. In addition to their well-known roles in endocytosis of lipoproteins and systemic lipid homeostasis, it has been established that LRP1 mediates the endocytotic clearance of a multitude of extracellular ligands and regulates diverse signaling processes such as growth factor signaling, inflammatory signaling pathways, apoptosis, and phagocytosis in liver. Here, possible functions of LRP1 expression in hepatocytes and non-parenchymal cells in healthy and injured liver are discussed. Recent studies indicate the expression of megalin (LRP2) by hepatic stellate cells, myofibroblasts and Kupffer cells and hypothesize that LRP2 might represent another potential regulator of hepatic inflammatory processes. These observations provide the experimental framework for the systematic and dynamic analysis of the LDLR family during chronic liver injury and fibrogenesis.
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43
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Traub LM, Bonifacino JS. Cargo recognition in clathrin-mediated endocytosis. Cold Spring Harb Perspect Biol 2013; 5:a016790. [PMID: 24186068 DOI: 10.1101/cshperspect.a016790] [Citation(s) in RCA: 213] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The endosomal system is expansive and complex, characterized by swift morphological transitions, dynamic remodeling of membrane constituents, and intracellular positioning changes. To properly navigate this ever-altering membrane labyrinth, transmembrane protein cargoes typically require specific sorting signals that are decoded by components of protein coats. The best-characterized sorting process within the endosomal system is the rapid internalization of select transmembrane proteins within clathrin-coated vesicles. Endocytic signals consist of linear motifs, conformational determinants, or covalent modifications in the cytosolic domains of transmembrane cargo. These signals are interpreted by a diverse set of clathrin-associated sorting proteins (CLASPs) that translocate from the cytosol to the inner face of the plasma membrane. Signal recognition by CLASPs is highly cooperative, involving additional interactions with phospholipids, Arf GTPases, other CLASPs, and clathrin, and is regulated by large conformational changes and covalent modifications. Related sorting events occur at other endosomal sorting stations.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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44
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Shah M, Baterina OY, Taupin V, Farquhar MG. ARH directs megalin to the endocytic recycling compartment to regulate its proteolysis and gene expression. ACTA ACUST UNITED AC 2013; 202:113-27. [PMID: 23836931 PMCID: PMC3704979 DOI: 10.1083/jcb.201211110] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
ARH is required for the trafficking of megalin from early endosomes to the endocytic recycling compartment, where megalin undergoes intramembrane proteolysis, releasing a tail fragment that represses megalin transcription. Receptors internalized by endocytosis can return to the plasma membrane (PM) directly from early endosomes (EE; fast recycling) or they can traffic from EE to the endocytic recycling compartment (ERC) and recycle from there (slow recycling). How receptors are sorted for trafficking along these two pathways remains unclear. Here we show that autosomal recessive hypercholesterolemia (ARH) is required for trafficking of megalin, a member of the LDL receptor family, from EE to the ERC by coupling it to dynein; in the absence of ARH, megalin returns directly to the PM from EE via the connecdenn2/Rab35 fast recycling pathway. Binding of ARH to the endocytic adaptor AP-2 prevents fast recycling of megalin. ARH-mediated trafficking of megalin to the ERC is necessary for γ-secretase mediated cleavage of megalin and release of a tail fragment that mediates transcriptional repression. These results identify a novel mechanism for sorting receptors for trafficking to the ERC and link ERC trafficking to regulated intramembrane proteolysis (RIP) and expression of megalin.
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Affiliation(s)
- Mehul Shah
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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45
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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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46
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Canuel M, Sun X, Asselin MC, Paramithiotis E, Prat A, Seidah NG. Proprotein convertase subtilisin/kexin type 9 (PCSK9) can mediate degradation of the low density lipoprotein receptor-related protein 1 (LRP-1). PLoS One 2013; 8:e64145. [PMID: 23675525 PMCID: PMC3652815 DOI: 10.1371/journal.pone.0064145] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 04/08/2013] [Indexed: 02/07/2023] Open
Abstract
Elevated LDL-cholesterol (LDLc) levels are a major risk factor for cardiovascular disease and atherosclerosis. LDLc is cleared from circulation by the LDL receptor (LDLR). Proprotein convertase subtilisin/kexin 9 (PCSK9) enhances the degradation of the LDLR in endosomes/lysosomes, resulting in increased circulating LDLc. PCSK9 can also mediate the degradation of LDLR lacking its cytosolic tail, suggesting the presence of as yet undefined lysosomal-targeting factor(s). Herein, we confirm this, and also eliminate a role for the transmembrane-domain of the LDLR in mediating its PCSK9-induced internalization and degradation. Recent findings from our laboratory also suggest a role for PCSK9 in enhancing tumor metastasis. We show herein that while the LDLR is insensitive to PCSK9 in murine B16F1 melanoma cells, PCSK9 is able to induce degradation of the low density lipoprotein receptor-related protein 1 (LRP-1), suggesting distinct targeting mechanisms for these receptors. Furthermore, PCSK9 is still capable of acting upon the LDLR in CHO 13-5-1 cells lacking LRP-1. Conversely, PCSK9 also acts on LRP-1 in the absence of the LDLR in CHO-A7 cells, where re-introduction of the LDLR leads to reduced PCSK9-mediated degradation of LRP-1. Thus, while PCSK9 is capable of inducing degradation of LRP-1, the latter is not an essential factor for LDLR regulation, but the LDLR effectively competes with LRP-1 for PCSK9 activity. Identification of PCSK9 targets should allow a better understanding of the consequences of PCSK9 inhibition for lowering LDLc and tumor metastasis.
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Affiliation(s)
- Maryssa Canuel
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, affiliated to the University of Montreal, Montreal, Quebec, Canada
| | - Xiaowei Sun
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, affiliated to the University of Montreal, Montreal, Quebec, Canada
| | - Marie-Claude Asselin
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, affiliated to the University of Montreal, Montreal, Quebec, Canada
| | | | - Annik Prat
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, affiliated to the University of Montreal, Montreal, Quebec, Canada
| | - Nabil G. Seidah
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, affiliated to the University of Montreal, Montreal, Quebec, Canada
- * E-mail:
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47
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Cayo MA, Cai J, DeLaForest A, Noto FK, Nagaoka M, Clark BS, Collery RF, Si-Tayeb K, Duncan SA. JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia. Hepatology 2012; 56:2163-71. [PMID: 22653811 PMCID: PMC3900031 DOI: 10.1002/hep.25871] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 05/24/2012] [Indexed: 12/14/2022]
Abstract
UNLABELLED Elevated levels of low-density lipoprotein cholesterol (LDL-C) in plasma are a major contributor to cardiovascular disease, which is the leading cause of death worldwide. Genome-wide association studies (GWAS) have identified 95 loci that associate with control of lipid/cholesterol metabolism. Although GWAS results are highly provocative, direct analyses of the contribution of specific allelic variations in regulating LDL-C has been challenging due to the difficulty in accessing appropriate cells from affected patients. The primary cell type responsible for controlling cholesterol and lipid flux is the hepatocyte. Recently, we have shown that cells with hepatocyte characteristics can be generated from human induced pluripotent stem cells (iPSCs). This finding raises the possibility of using patient-specific iPSC-derived hepatocytes to study the functional contribution of GWAS loci in regulating lipid metabolism. To test the validity of this approach, we produced iPSCs from JD a patient with mutations in the low-density lipoprotein receptor (LDLR) gene that result in familial hypercholesterolemia (FH). We demonstrate that (1) hepatocytes can be efficiently generated from FH iPSCs; (2) in contrast to control cells, FH iPSC-derived hepatocytes are deficient in LDL-C uptake; (3) control but not FH iPSC-derived hepatocytes increase LDL uptake in response to lovastatin; and (4) FH iPSC-derived hepatocytes display a marked elevation in secretion of lipidated apolipoprotein B-100. CONCLUSION Cumulatively, these findings demonstrate that FH iPSC-derived hepatocytes recapitulate the complex pathophysiology of FH in culture. These results also establish that patient-specific iPSC-derived hepatocytes could be used to definitively determine the functional contribution of allelic variation in regulating lipid and cholesterol metabolism and could potentially provide a platform for the identification of novel treatments of cardiovascular disease. (HEPATOLOGY 2012).
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Abstract
Endocytosis is essential for the entry of many viruses into cells. The primate lentiviruses [human immunodeficiency virus (HIV) 1 and 2, and the simian immunodeficiency viruses (SIVs)], however, use endocytosis in other aspects of their life cycles. Here, the authors describe the ways in which the endocytic pathway is used by HIV and SIV and discuss the mechanisms through which endocytosis may contribute to the pathogenic properties of these viruses.
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Affiliation(s)
- M Marsh
- The Medical Research Council Laboratory for Molecular Cell Biology and Dept of Biochemistry, University College London, Gower Street, London, UK WCIE 6BT, USA
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49
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Fahed AC, Bitar FF, Khalaf RI, Moubarak EM, Azar ST, Nemer GM. The Lebanese allele at the LDLR in normocholesterolemic people merits reconsideration of genotype phenotype correlations in familial hypercholesterolemia. Endocrine 2012; 42:445-8. [PMID: 22487947 DOI: 10.1007/s12020-012-9669-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 03/31/2012] [Indexed: 11/26/2022]
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50
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Atomic structure of the autosomal recessive hypercholesterolemia phosphotyrosine-binding domain in complex with the LDL-receptor tail. Proc Natl Acad Sci U S A 2012; 109:6916-21. [PMID: 22509010 DOI: 10.1073/pnas.1114128109] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hypercholesterolemia, high serum cholesterol in the form of LDL, is a major risk factor for atherosclerosis. LDL is mostly degraded in the liver after its cellular internalization with the LDL receptor (LDLR). This clathrin-mediated endocytosis depends on the protein autosomal recessive hypercholesterolemia (ARH), which binds the LDLR cytoplasmic tail. Mutations in either the LDLR tail or in ARH lead to hypercholesterolemia and premature atherosclerosis. Despite the significance of this interaction for cholesterol homeostasis, no structure of either ARH or the LDLR tail is available to determine its molecular basis. We report the crystal structure at 1.37-Å resolution of the phosphotyrosine-binding (PTB) domain of ARH in complex with an LDLR tail peptide containing the FxNPxY(0) internalization signal. Surprisingly, ARH interacts with a longer portion of the tail than previously recognized, which extends to I(-7)xF(-5)xNPxY(0)QK(+2). The LDLR tail assumes a unique "Hook"-like structure with a double β-turn conformation, which is accommodated in distinctive ARH structural determinants (i.e., an extended backbone hydrogen-bonding platform, three hydrophobic helical grooves, and a hydrophobic pocket for Y(0)). This unique complementarity differs significantly in related PTB proteins and may account for the unique physiological role of these partners in the hepatic uptake of cholesterol LDL. Moreover, the unusual hydrophobic pocket for Y(0) explains the distinctive ability of ARH to internalize proteins containing either FxNPxY(0) or FxNPxF(0) sequences. Biophysical measurements reveal how mutations associated with hypercholesterolemia destabilize ARH and its complex with LDLR and illuminate LDL internalization defects seen in patients.
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