1
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Sundaram MV, Pujol N. The Caenorhabditis elegans cuticle and precuticle: a model for studying dynamic apical extracellular matrices in vivo. Genetics 2024:iyae072. [PMID: 38995735 DOI: 10.1093/genetics/iyae072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 03/25/2024] [Indexed: 07/14/2024] Open
Abstract
Apical extracellular matrices (aECMs) coat the exposed surfaces of animal bodies to shape tissues, influence social interactions, and protect against pathogens and other environmental challenges. In the nematode Caenorhabditis elegans, collagenous cuticle and zona pellucida protein-rich precuticle aECMs alternately coat external epithelia across the molt cycle and play many important roles in the worm's development, behavior, and physiology. Both these types of aECMs contain many matrix proteins related to those in vertebrates, as well as some that are nematode-specific. Extensive differences observed among tissues and life stages demonstrate that aECMs are a major feature of epithelial cell identity. In addition to forming discrete layers, some cuticle components assemble into complex substructures such as ridges, furrows, and nanoscale pillars. The epidermis and cuticle are mechanically linked, allowing the epidermis to sense cuticle damage and induce protective innate immune and stress responses. The C. elegans model, with its optical transparency, facilitates the study of aECM cell biology and structure/function relationships and all the myriad ways by which aECM can influence an organism.
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Affiliation(s)
- Meera V Sundaram
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Nathalie Pujol
- Aix Marseille University, INSERM, CNRS, CIML, Turing Centre for Living Systems, 13009 Marseille, France
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2
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Harders RH, Morthorst TH, Landgrebe LE, Lande AD, Fuglsang MS, Mortensen SB, Feteira-Montero V, Jensen HH, Wesseltoft JB, Olsen A. CED-6/GULP and components of the clathrin-mediated endocytosis machinery act redundantly to correctly display CED-1 on the cell membrane in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2024; 14:jkae088. [PMID: 38696649 PMCID: PMC11228867 DOI: 10.1093/g3journal/jkae088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/03/2024] [Accepted: 04/16/2024] [Indexed: 05/04/2024]
Abstract
CED-1 (cell death abnormal) is a transmembrane receptor involved in the recognition of "eat-me" signals displayed on the surface of apoptotic cells and thus central for the subsequent engulfment of the cell corpse in Caenorhabditis elegans. The roles of CED-1 in engulfment are well established, as are its downstream effectors. The latter include the adapter protein CED-6/GULP and the ATP-binding cassette family homolog CED-7. However, how CED-1 is maintained on the plasma membrane in the absence of engulfment is currently unknown. Here, we show that CED-6 and CED-7 have a novel role in maintaining CED-1 correctly on the plasma membrane. We propose that the underlying mechanism is via endocytosis as CED-6 and CED-7 act redundantly with clathrin and its adaptor, the Adaptor protein 2 complex, in ensuring correct CED-1 localization. In conclusion, CED-6 and CED-7 impact other cellular processes than engulfment of apoptotic cells.
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Affiliation(s)
- Rikke Hindsgaul Harders
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, Aalborg, DK-9220, Denmark
| | - Tine H Morthorst
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus, DK-8000, Denmark
| | - Line E Landgrebe
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus, DK-8000, Denmark
| | - Anna D Lande
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus, DK-8000, Denmark
| | - Marie Sikjær Fuglsang
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus, DK-8000, Denmark
| | - Stine Bothilde Mortensen
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, Aalborg, DK-9220, Denmark
| | - Verónica Feteira-Montero
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, Aalborg, DK-9220, Denmark
| | - Helene Halkjær Jensen
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, Aalborg, DK-9220, Denmark
| | - Jonas Bruhn Wesseltoft
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, Aalborg, DK-9220, Denmark
| | - Anders Olsen
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, Aalborg, DK-9220, Denmark
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3
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Binti S, Edeen PT, Fay DS. Loss of the Na + /K + cation pump CATP-1 suppresses nekl -associated molting defects. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.15.585189. [PMID: 38559007 PMCID: PMC10979969 DOI: 10.1101/2024.03.15.585189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The conserved C. elegans protein kinases NEKL-2 and NEKL-3 regulate multiple steps of membrane trafficking and are required for larval molting. Through a forward genetic screen we identified a loss-of-function mutation in catp-1 as a suppressor of molting defects in synthetically lethal nekl-2; nekl-3 double mutants. catp-1 is predicted to encode a membrane- associated P4-type ATPase involved in Na + -K + exchange. Moreover, a mutation predicted to abolish CATP-1 ion-pump activity also suppressed nekl-2; nekl-3 mutants. Endogenously tagged CATP-1 was primarily expressed in epidermal (hypodermal) cells within punctate structures located at or near the apical plasma membrane. Through whole genome sequencing, we identified two additional nekl-2; nekl-3 suppressor strains containing coding-altering mutations in catp-1 but found that neither mutation, when introduced into nekl-2; nekl-3 mutants using CRISPR methods, was sufficient to elicit robust suppression of molting defects. Our data also suggested that the two catp-1 isoforms, catp-1a and catp-1b , may in some contexts be functionally redundant. On the basis of previously published studies, we tested the hypothesis that loss of catp-1 may suppress nekl -associated defects by inducing partial entry into the dauer pathway. Contrary to expectations, however, we failed to obtain evidence that loss of catp-1 suppresses nekl-2; nekl-3 defects through a dauer-associated mechanism or that loss of catp-1 leads to entry into the pre-dauer L2d stage. As such, loss of catp-1 may suppress nekl- associated molting and membrane trafficking defects by altering electrochemical gradients within membrane-bound compartments.
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4
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Joseph BB, Edeen PT, Meadows S, Binti S, Fay DS. An unexpected role for the conserved ADAM-family metalloprotease ADM-2 in Caenorhabditis elegans molting. PLoS Genet 2022; 18:e1010249. [PMID: 35639786 PMCID: PMC9187072 DOI: 10.1371/journal.pgen.1010249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 06/10/2022] [Accepted: 05/11/2022] [Indexed: 11/18/2022] Open
Abstract
Molting is a widespread developmental process in which the external extracellular matrix (ECM), the cuticle, is remodeled to allow for organismal growth and environmental adaptation. Studies in the nematode Caenorhabditis elegans have identified a diverse set of molting-associated factors including signaling molecules, intracellular trafficking regulators, ECM components, and ECM-modifying enzymes such as matrix metalloproteases. C. elegans NEKL-2 and NEKL-3, two conserved members of the NEK family of protein kinases, are essential for molting and promote the endocytosis of environmental steroid-hormone precursors by the epidermis. Steroids in turn drive the cyclic induction of many genes required for molting. Here we report a role for the sole C. elegans ADAM–meltrin metalloprotease family member, ADM-2, as a mediator of molting. Loss of adm-2, including mutations that disrupt the metalloprotease domain, led to the strong suppression of molting defects in partial loss-of-function nekl mutants. ADM-2 is expressed in the epidermis, and its trafficking through the endo-lysosomal network was disrupted after NEKL depletion. We identified the epidermally expressed low-density lipoprotein receptor–related protein, LRP-1, as a candidate target of ADM-2 regulation. Whereas loss of ADM-2 activity led to the upregulation of apical epidermal LRP-1, ADM-2 overexpression caused a reduction in LRP-1 levels. Consistent with this, several mammalian ADAMs, including the meltrin ADAM12, have been shown to regulate mammalian LRP1 via proteolysis. In contrast to mammalian homologs, however, the regulation of LRP-1 by ADM-2 does not appear to involve the metalloprotease function of ADM-2, nor is proteolytic processing of LRP-1 strongly affected in adm-2 mutants. Our findings suggest a noncanonical role for an ADAM family member in the regulation of a lipoprotein-like receptor and lead us to propose that endocytic trafficking may be important for both the internalization of factors that promote molting as well as the removal of proteins that can inhibit the process. The molecular and cellular features of molting in nematodes share many similarities with cellular and developmental processes that occur in mammals. This includes the degradation and reorganization of extracellular matrix materials that surround cells, as well as the intracellular machineries that allow cells to sample and modify their environments. In the current study, we found an unexpected function for a conserved protein that cleaves other proteins on the external surface of cells. Rather than promoting molting through extracellular matrix reorganization, however, the ADM-2 protease appears to function as a negative regulator of molting. This observation can be explained in part by data showing that ADM-2 negatively regulates a cell surface receptor required for molting. Surprisingly, it appears to do so through a mechanism that does not involve proteolysis. Our data provide insights into the mechanisms controlling molting and link several conserved proteins to show how they function together during development.
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Affiliation(s)
- Braveen B. Joseph
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Phillip T. Edeen
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Sarina Meadows
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Shaonil Binti
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - David S. Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
- * E-mail:
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5
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Langridge PD, Garcia Diaz A, Chan JY, Greenwald I, Struhl G. Evolutionary plasticity in the requirement for force exerted by ligand endocytosis to activate C. elegans Notch proteins. Curr Biol 2022; 32:2263-2271.e6. [PMID: 35349791 PMCID: PMC9133158 DOI: 10.1016/j.cub.2022.03.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/28/2022] [Accepted: 03/08/2022] [Indexed: 10/18/2022]
Abstract
The conserved transmembrane receptor Notch has diverse and profound roles in controlling cell fate during animal development. In the absence of ligand, a negative regulatory region (NRR) in the Notch ectodomain adopts an autoinhibited confirmation, masking an ADAM protease cleavage site;1,2 ligand binding induces cleavage of the NRR, leading to Notch ectodomain shedding as the first step of signal transduction.3,4 In Drosophila and vertebrates, recruitment of transmembrane Delta/Serrate/LAG-2 (DSL) ligands by the endocytic adaptor Epsin, and their subsequent internalization by Clathrin-mediated endocytosis, exerts a "pulling force" on Notch that is essential to expose the cleavage site in the NRR.4-6 Here, we show that Epsin-mediated endocytosis of transmembrane ligands is not essential to activate the two C. elegans Notch proteins, LIN-12 and GLP-1. Using an in vivo force sensing assay in Drosophila,6 we present evidence (1) that the LIN-12 and GLP-1 NRRs are tuned to lower force thresholds than the NRR of Drosophila Notch, and (2) that this difference depends on the absence of a "leucine plug" that occludes the cleavage site in the Drosophila and vertebrate Notch NRRs.1,2 Our results thus establish an unexpected evolutionary plasticity in the force-dependent mechanism of Notch activation and implicate a specific structural element, the leucine plug, as a determinant.
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Affiliation(s)
- Paul D Langridge
- Department of Genetics and Development, Columbia University, New York, NY 10027, USA; Mortimer B. Zuckerman Mind Brain Behavior Institute, New York, NY 10027, USA.
| | | | - Jessica Yu Chan
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Iva Greenwald
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
| | - Gary Struhl
- Department of Genetics and Development, Columbia University, New York, NY 10027, USA; Mortimer B. Zuckerman Mind Brain Behavior Institute, New York, NY 10027, USA.
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6
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Cui K, Dong Y, Wang B, Cowan DB, Chan SL, Shyy J, Chen H. Endocytic Adaptors in Cardiovascular Disease. Front Cell Dev Biol 2020; 8:624159. [PMID: 33363178 PMCID: PMC7759532 DOI: 10.3389/fcell.2020.624159] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Endocytosis is the process of actively transporting materials into a cell by membrane engulfment. Traditionally, endocytosis was divided into three forms: phagocytosis (cell eating), pinocytosis (cell drinking), and the more selective receptor-mediated endocytosis (clathrin-mediated endocytosis); however, other important endocytic pathways (e.g., caveolin-dependent endocytosis) contribute to the uptake of extracellular substances. In each, the plasma membrane changes shape to allow the ingestion and internalization of materials, resulting in the formation of an intracellular vesicle. While receptor-mediated endocytosis remains the best understood pathway, mammalian cells utilize each form of endocytosis to respond to their environment. Receptor-mediated endocytosis permits the internalization of cell surface receptors and their ligands through a complex membrane invagination process that is facilitated by clathrin and adaptor proteins. Internalized vesicles containing these receptor-ligand cargoes fuse with early endosomes, which can then be recycled back to the plasma membrane, delivered to other cellular compartments, or destined for degradation by fusing with lysosomes. These intracellular fates are largely determined by the interaction of specific cargoes with adaptor proteins, such as the epsins, disabled-homolog 2 (Dab2), the stonin proteins, epidermal growth factor receptor substrate 15, and adaptor protein 2 (AP-2). In this review, we focus on the role of epsins and Dab2 in controlling these sorting processes in the context of cardiovascular disease. In particular, we will focus on the function of epsins and Dab2 in inflammation, cholesterol metabolism, and their fundamental contribution to atherogenicity.
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Affiliation(s)
- Kui Cui
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - Yunzhou Dong
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - Beibei Wang
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - Douglas B Cowan
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States.,Department of Cardiology, Boston Children's Hospital, Boston, MA, United States
| | - Siu-Lung Chan
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - John Shyy
- Division of Cardiology, Department of Medicine, University of California, San Diego, San Diego, CA, United States
| | - Hong Chen
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
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7
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Joseph BB, Wang Y, Edeen P, Lažetić V, Grant BD, Fay DS. Control of clathrin-mediated endocytosis by NIMA family kinases. PLoS Genet 2020; 16:e1008633. [PMID: 32069276 PMCID: PMC7048319 DOI: 10.1371/journal.pgen.1008633] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 02/28/2020] [Accepted: 01/28/2020] [Indexed: 12/16/2022] Open
Abstract
Endocytosis, the process by which cells internalize plasma membrane and associated cargo, is regulated extensively by posttranslational modifications. Previous studies suggested the potential involvement of scores of protein kinases in endocytic control, of which only a few have been validated in vivo. Here we show that the conserved NIMA-related kinases NEKL-2/NEK8/9 and NEKL-3/NEK6/7 (the NEKLs) control clathrin-mediated endocytosis in C. elegans. Loss of NEKL-2 or NEKL-3 activities leads to penetrant larval molting defects and to the abnormal localization of trafficking markers in arrested larvae. Using an auxin-based degron system, we also find that depletion of NEKLs in adult-stage C. elegans leads to gross clathrin mislocalization and to a dramatic reduction in clathrin mobility at the apical membrane. Using a non-biased genetic screen to identify suppressors of nekl molting defects, we identified several components and regulators of AP2, the major clathrin adapter complex acting at the plasma membrane. Strikingly, reduced AP2 activity rescues both nekl mutant molting defects as well as associated trafficking phenotypes, whereas increased levels of active AP2 exacerbate nekl defects. Moreover, in a unique example of mutual suppression, NEKL inhibition alleviates defects associated with reduced AP2 activity, attesting to the tight link between NEKL and AP2 functions. We also show that NEKLs are required for the clustering and internalization of membrane cargo required for molting. Notably, we find that human NEKs can rescue molting and trafficking defects in nekl mutant worms, suggesting that the control of intracellular trafficking is an evolutionarily conserved function of NEK family kinases. In order to function properly, cells must continually import materials from the outside. This process, termed endocytosis, is necessary for the uptake of nutrients and for interpreting signals coming from the external environment or from within the body. These signals are critical during animal development but also affect many types of cell behaviors throughout life. In our current work, we show that several highly conserved proteins in the nematode Caenorhabditis elegans, NEKL-2 and NEKL-3, regulate endocytosis. The human counterparts of NEKL-2 and NEKL-3 have been implicated in cardiovascular and renal diseases as well as many types of cancers. However, their specific functions within cells is incompletely understood and very little is known about their role in endocytosis or how this role might impact disease processes. Here we use several complementary approaches to characterize the specific functions of C. elegans NEKL-2 and NEKL-3 in endocytosis and show that their human counterparts likely have very similar functions. This work paves the way to a better understanding of fundamental biological processes and to determining the cellular functions of proteins connected to human diseases.
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Affiliation(s)
- Braveen B. Joseph
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Yu Wang
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Phil Edeen
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Vladimir Lažetić
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Barth D. Grant
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - David S. Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
- * E-mail:
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8
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Brophy ML, Dong Y, Tao H, Yancey PG, Song K, Zhang K, Wen A, Wu H, Lee Y, Malovichko MV, Sithu SD, Wong S, Yu L, Kocher O, Bischoff J, Srivastava S, Linton MF, Ley K, Chen H. Myeloid-Specific Deletion of Epsins 1 and 2 Reduces Atherosclerosis by Preventing LRP-1 Downregulation. Circ Res 2019; 124:e6-e19. [PMID: 30595089 DOI: 10.1161/circresaha.118.313028] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
RATIONALE Atherosclerosis is, in part, caused by immune and inflammatory cell infiltration into the vascular wall, leading to enhanced inflammation and lipid accumulation in the aortic endothelium. Understanding the molecular mechanisms underlying this disease is critical for the development of new therapies. Our recent studies demonstrate that epsins, a family of ubiquitin-binding endocytic adaptors, are critical regulators of atherogenicity. Given the fundamental contribution lesion macrophages make to fuel atherosclerosis, whether and how myeloid-specific epsins promote atherogenesis is an open and significant question. OBJECTIVE We will determine the role of myeloid-specific epsins in regulating lesion macrophage function during atherosclerosis. METHODS AND RESULTS We engineered myeloid cell-specific epsins double knockout mice (LysM-DKO) on an ApoE-/- background. On Western diet, these mice exhibited marked decrease in atherosclerotic lesion formation, diminished immune and inflammatory cell content in aortas, and reduced necrotic core content but increased smooth muscle cell content in aortic root sections. Epsins deficiency hindered foam cell formation and suppressed proinflammatory macrophage phenotype but increased efferocytosis and anti-inflammatory macrophage phenotype in primary macrophages. Mechanistically, we show that epsin loss specifically increased total and surface levels of LRP-1 (LDLR [low-density lipoprotein receptor]-related protein 1), an efferocytosis receptor with antiatherosclerotic properties. We further show that epsin and LRP-1 interact via epsin's ubiquitin-interacting motif domain. ox-LDL (oxidized LDL) treatment increased LRP-1 ubiquitination, subsequent binding to epsin, and its internalization from the cell surface, suggesting that epsins promote the ubiquitin-dependent internalization and downregulation of LRP-1. Crossing ApoE-/-/LysM-DKO mice onto an LRP-1 heterozygous background restored, in part, atherosclerosis, suggesting that epsin-mediated LRP-1 downregulation in macrophages plays a pivotal role in propelling atherogenesis. CONCLUSIONS Myeloid epsins promote atherogenesis by facilitating proinflammatory macrophage recruitment and inhibiting efferocytosis in part by downregulating LRP-1, implicating that targeting epsins in macrophages may serve as a novel therapeutic strategy to treat atherosclerosis.
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Affiliation(s)
- Megan L Brophy
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center (M.L.B.)
| | - Yunzhou Dong
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Huan Tao
- Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN (H.T., P.G.Y., M.F.L.)
| | - Patricia G Yancey
- Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN (H.T., P.G.Y., M.F.L.)
| | - Kai Song
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Kun Zhang
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA.,Department of Cardiology, Sun Yat-sen Memorial Hospital of Sun Yat-sen University, Guangzhou, China (K.Z.)
| | - Aiyun Wen
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Hao Wu
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Yang Lee
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Marina V Malovichko
- Division of Cardiovascular Medicine, Department of Medicine, University of Louisville, KY (M.V.M., S.D.S., S.S.)
| | - Srinivas D Sithu
- Division of Cardiovascular Medicine, Department of Medicine, University of Louisville, KY (M.V.M., S.D.S., S.S.)
| | - Scott Wong
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Lili Yu
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Olivier Kocher
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Medical Deaconess Medical Center (O.K.), Harvard Medical School, MA
| | - Joyce Bischoff
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
| | - Sanjay Srivastava
- Division of Cardiovascular Medicine, Department of Medicine, University of Louisville, KY (M.V.M., S.D.S., S.S.)
| | - MacRae F Linton
- Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN (H.T., P.G.Y., M.F.L.)
| | - Klaus Ley
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, CA (K.L.)
| | - Hong Chen
- From the Vascular Biology Program and Department of Surgery, Boston Children's Hospital (M.L.B., Y.D., K.S., K.Z., A.W., H.W., Y.L., S.W., L.Y., J.B., H.C.), Harvard Medical School, MA
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9
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Zuidema A, Wang W, Kreft M, Te Molder L, Hoekman L, Bleijerveld OB, Nahidiazar L, Janssen H, Sonnenberg A. Mechanisms of integrin αVβ5 clustering in flat clathrin lattices. J Cell Sci 2018; 131:jcs221317. [PMID: 30301780 DOI: 10.1242/jcs.221317] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/27/2018] [Indexed: 12/17/2023] Open
Abstract
The family of integrin transmembrane receptors is essential for the normal function of multicellular organisms by facilitating cell-extracellular matrix adhesion. The vitronectin-binding integrin αVβ5 localizes to focal adhesions (FAs) as well as poorly characterized flat clathrin lattices (FCLs). Here, we show that, in human keratinocytes, αVβ5 is predominantly found in FCLs, and formation of the αVβ5-containing FCLs requires the presence of vitronectin as ligand, Ca2+, and the clathrin adaptor proteins ARH (also known as LDLRAP1), Numb and EPS15/EPS15L1. Integrin chimeras, containing the extracellular and transmembrane domains of β5 and the cytoplasmic domains of β1 or β3, almost exclusively localize in FAs. Interestingly, lowering actomyosin-mediated contractility promotes integrin redistribution to FLCs in an integrin tail-dependent manner, while increasing cellular tension favors αVβ5 clustering in FAs. Our findings strongly indicate that clustering of integrin αVβ5 in FCLs is dictated by the β5 subunit cytoplasmic domain, cellular tension and recruitment of specific adaptor proteins to the β5 subunit cytoplasmic domains.
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Affiliation(s)
- Alba Zuidema
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Wei Wang
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Maaike Kreft
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Lisa Te Molder
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Liesbeth Hoekman
- Mass spectrometry/Proteomics Facility, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Onno B Bleijerveld
- Mass spectrometry/Proteomics Facility, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Leila Nahidiazar
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Hans Janssen
- Electron Microscopy Facility, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
| | - Arnoud Sonnenberg
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands
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10
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Lažetić V, Joseph BB, Bernazzani SM, Fay DS. Actin organization and endocytic trafficking are controlled by a network linking NIMA-related kinases to the CDC-42-SID-3/ACK1 pathway. PLoS Genet 2018; 14:e1007313. [PMID: 29608564 PMCID: PMC5897031 DOI: 10.1371/journal.pgen.1007313] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 04/12/2018] [Accepted: 03/19/2018] [Indexed: 01/07/2023] Open
Abstract
Molting is an essential process in the nematode Caenorhabditis elegans during which the epidermal apical extracellular matrix, termed the cuticle, is detached and replaced at each larval stage. The conserved NIMA-related kinases NEKL-2/NEK8/NEK9 and NEKL-3/NEK6/NEK7, together with their ankyrin repeat partners, MLT-2/ANKS6, MLT-3/ANKS3, and MLT-4/INVS, are essential for normal molting. In nekl and mlt mutants, the old larval cuticle fails to be completely shed, leading to entrapment and growth arrest. To better understand the molecular and cellular functions of NEKLs during molting, we isolated genetic suppressors of nekl molting-defective mutants. Using two independent approaches, we identified CDC-42, a conserved Rho-family GTPase, and its effector protein kinase, SID-3/ACK1. Notably, CDC42 and ACK1 regulate actin dynamics in mammals, and actin reorganization within the worm epidermis has been proposed to be important for the molting process. Inhibition of NEKL-MLT activities led to strong defects in the distribution of actin and failure to form molting-specific apical actin bundles. Importantly, this phenotype was reverted following cdc-42 or sid-3 inhibition. In addition, repression of CDC-42 or SID-3 also suppressed nekl-associated defects in trafficking, a process that requires actin assembly and disassembly. Expression analyses indicated that components of the NEKL-MLT network colocalize with both actin and CDC-42 in specific regions of the epidermis. Moreover, NEKL-MLT components were required for the normal subcellular localization of CDC-42 in the epidermis as well as wild-type levels of CDC-42 activation. Taken together, our findings indicate that the NEKL-MLT network regulates actin through CDC-42 and its effector SID-3. Interestingly, we also observed that downregulation of CDC-42 in a wild-type background leads to molting defects, suggesting that there is a fine balance between NEKL-MLT and CDC-42-SID-3 activities in the epidermis.
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Affiliation(s)
- Vladimir Lažetić
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY
| | - Braveen B. Joseph
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY
| | - Sarina M. Bernazzani
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY
| | - David S. Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY
- * E-mail:
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11
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Lažetić V, Fay DS. Molting in C. elegans. WORM 2017; 6:e1330246. [PMID: 28702275 DOI: 10.1080/21624054.2017.1330246] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 05/01/2017] [Accepted: 05/09/2017] [Indexed: 12/21/2022]
Abstract
Molting is an essential developmental process for the majority of animal species on Earth. During the molting process, which is a specialized form of extracellular matrix (ECM) remodeling, the old apical ECM, or cuticle, is replaced with a new one. Many of the genes and pathways identified as important for molting in nematodes are highly conserved in vertebrates and include regulators and components of vesicular trafficking, steroid-hormone signaling, developmental timers, and hedgehog-like signaling. In this review, we discuss what is known about molting, with a focus on studies in Caenorhabditis elegans. We also describe the key structural elements of the cuticle that must be released, newly synthesized, or remodeled for proper molting to occur.
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Affiliation(s)
- Vladimir Lažetić
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY, USA
| | - David S Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY, USA
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12
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Lažetić V, Fay DS. Conserved Ankyrin Repeat Proteins and Their NIMA Kinase Partners Regulate Extracellular Matrix Remodeling and Intracellular Trafficking in Caenorhabditis elegans. Genetics 2017; 205:273-293. [PMID: 27799278 PMCID: PMC5223508 DOI: 10.1534/genetics.116.194464] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/28/2016] [Indexed: 12/27/2022] Open
Abstract
Molting is an essential developmental process in nematodes during which the epidermal apical extracellular matrix, the cuticle, is remodeled to accommodate further growth. Using genetic approaches, we identified a requirement for three conserved ankyrin repeat-rich proteins, MLT-2/ANKS6, MLT-3/ANKS3, and MLT-4/INVS, in Caenorhabditis elegans molting. Loss of mlt function resulted in severe defects in the ability of larvae to shed old cuticle and led to developmental arrest. Genetic analyses demonstrated that MLT proteins functionally cooperate with the conserved NIMA kinase family members NEKL-2/NEK8 and NEKL-3/NEK6/NEK7 to promote cuticle shedding. MLT and NEKL proteins were specifically required within the hyp7 epidermal syncytium, and fluorescently tagged mlt and nekl alleles were expressed in puncta within this tissue. Expression studies further showed that NEKL-2-MLT-2-MLT-4 and NEKL-3-MLT-3 colocalize within largely distinct assemblies of apical foci. MLT-2 and MLT-4 were required for the normal accumulation of NEKL-2 at the hyp7-seam cell boundary, and loss of mlt-2 caused abnormal nuclear accumulation of NEKL-2 Correspondingly, MLT-3, which bound directly to NEKL-3, prevented NEKL-3 nuclear localization, supporting the model that MLT proteins may serve as molecular scaffolds for NEKL kinases. Our studies additionally showed that the NEKL-MLT network regulates early steps in clathrin-mediated endocytosis at the apical surface of hyp7, which may in part account for molting defects observed in nekl and mlt mutants. This study has thus identified a conserved NEKL-MLT protein network that regulates remodeling of the apical extracellular matrix and intracellular trafficking, functions that may be conserved across species.
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Affiliation(s)
- Vladimir Lažetić
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming 82071
| | - David S Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming 82071
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13
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Epsin1 modulates synaptic vesicle retrieval capacity at CNS synapses. Sci Rep 2016; 6:31997. [PMID: 27557559 PMCID: PMC4997357 DOI: 10.1038/srep31997] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/01/2016] [Indexed: 11/08/2022] Open
Abstract
Synaptic vesicle retrieval is an essential process for continuous maintenance of neural information flow after synaptic transmission. Epsin1, originally identified as an EPS15-interacting protein, is a major component of clathrin-mediated endocytosis. However, the role of Epsin1 in synaptic vesicle endocytosis at CNS synapses remains elusive. Here, we showed significantly altered synaptic vesicle endocytosis in neurons transfected with shRNA targeting Epsin1 during/after neural activity. Endocytosis was effectively restored by introducing shRNA-insensitive Epsin1 into Epsin1-depleted neurons. Domain studies performed on neurons in which domain deletion mutants of Epsin1 were introduced after Epsin1 knockdown revealed that ENTH, CLAP, and NPFs are essential for synaptic vesicle endocytosis, whereas UIMs are not. Strikingly, the efficacy of the rate of synaptic vesicle retrieval (the "endocytic capacity") was significantly decreased in the absence of Epsin1. Thus, Epsin1 is required for proper synaptic vesicle retrieval and modulates the endocytic capacity of synaptic vesicles.
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Wang L, Johnson A, Hanna M, Audhya A. Eps15 membrane-binding and -bending activity acts redundantly with Fcho1 during clathrin-mediated endocytosis. Mol Biol Cell 2016; 27:2675-87. [PMID: 27385343 PMCID: PMC5007088 DOI: 10.1091/mbc.e16-03-0151] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 06/29/2016] [Indexed: 11/11/2022] Open
Abstract
Clathrin-mediated endocytosis involves a network of proteins that direct cargo capture while simultaneously facilitating membrane remodeling. Eps15 is a critical factor that binds and bends membranes and acts redundantly with Fcho1 to ensure clathrin lattice stability during the initial stages of plasma membrane invagination. Clathrin coat assembly on membranes requires cytosolic adaptors and accessory proteins, which bridge triskeleons with the lipid bilayer and stabilize lattice architecture throughout the process of vesicle formation. In Caenorhabditis elegans, the prototypical AP-2 adaptor complex, which is activated by the accessory factor Fcho1 at the plasma membrane, is dispensable during embryogenesis, enabling us to define alternative mechanisms that facilitate clathrin-mediated endocytosis. Here we uncover a synthetic genetic interaction between C. elegans Fcho1 (FCHO-1) and Eps15 (EHS-1), suggesting that they function in a parallel and potentially redundant manner. Consistent with this idea, we find that the FCHO-1 EFC/F-BAR domain and the EHS-1 EH domains exhibit highly similar membrane-binding and -bending characteristics in vitro. Furthermore, we demonstrate a critical role for EHS-1 when FCHO-1 membrane-binding and -bending activity is specifically eliminated in vivo. Taken together, our data highlight Eps15 as an important membrane-remodeling factor, which acts in a partially redundant manner with Fcho proteins during the earliest stages of clathrin-mediated endocytosis.
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Affiliation(s)
- Lei Wang
- Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706
| | - Adam Johnson
- Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706
| | - Michael Hanna
- Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706
| | - Anjon Audhya
- Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706
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Imae R, Dejima K, Kage-Nakadai E, Arai H, Mitani S. Endomembrane-associated RSD-3 is important for RNAi induced by extracellular silencing RNA in both somatic and germ cells of Caenorhabditis elegans. Sci Rep 2016; 6:28198. [PMID: 27306325 PMCID: PMC4910058 DOI: 10.1038/srep28198] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/01/2016] [Indexed: 12/25/2022] Open
Abstract
RNA silencing signals in C. elegans spread among cells, leading to RNAi
throughout the body. During systemic spread of RNAi, membrane trafficking is thought
to play important roles. Here, we show that RNAi Spreading Defective-3
(rsd-3), which encodes a homolog of epsinR, a conserved ENTH (epsin
N-terminal homology) domain protein, generally participates in cellular uptake of
silencing RNA. RSD-3 is previously thought to be involved in systemic RNAi only in
germ cells, but we isolated several deletion alleles of rsd-3, and found that
these mutants are defective in the spread of silencing RNA not only into germ cells
but also into somatic cells. RSD-3 is ubiquitously expressed, and intracellularly
localized to the trans-Golgi network (TGN) and endosomes. Tissue-specific
rescue experiments indicate that RSD-3 is required for importing silencing RNA into
cells rather than exporting from cells. Structure/function analysis showed that the
ENTH domain alone is sufficient, and membrane association of the ENTH domain is
required, for RSD-3 function in systemic RNAi. Our results suggest that endomembrane
trafficking through the TGN and endosomes generally plays an important role in
cellular uptake of silencing RNA.
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Affiliation(s)
- Rieko Imae
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Katsufumi Dejima
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Eriko Kage-Nakadai
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Hiroyuki Arai
- Graduate School of Pharmaceutical Science, University of Tokyo, Tokyo, Japan
| | - Shohei Mitani
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.,Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan
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16
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A MARCH6 and IDOL E3 Ubiquitin Ligase Circuit Uncouples Cholesterol Synthesis from Lipoprotein Uptake in Hepatocytes. Mol Cell Biol 2015; 36:285-94. [PMID: 26527619 DOI: 10.1128/mcb.00890-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 10/27/2015] [Indexed: 11/20/2022] Open
Abstract
Cholesterol synthesis and lipoprotein uptake are tightly coordinated to ensure that the cellular level of cholesterol is adequately maintained. Hepatic dysregulation of these processes is associated with pathological conditions, most notably cardiovascular disease. Using a genetic approach, we have recently identified the E3 ubiquitin ligase MARCH6 as a regulator of cholesterol biosynthesis, owing to its ability to promote degradation of the rate-limiting enzymes 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGCR) and squalene epoxidase (SQLE). Here, we present evidence for MARCH6 playing a multifaceted role in the control of cholesterol homeostasis in hepatocytes. We identify MARCH6 as an endogenous inhibitor of the sterol regulatory element binding protein (SREBP) transcriptional program. Accordingly, loss of MARCH6 increases expression of SREBP-regulated genes involved in cholesterol biosynthesis and lipoprotein uptake. Unexpectedly, this is associated with a decrease in cellular lipoprotein uptake, induced by enhanced lysosomal degradation of the low-density lipoprotein receptor (LDLR). Finally, we provide evidence that induction of the E3 ubiquitin ligase IDOL represents the molecular mechanism underlying this MARCH6-induced phenotype. Our study thus highlights a MARCH6-dependent mechanism to direct cellular cholesterol accretion that relies on uncoupling of cholesterol synthesis from lipoprotein uptake.
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18
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Yochem J, Lažetić V, Bell L, Chen L, Fay D. C. elegans NIMA-related kinases NEKL-2 and NEKL-3 are required for the completion of molting. Dev Biol 2015; 398:255-66. [PMID: 25523392 PMCID: PMC4314388 DOI: 10.1016/j.ydbio.2014.12.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 11/29/2014] [Accepted: 12/04/2014] [Indexed: 12/20/2022]
Abstract
Caenorhabditis elegans molting is a process during which the apical extracellular matrix of the epidermis, the cuticle, is remodeled through a process of degradation and re-synthesis. Using a genetic approach, we identified nekl-3 as essential for the completion of molting. NEKL-3 is highly similar to the mammalian NEK kinase family members NEK6 and NEK7. Animals homozygous for a hypomorphic mutation in nekl-3, sv3, had a novel molting defect in which the central body region, but not the head or tail, was unable to shed the old cuticle. In contrast, a null mutation in nekl-3, gk506, led to complete enclosure within the old cuticle. nekl-2, which is most similar to mammalian NEK8, was also essential for molting. Mosaic analyses demonstrated that NEKL-2 and NEKL-3 were specifically required within the large epidermal syncytium, hyp7, to facilitate molting. Consistent with this, NEKL-2 and NEKL-3 were expressed at the apical surface of hyp7 where they localized to small spheres or tubular structures. Inhibition of nekl-2, but not nekl-3, led to the mislocalization of LRP-1/megalin, a cell surface receptor for low-density lipoprotein (LDL)-binding proteins. In addition, nekl-2 inhibition led to the mislocalization of several other endosome-associated proteins. Notably, LRP-1 acts within hyp7 to facilitate completion of molting, suggesting at least one mechanism by which NEKL-2 may influence molting. Notably, our studies failed to reveal a requirement for NEKL-2 or NEKL-3 in cell division, a function reported for several mammalian NEKs including NEK6 and NEK7. Our findings provide the first genetic and in vivo evidence for a role of NEK family members in endocytosis, which may be evolutionarily conserved.
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Affiliation(s)
- John Yochem
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY 82071, United States; Department of Genetics, Cell Biology, and Development and the Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, United States
| | - Vladimir Lažetić
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY 82071, United States
| | - Leslie Bell
- Department of Genetics, Cell Biology, and Development and the Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, United States
| | - Lihsia Chen
- Department of Genetics, Cell Biology, and Development and the Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, United States
| | - David Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, WY 82071, United States.
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Abstract
The counterbalancing action of the endocytosis and secretory pathways maintains a dynamic equilibrium that regulates the composition of the plasma membrane, allowing it to maintain homeostasis and to change rapidly in response to alterations in the extracellular environment and/or intracellular metabolism. These pathways are intimately integrated with intercellular signaling systems and play critical roles in all cells. Studies in Caenorhabditis elegans have revealed diverse roles of membrane trafficking in physiology and development and have also provided molecular insight into the fundamental mechanisms that direct cargo sorting, vesicle budding, and membrane fisson and fusion. In this review, we summarize progress in understanding membrane trafficking mechanisms derived from work in C. elegans, focusing mainly on work done in non-neuronal cell-types, especially the germline, early embryo, coelomocytes, and intestine.
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Affiliation(s)
- Ken Sato
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan. ;
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20
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Piper RC, Dikic I, Lukacs GL. Ubiquitin-dependent sorting in endocytosis. Cold Spring Harb Perspect Biol 2014; 6:6/1/a016808. [PMID: 24384571 DOI: 10.1101/cshperspect.a016808] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
When ubiquitin (Ub) is attached to membrane proteins on the plasma membrane, it directs them through a series of sorting steps that culminate in their delivery to the lumen of the lysosome where they undergo complete proteolysis. Ubiquitin is recognized by a series of complexes that operate at a number of vesicle transport steps. Ubiquitin serves as a sorting signal for internalization at the plasma membrane and is the major signal for incorporation into intraluminal vesicles of multivesicular late endosomes. The sorting machineries that catalyze these steps can bind Ub via a variety of Ub-binding domains. At the same time, many of these complexes are themselves ubiquitinated, thus providing a plethora of potential mechanisms to regulate their activity. Here we provide an overview of how membrane proteins are selected for ubiquitination and deubiquitination within the endocytic pathway and how that ubiquitin signal is interpreted by endocytic sorting machineries.
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Affiliation(s)
- Robert C Piper
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242
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Shen Q, He B, Lu N, Conradt B, Grant BD, Zhou Z. Phagocytic receptor signaling regulates clathrin and epsin-mediated cytoskeletal remodeling during apoptotic cell engulfment in C. elegans. Development 2013; 140:3230-43. [PMID: 23861060 PMCID: PMC3931732 DOI: 10.1242/dev.093732] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The engulfment and subsequent degradation of apoptotic cells by phagocytes is an evolutionarily conserved process that efficiently removes dying cells from animal bodies during development. Here, we report that clathrin heavy chain (CHC-1), a membrane coat protein well known for its role in receptor-mediated endocytosis, and its adaptor epsin (EPN-1) play crucial roles in removing apoptotic cells in Caenorhabditis elegans. Inactivating epn-1 or chc-1 disrupts engulfment by impairing actin polymerization. This defect is partially suppressed by inactivating UNC-60, a cofilin ortholog and actin server/depolymerization protein, further indicating that EPN-1 and CHC-1 regulate actin assembly during pseudopod extension. CHC-1 is enriched on extending pseudopods together with EPN-1, in an EPN-1-dependent manner. Epistasis analysis places epn-1 and chc-1 in the same cell-corpse engulfment pathway as ced-1, ced-6 and dyn-1. CED-1 signaling is necessary for the pseudopod enrichment of EPN-1 and CHC-1. CED-1, CED-6 and DYN-1, like EPN-1 and CHC-1, are essential for the assembly and stability of F-actin underneath pseudopods. We propose that in response to CED-1 signaling, CHC-1 is recruited to the phagocytic cup through EPN-1 and acts as a scaffold protein to organize actin remodeling. Our work reveals novel roles of clathrin and epsin in apoptotic-cell internalization, suggests a Hip1/R-independent mechanism linking clathrin to actin assembly, and ties the CED-1 pathway to cytoskeleton remodeling.
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Affiliation(s)
- Qian Shen
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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22
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Sorrentino V, Nelson JK, Maspero E, Marques ARA, Scheer L, Polo S, Zelcer N. The LXR-IDOL axis defines a clathrin-, caveolae-, and dynamin-independent endocytic route for LDLR internalization and lysosomal degradation. J Lipid Res 2013; 54:2174-2184. [PMID: 23733886 DOI: 10.1194/jlr.m037713] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Low density lipoprotein (LDL) cholesterol is taken up into cells via clathrin-mediated endocytosis of the LDL receptor (LDLR). Following dissociation of the LDLR-LDL complex, LDL is directed to lysosomes whereas the LDLR recycles to the plasma membrane. Activation of the sterol-sensing nuclear receptors liver X receptors (LXRs) enhances degradation of the LDLR. This depends on the LXR target gene inducible degrader of the LDLR (IDOL), an E3-ubiquitin ligase that promotes ubiquitylation and lysosomal degradation of the LDLR. How ubiquitylation of the LDLR by IDOL controls its endocytic trafficking is currently unknown. Using genetic- and pharmacological-based approaches coupled to functional assessment of LDL uptake, we show that the LXR-IDOL axis targets a LDLR pool present in lipid rafts. IDOL-dependent internalization of the LDLR is independent of clathrin, caveolin, macroautophagy, and dynamin. Rather, it depends on the endocytic protein epsin. Consistent with LDLR ubiquitylation acting as a sorting signal, degradation of the receptor can be blocked by perturbing the endosomal sorting complex required for transport (ESCRT) or by USP8, a deubiquitylase implicated in sorting ubiquitylated cargo to multivesicular bodies. In summary, we provide evidence for the existence of an LXR-IDOL-mediated internalization pathway for the LDLR that is distinct from that used for lipoprotein uptake.
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Affiliation(s)
- Vincenzo Sorrentino
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Jessica K Nelson
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Elena Maspero
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, 20139 Milan, Italy; and
| | - André R A Marques
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Lilith Scheer
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands
| | - Simona Polo
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, 20139 Milan, Italy; and; Dipartimento di Scienze della Salute, Universita' degli Studi di Milano, 20122 Milan, Italy
| | - Noam Zelcer
- Department of Medical Biochemistry, Academic Medical Center of the University of Amsterdam, 1105AZ Amsterdam, The Netherlands.
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