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Abstract
Primary cilia, antenna-like sensory organelles protruding from the surface of most vertebrate cell types, are essential for regulating signalling pathways during development and adult homeostasis. Mutations in genes affecting cilia cause an overlapping spectrum of >30 human diseases and syndromes, the ciliopathies. Given the immense structural and functional diversity of the mammalian cilia repertoire, there is a growing disconnect between patient genotype and associated phenotypes, with variable severity and expressivity characteristic of the ciliopathies as a group. Recent technological developments are rapidly advancing our understanding of the complex mechanisms that control biogenesis and function of primary cilia across a range of cell types and are starting to tackle this diversity. Here, we examine the structural and functional diversity of primary cilia, their dynamic regulation in different cellular and developmental contexts and their disruption in disease.
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Affiliation(s)
- Pleasantine Mill
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, Scotland
| | | | - Lotte B Pedersen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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2
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Nava V, Chandra S, Aherne J, Alfonso MB, Antão-Geraldes AM, Attermeyer K, Bao R, Bartrons M, Berger SA, Biernaczyk M, Bissen R, Brookes JD, Brown D, Cañedo-Argüelles M, Canle M, Capelli C, Carballeira R, Cereijo JL, Chawchai S, Christensen ST, Christoffersen KS, de Eyto E, Delgado J, Dornan TN, Doubek JP, Dusaucy J, Erina O, Ersoy Z, Feuchtmayr H, Frezzotti ML, Galafassi S, Gateuille D, Gonçalves V, Grossart HP, Hamilton DP, Harris TD, Kangur K, Kankılıç GB, Kessler R, Kiel C, Krynak EM, Leiva-Presa À, Lepori F, Matias MG, Matsuzaki SIS, McElarney Y, Messyasz B, Mitchell M, Mlambo MC, Motitsoe SN, Nandini S, Orlandi V, Owens C, Özkundakci D, Pinnow S, Pociecha A, Raposeiro PM, Rõõm EI, Rotta F, Salmaso N, Sarma SSS, Sartirana D, Scordo F, Sibomana C, Siewert D, Stepanowska K, Tavşanoğlu ÜN, Tereshina M, Thompson J, Tolotti M, Valois A, Verburg P, Welsh B, Wesolek B, Weyhenmeyer GA, Wu N, Zawisza E, Zink L, Leoni B. Plastic debris in lakes and reservoirs. Nature 2023; 619:317-322. [PMID: 37438590 DOI: 10.1038/s41586-023-06168-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 05/04/2023] [Indexed: 07/14/2023]
Abstract
Plastic debris is thought to be widespread in freshwater ecosystems globally1. However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging2,3. Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 μm) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris4. Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services.
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Affiliation(s)
- Veronica Nava
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy.
| | - Sudeep Chandra
- Global Water Center, Department of Biology, University of Nevada, Reno, NV, USA
- Department of Biology, University of Nevada, Reno, NV, USA
| | - Julian Aherne
- School of the Environment, Trent University, Peterborough, Canada
| | - María B Alfonso
- Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan
| | - Ana M Antão-Geraldes
- Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, 5300-253 Bragança, Portugal
- Laboratório Associado para a Sustentabilidade e Tecnologia em Regiões de Montanha (SusTEC), Instituto Politécnico de Bragança, 5300-253 Bragança, Portugal
| | - Katrin Attermeyer
- WasserCluster Lunz - Biologische Station, Lunz am See, Austria
- Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
| | - Roberto Bao
- Centro Interdisciplinar de Química e Bioloxía (CICA), GRICA Group, University of A Coruña, A Coruña, Spain
| | - Mireia Bartrons
- Aquatic Ecology Group, University of Vic - Central University of Catalonia, Vic, Spain
| | - Stella A Berger
- Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
| | - Marcin Biernaczyk
- Faculty of Food Sciences and Fisheries, West Pomeranian University of Technology, Szczecin, Poland
| | - Raphael Bissen
- Department of Mining and Petroleum Engineering, Chulalongkorn University, Bangkok, Thailand
| | - Justin D Brookes
- School of Biological Sciences, University of Adelaide, North Terrace, Adelaide, Australia
| | - David Brown
- Department of Environmental Data, Horizons Regional Council, Palmerston North, New Zealand
| | - Miguel Cañedo-Argüelles
- Institute of Environmental Assessment and Water Research (IDAEA-CSIC), FEHM-Lab, Barcelona, Spain
| | - Moisés Canle
- Cátedra EMALCSA-UDC, React! Group, Faculty of Sciences & CICA, University of A Coruña, A Coruña, Spain
| | - Camilla Capelli
- Institute of Earth Sciences, University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Mendrisio, Switzerland
| | - Rafael Carballeira
- Centro Interdisciplinar de Química e Bioloxía (CICA), GRICA Group, University of A Coruña, A Coruña, Spain
- Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Valencia, Spain
| | - José Luis Cereijo
- Water and Environmental Engineering Group, University of A Coruña, A Coruña, Spain
| | | | | | | | | | - Jorge Delgado
- Water and Environmental Engineering Group, University of A Coruña, A Coruña, Spain
| | - Tyler N Dornan
- School of Biological Sciences, University of Adelaide, North Terrace, Adelaide, Australia
| | - Jonathan P Doubek
- School of Natural Resources & Environment, Lake Superior State University, Sault Sainte Marie, MI, USA
- Center for Freshwater Research and Education, Lake Superior State University, Sault Sainte Marie, MI, USA
| | - Julia Dusaucy
- Savoie Mont Blanc University, CNRS, Université Grenoble Alpes, EDYTEM, Chambéry, France
| | - Oxana Erina
- Department of Hydrology, Lomonosov Moscow State University, Moscow, Russia
- Faculty of Biotechnology and Fisheries, Moscow State University of Technologies and Management (FCU), Moscow, Russia
| | - Zeynep Ersoy
- FEHM-Lab (Freshwater Ecology, Hydrology and Management), Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Spain
- Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona (UB), Barcelona, Spain
- Rui Nabeiro Biodiversity Chair, Mediterranean Institute for Agriculture, Environment and Development (MED), Universidade de Évora, Évora, Portugal
| | - Heidrun Feuchtmayr
- Lake Ecosystems Group, UK Centre for Ecology & Hydrology, Lancaster, United Kingdom
| | - Maria Luce Frezzotti
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Silvia Galafassi
- Water Research Institute, National Research Council, Verbania, Italy
| | - David Gateuille
- Savoie Mont Blanc University, CNRS, Université Grenoble Alpes, EDYTEM, Chambéry, France
| | - Vitor Gonçalves
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, BIOPOLIS Program in Genomics, Biodiversity and Land Planning; UNESCO Chair - Land Within Sea: Biodiversity & Sustainability in Atlantic Islands, Universidade dos Açores, Ponta Delgada, São Miguel, Açores, Portugal
- Institute of Biochemistry and Biology, Potsdam University, Potsdam, Germany
| | - Hans-Peter Grossart
- Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
- Institute of Biochemistry and Biology, Potsdam University, Potsdam, Germany
| | - David P Hamilton
- Australian Rivers Institute, Griffith University, Nathan, Queensland, Australia
| | - Ted D Harris
- Kansas Biological Survey & Center for Ecological Research, University of Kansas, Lawrence, KS, USA
| | - Külli Kangur
- Estonian University of Life Sciences, Tartu, Estonia
| | | | - Rebecca Kessler
- Kansas Biological Survey & Center for Ecological Research, University of Kansas, Lawrence, KS, USA
| | - Christine Kiel
- Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
| | - Edward M Krynak
- Global Water Center, Department of Biology, University of Nevada, Reno, NV, USA
- Department of Biology, University of Nevada, Reno, NV, USA
| | - Àngels Leiva-Presa
- Aquatic Ecology Group, University of Vic - Central University of Catalonia, Vic, Spain
| | - Fabio Lepori
- Institute of Earth Sciences, University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Mendrisio, Switzerland
| | - Miguel G Matias
- Rui Nabeiro Biodiversity Chair, Mediterranean Institute for Agriculture, Environment and Development (MED), Universidade de Évora, Évora, Portugal
- Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
| | | | - Yvonne McElarney
- Fisheries and Aquatic Ecosystems, Agri-Food and Biosciences Institute, Belfast, Northern Ireland
| | - Beata Messyasz
- Department of Hydrobiology, Institute of Environmental Biology, Adam Mickiewicz University, Poznań, Poland
| | - Mark Mitchell
- Department of Science and Innovation, Horizons Regional Council, Palmerston North, New Zealand
| | - Musa C Mlambo
- Department of Freshwater Invertebrates, Albany Museum, Grahamstown, South Africa
| | - Samuel N Motitsoe
- Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa
| | - Sarma Nandini
- FES Iztacala, Universidad Nacional Autónoma de México, Tlalnepantla, Mexico
| | - Valentina Orlandi
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Caroline Owens
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, USA
| | - Deniz Özkundakci
- Environmental Research Institute - Te Pūtahi Rangahau Taiao, The University of Waikato, Hamilton, New Zealand
| | - Solvig Pinnow
- Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
| | - Agnieszka Pociecha
- Department of Freshwater Biology, Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland
| | - Pedro Miguel Raposeiro
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, BIOPOLIS Program in Genomics, Biodiversity and Land Planning; UNESCO Chair - Land Within Sea: Biodiversity & Sustainability in Atlantic Islands, Universidade dos Açores, Ponta Delgada, São Miguel, Açores, Portugal
- Faculdade de Ciências e Tecnologias, Universidade dos Açores, Ponta Delgada, Portugal
| | - Eva-Ingrid Rõõm
- Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia
| | - Federica Rotta
- Institute of Earth Sciences, University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Mendrisio, Switzerland
| | - Nico Salmaso
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - S S S Sarma
- FES Iztacala, Universidad Nacional Autónoma de México, Tlalnepantla, Mexico
| | - Davide Sartirana
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Facundo Scordo
- Instituto Argentino de Oceanografía, Universidad Nacional del Sur (UNS)-CONICET, Bahía Blanca, Argentina
- Departamento de Geografía y Turismo, Universidad Nacional del Sur, Bahía Blanca, Argentina
| | - Claver Sibomana
- Center of Research in Natural and Environmental Sciences, University of Burundi, Bujumbura, Burundi
| | | | - Katarzyna Stepanowska
- Faculty of Food Sciences and Fisheries, West Pomeranian University of Technology, Szczecin, Poland
| | | | - Maria Tereshina
- Department of Hydrology, Lomonosov Moscow State University, Moscow, Russia
| | - James Thompson
- Fisheries and Aquatic Ecosystems, Agri-Food and Biosciences Institute, Belfast, Northern Ireland
- School of Geography and Environmental Sciences, Ulster University, Coleraine, Northern Ireland
| | - Monica Tolotti
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Amanda Valois
- National Institute of Water and Atmospheric Research, Freshwater Ecology, Hamilton and Wellington, New Zealand
| | - Piet Verburg
- National Institute of Water and Atmospheric Research, Freshwater Ecology, Hamilton, New Zealand
| | - Brittany Welsh
- School of the Environment, Trent University, Peterborough, Canada
| | - Brian Wesolek
- Biological Services Department, Bay Mills Indian Community, Brimley, MI, USA
| | - Gesa A Weyhenmeyer
- Department of Ecology and Genetics, Limnology Group, Uppsala University, Uppsala, Sweden
| | - Naicheng Wu
- Department of Geography and Spatial Information Techniques, Ningbo University, Ningbo, China
| | - Edyta Zawisza
- Institute of Geological Sciences, Polish Academy of Sciences, Warsaw, Poland
| | - Lauren Zink
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada
| | - Barbara Leoni
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
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3
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Munch TN, Hedley PL, Hagen CM, Bækvad-Hansen M, Geller F, Bybjerg-Grauholm J, Nordentoft M, Børglum AD, Werge TM, Melbye M, Hougaard DM, Larsen LA, Christensen ST, Christiansen M. The genetic background of hydrocephalus in a population-based cohort: implication of ciliary involvement. Brain Commun 2023; 5:fcad004. [PMID: 36694575 PMCID: PMC9866251 DOI: 10.1093/braincomms/fcad004] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 10/04/2022] [Accepted: 01/08/2023] [Indexed: 01/11/2023] Open
Abstract
Hydrocephalus is one of the most common congenital disorders of the central nervous system and often displays psychiatric co-morbidities, in particular autism spectrum disorder. The disease mechanisms behind hydrocephalus are complex and not well understood, but some association with dysfunctional cilia in the brain ventricles and subarachnoid space has been indicated. A better understanding of the genetic aetiology of hydrocephalus, including the role of ciliopathies, may bring insights into a potentially shared genetic aetiology. In this population-based case-cohort study, we, for the first time, investigated variants of postulated hydrocephalus candidate genes. Using these data, we aimed to investigate potential involvement of the ciliome in hydrocephalus and describe genotype-phenotype associations with an autism spectrum disorder. One-hundred and twenty-one hydrocephalus candidate genes were screened in a whole-exome-sequenced sub-cohort of the Lundbeck Foundation Initiative for Integrative Psychiatric Research study, comprising 72 hydrocephalus patients and 4181 background population controls. Candidate genes containing high-impact variants of interest were systematically evaluated for their involvement in ciliary function and an autism spectrum disorder. The median age at diagnosis for the hydrocephalus patients was 0 years (range 0-27 years), the median age at analysis was 22 years (11-35 years), and 70.5% were males. The median age for controls was 18 years (range 11-26 years) and 53.3% were males. Fifty-two putative hydrocephalus-associated variants in 34 genes were identified in 42 patients (58.3%). In hydrocephalus cases, we found increased, but not significant, enrichment of high-impact protein altering variants (odds ratio 1.51, 95% confidence interval 0.92-2.51, P = 0.096), which was driven by a significant enrichment of rare protein truncating variants (odds ratio 2.71, 95% confidence interval 1.17-5.58, P = 0.011). Fourteen of the genes with high-impact variants are part of the ciliome, whereas another six genes affect cilia-dependent processes during neurogenesis. Furthermore, 15 of the 34 genes with high-impact variants and three of eight genes with protein truncating variants were associated with an autism spectrum disorder. Because symptoms of other diseases may be neglected or masked by the hydrocephalus-associated symptoms, we suggest that patients with congenital hydrocephalus undergo clinical genetic assessment with respect to ciliopathies and an autism spectrum disorder. Our results point to the significance of hydrocephalus as a ciliary disease in some cases. Future studies in brain ciliopathies may not only reveal new insights into hydrocephalus but also, brain disease in the broadest sense, given the essential role of cilia in neurodevelopment.
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Affiliation(s)
- Tina N Munch
- Correspondence to: Tina Nørgaard Munch, MD Associate Professor, Department of Neurosurgery 6031 Copenhagen University Hospital, Inge Lehmanns Vej 6 DK-2100 Copenhagen Ø, Denmark E-mail:
| | - Paula L Hedley
- Department for Congenital Disorders, Statens Serum Institut, DK-2300 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark,Brazen Bio, Los Angeles, 90502 CA, USA
| | - Christian M Hagen
- Department for Congenital Disorders, Statens Serum Institut, DK-2300 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark
| | - Marie Bækvad-Hansen
- Department for Congenital Disorders, Statens Serum Institut, DK-2300 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark
| | - Frank Geller
- Department of Epidemiology Research, Statens Serum Institut, DK-2300 Copenhagen, Denmark
| | - Jonas Bybjerg-Grauholm
- Department for Congenital Disorders, Statens Serum Institut, DK-2300 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark
| | - Merete Nordentoft
- Department of Clinical Medicine, University of Copenhagen, DK-2100 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark,Mental Health Centre, Capital Region of Denmark, 2900 Hellerup, Denmark
| | - Anders D Børglum
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark,Center for Genomics and Personalized Medicine, Aarhus University, DK-8000 Aarhus, Denmark,Department of Biomedicine, Aarhus University, DK-8000 Aarhus, Denmark
| | - Thomas M Werge
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark,Mental Health Centre, Capital Region of Denmark, 2900 Hellerup, Denmark
| | - Mads Melbye
- Department of Clinical Medicine, University of Copenhagen, DK-2100 Copenhagen, Denmark,Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA,Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo 0473, Norway,K.G. Jebsen Center for Genetic Epidemiology, Norwegian University of Science and Technology, Trondheim 7491, Norway
| | - David M Hougaard
- Department for Congenital Disorders, Statens Serum Institut, DK-2300 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark
| | - Lars A Larsen
- Department of Cellular and Molecular Medicine, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Søren T Christensen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Michael Christiansen
- Department for Congenital Disorders, Statens Serum Institut, DK-2300 Copenhagen, Denmark,The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, DK-8000 Aarhus, Denmark,Department of Biomedical Science, University of Copenhagen, DK-2100 Copenhagen, Denmark
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4
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Christensen SL, Rasmussen RH, Cour SL, Ernstsen C, Hansen TF, Kogelman LJ, Lauritzen SP, Guzaite G, Styrishave B, Janfelt C, Christensen ST, Aziz Q, Tinker A, Jansen-Olesen I, Olesen J, Kristensen DM. Smooth muscle ATP-sensitive potassium channels mediate migraine-relevant hypersensitivity in mouse models. Cephalalgia 2022; 42:93-107. [PMID: 34816764 DOI: 10.1177/03331024211053570] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BACKGROUND Opening of KATP channels by systemic levcromakalim treatment triggers attacks in migraine patients and hypersensitivity to von Frey stimulation in a mouse model. Blocking of these channels is effective in several preclinical migraine models. It is unknown in what tissue and cell type KATP-induced migraine attacks are initiated and which KATP channel subtype is targeted. METHODS In mouse models, we administered levcromakalim intracerebroventricularly, intraperitoneally and intraplantarily and compared the nociceptive responses by von Frey and hotplate tests. Mice with a conditional loss-of-function mutation in the smooth muscle KATP channel subunit Kir6.1 were given levcromakalim and GTN and examined with von Frey filaments. Arteries were tested for their ability to dilate ex vivo. mRNA expression, western blotting and immunohistochemical stainings were made to identify relevant target tissue for migraine induced by KATP channel opening. RESULTS Systemic administration of levcromakalim induced hypersensitivity but central and local administration provided antinociception respectively no effect. The Kir6.1 smooth muscle knockout mouse was protected from both GTN and levcromakalim induced hypersensitivity, and their arteries had impaired dilatory response to the latter. mRNA and protein expression studies showed that trigeminal ganglia did not have significant KATP channel expression of any subtype, whereas brain arteries and dura mater primarily expressed the Kir6.1 + SUR2B subtype. CONCLUSION Hypersensitivity provoked by GTN and levcromakalim in mice is dependent on functional smooth muscle KATP channels of extracerebral origin. These results suggest a vascular contribution to hypersensitivity induced by migraine triggers.
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Affiliation(s)
- Sarah L Christensen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Rikke H Rasmussen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Sanne La Cour
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Charlotte Ernstsen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Thomas F Hansen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
- Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Denmark
| | - Lisette Ja Kogelman
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Sabrina P Lauritzen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Gintare Guzaite
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Bjarne Styrishave
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Christian Janfelt
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Søren T Christensen
- Department of Biology, Section of Cell Biology and Physiology, University of Copenhagen, Denmark
| | - Qadeer Aziz
- The Heart Centre, 4617Queen Mary University of London, William Harvey Research Institute, Queen Mary University of London, UK
| | - Andrew Tinker
- The Heart Centre, 4617Queen Mary University of London, William Harvey Research Institute, Queen Mary University of London, UK
| | - Inger Jansen-Olesen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Jes Olesen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - David M Kristensen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail) - UMR_S 1085, Rennes, France
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
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5
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Christensen SL, Rasmussen RH, Ernstsen C, La Cour S, David A, Chaker J, Haanes KA, Christensen ST, Olesen J, Kristensen DM. CGRP-dependent signalling pathways involved in mouse models of GTN- cilostazol- and levcromakalim-induced migraine. Cephalalgia 2021; 41:1413-1426. [PMID: 34407650 DOI: 10.1177/03331024211038884] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Knowledge of exact signalling events during migraine attacks is lacking. Various substances are known to trigger migraine attacks in patients and calcitonin gene-related peptide antagonising drugs are effective against migraine pain. Here, we investigated the signalling pathways involved in three different mouse models of provoked migraine and relate them to calcitonin gene-related peptide and other migraine-relevant targets. METHODS In vivo mouse models of glyceryl trinitrate-, cilostazol- and levcromakalim-induced migraine were applied utilising tactile sensitivity to von Frey filaments as measuring readout. Signalling pathways involved in the three models were dissected by use of specific knockout mice and chemical inhibitors. In vivo results were supported by ex vivo wire myograph experiments measuring arterial dilatory responses and ex vivo calcitonin gene-related peptide release from trigeminal ganglion and trigeminal nucleus caudalis from mice. RESULTS Glyceryl trinitrate-induced hypersensitivity was dependent on both prostaglandins and transient receptor potential cation channel, subfamily A, member 1, whereas cilostazol- and levcromakalim-induced hypersensitivity were independent of both. All three migraine triggers activated calcitonin gene-related peptide signalling, as both receptor antagonism and antibody neutralisation of calcitonin gene-related peptide were effective inhibitors of hypersensitivity in all three models. Stimulation of trigeminal ganglia and brain stem tissue samples with cilostazol and levcromakalim did not result in release of calcitonin gene-related peptide, and vasodilation following levcromakalim stimulation was independent of CGRP receptor antagonism. CONCLUSION The mouse models of glyceryl trinitrate-, cilostazol- and levcromakalim- induced migraine all involve calcitonin gene-related peptide signalling in a complex interplay between different cell/tissue types. These models are useful in the study of migraine mechanisms.
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Affiliation(s)
- Sarah L Christensen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Rikke H Rasmussen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Charlotte Ernstsen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Sanne La Cour
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - Arthur David
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail) - UMR_S 1085, Rennes, France
| | - Jade Chaker
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail) - UMR_S 1085, Rennes, France
| | - Kristian A Haanes
- Department of Clinical Experimental Research, 70590Rigshospitalet Glostrup, Rigshospitalet Glostrup, Denmark
| | - Søren T Christensen
- Department of Biology, Section of Cell Biology and Physiology, University of Copenhagen, Denmark
| | - Jes Olesen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark
| | - David M Kristensen
- Danish Headache Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark.,Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail) - UMR_S 1085, Rennes, France.,Department of Biology, Section of Cell Biology and Physiology, University of Copenhagen, Denmark
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6
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Álvarez-Satta M, Lago-Docampo M, Bea-Mascato B, Solarat C, Castro-Sánchez S, Christensen ST, Valverde D. ALMS1 Regulates TGF-β Signaling and Morphology of Primary Cilia. Front Cell Dev Biol 2021; 9:623829. [PMID: 33598462 PMCID: PMC7882606 DOI: 10.3389/fcell.2021.623829] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 01/11/2021] [Indexed: 12/20/2022] Open
Abstract
In this study, we aimed to evaluate the role of ALMS1 in the morphology of primary cilia and regulation of cellular signaling using a knockdown model of the hTERT-RPE1 cell line. ALMS1 depletion resulted in the formation of longer cilia, which often displayed altered morphology as evidenced by extensive twisting and bending of the axoneme. Transforming growth factor beta/bone morphogenetic protein (TGF-β/BMP) signaling, which is regulated by primary cilia, was similarly affected by ALMS1 depletion as judged by reduced levels of TGFβ-1-mediated activation of SMAD2/3. These results provide novel information on the role of ALMS1 in the function of primary cilia and processing of cellular signaling, which when aberrantly regulated may underlie Alström syndrome.
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Affiliation(s)
- María Álvarez-Satta
- CINBIO, Universidade de Vigo, Vigo, Spain.,Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), Hospital Álvaro Cunqueiro, Vigo, Spain
| | - Mauro Lago-Docampo
- CINBIO, Universidade de Vigo, Vigo, Spain.,Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), Hospital Álvaro Cunqueiro, Vigo, Spain
| | - Brais Bea-Mascato
- CINBIO, Universidade de Vigo, Vigo, Spain.,Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), Hospital Álvaro Cunqueiro, Vigo, Spain
| | - Carlos Solarat
- CINBIO, Universidade de Vigo, Vigo, Spain.,Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), Hospital Álvaro Cunqueiro, Vigo, Spain
| | - Sheila Castro-Sánchez
- CINBIO, Universidade de Vigo, Vigo, Spain.,Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), Hospital Álvaro Cunqueiro, Vigo, Spain
| | - Søren T Christensen
- Department of Biology, Section of Cell Biology and Physiology, The August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Diana Valverde
- CINBIO, Universidade de Vigo, Vigo, Spain.,Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), Hospital Álvaro Cunqueiro, Vigo, Spain
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7
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Björkman A, Johansen SL, Lin L, Schertzer M, Kanellis DC, Katsori AM, Christensen ST, Luo Y, Andersen JS, Elsässer SJ, Londono-Vallejo A, Bartek J, Schou KB. Human RTEL1 associates with Poldip3 to facilitate responses to replication stress and R-loop resolution. Genes Dev 2020; 34:1065-1074. [PMID: 32561545 PMCID: PMC7397856 DOI: 10.1101/gad.330050.119] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 05/18/2020] [Indexed: 02/07/2023]
Abstract
In this study from Björkman et al., the authors sought to understand how RTEL1 helicase preserves genomic stability during replication. They demonstrate that RTEL1 and the Polδ subunit Poldip3 form a complex and are mutually dependent in chromatin binding after replication stress, and loss of RTEL1 and Poldip3 leads to marked R-loop accumulation that is confined to sites of active replication, thus highlighting a previously unknown role of RTEL1 and Poldip3 in R-loop suppression at genomic regions where transcription and replication intersect. RTEL1 helicase is a component of DNA repair and telomere maintenance machineries. While RTEL1's role in DNA replication is emerging, how RTEL1 preserves genomic stability during replication remains elusive. Here we used a range of proteomic, biochemical, cell, and molecular biology and gene editing approaches to provide further insights into potential role(s) of RTEL1 in DNA replication and genome integrity maintenance. Our results from complementary human cell culture models established that RTEL1 and the Polδ subunit Poldip3 form a complex and are/function mutually dependent in chromatin binding after replication stress. Loss of RTEL1 and Poldip3 leads to marked R-loop accumulation that is confined to sites of active replication, enhances endogenous replication stress, and fuels ensuing genomic instability. The impact of depleting RTEL1 and Poldip3 is epistatic, consistent with our proposed concept of these two proteins operating in a shared pathway involved in DNA replication control under stress conditions. Overall, our data highlight a previously unsuspected role of RTEL1 and Poldip3 in R-loop suppression at genomic regions where transcription and replication intersect, with implications for human diseases including cancer.
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Affiliation(s)
- Andrea Björkman
- Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, Solna 171 77, Sweden
| | - Søren L Johansen
- Department of Cell Biology and Physiology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Lin Lin
- Department of Biomedicine, Aarhus University, Aarhus 8200, Denmark.,Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus 8200, Denmark
| | - Mike Schertzer
- 3UMR 3244 (Telomere and Cancer Laboratory), Centre National de la Recherche Scientifique, Institut Curie, PSL Research University, Sorbonne Universités, Paris 75005, France
| | - Dimitris C Kanellis
- Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, Solna 171 77, Sweden
| | - Anna-Maria Katsori
- Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, Solna 171 77, Sweden
| | - Søren T Christensen
- Department of Cell Biology and Physiology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Yonglun Luo
- Department of Biomedicine, Aarhus University, Aarhus 8200, Denmark.,Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus 8200, Denmark
| | - Jens S Andersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Simon J Elsässer
- Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, Solna 171 77, Sweden
| | - Arturo Londono-Vallejo
- 3UMR 3244 (Telomere and Cancer Laboratory), Centre National de la Recherche Scientifique, Institut Curie, PSL Research University, Sorbonne Universités, Paris 75005, France
| | - Jiri Bartek
- Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, Solna 171 77, Sweden.,Danish Cancer Society Research Centre, DK-2100 Copenhagen, Denmark
| | - Kenneth B Schou
- Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, Solna 171 77, Sweden
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8
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Malinda RR, Zeeberg K, Sharku PC, Ludwig MQ, Pedersen LB, Christensen ST, Pedersen SF. TGFβ Signaling Increases Net Acid Extrusion, Proliferation and Invasion in Panc-1 Pancreatic Cancer Cells: SMAD4 Dependence and Link to Merlin/NF2 Signaling. Front Oncol 2020; 10:687. [PMID: 32457840 PMCID: PMC7221161 DOI: 10.3389/fonc.2020.00687] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 04/14/2020] [Indexed: 12/14/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer-related death, with a 5-year survival of <10% and severely limited treatment options. PDAC hallmarks include profound metabolic acid production and aggressive local proliferation and invasiveness. This phenotype is supported by upregulated net acid extrusion and epithelial-to-mesenchymal transition (EMT), the latter typically induced by aberrant transforming growth factor-β (TGFβ) signaling. It is, however, unknown whether TGFβ-induced EMT and upregulation of acid extrusion are causally related. Here, we show that mRNA and protein expression of the net acid extruding transporters Na+/H+ exchanger 1 (NHE1, SLC9A1) and Na+, HCO3- cotransporter 1 (NBCn1, SLC4A7) are increased in a panel of human PDAC cell lines compared to immortalized human pancreatic ductal epithelial (HPDE) cells. Treatment of Panc-1 cells (which express SMAD4, required for canonical TGFβ signaling) with TGFβ-1 for 48 h elicited classical EMT with down- and upregulation of epithelial and mesenchymal markers, respectively, in a manner inhibited by SMAD4 knockdown. Accordingly, less pronounced EMT was induced in BxPC-3 cells, which do not express SMAD4. TGFβ-1 treatment elicited a SMAD4-dependent increase in NHE1 expression, and a smaller, SMAD4-independent increase in NBCn1 in Panc-1 cells. Consistent with this, TGFβ-1 treatment led to elevated intracellular pH and increased net acid extrusion capacity in Panc-1 cells, but not in BxPC-3 cells, in an NHE1-dependent manner. Proliferation was increased in Panc-1 cells and decreased in BxPC-3 cells, upon TGFβ-1 treatment, and this, as well as EMT per se, was unaffected by NHE1- or NBCn1 inhibition. TGFβ-1-induced EMT was associated with a 4-fold increase in Panc-1 cell invasiveness, which further increased ~10-fold upon knockdown of the tumor suppressor Merlin (Neurofibromatosis type 2). Knockdown of NHE1 or NBCn1 abolished Merlin-induced invasiveness, but not that induced by TGFβ-1 alone. In conclusion, NHE1 and NBCn1 expression and NHE-dependent acid extrusion are upregulated during TGFβ-1-induced EMT of Panc-1 cells. NHE1 upregulation is SMAD4-dependent, and SMAD4-deficient BxPC-3 cells show no change in pHi regulation. NHE1 and NBCn1 are not required for EMT per se or EMT-associated proliferation changes, but are essential for the potentiation of invasiveness induced by Merlin knockdown.
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Affiliation(s)
- Raj R Malinda
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Katrine Zeeberg
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Patricia C Sharku
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Mette Q Ludwig
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Lotte B Pedersen
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Søren T Christensen
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Stine F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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9
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Stevens EM, Vladar EK, Alanin MC, Christensen ST, von Buchwald C, Milla C. Ciliary Localization of the Intraflagellar Transport Protein IFT88 Is Disrupted in Cystic Fibrosis. Am J Respir Cell Mol Biol 2020; 62:120-123. [DOI: 10.1165/rcmb.2018-0287le] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Elizabeth M. Stevens
- University of CopenhagenCopenhagen, Denmark
- Stanford UniversityStanford, Californiaand
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10
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Christensen ST, Grell AS, Johansson SE, Andersson CM, Edvinsson L, Haanes KA. Synergistic effects of a cremophor EL drug delivery system and its U0126 cargo in an ex vivo model. Drug Deliv 2019; 26:680-688. [PMID: 31274009 PMCID: PMC6691891 DOI: 10.1080/10717544.2019.1636421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Neuroprotection has proven clinically unsuccessful in subarachnoid hemorrhage. We believe that this is because the major component in the early damage pathway, the vascular wall, has not been given the necessary focus. U0126 is a potent inhibitor of vascular phenotypical changes, exemplified by functional endothelin B (ETB) receptor upregulation. The current study aimed to determine the optimal dose of U0126 ex vivo and test the toxicology of this dose in vivo. To find the optimal dose and test a suitable in vivo delivery system, we applied an ex vivo model of blood flow cessation and investigated functional ETB receptor upregulation (using a specific agonist) as the primary endpoint. The secondary endpoint was depolarization-induced contractility assessed by 60 mM K+ stimuli. Furthermore, an in vivo toxicology study was performed on the optimal selected doses. U0126 (10 µM) had a strong effect on the prevention of functional ETB receptor contractility, combined with minimal effect on the depolarization-induced contractility. When cremophor EL was chosen for drug delivery, it had an inhibitory and additive effect (combined with U0126) on the ETB receptor contractility. Hence, 10 µM U0126 in 0.5% cremophor EL seems to be a dose that will be close to the maximal inhibition observed ex vivo on basilar arteries, without exhibiting side effects in the toxicology studies. U0126 and cremophor EL are well tolerated at doses that have effect on ETB receptor upregulation. Cremophor EL has an additional positive effect, preventing functional ETB receptor upregulation, making it suitable as a drug delivery system.
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Affiliation(s)
- S T Christensen
- a Department of Clinical Experimental Research , Copenhagen University Hospital, Rigshospitalet-Glostrup , Copenhagen , Denmark
| | - A S Grell
- a Department of Clinical Experimental Research , Copenhagen University Hospital, Rigshospitalet-Glostrup , Copenhagen , Denmark
| | - S E Johansson
- a Department of Clinical Experimental Research , Copenhagen University Hospital, Rigshospitalet-Glostrup , Copenhagen , Denmark
| | | | - L Edvinsson
- a Department of Clinical Experimental Research , Copenhagen University Hospital, Rigshospitalet-Glostrup , Copenhagen , Denmark.,c Department of Clinical Sciences, Division of Experimental Vascular Research , Lund University , Lund , Sweden
| | - K A Haanes
- a Department of Clinical Experimental Research , Copenhagen University Hospital, Rigshospitalet-Glostrup , Copenhagen , Denmark
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11
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Mönnich M, Borgeskov L, Breslin L, Jakobsen L, Rogowski M, Doganli C, Schrøder JM, Mogensen JB, Blinkenkjær L, Harder LM, Lundberg E, Geimer S, Christensen ST, Andersen JS, Larsen LA, Pedersen LB. CEP128 Localizes to the Subdistal Appendages of the Mother Centriole and Regulates TGF-β/BMP Signaling at the Primary Cilium. Cell Rep 2019. [PMID: 29514088 DOI: 10.1016/j.celrep.2018.02.043] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Abstract
The centrosome is the main microtubule-organizing center in animal cells and comprises a mother and daughter centriole surrounded by pericentriolar material. During formation of primary cilia, the mother centriole transforms into a basal body that templates the ciliary axoneme. Ciliogenesis depends on mother centriole-specific distal appendages, whereas the role of subdistal appendages in ciliary function is unclear. Here, we identify CEP128 as a centriole subdistal appendage protein required for regulating ciliary signaling. Loss of CEP128 did not grossly affect centrosomal or ciliary structure but caused impaired transforming growth factor-β/bone morphogenetic protein (TGF-β/BMP) signaling in zebrafish and at the primary cilium in cultured mammalian cells. This phenotype is likely the result of defective vesicle trafficking at the cilium as ciliary localization of RAB11 was impaired upon loss of CEP128, and quantitative phosphoproteomics revealed that CEP128 loss affects TGF-β1-induced phosphorylation of multiple proteins that regulate cilium-associated vesicle trafficking.
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Affiliation(s)
- Maren Mönnich
- Department of Cellular and Molecular Medicine, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Louise Borgeskov
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Loretta Breslin
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark; Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Lis Jakobsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Michaela Rogowski
- Cell Biology/Electron Microscopy, University of Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth, Germany
| | - Canan Doganli
- Department of Cellular and Molecular Medicine, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Jacob M Schrøder
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Johanne B Mogensen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Louise Blinkenkjær
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Lea M Harder
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Emma Lundberg
- Science for Life Laboratory, School of Biotechnology, KTH Royal Institute of Technology, SE-171 21 Stockholm, Sweden
| | - Stefan Geimer
- Cell Biology/Electron Microscopy, University of Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth, Germany.
| | - Søren T Christensen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark.
| | - Jens S Andersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
| | - Lars A Larsen
- Department of Cellular and Molecular Medicine, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Lotte B Pedersen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark.
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12
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Lam RK, Raj SL, Pascal TA, Pemmaraju CD, Foglia L, Simoncig A, Fabris N, Miotti P, Hull CJ, Rizzuto AM, Smith JW, Mincigrucci R, Masciovecchio C, Gessini A, Allaria E, De Ninno G, Diviacco B, Roussel E, Spampinati S, Penco G, Di Mitri S, Trovò M, Danailov M, Christensen ST, Sokaras D, Weng TC, Coreno M, Poletto L, Drisdell WS, Prendergast D, Giannessi L, Principi E, Nordlund D, Saykally RJ, Schwartz CP. Soft X-Ray Second Harmonic Generation as an Interfacial Probe. Phys Rev Lett 2018; 120:023901. [PMID: 29376703 DOI: 10.1103/physrevlett.120.023901] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Indexed: 05/27/2023]
Abstract
Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (∼284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from the first atomic layer at the open surface. This technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.
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Affiliation(s)
- R K Lam
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S L Raj
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - T A Pascal
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - C D Pemmaraju
- Theory Institute for Materials and Energy Spectroscopies, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - L Foglia
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - A Simoncig
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - N Fabris
- Institute of Photonics and Nanotechnologies, National Research Council of Italy, via Trasea 7, I-35131 Padova, Italy
- Department of Information Engineering, University of Padova, via Gradenigo 6/B, I-35131 Padova, Italy
| | - P Miotti
- Institute of Photonics and Nanotechnologies, National Research Council of Italy, via Trasea 7, I-35131 Padova, Italy
- Department of Information Engineering, University of Padova, via Gradenigo 6/B, I-35131 Padova, Italy
| | - C J Hull
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A M Rizzuto
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - J W Smith
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - R Mincigrucci
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - C Masciovecchio
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - A Gessini
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - E Allaria
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - G De Ninno
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
- Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia
| | - B Diviacco
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - E Roussel
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - S Spampinati
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - G Penco
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - S Di Mitri
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - M Trovò
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - M Danailov
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - S T Christensen
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - D Sokaras
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - T-C Weng
- Center for High Pressure Science & Technology Advanced Research, Pudong, Shanghai 201203, China
| | - M Coreno
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
- ISM-CNR, Elettra Laboratory, Basovizza, I-34149 Trieste, Italy
| | - L Poletto
- Institute of Photonics and Nanotechnologies, National Research Council of Italy, via Trasea 7, I-35131 Padova, Italy
| | - W S Drisdell
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - D Prendergast
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - L Giannessi
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
- ENEA, C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Rome), Italy
| | - E Principi
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5, 34149 Trieste, Italy
| | - D Nordlund
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - R J Saykally
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - C P Schwartz
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
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13
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Christensen ST, Morthorst SK, Mogensen JB, Pedersen LB. Primary Cilia and Coordination of Receptor Tyrosine Kinase (RTK) and Transforming Growth Factor β (TGF-β) Signaling. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a028167. [PMID: 27638178 DOI: 10.1101/cshperspect.a028167] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Since the beginning of the millennium, research in primary cilia has revolutionized our way of understanding how cells integrate and organize diverse signaling pathways during vertebrate development and in tissue homeostasis. Primary cilia are unique sensory organelles that detect changes in their extracellular environment and integrate and transmit signaling information to the cell to regulate various cellular, developmental, and physiological processes. Many different signaling pathways have now been shown to rely on primary cilia to function properly, and mutations that lead to ciliary dysfunction are at the root of a pleiotropic group of diseases and syndromic disorders called ciliopathies. In this review, we present an overview of primary cilia-mediated regulation of receptor tyrosine kinase (RTK) and transforming growth factor β (TGF-β) signaling. Further, we discuss how defects in the coordination of these pathways may be linked to ciliopathies.
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Affiliation(s)
- Søren T Christensen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen OE, Denmark
| | - Stine K Morthorst
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen OE, Denmark
| | - Johanne B Mogensen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen OE, Denmark
| | - Lotte B Pedersen
- Department of Biology, University of Copenhagen, DK-2100 Copenhagen OE, Denmark
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14
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Pedersen LB, Mogensen JB, Christensen ST. Endocytic Control of Cellular Signaling at the Primary Cilium. Trends Biochem Sci 2016; 41:784-797. [DOI: 10.1016/j.tibs.2016.06.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 06/03/2016] [Accepted: 06/07/2016] [Indexed: 01/20/2023]
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15
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Mourão A, Christensen ST, Lorentzen E. The intraflagellar transport machinery in ciliary signaling. Curr Opin Struct Biol 2016; 41:98-108. [PMID: 27393972 DOI: 10.1016/j.sbi.2016.06.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 06/07/2016] [Indexed: 01/12/2023]
Abstract
Cilia and flagella on eukaryotic cells are slender microtubule-based projections surrounded by a membrane with a unique lipid and protein composition. It is now appreciated that cilia in addition to their established roles in motility also constitute hubs for cellular signaling by sensing external environmental cues necessary for organ development and maintenance of human health. Pathways reported to rely on the cilium organelle include Hedgehog, TGF-β, Wnt, PDGFRα, integrin and DNA damage repair signaling. An emerging theme in ciliary signaling is the requirement for active transport of signaling components into and out of the cilium proper. Here, we review the current state-of-the-art regarding the importance of intraflagellar transport and BBSome multi-subunit complexes in ciliary signaling.
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Affiliation(s)
- André Mourão
- Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany
| | - Søren T Christensen
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark.
| | - Esben Lorentzen
- Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
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Nielsen BS, Malinda RR, Schmid FM, Pedersen SF, Christensen ST, Pedersen LB. PDGFRβ and oncogenic mutant PDGFRα D842V promote disassembly of primary cilia through a PLCγ- and AURKA-dependent mechanism. J Cell Sci 2015; 128:3543-9. [PMID: 26290382 DOI: 10.1242/jcs.173559] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 08/17/2015] [Indexed: 01/04/2023] Open
Abstract
Primary cilia are microtubule-based sensory organelles projecting from most quiescent mammalian cells, which disassemble in cells cultured in serum-deprived conditions upon re-addition of serum or growth factors. Platelet-derived growth factors (PDGF) are implicated in deciliation, but the specific receptor isoforms and mechanisms involved are unclear. We report that PDGFRβ promotes deciliation in cultured cells and provide evidence implicating PLCγ and intracellular Ca(2+) release in this process. Activation of wild-type PDGFRα alone did not elicit deciliation. However, expression of constitutively active PDGFRα D842V mutant receptor, which potently activates PLCγ (also known as PLCG1), caused significant deciliation, and this phenotype was rescued by inhibiting PDGFRα D842V kinase activity or AURKA. We propose that PDGFRβ and PDGFRα D842V promote deciliation through PLCγ-mediated Ca(2+) release from intracellular stores, causing activation of calmodulin and AURKA-triggered deciliation.
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Affiliation(s)
- Brian S Nielsen
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen OE DK-2100, Denmark
| | - Raj R Malinda
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen OE DK-2100, Denmark
| | - Fabian M Schmid
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen OE DK-2100, Denmark
| | - Stine F Pedersen
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen OE DK-2100, Denmark
| | - Søren T Christensen
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen OE DK-2100, Denmark
| | - Lotte B Pedersen
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen OE DK-2100, Denmark
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17
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Schou KB, Morthorst SK, Christensen ST, Pedersen LB. Identification of conserved, centrosome-targeting ASH domains in TRAPPII complex subunits and TRAPPC8. Cilia 2014; 3:6. [PMID: 25018876 PMCID: PMC4094338 DOI: 10.1186/2046-2530-3-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 05/22/2014] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Assembly of primary cilia relies on vesicular trafficking towards the cilium base and intraflagellar transport (IFT) between the base and distal tip of the cilium. Recent studies have identified several key regulators of these processes, including Rab GTPases such as Rab8 and Rab11, the Rab8 guanine nucleotide exchange factor Rabin8, and the transport protein particle (TRAPP) components TRAPPC3, -C9, and -C10, which physically interact with each other and function together with Bardet Biedl syndrome (BBS) proteins in ciliary membrane biogenesis. However, despite recent advances, the exact molecular mechanisms by which these proteins interact and target to the basal body to promote ciliogenesis are not fully understood. RESULTS We surveyed the human proteome for novel ASPM, SPD-2, Hydin (ASH) domain-containing proteins. We identified the TRAPP complex subunits TRAPPC8, -9, -10, -11, and -13 as novel ASH domain-containing proteins. In addition to a C-terminal ASH domain region, we predict that the N-terminus of TRAPPC8, -9, -10, and -11, as well as their yeast counterparts, consists of an α-solenoid bearing stretches of multiple tetratricopeptide (TPR) repeats. Immunofluorescence microscopy analysis of cultured mammalian cells revealed that exogenously expressed ASH domains, as well as endogenous TRAPPC8, localize to the centrosome/basal body. Further, depletion of TRAPPC8 impaired ciliogenesis and GFP-Rabin8 centrosome targeting. CONCLUSIONS Our results suggest that ASH domains confer targeting to the centrosome and cilia, and that TRAPPC8 has cilia-related functions. Further, we propose that the yeast TRAPPII complex and its mammalian counterpart are evolutionarily related to the bacterial periplasmic trafficking chaperone PapD of the usher pili assembly machinery.
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Affiliation(s)
- Kenneth B Schou
- Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark ; Center for Experimental Bioinformatics, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Stine K Morthorst
- Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark
| | - Søren T Christensen
- Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark
| | - Lotte B Pedersen
- Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark
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18
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Abstract
Cilia and flagella are surface-exposed, finger-like organelles whose core consists of a microtubule (MT)-based axoneme that grows from a modified centriole, the basal body. Cilia are found on the surface of many eukaryotic cells and play important roles in cell motility and in coordinating a variety of signaling pathways during growth, development, and tissue homeostasis. Defective cilia have been linked to a number of developmental disorders and diseases, collectively called ciliopathies. Cilia are dynamic organelles that assemble and disassemble in tight coordination with the cell cycle. In most cells, cilia are assembled during growth arrest in a multistep process involving interaction of vesicles with appendages present on the distal end of mature centrioles, and addition of tubulin and other building blocks to the distal tip of the basal body and growing axoneme; these building blocks are sorted through a region at the cilium base known as the ciliary necklace, and then transported via intraflagellar transport (IFT) along the axoneme toward the tip for assembly. After assembly, the cilium frequently continues to turn over and incorporate tubulin at its distal end in an IFT-dependent manner. Prior to cell division, the cilia are usually resorbed to liberate centrosomes for mitotic spindle pole formation. Here, we present an overview of the main cytoskeletal structures associated with cilia and centrioles with emphasis on the MT-associated appendages, fibers, and filaments at the cilium base and tip. The composition and possible functions of these structures are discussed in relation to cilia assembly, disassembly, and length regulation.
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Affiliation(s)
- Lotte B Pedersen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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19
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Veland IR, Montjean R, Eley L, Pedersen LB, Schwab A, Goodship J, Kristiansen K, Pedersen SF, Saunier S, Christensen ST. Inversin/Nephrocystin-2 is required for fibroblast polarity and directional cell migration. PLoS One 2013; 8:e60193. [PMID: 23593172 PMCID: PMC3620528 DOI: 10.1371/journal.pone.0060193] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 02/22/2013] [Indexed: 12/30/2022] Open
Abstract
Inversin is a ciliary protein that critically regulates developmental processes and tissue homeostasis in vertebrates, partly through the degradation of Dishevelled (Dvl) proteins to coordinate Wnt signaling in planar cell polarity (PCP). Here, we investigated the role of Inversin in coordinating cell migration, which highly depends on polarity processes at the single-cell level, including the spatial and temporal organization of the cytoskeleton as well as expression and cellular localization of proteins in leading edge formation of migrating cells. Using cultures of mouse embryonic fibroblasts (MEFs) derived from inv(-/-) and inv(+/+) animals, we confirmed that both inv(-/-) and inv(+/+) MEFs form primary cilia, and that Inversin localizes to the primary cilium in inv(+/+) MEFs. In wound healing assays, inv(-/-) MEFs were severely compromised in their migratory ability and exhibited cytoskeletal rearrangements, including distorted lamellipodia formation and cilia orientation. Transcriptome analysis revealed dysregulation of Wnt signaling and of pathways regulating actin organization and focal adhesions in inv(-/-) MEFs as compared to inv(+/+) MEFs. Further, Dvl-1 and Dvl-3 localized to MEF primary cilia, and β-catenin/Wnt signaling was elevated in inv(-/-) MEFs, which moreover showed reduced ciliary localization of Dvl-3. Finally, inv(-/-) MEFs displayed dramatically altered activity and localization of RhoA, Rac1, and Cdc42 GTPases, and aberrant expression and targeting of the Na(+)/H(+) exchanger NHE1 and ezrin/radixin/moesin (ERM) proteins to the edge of cells facing the wound. Phosphorylation of β-catenin at the ciliary base and formation of well-defined lamellipodia with localization and activation of ERM to the leading edge of migrating cells were restored in inv(-/-) MEFs expressing Inv-GFP. Collectively, our findings point to the significance of Inversin in controlling cell migration processes, at least in part through transcriptional regulation of genes involved in Wnt signaling and pathways that control cytoskeletal organization and ion transport.
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Affiliation(s)
- Iben R. Veland
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Rodrick Montjean
- Inserm U-983, Imagine Institut, Paris Descartes-Sorbonne Paris Cité University, Necker Hospital, Paris, France
| | - Lorraine Eley
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Lotte B. Pedersen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Albrecht Schwab
- Institute of Physiology II, Münster University, Münster, Germany
| | - Judith Goodship
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | | | - Stine F. Pedersen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Sophie Saunier
- Inserm U-983, Imagine Institut, Paris Descartes-Sorbonne Paris Cité University, Necker Hospital, Paris, France
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20
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Clement DL, Mally S, Stock C, Lethan M, Satir P, Schwab A, Pedersen SF, Christensen ST. PDGFRα signaling in the primary cilium regulates NHE1-dependent fibroblast migration via coordinated differential activity of MEK1/2-ERK1/2-p90RSK and AKT signaling pathways. J Cell Sci 2012; 126:953-65. [PMID: 23264740 DOI: 10.1242/jcs.116426] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In fibroblasts, platelet-derived growth factor receptor alpha (PDGFRα) is upregulated during growth arrest and compartmentalized to the primary cilium. PDGF-AA mediated activation of the dimerized ciliary receptor produces a phosphorylation cascade through the PI3K-AKT and MEK1/2-ERK1/2 pathways leading to the activation of the Na(+)/H(+) exchanger, NHE1, cytoplasmic alkalinization and actin nucleation at the lamellipodium that supports directional cell migration. We here show that AKT and MEK1/2-ERK1/2-p90(RSK) inhibition reduced PDGF-AA-induced cell migration by distinct mechanisms: AKT inhibition reduced NHE1 activity by blocking the translocation of NHE1 to the cell membrane. MEK1/2 inhibition did not affect NHE1 activity but influenced NHE1 localization, causing NHE1 to localize discontinuously in patches along the plasma membrane, rather than preferentially at the lamellipodium. We also provide direct evidence of NHE1 translocation through the cytoplasm to the leading edge. In conclusion, signals initiated at the primary cilium through the PDGFRαα cascade reorganize the cytoskeleton to regulate cell migration differentially through the AKT and the MEK1/2-ERK1/2-p90(RSK) pathways. The AKT pathway is necessary for initiation of NHE1 translocation, presumably in vesicles, to the leading edge and for its activation. In contrast, the MEK1/2-ERK1/2-p90(RSK) pathway controls the spatial organization of NHE1 translocation and incorporation, and therefore specifies the direction of the leading edge formation.
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Affiliation(s)
- Ditte L Clement
- Department of Biology, University of Copenhagen, August Krogh Building, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark
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Pedersen LB, Dinant RI, Aleliunaite A, Veland IR, Christensen ST. The primary cilium regulates the expression and subcellular localization of kinesin-3 family member Kif13B. Cilia 2012. [PMCID: PMC3555922 DOI: 10.1186/2046-2530-1-s1-p37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Egeberg DL, Lethan M, Manguso R, Schneider L, Awan A, Jørgensen TS, Byskov AG, Pedersen LB, Christensen ST. Primary cilia and aberrant cell signaling in epithelial ovarian cancer. Cilia 2012; 1:15. [PMID: 23351307 PMCID: PMC3555760 DOI: 10.1186/2046-2530-1-15] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 05/01/2012] [Indexed: 12/14/2022] Open
Abstract
Background Ovarian cancer is the fourth leading cause of cancer-related deaths among women in Denmark, largely due to the advanced stage at diagnosis in most patients. Approximately 90% of ovarian cancers originate from the single-layered ovarian surface epithelium (OSE). Defects in the primary cilium, a solitary sensory organelle in most cells types including OSE, were recently implicated in tumorigenesis, mainly due to deregulation of ciliary signaling pathways such as Hedgehog (Hh) signaling. However, a possible link between primary cilia and epithelial ovarian cancer has not previously been investigated. Methods The presence of primary cilia was analyzed in sections of fixed human ovarian tissue as well as in cultures of normal human ovarian surface epithelium (OSE) cells and two human OSE-derived cancer cell lines. We also used immunofluorescence microscopy, western blotting, RT-PCR and siRNA to investigate ciliary signaling pathways in these cells. Results We show that ovarian cancer cells display significantly reduced numbers of primary cilia. The reduction in ciliation frequency in these cells was not due to a failure to enter growth arrest, and correlated with persistent centrosomal localization of aurora A kinase (AURA). Further, we demonstrate that ovarian cancer cells have deregulated Hh signaling and platelet-derived growth factor receptor alpha (PDGFRα) expression and that promotion of ciliary formation/stability by AURA siRNA depletion decreases Hh signaling in ovarian cancer cells. Lastly, we show that the tumor suppressor protein and negative regulator of AURA, checkpoint with forkhead-associated and ring finger domains (CHFR), localizes to the centrosome/primary cilium axis. Conclusions Our results suggest that primary cilia play a role in maintaining OSE homeostasis and that the low frequency of primary cilia in cancer OSE cells may result in part from over-expression of AURA, leading to aberrant Hh signaling and ovarian tumorigenesis.
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Affiliation(s)
- Dorte L Egeberg
- Department of Biology, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark.
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23
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Christensen ST, Clement CA, Satir P, Pedersen LB. Primary cilia and coordination of receptor tyrosine kinase (RTK) signalling. J Pathol 2012; 226:172-84. [PMID: 21956154 PMCID: PMC4294548 DOI: 10.1002/path.3004] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 09/20/2011] [Accepted: 09/22/2011] [Indexed: 12/14/2022]
Abstract
Primary cilia are microtubule-based sensory organelles that coordinate signalling pathways in cell-cycle control, migration, differentiation and other cellular processes critical during development and for tissue homeostasis. Accordingly, defects in assembly or function of primary cilia lead to a plethora of developmental disorders and pathological conditions now known as ciliopathies. In this review, we summarize the current status of the role of primary cilia in coordinating receptor tyrosine kinase (RTK) signalling pathways. Further, we present potential mechanisms of signalling crosstalk and networking in the primary cilium and discuss how defects in ciliary RTK signalling are linked to human diseases and disorders.
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Schrøder JM, Larsen J, Komarova Y, Akhmanova A, Thorsteinsson RI, Grigoriev I, Manguso R, Christensen ST, Pedersen SF, Geimer S, Pedersen LB. EB1 and EB3 promote cilia biogenesis by several centrosome-related mechanisms. J Cell Sci 2011; 124:2539-51. [PMID: 21768326 DOI: 10.1242/jcs.085852] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The microtubule (MT) plus-end-tracking protein EB1 is required for assembly of primary cilia in mouse fibroblasts, but the mechanisms involved and the roles of the related proteins EB2 and EB3 in ciliogenesis are unknown. Using protein depletion experiments and expression of dominant-negative constructs we show here that EB1 and EB3, but not EB2, are required for assembly of primary cilia in cultured cells. Electron microscopy and live imaging showed that cells lacking EB1 or EB3 are defective in MT minus-end anchoring at the centrosome and/or basal body, and possess abnormally short cilia stumps surrounded by vesicles. Further, GST pull-down assays, mass spectrometry and immunoprecipitation indicated that EB1 and EB3 interact with proteins implicated in MT minus-end anchoring or vesicular trafficking to the cilia base, suggesting that EB1 and EB3 promote ciliogenesis by facilitating such trafficking. In addition, we show that EB3 is localized to the tip of motile cilia in bronchial epithelial cells and affects the formation of centriole-associated rootlet filaments. Collectively, our findings indicate that EBs affect biogenesis of cilia by several centrosome-related mechanisms and support the idea that different EB1-EB3 dimer species have distinct functions within cells.
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Affiliation(s)
- Jacob M Schrøder
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark
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25
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Madsen SH, Andreassen KV, Christensen ST, Karsdal MA, Sverdrup FM, Bay-Jensen AC, Henriksen K. Glucocorticoids exert context-dependent effects on cells of the joint in vitro. Steroids 2011; 76:1474-82. [PMID: 21855558 DOI: 10.1016/j.steroids.2011.07.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 07/27/2011] [Accepted: 07/28/2011] [Indexed: 01/20/2023]
Abstract
INTRODUCTION Glucocorticoids are known to attenuate bone formation in vivo leading to decreased bone volume and increased risk of fractures, whereas effects on the joint tissue are less characterized. However, glucocorticoids appear to have a reducing effect on inflammation and pain in osteoarthritis. This study aimed at characterizing the effect of glucocorticoids on chondrocytes, osteoclasts, and osteoblasts. EXPERIMENTAL We used four model systems to investigate how glucocorticoids affect the cells of the joint; two intact tissues (femoral head- and cartilage-explants), and two separate cell cultures of osteoblasts (2T3-pre-osteoblasts) and osteoclasts (CD14(+)-monocytes). The model systems were cultured in the presence of two glucocorticoids; prednisolone or dexamethasone. To induce anabolic and catabolic conditions, cultures were activated by insulin-like growth factor I/bone morphogenetic protein 2 and oncostatin M/tumor necrosis factor-α, respectively. Histology and markers of bone- and cartilage-turnover were used to evaluate effects of glucocorticoid treatment. RESULTS Prednisolone treatment decreased collagen type-II degradation in immature cartilage, whereas glucocorticoids did not affect collagen type-II in mature cartilage. Glucocorticoids had an anti-catabolic effect on catabolic-activated cartilage from a bovine stifle joint and murine femoral heads. Glucocorticoids decreased viability of all bone cells, leading to a reduction in osteoclastogenesis and bone resorption; however, bone morphogenetic protein 2-stimulated osteoblasts increased bone formation, as opposed to non-stimulated osteoblasts. CONCLUSIONS Using highly robust in vitro models of bone and cartilage turnover, we suggest that effects of glucocorticoids highly depend on the activation and differential stage of the cell targeted in the joint. Present data indicated that glucocorticoid treatment may be beneficial for articular cartilage, although detrimental effects on bone should be taken into account.
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Affiliation(s)
- Suzi H Madsen
- Cartilage Biology and Biomarkers, Nordic Bioscience A/S, Herlev Hovedgade 207, DK-2730 Herlev, Denmark.
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26
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Schrøder JM, Larsen J, Komarova Y, Akhmanova A, Thorsteinsson RI, Grigoriev I, Manguso R, Christensen ST, Pedersen SF, Geimer S, Pedersen LB. EB1 and EB3 promote cilia biogenesis by several centrosome-related mechanisms. Development 2011. [DOI: 10.1242/dev.072231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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27
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Nielsen ME, Rasmussen IA, Kristensen SG, Christensen ST, Møllgård K, Wreford Andersen E, Byskov AG, Yding Andersen C. In human granulosa cells from small antral follicles, androgen receptor mRNA and androgen levels in follicular fluid correlate with FSH receptor mRNA. Mol Hum Reprod 2010; 17:63-70. [PMID: 20843821 DOI: 10.1093/molehr/gaq073] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Human small antral follicles (diameter 3-9 mm) were obtained from ovaries surgically removed for fertility preservation. From the individual aspirated follicles, granulosa cells and the corresponding follicular fluid were isolated in 64 follicles, of which 55 were available for mRNA analysis (24 women). Expressions of androgen receptor (AR) mRNA levels in granulosa cells, and of androstenedione and testosterone in follicular fluid, were correlated to the expression of the FSH receptor (FSHR), LH receptor (LHR), CYP19 and anti-Müllerian Hormone-receptor II (AMHRII) mRNA in the granulosa cells and to the follicular fluid concentrations of AMH, inhibin-B, progesterone and estradiol. AR mRNA expression in granulosa cells and the follicular fluid content of androgens both showed a highly significant positive association with the expression of FSHR mRNA in granulosa cells. AR mRNA expression also correlated significantly with the expression of AMHRII, but did not correlate with any of the hormones in the follicular fluid. These data demonstrate an intimate association between AR expression in immature granulosa cells, and the expression of FSHR in normal small human antral follicles and between the follicular fluid levels of androgen and FSHR expression. This suggests that follicular sensitivity towards FSH stimulation may be augmented by stimulation of androgens via the AR.
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Affiliation(s)
- M E Nielsen
- The Fertility Clinic, Odense University Hospital, Odense , Denmark
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Thorsteinsson RI, Christensen ST, Pedersen LB. Using quantitative PCR to identify kinesin-3 genes that are upregulated during growth arrest in mouse NIH3T3 cells. Methods Cell Biol 2010; 94:67-86. [PMID: 20362085 DOI: 10.1016/s0091-679x(08)94003-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Most cells in our body form a single primary cilium when entering growth arrest. During the past decade, a number of studies have revealed a key role for primary cilia in coordinating a variety of signaling pathways that control important cellular and developmental processes. Consequently, significant effort has been directed toward the identification of genes involved in ciliary assembly and function. Many candidate ciliary genes and proteins have been identified using large-scale "omics" approaches, including proteomics, transcriptomics, and comparative genomics. Although such large-scale approaches can be extremely informative, additional validation of candidate ciliary genes using alternative "small-scale" approaches is often necessary. Here we describe a quantitative PCR-based method that can be used to screen groups of genes for those that are upregulated during growth arrest in cultured mouse NIH3T3 cells and those that might have cilia-related functions. We employed this method to specifically search for mouse kinesin-3 genes that are upregulated during growth arrest and identified three such genes (Kif13A, Kif13B, and Kif16A). In principle, however, the method can be extended to identify other genes or gene families that are upregulated during growth arrest.
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Affiliation(s)
- Rikke I Thorsteinsson
- Department of Biology, Section of Cell and Developmental Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark
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29
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Affiliation(s)
- Peter Satir
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, 10461 NY, USA.
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Schneider L, Cammer M, Lehman J, Nielsen SK, Guerra CF, Veland IR, Stock C, Hoffmann EK, Yoder BK, Schwab A, Satir P, Christensen ST. Directional cell migration and chemotaxis in wound healing response to PDGF-AA are coordinated by the primary cilium in fibroblasts. Cell Physiol Biochem 2010; 25:279-92. [PMID: 20110689 DOI: 10.1159/000276562] [Citation(s) in RCA: 188] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2009] [Indexed: 12/28/2022] Open
Abstract
Cell motility and migration play pivotal roles in numerous physiological and pathophysiological processes including development and tissue repair. Cell migration is regulated through external stimuli such as platelet-derived growth factor-AA (PDGF-AA), a key regulator in directional cell migration during embryonic development and a chemoattractant during postnatal migratory responses including wound healing. We previously showed that PDGFRalpha signaling is coordinated by the primary cilium in quiescent cells. However, little is known about the function of the primary cilium in cell migration. Here we used micropipette analysis to show that a normal chemosensory response to PDGF-AA in fibroblasts requires the primary cilium. In vitro and in vivo wound healing assays revealed that in ORPK mouse (IFT88(Tg737Rpw)) fibroblasts, where ciliary assembly is defective, chemotaxis towards PDGF-AA is absent, leading to unregulated high speed and uncontrolled directional cell displacement during wound closure, with subsequent defects in wound healing. These data suggest that in coordination with cytoskeletal reorganization, the fibroblast primary cilium functions via ciliary PDGFRalpha signaling to monitor directional movement during wound healing.
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Affiliation(s)
- Linda Schneider
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, DK-2100 Copenhagen OE, Denmark
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Awan A, Oliveri RS, Jensen PL, Christensen ST, Andersen CY. Immunoflourescence and mRNA analysis of human embryonic stem cells (hESCs) grown under feeder-free conditions. Methods Mol Biol 2010; 584:195-210. [PMID: 19907979 DOI: 10.1007/978-1-60761-369-5_11] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This chapter describes the procedures in order to do immunofluorescence (IF) microscopy and quantitative PCR (qPCR) analysis of human embryonic stem cells (hESCs) grown specifically under feeder-free conditions. A detailed protocol outlining the steps from initially growing the cells, passaging onto 16-well glass chambers, and continuing with the general IF and qPCR steps will be provided. The techniques will be illustrated with new results on cellular localization of transcriptional factors and components of the Hedgehog, Wnt, and PDGF signaling pathways to primary cilia in stem cell maintenance and differentiation. Furthermore, a sample qPCR experiment will be shown illustrating that these techniques can be important tools in answering basic questions about hESC biology.
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Affiliation(s)
- Aashir Awan
- Laboratory for Reproductive Biology, University Hospital of Copenhagen, Copenhagen, Denmark
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Clement CA, Larsen LA, Christensen ST. Using nucleofection of siRNA constructs for knockdown of primary cilia in P19.CL6 cancer stem cell differentiation into cardiomyocytes. Methods Cell Biol 2009; 94:181-97. [PMID: 20362091 DOI: 10.1016/s0091-679x(08)94009-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Primary cilia assemble as solitary organelles in most mammalian cells during growth arrest and are thought to coordinate a series of signal transduction pathways required for cell cycle control, cell migration, and cell differentiation during development and in tissue homeostasis. Recently, primary cilia were suggested to control pluripotency, proliferation, and/or differentiation of stem cells, which may comprise an important source in regenerative biology. We here provide a method using a P19.CL6 embryonic carcinoma (EC) stem cell line to study the function of the primary cilium in early cardiogenesis. By knocking down the formation of the primary cilium by nucleofection of plasmid DNA with siRNA sequences against genes essential in ciliogenesis (IFT88 and IFT20) we block hedgehog (Hh) signaling in P19.CL6 cells as well as the differentiation of the cells into beating cardiomyocytes (Clement et al., 2009). Immunofluorescence microscopy, western blotting, and quantitative PCR analysis were employed to delineate the molecular and cellular events in cilia-dependent cardiogenesis. We optimized the nucleofection procedure to generate strong reduction in the frequency of ciliated cells in the P19.CL6 culture.
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Affiliation(s)
- Christian A Clement
- Department of Biology, Section of Cell and Developmental Biology, University of Copenhagen, DK-2100 Copenhagen OE, Denmark
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Clement CA, Kristensen SG, Møllgård K, Pazour GJ, Yoder BK, Larsen LA, Christensen ST. The primary cilium coordinates early cardiogenesis and hedgehog signaling in cardiomyocyte differentiation. J Cell Sci 2009; 122:3070-82. [PMID: 19654211 DOI: 10.1242/jcs.049676] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Defects in the assembly or function of primary cilia, which are sensory organelles, are tightly coupled to developmental defects and diseases in mammals. Here, we investigated the function of the primary cilium in regulating hedgehog signaling and early cardiogenesis. We report that the pluripotent P19.CL6 mouse stem cell line, which can differentiate into beating cardiomyocytes, forms primary cilia that contain essential components of the hedgehog pathway, including Smoothened, Patched-1 and Gli2. Knockdown of the primary cilium by Ift88 and Ift20 siRNA or treatment with cyclopamine, an inhibitor of Smoothened, blocks hedgehog signaling in P19.CL6 cells, as well as differentiation of the cells into beating cardiomyocytes. E11.5 embryos of the Ift88(tm1Rpw) (Ift88-null) mice, which form no cilia, have ventricular dilation, decreased myocardial trabeculation and abnormal outflow tract development. These data support the conclusion that cardiac primary cilia are crucial in early heart development, where they partly coordinate hedgehog signaling.
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Veland IR, Awan A, Pedersen LB, Yoder BK, Christensen ST. Primary cilia and signaling pathways in mammalian development, health and disease. Nephron Physiol 2009; 111:p39-53. [PMID: 19276629 PMCID: PMC2881330 DOI: 10.1159/000208212] [Citation(s) in RCA: 204] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Although first described as early as 1898 and long considered a vestigial organelle of little functional importance, the primary cilium has become one of the hottest research topics in modern cell biology and physiology. Primary cilia are nonmotile sensory organelles present in a single copy on the surface of most growth-arrested or differentiated mammalian cells, and defects in their assembly or function are tightly coupled to many developmental defects, diseases and disorders. In normal tissues, the primary cilium coordinates a series of signal transduction pathways, including Hedgehog, Wnt, PDGFRalpha and integrin signaling. In the kidney, the primary cilium may function as a mechano-, chemo- and osmosensing unit that probes the extracellular environment and transmits signals to the cell via, e.g., polycystins, which depend on ciliary localization for appropriate function. Indeed, hypomorphic mutations in the mouse ift88 (previously called Tg737) gene, which encodes a ciliogenic intraflagellar transport protein, result in malformation of primary cilia, and in the collecting ducts of kidney tubules this is accompanied by development of autosomal recessive polycystic kidney disease (PKD). While PKD was one of the first diseases to be linked to dysfunctional primary cilia, defects in this organelle have subsequently been associated with many other phenotypes, including cancer, obesity, diabetes as well as a number of developmental defects. Collectively, these disorders of the cilium are now referred to as the ciliopathies. In this review, we provide a brief overview of the structure and function of primary cilia and some of their roles in coordinating signal transduction pathways in mammalian development, health and disease.
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Affiliation(s)
- Iben R Veland
- Department of Biology, Section of Cell and Developmental Biology, University of Copenhagen, Copenhagen, Denmark
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35
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Abstract
Primary cilia are microtubule-based, hair-like sensory organelles present on the surface of most growth-arrested cells in our body. Recent research has demonstrated a crucial role for primary cilia in regulating vertebrate developmental pathways and tissue homeostasis, and defects in genes involved in primary cilia assembly or function have been associated with a panoply of disorders and diseases, including polycystic kidney disease, left-right asymmetry defects, hydrocephalus, and Bardet Biedl Syndrome. Here we provide an up-to-date review focused on the molecular mechanisms involved in the assembly of primary cilia in vertebrate cells. We present an overview of the early stages of the cilia assembly process, as well as a description of the intraflagellar transport (IFT) system. IFT is a highly conserved process required for assembly of almost all eukaryotic cilia and flagella, and much of our current knowledge about IFT is based on studies performed in Chlamydomonas and Caenorhabditis elegans. Therefore, our review of the IFT literature includes studies performed in these two model organisms. The role of several non-IFT proteins (e.g., centrosomal proteins) in the ciliary assembly process is also discussed.
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Affiliation(s)
- Lotte B Pedersen
- Department of Biology, Section of Cell and Molecular Biology, University of Copenhagen, Copenhagen, Denmark.
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Kiprilov EN, Awan A, Desprat R, Velho M, Clement CA, Byskov AG, Andersen CY, Satir P, Bouhassira EE, Christensen ST, Hirsch RE. Human embryonic stem cells in culture possess primary cilia with hedgehog signaling machinery. ACTA ACUST UNITED AC 2008; 180:897-904. [PMID: 18332216 PMCID: PMC2265400 DOI: 10.1083/jcb.200706028] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Human embryonic stem cells (hESCs) are potential therapeutic tools and models of human development. With a growing interest in primary cilia in signal transduction pathways that are crucial for embryological development and tissue differentiation and interest in mechanisms regulating human hESC differentiation, demonstrating the existence of primary cilia and the localization of signaling components in undifferentiated hESCs establishes a mechanistic basis for the regulation of hESC differentiation. Using electron microscopy (EM), immunofluorescence, and confocal microscopies, we show that primary cilia are present in three undifferentiated hESC lines. EM reveals the characteristic 9 + 0 axoneme. The number and length of cilia increase after serum starvation. Important components of the hedgehog (Hh) pathway, including smoothened, patched 1 (Ptc1), and Gli1 and 2, are present in the cilia. Stimulation of the pathway results in the concerted movement of Ptc1 out of, and smoothened into, the primary cilium as well as up-regulation of GLI1 and PTC1. These findings show that hESCs contain primary cilia associated with working Hh machinery.
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Affiliation(s)
- Enko N Kiprilov
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Abstract
In the past half century, beginning with electron microscopic studies of 9 + 2 motile and 9 + 0 primary cilia, novel insights have been obtained regarding the structure and function of mammalian cilia. All cilia can now be viewed as sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation. This view has had unanticipated consequences for our understanding of developmental processes and human disease.
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Affiliation(s)
- Peter Satir
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, USA
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Schrøder JM, Schneider L, Christensen ST, Pedersen LB. EB1 is required for primary cilia assembly in fibroblasts. Curr Biol 2008; 17:1134-9. [PMID: 17600711 DOI: 10.1016/j.cub.2007.05.055] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 05/21/2007] [Accepted: 05/22/2007] [Indexed: 11/18/2022]
Abstract
EB1 is a small microtubule (MT)-binding protein that associates preferentially with MT plus ends and plays a role in regulating MT dynamics. EB1 also targets other MT-associated proteins to the plus end and thereby regulates interactions of MTs with the cell cortex, mitotic kinetochores, and different cellular organelles [1, 2]. EB1 also localizes to centrosomes and is required for centrosomal MT anchoring and organization of the MT network [3, 4]. We previously showed that EB1 localizes to the flagellar tip and proximal region of the basal body in Chlamydomonas[5], but the function of EB1 in the cilium/flagellum is unknown. We depleted EB1 from NIH3T3 fibroblasts by using siRNA and found that EB1 depletion causes a approximately 50% reduction in the efficiency of primary cilia assembly in serum-starved cells. Expression of dominant-negative EB1 also inhibited cilia formation, and expression of mutant dominant-negative EB1 constructs suggested that binding of EB1 to p150(Glued) is important for cilia assembly. Finally, expression of a C-terminal fragment of the centrosomal protein CAP350, which removes EB1 from the centrosome but not MT plus ends [6], also inhibited ciliogenesis. We conclude that localization of EB1 at the centriole/basal body is required for primary cilia assembly in fibroblasts.
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Affiliation(s)
- Jacob M Schrøder
- Department of Molecular Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark
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Christensen ST, Pedersen SF, Satir P, Veland IR, Schneider L. The primary cilium coordinates signaling pathways in cell cycle control and migration during development and tissue repair. Curr Top Dev Biol 2008; 85:261-301. [PMID: 19147009 DOI: 10.1016/s0070-2153(08)00810-7] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Cell cycle control and migration are critical processes during development and maintenance of tissue functions. Recently, primary cilia were shown to take part in coordination of the signaling pathways that control these cellular processes in human health and disease. In this review, we present an overview of the function of primary cilia and the centrosome in the signaling pathways that regulate cell cycle control and migration with focus on ciliary signaling via platelet-derived growth factor receptor alpha (PDGFRalpha). We also consider how the primary cilium and the centrosome interact with the extracellular matrix, coordinate Wnt signaling, and modulate cytoskeletal changes that impinge on both cell cycle control and cell migration.
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Affiliation(s)
- Søren T Christensen
- Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark
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Pedersen LB, Rompolas P, Christensen ST, Rosenbaum JL, King SM. The lissencephaly protein Lis1 is present in motile mammalian cilia and requires outer arm dynein for targeting to Chlamydomonas flagella. J Cell Sci 2007; 120:858-67. [PMID: 17314247 DOI: 10.1242/jcs.03374] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lissencephaly is a developmental brain disorder characterized by a smooth cerebral surface, thickened cortex and misplaced neurons. Classical lissencephaly is caused by mutations in LIS1, which encodes a WD-repeat protein involved in cytoplasmic dynein regulation, mitosis and nuclear migration. Several proteins required for nuclear migration in Aspergillus bind directly to Lis1, including NudC. Mammalian NudC is highly expressed in ciliated epithelia, and localizes to motile cilia in various tissues. Moreover, a NudC ortholog is upregulated upon deflagellation in Chlamydomonas. We found that mammalian Lis1 localizes to motile cilia in trachea and oviduct, but is absent from non-motile primary cilia. Furthermore, we cloned a gene encoding a Lis1-like protein (CrLis1) from Chlamydomonas. CrLis1 is a approximately 37 kDa protein that contains seven WD-repeat domains, similar to Lis1 proteins from other organisms. Immunoblotting using an anti-CrLis1 antibody revealed that this protein is present in the flagellum and is depleted from flagella of mutants with defective outer dynein arm assembly, including one strain that lacks only the alpha heavy chain/light chain 5 thioredoxin complex. Biochemical experiments confirmed that CrLis1 associates with outer dynein arm components and revealed that CrLis1 binds directly to rat NudC. Our results suggest that Lis1 and NudC are present in cilia and flagella and may regulate outer dynein arm activity.
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Affiliation(s)
- Lotte B Pedersen
- Department of Molecular Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark.
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41
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Abstract
The primary cilium is a hallmark of mammalian tissue cells. Recent research has shown that these organelles display unique sets of selected signal transduction modules including receptors, ion channels, effector proteins and transcription factors that relay chemical and physical stimuli from the extracellular environment in order to control basic cellular processes during embryonic and postnatal development, as well as in tissue homeostasis in adulthood. Consequently, defects in building of the cilium or in transport or function of ciliary signal proteins are associated with a series of pathologies, including developmental disorders and cancer. In this review, we highlight recent examples of the mechanisms by which signal components are selectively targeted and transported to the ciliary membrane and we present an overview of the signal transduction pathways associated with primary and motile cilia in vertebrate cells, including platelet-derived growth factor receptor-alpha (PDGFRalpha), hedgehog and Wnt signaling pathways. Finally, we discuss the functions of these cilia-associated signal transduction pathways and their role in human health and development.
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Affiliation(s)
- Søren T Christensen
- Department of Molecular Biology, Section of Biochemistry, The August Krogh Building, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark.
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Schneider L, Clement CA, Teilmann SC, Pazour GJ, Hoffmann EK, Satir P, Christensen ST. PDGFRalphaalpha signaling is regulated through the primary cilium in fibroblasts. Curr Biol 2006; 15:1861-6. [PMID: 16243034 DOI: 10.1016/j.cub.2005.09.012] [Citation(s) in RCA: 457] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Revised: 09/01/2005] [Accepted: 09/01/2005] [Indexed: 11/28/2022]
Abstract
Recent findings show that cilia are sensory organelles that display specific receptors and ion channels, which transmit signals from the extracellular environment via the cilium to the cell to control tissue homeostasis and function. Agenesis of primary cilia or mislocation of ciliary signal components affects human pathologies, such as polycystic kidney disease and disorders associated with Bardet-Biedl syndrome. Primary cilia are essential for hedgehog ligand-induced signaling cascade regulating growth and patterning. Here, we show that the primary cilium in fibroblasts plays a critical role in growth control via platelet-derived growth factor receptor alpha (PDGFRalpha), which localizes to the primary cilium during growth arrest in NIH3T3 cells and primary cultures of mouse embryonic fibroblasts. Ligand-dependent activation of PDGFRalphaalpha is followed by activation of Akt and the Mek1/2-Erk1/2 pathways, with Mek1/2 being phosphorylated within the cilium and at the basal body. Fibroblasts derived from Tg737(orpk) mutants fail to form normal cilia and to upregulate the level of PDGFRalpha; PDGF-AA fails to activate PDGFRalphaalpha and the Mek1/2-Erk1/2 pathway. Signaling through PDGFRbeta, which localizes to the plasma membrane, is maintained at comparable levels in wild-type and mutant cells. We propose that ciliary PDGFRalphaalpha signaling is linked to tissue homeostasis and to mitogenic signaling pathways.
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Affiliation(s)
- Linda Schneider
- Department of Biochemistry, Institute for Molecular Biology and Physiology, University of Copenhagen, The August Krogh Building, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
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Teilmann SC, Byskov AG, Pedersen PA, Wheatley DN, Pazour GJ, Christensen ST. Localization of transient receptor potential ion channels in primary and motile cilia of the female murine reproductive organs. Mol Reprod Dev 2006; 71:444-52. [PMID: 15858826 DOI: 10.1002/mrd.20312] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have examined the subcellular localization of transient receptor potential (TRP) ion channels and the potential sensory role of cilia in murine female reproductive organs using confocal laser scanning microscopy analysis on ovary and oviduct tissue sections as well as on primary cultures of follicular granulosa cells. We show that the Ca2+ permeable cation channel, polycystin-2, as well as polycystin-1, a receptor that forms a functional protein complex with polycystin 2, distinctively localize to primary cilia emerging from granulosa cells of antral follicles in vivo and in vitro. Both polycystins are localized to motile oviduct cilia and this localization is greatly increased upon ovulatory gonadotropic stimulation. Further, the Ca2+ permeable cation channel, TRP vaniloid 4 (TRPV4), localizes to a sub-population of motile cilia on the epithelial cells of the ampulla and isthmus with high intensity in proximal invaginations of the epithelial folds. These observations are the first to demonstrate ciliary localization of TRP ion channels and their possible receptor function in the female reproductive organs. We suggest that polycystins 1 and 2 play an important role in granulosa cell differentiation and in development and maturation of ovarian follicles. In the oviduct both TRPV4 and polycystins could be important in relaying physiochemical changes in the oviduct upon ovulation.
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Christensen ST, Voss JW, Teilmann SC, Lambert IH. High expression of the taurine transporter TauT in primary cilia of NIH3T3 fibroblasts. Cell Biol Int 2005; 29:347-51. [PMID: 15914036 DOI: 10.1016/j.cellbi.2005.02.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2005] [Accepted: 02/17/2005] [Indexed: 10/25/2022]
Abstract
Taurine, present in high concentrations in various mammalian cells, is essential for regulation of cell volume, cellular oxidative status as well as the cellular Ca2+ homeostasis. Cellular taurine content is a balance between active uptake through the saturable, Na(+)-dependent taurine transporter TauT, and passive release via a volume-sensitive leak pathway. Here we demonstrate that: (i) TauT localizes to the primary cilium of growth-arrested NIH3T3 fibroblasts, (ii) long-term exposure to TNF(alpha) or hypertonic sucrose medium, i.e., growth medium supplemented with 100 mM sucrose, increases ciliary TauT expression and (iii) long-term exposure to hypertonic taurine medium, i.e., growth medium supplemented with 100 mM taurine, reduces ciliary TauT expression. These results point to an important role of taurine in the regulation of physiological processes located to the primary cilium.
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Affiliation(s)
- Søren T Christensen
- Institute of Molecular Biology and Physiology, The August Krogh Building, Department of Biochemistry, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark.
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Teilmann SC, Christensen ST. Localization of the angiopoietin receptors Tie-1 and Tie-2 on the primary cilia in the female reproductive organs. Cell Biol Int 2005; 29:340-6. [PMID: 15893943 DOI: 10.1016/j.cellbi.2005.03.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Accepted: 02/17/2005] [Indexed: 11/18/2022]
Abstract
Blood vessel homeostasis and endothelial cell survival depend on proper signalling through angiopoietin receptors such as the receptor tyrosine kinases Tie-1 and Tie-2. We have studied the presence and subcellular localization of these receptors in murine female reproductive organs using confocal microscopy analysis of antibody stained tissue sections of ovary and oviduct. We show that Tie-2 principally localizes to primary cilia of the surface epithelium of the ovary, bursa and extra-ovarian rete ducts as well as to plasma membranes of ovarian theca and endothelial cells. Primary cilia of follicular granulosa cells were negative. Further, Tie-1 and Tie-2 localized to motile cilia of the oviduct. Western blotting detection and immunolocalization of anti-Tie-2 in ovary and oviduct were abolished by administration of an anti-Tie-2 blocking peptide, confirming antibody specificity. In a series of immunohistochemical analysis on human ovarian tissues we also observed a unique localization of Tie-2 to the primary cilia of ovarian surface epithelium. These observations are the first to show ciliary localization of angiopoietin receptors. Our results support the hypothesis that cilia of the female reproductive organs play a novel and important sensory role in relaying physiochemical changes from the extracellular environment to epithelial cells of the oviduct, the ovary and extra-ovarian tissues.
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Voss JW, Pedersen SF, Christensen ST, Lambert IH. Regulation of the expression and subcellular localization of the taurine transporter TauT in mouse NIH3T3 fibroblasts. ACTA ACUST UNITED AC 2005; 271:4646-58. [PMID: 15606752 DOI: 10.1111/j.1432-1033.2004.04420.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cellular level of the organic osmolyte taurine is a balance between active uptake and passive leak via a volume sensitive pathway. Here, we demonstrate that NIH3T3 mouse fibroblasts express a saturable, high affinity taurine transporter (TauT, Km = 18 microm), and that taurine uptake via TauT is a Na+- and Cl(-)-dependent process with an apparent 2.5 : 1 : 1 Na+/Cl-/taurine stoichiometry. Transport activity is reduced following acute administration of H2O2 or activators of protein kinases A or C. TauT transport activity, expression and nuclear localization are significantly increased upon serum starvation (24 h), exposure to tumour necrosis factor alpha (TNFalpha; 16 h), or hyperosmotic medium (24 h); conditions that are also associated with increased localization of TauT to the cytosolic network of microtubules. Conversely, transport activity, expression and nuclear localization of TauT are reduced in a reversible manner following long-term exposure (24 h) to high extracellular taurine concentration. In contrast to active taurine uptake, swelling-induced taurine release is significantly reduced following preincubation with TNFalpha (16 h) but unaffected by high extracellular taurine concentration (24 h). Thus, in NIH3T3 cells, (a) active taurine uptake reflects TauT expression; (b) TauT activity is modulated by multiple stimuli, both acutely, and at the level of TauT expression; (c) the subcellular localization of TauT is regulated; and (d) volume-sensitive taurine release is not mediated by TauT.
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Affiliation(s)
- Jesper W Voss
- The August Krogh Institute, Biochemical Department, Universitetsparken 13, Copenhagen, Denmark
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47
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Abstract
Cell shrinkage is a hallmark of the apoptotic mode of programmed cell death, but it is as yet unclear whether a reduction in cell volume is a primary activation signal of apoptosis. Here we studied the effect of an acute elevation of osmolarity (NaCl or sucrose additions, final osmolarity 687 mosmol l(-1)) on NIH 3T3 fibroblasts to identify components involved in the signal transduction from shrinkage to apoptosis. After 1.5 h the activity of caspase-3 started to increase followed after 3 h by the appearance of many apoptotic-like bodies. The caspase-3 activity increase was greatly enhanced in cells expressing a constitutively active G protein, Rac (RacV12A3 cell), indicating that Rac acts upstream to caspase-3 activation. The stress-activated protein kinase, p38, was significantly activated by phosphorylation within 30 min after induction of osmotic shrinkage, the phosphorylation being accelerated in fibroblasts overexpressing Rac. Conversely, the activation of the extracellular signal-regulated kinase (Erk1/2) was initially significantly decreased. Subsequent to activation of p38, p53 was activated through serine-15 phosphorylation, and active p53 was translocated from the cytosol to the nucleus. Inhibition of p38 in Rac cells reduced the activation of both p53 and caspase-3. After 60 min in hypertonic medium the rate constants for K+ and taurine efflux were increased, particular in Rac cells. We suggest the following sequence of events in the cell shrinkage-induced apoptotic response: cellular shrinkage activates Rac, with activation of p38, followed by phosphorylation and nuclear translocation of p53, resulting in permeability increases and caspase-3 activation.
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Affiliation(s)
- Martin B Friis
- Department of Biochemistry, Institute of Molecular Biology and Physiology, The August Krogh Building, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark
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Pederson SF, Varming C, Christensen ST, Hoffmann EK. Mechanisms of activation of NHE by cell shrinkage and by calyculin A in Ehrlich ascites tumor cells. J Membr Biol 2002; 189:67-81. [PMID: 12202953 DOI: 10.1007/s00232-001-0190-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2001] [Indexed: 10/27/2022]
Abstract
The Na+/H+ exchanger isoforms NHE1, NHE2, and NHE3 were all found to be expressed in Ehrlich ascites tumor cells, as evaluated by Western blotting and confocal microscopy. Under unstimulated conditions, NHE1 was found predominantly in the plasma membrane, NHE3 intracellularly, and NHE2 in both compartments. Osmotic cell shrinkage elicited a rapid intracellular alkalinization, the sensitivity of which to EIPA (IC50 0.19 microM) and HOE 642 (IC50 0.85 microM) indicated that it predominantly reflected activation of NHE1. NHE activation by osmotic shrinkage was inhibited by the protein kinase C inhibitors chelerythrine (IC50 12.5 microM), Gö 6850 (5 microM), and Gö 6976 (1 microM), and by the p38 MAPK inhibitor SB 203580 (10 microM). Furthermore, hypertonic cell shrinkage elicited a biphasic increase in p38 MAPK phosphorylation, with the first significant increase detectable 2 minutes after the hypertonic challenge. Neither myosin light chain kinase-specific concentrations of ML-7 (IC50 40 microM) nor ERK1/2 inhibition by PD 98059 (50 microM) had any effect on NHE activation. Under isotonic conditions, the serine/threonine protein phosphatase inhibitor calyculin A elicited an EIPA- and HOE 642-inhibitable intracellular alkalinization, indicating NHE1 activation. Similarly, shrinkage-induced NHE activation was potentiated by calyculin A. The calyculin A-induced alkalinization was not associated with an increase in the free, intracellular calcium concentration, but was abolished by chelerythrine. It is concluded that shrinkage-induced NHE activation is dependent on PKC and p38 MAPK, but not on MLCK or ERK1/2. NHE activity under both iso- and hypertonic conditions is increased by inhibition of serine/threonine phosphatases, and this effect appears to be PKC-dependent.
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Affiliation(s)
- S F Pederson
- Department of Biochemistry, August Krogh Institute, University of Copenhagen, 13, Universitetsparken, DK-2100 Copenhagen, Denmark
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Christensen ST, Sørensen H, Beyer NH, Kristiansen K, Rasmussen L, Rasmussen MI. Cell death in Tetrahymena thermophila: new observations on culture conditions. Cell Biol Int 2001; 25:509-19. [PMID: 11407856 DOI: 10.1006/cbir.2000.0689] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously suggested that the cell fate of the protozoan ciliate, Tetrahymena thermophila, effectively relates to a quorum-sensing mechanism where cell-released factors support cell survival and proliferation. The cells have to be present above a critical initial density in a chemically defined nutrient medium in order to release a sufficient level of these factors to allow a new colony to flourish. At a relatively high rate of metabolism and/or macromolecular synthesis and below this critical density, cells began to die abruptly within 30 min of inoculation, and this death took the form of an explosive disintegration lasting less than 50 milliseconds. The cells died at any location in the culture, and the frequency of cell death was always lower in well-filled vials than those with medium/air interface. Cell death was inhibited by the addition of Actinomycin D or through modifications of the culture conditions either by reducing the oxygen tension or by decreasing the temperature of the growth medium. In addition, plastic caps in well-filled vials release substances, which promote cell survival. The fate of low-density cultures is related to certain 'physical' conditions, in addition to the availability of oxygen within closed culture systems.
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Affiliation(s)
- S T Christensen
- Institute of Medical Biology, Department of Anatomy and Cell Biology, University of Southern Denmark, Odense, Denmark.
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