1
|
Trastulla L, Dolgalev G, Moser S, Jiménez-Barrón LT, Andlauer TFM, von Scheidt M, Budde M, Heilbronner U, Papiol S, Teumer A, Homuth G, Völzke H, Dörr M, Falkai P, Schulze TG, Gagneur J, Iorio F, Müller-Myhsok B, Schunkert H, Ziller MJ. Distinct genetic liability profiles define clinically relevant patient strata across common diseases. Nat Commun 2024; 15:5534. [PMID: 38951512 PMCID: PMC11217418 DOI: 10.1038/s41467-024-49338-2] [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: 02/20/2024] [Accepted: 05/31/2024] [Indexed: 07/03/2024] Open
Abstract
Stratified medicine holds great promise to tailor treatment to the needs of individual patients. While genetics holds great potential to aid patient stratification, it remains a major challenge to operationalize complex genetic risk factor profiles to deconstruct clinical heterogeneity. Contemporary approaches to this problem rely on polygenic risk scores (PRS), which provide only limited clinical utility and lack a clear biological foundation. To overcome these limitations, we develop the CASTom-iGEx approach to stratify individuals based on the aggregated impact of their genetic risk factor profiles on tissue specific gene expression levels. The paradigmatic application of this approach to coronary artery disease or schizophrenia patient cohorts identified diverse strata or biotypes. These biotypes are characterized by distinct endophenotype profiles as well as clinical parameters and are fundamentally distinct from PRS based groupings. In stark contrast to the latter, the CASTom-iGEx strategy discovers biologically meaningful and clinically actionable patient subgroups, where complex genetic liabilities are not randomly distributed across individuals but rather converge onto distinct disease relevant biological processes. These results support the notion of different patient biotypes characterized by partially distinct pathomechanisms. Thus, the universally applicable approach presented here has the potential to constitute an important component of future personalized medicine paradigms.
Collapse
Affiliation(s)
- Lucia Trastulla
- Max Planck Institute of Psychiatry, Munich, Germany
- Technische Universität München Medical Graduate Center Experimental Medicine, Munich, Germany
- Human Technopole, Milan, Italy
- Department of Psychiatry, University of Münster, Münster, Germany
| | - Georgii Dolgalev
- Department of Psychiatry, University of Münster, Münster, Germany
| | - Sylvain Moser
- Max Planck Institute of Psychiatry, Munich, Germany
- Technische Universität München Medical Graduate Center Experimental Medicine, Munich, Germany
- International Max Planck Research School for Translational Psychiatry (IMPRS-TP), Munich, Germany
| | - Laura T Jiménez-Barrón
- Max Planck Institute of Psychiatry, Munich, Germany
- International Max Planck Research School for Translational Psychiatry (IMPRS-TP), Munich, Germany
| | - Till F M Andlauer
- Max Planck Institute of Psychiatry, Munich, Germany
- Department of Neurology, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, Germany
| | - Moritz von Scheidt
- Klinik für Herz-und Kreislauferkrankungen, Deutsches Herzzentrum München, Technical University Munich, Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Monika Budde
- Institute of Psychiatric Phenomics and Genomics (IPPG), LMU University Hospital, LMU Munich, Munich, 80336, Germany
| | - Urs Heilbronner
- Institute of Psychiatric Phenomics and Genomics (IPPG), LMU University Hospital, LMU Munich, Munich, 80336, Germany
| | - Sergi Papiol
- Max Planck Institute of Psychiatry, Munich, Germany
- Institute of Psychiatric Phenomics and Genomics (IPPG), LMU University Hospital, LMU Munich, Munich, 80336, Germany
| | - Alexander Teumer
- German Center for Cardiovascular Research (DZHK), Partner Site Greifswald, Greifswald, Germany
- Department of Psychiatry and Psychotherapy, University Medicine Greifswald, Greifswald, Germany
| | - Georg Homuth
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Henry Völzke
- German Center for Cardiovascular Research (DZHK), Partner Site Greifswald, Greifswald, Germany
- Institute of Community Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Marcus Dörr
- German Center for Cardiovascular Research (DZHK), Partner Site Greifswald, Greifswald, Germany
- Department of Internal Medicine B, University Medicine Greifswald, Greifswald, Germany
| | - Peter Falkai
- Max Planck Institute of Psychiatry, Munich, Germany
- Department of Psychiatry and Psychotherapy, University Hospital, LMU Munich, Munich, 80336, Germany
| | - Thomas G Schulze
- Institute of Psychiatric Phenomics and Genomics (IPPG), LMU University Hospital, LMU Munich, Munich, 80336, Germany
- Department of Psychiatry and Behavioral Sciences, SUNY Upstate Medical University, Syracuse, NY, USA
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Julien Gagneur
- School of Computation, Information and Technology, Technical University of Munich, Garching, Germany
- Institute of Human Genetics, School of Medicine and Health, Technical University of Munich, Munich, Germany
- Computational Health Center, Helmholtz Center Munich, Neuherberg, Germany
| | | | - Bertram Müller-Myhsok
- Max Planck Institute of Psychiatry, Munich, Germany
- Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Heribert Schunkert
- Klinik für Herz-und Kreislauferkrankungen, Deutsches Herzzentrum München, Technical University Munich, Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Michael J Ziller
- Max Planck Institute of Psychiatry, Munich, Germany.
- Department of Psychiatry, University of Münster, Münster, Germany.
- Center for Soft Nanoscience, University of Münster, Münster, Germany.
| |
Collapse
|
2
|
Wu C, Ji C, Qian D, Li C, Chen J, Zhang J, Bao G, Xu G, Cui Z. Contribution of ApoB-100/SORT1-Mediated Immune Microenvironment in Regulating Oxidative Stress, Inflammation, and Ferroptosis After Spinal Cord Injury. Mol Neurobiol 2024:10.1007/s12035-024-03956-5. [PMID: 38337131 DOI: 10.1007/s12035-024-03956-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 01/12/2024] [Indexed: 02/12/2024]
Abstract
This study aims to explore the impacts of ApoB-100/SORT1-mediated immune microenvironment during acute spinal cord injury (SCI), and to investigate the potential mechanism. CB57BL/6 mice underwent moderate thoracic contusion injury to establish the SCI animal model, and received ApoB-100 lentivirus injection to interfere ApoB-100 level. Functional recovery was assessed using the Basso, Beattie, and Bresnahan (BBB) score and footprint analysis. Transmission electron microscopy was applied to observe the ultrastructure of the injured spinal cord tissue. Hematoxylin-eosin (HE) staining and Perls staining were conducted to assess histological changes and iron deposition. Biochemical factor and cytokines were detected using their commercial kits. M1/M2 macrophage markers were detected by immunofluorescence assay in vivo and by flow cytometry in vitro. HT22 neurons were simulated by lipopolysaccharide (LPS), followed by incubation with polarized macrophage medium to simulate the immune microenvironment of injured spinal cord in vitro. The local immune microenvironment is changed in SCI mice, accompanied with the occurrence of oxidative stress and the elevation of both M1 and M2 macrophages. Knockdown of ApoB-100 ameliorates oxidative stress and lipid disorder, and inhibits inflammation and ferroptosis in SCI mice. Importantly, knockdown of ApoB-100 can partly restrict M1 macrophages but does not change M2 macrophage proportion in SCI mice. Further, M1 macrophages are observed to attenuate the inflammatory response, oxidative stress, and ferroptosis levels of LPS-induced HT22 cells, which is further strengthened by SORT1 knockdown. Blockage of ApoB-100/SORT1-mediated immune microenvironment plays a protective role against SCI via inhibiting oxidative stress, inflammation, lipid disorders, and ferroptosis, providing novel insights of the targeted therapy of SCI.
Collapse
Affiliation(s)
- Chunshuai Wu
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China
| | - Chunyan Ji
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China
| | - Dandan Qian
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China
| | - Chaochen Li
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China
| | - Jiajia Chen
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
| | - Jinlong Zhang
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
| | - Guofeng Bao
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China
| | - Guanhua Xu
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China.
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China.
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China.
| | - Zhiming Cui
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong First People's Hospital, Nantong University, 666 Shengli Road, Nantong, 226000, Jiangsu Province, China.
- Research Institute for Spine and Spinal Cord Disease of Nantong University, Nantong, 226000, China.
- Key Laboratory for Restoration Mechanism and Clinical Translation of Spinal Cord Injury, Nantong, 226000, China.
| |
Collapse
|
3
|
Wang H, Nikain C, Amengual J, La Forest M, Yu Y, Wang MC, Watts R, Lehner R, Qiu Y, Cai M, Kurland IJ, Goldberg IJ, Rajan S, Hussain MM, Brodsky JL, Fisher EA. FITM2 deficiency results in ER lipid accumulation, ER stress, reduced apolipoprotein B lipidation, and VLDL triglyceride secretion in vitro and in mouse liver. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.05.570183. [PMID: 38106013 PMCID: PMC10723279 DOI: 10.1101/2023.12.05.570183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Objectives Triglyceride (TG) association with apolipoprotein B100 (apoB100) serves to form very low density lipoproteins (VLDL) in the liver. The repertoire of factors that facilitate this association is incompletely defined. FITM2, an integral endoplasmic reticulum (ER) protein, was originally discovered as a factor participating in cytoplasmic lipid droplets (LDs) in tissues that do not form VLDL. We hypothesized that in the liver, in addition to promoting cytosolic LD formation, FITM2 would also transfer TG from its site of synthesis in the ER membrane to nascent VLDL particles within the ER lumen. Methods Experiments were conducted using a rat hepatic cell line (McArdle-RH7777, or McA cells), an established model of mammalian lipoprotein metabolism, and mice. FITM2 expression was reduced using siRNA in cells and by liver specific cre-recombinase mediated deletion of the Fitm2 gene in mice. Effects of FITM2 deficiency on VLDL assembly and secretion in vitro and in vivo were measured by multiple methods, including density gradient ultracentrifugation, chromatography, mass spectrometry, simulated Raman spectroscopy (SRS) microscopy, sub-cellular fractionation, immunoprecipitation, immunofluorescence, and electron microscopy. Main findings 1) FITM2-deficient hepatic cells in vitro and in vivo secrete TG-depleted VLDL particles, but the number of particles is unchanged compared to controls; 2) FITM2 deficiency in mice on a high fat diet (HFD) results in decreased plasma TG levels. The number of apoB100-containing lipoproteins remains similar, but shift from VLDL to LDL density; 3) Both in vitro and in vivo , when TG synthesis is stimulated and FITM2 is deficient, TG accumulates in the ER, and despite its availability this pool is unable to fully lipidate apoB100 particles; 4) FITM2 deficiency disrupts ER morphology and results in ER stress. Principal conclusions The results suggest that FITM2 contributes to VLDL lipidation, especially when newly synthesized hepatic TG is in abundance. In addition to its fundamental importance in VLDL assembly, the results also suggest that under dysmetabolic conditions, FITM2 may be a limiting factor that ultimately contributes to non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH).
Collapse
|
4
|
Lin H, Wang L, Liu Z, Long K, Kong M, Ye D, Chen X, Wang K, Wu KKL, Fan M, Song E, Wang C, Hoo RLC, Hui X, Hallenborg P, Piao H, Xu A, Cheng KKY. Hepatic MDM2 Causes Metabolic Associated Fatty Liver Disease by Blocking Triglyceride-VLDL Secretion via ApoB Degradation. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2200742. [PMID: 35524581 PMCID: PMC9284139 DOI: 10.1002/advs.202200742] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/15/2022] [Indexed: 05/06/2023]
Abstract
Dysfunctional triglyceride-very low-density lipoprotein (TG-VLDL) metabolism is linked to metabolic-associated fatty liver disease (MAFLD); however, the underlying cause remains unclear. The study shows that hepatic E3 ubiquitin ligase murine double minute 2 (MDM2) controls MAFLD by blocking TG-VLDL secretion. A remarkable upregulation of MDM2 is observed in the livers of human and mouse models with different levels of severity of MAFLD. Hepatocyte-specific deletion of MDM2 protects against high-fat high-cholesterol diet-induced hepatic steatosis and inflammation, accompanied by a significant elevation in TG-VLDL secretion. As an E3 ubiquitin ligase, MDM2 targets apolipoprotein B (ApoB) for proteasomal degradation through direct protein-protein interaction, which leads to reduced TG-VLDL secretion in hepatocytes. Pharmacological blockage of the MDM2-ApoB interaction alleviates dietary-induced hepatic steatohepatitis and fibrosis by inducing hepatic ApoB expression and subsequent TG-VLDL secretion. The effect of MDM2 on VLDL metabolism is p53-independent. Collectively, these findings suggest that MDM2 acts as a negative regulator of hepatic ApoB levels and TG-VLDL secretion in MAFLD. Inhibition of the MDM2-ApoB interaction may represent a potential therapeutic approach for MAFLD treatment.
Collapse
Affiliation(s)
- Huige Lin
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| | - Lin Wang
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
- The State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongPokfulamHong Kong
- Department of MedicineThe University of Hong KongPokfulamHong Kong
| | - Zhuohao Liu
- The State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongPokfulamHong Kong
- Department of MedicineThe University of Hong KongPokfulamHong Kong
- Department of NeurosurgeryShenzhen HospitalSouthern Medical UniversityShenzhen518000P. R. China
| | - Kekao Long
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| | - Mengjie Kong
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| | - Dewei Ye
- Key Laboratory of Glucolipid Metabolic Diseases of the Ministry of EducationGuangdong Pharmaceutical UniversityGuangzhou510000P. R. China
| | - Xi Chen
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| | - Kai Wang
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| | - Kelvin KL Wu
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| | - Mengqi Fan
- Key Laboratory of Glucolipid Metabolic Diseases of the Ministry of EducationGuangdong Pharmaceutical UniversityGuangzhou510000P. R. China
| | - Erfei Song
- Department of Metabolic and Bariatric SurgeryThe First Affiliated Hospital of Jinan UniversityGuangzhou510000P. R. China
| | - Cunchuan Wang
- Department of Metabolic and Bariatric SurgeryThe First Affiliated Hospital of Jinan UniversityGuangzhou510000P. R. China
| | - Ruby LC Hoo
- The State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongPokfulamHong Kong
- Department of Pharmacology and PharmacyThe University of Hong KongPokfulamHong Kong
| | - Xiaoyan Hui
- The State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongPokfulamHong Kong
- Department of MedicineThe University of Hong KongPokfulamHong Kong
| | - Philip Hallenborg
- Department of Biochemistry and Molecular BiologyUniversity of Southern DenmarkSouthern Denmark5230Denmark
| | - Hailong Piao
- Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian116000P. R. China
| | - Aimin Xu
- The State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongPokfulamHong Kong
- Department of MedicineThe University of Hong KongPokfulamHong Kong
- Department of Pharmacology and PharmacyThe University of Hong KongPokfulamHong Kong
| | - Kenneth KY Cheng
- Department of Health Technology and InformaticsThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong
| |
Collapse
|
5
|
Yang W, Wang S, Loor JJ, Jiang Q, Gao C, Yang M, Tian Y, Fan W, Zhao Y, Zhang B, Xu C. Role of sortilin 1 (SORT1) on lipid metabolism in bovine liver. J Dairy Sci 2022; 105:5420-5434. [DOI: 10.3168/jds.2021-21607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Accepted: 02/27/2022] [Indexed: 11/19/2022]
|
6
|
Kumari D, Fisher EA, Brodsky JL. Hsp40s play distinct roles during the initial stages of apolipoprotein B biogenesis. Mol Biol Cell 2021; 33:ar15. [PMID: 34910568 PMCID: PMC9236142 DOI: 10.1091/mbc.e21-09-0436] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Apolipoprotein B (ApoB) is the primary component of atherogenic lipoproteins, which transport serum fats and cholesterol. Therefore, elevated levels of circulating ApoB are a primary risk factor for cardiovascular disease. During ApoB biosynthesis in the liver and small intestine under nutrient-rich conditions, ApoB cotranslationally translocates into the endoplasmic reticulum (ER) and is lipidated and ultimately secreted. Under lipid-poor conditions, ApoB is targeted for ER Associated Degradation (ERAD). Although prior work identified select chaperones that regulate ApoB biogenesis, the contributions of cytoplasmic Hsp40s are undefined. To this end, we screened ApoB-expressing yeast and determined that a class A ER-associated Hsp40, Ydj1, associates with and facilitates the ERAD of ApoB. Consistent with these results, a homologous Hsp40, DNAJA1, functioned similarly in rat hepatoma cells. DNAJA1 deficient cells also secreted hyperlipidated lipoproteins, in accordance with attenuated ERAD. In contrast to the role of DNAJA1 during ERAD, DNAJB1-a class B Hsp40-helped stabilize ApoB. Depletion of DNAJA1 and DNAJB1 also led to opposing effects on ApoB ubiquitination. These data represent the first example in which different Hsp40s exhibit disparate effects during regulated protein biogenesis in the ER, and highlight distinct roles that chaperones can play on a single ERAD substrate.
Collapse
Affiliation(s)
- Deepa Kumari
- Department of Biological Sciences, A320 Langley Hall, Fifth & Ruskin Ave, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Edward A Fisher
- Department of Medicine, Leon H. Charney Division of Cardiology, Cardiovascular Research Center, New York University Grossman School of Medicine, New York, United States
| | - Jeffrey L Brodsky
- Department of Biological Sciences, A320 Langley Hall, Fifth & Ruskin Ave, University of Pittsburgh, Pittsburgh, PA 15260 USA
| |
Collapse
|
7
|
Huang D, Xu B, Liu L, Wu L, Zhu Y, Ghanbarpour A, Wang Y, Chen FJ, Lyu J, Hu Y, Kang Y, Zhou W, Wang X, Ding W, Li X, Jiang Z, Chen J, Zhang X, Zhou H, Li JZ, Guo C, Zheng W, Zhang X, Li P, Melia T, Reinisch K, Chen XW. TMEM41B acts as an ER scramblase required for lipoprotein biogenesis and lipid homeostasis. Cell Metab 2021; 33:1655-1670.e8. [PMID: 34015269 DOI: 10.1016/j.cmet.2021.05.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/06/2021] [Accepted: 05/05/2021] [Indexed: 02/06/2023]
Abstract
How amphipathic phospholipids are shuttled between the membrane bilayer remains an essential but elusive process, particularly at the endoplasmic reticulum (ER). One prominent phospholipid shuttling process concerns the biogenesis of APOB-containing lipoproteins within the ER lumen, which may require bulk trans-bilayer movement of phospholipids from the cytoplasmic leaflet of the ER bilayer. Here, we show that TMEM41B, present in the lipoprotein export machinery, encodes a previously conceptualized ER lipid scramblase mediating trans-bilayer shuttling of bulk phospholipids. Loss of hepatic TMEM41B eliminates plasma lipids, due to complete absence of mature lipoproteins within the ER, but paradoxically also activates lipid production. Mechanistically, scramblase deficiency triggers unique ER morphological changes and unsuppressed activation of SREBPs, which potently promotes lipid synthesis despite stalled secretion. Together, this response induces full-blown nonalcoholic hepatosteatosis in the TMEM41B-deficient mice within weeks. Collectively, our data uncovered a fundamental mechanism safe-guarding ER function and integrity, dysfunction of which disrupts lipid homeostasis.
Collapse
Affiliation(s)
- Dong Huang
- State Key Laboratory of Membrane Biology, Peking University, Beijing 100871, China; Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Bolin Xu
- State Key Laboratory of Membrane Biology, Peking University, Beijing 100871, China; Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Lu Liu
- State Key Laboratory of Membrane Biology, Peking University, Beijing 100871, China; Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Lingzhi Wu
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Yuangang Zhu
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Alireza Ghanbarpour
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Yawei Wang
- Center for Life Sciences, Peking University, Beijing 100871, China
| | - Feng-Jung Chen
- Institute of Metabolism and Integrative Biology, Fudan University, Shanghai 200438, China
| | - Jia Lyu
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Yating Hu
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Yunlu Kang
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Wenjing Zhou
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Xiao Wang
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Wanqiu Ding
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Xin Li
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Zhaodi Jiang
- National Institute of Biological Sciences, Tsinghua University, Beijing 100086, China
| | - Jizheng Chen
- Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510503, China
| | - Xu Zhang
- The Key Laboratory of Rare Metabolic Disease, Department of Biochemistry and Molecular Biology, The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Hongwen Zhou
- Department of Endocrinology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - John Zhong Li
- The Key Laboratory of Rare Metabolic Disease, Department of Biochemistry and Molecular Biology, The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Chunguang Guo
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Wen Zheng
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Xiuqin Zhang
- Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China
| | - Peng Li
- Institute of Metabolism and Integrative Biology, Fudan University, Shanghai 200438, China; School of Life Sciences, Tsinghua University, Beijing 100086, China
| | - Thomas Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Karin Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Xiao-Wei Chen
- State Key Laboratory of Membrane Biology, Peking University, Beijing 100871, China; Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100871, China; Center for Life Sciences, Peking University, Beijing 100871, China.
| |
Collapse
|
8
|
Receptor-Mediated ER Export of Lipoproteins Controls Lipid Homeostasis in Mice and Humans. Cell Metab 2021; 33:350-366.e7. [PMID: 33186557 DOI: 10.1016/j.cmet.2020.10.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 08/24/2020] [Accepted: 10/20/2020] [Indexed: 12/14/2022]
Abstract
Efficient delivery of specific cargos in vivo poses a major challenge to the secretory pathway, which shuttles products encoded by ∼30% of the genome. Newly synthesized protein and lipid cargos embark on the secretory pathway via COPII-coated vesicles, assembled by the GTPase SAR1 on the endoplasmic reticulum (ER), but how lipid-carrying lipoproteins are distinguished from the general protein cargos in the ER and selectively secreted has not been clear. Here, we show that this process is quantitatively governed by the GTPase SAR1B and SURF4, a high-efficiency cargo receptor. While both genes are implicated in lipid regulation in humans, hepatic inactivation of either mouse Sar1b or Surf4 selectively depletes plasma lipids to near-zero and protects the mice from atherosclerosis. These findings show that the pairing between SURF4 and SAR1B synergistically operates a specialized, dosage-sensitive transport program for circulating lipids, while further suggesting a potential translation to treat atherosclerosis and related cardio-metabolic diseases.
Collapse
|
9
|
Duwaerts CC, Maiers JL. ER Disposal Pathways in Chronic Liver Disease: Protective, Pathogenic, and Potential Therapeutic Targets. Front Mol Biosci 2021; 8:804097. [PMID: 35174209 PMCID: PMC8841999 DOI: 10.3389/fmolb.2021.804097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 11/18/2021] [Indexed: 11/13/2022] Open
Abstract
The endoplasmic reticulum is a central player in liver pathophysiology. Chronic injury to the ER through increased lipid content, alcohol metabolism, or accumulation of misfolded proteins causes ER stress, dysregulated hepatocyte function, inflammation, and worsened disease pathogenesis. A key adaptation of the ER to resolve stress is the removal of excess or misfolded proteins. Degradation of intra-luminal or ER membrane proteins occurs through distinct mechanisms that include ER-associated Degradation (ERAD) and ER-to-lysosome-associated degradation (ERLAD), which includes macro-ER-phagy, micro-ER-phagy, and Atg8/LC-3-dependent vesicular delivery. All three of these processes are critical for removing misfolded or unfolded protein aggregates, and re-establishing ER homeostasis following expansion/stress, which is critical for liver function and adaptation to injury. Despite playing a key role in resolving ER stress, the contribution of these degradative processes to liver physiology and pathophysiology is understudied. Analysis of publicly available datasets from diseased livers revealed that numerous genes involved in ER-related degradative pathways are dysregulated; however, their roles and regulation in disease progression are not well defined. Here we discuss the dynamic regulation of ER-related protein disposal pathways in chronic liver disease and cell-type specific roles, as well as potentially targetable mechanisms for treatment of chronic liver disease.
Collapse
Affiliation(s)
- Caroline C Duwaerts
- Department of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Jessica L Maiers
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States
| |
Collapse
|
10
|
Oikonomou C, Hendershot LM. Disposing of misfolded ER proteins: A troubled substrate's way out of the ER. Mol Cell Endocrinol 2020; 500:110630. [PMID: 31669350 PMCID: PMC6911830 DOI: 10.1016/j.mce.2019.110630] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/19/2019] [Accepted: 10/20/2019] [Indexed: 12/12/2022]
Abstract
Secreted, plasma membrane, and resident proteins of the secretory pathway are synthesized in the endoplasmic reticulum (ER) where they undergo post-translational modifications, oxidative folding, and subunit assembly in tightly monitored processes. An ER quality control (ERQC) system oversees protein maturation and ensures that only those reaching their native state will continue trafficking into the secretory pathway to reach their final destinations. Those that fail must be recognized and eliminated to maintain ER homeostasis. Two cellular mechanisms have been identified to rid the ER of terminally unfolded, misfolded, and aggregated proteins. ER-associated degradation (ERAD) was discovered nearly 30 years ago and entails the identification of improperly matured secretory pathway proteins and their retrotranslocation to the cytosol for degradation by the ubiquitin-proteasome system. ER-phagy has been more recently described and caters to larger, more complex proteins and protein aggregates that are not readily handled by ERAD. This pathway has unique upstream components and relies on the same downstream effectors of autophagy used in other cellular processes to deliver clients to lysosomes for degradation. In this review, we describe the main elements of ERQC, ERAD, and ER-phagy and focus on recent advances in these fields.
Collapse
Affiliation(s)
- Christina Oikonomou
- St. Jude Children's Research Hospital, Memphis, TN, 38104, USA; The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Linda M Hendershot
- St. Jude Children's Research Hospital, Memphis, TN, 38104, USA; The University of Tennessee Health Science Center, Memphis, TN, USA.
| |
Collapse
|
11
|
Chen L, Chen XW, Huang X, Song BL, Wang Y, Wang Y. Regulation of glucose and lipid metabolism in health and disease. SCIENCE CHINA-LIFE SCIENCES 2019; 62:1420-1458. [PMID: 31686320 DOI: 10.1007/s11427-019-1563-3] [Citation(s) in RCA: 130] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 10/15/2019] [Indexed: 02/08/2023]
Abstract
Glucose and fatty acids are the major sources of energy for human body. Cholesterol, the most abundant sterol in mammals, is a key component of cell membranes although it does not generate ATP. The metabolisms of glucose, fatty acids and cholesterol are often intertwined and regulated. For example, glucose can be converted to fatty acids and cholesterol through de novo lipid biosynthesis pathways. Excessive lipids are secreted in lipoproteins or stored in lipid droplets. The metabolites of glucose and lipids are dynamically transported intercellularly and intracellularly, and then converted to other molecules in specific compartments. The disorders of glucose and lipid metabolism result in severe diseases including cardiovascular disease, diabetes and fatty liver. This review summarizes the major metabolic aspects of glucose and lipid, and their regulations in the context of physiology and diseases.
Collapse
Affiliation(s)
- Ligong Chen
- School of Pharmaceutical Sciences, Beijing Advanced Innovation Center for Structural Biology, Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Tsinghua University, Beijing, 100084, China.
| | - Xiao-Wei Chen
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Bao-Liang Song
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
| | - Yan Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
| | - Yiguo Wang
- MOE Key Laboratory of Bioinformatics, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
| |
Collapse
|
12
|
Doonan LM, Guerriero CJ, Preston GM, Buck TM, Khazanov N, Fisher EA, Senderowitz H, Brodsky JL. Hsp104 facilitates the endoplasmic-reticulum-associated degradation of disease-associated and aggregation-prone substrates. Protein Sci 2019; 28:1290-1306. [PMID: 31050848 DOI: 10.1002/pro.3636] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 04/29/2019] [Indexed: 12/20/2022]
Abstract
Misfolded proteins in the endoplasmic reticulum (ER) are selected for ER-associated degradation (ERAD). More than 60 disease-associated proteins are substrates for the ERAD pathway due to the presence of missense or nonsense mutations. In yeast, the Hsp104 molecular chaperone disaggregates detergent-insoluble ERAD substrates, but the spectrum of disease-associated ERAD substrates that may be aggregation prone is unknown. To determine if Hsp104 recognizes aggregation-prone ERAD substrates associated with human diseases, we developed yeast expression systems for a hydrophobic lipid-binding protein, apolipoprotein B (ApoB), along with a chimeric protein harboring a nucleotide-binding domain from the cystic fibrosis transmembrane conductance regulator (CFTR) into which disease-causing mutations were introduced. We discovered that Hsp104 facilitates the degradation of ER-associated ApoB as well as a truncated CFTR chimera in which a premature stop codon corresponds to a disease-causing mutation. Chimeras containing a wild-type version of the CFTR domain or a different mutation were stable and thus Hsp104 independent. We also discovered that the detergent solubility of the unstable chimera was lower than the stable chimeras, and Hsp104 helped retrotranslocate the unstable chimera from the ER, consistent with disaggregase activity. To determine why the truncated chimera was unstable, we next performed molecular dynamics simulations and noted significant unraveling of the CFTR nucleotide-binding domain. Because human cells lack Hsp104, these data indicate that an alternate disaggregase or mechanism facilitates the removal of aggregation-prone, disease-causing ERAD substrates in their native environments.
Collapse
Affiliation(s)
- Lynley M Doonan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - Christopher J Guerriero
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - G Michael Preston
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - Netaly Khazanov
- Department of Chemistry, Bar Ilan University, Ramat Gan, 5290002, Israel
| | - Edward A Fisher
- Division of Cardiology, Department of Medicine and Cell Biology, New York University, New York, New York, 10016
| | - Hanoch Senderowitz
- Department of Chemistry, Bar Ilan University, Ramat Gan, 5290002, Israel
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| |
Collapse
|
13
|
de Gaetano M, McEvoy C, Andrews D, Cacace A, Hunter J, Brennan E, Godson C. Specialized Pro-resolving Lipid Mediators: Modulation of Diabetes-Associated Cardio-, Reno-, and Retino-Vascular Complications. Front Pharmacol 2018; 9:1488. [PMID: 30618774 PMCID: PMC6305798 DOI: 10.3389/fphar.2018.01488] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 12/05/2018] [Indexed: 12/18/2022] Open
Abstract
Diabetes and its associated chronic complications present a healthcare challenge on a global scale. Despite improvements in the management of chronic complications of the micro-/macro-vasculature, their growing prevalence and incidence highlights the scale of the problem. It is currently estimated that diabetes affects 425 million people globally and it is anticipated that this figure will rise by 2025 to 700 million people. The vascular complications of diabetes including diabetes-associated atherosclerosis and kidney disease present a particular challenge. Diabetes is the leading cause of end stage renal disease, reflecting fibrosis leading to organ failure. Moreover, diabetes associated states of inflammation, neo-vascularization, apoptosis and hypercoagulability contribute to also exacerbate atherosclerosis, from the metabolic syndrome to advanced disease, plaque rupture and coronary thrombosis. Current therapeutic interventions focus on regulating blood glucose, glomerular and peripheral hypertension and can at best slow the progression of diabetes complications. Recently advanced knowledge of the pathogenesis underlying diabetes and associated complications revealed common mechanisms, including the inflammatory response, insulin resistance and hyperglycemia. The major role that inflammation plays in many chronic diseases has led to the development of new strategies aiming to promote the restoration of homeostasis through the "resolution of inflammation." These strategies aim to mimic the spontaneous activities of the 'specialized pro-resolving mediators' (SPMs), including endogenous molecules and their synthetic mimetics. This review aims to discuss the effect of SPMs [with particular attention to lipoxins (LXs) and resolvins (Rvs)] on inflammatory responses in a series of experimental models, as well as evidence from human studies, in the context of cardio- and reno-vascular diabetic complications, with a brief mention to diabetic retinopathy (DR). These data collectively support the hypothesis that endogenously generated SPMs or synthetic mimetics of their activities may represent lead molecules in a new discipline, namely the 'resolution pharmacology,' offering hope for new therapeutic strategies to prevent and treat, specifically, diabetes-associated atherosclerosis, nephropathy and retinopathy.
Collapse
Affiliation(s)
- Monica de Gaetano
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
| | - Caitriona McEvoy
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
- Renal Transplant Program, University Health Network, Toronto, ON, Canada
| | - Darrell Andrews
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
| | - Antonino Cacace
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
| | - Jonathan Hunter
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
| | - Eoin Brennan
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
| | - Catherine Godson
- UCD Diabetes Complications Research Centre, Conway Institute and UCD School of Medicine, University College Dublin, Dublin, Ireland
| |
Collapse
|
14
|
Zhang P, Csaki LS, Ronquillo E, Baufeld LJ, Lin JY, Gutierrez A, Dwyer JR, Brindley DN, Fong LG, Tontonoz P, Young SG, Reue K. Lipin 2/3 phosphatidic acid phosphatases maintain phospholipid homeostasis to regulate chylomicron synthesis. J Clin Invest 2018; 129:281-295. [PMID: 30507612 DOI: 10.1172/jci122595] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 10/09/2018] [Indexed: 12/31/2022] Open
Abstract
The lipin phosphatidic acid phosphatase (PAP) enzymes are required for triacylglycerol (TAG) synthesis from glycerol 3-phosphate in most mammalian tissues. The 3 lipin proteins (lipin 1, lipin 2, and lipin 3) each have PAP activity, but have distinct tissue distributions, with lipin 1 being the predominant PAP enzyme in many metabolic tissues. One exception is the small intestine, which is unique in expressing exclusively lipin 2 and lipin 3. TAG synthesis in small intestinal enterocytes utilizes 2-monoacylglycerol and does not require the PAP reaction, making the role of lipin proteins in enterocytes unclear. Enterocyte TAGs are stored transiently as cytosolic lipid droplets or incorporated into lipoproteins (chylomicrons) for secretion. We determined that lipin enzymes are critical for chylomicron biogenesis, through regulation of membrane phospholipid composition and association of apolipoprotein B48 with nascent chylomicron particles. Lipin 2/3 deficiency caused phosphatidic acid accumulation and mammalian target of rapamycin complex 1 (mTORC1) activation, which were associated with enhanced protein levels of a key phospholipid biosynthetic enzyme (CTP:phosphocholine cytidylyltransferase α) and altered membrane phospholipid composition. Impaired chylomicron synthesis in lipin 2/3 deficiency could be rescued by normalizing phospholipid synthesis levels. These data implicate lipin 2/3 as a control point for enterocyte phospholipid homeostasis and chylomicron biogenesis.
Collapse
Affiliation(s)
- Peixiang Zhang
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Lauren S Csaki
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Emilio Ronquillo
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Lynn J Baufeld
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Jason Y Lin
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Alexis Gutierrez
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Jennifer R Dwyer
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - David N Brindley
- Signal Transduction Research Group, Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Loren G Fong
- Department of Medicine, Division of Cardiology, and
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.,Molecular Biology Institute, UCLA, Los Angeles, California, USA
| | - Stephen G Young
- Department of Medicine, Division of Cardiology, and.,Molecular Biology Institute, UCLA, Los Angeles, California, USA
| | - Karen Reue
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.,Molecular Biology Institute, UCLA, Los Angeles, California, USA
| |
Collapse
|
15
|
Glaeser K, Urban M, Fenech E, Voloshanenko O, Kranz D, Lari F, Christianson JC, Boutros M. ERAD-dependent control of the Wnt secretory factor Evi. EMBO J 2018; 37:embj.201797311. [PMID: 29378775 PMCID: PMC5813261 DOI: 10.15252/embj.201797311] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 12/01/2017] [Accepted: 01/02/2018] [Indexed: 12/21/2022] Open
Abstract
Active regulation of protein abundance is an essential strategy to modulate cellular signaling pathways. Within the Wnt signaling cascade, regulated degradation of β-catenin by the ubiquitin-proteasome system (UPS) affects the outcome of canonical Wnt signaling. Here, we found that abundance of the Wnt cargo receptor Evi (Wls/GPR177), which is required for Wnt protein secretion, is also regulated by the UPS through endoplasmic reticulum (ER)-associated degradation (ERAD). In the absence of Wnt ligands, Evi is ubiquitinated and targeted for ERAD in a VCP-dependent manner. Ubiquitination of Evi involves the E2-conjugating enzyme UBE2J2 and the E3-ligase CGRRF1. Furthermore, we show that a triaging complex of Porcn and VCP determines whether Evi enters the secretory or the ERAD pathway. In this way, ERAD-dependent control of Evi availability impacts the scale of Wnt protein secretion by adjusting the amount of Evi to meet the requirement of Wnt protein export. As Wnt and Evi protein levels are often dysregulated in cancer, targeting regulatory ERAD components might be a useful approach for therapeutic interventions.
Collapse
Affiliation(s)
- Kathrin Glaeser
- Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ) and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
| | - Manuela Urban
- Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ) and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
| | - Emma Fenech
- Ludwig Institute for Cancer Research, University of Oxford, Oxford, UK
| | - Oksana Voloshanenko
- Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ) and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
| | - Dominique Kranz
- Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ) and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
| | - Federica Lari
- Ludwig Institute for Cancer Research, University of Oxford, Oxford, UK
| | | | - Michael Boutros
- Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ) and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
| |
Collapse
|
16
|
Amengual J, Guo L, Strong A, Madrigal-Matute J, Wang H, Kaushik S, Brodsky JL, Rader DJ, Cuervo AM, Fisher EA. Autophagy Is Required for Sortilin-Mediated Degradation of Apolipoprotein B100. Circ Res 2018; 122:568-582. [PMID: 29301854 DOI: 10.1161/circresaha.117.311240] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 12/28/2017] [Accepted: 12/29/2017] [Indexed: 12/30/2022]
Abstract
RATIONALE Genome-wide association studies identified single-nucleotide polymorphisms near the SORT1 locus strongly associated with decreased plasma LDL-C (low-density lipoprotein cholesterol) levels and protection from atherosclerotic cardiovascular disease and myocardial infarction. The minor allele of the causal SORT1 single-nucleotide polymorphism locus creates a putative C/EBPα (CCAAT/enhancer-binding protein α)-binding site in the SORT1 promoter, thereby increasing in homozygotes sortilin expression by 12-fold in liver, which is rich in this transcription factor. Our previous studies in mice have showed reductions in plasma LDL-C and its principal protein component, apoB (apolipoprotein B) with increased SORT1 expression, and in vitro studies suggested that sortilin promoted the presecretory lysosomal degradation of apoB associated with the LDL precursor, VLDL (very-low-density lipoprotein). OBJECTIVE To determine directly that SORT1 overexpression results in apoB degradation and to identify the mechanisms by which this reduces apoB and VLDL secretion by the liver, thereby contributing to understanding the clinical phenotype of lower LDL-C levels. METHODS AND RESULTS Pulse-chase studies directly established that SORT1 overexpression results in apoB degradation. As noted above, previous work implicated a role for lysosomes in this degradation. Through in vitro and in vivo studies, we now demonstrate that the sortilin-mediated route of apoB to lysosomes is unconventional and intersects with autophagy. Increased expression of sortilin diverts more apoB away from secretion, with both proteins trafficking to the endosomal compartment in vesicles that fuse with autophagosomes to form amphisomes. The amphisomes then merge with lysosomes. Furthermore, we show that sortilin itself is a regulator of autophagy and that its activity is scaled to the level of apoB synthesis. CONCLUSIONS These results strongly suggest that an unconventional lysosomal targeting process dependent on autophagy degrades apoB that was diverted from the secretory pathway by sortilin and provides a mechanism contributing to the reduced LDL-C found in individuals with SORT1 overexpression.
Collapse
Affiliation(s)
- Jaume Amengual
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Liang Guo
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Alanna Strong
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Julio Madrigal-Matute
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Haizhen Wang
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Susmita Kaushik
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Jeffrey L Brodsky
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Daniel J Rader
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Ana Maria Cuervo
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.)
| | - Edward A Fisher
- From the Division of Cardiology (J.A., L.G., H.W., E.A.F.), Department of Medicine (J.A., L.G., H.W., E.A.F.), and Marc and Ruti Bell Program in Vascular Biology (J.A., E.A.F., L.G, H.W.), NYU School of Medicine; Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., D.J.R.); Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York (J.M.-M., S.K., A.M.C.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.).
| |
Collapse
|
17
|
Singh AK, Aryal B, Zhang X, Fan Y, Price NL, Suárez Y, Fernández-Hernando C. Posttranscriptional regulation of lipid metabolism by non-coding RNAs and RNA binding proteins. Semin Cell Dev Biol 2017; 81:129-140. [PMID: 29183708 DOI: 10.1016/j.semcdb.2017.11.026] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 11/14/2017] [Accepted: 11/20/2017] [Indexed: 12/14/2022]
Abstract
Alterations in lipoprotein metabolism enhance the risk of cardiometabolic disorders including type-2 diabetes and atherosclerosis, the leading cause of death in Western societies. While the transcriptional regulation of lipid metabolism has been well characterized, recent studies have uncovered the importance of microRNAs (miRNAs), long-non-coding RNAs (lncRNAs) and RNA binding proteins (RBP) in regulating the expression of lipid-related genes at the posttranscriptional level. Work from several groups has identified a number of miRNAs, including miR-33, miR-122 and miR-148a, that play a prominent role in controlling cholesterol homeostasis and lipoprotein metabolism. Importantly, dysregulation of miRNA expression has been associated with dyslipidemia, suggesting that manipulating the expression of these miRNAs could be a useful therapeutic approach to ameliorate cardiovascular disease (CVD). The role of lncRNAs in regulating lipid metabolism has recently emerged and several groups have demonstrated their regulation of lipoprotein metabolism. However, given the high abundance of lncRNAs and the poor-genetic conservation between species, much work will be needed to elucidate the specific role of lncRNAs in controlling lipoprotein metabolism. In this review article, we summarize recent findings in the field and highlight the specific contribution of lncRNAs and RBPs in regulating lipid metabolism.
Collapse
Affiliation(s)
- Abhishek K Singh
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA
| | - Binod Aryal
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA
| | - Xinbo Zhang
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA
| | - Yuhua Fan
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA; College of Pharmacy, Harbin Medical University -Daqing, 163000, PR China
| | - Nathan L Price
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA
| | - Yajaira Suárez
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA
| | - Carlos Fernández-Hernando
- Vascular Biology and Therapeutics Program, Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine, Department of Pathology, Yale University School of Medicine, 10 Amistad St., New Haven, CT 06510, USA.
| |
Collapse
|
18
|
McCullough A, Previs S, Kasumov T. Stable isotope-based flux studies in nonalcoholic fatty liver disease. Pharmacol Ther 2017; 181:22-33. [PMID: 28720429 DOI: 10.1016/j.pharmthera.2017.07.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is associated with the worldwide epidemics of obesity, diabetes and cardiovascular diseases. NAFLD ranges from benign fat accumulation in the liver (steatosis) to non-alcoholic steatohepatitis (NASH), and cirrhosis which can progress to hepatocellular carcinoma and liver failure. Mass spectrometry and magnetic resonance spectroscopy-coupled stable isotope-based flux studies provide new insights into the understanding of NAFLD pathogenesis and the disease progression. This review focuses mainly on the utilization of mass spectrometry-based methods for the understanding of metabolic abnormalities in the different stages of NAFLD. For example, stable isotope-based flux studies demonstrated multi-organ insulin resistance, dysregulated glucose, lipids and lipoprotein metabolism in patients with NAFLD. We also review recent developments in the stable isotope-based technologies for the study of mitochondrial dysfunction, oxidative stress and fibrogenesis in NAFLD. We highlight the limitations of current methodologies, discuss the emerging areas of research in this field, and future directions for the applications of stable isotopes to study NAFLD and its complications.
Collapse
Affiliation(s)
- Arthur McCullough
- Department of Gastroenterology & Hepatology, Cleveland Clinic, Cleveland, OH, USA
| | | | - Takhar Kasumov
- Department of Gastroenterology & Hepatology, Cleveland Clinic, Cleveland, OH, USA; Department of Pharmaceutical Sciences, College of Pharmacy, Northeast Ohio Medical University, Rootstown, OH, USA.
| |
Collapse
|
19
|
Seah NE, de Magalhaes Filho CD, Petrashen AP, Henderson HR, Laguer J, Gonzalez J, Dillin A, Hansen M, Lapierre LR. Autophagy-mediated longevity is modulated by lipoprotein biogenesis. Autophagy 2016; 12:261-72. [PMID: 26671266 PMCID: PMC4836030 DOI: 10.1080/15548627.2015.1127464] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Autophagy-dependent longevity models in C. elegans display altered lipid storage profiles, but the contribution of lipid distribution to life-span extension is not fully understood. Here we report that lipoprotein production, autophagy and lysosomal lipolysis are linked to modulate life span in a conserved fashion. We find that overexpression of the yolk lipoprotein VIT/vitellogenin reduces the life span of long-lived animals by impairing the induction of autophagy-related and lysosomal genes necessary for longevity. Accordingly, reducing vitellogenesis increases life span via induction of autophagy and lysosomal lipolysis. Life-span extension due to reduced vitellogenesis or enhanced lysosomal lipolysis requires nuclear hormone receptors (NHRs) NHR-49 and NHR-80, highlighting novel roles for these NHRs in lysosomal lipid signaling. In dietary-restricted worms and mice, expression of VIT and hepatic APOB (apolipoprotein B), respectively, are significantly reduced, suggesting a conserved longevity mechanism. Altogether, our study demonstrates that lipoprotein biogenesis is an important mechanism that modulates aging by impairing autophagy and lysosomal lipolysis.
Collapse
Affiliation(s)
- Nicole E Seah
- a Department of Molecular Biology , Cell Biology and Biochemistry, Brown University , Providence , RI , USA
| | - C Daniel de Magalhaes Filho
- b The Howard Hughes Medical Institute, The Glenn Center for Aging Research, The Salk Institute for Biological Studies , La Jolla , CA , USA.,c The Howard Hughes Medical Institute, Molecular and Cell Biology Department, Li Ka Shing Center, University of California Berkeley , Berkeley , CA , USA
| | - Anna P Petrashen
- a Department of Molecular Biology , Cell Biology and Biochemistry, Brown University , Providence , RI , USA
| | - Hope R Henderson
- c The Howard Hughes Medical Institute, Molecular and Cell Biology Department, Li Ka Shing Center, University of California Berkeley , Berkeley , CA , USA.,d Del E. Webb Neuroscience , Aging and Stem Cell Research Center, Program of Development and Aging, Sanford-Burnham Medical Research Institute , La Jolla , CA , USA
| | - Jade Laguer
- d Del E. Webb Neuroscience , Aging and Stem Cell Research Center, Program of Development and Aging, Sanford-Burnham Medical Research Institute , La Jolla , CA , USA
| | - Julissa Gonzalez
- d Del E. Webb Neuroscience , Aging and Stem Cell Research Center, Program of Development and Aging, Sanford-Burnham Medical Research Institute , La Jolla , CA , USA
| | - Andrew Dillin
- b The Howard Hughes Medical Institute, The Glenn Center for Aging Research, The Salk Institute for Biological Studies , La Jolla , CA , USA.,c The Howard Hughes Medical Institute, Molecular and Cell Biology Department, Li Ka Shing Center, University of California Berkeley , Berkeley , CA , USA
| | - Malene Hansen
- d Del E. Webb Neuroscience , Aging and Stem Cell Research Center, Program of Development and Aging, Sanford-Burnham Medical Research Institute , La Jolla , CA , USA
| | - Louis R Lapierre
- a Department of Molecular Biology , Cell Biology and Biochemistry, Brown University , Providence , RI , USA.,d Del E. Webb Neuroscience , Aging and Stem Cell Research Center, Program of Development and Aging, Sanford-Burnham Medical Research Institute , La Jolla , CA , USA
| |
Collapse
|
20
|
Walsh MT, Hussain MM. Targeting microsomal triglyceride transfer protein and lipoprotein assembly to treat homozygous familial hypercholesterolemia. Crit Rev Clin Lab Sci 2016; 54:26-48. [PMID: 27690713 DOI: 10.1080/10408363.2016.1221883] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Homozygous familial hypercholesterolemia (HoFH) is a polygenic disease arising from defects in the clearance of plasma low-density lipoprotein (LDL), which results in extremely elevated plasma LDL cholesterol (LDL-C) and increased risk of atherosclerosis, coronary heart disease, and premature death. Conventional lipid-lowering therapies, such as statins and ezetimibe, are ineffective at lowering plasma cholesterol to safe levels in these patients. Other therapeutic options, such as LDL apheresis and liver transplantation, are inconvenient, costly, and not readily available. Recently, lomitapide was approved by the Federal Drug Administration as an adjunct therapy for the treatment of HoFH. Lomitapide inhibits microsomal triglyceride transfer protein (MTP), reduces lipoprotein assembly and secretion, and lowers plasma cholesterol levels by over 50%. Here, we explain the steps involved in lipoprotein assembly, summarize the role of MTP in lipoprotein assembly, explore the clinical and molecular basis of HoFH, and review pre-clinical studies and clinical trials with lomitapide and other MTP inhibitors for the treatment of HoFH. In addition, ongoing research and new approaches underway for better treatment modalities are discussed.
Collapse
Affiliation(s)
- Meghan T Walsh
- a School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center , Brooklyn , NY , USA.,b Department of Cell Biology , State University of New York Downstate Medical Center , Brooklyn , NY , USA
| | - M Mahmood Hussain
- b Department of Cell Biology , State University of New York Downstate Medical Center , Brooklyn , NY , USA.,c Department of Pediatrics , SUNY Downstate Medical Center , Brooklyn , NY , USA.,d VA New York Harbor Healthcare System , Brooklyn , NY , USA , and.,e Winthrop University Hospital , Mineola , NY , USA
| |
Collapse
|
21
|
Santos AJM, Nogueira C, Ortega-Bellido M, Malhotra V. TANGO1 and Mia2/cTAGE5 (TALI) cooperate to export bulky pre-chylomicrons/VLDLs from the endoplasmic reticulum. J Cell Biol 2016; 213:343-54. [PMID: 27138255 PMCID: PMC4862334 DOI: 10.1083/jcb.201603072] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 04/14/2016] [Indexed: 01/04/2023] Open
Abstract
Santos et al. show that TANGO1 and a TANGO1-like protein, TALI, bind each other and function together as receptors to export bulky ApoB-containing lipid particles from the endoplasmic reticulum. However, TANGO1-mediated export of bulky collagens by the same cells is TALI independent. Procollagens, pre-chylomicrons, and pre–very low-density lipoproteins (pre-VLDLs) are too big to fit into conventional COPII-coated vesicles, so how are these bulky cargoes exported from the endoplasmic reticulum (ER)? We have shown that TANGO1 located at the ER exit site is necessary for procollagen export. We report a role for TANGO1 and TANGO1-like (TALI), a chimeric protein resulting from fusion of MIA2 and cTAGE5 gene products, in the export of pre-chylomicrons and pre-VLDLs from the ER. TANGO1 binds TALI, and both interact with apolipoprotein B (ApoB) and are necessary for the recruitment of ApoB-containing lipid particles to ER exit sites for their subsequent export. Although export of ApoB requires the function of both TANGO1 and TALI, the export of procollagen XII by the same cells requires only TANGO1. These findings reveal a general role for TANGO1 in the export of bulky cargoes from the ER and identify a specific requirement for TALI in assisting TANGO1 to export bulky lipid particles.
Collapse
Affiliation(s)
- António J M Santos
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08002 Barcelona, Spain
| | - Cristina Nogueira
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08002 Barcelona, Spain
| | - Maria Ortega-Bellido
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08002 Barcelona, Spain
| | - Vivek Malhotra
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08002 Barcelona, Spain Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
| |
Collapse
|
22
|
Jiang ZG, de Boer IH, Mackey RH, Jensen MK, Lai M, Robson SC, Tracy R, Kuller LH, Mukamal KJ. Associations of insulin resistance, inflammation and liver synthetic function with very low-density lipoprotein: The Cardiovascular Health Study. Metabolism 2016; 65:92-9. [PMID: 26892520 PMCID: PMC4761104 DOI: 10.1016/j.metabol.2015.10.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 10/04/2015] [Accepted: 10/07/2015] [Indexed: 01/21/2023]
Abstract
INTRODUCTION Production of very low-density lipoprotein (VLDL) is increased in states of metabolic syndrome, leading to hypertriglyceridemia. However, metabolic syndrome is often associated with non-alcoholic fatty liver disease, which leads to liver fibrosis and inflammation that may decrease VLDL production. In this study, we aim to determine the interactive impact on VLDL profiles from insulin resistance, impairment in liver synthetic function and inflammation. METHODS We examined cross-sectional associations of insulin sensitivity, inflammation, and liver synthetic function with VLDL particle (VLDL-P) concentration and size among 1,850 older adults in the Cardiovascular Health Study. RESULTS Indices for high insulin sensitivity and low liver synthetic function were associated with lower concentrations of VLDL-P. In addition, insulin resistance preferentially increased concentration of large VLDL and was associated with mean VLDL size. Indices for inflammation however demonstrated a nonlinear relationship with both VLDL-P concentration and VLDL size. When mutually adjusted, one standard deviation (SD) increment in Matsuda index and C-reactive protein (CRP) were associated with 4.9 nmol/L (-8.2 to -1.5, p=0.005) and 6.3 nmol/L (-11.0 to -1.6, p=0.009) lower VLDL-P concentration respectively. In contrast, one-SD increment in factor VII, a marker for liver synthetic function, was associated with 16.9 nmol/L (12.6-21.2, p<0.001) higher VLDL-P concentration. Furthermore, a one-SD increment in the Matsuda index was associated with 1.1 nm (-2.0 to -0.3, p=0.006) smaller mean VLDL size, whereas CRP and factor VII were not associated with VLDL size. CONCLUSION Insulin sensitivity, inflammation and markers for liver synthetic function differentially impact VLDL-P concentration and VLDL size. These results underscore the complex effects of insulin resistance and its complications on VLDL production.
Collapse
Affiliation(s)
- Z Gordon Jiang
- Division of Gastroenterology and Hepatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard School of Medicine, Boston, MA 02115.
| | - Ian H de Boer
- Division of Nephrology, University of Washington, Seattle, WA 98195
| | - Rachel H Mackey
- Department of Pathology, University of Vermont College of Medicine, Burlington, VT 05405
| | - Majken K Jensen
- Department of Nutrition, Harvard School of Public Health, Boston, MA 02115
| | - Michelle Lai
- Division of Gastroenterology and Hepatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard School of Medicine, Boston, MA 02115
| | - Simon C Robson
- Division of Gastroenterology and Hepatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard School of Medicine, Boston, MA 02115
| | - Russell Tracy
- Department of Pathology and Laboratory Medicine, University of Vermont College of Medicine, Burlington, VT 05405
| | - Lewis H Kuller
- Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15261
| | - Kenneth J Mukamal
- Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center, Boston, MA 02115
| |
Collapse
|
23
|
Zhou L, Irani S, Sirwi A, Hussain MM. MicroRNAs regulating apolipoprotein B-containing lipoprotein production. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:2062-2068. [PMID: 26923435 DOI: 10.1016/j.bbalip.2016.02.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 02/18/2016] [Accepted: 02/22/2016] [Indexed: 02/07/2023]
Abstract
MicroRNAs (miRs) are small, non-coding RNAs that regulate gene expression and have been implicated in many pathological conditions. Significant progress has been made to unveil their role in lipid metabolism. This review aims at summarizing the role of different miRs that regulate hepatic assembly and secretion of apolipoprotein B (apoB)-containing lipoproteins. Overproduction and/or impaired clearance of these lipoproteins from circulation increase plasma concentrations of lipids enhancing risk for cardiovascular disease. So far, three miRs, miR-122, miR-34a, and miR-30c have been shown to modulate hepatic production of apoB-containing low density lipoproteins. In this review, we will first provide a brief overview of lipid metabolism and apoB-containing lipoprotein assembly to orient readers to different steps that have been shown to be regulated by miRs. Then, we will discuss the role of each miR on plasma lipids and atherosclerotic burden. Furthermore, we will summarize mechanistic studies explaining how these miRs regulate hepatic lipid synthesis, fatty acid oxidation, and lipoprotein secretion. Finally, we will briefly highlight the potential use of each miR as a therapeutic drug for treating cardiovascular diseases. This article is part of a Special Issue entitled: MicroRNAs and lipid/energy metabolism and related diseases edited by Carlos Fernández-Hernando and Yajaira Suárez.
Collapse
Affiliation(s)
- Liye Zhou
- School of Graduate Studies, Molecular and Cell Biology Program, USA; Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, USA; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY, USA
| | - Sara Irani
- School of Graduate Studies, Molecular and Cell Biology Program, USA; Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, USA; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY, USA
| | - Alaa Sirwi
- School of Graduate Studies, Molecular and Cell Biology Program, USA; Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, USA; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY, USA
| | - M Mahmood Hussain
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, USA; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY, USA; VA New York Harbor Healthcare System, Brooklyn, NY, USA.
| |
Collapse
|
24
|
Fisher EA. Regression of Atherosclerosis: The Journey From the Liver to the Plaque and Back. Arterioscler Thromb Vasc Biol 2015; 36:226-35. [PMID: 26681754 DOI: 10.1161/atvbaha.115.301926] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 11/18/2015] [Indexed: 11/16/2022]
Abstract
Cardinal events in atherogenesis are the retention of apolipoprotein B-containing lipoproteins in the arterial wall and the reaction of macrophages to these particles. My laboratory has been interested in both the cell biological events producing apolipoprotein B-containing lipoproteins, as well as in the reversal of the damage they cause in the plaques formed in the arterial wall. In the 2013 George Lyman Duff Memorial Lecture, as summarized in this review, I covered 3 areas of my past, present, and future interests, namely, the regulation of hepatic very low density lipoprotein production by the degradation of apolipoprotein B100, the dynamic changes in macrophages in the regression of atherosclerosis, and the application of nanoparticles to both image and treat atherosclerotic plaques.
Collapse
Affiliation(s)
- Edward A Fisher
- From the Department of Medicine (Cardiology), the Marc and Ruti Bell Program in Vascular Biology and the Center for the Prevention of Cardiovascular Disease, New York University School of Medicine.
| |
Collapse
|
25
|
Hepatocyte-Specific Depletion of UBXD8 Induces Periportal Steatosis in Mice Fed a High-Fat Diet. PLoS One 2015; 10:e0127114. [PMID: 25970332 PMCID: PMC4430229 DOI: 10.1371/journal.pone.0127114] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Accepted: 04/10/2015] [Indexed: 12/19/2022] Open
Abstract
We showed previously that UBXD8 plays a key role in proteasomal degradation of lipidated ApoB in hepatocarcinoma cell lines. In the present study, we aimed to investigate the functions of UBXD8 in liver in vivo. For this purpose, hepatocyte-specific UBXD8 knockout (UBXD8-LKO) mice were generated. They were fed with a normal or high-fat diet, and the phenotypes were compared with those of littermate control mice. Hepatocytes obtained from UBXD8-LKO and control mice were analyzed in culture. After 26 wk of a high-fat diet, UBXD8-LKO mice exhibited macrovesicular steatosis in the periportal area and microvesicular steatosis in the perivenular area, whereas control mice exhibited steatosis only in the perivenular area. Furthermore, UBXD8-LKO mice on a high-fat diet had significantly lower concentrations of serum triglyceride and VLDL than control mice. A Triton WR-1339 injection study revealed that VLDL secretion from hepatocytes was reduced in UBXD8-LKO mice. The decrease of ApoB secretion upon UBXD8 depletion was recapitulated in cultured primary hepatocytes. Accumulation of lipidated ApoB in lipid droplets was observed only in UBXD8-null hepatocytes. The results showed that depletion of UBXD8 in hepatocytes suppresses VLDL secretion, and could lead to periportal steatosis when mice are fed a high-fat diet. This is the first demonstration that an abnormality in the intracellular ApoB degradation mechanism can cause steatosis, and provides a useful model for periportal steatosis, which occurs in several human diseases.
Collapse
|
26
|
|
27
|
New insights into the pathophysiology of dyslipidemia in type 2 diabetes. Atherosclerosis 2015; 239:483-95. [PMID: 25706066 DOI: 10.1016/j.atherosclerosis.2015.01.039] [Citation(s) in RCA: 256] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 01/28/2015] [Accepted: 01/30/2015] [Indexed: 02/06/2023]
Abstract
Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality for patients with type 2 diabetes, despite recent significant advances in management strategies to lessen CVD risk factors. A major cause is the atherogenic dyslipidemia, which consists of elevated plasma concentrations of both fasting and postprandial triglyceride-rich lipoproteins (TRLs), small dense low-density lipoprotein (LDL) and low high-density lipoprotein (HDL) cholesterol. The different components of diabetic dyslipidemia are not isolated abnormalities but closely linked to each other metabolically. The underlying disturbances are hepatic overproduction and delayed clearance of TRLs. Recent results have unequivocally shown that triglyceride-rich lipoproteins and their remnants are atherogenic. To develop novel strategies for the prevention and treatment of dyslipidaemia, it is essential to understand the pathophysiology of dyslipoproteinaemia in humans. Here, we review recent advances in our understanding of the pathophysiology of diabetic dyslipidemia.
Collapse
|
28
|
Choi K, Kim H, Kang H, Lee SY, Lee SJ, Back SH, Lee SH, Kim MS, Lee JE, Park JY, Kim J, Kim S, Song JH, Choi Y, Lee S, Lee HJ, Kim JH, Cho S. Regulation of diacylglycerol acyltransferase 2 protein stability by gp78-associated endoplasmic-reticulum-associated degradation. FEBS J 2014; 281:3048-60. [DOI: 10.1111/febs.12841] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 04/28/2014] [Accepted: 05/09/2014] [Indexed: 12/24/2022]
Affiliation(s)
- Kwangman Choi
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Hyeongki Kim
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
- Department of Biomolecular Science; University of Science and Technology; Daejeon Korea
| | - Hyunju Kang
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - So-Young Lee
- International Cooperation Office; Ministry of Food and Drug Safety; Cheongwon Chungbuk Korea
| | - Sang Jun Lee
- Infection and Immunity Research Center; Korea Research Institute of Bioscience and Biotechnology; Daejeon Korea
| | - Sung Hoon Back
- School of Biological Sciences; University of Ulsan; Korea
| | - Seo Hyun Lee
- Cancer Cell and Molecular Biology Branch; Research Institute; National Cancer Center; Goyang Korea
| | - M. Sun Kim
- Cancer Cell and Molecular Biology Branch; Research Institute; National Cancer Center; Goyang Korea
| | - Jeong Eun Lee
- Cancer Cell and Molecular Biology Branch; Research Institute; National Cancer Center; Goyang Korea
| | - Ju Young Park
- Cancer Cell and Molecular Biology Branch; Research Institute; National Cancer Center; Goyang Korea
| | - Jiye Kim
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Sunhong Kim
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Jae-Hyung Song
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Yura Choi
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Suui Lee
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Hyun-Jun Lee
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
| | - Jong Heon Kim
- Cancer Cell and Molecular Biology Branch; Research Institute; National Cancer Center; Goyang Korea
- Department of System Cancer Science; Graduate School of Cancer Science and Policy; National Cancer Center; Goyang Korea
| | - Sungchan Cho
- Targeted Medicine Research Center; Korea Research Institute of Bioscience and Biotechnology; Cheongwon Chungbuk Korea
- Department of Biomolecular Science; University of Science and Technology; Daejeon Korea
| |
Collapse
|
29
|
Jiang J, Chen H, Wang L. Gene expression analysis of familial hypercholesterolemia. Mol Biol 2014. [DOI: 10.1134/s002689331401004x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
30
|
Butkinaree C, Guo L, Ramkhelawon B, Wanschel A, Brodsky JL, Moore KJ, Fisher EA. A regulator of secretory vesicle size, Kelch-like protein 12, facilitates the secretion of apolipoprotein B100 and very-low-density lipoproteins--brief report. Arterioscler Thromb Vasc Biol 2013; 34:251-4. [PMID: 24334870 DOI: 10.1161/atvbaha.113.302728] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
OBJECTIVE One of the major risk factors for atherosclerosis is the plasma level of low-density lipoprotein (LDL), which is a product of very-low-density lipoprotein (VLDL). Hepatic apolipoprotein B100 (apoB100) is the essential component that provides structural stability to VLDL particles. Newly translated apoB100 is partially lipidated in the endoplasmic reticulum (ER), forming nascent apoB100-VLDL particles. These particles are further modified to form fully mature VLDLs in the Golgi apparatus. Therefore, the transport of nascent VLDL from the ER to the Golgi represents a critical step during VLDL maturation and secretion and in regulating serum LDL cholesterol levels. Our previous studies showed that apoB100 exits the ER in coat complex II vesicles (COPII), but the cohort of related factors that control trafficking is poorly defined. APPROACH AND RESULTS Expression levels of Kelch-like protein 12 (KLHL12), an adaptor protein known to assist COPII-dependent transport of procollagen, were manipulated by using a KLHL12-specific small interfering RNA and a KLHL12 expression plasmid in the rat hepatoma cell line, McArdle RH7777. KLHL12 knockdown decreased the secreted and intracellular pools of apoB100, an effect that was attenuated in the presence of an autophagy inhibitor. KLHL12 knockdown also significantly reduced secretion of the most lipidated apoB100-VLDL species and led to the accumulation of apoB100 in the ER. Consistent with these data, KLHL12 overexpression increased apoB100 recovery and apoB100-VLDL secretion. Images obtained from confocal microscopy revealed colocalization of apoB100 and KLHL12, further supporting a direct link between KLHL12 function and VLDL trafficking from the ER. CONCLUSIONS KLHL12 plays a critical role in facilitating the ER exit and secretion of apoB100-VLDL particles, suggesting that KLHL12 modulation would influence plasma lipid levels.
Collapse
Affiliation(s)
- Chutikarn Butkinaree
- From the Department of Medicine, Leon H. Charney Division of Cardiology, Department of Cell Biology, and the Marc and Ruti Bell Vascular Biology and Disease Program, New York University School of Medicine (C.B., L.G., B.R., A.W., K.J.M., E.A.F.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.). C.B. is currently affiliated with Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec, Canada
| | | | | | | | | | | | | |
Collapse
|
31
|
Abstract
Cardiovascular disease represents the most common cause of death in patients with nonalcoholic fatty liver disease (NAFLD). Patients with NAFLD exhibit an atherogenic dyslipidemia that is characterized by an increased plasma concentration of triglycerides, reduced concentration of high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) particles that are smaller and more dense than normal. The pathogenesis of NAFLD-associated atherogenic dyslipidemia is multifaceted, but many aspects are attributable to manifestations of insulin resistance. Here the authors review the structure, function, and metabolism of lipoproteins, which are macromolecular particles of lipids and proteins that transport otherwise insoluble triglyceride and cholesterol molecules within the plasma. They provide a current explanation of the metabolic perturbations that are observed in the setting of insulin resistance. An improved understanding of the pathophysiology of atherogenic dyslipidemia would be expected to guide therapies aimed at reducing morbidity and mortality in patients with NAFLD.
Collapse
Affiliation(s)
- Edward Fisher
- Division of Cardiology, Department of Medicine, The Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York
| | - David Cohen
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| |
Collapse
|
32
|
Maitin V, Andreo U, Guo L, Fisher EA. Docosahexaenoic acid impairs the maturation of very low density lipoproteins in rat hepatic cells. J Lipid Res 2013; 55:75-84. [PMID: 24136824 DOI: 10.1194/jlr.m043026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One mechanism of the lipid-lowering effects of the fish oil n-3 fatty acids [e.g., docosahexaenoic acid (DHA)] in cell and animal models is induced hepatic apolipoprotein B100 (apoB) presecretory degradation. This degradation occurs post-endoplasmic reticulum, but whether DHA induces it before or after intracellular VLDL formation remains unanswered. We found in McA-RH7777 rat hepatic cells that DHA and oleic acid (OA) treatments allowed formation of pre-VLDL particles and their transport to the Golgi, but, in contrast to OA, with DHA pre-VLDL particles failed to quantitatively assemble into fully lipidated (mature) VLDL. This failure required lipid peroxidation and was accompanied by the formation of apoB aggregates (known to be degraded by autophagy). Preventing the exit of proteins from the Golgi blocked the aggregation of apoB but did not restore VLDL maturation, indicating that failure to fully lipidate apoB preceded its aggregation. ApoB autophagic degradation did not appear to require an intermediate step of cytosolic aggresome formation. Taken with other examples in the literature, the results of this study suggest that pre-VLDL particles that are competent to escape endoplasmic reticulum quality control mechanisms but fail to mature in the Golgi remain subject to quality control surveillance late in the secretory pathway.
Collapse
Affiliation(s)
- Vatsala Maitin
- Departments of Medicine (Leon H. Charney Division of Cardiology) and Cell Biology and the Marc and Ruti Bell Vascular Biology and Disease Program, New York University School of Medicine, New York, NY 10016; and
| | | | | | | |
Collapse
|
33
|
Xiao G, Zhang T, Yu S, Lee S, Calabuig-Navarro V, Yamauchi J, Ringquist S, Dong HH. ATF4 protein deficiency protects against high fructose-induced hypertriglyceridemia in mice. J Biol Chem 2013; 288:25350-25361. [PMID: 23888053 DOI: 10.1074/jbc.m113.470526] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Hypertriglyceridemia is the most common lipid disorder in obesity and type 2 diabetes. It results from increased production and/or decreased clearance of triglyceride-rich lipoproteins. To better understand the pathophysiology of hypertriglyceridemia, we studied hepatic regulation of triglyceride metabolism by the activating transcription factor 4 (ATF4), a member of the basic leucine zipper-containing protein subfamily. We determined the effect of ATF4 on hepatic lipid metabolism in Atf4(-/-) mice fed regular chow or provided with free access to fructose drinking water. ATF4 depletion preferentially attenuated hepatic lipogenesis without affecting hepatic triglyceride production and fatty acid oxidation. This effect prevented excessive fat accumulation in the liver of Atf4(-/-) mice, when compared with wild-type littermates. To gain insight into the underlying mechanism, we showed that ATF4 depletion resulted in a significant reduction in hepatic expression of peroxisome proliferator-activated receptor-γ, a nuclear receptor that acts to promote lipogenesis in the liver. This effect was accompanied by a significant reduction in hepatic expression of sterol regulatory element-binding protein 1c (SREBP-1c), acetyl-CoA carboxylase, and fatty-acid synthase, three key functions in the lipogenic pathway in Atf4(-/-) mice. Of particular significance, we found that Atf4(-/-) mice, as opposed to wild-type littermates, were protected against the development of steatosis and hypertriglyceridemia in response to high fructose feeding. These data demonstrate that ATF4 plays a critical role in regulating hepatic lipid metabolism in response to nutritional cues.
Collapse
Affiliation(s)
- Guozhi Xiao
- From the Department of Biochemistry, Rush University Medical Center, Chicago, Illinois 60612,; the College of Life Sciences, Nankai University, Tianjin 300071, China, and.
| | - Ting Zhang
- the Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, and
| | - Shibing Yu
- the Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15224
| | - Sojin Lee
- the Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, and
| | - Virtu Calabuig-Navarro
- the Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, and
| | - Jun Yamauchi
- the Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, and
| | - Steven Ringquist
- the Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, and
| | - H Henry Dong
- the Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, and.
| |
Collapse
|
34
|
Borén J, Taskinen MR, Olofsson SO, Levin M. Ectopic lipid storage and insulin resistance: a harmful relationship. J Intern Med 2013; 274:25-40. [PMID: 23551521 DOI: 10.1111/joim.12071] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Obesity increases the risk of metabolic diseases, including insulin resistance and type 2 diabetes, as well as cardiovascular disease. In addition to lipid accumulation in adipose tissue, obesity is associated with increased lipid storage in ectopic tissues, such as skeletal muscle and liver. Furthermore, lipid accumulation in the heart may result in cardiac dysfunction and heart failure. It has recently been demonstrated that intracellular lipid accumulation in ectopic tissues leads to pathological responses and impaired insulin signalling. Here, we will review the current understanding of how lipid storage and lipid droplet physiology affect the risk of developing metabolic diseases.
Collapse
Affiliation(s)
- J Borén
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden.
| | | | | | | |
Collapse
|
35
|
Insulin-stimulated degradation of apolipoprotein B100: roles of class II phosphatidylinositol-3-kinase and autophagy. PLoS One 2013; 8:e57590. [PMID: 23516411 PMCID: PMC3596368 DOI: 10.1371/journal.pone.0057590] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 01/27/2013] [Indexed: 11/24/2022] Open
Abstract
Both in humans and animal models, an acute increase in plasma insulin levels, typically following meals, leads to transient depression of hepatic secretion of very low density lipoproteins (VLDL). One contributing mechanism for the decrease in VLDL secretion is enhanced degradation of apolipoprotein B100 (apoB100), which is required for VLDL formation. Unlike the degradation of nascent apoB100, which occurs in the endoplasmic reticulum (ER), insulin-stimulated apoB100 degradation occurs post-ER and is inhibited by pan-phosphatidylinositol (PI)3-kinase inhibitors. It is unclear, however, which of the three classes of PI3-kinases is required for insulin-stimulated apoB100 degradation, as well as the proteolytic machinery underlying this response. Class III PI3-kinase is not activated by insulin, but the other two classes are. By using a class I-specific inhibitor and siRNA to the major class II isoform in liver, we now show that it is class II PI3-kinase that is required for insulin-stimulated apoB100 degradation in primary mouse hepatocytes. Because the insulin-stimulated process resembles other examples of apoB100 post-ER proteolysis mediated by autophagy, we hypothesized that the effects of insulin in autophagy-deficient mouse primary hepatocytes would be attenuated. Indeed, apoB100 degradation in response to insulin was significantly impaired in two types of autophagy-deficient hepatocytes. Together, our data demonstrate that insulin-stimulated apoB100 degradation in the liver requires both class II PI3-kinase activity and autophagy.
Collapse
|
36
|
Christian P, Sacco J, Adeli K. Autophagy: Emerging roles in lipid homeostasis and metabolic control. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:819-24. [PMID: 23274236 DOI: 10.1016/j.bbalip.2012.12.009] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 12/13/2012] [Accepted: 12/18/2012] [Indexed: 02/06/2023]
Abstract
Current evidence implicates autophagy in the regulation of lipid stores within the two main organs involved in maintaining lipid homeostasis, the liver and adipose tissue. Critical to this role in hepatocytes is the breakdown of cytoplasmic lipid droplets, a process referred to as lipophagy. Conversely, autophagy is required for adipocyte differentiation and the concurrent accumulation of lipid droplets. Autophagy also affects lipid metabolism through contributions to lipoprotein assembly. A number of reports have now implicated autophagy in the degradation of apolipoprotein B, the main structural protein of very-low-density-lipoprotein. Aberrant autophagy may also be involved in conditions of deregulated lipid homeostasis in metabolic disorders such as the metabolic syndrome. First, insulin signalling and autophagy activity appear to diverge in a mechanism of reciprocal regulation, suggesting a role for autophagy in insulin resistance. Secondly, upregulation of autophagy may lead to conversion of white adipose tissue into brown adipose tissue, thus regulating energy expenditure and obesity. Thirdly, upregulation of autophagy in hepatocytes could increase breakdown of lipid stores controlling triglyceride homeostasis and fatty liver. Taken together, autophagy appears to play a very complex role in lipid homeostasis, affecting lipid stores differently depending on the tissue, as well as contributing to pathways of lipoprotein metabolism.
Collapse
Affiliation(s)
- Patricia Christian
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8
| | | | | |
Collapse
|
37
|
Chang MI, Puder M, Gura KM. The use of fish oil lipid emulsion in the treatment of intestinal failure associated liver disease (IFALD). Nutrients 2012; 4:1828-50. [PMID: 23363993 PMCID: PMC3546610 DOI: 10.3390/nu4121828] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 11/11/2012] [Accepted: 11/19/2012] [Indexed: 01/07/2023] Open
Abstract
Since 2004, fish oil based lipid emulsions have been used in the treatment of intestinal failure associated liver disease, with a noticeable impact on decreasing the incidence of morbidity and mortality of this often fatal condition. With this new therapy, however, different approaches have emerged as well as concerns about potential risks with using fish oil as a monotherapy. This review will discuss the experience to date with this lipid emulsion along with the rational for its use, controversies and concerns.
Collapse
|
38
|
Smith MH, Ploegh HL, Weissman JS. Road to ruin: targeting proteins for degradation in the endoplasmic reticulum. Science 2012; 334:1086-90. [PMID: 22116878 PMCID: PMC3864754 DOI: 10.1126/science.1209235] [Citation(s) in RCA: 480] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Some nascent proteins that fold within the endoplasmic reticulum (ER) never reach their native state. Misfolded proteins are removed from the folding machinery, dislocated from the ER into the cytosol, and degraded in a series of pathways collectively referred to as ER-associated degradation (ERAD). Distinct ERAD pathways centered on different E3 ubiquitin ligases survey the range of potential substrates. We now know many of the components of the ERAD machinery and pathways used to detect substrates and target them for degradation. Much less is known about the features used to identify terminally misfolded conformations and the broader role of these pathways in regulating protein half-lives.
Collapse
Affiliation(s)
- Melanie H Smith
- Department of Cellular and Molecular Pharmacology, Graduate Group in Biophysics and Howard Hughes Medical Institute, University of California-San Francisco, CA 94158, USA
| | | | | |
Collapse
|
39
|
A malfunction in triglyceride transfer from the intracellular lipid pool to apoB in enterocytes of SOD1-deficient mice. FEBS Lett 2012; 586:4289-95. [PMID: 23098755 DOI: 10.1016/j.febslet.2012.09.047] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 09/28/2012] [Indexed: 12/16/2022]
Abstract
We compared lipid metabolism in the intestines of Sod1-knockout mice with that found in wild-type mice to elucidate the impact of oxidative stress in vivo. A high-fat diet in wild-type mice induced postprandial hypertriglyceridemia, but this adaptive response was impaired in Sod1-knockout mice. While fewer triglycerides were secreted to the blood in the form of triglyceride-rich lipoprotein, more lipid droplets accumulated in the enterocytes of Sod1-knockout mice fed a high-fat diet. These data collectively suggest that high-fat diet induces oxidative stress, inhibits lipid secretion to the blood, and ultimately leads to dysfunctional lipid metabolism in enterocytes.
Collapse
|
40
|
Ke PY, Chen SSL. Hepatitis C virus and cellular stress response: implications to molecular pathogenesis of liver diseases. Viruses 2012. [PMID: 23202463 PMCID: PMC3497051 DOI: 10.3390/v4102251] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Infection with hepatitis C virus (HCV) is a leading risk factor for chronic liver disease progression, including steatosis, cirrhosis, and hepatocellular carcinoma. With approximately 3% of the human population infected worldwide, HCV infection remains a global public health challenge. The efficacy of current therapy is still limited in many patients infected with HCV, thus a greater understanding of pathogenesis in HCV infection is desperately needed. Emerging lines of evidence indicate that HCV triggers a wide range of cellular stress responses, including cell cycle arrest, apoptosis, endoplasmic reticulum (ER) stress/unfolded protein response (UPR), and autophagy. Also, recent studies suggest that these HCV-induced cellular responses may contribute to chronic liver diseases by modulating cell proliferation, altering lipid metabolism, and potentiating oncogenic pathways. However, the molecular mechanism underlying HCV infection in the pathogenesis of chronic liver diseases still remains to be determined. Here, we review the known stress response activation in HCV infection in vitro and in vivo, and also explore the possible relationship of a variety of cellular responses with the pathogenicity of HCV-associated diseases. Comprehensive knowledge of HCV-mediated disease progression shall shed new insights into the discovery of novel therapeutic targets and the development of new intervention strategy.
Collapse
Affiliation(s)
- Po-Yuan Ke
- Department of Biochemistry and Molecular Biology, College of Medicine, Chang Gung University, Taoyuan 33371, Taiwan, Republic of China; (P.-Y.K.)
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan, Republic of China
| | - Steve S.-L. Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan, Republic of China
- Author to whom correspondence should be addressed; (S.-L.C.); Tel.: +886-2-2652-3933, Fax: +886-2-2652-3073
| |
Collapse
|
41
|
Fisher EA, Brodsky JL. The unfolded protein response: a multifaceted regulator of lipid and lipoprotein metabolism. Cell Metab 2012; 16:407-8. [PMID: 23040063 DOI: 10.1016/j.cmet.2012.09.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Elevated levels of circulating lipids are the major cause of cardiovascular disease, but beneficial outcomes might be realized by targeting lipid carriers. Two papers in this issue of Cell Metabolism (So et al., 2012; Wang et al., 2012) demonstrate how modulation of one arm of the unfolded protein response can decrease plasma levels of VLDL particles and their associated lipids.
Collapse
Affiliation(s)
- Edward A Fisher
- Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
| | | |
Collapse
|
42
|
Bingham TC, Parathath S, Tian H, Reiss A, Chan E, Fisher EA, Cronstein BN. Cholesterol 27-hydroxylase but not apolipoprotein apoE contributes to A2A adenosine receptor stimulated reverse cholesterol transport. Inflammation 2012; 35:49-57. [PMID: 21258856 DOI: 10.1007/s10753-010-9288-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Movement of free cholesterol between the cellular compartment and acceptor is governed by cholesterol gradients that are determined by several enzymes and reverse cholesterol transport proteins. We have previously demonstrated that adenosine A(2A) receptors inhibit foam cell formation and stimulate production of cholesterol 27-hydroxylase (CYP27A1), an enzyme involved in the conversion of cholesterol to oxysterols. We therefore asked whether the effect of adenosine A(2A) receptors on foam cell formation in vitro is mediated by CYP27A1 or apoE, a carrier for cholesterol in the serum. We found that specific lentiviral siRNA infection markedly reduced apoE or 27-hydroxylase mRNA in THP-1 cells. Despite diminished apoE expression (p < 0.0002, interferon-gamma (IFNγ) CGS vs. IFNγ alone, n=4), CGS-21680, an adenosine A(2A) receptor agonist, inhibits foam cell formation. In contrast, CGS-21680 had no effect on reducing foam cell formation in CYP27A1 KD cells (4 ± 2%; p<0.5113, inhibition vs. IFNγ alone, n=4). Previously, we reported the A(2A) agonist CGS-21680 increases apoAI-mediated cholesterol efflux nearly twofold in wild-type macrophages. Adenosine receptor activation had no effect on cholesterol efflux in CYP27A1 KD cells but reduced efflux in apoE KD cells. These results demonstrate that adenosine A(2A) receptor occupancy diminishes foam cell formation by increasing expression and function of CYP27A1.
Collapse
Affiliation(s)
- Taiese Crystal Bingham
- Department of Medicine, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
| | | | | | | | | | | | | |
Collapse
|
43
|
Olofsson SO, Borén J. Apolipoprotein B Secretory Regulation by Degradation. Arterioscler Thromb Vasc Biol 2012; 32:1334-8. [DOI: 10.1161/atvbaha.112.251116] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this short review, we discuss apolipoprotein B100 and the assembly of very low-density lipoproteins. In particular, we address the nature and importance of co- and posttranslational degradation of apolipoprotein B100 during the assembly process. We also provide a short historical background to the development of the current model for the degradation of apolipoprotein B100.
Collapse
Affiliation(s)
- Sven-Olof Olofsson
- From the Sahlgrenska Center for Cardiovascular and Metabolic Research/Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Jan Borén
- From the Sahlgrenska Center for Cardiovascular and Metabolic Research/Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| |
Collapse
|
44
|
Fisher EA. The degradation of apolipoprotein B100: multiple opportunities to regulate VLDL triglyceride production by different proteolytic pathways. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:778-81. [PMID: 22342675 DOI: 10.1016/j.bbalip.2012.02.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 02/02/2012] [Accepted: 02/02/2012] [Indexed: 12/12/2022]
Abstract
Very low density lipoproteins (VLDL) are a major secretory product of the liver. They serve to transport endogenously synthesized lipids, mainly triglycerides (but also some cholesterol and cholesteryl esters) to peripheral tissues. VLDL is also the precursor of LDL. ApoB100 is absolutely required for VLDL assembly and secretion. The amount of VLDL triglycerides secreted by the liver depends on the amount loaded onto each lipoprotein particle, as well as the number of particles. Each VLDL has one apoB100 molecule, making apoB100 availability a key determinant of the number of VLDL particles, and hence, triglycerides, that can be secreted by hepatic cells. Surprisingly, the pool of apoB100 in the liver is typically regulated not by its level of synthesis, which is relatively constant, but by its level of degradation. It is now recognized that there are multiple opportunities for the hepatic cell to intercept apoB100 molecules and to direct them to distinct degradative processes. This mini-review will summarize progress in understanding these processes, with an emphasis on autophagy, the most recently described pathway of apoB100 degradation, and the one with possibly the most physiologic relevance to common metabolic perturbations affecting VLDL production. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.
Collapse
Affiliation(s)
- Edward A Fisher
- The Department of Medicine (Cardiology) and the Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, Smilow 7, 522 First Avenue, New York, NY 10016, USA.
| |
Collapse
|
45
|
Suzuki M, Otsuka T, Ohsaki Y, Cheng J, Taniguchi T, Hashimoto H, Taniguchi H, Fujimoto T. Derlin-1 and UBXD8 are engaged in dislocation and degradation of lipidated ApoB-100 at lipid droplets. Mol Biol Cell 2012; 23:800-10. [PMID: 22238364 PMCID: PMC3290640 DOI: 10.1091/mbc.e11-11-0950] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Apolipoprotein B-100 after lipidation is dislocated from the ER lumen to the cytoplasmic surface of lipid droplets for proteasomal degradation. UBXD8 in lipid droplets and Derlin-1 in the ER membrane interact with each other and with ApoB and are engaged in the pre- and postdislocation steps, respectively. Apolipoprotein B-100 (ApoB) is the principal component of very low density lipoprotein. Poorly lipidated nascent ApoB is extracted from the Sec61 translocon and degraded by proteasomes. ApoB lipidated in the endoplasmic reticulum (ER) lumen is also subjected to proteasomal degradation, but where and how it dislocates to the cytoplasm remain unknown. In the present study, we demonstrate that ApoB after lipidation is dislocated to the cytoplasmic surface of lipid droplets (LDs) and accumulates as ubiquitinated ApoB in Huh7 cells. Depletion of UBXD8, which is almost confined to LDs in this cell type, decreases recruitment of p97 to LDs and causes an increase of both ubiquitinated ApoB on the LD surface and lipidated ApoB in the ER lumen. In contrast, abrogation of Derlin-1 function induces an accumulation of lipidated ApoB in the ER lumen but does not increase ubiquitinated ApoB on the LD surface. UBXD8 and Derlin-1 bind with each other and with lipidated ApoB and show colocalization around LDs. These results indicate that ApoB after lipidation is dislocated from the ER lumen to the LD surface for proteasomal degradation and that Derlin-1 and UBXD8 are engaged in the predislocation and postdislocation steps, respectively.
Collapse
Affiliation(s)
- Michitaka Suzuki
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa, Nagoya 466-8550, Japan
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Grubb S, Guo L, Fisher EA, Brodsky JL. Protein disulfide isomerases contribute differentially to the endoplasmic reticulum-associated degradation of apolipoprotein B and other substrates. Mol Biol Cell 2011; 23:520-32. [PMID: 22190736 PMCID: PMC3279382 DOI: 10.1091/mbc.e11-08-0704] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
ER-associated degradation (ERAD) rids the early secretory pathway of misfolded or misprocessed proteins. Some members of the protein disulfide isomerase (PDI) family appear to facilitate ERAD substrate selection and retrotranslocation, but a thorough characterization of PDIs during the degradation of diverse substrates has not been undertaken, in part because there are 20 PDI family members in mammals. PDIs can also exhibit disulfide redox, isomerization, and/or chaperone activity, but which of these activities is required for the ERAD of different substrate classes is unknown. We therefore examined the fates of unique substrates in yeast, which expresses five PDIs. Through the use of a yeast expression system for apolipoprotein B (ApoB), which is disulfide rich, we discovered that Pdi1 interacts with ApoB and facilitates degradation through its chaperone activity. In contrast, Pdi1's redox activity was required for the ERAD of CPY* (a misfolded version of carboxypeptidase Y that has five disulfide bonds). The ERAD of another substrate, the alpha subunit of the epithelial sodium channel, was Pdi1 independent. Distinct effects of mammalian PDI homologues on ApoB degradation were then observed in hepatic cells. These data indicate that PDIs contribute to the ERAD of proteins through different mechanisms and that PDI diversity is critical to recognize the spectrum of potential ERAD substrates.
Collapse
Affiliation(s)
- Sarah Grubb
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | | | | | | |
Collapse
|
47
|
Choi SH, Ginsberg HN. Increased very low density lipoprotein (VLDL) secretion, hepatic steatosis, and insulin resistance. Trends Endocrinol Metab 2011; 22:353-63. [PMID: 21616678 PMCID: PMC3163828 DOI: 10.1016/j.tem.2011.04.007] [Citation(s) in RCA: 249] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 04/18/2011] [Accepted: 04/19/2011] [Indexed: 12/14/2022]
Abstract
Insulin resistance (IR) affects not only the regulation of carbohydrate metabolism but all aspects of lipid and lipoprotein metabolism. IR is associated with increased secretion of VLDL and increased plasma triglycerides, as well as with hepatic steatosis, despite the increased VLDL secretion. Here we link IR with increased VLDL secretion and hepatic steatosis at both the physiologic and molecular levels. Increased VLDL secretion, together with the downstream effects on high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) size, is proatherogenic. Hepatic steatosis is a risk factor for steatohepatitis and cirrhosis. Understanding the complex inter-relationships between IR and these abnormalities of liver lipid homeostasis will provide insights relevant to new therapies for these increasing clinical problems.
Collapse
Affiliation(s)
- Sung Hee Choi
- Internal Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seoul, Korea
| | - Henry N Ginsberg
- Columbia University College of Physicians and Surgeons, New York, NY, USA
- whom correspondence should be addressed.
| |
Collapse
|
48
|
Quantity control of the ErbB3 receptor tyrosine kinase at the endoplasmic reticulum. Mol Cell Biol 2011; 31:3009-18. [PMID: 21576364 DOI: 10.1128/mcb.05105-11] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ErbB3 receptor tyrosine kinase contributes to a variety of developmental processes, and its overexpression and aberrant activation promote tumor progression and therapeutic resistance. Accumulating evidence suggests that tumor overexpression may be mediated by the loss of posttranscriptional negative regulatory mechanisms, such as protein degradation, that normally keep receptor levels in check. Our previous studies indicate that the RING finger E3 ubiquitin ligase Nrdp1, a protein lost in breast and other tumor types, suppresses ErbB3 levels by mediating ligand-independent receptor ubiquitination and degradation. Here we demonstrate that Nrdp1 preferentially associates with the nascent form of ErbB3 to accelerate its degradation, and we show that the two proteins colocalize at the endoplasmic reticulum (ER). Blocking the exit of ErbB3 from the ER does not affect the ability of Nrdp1 to mediate receptor ubiquitination or degradation, while functional disruption of the conserved ER-associated degradation (ERAD) pathway ATPase VCP/p97 leads to the Nrdp1-dependent accumulation of ubiquitinated ErbB3 but blocks receptor degradation. Further evidence indicates that the ErbB3 targeted by Nrdp1 for degradation is properly folded and fully functional. Collectively, these observations point to a novel mechanism of receptor tyrosine kinase quantity control wherein steady-state levels of signaling-competent receptor are dictated by an ER-localized degradation pathway.
Collapse
|
49
|
Abstract
PURPOSE OF REVIEW To discuss transcriptional mechanisms regulating hepatic lipid metabolism. RECENT FINDINGS Humans who are obese or have diabetes (NIDDM) or metabolic syndrome (MetS) have low blood and tissue levels of C20-22 polyunsaturated fatty acids (PUFAs). Although the impact of low C20-22 PUFAs on disease progression in humans is not fully understood, studies with mice have provided clues suggesting that impaired PUFA metabolism may contribute to the severity of risk factors associated with NIDDM and MetS. High fat diets promote hyperglycemia, insulin resistance and fatty liver in C57BL/6J mice, an effect that correlates with suppressed expression of enzymes involved in PUFA synthesis and decreased hepatic C20-22 PUFA content. A/J mice, in contrast, are resistant to diet-induced obesity and diabetes; these mice have elevated expression of hepatic enzymes involved in PUFA synthesis and C20-22 PUFA content. Moreover, loss-of-function and gain-of-function studies have identified fatty acid elongase (Elovl5), a key enzyme involved in PUFA synthesis, as a regulator of hepatic lipid and carbohydrate metabolism. Elovl5 activity regulates hepatic C20-22 PUFA content, signaling pathways (Akt and PP2A) and transcription factors (SREBP-1, PPARα, FoxO1 and PGC1α) that control fatty acid synthesis and gluconeogenesis. SUMMARY These studies may help define novel strategies to control fatty liver and hyperglycemia associated with NIDDM and MetS.
Collapse
Affiliation(s)
- Donald B Jump
- Department of Nutrition and Exercise Sciences, The Linus Pauling Institute, Oregon State University, Corvallis, Oregon 97331, USA.
| |
Collapse
|
50
|
|