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Mu W, Zhi Y, Zhou J, Wang C, Chai K, Fan Z, Lv G. Endoplasmic reticulum stress and quality control in relation to cisplatin resistance in tumor cells. Front Pharmacol 2024; 15:1419468. [PMID: 38948460 PMCID: PMC11211601 DOI: 10.3389/fphar.2024.1419468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Accepted: 05/29/2024] [Indexed: 07/02/2024] Open
Abstract
The endoplasmic reticulum (ER) is a crucial organelle that orchestrates key cellular functions like protein folding and lipid biosynthesis. However, it is highly sensitive to disturbances that lead to ER stress. In response, the unfolded protein response (UPR) activates to restore ER homeostasis, primarily through three sensors: IRE1, ATF6, and PERK. ERAD and autophagy are crucial in mitigating ER stress, yet their dysregulation can lead to the accumulation of misfolded proteins. Cisplatin, a commonly used chemotherapy drug, induces ER stress in tumor cells, activating complex signaling pathways. Resistance to cisplatin stems from reduced drug accumulation, activation of DNA repair, and anti-apoptotic mechanisms. Notably, cisplatin-induced ER stress can dualistically affect tumor cells, promoting either survival or apoptosis, depending on the context. ERAD is crucial for degrading misfolded proteins, whereas autophagy can protect cells from apoptosis or enhance ER stress-induced apoptosis. The complex interaction between ER stress, cisplatin resistance, ERAD, and autophagy opens new avenues for cancer treatment. Understanding these processes could lead to innovative strategies that overcome chemoresistance, potentially improving outcomes of cisplatin-based cancer treatments. This comprehensive review provides a multifaceted perspective on the complex mechanisms of ER stress, cisplatin resistance, and their implications in cancer therapy.
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Affiliation(s)
| | | | | | | | | | - Zhongqi Fan
- Department of Hepatobiliary and Pancreatic Surgery, General Surgery Center, First Hospital of Jilin University, Changchun, Jilin, China
| | - Guoyue Lv
- Department of Hepatobiliary and Pancreatic Surgery, General Surgery Center, First Hospital of Jilin University, Changchun, Jilin, China
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2
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Desrochers GF, Filip R, Bastianelli M, Stern T, Pezacki JP. microRNA-27b regulates hepatic lipase enzyme LIPC and reduces triglyceride degradation during hepatitis C virus infection. J Biol Chem 2022; 298:101983. [PMID: 35483451 PMCID: PMC9163519 DOI: 10.1016/j.jbc.2022.101983] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 03/24/2022] [Accepted: 03/26/2022] [Indexed: 11/26/2022] Open
Abstract
miRNAs are short, noncoding RNAs that negatively and specifically regulate protein expression, the cumulative effects of which can result in broad changes to cell systems and architecture. The miRNA miR-27b is known to regulate lipid regulatory pathways in the human liver and is also induced by the hepatitis C virus (HCV). However, the functional targets of miR-27b are not well established. Herein, an activity-based protein profiling method using a serine hydrolase probe, coupled with stable isotope labeling and mass spectrometry identified direct and indirect targets of miR-27b. The hepatic lipase C (LIPC) stood out as both highly dependent on miR-27b and as a major modulator of lipid pathway misregulation. Modulation of miR-27b using both exogenous miRNA mimics and inhibitors demonstrated that transcription factors Jun, PPARα, and HNF4α, all of which also influence LIPC levels and activity, are regulated by miR-27b. LIPC was furthermore shown to affect the progress of the life cycle of HCV and to decrease levels of intracellular triglycerides, upon which HCV is known to depend. In summary, this work has demonstrated that miR-27b mediates HCV infection by downregulating LIPC, thereby reducing triglyceride degradation, which in turn increases cellular lipid levels.
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Affiliation(s)
| | - Roxana Filip
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada
| | - Micheal Bastianelli
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada
| | - Tiffany Stern
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada
| | - John Paul Pezacki
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada; Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada.
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3
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Koerner CM, Roberts BS, Neher SB. Endoplasmic reticulum quality control in lipoprotein metabolism. Mol Cell Endocrinol 2019; 498:110547. [PMID: 31442546 PMCID: PMC6814580 DOI: 10.1016/j.mce.2019.110547] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 08/16/2019] [Accepted: 08/17/2019] [Indexed: 12/26/2022]
Abstract
Lipids play a critical role in energy metabolism, and a suite of proteins is required to deliver lipids to tissues. Several of these proteins require an intricate endoplasmic reticulum (ER) quality control (QC) system and unique secondary chaperones for folding. Key examples include apolipoprotein B (apoB), which is the primary scaffold for many lipoproteins, dimeric lipases, which hydrolyze triglycerides from circulating lipoproteins, and the low-density lipoprotein receptor (LDLR), which clears cholesterol-rich lipoproteins from the circulation. ApoB requires specialized proteins for lipidation, dimeric lipases lipoprotein lipase (LPL) and hepatic lipase (HL) require a transmembrane maturation factor for secretion, and the LDLR requires several specialized, domain-specific chaperones. Deleterious mutations in these proteins or their chaperones may result in dyslipidemias, which are detrimental to human health. Here, we review the ER quality control systems that ensure secretion of apoB, LPL, HL, and LDLR with a focus on the specialized chaperones required by each protein.
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Affiliation(s)
- Cari M Koerner
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, USA
| | - Benjamin S Roberts
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, USA
| | - Saskia B Neher
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, USA.
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4
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Geldenhuys WJ, Lin L, Darvesh AS, Sadana P. Emerging strategies of targeting lipoprotein lipase for metabolic and cardiovascular diseases. Drug Discov Today 2016; 22:352-365. [PMID: 27771332 DOI: 10.1016/j.drudis.2016.10.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 09/17/2016] [Accepted: 10/12/2016] [Indexed: 12/12/2022]
Abstract
Although statins and other pharmacological approaches have improved the management of lipid abnormalities, there exists a need for newer treatment modalities especially for the management of hypertriglyceridemia. Lipoprotein lipase (LPL), by promoting hydrolytic cleavage of the triglyceride core of lipoproteins, is a crucial node in the management of plasma lipid levels. Although LPL expression and activity modulation is observed as a pleiotropic action of some the commonly used lipid lowering drugs, the deliberate development of drugs targeting LPL has not occurred yet. In this review, we present the biology of LPL, highlight the LPL modulation property of currently used drugs and review the novel emerging approaches to target LPL.
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Affiliation(s)
- Werner J Geldenhuys
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26505, USA
| | - Li Lin
- Department of Pharmaceutical Sciences, College of Pharmacy, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272, USA
| | - Altaf S Darvesh
- Department of Pharmaceutical Sciences, College of Pharmacy, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272, USA
| | - Prabodh Sadana
- Department of Pharmaceutical Sciences, College of Pharmacy, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272, USA.
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Guo J, Zhang Y, Mihic A, Li SH, Sun Z, Shao Z, Wu J, Weisel RD, Li RK. A secreted protein (Canopy 2, CNPY2) enhances angiogenesis and promotes smooth muscle cell migration and proliferation. Cardiovasc Res 2015; 105:383-393. [DOI: 10.1093/cvr/cvv010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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Mao HZ, Ehrhardt N, Bedoya C, Gomez JA, DeZwaan-McCabe D, Mungrue IN, Kaufman RJ, Rutkowski DT, Péterfy M. Lipase maturation factor 1 (lmf1) is induced by endoplasmic reticulum stress through activating transcription factor 6α (Atf6α) signaling. J Biol Chem 2014; 289:24417-27. [PMID: 25035425 PMCID: PMC4148868 DOI: 10.1074/jbc.m114.588764] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Indexed: 11/06/2022] Open
Abstract
Lipase maturation factor 1 (Lmf1) is a critical determinant of plasma lipid metabolism, as demonstrated by severe hypertriglyceridemia associated with its mutations in mice and human subjects. Lmf1 is a chaperone localized to the endoplasmic reticulum (ER) and required for the post-translational maturation and activation of several vascular lipases. Despite its importance in plasma lipid homeostasis, the regulation of Lmf1 remains unexplored. We report here that Lmf1 expression is induced by ER stress in various cell lines and in tunicamycin (TM)-injected mice. Using genetic deficiencies in mouse embryonic fibroblasts and mouse liver, we identified the Atf6α arm of the unfolded protein response as being responsible for the up-regulation of Lmf1 in ER stress. Experiments with luciferase reporter constructs indicated that ER stress activates the Lmf1 promoter through a GC-rich DNA sequence 264 bp upstream of the transcriptional start site. We demonstrated that Atf6α is sufficient to induce the Lmf1 promoter in the absence of ER stress, and this effect is mediated by the TM-responsive cis-regulatory element. Conversely, Atf6α deficiency induced by genetic ablation or a dominant-negative form of Atf6α abolished TM stimulation of the Lmf1 promoter. In conclusion, our results indicate that Lmf1 is an unfolded protein response target gene, and Atf6α signaling is sufficient and necessary for activation of the Lmf1 promoter. Importantly, the induction of Lmf1 by ER stress appears to be a general phenomenon not restricted to lipase-expressing cells, which suggests a lipase-independent cellular role for this protein in ER homeostasis.
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Affiliation(s)
- Hui Z Mao
- From the Medical Genetics Research Institute and
| | | | - Candy Bedoya
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California 90048
| | - Javier A Gomez
- Department of Anatomy and Cell Biology and Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Diane DeZwaan-McCabe
- Department of Anatomy and Cell Biology and Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Imran N Mungrue
- the Department of Pharmacology and Experimental Therapeutics, Louisiana State University School of Medicine, New Orleans, Louisiana 70112
| | - Randal J Kaufman
- Degenerative Disease Research, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, and
| | - D Thomas Rutkowski
- Department of Anatomy and Cell Biology and Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Miklós Péterfy
- From the Medical Genetics Research Institute and Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California 90048, the Department of Medicine, David Geffen School of Medicine at the University of California, Los Angeles, California 90095
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7
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Bamji-Mirza M, Zhang W, Yao Z. Expression of human hepatic lipase negatively impacts apolipoprotein A-I production in primary hepatocytes from Lipc-null mice. J Biomed Res 2014; 28:201-12. [PMID: 25013403 PMCID: PMC4085557 DOI: 10.7555/jbr.28.20130184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Revised: 12/28/2013] [Accepted: 02/22/2014] [Indexed: 11/22/2022] Open
Abstract
This study aimed to examine whether expression of human hepatic lipase (hHL) exerted an intracellular effect on hepatic production of apolipoprotein (apo) A-I. The levels of secreted and cell-associated apoA-I were contrasted between primary hepatocytes isolated from Lipc-null and C57BL/6 mice, and between Lipc-null hepatocytes transfected with either hHL-encoding or control adenovirus. An HSPG-binding deficient hHL protein (hHLmt) was used to determine the impact of cell surface binding on HL action. Accumulation of apoA-I in conditioned media of primary hepatocytes isolated from Lipc-null mice was increased as compared to that from C57BL/6 mice. Metabolic labeling experiments showed that secretion of 35S-apoA-I from Lipc-null cells was significantly higher than that from C57BL/6 cells. Expression of hHL in Lipc-null hepatocytes, through adenovirus-mediated gene transfer, resulted in decreased synthesis and secretion of 35S-apoA-I, but not 35S-apoE, as compared with cells transfected with control adenovirus. Expression of HSPG-binding deficient hHLmt in Lipc-null cells also exerted an inhibitory effect on apoA-I production, even though hHLmt displayed impaired exit from the endoplasmic reticulum as compared with hHL. Subcellular fractionation revealed that expression of hHL or hHLmt led to increased microsome-association of apoA-I relative to non-transfected control. Expression of hHL negatively impacts hepatic production of apoA-I.
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Affiliation(s)
- Michelle Bamji-Mirza
- Department of Biochemistry, Microbiology & Immunology, and ; Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada; ; Human Health Therapeutics Portfolio, Life Sciences Division, National Research Council Canada, Ottawa, Ontario, K1A 0R6, Canada
| | - Wandong Zhang
- Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada; ; Human Health Therapeutics Portfolio, Life Sciences Division, National Research Council Canada, Ottawa, Ontario, K1A 0R6, Canada
| | - Zemin Yao
- Department of Biochemistry, Microbiology & Immunology, and ; Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada
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8
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Vagin O, Tokhtaeva E, Garay PE, Souda P, Bassilian S, Whitelegge JP, Lewis R, Sachs G, Wheeler L, Aoki R, Fernandez-Salas E. Recruitment of septin cytoskeletal proteins by botulinum toxin A protease determines its remarkable stability. J Cell Sci 2014; 127:3294-308. [PMID: 24928902 DOI: 10.1242/jcs.146324] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Proteolytic cleavage of synaptosomal-associated protein 25 by the light chain of botulinum neurotoxin type A (LCA) results in a blockade of neurotransmitter release that persists for several months in motor neurons. The L428A/L429A mutation in LCA is known to significantly shorten both the proteolytic and neuroparalytic effects of the neurotoxin in mice. To elucidate the cellular mechanism for LCA longevity, we studied the effects of L428A/L429A mutation on the interactome, localization and stability of LCA expressed in cultured neuronal cells. Mass spectrometry analysis of the LCA interactome showed that the mutation prevented the interaction of LCA with septins. The wild-type LCA was concentrated in plasma-membrane-associated clusters, colocalizing with septins-2 and septin-7, which accumulated in these clusters only in the presence of LCA. The L428A/L429A mutation decreased co-clustering of LCA and septins and accelerated proteasomal and non-proteasomal degradation of LCA. Similarly, the impairment of septin oligomerization by forchlorfenuron or silencing of septin-2 prevented LCA interaction and clustering with septins and increased LCA degradation. Therefore, the dileucine-mediated LCA-septin co-clustering is crucial for the long-lasting stabilization of LCA-related proteolytic and presumably neuroparalytic activity.
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Affiliation(s)
- Olga Vagin
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA 91343, USA
| | - Elmira Tokhtaeva
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA 91343, USA
| | - Patton E Garay
- Department of Biological Sciences, Allergan Inc., Irvine, CA 92612, USA
| | - Puneet Souda
- The NPI-Semel Institute, Pasarow Mass Spectrometry Laboratory, UCLA, Los Angeles, CA 90095, USA
| | - Sara Bassilian
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA 91343, USA
| | - Julian P Whitelegge
- The NPI-Semel Institute, Pasarow Mass Spectrometry Laboratory, UCLA, Los Angeles, CA 90095, USA
| | - Ramilla Lewis
- Department of Biological Sciences, Allergan Inc., Irvine, CA 92612, USA
| | - George Sachs
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA 91343, USA
| | - Larry Wheeler
- Department of Biological Sciences, Allergan Inc., Irvine, CA 92612, USA
| | - Roger Aoki
- Department of Biological Sciences, Allergan Inc., Irvine, CA 92612, USA
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9
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Hosseini M, Ehrhardt N, Weissglas-Volkov D, Lai CM, Mao HZ, Liao JL, Nikkola E, Bensadoun A, Taskinen MR, Doolittle MH, Pajukanta P, Péterfy M. Transgenic expression and genetic variation of Lmf1 affect LPL activity in mice and humans. Arterioscler Thromb Vasc Biol 2012; 32:1204-10. [PMID: 22345169 DOI: 10.1161/atvbaha.112.245696] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Lipoprotein lipase (LPL) is a principal enzyme in lipoprotein metabolism, tissue lipid utilization, and energy metabolism. LPL is synthesized by parenchymal cells in adipose, heart, and muscle tissues followed by secretion to extracellular sites, where lipolyic function is exerted. The catalytic activity of LPL is attained during posttranslational maturation, which involves glycosylation, folding, and subunit assembly within the endoplasmic reticulum. A lipase-chaperone, lipase maturation factor 1 (Lmf1), has recently emerged as a critical factor in this process. Previous studies demonstrated that loss-of-function mutations of Lmf1 result in diminished lipase activity and severe hypertriglyceridemia in mice and human subjects. The objective of this study is to investigate whether, beyond its role as a required factor in lipase maturation, variation in Lmf1 expression is sufficient to modulate LPL activity in vivo. METHODS AND RESULTS To assess the effects of Lmf1 overexpression in adipose and muscle tissues, we generated aP2-Lmf1 and Mck-Lmf1 transgenic mice. Characterization of relevant tissues revealed increased LPL activity in both mouse strains. In the omental and subcutaneous adipose depots, Lmf1 overexpression was associated with increased LPL specific activity without changes in LPL mass. In contrast, increased LPL activity was due to elevated LPL protein level in heart and gonadal adipose tissue. To extend these studies to humans, we detected association between LMF1 gene variants and postheparin LPL activity in a dyslipidemic cohort. CONCLUSIONS Our results suggest that variation in Lmf1 expression is a posttranslational determinant of LPL activity.
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Affiliation(s)
- Maryam Hosseini
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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Glahn DC, Curran JE, Winkler AM, Carless MA, Kent JW, Charlesworth JC, Johnson MP, Göring HHH, Cole SA, Dyer TD, Moses EK, Olvera RL, Kochunov P, Duggirala R, Fox PT, Almasy L, Blangero J. High dimensional endophenotype ranking in the search for major depression risk genes. Biol Psychiatry 2012; 71:6-14. [PMID: 21982424 PMCID: PMC3230692 DOI: 10.1016/j.biopsych.2011.08.022] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 08/24/2011] [Accepted: 08/25/2011] [Indexed: 11/26/2022]
Abstract
BACKGROUND Despite overwhelming evidence that major depression is highly heritable, recent studies have localized only a single depression-related locus reaching genome-wide significance and have yet to identify a causal gene. Focusing on family-based studies of quantitative intermediate phenotypes or endophenotypes, in tandem with studies of unrelated individuals using categorical diagnoses, should improve the likelihood of identifying major depression genes. However, there is currently no empirically derived statistically rigorous method for selecting optimal endophentypes for mental illnesses. Here, we describe the endophenotype ranking value, a new objective index of the genetic utility of endophenotypes for any heritable illness. METHODS Applying endophenotype ranking value analysis to a high-dimensional set of over 11,000 traits drawn from behavioral/neurocognitive, neuroanatomic, and transcriptomic phenotypic domains, we identified a set of objective endophenotypes for recurrent major depression in a sample of Mexican American individuals (n = 1122) from large randomly selected extended pedigrees. RESULTS Top-ranked endophenotypes included the Beck Depression Inventory, bilateral ventral diencephalon volume, and expression levels of the RNF123 transcript. To illustrate the utility of endophentypes in this context, each of these traits were utlized along with disease status in bivariate linkage analysis. A genome-wide significant quantitative trait locus was localized on chromsome 4p15 (logarithm of odds = 3.5) exhibiting pleiotropic effects on both the endophenotype (lymphocyte-derived expression levels of the RNF123 gene) and disease risk. CONCLUSIONS The wider use of quantitative endophenotypes, combined with unbiased methods for selecting among these measures, should spur new insights into the biological mechanisms that influence mental illnesses like major depression.
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Affiliation(s)
- David C Glahn
- Olin Neuropsychiatry Research Center, Institute of Living, Hartford Hospital, 200 Retreat Avenue, Hartford, CT 06106, USA.
| | - Joanne E Curran
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Anderson M Winkler
- Olin Neuropsychiatry Research Center, Institute of Living, Hartford Hospital, 200 Retreat Avenue, CT, 06106, USA,Department of Psychiatry, Yale University School of Medicine, 300 George Street, New Haven, CT, 06511, USA
| | - Melanie A Carless
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Jack W Kent
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Jac C Charlesworth
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Matthew P Johnson
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Harald HH Göring
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Shelley A Cole
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Thomas D Dyer
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Eric K Moses
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Rene L Olvera
- Department of Psychiatry, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Peter Kochunov
- Research Imaging Institute, University of Texas Health Science Center San Antonio, 8403 Floyd Curl Dr, San Antonio, TX, 78229, USA
| | - Ravi Duggirala
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - Peter T Fox
- Research Imaging Institute, University of Texas Health Science Center San Antonio, 8403 Floyd Curl Dr, San Antonio, TX, 78229, USA
| | - Laura Almasy
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
| | - John Blangero
- Department of Genetics, Texas Biomedical Research Institute, PO Box 760549, San Antonio, TX, 78245 USA
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Péterfy M. Lipase maturation factor 1: a lipase chaperone involved in lipid metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:790-4. [PMID: 22063272 DOI: 10.1016/j.bbalip.2011.10.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 10/03/2011] [Accepted: 10/04/2011] [Indexed: 10/16/2022]
Abstract
Mutations in lipase maturation factor 1 (LMF1) are associated with severe hypertriglyceridemia in mice and human subjects. The underlying cause is impaired lipid clearance due to lipase deficiency. LMF1 is a chaperone of the endoplasmic reticulum (ER) and it is critically required for the post-translational activation of three vascular lipases: lipoprotein lipase (LPL), hepatic lipase (HL) and endothelial lipase (EL). As LMF1 is only required for the maturation of homodimeric, but not monomeric, lipases, it is likely involved in the assembly of inactive lipase subunits into active enzymes and/or the stabilization of active dimers. Herein, we provide an overview of current understanding of LMF1 function and propose that it may play a regulatory role in lipase activation and lipid metabolism. Further studies will be required to test this hypothesis and elucidate the full spectrum of phenotypes in combined lipase deficiency. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.
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Affiliation(s)
- Miklós Péterfy
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States.
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12
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Tokhtaeva E, Sachs G, Souda P, Bassilian S, Whitelegge JP, Shoshani L, Vagin O. Epithelial junctions depend on intercellular trans-interactions between the Na,K-ATPase β₁ subunits. J Biol Chem 2011; 286:25801-12. [PMID: 21642423 DOI: 10.1074/jbc.m111.252247] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
N-Glycans of the Na,K-ATPase β₁ subunit are important for intercellular adhesion in epithelia, suggesting that epithelial junctions depend on N-glycan-mediated interactions between the β₁ subunits of neighboring cells. The level of co-immunoprecipitation of the endogenous β₁ subunit with various YFP-linked β₁ subunits expressed in Madin-Darby canine kidney cells was used to assess β₁-β₁ interactions. The amount of co-precipitated endogenous dog β₁ was greater with dog YFP-β₁ than with rat YFP-β₁, showing that amino acid-mediated interactions are important for β₁-β₁ binding. Co-precipitation of β₁ was also less with the unglycosylated YFP-β₁ than with glycosylated YFP-β₁, indicating a role for N-glycans. Mixing cells expressing dog YFP-β₁ with non-transfected cells increased the amount of co-precipitated β₁, confirming the presence of intercellular (YFP-β₁)-β₁ complexes. Accordingly, disruption of intercellular junctions decreased the amount of co-precipitated β₁ subunits. The decrease in β₁ co-precipitation both with rat YFP-β₁ and unglycosylated YFP-β₁ was associated with decreased detergent stability of junctional proteins and increased paracellular permeability. Reducing N-glycan branching by specific inhibitors increased (YFP-β₁)-β₁ co-precipitation and strengthened intercellular junctions. Therefore, interactions between the β₁ subunits of neighboring cells maintain integrity of intercellular junctions, and alterations in the β₁ subunit N-glycan structure can regulate stability and tightness of intercellular junctions.
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Affiliation(s)
- Elmira Tokhtaeva
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, California 90073, USA
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Ben-Zeev O, Hosseini M, Lai CM, Ehrhardt N, Wong H, Cefalù AB, Noto D, Averna MR, Doolittle MH, Péterfy M. Lipase maturation factor 1 is required for endothelial lipase activity. J Lipid Res 2011; 52:1162-1169. [PMID: 21447484 DOI: 10.1194/jlr.m011155] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Lipase maturation factor 1 (Lmf1) is an endoplasmic reticulum (ER) membrane protein involved in the posttranslational folding and/or assembly of lipoprotein lipase (LPL) and hepatic lipase (HL) into active enzymes. Mutations in Lmf1 are associated with diminished LPL and HL activities ("combined lipase deficiency") and result in severe hypertriglyceridemia in mice as well as in human subjects. Here, we investigate whether endothelial lipase (EL) also requires Lmf1 to attain enzymatic activity. We demonstrate that cells harboring a (cld) loss-of-function mutation in the Lmf1 gene are unable to generate active EL, but they regain this capacity after reconstitution with the Lmf1 wild type. Furthermore, we show that cellular EL copurifies with Lmf1, indicating their physical interaction in the ER. Finally, we determined that post-heparin phospholipase activity in a patient with the LMF1(W464X) mutation is reduced by more than 95% compared with that in controls. Thus, our study indicates that EL is critically dependent on Lmf1 for its maturation in the ER and demonstrates that Lmf1 is a required factor for all three vascular lipases, LPL, HL, and EL.
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Affiliation(s)
- Osnat Ben-Zeev
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA
| | - Maryam Hosseini
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA; Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Ching-Mei Lai
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA
| | - Nicole Ehrhardt
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Howard Wong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA
| | - Angelo B Cefalù
- Department of Clinical Medicine and Emerging Diseases, University of Palermo, Palermo, Italy
| | - Davide Noto
- Department of Clinical Medicine and Emerging Diseases, University of Palermo, Palermo, Italy
| | - Maurizio R Averna
- Department of Clinical Medicine and Emerging Diseases, University of Palermo, Palermo, Italy
| | - Mark H Doolittle
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA
| | - Miklós Péterfy
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA; Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA.
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14
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Bamji-Mirza M, Sundaram M, Zhong S, Yao EF, Parks RJ, Yao Z. Secretion of triacylglycerol-poor VLDL particles from McA-RH7777 cells expressing human hepatic lipase. J Lipid Res 2010; 52:540-8. [PMID: 21189265 DOI: 10.1194/jlr.m012476] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hepatic lipase (HL) plays a role in the catabolism of apolipoprotein (apo)B-containing lipoproteins through its lipolytic and ligand-binding properties. We describe a potential intracellular role of HL in the assembly and secretion of VLDL. Transient or stable expression of HL in McA-RH7777 cells resulted in decreased (by 40%) incorporation of [(3)H]glycerol into cell-associated and secreted triacylglycerol (TAG) relative to control cells. However, incorporation of [(35)S]methionine/cysteine into cell and medium apoB-100 was not decreased by HL expression. The decreased (3)H-TAG synthesis/secretion in HL expressing cells was not attributable to decreased expression of genes involved in lipogenesis. Fractionation of medium revealed that the decreased [(3)H]TAG from HL expressing cells was mainly attributable to decreased VLDL. Expression of catalytically-inactive HL (HL(SG)) (Ser-145 at the catalytic site was substituted with Gly) in the cells also resulted in decreased secretion of VLDL-[(3)H]TAG. Examination of lumenal contents of microsomes showed a 40% decrease in [(3)H]TAG associated with lumenal lipid droplets in HL or HL(SG) expressing cells as compared with control. The microsomal membrane-associated [(3)H]TAG was decreased by 50% in HL expressing cells but not in HL(SG) expressing cells. Thus, expression of HL, irrespective of its lipolytic function, impairs formation of VLDL precursor [(3)H]TAG in the form of lumenal lipid droplets. These results suggest that HL expression in McA-RH7777 cells result in secretion of [(3)H]TAG-poor VLDL.
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Affiliation(s)
- Michelle Bamji-Mirza
- Department of Biochemistry, Microbiology & Immunology, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Canada, K1H 8M5
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15
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Abstract
PURPOSE OF REVIEW There are strong epidemiologic connections between plasma triglycerides and atherosclerosis. We will consider to what extent this goes back to derangements of the lipoprotein lipase (LPL) system. The roles of hepatic lipase and endothelial lipase will also be touched upon. RECENT FINDINGS Understanding of LPL action has taken major steps with the discovery of lipase maturation factor 1 as a specific endoplasmic reticulum chaperon needed for proper folding of the lipases, glycosylphosphatidylinositol-anchored HDL-binding protein 1 as an endothelial cell protein needed for transport and binding of LPL and some angiopoietin-like proteins that can modulate LPL activity. Studies of genetic variants continue to support the important roles of the lipases in lipoprotein metabolism and in atherosclerosis. CONCLUSION There are several ways by which derangement of the lipases may contribute to atherogenesis. Lipase actions are major determinants of plasma lipoprotein patterns. LPL activity must be modulated in relation to the physiological situation (feeding, fasting, exercise, etc.). Fatty acids and monoglycerides generated must be efficiently removed so that they do not endanger the integrity of the endothelium, cause lipotoxic reactions or both. In addition, the lipases may cause binding and endocytosis of lipoprotein particles in the artery wall.
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Affiliation(s)
- Gunilla Olivecrona
- Department of Medical Biosciences, Section on Physiological Chemistry, Umeå University, Umeå, Sweden.
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16
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Abstract
PURPOSE OF REVIEW Lipase maturation factor 1 (LMF1) is a membrane-bound protein located in the endoplasmic reticulum. It is essential to the folding and assembly (i.e., maturation) of a selected group of lipases that include lipoprotein lipase, hepatic lipase and endothelial lipase. The purpose of this review is to examine recent studies that have begun to elucidate the structure and function of LMF1 and to place it in the context of lipase folding and assembly. RECENT FINDINGS Recent studies identified mutations in LMF1 that cause combined lipase deficiency and hypertriglyceridemia in humans. These mutations result in the truncation of a large, evolutionarily conserved domain (DUF1222), which is essential for interaction with lipases and their attainment of enzymatic activity. The structural complexity of LMF1 has been further characterized by solving its topology in the endoplasmic reticulum membrane. Recent studies indicate that in addition to lipoprotein lipase and hepatic lipase, the maturation of endothelial lipase is also dependent on LMF1. Based on its apparent specificity for dimeric lipases, LMF1 is proposed to play an essential role in the assembly and/or stabilization of head-to-tail lipase homodimers. SUMMARY LMF1 functions in the maturation of a selected group of secreted lipases that assemble into homodimers in the endoplasmic reticulum. These dimeric lipases include lipoprotein lipase, hepatic lipase and endothelial lipase, all of which contribute significantly to plasma triglyceride and high-density lipoprotein cholesterol levels in humans. Future studies involving genetically engineered mouse models will be required to fully elucidate the role of LMF1 in normal physiology and diseases.
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Affiliation(s)
- Mark H. Doolittle
- Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles, and VA Greater Los Angeles Healthcare System, 11301 Wilshire Blvd., Bldg. 113, Rm. 312, Los Angeles, CA 90073, USA, Tel.: 661-433-6349, Fax: 310-268-4981,
| | - Nicole Ehrhardt
- Medical Genetics Institute, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles, CA 90048, USA, Tel.: 310-423-3862, Fax: 310-423-0299,
| | - Miklós Péterfy
- Medical Genetics Institute, Cedars-Sinai Medical Center, and Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles, 8700 Beverly Blvd., Los Angeles, CA 90048, USA, Tel.: 310-478-3711 x42153, Fax: 310-268-4981,
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18
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Lindholm D, Bornhauser BC, Korhonen L. Mylip makes an Idol turn into regulation of LDL receptor. Cell Mol Life Sci 2009; 66:3399-402. [PMID: 19688294 PMCID: PMC11115883 DOI: 10.1007/s00018-009-0127-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 07/30/2009] [Accepted: 08/04/2009] [Indexed: 01/29/2023]
Abstract
High blood low-density-lipoprotein (LDL) cholesterol is a serious health problem among an increased number of patients in the Western world. Statins and other cholesterol lowering drugs have proven to be beneficial as therapy but are not optimal and show adverse effects in some patients. The LDL receptor is a crucial determinant of cholesterol metabolism in the body and amenable for drug interventions. Novel insights into the physiology of this receptor come from studies on the ubiquitination and degradation of LDL receptor by the ubiquitin ligase Mylip/Idol that is induced in cells by the nuclear receptor, LXR. This may open up new possibilities in the future to influence LDL receptor levels and cholesterol metabolism pharmacologically in various diseases.
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Affiliation(s)
- Dan Lindholm
- Minerva Medical Research Institute, Biomedicum-2, Helsinki University, Stockholmsgatan 8, 00290 Helsinki, Finland.
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Doolittle MH, Neher SB, Ben-Zeev O, Ling-Liao J, Gallagher CM, Hosseini M, Yin F, Wong H, Walter P, Péterfy M. Lipase maturation factor LMF1, membrane topology and interaction with lipase proteins in the endoplasmic reticulum. J Biol Chem 2009; 284:33623-33. [PMID: 19783858 DOI: 10.1074/jbc.m109.049395] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipase maturation factor 1 (LMF1) is predicted to be a polytopic protein localized to the endoplasmic reticulum (ER) membrane. It functions in the post-translational attainment of enzyme activity for both lipoprotein lipase and hepatic lipase. By using transmembrane prediction methods in mouse and human orthologs, models of LMF1 topology were constructed and tested experimentally. Employing a tagging strategy that used insertion of ectopic glycan attachment sites and terminal fusions of green fluorescent protein, we established a five-transmembrane model, thus dividing LMF1 into six domains. Three domains were found to face the cytoplasm (the amino-terminal domain and loops B and D), and the other half was oriented to the ER lumen (loops A and C and the carboxyl-terminal domain). This representative model shows the arrangement of an evolutionarily conserved domain within LMF1 (DUF1222) that is essential to lipase maturation. DUF1222 comprises four of the six domains, with the two largest ones facing the ER lumen. We showed for the first time, using several naturally occurring variants featuring DUF1222 truncations, that Lmf1 interacts physically with lipoprotein lipase and hepatic lipase and localizes the lipase interaction site to loop C within DUF1222. We discuss the implication of our results with regard to lipase maturation and DUF1222 domain structure.
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Affiliation(s)
- Mark H Doolittle
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA.
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20
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Abstract
Lipases are acyl hydrolases that represent a diverse group of enzymes present in organisms ranging from prokaryotes to humans. This article focuses on an evolutionarily related family of extracellular lipases that include lipoprotein lipase, hepatic lipase and endothelial lipase. As newly synthesized proteins, these lipases undergo a series of co- and post-translational maturation steps occurring in the endoplasmic reticulum, including glycosylation and glycan processing, and protein folding and subunit assembly. This article identifies and discusses mechanisms that direct early and late events in lipase folding and assembly. Lipase maturation employs the two general chaperone systems operating in the endoplasmic reticulum, as well as a recently identified lipase-specific chaperone termed lipase maturation factor 1. We propose that the two general chaperone systems act in a coordinated manner early in lipase maturation in order to help create partially folded monomers; lipase maturation factor 1 then facilitates final monomer folding and subunit assembly into fully functional homodimers. Once maturation is complete, the lipases exit the endoplasmic reticulum and are secreted to extracellular sites, where they carry out a number of functions related to lipoprotein and lipid metabolism.
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Affiliation(s)
- Mark H Doolittle
- VA Greater Los Angeles, Healthcare System, 11301 Wilshire Blvd, Bldg 113, Rm 312, Los Angeles, CA 90073, USA, Tel.: +1 661 433 6349
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