143 results on '"Zelcer N"'
Search Results
2. Spring is a novel regulator of hepatic lipid metabolism and plasma lipoprotein levels
- Author
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Hendrix, S., primary and Zelcer, N., additional
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- 2023
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3. Genome-wide CRISPR-Cas9 screen to identify new proteins involved in intracellular cholesterol transport
- Author
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Meurs, A., primary, De Lint, K., additional, and Zelcer, N., additional
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- 2022
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4. SPRING1 is required for proper functioning of SREPB mediated lipid synthesis
- Author
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Hendrix, S., primary and Zelcer, N., additional
- Published
- 2022
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5. Multi-OMIC profiling of LXR activation identifies SLPG as a sterol-inducible lysoplasmalogenase in macrophages
- Author
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Van Wouw, S., primary, Van Den Berg, M., additional, and Zelcer, N., additional
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- 2022
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6. P612: CHRONIC LYMPHOCYTIC LEUKEMIA (CLL)-DERIVED T-CELLS HAVE DISTURBED FATTY ACID METABOLISM, POSSIBLY CONTRIBUTING TO T-CELL DYSFUNCTION
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Jacobs, C. F., primary, Simon-Molas, H., additional, Zelcer, N., additional, Kater, A. P., additional, and Peters, F. S., additional
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- 2022
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7. SPRING is a novel determinant in SREBP signalling and cholesterol metabolism
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Hendrix, S., primary, Zelcer, N., additional, Valiloo, M., additional, and Tan, J., additional
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- 2021
- Full Text
- View/download PDF
8. MRP2 and 3 in health and disease
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Borst, P., Zelcer, N., and van de Wetering, K.
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- 2006
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9. On the putative co-transport of drugs by multidrug resistance proteins
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Borst, P., Zelcer, N., van de Wetering, K., and Poolman, B.
- Published
- 2006
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10. The potential impact of drug transporters on nucleoside-analog-based antiviral chemotherapy
- Author
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Borst, P., Balzarini, J., Ono, N., Reid, G., de Vries, H., Wielinga, P., Wijnholds, J., and Zelcer, N.
- Published
- 2004
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11. A MARCH6 and IDOL E3 ubiquitin ligase circuit uncouples cholesterol synthesis from lipoprotein uptake in hepatocytes
- Author
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Loregger, A., primary, Cook, E., additional, Nelson, J., additional, Moeton, M., additional, Sharpe, L., additional, Engberg, S., additional, Karimova, M., additional, Lambert, G., additional, and Zelcer, N., additional
- Published
- 2016
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12. identification of a novel LXR target
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Cook, E.C.L., primary, Nelson, J.K., additional, Sorrentino, V., additional, and Zelcer, N., additional
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- 2016
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13. Mutations in stap1 are associated with autosomal dominant hypercholesterolemia
- Author
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Fouchier, S.W., primary, Stitziel, N.O., additional, Dallinga-Thie, G.M., additional, Meijers, J.C.M., additional, Zelcer, N., additional, Kastelein, J.J.P., additional, Defesche, J.C., additional, Kathiresan, S., additional, and Hovingh, G.K., additional
- Published
- 2014
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14. MRP2-4, from drug resistance to physiology
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Zelcer, N., Borst, Piet, Other departments, Borst, P., and Faculteit der Geneeskunde
- Published
- 2003
15. Identification of a loss-of-function inducible degrader of the low-density lipoprotein receptor variant in individuals with low circulating low-density lipoprotein
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Sorrentino, V., primary, Fouchier, S. W., additional, Motazacker, M. M., additional, Nelson, J. K., additional, Defesche, J. C., additional, Dallinga-Thie, G. M., additional, Kastelein, J. J. P., additional, Kees Hovingh, G., additional, and Zelcer, N., additional
- Published
- 2013
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16. 603 COMBINING EXOME SEQUENCING WITH EXCLUSION LINKAGE ANALYSIS AS A TOOL TO UNRAVEL THE MOLECULAR BASIS OF A COMMON GENETIC DISEASE
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Motazacker, M.M., primary, Huijgen, R., additional, Peter, J., additional, Defesche, J.C., additional, Kastelein, J.J.R, additional, Hovingh, G.K., additional, Kathiresan, S., additional, Zelcer, N., additional, and Fouchier, S.W., additional
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- 2011
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17. Liver X receptors as integrators of metabolic and inflammatory signaling
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Zelcer, N., primary
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- 2006
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18. On the putative co-transport of drugs by multidrug resistance proteins
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Borst, P., primary, Zelcer, N., additional, van de Wetering, K., additional, and Poolman, B., additional
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- 2005
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19. ABC transporters in lipid transport
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Borst, P, primary, Zelcer, N, additional, and van Helvoort, A, additional
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- 2000
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20. Inactivation of the E3 Ubiquitin Ligase IDOL Attenuates Diet-Induced Obesity and Metabolic Dysfunction in Mice
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van Loon, NM, Ottenhoff, R, Kooijman, S, Moeton, M, Scheij, S, Abbing, RLPR, Gijbels, MJJ, Levels, JHM, Sorrentino, V, Berbee, JFP, Rensen, PCN, and Zelcer, N
21. A delicate balance: Post-transcriptional regulation of intracellular cholesterol metabolism
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Tan, J.M.E., Zelcer, N., Huveneers, Stephan, Loregger, A., and Faculteit der Geneeskunde
- Subjects
lipids (amino acids, peptides, and proteins) - Abstract
The maintenance of intracellular cholesterol homeostasis relies on a fascinating interplay between multiple complex molecular processes. The studies described in this thesis highlight the contribution of post-transcriptional regulation to the control of intracellular lipid metabolism. The membranes of our cells are comprised of a complex heterogeneous mixture of different lipids and proteins. Cholesterol is a lipid that is essential for the integrity and function of our membranes. Cholesterol also serves as a critical precursor for steroid hormones, as cortisol and oestrogen, bile acids and vitamins, for instance vitamin D. Inversely, a dysregulated systemic cholesterol metabolism can be detrimental to human health, and is associated with many pathologies, including cardiovascular disease, neurological disorders, and cancer. Chapter 1 comprises a general introduction, explaining the mechanisms that cells employ to tightly regulate their cholesterol levels. In chapter 2 , we describe an unbiased screening approach, by which we identify the SREBP-regulating gene (SPRING) as a new moiety in the (post-)transcriptional regulation of cholesterol metabolism. In chapter 3 , we focus on the post-translational regulation of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), which is the first rate-limiting enzyme of cholesterol biosynthesis and the target of statins. We identify UBXD8 a necessary element for extraction and subsequent proteasomal degradation of HMGCR in response to oxysterols. In chapter 4 , we move to the second rate-limiting enzyme of cholesterol biosynthesis: squalene monooxygenase (SQLE), which is subject to ubiquitylation and subsequent degradation in response to cholesterol. We identify UBE2J2 as the E2 ubiquitin conjugating enzyme necessary for this process, and show that the degradation of SQLE and HMGCR relies on the use of different E2 enzymes. In chapter 5 , we investigate the function of the E3 ligase of SQLE, MARCH6, in endothelial cells. We find that MARCH6-regulated SQLE levels are an important determinant of endothelial junctional integrity and angiogenesis. Chapter 6 summarises the studies presented in this thesis and places the findings in a broader context.
- Published
- 2021
22. Forces that control endothelial adhesion in angiogenesis
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van der Stoel, M.M., Huveneers, Stephan, de Vries, C.J.M., Zelcer, N., and Faculteit der Geneeskunde
- Abstract
Angiogenesis, the formation of new blood vessels from preexisting ones, is regulated by collective migration of endothelial cells, by dynamic remodeling of their cell – cell and cell – extracellular matrix adhesions. During angiogenesis, the mechanical forces subjected to the endothelial layer change, including matrix rigidity, hemodynamic forces and actin cytoskeletal contractility. The endothelial adhesions can sense and transmit these forces into biochemical signaling, resulting in changes in gene expression, adhesion, migration, proliferation and angiogenesis. In this thesis, we examined how different endothelial signaling events regulate sprouting angiogenesis via modulation of cell – cell and cell- extracellular matrix adhesions. Using in vitro and in vivo angiogenic sprouting models we describe how endothelial functions are modulated by internal processes such as cholesterol biosynthesis and cytoskeletal-mechanotransduction, but also by external stimuli, like extracellular matrix stiffening and hemodynamic forces, and the implications that these have for angiogenic processes. Overall, this thesis contributes to a better understanding of the endothelial adhesion mechanotransductory processes during angiogenesis.
- Published
- 2021
23. Cholesterol metabolism and hematopoiesis interaction in atherothrombosis
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Ouweneel, A.B., Eck, M. van, Vlijmen, B.J.M. van, Irth, H., Bouwstra, J.A., Versteeg, H.H., Zelcer, N., Pasterkamp, G., and Leiden University
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Megakaryopoiesis ,High_density lipoproteins ,Hypercholesterolemia ,Atherothrombosis ,Cholesterol efflux ,Small interfering RNA ,Atherosclerosis ,Mouse models ,Hematopoiesis ,Protein C - Abstract
Cardiovascular disease is the leading cause of death worldwide. The primary underlying pathology of cardiovascular disease is atherosclerosis. Atherosclerosis is a chronic, multifactorial disease in which lipid accumulates in the arterial wall, leading to a local inflammatory reaction and atherosclerotic plaque formation. Atherosclerotic disease develops largely asymptomatic over a lifetime. However, plaque rupture or erosion can cause the formation of a superimposed thrombus, blocking the flow of blood, and cause acute cardiovascular events such as myocardial infarction or ischemic stroke. Defects in cholesterol metabolism and hypercholesterolemia, which are major risk factors for atherosclerosis, have been shown to affect hematopoiesis, immune cell production and platelet counts and reactivity. Therefore, bone marrow cholesterol handling is an interesting target in the battle against cardiovascular disease, and acute cardiovascular events in particular. This thesis describes novel interactions between cholesterol metabolism and the production of immune cells and platelets, and its effects on atherosclerosis and atherothrombosis development.
- Published
- 2019
24. A matter of perspective: The multifaceted role of UBE3A in Angelman syndrome development
- Author
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Avagliano Trezza, R., Distel, B., Zelcer, N., Aerts, Johannes M.F.G., Faculteit der Geneeskunde, Distel, Bernard, Zelcer, Noam, Aerts, Johannes M. F. G., Graduate School, and Medical Biochemistry
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities - Abstract
Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by mutation or deletion of the UBE3A gene, which encodes an E3 ubiquitin protein ligase. E3 ligases are essential components of the UPS (ubiquitin proteasome system). The UPS is a finely tuned machinery that has an essential role in cellular homeostasis, and any perturbation of the UPS may lead to irreparable cellular damage. In this thesis we have employed molecular and biochemical techniques to unravel how the loss-of-function (deletion or mutations) of the E3 ubiquitin protein ligase UBE3A results in AS development, with emphasis on the identification and characterization of brain-specific targets of UBE3A. Using protein-protein interaction techniques we have identified several bona fide UBE3A interacting proteins, among which a pre-synaptic protein. Detailed biochemical and mutational analyses of these proteins have provided the first insights into the intracellular pathways where UBE3A exerts its function. By studying the localization of UBE3A isoforms we uncovered that UBE3A is predominantly localized in the nucleus and that AS-linked mutations can disturb nuclear localization. These observations suggest that UBE3A has an important role in the nucleus, providing further direction for future studies on the relation between UBE3A subcellular localization and the pathophysiology of AS.
- Published
- 2019
25. Fine-tuning protein recycling to control cholesterol homeostasis
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Cook, E.C.L., Zelcer, N., de Vries, C.J.M., Loregger, A., and Faculteit der Geneeskunde
- Subjects
lipids (amino acids, peptides, and proteins) - Abstract
Intracellular levels of cholesterol are paramount to regulating cholesterol levels in blood. The Ubiquitin Proteasome System (UPS) can regulate the expression and activity of the master regulators of cholesterol levels in the cell: SREBP2 and LXR. The UPS, its E2 and E3 ligases and deubiquitylating enzymes (DUBs) can also fine-tune the expression, degradation and activity enzymes involved in the synthesis, uptake and efflux of cholesterol. Using molecular techniques, in this thesis we focus on the identification and description of new pathways that regulate intracellular cholesterol pools through the UPS. Two new E3 ligases involved in the regulation of intracellular cholesterol homeostasis were identified: MARCH6 and RNF145. Both E3 ligases respond to high cholesterol levels. MARCH6 degrades SM, an enzyme involved in cholesterol synthesis when intracellular cholesterol is high. RNF145's transcription is responsive to LXR, a transcription factor activated in the presence of certain cholesterol derivatives. We also look at a feedback mechanism in cholesterol homeostasis regulated by two E3 ligases: MARCH6 and IDOL. This feedback mechanism regulates which cholesterol source is preferentially used by the cell: either uptake or synthesis. The E2 ligases involved in the cholesterol-mediated degradation of HMGCR and SM were identified and serve as another mechanism to differentiate their breakdown. Furthermore, we identify a novel regulation of IDOL by DUBs, independent of its regulation by LXR.
- Published
- 2019
26. Nuclear receptors and their co-factors in hematological and inflammation-driven disorders
- Author
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Koenis, D.S., de Vries, C.J.M., Zelcer, N., de Waard, V., Huveneers, S., and Faculteit der Geneeskunde
- Abstract
Nuclear receptors are a class of ligand-activated transcription factors that regulate the expression of genes involved in all aspects of cellular biology. The nuclear receptors Nur77 and liver X receptor (LXR) are two well-established regulators of inflammation and metabolism that play important roles in the pathogenesis of diseases driven by excessive inflammation and dysregulated metabolism, such as atherosclerosis. This thesis describes new ways in which the activity of Nur77 and LXR is regulated and how they, in turn, can regulate cellular metabolism, inflammatory responses, and immune cell differentiation. The key findings of this thesis include the identification of two novel coregulatory proteins that enhance Nur77 and LXR activity, the genome-wide profiling of Nur77 binding sites and target genes in macrophages, the identification of Nur77 as an important factor in the metabolic switch of macrophages upon inflammatory stimulation, and the characterization of differences in hematological phenotypes between two distinct Nur77-deficient mouse models.
- Published
- 2018
27. Liver X receptors constrain tumor development and metastasis dissemination in PTEN-deficient prostate cancer
- Author
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Alioui, Anthony, Dufour, Julie, Leoni, Valerio, Loregger, Anke, Moeton, Martina, Iuliano, Luigi, Zerbinati, Chiara, Septier, Amandine, Val, Pierre, Fouache, Allan, Russo, Vincenzo, Volle, David H., Lobaccaro, Jean-Marc A., Zelcer, Noam, Baron, Silvère, Alioui, A, Dufour, J, Leoni, V, Loregger, A, Moeton, M, Iuliano, L, Zerbinati, C, Septier, A, Val, P, Fouache, A, Russo, V, Volle, D, Lobaccaro, J, Zelcer, N, Baron, S, Medical Biochemistry, Amsterdam Gastroenterology Endocrinology Metabolism, ACS - Diabetes & metabolism, and ACS - Atherosclerosis & ischemic syndromes
- Subjects
Male ,Mice, Knockout ,Gene Expression Profiling ,PTEN Phosphohydrolase ,Prostate ,Prostatic Neoplasms ,Kaplan-Meier Estimate ,Article ,Cholesterol ,Retraction Note ,Cell Line, Tumor ,Disease Progression ,Animals ,Humans ,lipids (amino acids, peptides, and proteins) ,oxysterols, sterols, cholesterol, mass spectrometry, metabolomics, neurodegenerative diseases ,Neoplasm Metastasis ,Cells, Cultured ,Liver X Receptors ,Signal Transduction - Abstract
Advanced prostate cancer (PCa) is a clinical challenge as no curative therapeutic is available. In this context, a better understanding of metastasis and resistance mechanisms in PCa is an important issue. As phosphatase and tensin homolog (PTEN) loss is the most common genetic lesion in such cancer, we investigate human data sets for mechanisms that can constrain cancer evolution in this setting. Here we report a liver X receptor (LXR) signature, which tightly correlates with PTEN loss, in PCa. Accordingly, the LXR pathway is deregulated in prostate carcinomas in Pten-null mice. Genetic ablation of LXRs in Pten-null mice, exacerbates PCa invasiveness and metastatic dissemination, which involves mesenchymal transition and accumulation of matrix metalloproteinases. Mechanistically, PTEN deletion governed LXR transcriptional activity through deregulation of cholesterol de novo synthesis, resulting in accumulation of endogenous LXR ligands. Our study therefore reveals a functional circuit linking PTEN and LXR, and highlights LXRs as metabolic gatekeepers that are able to constrain PCa progression., Treatment of prostate cancer, especially in its advanced stage, is still challenging; therefore, strategies to prevent metastatic dissemination are of great interest. Here the authors reveal a crucial role for liver X receptors in suppressing prostate carcinogenesis and metastatic progression in PTEN-null tumors.
- Published
- 2017
28. Scratching the surface: Regulation of cell surface receptors in cholesterol metabolism
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Nelson, J.K., de Vries, C.J.M., Zelcer, N., and Faculteit der Geneeskunde
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lipids (amino acids, peptides, and proteins) - Abstract
Elevated plasma levels of low density lipoprotein cholesterol (LDL) are an established risk factor for the development of atherosclerosis and cardiovascular diseases. The LDL-Receptor is a key determinant in regulating LDL levels in plasma, and current lipid-lowering strategies aim to increase its cell surface expression. My PhD research has largely focused on the characterization of novel post-translational regulators of the LDL-Receptor. Mainly, I studied the Liver X Receptor (LXR) responsive E3 ubiquitin ligase, the Inducible Degrader of the LDL-Receptor (IDOL), which negatively regulates the LDL-Receptor and attenuates LDL uptake into cells. Through genetic, molecular and biochemical characterization, we identified novel mechanisms and components that regulate IDOL-mediated degradation of the LDL-Receptor. Specifically, I was involved in investigating the endocytic trafficking route of this degradation pathway, identifying a deubiquitlyase (DUB) that attenuates IDOL activity, describing a novel transcriptional regulatory mechanism, as well as characterizing a rare IDOL variant in individuals with low circulating LDL-cholesterol levels. These findings suggest that IDOL inhibition would be beneficial for developing new lipid lowering strategies, and thus, have laid the foundation for ongoing research aimed at solving the structure of IDOL as well as characterizing its physiological impact in vivo. Collectively, my research resulted in the publication of 7 articles in peer-reviewed journals and 2 articles currently in submission.
- Published
- 2016
29. Deregulation of lysosomal and mitochondrial dynamics in obesity
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Tol, M.J.P.M., Verhoeven, Arthur, Zelcer, N., van Eijk, M.C., and Faculteit der Geneeskunde
- Abstract
In recent years, it is increasingly recognized that changes in cellular nutrient status impact organelle dynamics. Yet, the physiological relevance thereof as well as the inherent tissue-specific mechanisms remain enigmatic. Research described in this thesis aims at unravelling hitherto undefined signalling pathways in white adipose tissue (WAT) that are (de)regulated in obesity, with emphasis on the core hallmarks of insulin resistance (IR), namely low-grade inflammation and mitochondrial dysfunction. A holistic approach, involving bioinformatics, genetic, and pharmacological strategies in cultured cells and murine obesity models is used to identify novel transcriptional circuits that modulate organelle dynamics in WAT and resident adipose tissue macrophages (ATMs). We describe a regulatory circuit in which peroxisome proliferator–activated receptor γ (PPARγ), the adipocyte master regulator and receptor for the thiazolidinedione (TZD) class of antidiabetic drugs, controls mitochondrial network fragmentation through transcriptional induction of the BH3-only Bnip3. This mode of action leads to adipose insulin sensitization and improved mitochondrial bioenergetics. Additionally, we report the activation of a coherent lysosomal gene program in obese ATMs, governed by the MiT/TFE family of transcription factors. Altogether, these data uncover transcriptionally regulated organelle dynamics in adipose tissue, and its (de)regulation in obesity-related IR.
- Published
- 2016
30. SPRING licenses S1P-mediated cleavage of SREBP2 by displacing an inhibitory pro-domain.
- Author
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Hendrix S, Dartigue V, Hall H, Bawaria S, Kingma J, Bajaj B, Zelcer N, and Kober DL
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- Humans, Serine Endopeptidases metabolism, Serine Endopeptidases chemistry, Serine Endopeptidases genetics, Endoplasmic Reticulum metabolism, Cryoelectron Microscopy, Golgi Apparatus metabolism, Proprotein Convertases metabolism, Proprotein Convertases genetics, Cholesterol metabolism, Animals, HEK293 Cells, Signal Transduction, Sterol Regulatory Element Binding Protein 2 metabolism, Sterol Regulatory Element Binding Protein 2 genetics, Protein Domains
- Abstract
Site-one protease (S1P) conducts the first of two cleavage events in the Golgi to activate Sterol regulatory element binding proteins (SREBPs) and upregulate lipogenic transcription. S1P is also required for a wide array of additional signaling pathways. A zymogen serine protease, S1P matures through autoproteolysis of two pro-domains, with one cleavage event in the endoplasmic reticulum (ER) and the other in the Golgi. We recently identified the SREBP regulating gene, (SPRING), which enhances S1P maturation and is necessary for SREBP signaling. Here, we report the cryo-EM structures of S1P and S1P-SPRING at sub-2.5 Å resolution. SPRING activates S1P by dislodging its inhibitory pro-domain and stabilizing intra-domain contacts. Functionally, SPRING licenses S1P to cleave its cognate substrate, SREBP2. Our findings reveal an activation mechanism for S1P and provide insights into how spatial control of S1P activity underpins cholesterol homeostasis., (© 2024. The Author(s).)
- Published
- 2024
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31. A suite of genome-engineered hepatic cells provide novel insights into the spatiotemporal metabolism of APOB and APOB-containing lipoprotein secretion.
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Meurs A, Ndoj K, van den Berg M, Marinković G, Tantucci M, Veenendaal T, Kuivenhoven JA, Klumperman J, and Zelcer N
- Abstract
Aims: APOB-containing very-low-density lipoprotein (VLDL) production, secretion, and clearance by hepatocytes is a central determinant of hepatic and circulating lipid levels. Impairment of any of the aforementioned processes is associated with the development of multiple diseases. Despite the discovery of genes and processes that govern hepatic VLDL metabolism, our understanding of the different mechanistic steps involved is far from complete. An impediment to these studies is the lack of tractable hepatocyte-based systems to interrogate and follow APOB in cells, which the current study addresses., Methods and Results: To facilitate the cellular study of VLDL metabolism, we generated human hepatic HepG2 and Huh-7 cell lines in which CRISPR/Cas9-based genome engineering was used to introduce the fluorescent protein mNeonGreen into the APOB gene locus. This results in the production of APOB100-mNeon that localizes predominantly to the endoplasmic reticulum (ER) and Golgi by immunofluorescence and electron microscopy imaging. The production and secretion of APOB100-mNeon can be quantitatively followed in medium over time, and results in production of lipoproteins that are taken up via the LDLR pathway. Importantly, the production and secretion of APOB-mNeon is sensitive to established pharmacological and physiological treatments, and to genetic modifiers known to influence VLDL production in humans. As a showcase, we used HepG2-APOBmNeon cells to interrogate ER-associated degradation (ERAD) of APOB. Using a dedicated sgRNA library targeting all established membrane-associated ER-resident E3 ubiquitin ligases led to identification of SYNV1 as the E3 responsible for degradation of poorly-lipidated APOB in HepG2 cells., Conclusions: In summary, the engineered cells reported here allow the study of hepatic VLDL assembly and secretion, and facilitate spatiotemporal interrogation induced by pharmacologic and genetic perturbations., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)
- Published
- 2024
- Full Text
- View/download PDF
32. The ubiquitous role of ubiquitination in lipid metabolism.
- Author
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Loix M, Zelcer N, Bogie JFJ, and Hendriks JJA
- Subjects
- Animals, Humans, Signal Transduction, Ubiquitin metabolism, Lipid Metabolism, Ubiquitination
- Abstract
Lipids are essential molecules that play key roles in cell physiology by serving as structural components, for storage of energy, and in signal transduction. Hence, efficient regulation and maintenance of lipid homeostasis are crucial for normal cellular and tissue function. In the past decade, increasing research has shown the importance of ubiquitination in regulating the stability of key players in different aspects of lipid metabolism. This review describes recent insights into the regulation of lipid metabolism by ubiquitin signaling, discusses how ubiquitination can be targeted in diseases characterized by lipid dysregulation, and identifies areas that require further research., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)
- Published
- 2024
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33. SPRING is a Dedicated Licensing Factor for SREBP-Specific Activation by S1P.
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Hendrix S, Tan JME, Ndoj K, Kingma J, Valiloo M, Zijlstra LF, Ottenhoff R, Seidah NG, Loregger A, Kober DL, and Zelcer N
- Subjects
- Animals, Humans, Mice, Endoplasmic Reticulum metabolism, Golgi Apparatus metabolism, HEK293 Cells, Liver metabolism, Mice, Knockout, Proteolysis, Signal Transduction, Sterol Regulatory Element Binding Proteins metabolism, Sterol Regulatory Element Binding Proteins genetics, Proprotein Convertases metabolism, Proprotein Convertases genetics, Serine Endopeptidases metabolism, Serine Endopeptidases genetics
- Abstract
SREBP transcription factors are central regulators of lipid metabolism. Their proteolytic activation requires ER to the Golgi translocation and subsequent cleavage by site-1-protease (S1P). Produced as a proprotein, S1P undergoes autocatalytic cleavage from its precursor S1P
A to mature S1PC form. Here, we report that SPRING (previously C12ORF29) and S1P interact through their ectodomains, and that this facilitates the autocatalytic cleavage of S1PA into its mature S1PC form. Reciprocally, we identified a S1P recognition-motif in SPRING and demonstrate that S1P-mediated cleavage leads to secretion of the SPRING ectodomain in cells, and in liver-specific Spring knockout (LKO) mice transduced with AAV-mSpring. By reconstituting SPRING variants into SPRINGKO cells we show that the SPRING ectodomain supports proteolytic maturation of S1P and SREBP signaling, but that S1P-mediated SPRING cleavage is not essential for these processes. Absence of SPRING modestly diminishes proteolytic maturation of S1PA→C and trafficking of S1PC to the Golgi. However, despite reaching the Golgi in SPRINGKO cells, S1PC fails to rescue SREBP signaling. Remarkably, whereas SREBP signaling was severely attenuated in SPRINGKO cells and LKO mice, that of ATF6, another S1P substrate, was unaffected in these models. Collectively, our study positions SPRING as a dedicated licensing factor for SREBP-specific activation by S1P.- Published
- 2024
- Full Text
- View/download PDF
34. A new SPRING in lipid metabolism.
- Author
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Hendrix S and Zelcer N
- Subjects
- Humans, Mice, Animals, Sterol Regulatory Element Binding Protein 1 metabolism, Membrane Proteins genetics, Cholesterol metabolism, Lipid Metabolism genetics, Intracellular Signaling Peptides and Proteins metabolism
- Abstract
Purpose of Review: The SREBP transcription factors are master regulators of lipid homeostasis owing to their role in controlling cholesterol and fatty acid metabolism. The core machinery required to promote their trafficking and proteolytic activation has been established close to 20 years ago. In this review, we summarize the current understanding of a newly identified regulator of SREBP signaling, SPRING (formerly C12ORF49), its proposed mechanism of action, and its role in lipid metabolism., Recent Findings: Using whole-genome functional genetic screens we, and others, have recently identified SPRING as a novel regulator of SREBP signaling. SPRING is a Golgi-resident single-pass transmembrane protein that is required for proteolytic activation of SREBPs in this compartment. Mechanistic studies identified regulation of S1P, the protease that cleaves SREBPs, and control of retrograde trafficking of the SREBP chaperone SCAP from the Golgi to the ER as processes requiring SPRING. Emerging studies suggest an important role for SPRING in regulating circulating and hepatic lipid levels in mice and potentially in humans., Summary: Current studies support the notion that SPRING is a novel component of the core SREBP-activating machinery. Additional studies are warranted to elucidate its role in cellular and systemic lipid metabolism., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.)
- Published
- 2023
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35. Hepatic SREBP signaling requires SPRING to govern systemic lipid metabolism in mice and humans.
- Author
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Hendrix S, Kingma J, Ottenhoff R, Valiloo M, Svecla M, Zijlstra LF, Sachdev V, Kovac K, Levels JHM, Jongejan A, de Boer JF, Kuipers F, Rimbert A, Norata GD, Loregger A, and Zelcer N
- Subjects
- Humans, Female, Male, Animals, Mice, Sterol Regulatory Element Binding Protein 1 genetics, Hepatocytes, Lipoproteins, HDL, Lipid Metabolism genetics, Liver
- Abstract
The sterol regulatory element binding proteins (SREBPs) are transcription factors that govern cholesterol and fatty acid metabolism. We recently identified SPRING as a post-transcriptional regulator of SREBP activation. Constitutive or inducible global ablation of Spring in mice is not tolerated, and we therefore develop liver-specific Spring knockout mice (LKO). Transcriptomics and proteomics analysis reveal attenuated SREBP signaling in livers and hepatocytes of LKO mice. Total plasma cholesterol is reduced in male and female LKO mice in both the low-density lipoprotein and high-density lipoprotein fractions, while triglycerides are unaffected. Loss of Spring decreases hepatic cholesterol and triglyceride content due to diminished biosynthesis, which coincides with reduced very-low-density lipoprotein secretion. Accordingly, LKO mice are protected from fructose diet-induced hepatosteatosis. In humans, we find common genetic SPRING variants that associate with circulating high-density lipoprotein cholesterol and ApoA1 levels. This study positions SPRING as a core component of hepatic SREBP signaling and systemic lipid metabolism in mice and humans., (© 2023. Springer Nature Limited.)
- Published
- 2023
- Full Text
- View/download PDF
36. Hyperlipidaemia elicits an atypical, T helper 1-like CD4 + T-cell response: a key role for very low-density lipoprotein.
- Author
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van Os BW, Vos WG, Bosmans LA, van Tiel CM, Lith SC, den Toom MS, Beckers L, Levels JHM, van Wouw SAE, Zelcer N, Zaal EA, Berkers CR, van der Lest CHA, Helms JB, Weber C, Atzler D, de Winther MPJ, Baardman J, and Lutgens E
- Abstract
Aims: Hyperlipidemia and T cell driven inflammation are important drivers of atherosclerosis, the main underlying cause of cardiovascular disease. Here, we detailed the effects of hyperlipidemia on T cells., Methods and Results: In vitro, exposure of human and murine CD4+ T cells to very low-density lipoprotein (VLDL), but not to low-density lipoprotein (LDL) resulted in upregulation of Th1 associated pathways. VLDL was taken up via a CD36-dependent pathway and resulted in membrane stiffening and a reduction in lipid rafts. To further detail this response in vivo , T cells of mice lacking the LDL receptor (LDLr), which develop a strong increase in VLDL cholesterol and triglyceride levels upon high cholesterol feeding were investigated. CD4+ T cells of hyperlipidemic Ldlr -/- mice exhibited an increased expression of the C-X-C-chemokine receptor 3 (CXCR3) and produced more interferon-γ (IFN-γ). Gene set enrichment analysis identified IFN-γ-mediated signaling as the most upregulated pathway in hyperlipidemic T cells. However, the classical Th1 associated transcription factor profile with strong upregulation of Tbet and Il12rb2 was not observed. Hyperlipidemia did not affect levels of the CD4+ T cell's metabolites involved in glycolysis or other canonical metabolic pathways but enhanced amino acids levels. However, CD4+ T cells of hyperlipidemic mice showed increased cholesterol accumulation and an increased arachidonic acid (AA) to docosahexaenoic acid (DHA) ratio, which was associated with inflammatory T cell activation., Conclusions: Hyperlipidemia, and especially its VLDL component induces an atypical Th1 response in CD4+ T cells. Underlying mechanisms include CD36 mediated uptake of VLDL, and an altered AA/DHA ratio., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)
- Published
- 2023
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37. Sterol-regulated transmembrane protein TMEM86a couples LXR signaling to regulation of lysoplasmalogens in macrophages.
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van Wouw SAE, van den Berg M, El Ouraoui M, Meurs A, Kingma J, Ottenhoff R, Loix M, Hoeksema MA, Prange K, Pasterkamp G, Hendriks JJA, Bogie JFJ, van Klinken JB, Vaz FM, Jongejan A, de Winther MPJ, and Zelcer N
- Subjects
- Animals, Humans, Mice, Liver X Receptors metabolism, Membrane Glycoproteins metabolism, Membrane Proteins metabolism, Receptors, Immunologic, Transcription Factors metabolism, Macrophages metabolism, Sterols metabolism
- Abstract
Lysoplasmalogens are a class of vinyl ether bioactive lipids that have a central role in plasmalogen metabolism and membrane fluidity. The liver X receptor (LXR) transcription factors are important determinants of cellular lipid homeostasis owing to their ability to regulate cholesterol and fatty acid metabolism. However, their role in governing the composition of lipid species such as lysoplasmalogens in cellular membranes is less well studied. Here, we mapped the lipidome of bone marrow-derived macrophages (BMDMs) following LXR activation. We found a marked reduction in the levels of lysoplasmalogen species in the absence of changes in the levels of plasmalogens themselves. Transcriptional profiling of LXR-activated macrophages identified the gene encoding transmembrane protein 86a (TMEM86a), an integral endoplasmic reticulum protein, as a previously uncharacterized sterol-regulated gene. We demonstrate that TMEM86a is a direct transcriptional target of LXR in macrophages and microglia and that it is highly expressed in TREM2
+ /lipid-associated macrophages in human atherosclerotic plaques, where its expression positively correlates with other LXR-regulated genes. We further show that both murine and human TMEM86a display active lysoplasmalogenase activity that can be abrogated by inactivating mutations in the predicted catalytic site. Consequently, we demonstrate that overexpression of Tmem86a in BMDM markedly reduces lysoplasmalogen abundance and membrane fluidity, while reciprocally, silencing of Tmem86a increases basal lysoplasmalogen levels and abrogates the LXR-dependent reduction of this lipid species. Collectively, our findings implicate TMEM86a as a sterol-regulated lysoplasmalogenase in macrophages that contributes to sterol-dependent membrane remodeling., Competing Interests: Conflict of interest The authors declare no conflict of interest., (Copyright © 2023. Published by Elsevier Inc.)- Published
- 2023
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38. DOT1L regulates lipid biosynthesis and inflammatory responses in macrophages and promotes atherosclerotic plaque stability.
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Willemsen L, Prange KHM, Neele AE, van Roomen CPAA, Gijbels M, Griffith GR, Toom MD, Beckers L, Siebeler R, Spann NJ, Chen HJ, Bosmans LA, Gorbatenko A, van Wouw S, Zelcer N, Jacobs H, van Leeuwen F, and de Winther MPJ
- Subjects
- Humans, Mice, Animals, Histones metabolism, Macrophages metabolism, Lipids, Histone-Lysine N-Methyltransferase metabolism, Plaque, Atherosclerotic
- Abstract
Macrophages are critical immune cells in inflammatory diseases, and their differentiation and function are tightly regulated by histone modifications. H3K79 methylation is a histone modification associated with active gene expression, and DOT1L is the only histone methyltransferase for H3K79. Here we determine the role of DOT1L in macrophages by applying a selective DOT1L inhibitor in mouse and human macrophages and using myeloid-specific Dot1l-deficient mice. We found that DOT1L directly regulates macrophage function by controlling lipid biosynthesis gene programs including central lipid regulators like sterol regulatory element-binding proteins SREBP1 and SREBP2. DOT1L inhibition also leads to macrophage hyperactivation, which is associated with disrupted SREBP pathways. In vivo, myeloid Dot1l deficiency reduces atherosclerotic plaque stability and increases the activation of inflammatory plaque macrophages. Our data show that DOT1L is a crucial regulator of macrophage inflammatory responses and lipid regulatory pathways and suggest a high relevance of H3K79 methylation in inflammatory disease., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2022
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39. Proteolysis Targeting Chimeras (PROTACs): A Perspective on Integral Membrane Protein Degradation.
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Ruffilli C, Roth S, Rodrigo M, Boyd H, Zelcer N, and Moreau K
- Abstract
Targeted protein degradation (TPD) is a promising therapeutic modality to modulate protein levels and its application promises to reduce the "undruggable" proteome. Among TPD strategies, Proteolysis TArgeting Chimera (PROTAC) technology has shown a tremendous potential with attractive advantages when compared to the inhibition of the same target. While PROTAC technology has had a significant impact in scientific research, its application to degrade integral membrane proteins (IMPs) is still in its beginnings. Among the 15 compounds having entered clinical trials by the end of 2021, only two targets are membrane-associated proteins. In this review we are discussing the potential reasons which may underlie this, and we are presenting new tools that have been recently developed to solve these limitations and to empower the use of PROTACs to target IMPs., Competing Interests: The authors declare the following competing financial interest(s): Camilla Ruffilli, Sascha Roth, Monica Rodrigo, Helen Boyd, and Kevin Moreau are all AstraZeneca employees., (© 2022 The Authors. Published by American Chemical Society.)
- Published
- 2022
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40. Anti-Galectin-2 Antibody Treatment Reduces Atherosclerotic Plaque Size and Alters Macrophage Polarity.
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Kane J, Jansen M, Hendrix S, Bosmans LA, Beckers L, Tiel CV, Gijbels M, Zelcer N, Vries CJ, von Hundelshausen P, Vervloet M, Eringa E, Horrevoets AJ, Royen NV, and Lutgens E
- Subjects
- Animals, Anti-Inflammatory Agents therapeutic use, Apolipoproteins E, Cholesterol, Disease Models, Animal, Galectin 2 pharmacology, Galectin 2 therapeutic use, Macrophages, Mice, Mice, Inbred C57BL, Mice, Knockout, Mice, Knockout, ApoE, Atherosclerosis genetics, Hyperlipidemias, Plaque, Atherosclerotic, Single-Domain Antibodies
- Abstract
Background: Galectins have numerous cellular functions in immunity and inflammation. Short-term galectin-2 (Gal-2) blockade in ischemia-induced arteriogenesis shifts macrophages to an anti-inflammatory phenotype and improves perfusion. Gal-2 may also affect other macrophage-related cardiovascular diseases., Objectives: This study aims to elucidate the effects of Gal-2 inhibition in atherosclerosis., Methods: ApoE -/- mice were given a high-cholesterol diet (HCD) for 12 weeks. After 6 weeks of HCD, intermediate atherosclerotic plaques were present. To study the effects of anti-Gal-2 nanobody treatment on the progression of existing atherosclerosis, treatment with two llama-derived anti-Gal-2 nanobodies (clones 2H8 and 2C10), or vehicle was given for the remaining 6 weeks., Results: Gal-2 inhibition reduced the progression of existing atherosclerosis. Atherosclerotic plaque area in the aortic root was decreased, especially so in mice treated with 2C10 nanobodies. This clone showed reduced atherosclerosis severity as reflected by a decrease in fibrous cap atheromas in addition to decreases in plaque size.The number of plaque resident macrophages was unchanged; however, there was a significant increase in the fraction of CD206
+ macrophages. 2C10 treatment also increased plaque α-smooth muscle content, and Gal-2 may have a role in modulating the inflammatory status of smooth muscle cells. Remarkably, both treatments reduced serum cholesterol concentrations including reductions in very low-density lipoprotein, low-density lipoprotein, and high-density lipoprotein while triglyceride concentrations were unchanged., Conclusion: Prolonged and frequent treatment with anti-Gal-2 nanobodies reduced plaque size, slowed plaque progression, and modified the phenotype of plaque macrophages toward an anti-inflammatory profile. These results hold promise for future macrophage modulating therapeutic interventions that promote arteriogenesis and reduce atherosclerosis., Competing Interests: M.V. reports having served as advisor for FMC, Amgen, Medice, Otsuka, Vifor, and Kyowa Kirin. Research support from FMC, Amgen, and Vifor. No other conflicts of interest to report., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).)- Published
- 2022
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41. Defective Lipid Droplet-Lysosome Interaction Causes Fatty Liver Disease as Evidenced by Human Mutations in TMEM199 and CCDC115.
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Larsen LE, van den Boogert MAW, Rios-Ocampo WA, Jansen JC, Conlon D, Chong PLE, Levels JHM, Eilers RE, Sachdev VV, Zelcer N, Raabe T, He M, Hand NJ, Drenth JPH, Rader DJ, Stroes ESG, Lefeber DJ, Jonker JW, and Holleboom AG
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- Animals, Hepatocytes metabolism, Humans, Lysosomes metabolism, Membrane Proteins genetics, Membrane Proteins metabolism, Mice, Mutation genetics, Nerve Tissue Proteins genetics, Fatty Liver genetics, Fatty Liver metabolism, Lipid Droplets metabolism
- Abstract
Background & Aims: Recently, novel inborn errors of metabolism were identified because of mutations in V-ATPase assembly factors TMEM199 and CCDC115. Patients are characterized by generalized protein glycosylation defects, hypercholesterolemia, and fatty liver disease. Here, we set out to characterize the lipid and fatty liver phenotype in human plasma, cell models, and a mouse model., Methods and Results: Patients with TMEM199 and CCDC115 mutations displayed hyperlipidemia, characterized by increased levels of lipoproteins in the very low density lipoprotein range. HepG2 hepatoma cells, in which the expression of TMEM199 and CCDC115 was silenced, and induced pluripotent stem cell (iPSC)-derived hepatocyte-like cells from patients with TMEM199 mutations showed markedly increased secretion of apolipoprotein B (apoB) compared with controls. A mouse model for TMEM199 deficiency with a CRISPR/Cas9-mediated knock-in of the human A7E mutation had marked hepatic steatosis on chow diet. Plasma N-glycans were hypogalactosylated, consistent with the patient phenotype, but no clear plasma lipid abnormalities were observed in the mouse model. In the siTMEM199 and siCCDC115 HepG2 hepatocyte models, increased numbers and size of lipid droplets were observed, including abnormally large lipid droplets, which colocalized with lysosomes. Excessive de novo lipogenesis, failing oxidative capacity, and elevated lipid uptake were not observed. Further investigation of lysosomal function revealed impaired acidification combined with impaired autophagic capacity., Conclusions: Our data suggest that the hypercholesterolemia in TMEM199 and CCDC115 deficiency is due to increased secretion of apoB-containing particles. This may in turn be secondary to the hepatic steatosis observed in these patients as well as in the mouse model. Mechanistically, we observed impaired lysosomal function characterized by reduced acidification, autophagy, and increased lysosomal lipid accumulation. These findings could explain the hepatic steatosis seen in patients and highlight the importance of lipophagy in fatty liver disease. Because this pathway remains understudied and its regulation is largely untargeted, further exploration of this pathway may offer novel strategies for therapeutic interventions to reduce lipotoxicity in fatty liver disease., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2022
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42. Liver X receptor beta deficiency attenuates autoimmune-associated neuroinflammation in a T cell-dependent manner.
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Bogie JFJ, Vanmierlo T, Vanmol J, Timmermans S, Mailleux J, Nelissen K, Wijnands E, Wouters K, Stinissen P, Gustafsson JÅ, Steffensen KR, Mulder M, Zelcer N, and Hendriks JJA
- Subjects
- Animals, Autoimmunity, Cholesterol metabolism, Disease Models, Animal, Humans, Liver X Receptors genetics, Mice, Mice, Inbred C57BL, Mice, Knockout, Neurogenic Inflammation, Encephalomyelitis, Autoimmune, Experimental immunology, Liver X Receptors metabolism, Microglia pathology, Multiple Sclerosis immunology, T-Lymphocytes immunology
- Abstract
The initiation and progression of autoimmune disorders such as multiple sclerosis (MS) is linked to aberrant cholesterol metabolism and overt inflammation. Liver X receptors (LXR) are nuclear receptors that function at the crossroads of cholesterol metabolism and immunity, and their activation is considered a promising therapeutic strategy to attenuate autoimmunity. However, despite clear functional heterogeneity and cell-specific expression profiles, the impact of the individual LXR isoforms on autoimmunity remains poorly understood. Here, we show that LXRα and LXRβ have an opposite impact on immune cell function and disease severity in the experimental autoimmune encephalomyelitis model, an experimental MS model. While Lxrα deficiency aggravated disease pathology and severity, absence of Lxrβ was protective. Guided by flow cytometry and by using cell-specific knockout models, reduced disease severity in Lxrβ-deficient mice was primarily attributed to changes in peripheral T cell physiology and occurred independent from alterations in microglia function. Collectively, our findings indicate that LXR isoforms play functionally non-redundant roles in autoimmunity, potentially having broad implications for the development of LXR-based therapeutic strategies aimed at dampening autoimmunity and neuroinflammation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)
- Published
- 2021
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43. Four-and-a-half LIM domain protein 2 (FHL2) deficiency protects mice from diet-induced obesity and high FHL2 expression marks human obesity.
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Clemente-Olivo MP, Habibe JJ, Vos M, Ottenhoff R, Jongejan A, Herrema H, Zelcer N, Kooijman S, Rensen PCN, van Raalte DH, Nieuwdorp M, Eringa EC, and de Vries CJ
- Subjects
- Adipogenesis genetics, Adipose Tissue, White metabolism, Adult, Aged, Animals, Biomarkers metabolism, Diet, High-Fat, Female, Genetic Predisposition to Disease, Humans, LIM-Homeodomain Proteins metabolism, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Middle Aged, Muscle Proteins metabolism, Obesity diagnosis, Obesity metabolism, Transcription Factors metabolism, Weight Gain genetics, LIM-Homeodomain Proteins genetics, Muscle Proteins genetics, Obesity genetics, Transcription Factors genetics
- Abstract
Objective: Four-and-a-Half-LIM-domain-protein 2 (FHL2) modulates multiple signal transduction pathways but has not been implicated in obesity or energy metabolism. In humans, methylation and expression of the FHL2 gene increases with age, and high FHL2 expression is associated with increased body weight in humans and mice. This led us to hypothesize that FHL2 is a determinant of diet-induced obesity., Methods: FHL2-deficient (FHL2-/-) and wild type male mice were fed a high-fat diet. Metabolic phenotyping of these mice, as well as transcriptional analysis of key metabolic tissues was performed. Correlation of the expression of FHL2 and relevant genes was assessed in datasets from white adipose tissue of individuals with and without obesity., Results: FHL2 Deficiency protects mice from high-fat diet-induced weight gain, whereas glucose handling is normal. We observed enhanced energy expenditure, which may be explained by a combination of changes in multiple tissues; mild activation of brown adipose tissue with increased fatty acid uptake, increased cardiac glucose uptake and browning of white adipose tissue. Corroborating our findings in mice, expression of FHL2 in human white adipose tissue positively correlates with obesity and negatively with expression of browning-associated genes., Conclusion: Our results position FHL2 as a novel regulator of obesity and energy expenditure in mice and human. Given that FHL2 expression increases during aging, we now show that low FHL2 expression associates with a healthy metabolic state., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2021
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44. Regulation of intestinal LDLR by the LXR-IDOL axis.
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van Loon NM, van Wouw SAE, Ottenhoff R, Nelson JK, Kingma J, Scheij S, Moeton M, and Zelcer N
- Subjects
- Animals, Intestines, Liver X Receptors, Mice, Ubiquitin-Protein Ligases genetics, Ubiquitination, Orphan Nuclear Receptors genetics, Receptors, LDL genetics, Receptors, LDL metabolism
- Abstract
Background and Aims: Cholesterol metabolism is tightly regulated by transcriptional and post-transcriptional mechanisms. Accordingly, dysregulation of cholesterol metabolism is a major risk factor for the development of coronary artery disease and associated complications. In recent years, it has become apparent that next to the liver, the intestine plays a key role in systemic cholesterol metabolism by governing cholesterol absorption, secretion, and incorporation into lipoprotein particles. We have previously demonstrated that the Liver X receptor (LXR)-regulated E3 ubiquitin ligase inducible degrader of LDLR (IDOL) is a regulator of cholesterol uptake owing to its ability to promote the ubiquitylation of the low-density lipoprotein receptor (LDLR). However, whether the LXR-IDOL-LDLR axis regulates the LDLR in the intestine and whether this influences intestinal cholesterol homeostasis is not known., Methods: In this study, we evaluated the role of the LXR-IDOL-LDLR axis in enterocyte cell models and in primary enterocytes isolated from Idol
(-/-) and wild type mice. Furthermore, we studied the regulation of intestinal LDLR in Idol(-/-) and in wild type mice treated with the LXR agonist GW3965. Finally, we assessed ezetimibe-induced trans-intestinal cholesterol efflux in Idol(-/-) mice., Results: We show that in a wide range of intestinal cell lines LXR activation decreases LDLR protein abundance, cell surface occupancy, and LDL uptake in an IDOL-dependent manner. Similarly, we find that pharmacological dosing of C57BL6/N mice with the LXR agonist GW3965 increases Idol expression across the intestine with a concomitant reduction in Ldlr protein. Conversely, primary enterocytes isolated from Idol(-/-) mice have elevated Ldlr. To test whether these changes contribute to trans-intestinal cholesterol efflux, we measured fecal cholesterol in mice following ezetimibe dosing, but found no differences between Idol(-/-) and control mice in this setting., Conclusions: In conclusion, our study establishes that the LXR-IDOL-LDLR axis is active in the intestine and is part of the molecular circuitry that maintains cholesterol homeostasis in enterocytes., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)- Published
- 2020
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45. Structural analysis of the LDL receptor-interacting FERM domain in the E3 ubiquitin ligase IDOL reveals an obscured substrate-binding site.
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Martinelli L, Adamopoulos A, Johansson P, Wan PT, Gunnarsson J, Guo H, Boyd H, Zelcer N, and Sixma TK
- Subjects
- Binding Sites, FERM Domains, Humans, Models, Molecular, Receptors, LDL chemistry, Substrate Specificity, Ubiquitin-Protein Ligases chemistry, Ubiquitin-Protein Ligases genetics, Receptors, LDL metabolism, Ubiquitin-Protein Ligases metabolism
- Abstract
Hepatic abundance of the low-density lipoprotein receptor (LDLR) is a critical determinant of circulating plasma LDL cholesterol levels and hence development of coronary artery disease. The sterol-responsive E3 ubiquitin ligase inducible degrader of the LDLR (IDOL) specifically promotes ubiquitination and subsequent lysosomal degradation of the LDLR and thus controls cellular LDL uptake. IDOL contains an extended N-terminal FERM (4.1 protein, ezrin, radixin, and moesin) domain, responsible for substrate recognition and plasma membrane association, and a second C-terminal RING domain, responsible for the E3 ligase activity and homodimerization. As IDOL is a putative lipid-lowering drug target, we investigated the molecular details of its substrate recognition. We produced and isolated full-length IDOL protein, which displayed high autoubiquitination activity. However, in vitro ubiquitination of its substrate, the intracellular tail of the LDLR, was low. To investigate the structural basis for this, we determined crystal structures of the extended FERM domain of IDOL and multiple conformations of its F3ab subdomain. These reveal the archetypal F1-F2-F3 trilobed FERM domain structure but show that the F3c subdomain orientation obscures the target-binding site. To substantiate this finding, we analyzed the full-length FERM domain and a series of truncated FERM constructs by small-angle X-ray scattering (SAXS). The scattering data support a compact and globular core FERM domain with a more flexible and extended C-terminal region. This flexibility may explain the low activity in vitro and suggests that IDOL may require activation for recognition of the LDLR., Competing Interests: Conflict of interest—The authors declare that they have no conflicts of interest with the contents of this article., (© 2020 Martinelli et al.)
- Published
- 2020
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46. The MARCH6-SQLE Axis Controls Endothelial Cholesterol Homeostasis and Angiogenic Sprouting.
- Author
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Tan JME, van der Stoel MM, van den Berg M, van Loon NM, Moeton M, Scholl E, van der Wel NN, Kovačević I, Hordijk PL, Loregger A, Huveneers S, and Zelcer N
- Subjects
- Adherens Junctions metabolism, Adherens Junctions ultrastructure, Antigens, CD metabolism, Cadherins metabolism, Gene Silencing, HEK293 Cells, Human Umbilical Vein Endothelial Cells ultrastructure, Humans, Cholesterol metabolism, Homeostasis, Human Umbilical Vein Endothelial Cells metabolism, Membrane Proteins metabolism, Neovascularization, Physiologic, Squalene Monooxygenase metabolism, Ubiquitin-Protein Ligases metabolism
- Abstract
The endothelial monolayer forms a barrier between the lumen of blood vessels and the underlying tissues. Stable VE-cadherin-based adherens junctions are essential for maintaining this barrier, whereas their remodeling is required for angiogenesis in health and disease. Here, we position the ERAD-associated ubiquitin ligase MARCH6 as a determinant of angiogenic sprouting and barrier integrity through its ability to promote the degradation of the rate-limiting cholesterol biosynthetic enzyme squalene epoxidase (SQLE). Accordingly, MARCHF6 ablation in endothelial cells increases SQLE protein and cholesterol load. This leads to altered membrane order, disorganized adherens junctions, decreased endothelial barrier function, and impaired SQLE-dependent sprouting angiogenesis. Akin to MARCHF6 silencing, the overexpression of SQLE impairs angiogenesis. However, angiogenesis is also attenuated when SQLE is silenced, indicating that fine-tuning cholesterol biosynthesis is a determinant of healthy endothelial function. In summary, we propose a mechanistic link between regulation of cholesterol homeostasis by the MARCH6-SQLE axis and endothelial integrity and angiogenesis., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2020
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47. Stearoyl-CoA desaturase-1 impairs the reparative properties of macrophages and microglia in the brain.
- Author
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Bogie JFJ, Grajchen E, Wouters E, Corrales AG, Dierckx T, Vanherle S, Mailleux J, Gervois P, Wolfs E, Dehairs J, Van Broeckhoven J, Bowman AP, Lambrichts I, Gustafsson JÅ, Remaley AT, Mulder M, Swinnen JV, Haidar M, Ellis SR, Ntambi JM, Zelcer N, and Hendriks JJA
- Subjects
- ATP Binding Cassette Transporter 1 metabolism, Animals, Cell Line, Cholesterol metabolism, Endocytosis, Fatty Acids metabolism, Foam Cells metabolism, Humans, Inflammation pathology, Macrophages metabolism, Macrophages ultrastructure, Mice, Microglia metabolism, Myelin Sheath metabolism, Phagocytes pathology, Phagocytes ultrastructure, Phenotype, Protein Kinase C-delta metabolism, Stearoyl-CoA Desaturase deficiency, Brain pathology, Macrophages enzymology, Microglia enzymology, Stearoyl-CoA Desaturase metabolism
- Abstract
Failure of remyelination underlies the progressive nature of demyelinating diseases such as multiple sclerosis. Macrophages and microglia are crucially involved in the formation and repair of demyelinated lesions. Here we show that myelin uptake temporarily skewed these phagocytes toward a disease-resolving phenotype, while sustained intracellular accumulation of myelin induced a lesion-promoting phenotype. This phenotypic shift was controlled by stearoyl-CoA desaturase-1 (SCD1), an enzyme responsible for the desaturation of saturated fatty acids. Monounsaturated fatty acids generated by SCD1 reduced the surface abundance of the cholesterol efflux transporter ABCA1, which in turn promoted lipid accumulation and induced an inflammatory phagocyte phenotype. Pharmacological inhibition or phagocyte-specific deficiency of Scd1 accelerated remyelination ex vivo and in vivo. These findings identify SCD1 as a novel therapeutic target to promote remyelination., Competing Interests: Disclosures: The authors declare no competing interests exist., (© 2020 Bogie et al.)
- Published
- 2020
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48. Haploid genetic screens identify SPRING/C12ORF49 as a determinant of SREBP signaling and cholesterol metabolism.
- Author
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Loregger A, Raaben M, Nieuwenhuis J, Tan JME, Jae LT, van den Hengel LG, Hendrix S, van den Berg M, Scheij S, Song JY, Huijbers IJ, Kroese LJ, Ottenhoff R, van Weeghel M, van de Sluis B, Brummelkamp T, and Zelcer N
- Subjects
- Animals, Cell Line, Embryonic Development genetics, Endoplasmic Reticulum metabolism, Gene Expression, Golgi Apparatus metabolism, Haploidy, Hepatocytes metabolism, Humans, Intracellular Signaling Peptides and Proteins genetics, Intracellular Signaling Peptides and Proteins metabolism, Lipid Metabolism genetics, Liver metabolism, Membrane Glycoproteins genetics, Membrane Proteins genetics, Mice, Mice, Inbred C57BL, Sterol Regulatory Element Binding Proteins genetics, Cholesterol metabolism, Membrane Glycoproteins metabolism, Membrane Proteins metabolism, Signal Transduction, Sterol Regulatory Element Binding Proteins metabolism
- Abstract
The sterol-regulatory element binding proteins (SREBP) are central transcriptional regulators of lipid metabolism. Using haploid genetic screens we identify the SREBP Regulating Gene (SPRING/C12ORF49) as a determinant of the SREBP pathway. SPRING is a glycosylated Golgi-resident membrane protein and its ablation in Hap1 cells, Hepa1-6 hepatoma cells, and primary murine hepatocytes reduces SREBP signaling. In mice, Spring deletion is embryonic lethal yet silencing of hepatic Spring expression also attenuates the SREBP response. Mechanistically, attenuated SREBP signaling in SPRING
KO cells results from reduced SREBP cleavage-activating protein (SCAP) and its mislocalization to the Golgi irrespective of the cellular sterol status. Consistent with limited functional SCAP in SPRINGKO cells, reintroducing SCAP restores SREBP-dependent signaling and function. Moreover, in line with the role of SREBP in tumor growth, a wide range of tumor cell lines display dependency on SPRING expression. In conclusion, we identify SPRING as a previously unrecognized modulator of SREBP signaling.- Published
- 2020
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49. Industrial Trans Fatty Acids Stimulate SREBP2-Mediated Cholesterogenesis and Promote Non-Alcoholic Fatty Liver Disease.
- Author
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Oteng AB, Loregger A, van Weeghel M, Zelcer N, and Kersten S
- Subjects
- 3T3-L1 Cells, Animals, CHO Cells, Carcinoma, Hepatocellular, Cell Line, Tumor, Cholesterol genetics, Cricetulus, Gene Expression drug effects, Intracellular Signaling Peptides and Proteins physiology, Liver drug effects, Liver metabolism, Liver pathology, Male, Membrane Proteins physiology, Mice, Mice, Inbred C57BL, Non-alcoholic Fatty Liver Disease metabolism, Non-alcoholic Fatty Liver Disease pathology, Oleic Acids pharmacology, Cholesterol biosynthesis, Dietary Fats pharmacology, Non-alcoholic Fatty Liver Disease chemically induced, Sterol Regulatory Element Binding Protein 2 physiology, Trans Fatty Acids pharmacology
- Abstract
Scope: The mechanisms underlying the deleterious effects of trans fatty acids on plasma cholesterol and non-alcoholic fatty liver disease (NAFLD) are unclear. Here, the aim is to investigate the molecular mechanisms of action of industrial trans fatty acids., Methods and Results: Hepa1-6 hepatoma cells were incubated with elaidate, oleate, or palmitate. C57Bl/6 mice were fed diets rich in trans-unsaturated, cis-unsaturated, or saturated fatty acids. Transcriptomics analysis of Hepa1-6 cells shows that elaidate but not oleate or palmitate induces expression of genes involved in cholesterol biosynthesis. Induction of cholesterogenesis by elaidate is mediated by increased sterol regulatory element-binding protein 2 (SREBP2) activity and is dependent on SREBP cleavage-activating protein (SCAP), yet independent of liver-X receptor and ubiquitin regulatory X domain-containing protein 8. Elaidate decreases intracellular free cholesterol levels and represses the anticholesterogenic effect of exogenous cholesterol. In mice, the trans-unsaturated diet increases the ratio of liver to gonadal fat mass, steatosis, hepatic cholesterol levels, alanine aminotransferase activity, and fibrosis markers, suggesting enhanced NAFLD, compared to the cis-unsaturated and saturated diets., Conclusion: Elaidate induces cholesterogenesis in vitro by activating the SCAP-SREBP2 axis, likely by lowering intracellular free cholesterol and attenuating cholesterol-dependent repression of SCAP. This pathway potentially underlies the increase in liver cholesterol and NAFLD by industrial trans fatty acids., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2019
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50. N-Glycosylation Defects in Humans Lower Low-Density Lipoprotein Cholesterol Through Increased Low-Density Lipoprotein Receptor Expression.
- Author
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van den Boogert MAW, Larsen LE, Ali L, Kuil SD, Chong PLW, Loregger A, Kroon J, Schnitzler JG, Schimmel AWM, Peter J, Levels JHM, Steenbergen G, Morava E, Dallinga-Thie GM, Wevers RA, Kuivenhoven JA, Hand NJ, Zelcer N, Rader DJ, Stroes ESG, Lefeber DJ, and Holleboom AG
- Subjects
- Child, Female, Humans, Male, Cholesterol, LDL genetics, Glycosylation, Receptors, LDL metabolism
- Abstract
Background: The importance of protein glycosylation in regulating lipid metabolism is becoming increasingly apparent. We set out to further investigate this by studying patients with type I congenital disorders of glycosylation (CDGs) with defective N-glycosylation., Methods: We studied 29 patients with the 2 most prevalent types of type I CDG, ALG6 (asparagine-linked glycosylation protein 6)-deficiency CDG and PMM2 (phosphomannomutase 2)-deficiency CDG, and 23 first- and second-degree relatives with a heterozygous mutation and measured plasma cholesterol levels. Low-density lipoprotein (LDL) metabolism was studied in 3 cell models-gene silencing in HepG2 cells, patient fibroblasts, and patient hepatocyte-like cells derived from induced pluripotent stem cells-by measuring apolipoprotein B production and secretion, LDL receptor expression and membrane abundance, and LDL particle uptake. Furthermore, SREBP2 (sterol regulatory element-binding protein 2) protein expression and activation and endoplasmic reticulum stress markers were studied., Results: We report hypobetalipoproteinemia (LDL cholesterol [LDL-C] and apolipoprotein B below the fifth percentile) in a large cohort of patients with type I CDG (mean age, 9 years), together with reduced LDL-C and apolipoprotein B in clinically unaffected heterozygous relatives (mean age, 46 years), compared with 2 separate sets of age- and sex-matched control subjects. ALG6 and PMM2 deficiency led to markedly increased LDL uptake as a result of increased cell surface LDL receptor abundance. Mechanistically, this outcome was driven by increased SREBP2 protein expression accompanied by amplified target gene expression, resulting in higher LDL receptor protein levels. Endoplasmic reticulum stress was not found to be a major mediator., Conclusions: Our study establishes N-glycosylation as an important regulator of LDL metabolism. Given that LDL-C was also reduced in a group of clinically unaffected heterozygotes, we propose that increasing LDL receptor-mediated cholesterol clearance by targeting N-glycosylation in the LDL pathway may represent a novel therapeutic strategy to reduce LDL-C and cardiovascular disease.
- Published
- 2019
- Full Text
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