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Villarroya-Beltri C, Guerra S, Sánchez-Madrid F. ISGylation - a key to lock the cell gates for preventing the spread of threats. J Cell Sci 2017; 130:2961-2969. [PMID: 28842471 DOI: 10.1242/jcs.205468] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Interferon stimulated gene 15 (ISG15) is an ubiquitin-like protein whose expression and conjugation to targets (ISGylation) is induced by infection, interferon (IFN)-α and -β, ischemia, DNA damage and aging. Attention has historically focused on the antiviral effects of ISGylation, which blocks the entry, replication or release of different intracellular pathogens. However, recently, new functions of ISGylation have emerged that implicate it in multiple cellular processes, such as DNA repair, autophagy, protein translation and exosome secretion. In this Review, we discuss the induction and conjugation of ISG15, as well as the functions of ISGylation in the prevention of infections and in cancer progression. We also offer a novel perspective with regard to the latest findings on this pathway, with special attention to the role of ISGylation in the inhibition of exosome secretion, which is mediated by fusion of multivesicular bodies with lysosomes. Finally, we propose that under conditions of stress or infection, ISGylation acts as a defense mechanism to inhibit normal protein translation by modifying protein kinase R (PKR, also known as EIF2AK2), while any newly synthesized proteins are being tagged and thus marked as potentially dangerous. Then, the endosomal system is re-directed towards protein degradation at the lysosome, to effectively 'lock' the cell gates and thus prevent the spread of pathogens, prions and deleterious aggregates through exosomes.
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Affiliation(s)
- Carolina Villarroya-Beltri
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.,Immunology Service, Hospital de la Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.,CIBER de Enfermedades Cardiovasculares, Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Susana Guerra
- Preventive Medicine Department, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Francisco Sánchez-Madrid
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain .,Immunology Service, Hospital de la Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.,CIBER de Enfermedades Cardiovasculares, Instituto de Salud Carlos III, 28029 Madrid, Spain
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52
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Kohli P, Höhne M, Jüngst C, Bertsch S, Ebert LK, Schauss AC, Benzing T, Rinschen MM, Schermer B. The ciliary membrane-associated proteome reveals actin-binding proteins as key components of cilia. EMBO Rep 2017; 18:1521-1535. [PMID: 28710093 DOI: 10.15252/embr.201643846] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 06/06/2017] [Accepted: 06/13/2017] [Indexed: 01/01/2023] Open
Abstract
Primary cilia are sensory, antennae-like organelles present on the surface of many cell types. They have been involved in a variety of diseases collectively termed ciliopathies. As cilia are essential regulators of cell signaling, the composition of the ciliary membrane needs to be strictly regulated. To understand regulatory processes at the ciliary membrane, we report the targeting of a genetically engineered enzyme specifically to the ciliary membrane to allow biotinylation and identification of the membrane-associated proteome. Bioinformatic analysis of the comprehensive dataset reveals high-stoichiometric presence of actin-binding proteins inside the cilium. Immunofluorescence stainings and complementary interaction proteomic analyses confirm these findings. Depolymerization of branched F-actin causes further enrichment of the actin-binding and actin-related proteins in cilia, including Myosin 5a (Myo5a). Interestingly, Myo5a knockout decreases ciliation while enhanced levels of Myo5a are observed in cilia upon induction of ciliary disassembly. In summary, we present a novel approach to investigate dynamics of the ciliary membrane proteome in mammalian cells and identify actin-binding proteins as mechanosensitive components of cilia that might have important functions in cilia membrane dynamics.
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Affiliation(s)
- Priyanka Kohli
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany.,Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Christian Jüngst
- Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Sabine Bertsch
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany.,Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Lena K Ebert
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Astrid C Schauss
- Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany.,Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Markus M Rinschen
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany.,Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany .,Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Cologne, Germany.,Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
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53
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May-Simera H, Nagel-Wolfrum K, Wolfrum U. Cilia - The sensory antennae in the eye. Prog Retin Eye Res 2017; 60:144-180. [PMID: 28504201 DOI: 10.1016/j.preteyeres.2017.05.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 05/04/2017] [Accepted: 05/08/2017] [Indexed: 12/21/2022]
Abstract
Cilia are hair-like projections found on almost all cells in the human body. Originally believed to function merely in motility, the function of solitary non-motile (primary) cilia was long overlooked. Recent research has demonstrated that primary cilia function as signalling hubs that sense environmental cues and are pivotal for organ development and function, tissue hoemoestasis, and maintenance of human health. Cilia share a common anatomy and their diverse functional features are achieved by evolutionarily conserved functional modules, organized into sub-compartments. Defects in these functional modules are responsible for a rapidly growing list of human diseases collectively termed ciliopathies. Ocular pathogenesis is common in virtually all classes of syndromic ciliopathies, and disruptions in cilia genes have been found to be causative in a growing number of non-syndromic retinal dystrophies. This review will address what is currently known about cilia contribution to visual function. We will focus on the molecular and cellular functions of ciliary proteins and their role in the photoreceptor sensory cilia and their visual phenotypes. We also highlight other ciliated cell types in tissues of the eye (e.g. lens, RPE and Müller glia cells) discussing their possible contribution to disease progression. Progress in basic research on the cilia function in the eye is paving the way for therapeutic options for retinal ciliopathies. In the final section we describe the latest advancements in gene therapy, read-through of non-sense mutations and stem cell therapy, all being adopted to treat cilia dysfunction in the retina.
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Affiliation(s)
- Helen May-Simera
- Institute of Molecular Physiology, Cilia Biology, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
| | - Kerstin Nagel-Wolfrum
- Institute of Molecular Physiology, Molecular Cell Biology, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
| | - Uwe Wolfrum
- Institute of Molecular Physiology, Molecular Cell Biology, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
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54
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Palander O, El-Zeiry M, Trimble WS. Uncovering the Roles of Septins in Cilia. Front Cell Dev Biol 2017; 5:36. [PMID: 28428954 PMCID: PMC5382219 DOI: 10.3389/fcell.2017.00036] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 03/23/2017] [Indexed: 01/22/2023] Open
Abstract
Septins are a family of GTP-binding proteins that associate with cellular membranes and the cytoskeleton. Their ability to polymerize into filamentous structures permits them to serve as diffusion barriers for membrane proteins and as multi-molecular scaffolds that recruit components of signaling pathways. At the cellular level, septins contribute to the regulation of numerous processes, including cytokinesis, cell polarity, cell migration, and many others. In this review, we discuss emerging evidence for roles of mammalian septins in the biogenesis and function of flagella and cilia, and how this may impact human diseases such as ciliopathies.
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Affiliation(s)
- Oliva Palander
- Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada.,Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - Maha El-Zeiry
- Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada.,Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - William S Trimble
- Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada.,Department of Biochemistry, University of TorontoToronto, ON, Canada.,Department of Physiology, University of TorontoToronto, ON, Canada
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55
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Ma XN, Ma CX, Shi WG, Zhou J, Ma HP, Gao YH, Xian CJ, Chen KM. Primary cilium is required for the stimulating effect of icaritin on osteogenic differentiation and mineralization of osteoblasts in vitro. J Endocrinol Invest 2017; 40:357-366. [PMID: 27770387 DOI: 10.1007/s40618-016-0568-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 10/13/2016] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Icaritin, one effective metabolite of Herba Epimedii-derived flavonoid icariin, has a strong osteogenic activity. However, its action mechanism remains unclear. Since primary cilia have been shown to play a pivotal role in regulating the osteogenesis, we hypothesized primary cilia are indispensable in mediating icaritin osteogenic effect. MATERIALS AND METHODS Primary rat calvarial osteoblasts were transfected with siRNA1 targeting intraflagellar transport protein 88 (IFT88), a protein required for ciliogenesis, to prevent formation of primary cilium and were treated with 10-6 M icaritin. RESULTS Alkaline phosphatase (ALP) activity was significantly increased after 3 days in cells transfected with scrambled siRNA control and treated by icaritin (SC+I group) compared to cells transfected with scrambled siRNA control only (SC group). ALP activity after IFT88 siRNA1 transfection and icaritin treatment (siRNA1+I group) was significantly lower than that of SC+I group. Formation of ALP positively stained colonies after 6 days, osteocalcin secretion after 9 days and formation of calcified nodules after 12 days displayed a similar tendency among the three groups. mRNA expression of osteogenesis-related genes ALP, BMP-2, COL1α, RUNX-2 and OSX after 24 h was significantly increased in SC+I group, but was not different with SC group in siRNA1+I group. Protein levels of BMP-2, COL1α, RUNX-2 and OSX after 48 h showed the similar tendency with gene expression. CONCLUSION Primary cilia are important in mediating icaritin-stimulated osteogenic differentiation and may be a novel target for pharmacological therapies for bone loss.
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Affiliation(s)
- X-N Ma
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou, 730050, People's Republic of China
- Department of Endocrinology, The First Hospital of Lanzhou University, Lanzhou, 730000, People's Republic of China
| | - C-X Ma
- Department of Laboratory, Affiliated Hospital of Gansu University of Chinese Medicine, Lanzhou, 730000, People's Republic of China
| | - W-G Shi
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou, 730050, People's Republic of China
| | - J Zhou
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou, 730050, People's Republic of China
| | - H-P Ma
- Department of Pharmacy, Lanzhou General Hospital of CPLA, Lanzhou, 730050, People's Republic of China
| | - Y-H Gao
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou, 730050, People's Republic of China
| | - C J Xian
- Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5001, Australia
| | - K-M Chen
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou, 730050, People's Republic of China.
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56
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Bustos-Morán E, Blas-Rus N, Martin-Cófreces NB, Sánchez-Madrid F. Microtubule-associated protein-4 controls nanovesicle dynamics and T cell activation. J Cell Sci 2017; 130:1217-1223. [PMID: 28209780 DOI: 10.1242/jcs.199042] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 02/07/2017] [Indexed: 01/06/2023] Open
Abstract
The immune synapse (IS) is a specialized structure formed at the contact area between T lymphocytes and antigen-presenting cells (APCs) that is essential for the adaptive immune response. Proper T cell activation requires its polarization towards the APC, which is highly dependent on the tubulin cytoskeleton. Microtubule-associated protein-4 (MAP4) is a microtubule (MT)-stabilizing protein that controls MTs in physiological processes, such as cell division, migration, vesicular transport or primary cilia formation. In this study, we assessed the role of MAP4 in T cell activation. MAP4 decorates the pericentrosomal area and MTs of the T cell, and it is involved in MT detyrosination and stable assembly in response to T cell activation. In addition, MAP4 prompts the timely translocation of the MT-organizing center (MTOC) towards the IS and the dynamics of signaling nanovesicles that sustains T cell activation. However, MAP4 acts as a negative regulator of other T cell activation-related signals, including diacylglycerol (DAG) production and IL2 secretion. Our data indicate that MAP4 acts as a checkpoint molecule that balances positive and negative hallmarks of T cell activation.
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Affiliation(s)
- Eugenio Bustos-Morán
- Laboratory of Intercellular communication, Fundación CNIC, Madrid 28029, Spain.,Servicio de Inmunología, Hospital Universitario de la Princesa, UAM, IIS-IP, Madrid 28006, Spain
| | - Noelia Blas-Rus
- Laboratory of Intercellular communication, Fundación CNIC, Madrid 28029, Spain.,Servicio de Inmunología, Hospital Universitario de la Princesa, UAM, IIS-IP, Madrid 28006, Spain
| | - Noa Beatriz Martin-Cófreces
- Laboratory of Intercellular communication, Fundación CNIC, Madrid 28029, Spain.,Servicio de Inmunología, Hospital Universitario de la Princesa, UAM, IIS-IP, Madrid 28006, Spain.,CIBER Cardiovascular, ISCIII, Madrid, 28029, Spain
| | - Francisco Sánchez-Madrid
- Laboratory of Intercellular communication, Fundación CNIC, Madrid 28029, Spain .,Servicio de Inmunología, Hospital Universitario de la Princesa, UAM, IIS-IP, Madrid 28006, Spain.,CIBER Cardiovascular, ISCIII, Madrid, 28029, Spain
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57
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Abstract
Septins are GTP-binding and membrane-interacting proteins with a highly conserved domain structure involved in various cellular processes, including cytoskeleton organization, cytokinesis, and membrane dynamics. To date, 13 different septin genes have been identified in mammals (SEPT1 to SEPT12 and SEPT14), which can be classified into four distinct subgroups based on the sequence homology of their domain structure (SEPT2, SEPT3, SEPT6, and SEPT7 subgroup). The family members of these subgroups have a strong affinity for other septins and form apolar tri-, hexa-, or octameric complexes consisting of multiple septin polypeptides. The first characterized core complex is the hetero-trimer SEPT2-6-7. Within these complexes single septins can be exchanged in a subgroup-specific manner. Hexamers contain SEPT2 and SEPT6 subgroup members and SEPT7 in two copies each whereas the octamers additionally comprise two SEPT9 subgroup septins. The various isoforms seem to determine the function and regulation of the septin complex. Septins self-assemble into higher-order structures, including filaments and rings in orders, which are typical for different cell types. Misregulation of septins leads to human diseases such as neurodegenerative and bleeding disorders. In non-dividing cells such as neuronal tissue and platelets septins have been associated with exocytosis. However, many mechanistic details and roles attributed to septins are poorly understood. We describe here some important mammalian septin interactions with a special focus on the clinically relevant septin interactions.
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Affiliation(s)
- Katharina Neubauer
- Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, Faculty of Medicine, Medical Center-University of Freiburg Freiburg, Germany
| | - Barbara Zieger
- Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, Faculty of Medicine, Medical Center-University of Freiburg Freiburg, Germany
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58
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Vagin O, Beenhouwer DO. Septins: Regulators of Protein Stability. Front Cell Dev Biol 2016; 4:143. [PMID: 28066764 PMCID: PMC5168428 DOI: 10.3389/fcell.2016.00143] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 12/02/2016] [Indexed: 12/31/2022] Open
Abstract
Septins are small GTPases that play a role in several important cellular processes. In this review, we focus on the roles of septins in protein stabilization. Septins may regulate protein stability by: (1) interacting with proteins involved in degradation pathways, (2) regulating the interaction between transmembrane proteins and cytoskeletal proteins, (3) affecting the mobility of transmembrane proteins in lipid bilayers, and (4) modulating the interaction of proteins with their adaptor or signaling proteins. In this context, we discuss the role of septins in protecting four different proteins from degradation. First we consider botulinum neurotoxin serotype A (BoNT/A) and the contribution of septins to its extraordinarily long intracellular persistence. Next, we discuss the role of septins in stabilizing the receptor tyrosine kinases EGFR and ErbB2. Finally, we consider the contribution of septins in protecting hypoxia-inducible factor 1α (HIF-1α) from degradation.
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Affiliation(s)
- Olga Vagin
- Department of Physiology, Geffen School of Medicine at UCLALos Angeles, CA, USA; VA Greater Los Angeles Healthcare SystemLos Angeles, CA, USA
| | - David O Beenhouwer
- Department of Medicine, Geffen School of Medicine at UCLALos Angeles, CA, USA; Division of Infectious Diseases, VA Greater Los Angeles Health Care SystemLos Angeles, CA, USA
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59
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Dyson JM, Conduit SE, Feeney SJ, Hakim S, DiTommaso T, Fulcher AJ, Sriratana A, Ramm G, Horan KA, Gurung R, Wicking C, Smyth I, Mitchell CA. INPP5E regulates phosphoinositide-dependent cilia transition zone function. J Cell Biol 2016; 216:247-263. [PMID: 27998989 PMCID: PMC5223597 DOI: 10.1083/jcb.201511055] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Revised: 09/19/2016] [Accepted: 12/02/2016] [Indexed: 02/07/2023] Open
Abstract
Dyson et al. demonstrate that the inositol polyphosphate 5-phosphatase INPP5E is essential for Hedgehog-dependent embryonic development. By regulating PI(4,5)P2 and PI(3,4,5)P3 signals at cilia, INPP5E contributes to cilia transition zone function and thereby Smoothened accumulation at cilia. Human ciliopathies, including Joubert syndrome (JBTS), arise from cilia dysfunction. The inositol polyphosphate 5-phosphatase INPP5E localizes to cilia and is mutated in JBTS. Murine Inpp5e ablation is embryonically lethal and recapitulates JBTS, including neural tube defects and polydactyly; however, the underlying defects in cilia signaling and the function of INPP5E at cilia are still emerging. We report Inpp5e−/− embryos exhibit aberrant Hedgehog-dependent patterning with reduced Hedgehog signaling. Using mouse genetics, we show increasing Hedgehog signaling via Smoothened M2 expression rescues some Inpp5e−/− ciliopathy phenotypes and “normalizes” Hedgehog signaling. INPP5E’s phosphoinositide substrates PI(4,5)P2 and PI(3,4,5)P3 accumulated at the transition zone (TZ) in Hedgehog-stimulated Inpp5e−/− cells, which was associated with reduced recruitment of TZ scaffolding proteins and reduced Smoothened levels at cilia. Expression of wild-type, but not 5-phosphatase-dead, INPP5E restored TZ molecular organization and Smoothened accumulation at cilia. Therefore, we identify INPP5E as an essential point of convergence between Hedgehog and phosphoinositide signaling at cilia that maintains TZ function and Hedgehog-dependent embryonic development.
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Affiliation(s)
- Jennifer M Dyson
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Sarah E Conduit
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Sandra J Feeney
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Sandra Hakim
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Tia DiTommaso
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Alex J Fulcher
- Monash Micro Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Absorn Sriratana
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Georg Ramm
- Monash Micro Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Kristy A Horan
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Rajendra Gurung
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Carol Wicking
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Ian Smyth
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.,Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Christina A Mitchell
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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Xie YF, Shi WG, Zhou J, Gao YH, Li SF, Fang QQ, Wang MG, Ma HP, Wang JF, Xian CJ, Chen KM. Pulsed electromagnetic fields stimulate osteogenic differentiation and maturation of osteoblasts by upregulating the expression of BMPRII localized at the base of primary cilium. Bone 2016; 93:22-32. [PMID: 27622883 DOI: 10.1016/j.bone.2016.09.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 09/06/2016] [Accepted: 09/09/2016] [Indexed: 12/21/2022]
Abstract
Pulsed electromagnetic fields (PEMFs) have been considered as a potential candidate for the prevention and treatment of osteoporosis, however, the mechanism of its action is still elusive. We have previously reported that 50Hz 0.6mT PEMFs stimulate osteoblastic differentiation and mineralization in a primary cilium- dependent manner, but did not know the reason. In the current study, we found that the PEMFs promoted osteogenic differentiation and maturation of rat calvarial osteoblasts (ROBs) by activating bone morphogenetic protein BMP-Smad1/5/8 signaling on the condition that primary cilia were normal. Further studies revealed that BMPRII, the primary binding receptor of BMP ligand, was readily and strongly upregulated by PEMF treatment and localized at the bases of primary cilia. Abrogation of primary cilia with small interfering RNA sequence targeting IFT88 abolished the PEMF-induced upregulation of BMPRII and its ciliary localization. Knockdown of BMPRII expression level with RNA interference had no effects on primary cilia but significantly decreased the promoting effect of PEMFs on osteoblastic differentiation and maturation. These results indicated that PEMFs stimulate osteogenic differentiation and maturation of osteoblast by primary cilium-mediated upregulation of BMPRII expression and subsequently activation of BMP-Smad1/5/8 signaling, and that BMPRII is the key component linking primary cilium and BMP-Smad1/5/8 pathway. This study has thus revealed the molecular mechanism for the osteogenic effect of PEMFs.
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Affiliation(s)
- Yan-Fang Xie
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
| | - Wen-Gui Shi
- Gansu Key laboratory of Space Radiobiology, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China.
| | - Jian Zhou
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
| | - Yu-Hai Gao
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
| | - Shao-Feng Li
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
| | - Qing-Qing Fang
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
| | - Ming-Gang Wang
- School of life science and engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China.
| | - Hui-Ping Ma
- Department of Pharmacy, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
| | - Ju-Fang Wang
- Gansu Key laboratory of Space Radiobiology, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China.
| | - Cory J Xian
- Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA 5001, Australia.
| | - Ke-Ming Chen
- Institute of Orthopaedics, Lanzhou General Hospital, Lanzhou Command of CPLA, Lanzhou 730050, People's Republic of China.
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61
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Poüs C, Klipfel L, Baillet A. Cancer-Related Functions and Subcellular Localizations of Septins. Front Cell Dev Biol 2016; 4:126. [PMID: 27878118 PMCID: PMC5099157 DOI: 10.3389/fcell.2016.00126] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 10/24/2016] [Indexed: 12/16/2022] Open
Abstract
Since the initial discovery of septin family GTPases, the understanding of their molecular organization and cellular roles keeps being refined. Septins have been involved in many physiological processes and the misregulation of specific septin gene expression has been implicated in diverse human pathologies, including neurological disorders and cancer. In this minireview, we focus on the importance of the subunit composition and subcellular localization of septins relevant to tumor initiation, progression, and metastasis. We especially underline the importance of septin polymer composition and of their association with the plasma membrane, actin, or microtubules in cell functions involved in cancer and in resistance to cancer therapies. Through their scaffolding role, their function in membrane compartmentalization or through their protective function against protein degradation, septins also emerge as critical organizers of membrane-associated proteins and of signaling pathways implicated in cancer-associated angiogenesis, apoptosis, polarity, migration, proliferation, and in metastasis. Also, the question as to which of the free monomers, hetero-oligomers, or filaments is the functional form of mammalian septins is raised and the control over their spatial and temporal localization is discussed. The increasing amount of crosstalks identified between septins and cellular signaling mediators reinforces the exciting possibility that septins could be new targets in anti-cancer therapies or in therapeutic strategies to limit drug resistance.
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Affiliation(s)
- Christian Poüs
- Institut National de la Santé et de la Recherche Médicale, UMR-S 1193, Université Paris-Sud, Université Paris-SaclayChâtenay-Malabry, France; Laboratoire de Biochimie-Hormonologie, Hôpital Antoine Béclère, AP-HPClamart, France
| | - Laurence Klipfel
- Institut National de la Santé et de la Recherche Médicale, UMR-S 1193, Université Paris-Sud, Université Paris-SaclayChâtenay-Malabry, France; Département de Génétique, Institut de la Vision, Université Pierre et Marie Curie Paris 06, Sorbonne Universités, Institut National de la Santé et de la Recherche Médicale UMR-S 968, Centre National de la Recherche Scientifique UMR 7210Paris, France
| | - Anita Baillet
- Institut National de la Santé et de la Recherche Médicale, UMR-S 1193, Université Paris-Sud, Université Paris-Saclay Châtenay-Malabry, France
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Kukic I, Rivera-Molina F, Toomre D. The IN/OUT assay: a new tool to study ciliogenesis. Cilia 2016; 5:23. [PMID: 27493724 PMCID: PMC4972980 DOI: 10.1186/s13630-016-0044-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 05/26/2016] [Indexed: 11/24/2022] Open
Abstract
Background Nearly all cells have a primary cilia on their surface, which functions as a cellular antennae. Primary cilia assembly begins intracellularly and eventually emerges extracellularly. However, current ciliogenesis assays, which detect cilia length and number, do not monitor ciliary stages. Methods We developed a new assay that detects antibody access to a fluorescently tagged ciliary transmembrane protein, which revealed three ciliary states: classified as ‘inside,’ ‘outside,’ or ‘partial’ cilia. Results Strikingly, most cilia in RPE cells only partially emerged and many others were long and intracellular, which would be indistinguishable by conventional assays. Importantly, these states switch with starvation-induced ciliogenesis and the cilia can emerge both on the dorsal and ventral surface of the cell. Our assay further allows new molecular and functional studies of the ‘ciliary pocket,’ a deep plasma membrane invagination whose function is unclear. Molecularly, we show colocalization of EHD1, Septin 9 and glutamylated tubulin with the ciliary pocket. Conclusions Together, the IN/OUT assay is not only a new tool for easy and quantifiable visualization of different ciliary stages, but also allows molecular characterization of intermediate ciliary states. Electronic supplementary material The online version of this article (doi:10.1186/s13630-016-0044-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ira Kukic
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06510 USA
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06510 USA
| | - Derek Toomre
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06510 USA
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63
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Kang H, Lew DJ. How do cells know what shape they are? Curr Genet 2016; 63:75-77. [PMID: 27313005 DOI: 10.1007/s00294-016-0623-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 06/07/2016] [Accepted: 06/09/2016] [Indexed: 10/21/2022]
Abstract
Studies on a yeast cell cycle checkpoint that can delay mitosis depending on whether cells have built a bud have identified a "sensor" that seems to recognize the organization of filament-forming septin proteins. Innovative work applying correlative light and platinum replica electron microscopy suggests that the informative septin organization involves parallel alignment of septin filaments, and another striking study shows that septin filaments prefer to populate membranes that have positive micron-scale curvature. Together, these findings suggest a model for how cells may monitor aspects of their own shape to influence cell behavior.
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Affiliation(s)
- Hui Kang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Daniel J Lew
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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Verhey KJ, Yang W. Permeability barriers for generating a unique ciliary protein and lipid composition. Curr Opin Cell Biol 2016; 41:109-16. [PMID: 27232950 DOI: 10.1016/j.ceb.2016.05.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Revised: 05/04/2016] [Accepted: 05/10/2016] [Indexed: 01/08/2023]
Abstract
Cilia (and flagella) are microtubule-based protrusions that are found in single or multiple copies on the surface of most eukaryotic cells. Defects in cilia formation and/or function have now been correlated with an expanding spectrum of human genetic diseases termed ciliopathies. Recent work indicates that cilia are indeed a bona fide organelle with a unique protein and lipid content that enables specific cellular functions. Despite the physiological and clinical relevance of cilia, our understanding of how a unique protein and lipid composition is generated for this organelle remains poor. Here we review recent work on the mechanisms that determine the protein and lipid content, and thus the functional outputs, of this unique organelle.
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Affiliation(s)
- Kristen J Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
| | - Weidong Yang
- Department of Biology, Temple University, Philadelphia, PA 19122, USA
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Dash SN, Hakonen E, Ustinov J, Otonkoski T, Andersson O, Lehtonen S. sept7b is required for the differentiation of pancreatic endocrine progenitors. Sci Rep 2016; 6:24992. [PMID: 27114183 PMCID: PMC4845001 DOI: 10.1038/srep24992] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 04/05/2016] [Indexed: 12/14/2022] Open
Abstract
Protection or restoration of pancreatic β-cell mass as a therapeutic treatment for type 1 diabetes requires understanding of the mechanisms that drive the specification and development of pancreatic endocrine cells. Septins are filamentous small GTPases that function in the regulation of cell division, cytoskeletal organization and membrane remodeling, and are involved in various tissue-specific developmental processes. However, their role in pancreatic endocrine cell differentiation remains unknown. Here we show by functional manipulation techniques in transgenic zebrafish lines that suppression of sept7b, the zebrafish ortholog of human SEPT7, profoundly increases the number of endocrine progenitors but limits their differentiation, leading to reduction in β- and α-cell mass. Furthermore, we discovered that shh (sonic hedgehog) expression in the endoderm, essential for the development of pancreatic progenitors of the dorsal pancreatic bud, is absent in larvae depleted of sept7b. We also discovered that sept7b is important for the differentiation of ventral pancreatic bud-derived cells: sept7b-depleted larvae exhibit downregulation of Notch receptors notch1a and notch1b and show precocious differentiation of NeuroD-positive endocrine cells in the intrapancreatic duct and gut epithelium. Collectively, this study provides a novel insight into the development of pancreatic endocrine progenitors, revealing an essential role for sept7b in endocrine progenitor differentiation.
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Affiliation(s)
| | - Elina Hakonen
- Research Program for Molecular Neurology and Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland
| | - Jarkko Ustinov
- Research Program for Molecular Neurology and Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland
| | - Timo Otonkoski
- Research Program for Molecular Neurology and Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland
| | - Olov Andersson
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Sanna Lehtonen
- Department of Pathology, University of Helsinki, Helsinki, Finland
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Septin oligomerization regulates persistent expression of ErbB2/HER2 in gastric cancer cells. Biochem J 2016; 473:1703-18. [PMID: 27048593 DOI: 10.1042/bcj20160203] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 04/05/2016] [Indexed: 12/19/2022]
Abstract
Septins are a family of cytoskeletal GTP-binding proteins that assemble into membrane-associated hetero-oligomers and organize scaffolds for recruitment of cytosolic proteins or stabilization of membrane proteins. Septins have been implicated in a diverse range of cancers, including gastric cancer, but the underlying mechanisms remain unclear. The hypothesis tested here is that septins contribute to cancer by stabilizing the receptor tyrosine kinase ErbB2, an important target for cancer treatment. Septins and ErbB2 were highly over-expressed in gastric cancer cells. Immunoprecipitation followed by MS analysis identified ErbB2 as a septin-interacting protein. Knockdown of septin-2 or cell exposure to forchlorfenuron (FCF), a well-established inhibitor of septin oligomerization, decreased surface and total levels of ErbB2. These treatments had no effect on epidermal growth factor receptor (EGFR), emphasizing the specificity and functionality of the septin-ErbB2 interaction. The level of ubiquitylated ErbB2 at the plasma membrane was elevated in cells treated with FCF, which was accompanied by a decrease in co-localization of ErbB2 with septins at the membrane. Cathepsin B inhibitor, but not bafilomycin or lactacystin, prevented FCF-induced decrease in total ErbB2 by increasing accumulation of ubiquitylated ErbB2 in lysosomes. Therefore, septins protect ErbB2 from ubiquitylation, endocytosis and lysosomal degradation. The FCF-induced degradation pathway is distinct from and additive with the degradation induced by inhibiting ErbB2 chaperone Hsp90. These results identify septins as novel regulators of ErbB2 expression that contribute to the remarkable stabilization of the receptor at the plasma membrane of cancer cells and may provide a basis for the development of new ErbB2-targeting anti-cancer therapies.
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Takao D, Verhey KJ. Gated entry into the ciliary compartment. Cell Mol Life Sci 2016; 73:119-27. [PMID: 26472341 PMCID: PMC4959937 DOI: 10.1007/s00018-015-2058-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 09/28/2015] [Accepted: 09/29/2015] [Indexed: 11/26/2022]
Abstract
Cilia and flagella play important roles in cell motility and cell signaling. These functions require that the cilium establishes and maintains a unique lipid and protein composition. Recent work indicates that a specialized region at the base of the cilium, the transition zone, serves as both a barrier to entry and a gate for passage of select components. For at least some cytosolic proteins, the barrier and gate functions are provided by a ciliary pore complex (CPC) that shares molecular and mechanistic properties with nuclear gating. Specifically, nucleoporins of the CPC limit the diffusional entry of cytosolic proteins in a size-dependent manner and enable the active transport of large molecules and complexes via targeting signals, importins, and the small G protein Ran. For membrane proteins, the septin protein SEPT2 is part of the barrier to entry whereas the gating function is carried out and/or regulated by proteins associated with ciliary diseases (ciliopathies) such as nephronophthisis, Meckel–Gruber syndrome and Joubert syndrome. Here, we discuss the evidence behind these models of ciliary gating as well as the similarities to and differences from nuclear gating.
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Affiliation(s)
- Daisuke Takao
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl, Ann Arbor, MI 48109 USA
| | - Kristen J. Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl, Ann Arbor, MI 48109 USA
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Mick DU, Rodrigues RB, Leib RD, Adams CM, Chien AS, Gygi SP, Nachury MV. Proteomics of Primary Cilia by Proximity Labeling. Dev Cell 2015; 35:497-512. [PMID: 26585297 DOI: 10.1016/j.devcel.2015.10.015] [Citation(s) in RCA: 305] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 09/26/2015] [Accepted: 10/19/2015] [Indexed: 11/17/2022]
Abstract
While cilia are recognized as important signaling organelles, the extent of ciliary functions remains unknown because of difficulties in cataloguing proteins from mammalian primary cilia. We present a method that readily captures rapid snapshots of the ciliary proteome by selectively biotinylating ciliary proteins using a cilia-targeted proximity labeling enzyme (cilia-APEX). Besides identifying known ciliary proteins, cilia-APEX uncovered several ciliary signaling molecules. The kinases PKA, AMPK, and LKB1 were validated as bona fide ciliary proteins and PKA was found to regulate Hedgehog signaling in primary cilia. Furthermore, proteomics profiling of Ift27/Bbs19 mutant cilia correctly detected BBSome accumulation inside Ift27(-/-) cilia and revealed that β-arrestin 2 and the viral receptor CAR are candidate cargoes of the BBSome. This work demonstrates that proximity labeling can be applied to proteomics of non-membrane-enclosed organelles and suggests that proteomics profiling of cilia will enable a rapid and powerful characterization of ciliopathies.
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Affiliation(s)
- David U Mick
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA
| | - Rachel B Rodrigues
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ryan D Leib
- Stanford University Mass Spectrometry, Stanford University, Stanford, CA 94305, USA
| | - Christopher M Adams
- Stanford University Mass Spectrometry, Stanford University, Stanford, CA 94305, USA
| | - Allis S Chien
- Stanford University Mass Spectrometry, Stanford University, Stanford, CA 94305, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Maxence V Nachury
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA.
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Bizet AA, Becker-Heck A, Ryan R, Weber K, Filhol E, Krug P, Halbritter J, Delous M, Lasbennes MC, Linghu B, Oakeley EJ, Zarhrate M, Nitschké P, Garfa-Traore M, Serluca F, Yang F, Bouwmeester T, Pinson L, Cassuto E, Dubot P, Elshakhs NAS, Sahel JA, Salomon R, Drummond IA, Gubler MC, Antignac C, Chibout S, Szustakowski JD, Hildebrandt F, Lorentzen E, Sailer AW, Benmerah A, Saint-Mezard P, Saunier S. Mutations in TRAF3IP1/IFT54 reveal a new role for IFT proteins in microtubule stabilization. Nat Commun 2015; 6:8666. [PMID: 26487268 PMCID: PMC4617596 DOI: 10.1038/ncomms9666] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 09/17/2015] [Indexed: 01/20/2023] Open
Abstract
Ciliopathies are a large group of clinically and genetically heterogeneous disorders caused by defects in primary cilia. Here we identified mutations in TRAF3IP1 (TNF Receptor-Associated Factor Interacting Protein 1) in eight patients from five families with nephronophthisis (NPH) and retinal degeneration, two of the most common manifestations of ciliopathies. TRAF3IP1 encodes IFT54, a subunit of the IFT-B complex required for ciliogenesis. The identified mutations result in mild ciliary defects in patients but also reveal an unexpected role of IFT54 as a negative regulator of microtubule stability via MAP4 (microtubule-associated protein 4). Microtubule defects are associated with altered epithelialization/polarity in renal cells and with pronephric cysts and microphthalmia in zebrafish embryos. Our findings highlight the regulation of cytoplasmic microtubule dynamics as a role of the IFT54 protein beyond the cilium, contributing to the development of NPH-related ciliopathies.
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Affiliation(s)
- Albane A. Bizet
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Anita Becker-Heck
- Novartis Institutes for Biomedical Research, Basel CH-4002, Switzerland
| | - Rebecca Ryan
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Kristina Weber
- Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Emilie Filhol
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Pauline Krug
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Jan Halbritter
- Division of Nephrology, Department of Medicine, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
- Division of Nephrology, Department of Internal Medicine, University Clinic Leipzig, 04103 Leipzig, Germany
| | - Marion Delous
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | | | - Bolan Linghu
- Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139, USA
| | - Edward J. Oakeley
- Novartis Institutes for Biomedical Research, Basel CH-4002, Switzerland
| | - Mohammed Zarhrate
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
- Inserm UMR-1163, Genomic Core Facility, 75015 Paris, France
| | - Patrick Nitschké
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Bioinformatics Core Facility, 75015 Paris, France
| | - Meriem Garfa-Traore
- Cell Imaging Platform, INSERM US24 Structure Fédérative de recherche Necker, Paris Descartes Sorbonne Paris Cité University, 75015 Paris, France
| | - Fabrizio Serluca
- Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139, USA
| | - Fan Yang
- Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139, USA
| | - Tewis Bouwmeester
- Novartis Institutes for Biomedical Research, Basel CH-4002, Switzerland
| | - Lucile Pinson
- Department of Medical Genetic, Arnaud de Villeneuve University Health Center, 34090 Montpellier, France
| | - Elisabeth Cassuto
- Nephrology department, L'Archet II Hospital, Nice University Health Center, 06202 Nice, France
| | - Philippe Dubot
- Hemodialysis-Nephrology Department, William Morey Hospital, 71321 Chalon-sur-Saône, France
| | - Neveen A. Soliman Elshakhs
- Department of Pediatrics, Center of Pediatric Nephrology and Transplantation, Cairo University, Egyptian Group for Orphan Renal Diseases, 11956 Cairo, Egypt
| | - José A. Sahel
- INSERM U968, CNRS UMR 7210; Sorbonne Universités, Université Pierre et Marie Curie, UMR S968, Institut de la vision, 75012 Paris, France
- Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, INSERM, Direction de l'Hospitalisation et de l'Organisation des Soins, Centre d'Investigation Clinique 1423, 75012 Paris, France
| | - Rémi Salomon
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
- Assistance Publique—Hôpitaux de Paris, Pediatric Nephrologic department, Necker-Enfants Malades Hospital, 75015 Paris, France
| | - Iain A. Drummond
- Nephrology Division, Massachusetts General Hospital, Charlestown, Massachusetts 02114, USA
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Marie-Claire Gubler
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Corinne Antignac
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
- Assistance Publique-Hôpitaux de Paris, Department of Genetics, Necker-Enfants Malades Hospital, 75015 Paris, France
| | - Salahdine Chibout
- Novartis Institutes for Biomedical Research, Basel CH-4002, Switzerland
| | | | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Medicine, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Esben Lorentzen
- Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Andreas W. Sailer
- Novartis Institutes for Biomedical Research, Basel CH-4002, Switzerland
| | - Alexandre Benmerah
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | | | - Sophie Saunier
- Inserm UMR-1163, Laboratory of Hereditary Kidney Diseases, 75015 Paris, France
- Paris Descartes Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
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Gera N, Yang A, Holtzman TS, Lee SX, Wong ET, Swanson KD. Tumor treating fields perturb the localization of septins and cause aberrant mitotic exit. PLoS One 2015; 10:e0125269. [PMID: 26010837 PMCID: PMC4444126 DOI: 10.1371/journal.pone.0125269] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 03/23/2015] [Indexed: 01/04/2023] Open
Abstract
The anti-tumor effects of chemotherapy and radiation are thought to be mediated by triggering G1/S or G2/M cell cycle checkpoints, while spindle poisons, such as paclitaxel, block metaphase exit by initiating the spindle assembly checkpoint. In contrast, we have found that 150 kilohertz (kHz) alternating electric fields, also known as Tumor Treating Fields (TTFields), perturbed cells at the transition from metaphase to anaphase. Cells exposed to the TTFields during mitosis showed normal progression to this point, but exhibited uncontrolled membrane blebbing that coincided with metaphase exit. The ability of such alternating electric fields to affect cellular physiology is likely to be dependent on their interactions with proteins possessing high dipole moments. The mitotic Septin complex consisting of Septin 2, 6 and 7, possesses a high calculated dipole moment of 2711 Debyes (D) and plays a central role in positioning the cytokinetic cleavage furrow, and governing its contraction during ingression. We showed that during anaphase, TTFields inhibited Septin localization to the anaphase spindle midline and cytokinetic furrow, as well as its association with microtubules during cell attachment and spreading on fibronectin. After aberrant metaphase exit as a consequence of TTFields exposure, cells exhibited aberrant nuclear architecture and signs of cellular stress including an overall decrease in cellular proliferation, followed by apoptosis that was strongly influenced by the p53 mutational status. Thus, TTFields are able to diminish cell proliferation by specifically perturbing key proteins involved in cell division, leading to mitotic catastrophe and subsequent cell death.
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Affiliation(s)
- Nidhi Gera
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Aaron Yang
- Department of Neurology, Division of Neuro-Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Talia S. Holtzman
- Department of Neurology, Division of Neuro-Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Sze Xian Lee
- Department of Neurology, Division of Neuro-Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Eric T. Wong
- Department of Neurology, Division of Neuro-Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Kenneth D. Swanson
- Department of Neurology, Division of Neuro-Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
- * E-mail:
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The Carboxy-Terminal Tails of Septins Cdc11 and Shs1 Recruit Myosin-II Binding Factor Bni5 to the Bud Neck in Saccharomyces cerevisiae. Genetics 2015; 200:843-62. [PMID: 25971666 DOI: 10.1534/genetics.115.176503] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/08/2015] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Septins are a conserved family of GTP-binding proteins that form heterooctameric complexes that assemble into higher-order structures. In yeast, septin superstructure at the bud neck serves as a barrier to separate a daughter cell from its mother and as a scaffold to recruit the proteins that execute cytokinesis. However, how septins recruit specific factors has not been well characterized. In the accompanying article in this issue, (Finnigan et al. 2015), we demonstrated that the C-terminal extensions (CTEs) of the alternative terminal subunits of septin heterooctamers, Cdc11 and Shs1, share a role required for optimal septin function in vivo. Here we describe our use of unbiased genetic approaches (both selection of dosage suppressors and analysis of synthetic interactions) that pinpointed Bni5 as a protein that interacts with the CTEs of Cdc11 and Shs1. Furthermore, we used three independent methods-construction of chimeric proteins, noncovalent tethering mediated by a GFP-targeted nanobody, and imaging by fluorescence microscopy-to confirm that a physiologically important function of the CTEs of Cdc11 and Shs1 is optimizing recruitment of Bni5 and thereby ensuring efficient localization at the bud neck of Myo1, the type II myosin of the actomyosin contractile ring.Related article in GENETICS Finnigan, G. C. et al., 2015 Comprehensive Genetic Analysis of Paralogous Terminal Septin Subunits Shs1 and Cdc11 in Saccharomyces cerevisiae. Genetics 200: 841-861.
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Abstract
Septins are GTP-binding proteins that form filaments and higher-order structures on the cell cortex of eukaryotic cells and associate with actin and microtubule cytoskeletal networks. When assembled, septins coordinate cell division and contribute to cell polarity maintenance and membrane remodeling. These functions manifest themselves via scaffolding of cytosolic proteins and cytoskeletal networks to specific locations on membranes and by forming diffusional barriers that restrict lateral diffusion of proteins embedded in membranes. Notably, many neurodegenerative diseases and cancers have been characterized as having misregulated septins, suggesting that their functions are relevant to diverse diseases. Despite the importance of septins, little is known about what features of the plasma membrane influence septin recruitment and alternatively, how septins influence plasma membrane properties. Septins have been localized to the cell cortex at the base of cilia, the mother-bud neck of yeast, and branch points of filamentous fungi and dendritic spines, in cleavage furrows, and in retracting membrane protrusions in mammalian cells. These sites all possess some degree of curvature and are likely composed of distinct lipid pools. Depending on the context, septins may act alone or in concert with other cytoskeletal elements to influence and sense membrane properties. The degree to which septins react to and/or induce changes in shape and lipid composition are discussed here. As septins are an essential player in basic biology and disease, understanding the interplay between septins and the plasma membrane is critical and may yield new and unexpected functions.
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Affiliation(s)
- Andrew A Bridges
- From the Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
| | - Amy S Gladfelter
- From the Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
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Benmerah A, Durand B, Giles RH, Harris T, Kohl L, Laclef C, Meilhac SM, Mitchison HM, Pedersen LB, Roepman R, Swoboda P, Ueffing M, Bastin P. The more we know, the more we have to discover: an exciting future for understanding cilia and ciliopathies. Cilia 2015; 4:5. [PMID: 25974046 PMCID: PMC4378380 DOI: 10.1186/s13630-015-0014-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 02/23/2015] [Indexed: 11/10/2022] Open
Abstract
The Cilia 2014 conference was organised by four European networks: the Ciliopathy Alliance, the Groupement de Recherche CIL, the Nordic Cilia and Centrosome Network and the EU FP7 programme SYSCILIA. More than 400 delegates from 27 countries gathered at the Institut Pasteur conference centre in Paris, including 30 patients and patient representatives. The meeting offered a unique opportunity for exchange between different scientific and medical communities. Major highlights included new discoveries about the roles of motile and immotile cilia during development and homeostasis, the mechanism of cilium construction, as well as progress in diagnosis and possible treatment of ciliopathies. The contributions to the cilia field of flagellated infectious eukaryotes and of systems biology were also presented.
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Affiliation(s)
- Alexandre Benmerah
- INSERM U1163, Laboratoire des Maladies Rénales Héréditaires, 24 boulevard du Montparnasse, 75015 Paris, France ; Institut Imagine, Université Paris Descartes-Sorbonne Paris Cité, 24 boulevard du Montparnasse, 75015 Paris, France
| | - Bénédicte Durand
- Centre de Génétique et de Physiologie Moléculaires et Cellulaires, CNRS UMR 5534, Université Claude Bernard Lyon 1, 16 rue Dubois, Villeurbanne, Lyon, F69622 France
| | - Rachel H Giles
- Department of Nephrology, University Medical Centre Utrecht, 100 Heidelberglaan, Utrecht, 3584CX The Netherlands
| | - Tess Harris
- The Ciliopathy Alliance, 91 Royal College St, NW1 0SE, London
| | - Linda Kohl
- UMR7245 CNRS/MNHN, Muséum National d'Histoire Naturelle, 57 rue Cuvier, 75005 Paris, France
| | - Christine Laclef
- Developmental Biology Laboratory UMR7622, UPMC Univ Paris 06, Sorbonne Université, 9 Quai Saint Bernard, F-75005 Paris, France ; Developmental Biology Laboratory UMR7622, CNRS, Institut de Biologie Paris Seine (IBPS), 9 Quai Saint Bernard, F-75005 Paris, France ; INSERM, ERL1156, 9 Quai Saint Bernard, F-75005 Paris, France
| | - Sigolène M Meilhac
- Department of Developmental and Stem Cell Biology, Institut Pasteur, 25 rue du docteur Roux, 75015 Paris, France ; CNRS URA2578, 25 rue du docteur Roux, 75015 Paris, France
| | - Hannah M Mitchison
- Genetics and Genomic Medicine, Institute of Child Health, University College London, 30 Guilford Street, London, WC1N 1EH UK
| | - Lotte B Pedersen
- Department of Biology, University of Copenhagen, Universitetsparken 13, 2100 Copenhagen, OE Denmark
| | - Ronald Roepman
- Department of Human Genetics, Radboud University Medical Center, Geert Grooteplein 25, P.O. Box 9101, 6525 Nijmegen, GA The Netherlands
| | - Peter Swoboda
- Department of Biosciences and Nutrition, Karolinska Institute, Hälsovägen 7, S-141 83 Huddinge, Sweden
| | - Marius Ueffing
- Institute for Ophthalmic Research, University of Tübingen, PO 2669, D-72016 Tübingen, Germany ; Research Unit of Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health, D-85758 Neuherberg, Germany
| | - Philippe Bastin
- Trypanosome Cell Biology Unit, Institut Pasteur and INSERM U1201, 25 rue du Docteur Roux, 75015 Paris, France
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74
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Trimble WS, Grinstein S. Barriers to the free diffusion of proteins and lipids in the plasma membrane. ACTA ACUST UNITED AC 2015; 208:259-71. [PMID: 25646084 PMCID: PMC4315255 DOI: 10.1083/jcb.201410071] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Biological membranes segregate into specialized functional domains of distinct composition, which can persist for the entire life of the cell. How separation of their lipid and (glyco)protein components is generated and maintained is not well understood, but the existence of diffusional barriers has been proposed. Remarkably, the physical nature of such barriers and the manner whereby they impede the free diffusion of molecules in the plane of the membrane has rarely been studied in depth. Moreover, alternative mechanisms capable of generating membrane inhomogeneity are often disregarded. Here we describe prototypical biological systems where membrane segregation has been amply documented and discuss the role of diffusional barriers and other processes in the generation and maintenance of their structural and functional compartmentalization.
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Affiliation(s)
- William S Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Sergio Grinstein
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario M5C 1N8, Canada
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75
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Menon MB, Gaestel M. Sep(t)arate or not – how some cells take septin-independent routes through cytokinesis. J Cell Sci 2015; 128:1877-86. [PMID: 25690008 DOI: 10.1242/jcs.164830] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Cytokinesis is the final step of cell division, and is a process that requires a precisely coordinated molecular machinery to fully separate the cytoplasm of the parent cell and to establish the intact outer cell barrier of the daughter cells. Among various cytoskeletal proteins involved, septins are known to be essential mediators of cytokinesis. In this Commentary, we present recent observations that specific cell divisions can proceed in the absence of the core mammalian septin SEPT7 and its Drosophila homolog Peanut (Pnut) and that thus challenge the view that septins have an essential role in cytokinesis. In the pnut mutant neuroepithelium, orthogonal cell divisions are successfully completed. Similarly, in the mouse, Sept7-null mutant early embryonic cells and, more importantly, planktonically growing adult hematopoietic cells undergo productive proliferation. Hence, as discussed here, mechanisms must exist that compensate for the lack of SEPT7 and the other core septins in a cell-type-specific manner. Despite there being crucial non-canonical immune-relevant functions of septins, septin depletion is well tolerated by the hematopoietic system. Thus differential targeting of cytokinesis could form the basis for more specific anti-proliferative therapies to combat malignancies arising from cell types that require septins for cytokinesis, such as carcinomas and sarcomas, without impairing hematopoiesis that is less dependent on septin.
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Affiliation(s)
- Manoj B Menon
- Institute of Physiological Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Matthias Gaestel
- Institute of Physiological Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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76
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Dacheux D, Roger B, Bosc C, Landrein N, Roche E, Chansel L, Trian T, Andrieux A, Papaxanthos-Roche A, Marthan R, Robinson DR, Bonhivers M. Human FAM154A (SAXO1) is a microtubule-stabilizing protein specific to cilia and related structures. J Cell Sci 2015; 128:1294-307. [PMID: 25673876 DOI: 10.1242/jcs.155143] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cilia and flagella are microtubule-based organelles present at the surface of most cells, ranging from protozoa to vertebrates, in which these structures are implicated in processes from morphogenesis to cell motility. In vertebrate neurons, microtubule-associated MAP6 proteins stabilize cold-resistant microtubules through their Mn and Mc modules, and play a role in synaptic plasticity. Although centrioles, cilia and flagella have cold-stable microtubules, MAP6 proteins have not been identified in these organelles, suggesting that additional proteins support this role in these structures. Here, we characterize human FAM154A (hereafter referred to as hSAXO1) as the first human member of a widely conserved family of MAP6-related proteins specific to centrioles and cilium microtubules. Our data demonstrate that hSAXO1 binds specifically to centriole and cilium microtubules. We identify, in vivo and in vitro, hSAXO1 Mn modules as responsible for microtubule binding and stabilization as well as being necessary for ciliary localization. Finally, overexpression and knockdown studies show that hSAXO1 modulates axoneme length. Taken together, our findings suggest a fine regulation of hSAXO1 localization and important roles in cilium biogenesis and function.
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Affiliation(s)
- Denis Dacheux
- University Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France Institut Polytechnique de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Benoit Roger
- University Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Christophe Bosc
- INSERM, Centre de Recherche U836, F-38000, Grenoble, France University Grenoble Alpes, Grenoble Institut des Neurosciences, F-38000, Grenoble, France
| | - Nicolas Landrein
- University Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Emmanuel Roche
- University Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Lucie Chansel
- CHU de Bordeaux, Centre Aliénor d'Aquitaine, Laboratoire de Biologie de la Reproduction, F-33000 Bordeaux, France
| | - Thomas Trian
- University Bordeaux, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, F-33000 Bordeaux, France INSERM, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, F-33000 Bordeaux, France
| | - Annie Andrieux
- INSERM, Centre de Recherche U836, F-38000, Grenoble, France University Grenoble Alpes, Grenoble Institut des Neurosciences, F-38000, Grenoble, France CEA, Institut de Recherches en Technologies et Sciences pour le Vivant, GPC, F-38000 Grenoble, France
| | - Aline Papaxanthos-Roche
- CHU de Bordeaux, Centre Aliénor d'Aquitaine, Laboratoire de Biologie de la Reproduction, F-33000 Bordeaux, France
| | - Roger Marthan
- University Bordeaux, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, F-33000 Bordeaux, France INSERM, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, F-33000 Bordeaux, France
| | - Derrick R Robinson
- University Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Mélanie Bonhivers
- University Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
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77
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Tokhtaeva E, Capri J, Marcus EA, Whitelegge JP, Khuzakhmetova V, Bukharaeva E, Deiss-Yehiely N, Dada LA, Sachs G, Fernandez-Salas E, Vagin O. Septin dynamics are essential for exocytosis. J Biol Chem 2015; 290:5280-97. [PMID: 25575596 DOI: 10.1074/jbc.m114.616201] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Septins are a family of 14 cytoskeletal proteins that dynamically form hetero-oligomers and organize membrane microdomains for protein complexes. The previously reported interactions with SNARE proteins suggested the involvement of septins in exocytosis. However, the contradictory results of up- or down-regulation of septin-5 in various cells and mouse models or septin-4 in mice suggested either an inhibitory or a stimulatory role for these septins in exocytosis. The involvement of the ubiquitously expressed septin-2 or general septin polymerization in exocytosis has not been explored to date. Here, by nano-LC with tandem MS and immunoblot analyses of the septin-2 interactome in mouse brain, we identified not only SNARE proteins but also Munc-18-1 (stabilizes assembled SNARE complexes), N-ethylmaleimide-sensitive factor (NSF) (disassembles SNARE complexes after each membrane fusion event), and the chaperones Hsc70 and synucleins (maintain functional conformation of SNARE proteins after complex disassembly). Importantly, α-soluble NSF attachment protein (SNAP), the adaptor protein that mediates NSF binding to the SNARE complex, did not interact with septin-2, indicating that septins undergo reorganization during each exocytosis cycle. Partial depletion of septin-2 by siRNA or impairment of septin dynamics by forchlorfenuron inhibited constitutive and stimulated exocytosis of secreted and transmembrane proteins in various cell types. Forchlorfenuron impaired the interaction between SNAP-25 and its chaperone Hsc70, decreasing SNAP-25 levels in cultured neuroendocrine cells, and inhibited both spontaneous and stimulated acetylcholine secretion in mouse motor neurons. The results demonstrate a stimulatory role of septin-2 and the dynamic reorganization of septin oligomers in exocytosis.
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Affiliation(s)
- Elmira Tokhtaeva
- From the Departments of Physiology and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Joe Capri
- The Neuropsychiatric Institute-Semel Institute, Pasarow Mass Spectrometry Laboratory, UCLA, Los Angeles, California 90024
| | - Elizabeth A Marcus
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073, Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Julian P Whitelegge
- The Neuropsychiatric Institute-Semel Institute, Pasarow Mass Spectrometry Laboratory, UCLA, Los Angeles, California 90024
| | - Venera Khuzakhmetova
- Kazan Institute of Biochemistry and Biophysics, Kazan Scientific Center of the Russian Academy of Sciences, Kazan 420111, Russia, Kazan Federal University, Kazan 420008, Russia
| | - Ellya Bukharaeva
- Kazan Institute of Biochemistry and Biophysics, Kazan Scientific Center of the Russian Academy of Sciences, Kazan 420111, Russia, Kazan Federal University, Kazan 420008, Russia
| | - Nimrod Deiss-Yehiely
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, and
| | - Laura A Dada
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, and
| | - George Sachs
- From the Departments of Physiology and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Ester Fernandez-Salas
- Department of Pathology, School of Medicine, University of Michigan, Ann Arbor, Michigan 48109
| | - Olga Vagin
- From the Departments of Physiology and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073,
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78
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Zahnleiter D, Hauer NN, Kessler K, Uebe S, Sugano Y, Neuhauss SC, Giessl A, Ekici AB, Blessing H, Sticht H, Dörr HG, Reis A, Thiel CT. MAP4-Dependent Regulation of Microtubule Formation Affects Centrosome, Cilia, and Golgi Architecture as a Central Mechanism in Growth Regulation. Hum Mutat 2014; 36:87-97. [DOI: 10.1002/humu.22711] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 10/01/2014] [Indexed: 12/30/2022]
Affiliation(s)
- Diana Zahnleiter
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Nadine N. Hauer
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Kristin Kessler
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Steffen Uebe
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Yuya Sugano
- Institute of Molecular Life Sciences; University of Zurich; Zurich Switzerland
| | | | - Andreas Giessl
- Animal Physiology; Friedrich-Alexander Universität Erlangen-Nürnberg; Erlangen Germany
| | - Arif B. Ekici
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Holger Blessing
- Department of Pediatrics and Adolescent Medicine; Friedrich-Alexander Universität Erlangen-Nürnberg; Erlangen Germany
| | - Heinrich Sticht
- Institute of Biochemistry; Friedrich-Alexander Universität Erlangen-Nürnberg; Erlangen Germany
| | - Helmuth-Günther Dörr
- Department of Pediatrics and Adolescent Medicine; Friedrich-Alexander Universität Erlangen-Nürnberg; Erlangen Germany
| | - André Reis
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Christian T. Thiel
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
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79
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Fung KYY, Dai L, Trimble WS. Cell and molecular biology of septins. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 310:289-339. [PMID: 24725429 DOI: 10.1016/b978-0-12-800180-6.00007-4] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Septins are a family of GTP-binding proteins that assemble into cytoskeletal filaments. Unlike other cytoskeletal components, septins form ordered arrays of defined stoichiometry that can polymerize into long filaments and bundle laterally. Septins associate directly with membranes and have been implicated in providing membrane stability and serving as diffusion barriers for membrane proteins. In addition, septins bind other proteins and have been shown to function as multimolecular scaffolds by recruiting components of signaling pathways. Remarkably, septins participate in a spectrum of cellular processes including cytokinesis, ciliogenesis, cell migration, polarity, and cell-pathogen interactions. Given their breadth of functions, it is not surprising that septin abnormalities have also been linked to human diseases. In this review, we discuss the current knowledge of septin structure, assembly and function, and discuss these in the context of human disease.
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Affiliation(s)
- Karen Y Y Fung
- Cell Biology Program, Hospital for Sick Children, Toronto, Canada; Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Lu Dai
- Cell Biology Program, Hospital for Sick Children, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada
| | - William S Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, Canada; Department of Biochemistry, University of Toronto, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada.
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80
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Dolat L, Hu Q, Spiliotis ET. Septin functions in organ system physiology and pathology. Biol Chem 2014; 395:123-41. [PMID: 24114910 DOI: 10.1515/hsz-2013-0233] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 10/08/2013] [Indexed: 02/07/2023]
Abstract
Human septins comprise a family of 13 genes that encode for >30 protein isoforms with ubiquitous and tissue-specific expressions. Septins are GTP-binding proteins that assemble into higher-order oligomers and filamentous polymers, which associate with cell membranes and the cytoskeleton. In the last decade, much progress has been made in understanding the biochemical properties and cell biological functions of septins. In parallel, a growing number of studies show that septins play important roles for the development and physiology of specific tissues and organs. Here, we review the expression and function of septins in the cardiovascular, immune, nervous, urinary, digestive, respiratory, endocrine, reproductive, and integumentary organ systems. Furthermore, we discuss how the tissue-specific functions of septins relate to the pathology of human diseases that arise from aberrations in septin expression.
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81
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Fliegauf M, Kahle A, Häffner K, Zieger B. Distinct localization of septin proteins to ciliary sub-compartments in airway epithelial cells. Biol Chem 2014; 395:151-6. [PMID: 24317785 DOI: 10.1515/hsz-2013-0252] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 12/02/2013] [Indexed: 11/15/2022]
Abstract
Mucociliary clearance of the airways is accomplished by cilia-mediated laminar mucus flow along the planar epithelial surface. Maintenance of the highly specific architecture of the ciliated airway epithelium with columnar-shaped epithelial cells and tightening of the epithelial barrier is mainly attributed to the F-actin cytoskeleton. Recently, members of the highly conserved family of septin proteins have been shown to play crucial roles in ciliated tissue. These GTP-binding proteins form hetero-oligomeric complexes and assemble higher-order cytoskeletal structures such as filaments, bundles and ring-like structures such as a membrane diffusion barrier at the ciliary base. Here we analyzed the subcellular and sub-ciliary localization of various septin proteins by immunofluorescence imaging of airway epithelial cells. In addition to cytoplasmic localization we found that septins are either enriched at the apical cell cortex including the ciliary bases (septin-2, -4, -6, and -7), or show axonemal staining (septin-2, -7, -9 and -11) or specifically localize to ciliary sub-compartments (septin-8 and -9). The distinct localization of septins suggests structural functions as cytoskeletal components and as elements of the mechanical barrier at the apical cell cortex. Furthermore, the tight association of septin-8 and -9 with the ciliary compartment indicates a possible involvement in cilia-specific functions and cilia-related diseases.
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82
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Primary cilium-associated genes mediate bone marrow stromal cell response to hypoxia. Stem Cell Res 2014; 13:284-99. [PMID: 25171775 DOI: 10.1016/j.scr.2014.06.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 06/27/2014] [Accepted: 06/28/2014] [Indexed: 12/26/2022] Open
Abstract
Currently there is intense interest in using mesenchymal stem cells (MSC) for therapeutic interventions in many diseases and conditions. To accelerate the therapeutic use of stem cells we must understand how they sense their environment. Primary cilia are an extracellular sensory organelle present on most growth arrested cells that transduce information about the cellular environment into cells, triggering signaling cascades that have profound effects on development, cell cycle, proliferation, differentiation and migration. Migrating cells likely encounter differing oxygen tensions, therefore we investigated the effect of oxygen tension on cilia. Using bone marrow stromal cells (BMSCs, also known as bone marrow-derived mesenchymal stem cells) we found that oxygen tension significantly affected the length of cilia in primary BMSCs. Chronic exposure to hypoxia specifically down-regulated genes involved in hedgehog signaling and re-localized the Smo and Gli2 proteins to cilia. Investigating the effects of chemotactic migration on cilia, we observed significantly longer cilia in migrating cells which was again, strongly influenced by oxygen tension. Finally, using computational modeling we identified links between migration and ciliation signaling pathways, characterizing the novel role of HSP90 and PI3K signaling in regulating BMSC cilia length. These findings enhance our current understanding of BMSC adaptions to hypoxia and advance our knowledge of BMSC biology and cilia regulation.
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83
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In silico docking of forchlorfenuron (FCF) to septins suggests that FCF interferes with GTP binding. PLoS One 2014; 9:e96390. [PMID: 24787956 PMCID: PMC4008567 DOI: 10.1371/journal.pone.0096390] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 04/07/2014] [Indexed: 11/19/2022] Open
Abstract
Septins are GTP-binding proteins that form cytoskeleton-like filaments, which are essential for many functions in eukaryotic organisms. Small molecule compounds that disrupt septin filament assembly are valuable tools for dissecting septin functions with high temporal control. To date, forchlorfenuron (FCF) is the only compound known to affect septin assembly and functions. FCF dampens the dynamics of septin assembly inducing the formation of enlarged stable polymers, but the underlying mechanism of action is unknown. To investigate how FCF binds and affects septins, we performed in silico simulations of FCF docking to all available crystal structures of septins. Docking of FCF with SEPT2 and SEPT3 indicated that FCF interacts preferentially with the nucleotide-binding pockets of septins. Strikingly, FCF is predicted to form hydrogen bonds with residues involved in GDP-binding, mimicking nucleotide binding. FCF docking with the structure of SEPT2-GppNHp, a nonhydrolyzable GTP analog, and SEPT7 showed that FCF may assume two alternative non-overlapping conformations deeply into and on the outer side of the nucleotide-binding pocket. Surprisingly, FCF was predicted to interact with the P-loop Walker A motif GxxxxGKS/T, which binds the phosphates of GTP, and the GTP specificity motif AKAD, which interacts with the guanine base of GTP, and highly conserved amino acids including a threonine, which is critical for GTP hydrolysis. Thus, in silico FCF exhibits a conserved mechanism of binding, interacting with septin signature motifs and residues involved in GTP binding and hydrolysis. Taken together, our results suggest that FCF stabilizes septins by locking them into a conformation that mimics a nucleotide-bound state, preventing further GTP binding and hydrolysis. Overall, this study provides the first insight into how FCF may bind and stabilize septins, and offers a blueprint for the rational design of FCF derivatives that could target septins with higher affinity and specificity.
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84
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Bauß K, Knapp B, Jores P, Roepman R, Kremer H, Wijk EV, Märker T, Wolfrum U. Phosphorylation of the Usher syndrome 1G protein SANS controls Magi2-mediated endocytosis. Hum Mol Genet 2014; 23:3923-42. [PMID: 24608321 DOI: 10.1093/hmg/ddu104] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The human Usher syndrome (USH) is a complex ciliopathy with at least 12 chromosomal loci assigned to three clinical subtypes, USH1-3. The heterogeneous USH proteins are organized into protein networks. Here, we identified Magi2 (membrane-associated guanylate kinase inverted-2) as a new component of the USH protein interactome, binding to the multifunctional scaffold protein SANS (USH1G). We showed that the SANS-Magi2 complex assembly is regulated by the phosphorylation of an internal PDZ-binding motif in the sterile alpha motif domain of SANS by the protein kinase CK2. We affirmed Magi2's role in receptor-mediated, clathrin-dependent endocytosis and showed that phosphorylated SANS tightly regulates Magi2-mediated endocytosis. Specific depletions by RNAi revealed that SANS and Magi2-mediated endocytosis regulates aspects of ciliogenesis. Furthermore, we demonstrated the localization of the SANS-Magi2 complex in the periciliary membrane complex facing the ciliary pocket of retinal photoreceptor cells in situ. Our data suggest that endocytotic processes may not only contribute to photoreceptor cell homeostasis but also counterbalance the periciliary membrane delivery accompanying the exocytosis processes for the cargo vesicle delivery. In USH1G patients, mutations in SANS eliminate Magi2 binding and thereby deregulate endocytosis, lead to defective ciliary transport modules and ultimately disrupt photoreceptor cell function inducing retinal degeneration.
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Affiliation(s)
- Katharina Bauß
- Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany
| | - Barbara Knapp
- Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany
| | - Pia Jores
- Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany
| | - Ronald Roepman
- Department of Human Genetics, Institute for Genetic and Metabolic Disease, Nijmegen Centre for Molecular Life Sciences and
| | - Hannie Kremer
- Department of Human Genetics, Department of Otorhinolaryngology, Head and Neck Surgery, Nijmegen Centre for Molecular Life Sciences and Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre, 6500 HB, Nijmegen, Netherlands
| | - Erwin V Wijk
- Department of Human Genetics, Department of Otorhinolaryngology, Head and Neck Surgery, Nijmegen Centre for Molecular Life Sciences and Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre, 6500 HB, Nijmegen, Netherlands
| | - Tina Märker
- Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany
| | - Uwe Wolfrum
- Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany
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85
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Dash SN, Lehtonen E, Wasik AA, Schepis A, Paavola J, Panula P, Nelson WJ, Lehtonen S. Sept7b is essential for pronephric function and development of left-right asymmetry in zebrafish embryogenesis. J Cell Sci 2014; 127:1476-86. [PMID: 24496452 DOI: 10.1242/jcs.138495] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The conserved septin family of filamentous small GTPases plays important roles in mitosis, cell migration and cell morphogenesis by forming scaffolds and diffusion barriers. Recent studies in cultured cells in vitro indicate that a septin complex of septin 2, 7 and 9 is required for ciliogenesis and cilia function, but septin function in ciliogenesis in vertebrate organs in vivo is not understood. We show that sept7b is expressed in ciliated cells in different tissues during early zebrafish development. Knockdown of sept7b by using morpholino antisense oligonucleotides caused misorientation of basal bodies and cilia, reduction of apical actin and the shortening of motile cilia in Kupffer's vesicle and pronephric tubules. This resulted in pericardial and yolk sac edema, body axis curvature and hydrocephaly. Notably, in sept7b morphants we detected strong left-right asymmetry defects in the heart and lateral plate mesoderm (situs inversus), reduced fluid flow in the kidney, the formation of kidney cysts and loss of glomerular filtration barrier function. Thus, sept7b is essential during zebrafish development for pronephric function and ciliogenesis, and loss of expression of sept7b results in defects that resemble human ciliopathies.
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Affiliation(s)
- Surjya Narayan Dash
- University of Helsinki, Haartman Institute, Department of Pathology, Haartmaninkatu 3, 00290 Helsinki, Finland
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86
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Mostowy S, Bi E, Füchtbauer EM, Goryachev AB, Montagna C, Nagata KI, Trimble WS, Werner HB, Yao X, Zieger B, Spiliotis ET. Highlight: the 5th International Workshop on Septin Biology. Biol Chem 2014; 395:119-21. [PMID: 24334412 DOI: 10.1515/hsz-2013-0291] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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87
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Sept6 is required for ciliogenesis in Kupffer's vesicle, the pronephros, and the neural tube during early embryonic development. Mol Cell Biol 2014; 34:1310-21. [PMID: 24469395 DOI: 10.1128/mcb.01409-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Septins are conserved filament-forming GTP-binding proteins that act as cellular scaffolds or diffusion barriers in a number of cellular processes. However, the role of septins in vertebrate development remains relatively obscure. Here, we show that zebrafish septin 6 (sept6) is first expressed in the notochord and then in nearly all of the ciliary organs, including Kupffer's vesicle (KV), the pronephros, eye, olfactory bulb, and neural tube. Knockdown of sept6 in zebrafish embryos results in reduced numbers and length of cilia in KV. Consequently, cilium-related functions, such as the left-right patterning of internal organs and nodal/spaw signaling, are compromised. Knockdown of sept6 also results in aberrant cilium formation in the pronephros and neural tube, leading to cilium-related defects in pronephros development and Sonic hedgehog (Shh) signaling. We further demonstrate that SEPT6 associates with acetylated α-tubulin in vivo and localizes along the axoneme in the cilia of zebrafish pronephric duct cells as well as cultured ZF4 cells. Our study reveals a novel role of sept6 in ciliogenesis during early embryonic development in zebrafish.
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88
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Higher-order septin assembly is driven by GTP-promoted conformational changes: evidence from unbiased mutational analysis in Saccharomyces cerevisiae. Genetics 2014; 196:711-27. [PMID: 24398420 PMCID: PMC3948802 DOI: 10.1534/genetics.114.161182] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Septin proteins bind GTP and heterooligomerize into filaments with conserved functions across a wide range of eukaryotes. Most septins hydrolyze GTP, altering the oligomerization interfaces; yet mutations designed to abolish nucleotide binding or hydrolysis by yeast septins perturb function only at high temperatures. Here, we apply an unbiased mutational approach to this problem. Mutations causing defects at high temperature mapped exclusively to the oligomerization interface encompassing the GTP-binding pocket, or to the pocket itself. Strikingly, cold-sensitive defects arise when certain of these same mutations are coexpressed with a wild-type allele, suggestive of a novel mode of dominance involving incompatibility between mutant and wild-type molecules at the septin–septin interfaces that mediate filament polymerization. A different cold-sensitive mutant harbors a substitution in an unstudied but highly conserved region of the septin Cdc12. A homologous domain in the small GTPase Ran allosterically regulates GTP-binding domain conformations, pointing to a possible new functional domain in some septins. Finally, we identify a mutation in septin Cdc3 that restores the high-temperature assembly competence of a mutant allele of septin Cdc10, likely by adopting a conformation more compatible with nucleotide-free Cdc10. Taken together, our findings demonstrate that GTP binding and hydrolysis promote, but are not required for, one-time events—presumably oligomerization-associated conformational changes—during assembly of the building blocks of septin filaments. Restrictive temperatures impose conformational constraints on mutant septin proteins, preventing new assembly and in certain cases destabilizing existing assemblies. These insights from yeast relate directly to disease-causing mutations in human septins.
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89
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Abstract
The primary cilium that protrudes from the plasma membrane of many eukaryotic cell types is very much a cellular organelle in its own right. Its unique membrane and luminal composition is effectively compartmentalized by diffusion barrier at its base, known as the transition zone. Recent works have now shed light on the molecular components of this diffusion barrier, and revealed intriguing functional similarities with other better characterized cellular barriers.
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Affiliation(s)
- Yi Shan Lim
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University Health System , MD6, 14 Medical Drive , Singapore
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90
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Bonilha VL. Retinal pigment epithelium (RPE) cytoskeleton in vivo and in vitro. Exp Eye Res 2013; 126:38-45. [PMID: 24090540 DOI: 10.1016/j.exer.2013.09.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/18/2013] [Accepted: 09/19/2013] [Indexed: 12/31/2022]
Abstract
The retinal pigment epithelium (RPE) constitutes a monolayer of cuboidal cells that interact apically with the interphotoreceptor matrix (IPM) and outer segments of the photoreceptor cells and basally with the subjacent Bruch's membrane. This highly polarized structure is maintained by the cytoskeleton of individual cells and their interactions at the basolateral junctional complexes that stabilize this epithelial structure. This RPE complex network of filaments, tubules and associated proteins is modeled by the cellular environment, the RPE intercellular interactions, and by its interactions with the extracellular matrix. This is a review of the key features of the RPE cytoskeleton in vivo and in vitro.
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Affiliation(s)
- Vera L Bonilha
- Department of Ophthalmic Research, The Cole Eye Institute, Cleveland Clinic Lerner College of Medicine, 9500 Euclid Avenue i31, Cleveland, OH 44195, USA.
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91
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Wang S, Dong Z. Primary cilia and kidney injury: current research status and future perspectives. Am J Physiol Renal Physiol 2013; 305:F1085-98. [PMID: 23904226 DOI: 10.1152/ajprenal.00399.2013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cilia, membrane-enclosed organelles protruding from the apical side of cells, can be divided into two classes: motile and primary cilia. During the past decades, motile cilia have been intensively studied. However, it was not until the 1990s that people began to realize the importance of primary cilia as cellular-specific sensors, particularly in kidney tubular epithelial cells. Furthermore, accumulating evidence indicates that primary cilia may be involved in the regulation of cell proliferation, differentiation, apoptosis, and planar cell polarity. Many signaling pathways, such as Wnt, Notch, Hedgehog, and mammalian target of rapamycin, have been located to the primary cilia. Thus primary cilia have been regarded as a hub that integrates signals from the extracellular environment. More importantly, dysfunction of this organelle may contribute to the pathogenesis of a large spectrum of human genetic diseases, named ciliopathies. The significance of primary cilia in acquired human diseases such as hypertension and diabetes has gradually drawn attention. Interestingly, recent reports disclosed that cilia length varies during kidney injury, and shortening of cilia enhances the sensitivity of epithelial cells to injury cues. This review briefly summarizes the current status of cilia research and explores the potential mechanisms of cilia-length changes during kidney injury as well as provides some thoughts to allure more insightful ideas and promotes the further study of primary cilia in the context of kidney injury.
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Affiliation(s)
- Shixuan Wang
- Dept. of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912.
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92
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Ghossoub R, Hu Q, Failler M, Rouyez MC, Spitzbarth B, Mostowy S, Wolfrum U, Saunier S, Cossart P, Nelson WJ, Benmerah A. Septins 2, 7 and 9 and MAP4 colocalize along the axoneme in the primary cilium and control ciliary length. Development 2013. [DOI: 10.1242/dev.100073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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93
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Activation loop phosphorylation of a protein kinase is a molecular marker of organelle size that dynamically reports flagellar length. Proc Natl Acad Sci U S A 2013; 110:12337-42. [PMID: 23836633 DOI: 10.1073/pnas.1302364110] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Specification of organelle size is crucial for cell function, yet we know little about the molecular mechanisms that report and regulate organelle growth and steady-state dimensions. The biflagellated green alga Chlamydomonas requires continuous-length feedback to integrate the multiple events that support flagellar assembly and disassembly and at the same time maintain the sensory and motility functions of the organelle. Although several length mutants have been characterized, the requisite molecular reporter of length has not been identified. Previously, we showed that depletion of Chlamydomonas aurora-like protein kinase CALK inhibited flagellar disassembly and that a gel-shift-associated phosphorylation of CALK marked half-length flagella during flagellar assembly. Here, we show that phosphorylation of CALK on T193, a consensus phosphorylation site on the activation loop required for kinase activity, is distinct from the gel-shift-associated phosphorylation and is triggered when flagellar shortening is induced, thereby implicating CALK protein kinase activity in the shortening arm of length control. Moreover, CALK phosphorylation on T193 is dynamically related to flagellar length. It is reduced in cells with short flagella, elevated in the long flagella mutant, lf4, and dynamically tracks length during both flagellar assembly and flagellar disassembly in WT, but not in lf4. Thus, phosphorylation of CALK in its activation loop is implicated in the disassembly arm of a length feedback mechanism and is a continuous and dynamic molecular marker of flagellar length during both assembly and disassembly.
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