1
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Marquardt J, Chen X, Bi E. Reciprocal regulation by Elm1 and Gin4 controls septin hourglass assembly and remodeling. J Cell Biol 2024; 223:e202308143. [PMID: 38448162 PMCID: PMC10913813 DOI: 10.1083/jcb.202308143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 02/05/2024] [Accepted: 02/20/2024] [Indexed: 03/08/2024] Open
Abstract
The septin cytoskeleton is extensively regulated by posttranslational modifications, such as phosphorylation, to achieve the diversity of architectures including rings, hourglasses, and gauzes. While many of the phosphorylation events of septins have been extensively studied in the budding yeast Saccharomyces cerevisiae, the regulation of the kinases involved remains poorly understood. Here, we show that two septin-associated kinases, the LKB1/PAR-4-related kinase Elm1 and the Nim1/PAR-1-related kinase Gin4, regulate each other at two discrete points of the cell cycle. During bud emergence, Gin4 targets Elm1 to the bud neck via direct binding and phosphorylation to control septin hourglass assembly and stability. During mitosis, Elm1 maintains Gin4 localization via direct binding and phosphorylation to enable timely remodeling of the septin hourglass into a double ring. This mutual control between Gin4 and Elm1 ensures that septin architecture is assembled and remodeled in a temporally controlled manner to perform distinct functions during the cell cycle.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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2
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Zheng S, Zheng B, Fu C. The Roles of Septins in Regulating Fission Yeast Cytokinesis. J Fungi (Basel) 2024; 10:115. [PMID: 38392788 PMCID: PMC10890454 DOI: 10.3390/jof10020115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/26/2024] [Accepted: 01/28/2024] [Indexed: 02/24/2024] Open
Abstract
Cytokinesis is required to separate two daughter cells at the end of mitosis, and septins play crucial roles in many aspects of cytokinesis. While septins have been intensively studied in many model organisms, including the budding yeast Saccharomyces cerevisiae, septins have been relatively less characterized in the fission yeast Schizosaccharomyces pombe, which has proven to be an excellent model organism for studying fundamental cell biology. In this review, we summarize the findings of septins made in fission yeasts mainly from four aspects: the domain structure of septins, the localization of septins during the cell cycle, the roles of septins in regulating cytokinesis, and the regulatory proteins of septins.
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Affiliation(s)
- Shengnan Zheng
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
- Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Biyu Zheng
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
- Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Chuanhai Fu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
- Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
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3
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Perucho-Jaimes L, Do J, Van Elgort A, Kaplan KB. Septins modulate the autophagy response after nutrient starvation. Mol Biol Cell 2024; 35:ar4. [PMID: 37910217 PMCID: PMC10881159 DOI: 10.1091/mbc.e22-11-0520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 09/19/2023] [Accepted: 10/16/2023] [Indexed: 11/03/2023] Open
Abstract
The pathways that induce macroautophagy (referred to as autophagy hereafter) in response to the stress of starvation are well conserved and essential under nutrient-limiting conditions. However, less is understood about the mechanisms that modulate the autophagy response. Here we present evidence that after induction of autophagy in budding yeast septin filaments rapidly assemble into discrete patches distributed along the cell cortex. These patches gradually mature over 12 h of nutrient deprivation to form extended structures around Atg9 membranes tethered at the cortical endoplasmic reticulum, a class of membranes that are limiting for autophagosome biogenesis. Loss of cortical septin structures alters the kinetics of autophagy activation and most dramatically extends the duration of the autophagy response. In wild-type cells, diffusion of Atg9 membranes at the cell cortex undergoes transient pauses that are dependent on septins, and septins at the bud neck block the diffusion of Atg9 membranes between mother and daughter cells. We conclude that septins reorganize at the cell cortex during autophagy to locally limit access of Atg9 membranes to autophagosome assembly sites, and thus modulate the autophagy response during nutrient deprivation.
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Affiliation(s)
- Luis Perucho-Jaimes
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Jonathan Do
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Alexandria Van Elgort
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Kenneth B. Kaplan
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
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4
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Marquardt J, Chen X, Bi E. Elucidating the Synergistic Role of Elm1 and Gin4 Kinases in Regulating Septin Hourglass Assembly. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.566235. [PMID: 37986786 PMCID: PMC10659281 DOI: 10.1101/2023.11.08.566235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
The septin cytoskeleton is extensively regulated by post-translational modifications such as phosphorylation to achieve the diversity of architectures including rings, hourglass, and gauzes. While many of the phosphorylation events of septins have been extensively studied in the budding yeast Saccharomyces cerevisiae, the regulation of the kinases involved remains poorly understood. Here we show that two septin-associated kinases, the LKB1/PAR-4-related kinase Elm1 and the Nim1/PAR-1-related kinase Gin4, regulate each other at two discrete points of the cell cycle. During bud emergence, Gin4 targets Elm1 to the bud neck via direct binding and phosphorylation to control septin hourglass assembly and stability. During mitosis, Elm1 maintains Gin4 localization via direct binding and phosphorylation to enable timely remodeling of the septin hourglass into a double ring. This unique synergy ensures that septin architecture is assembled and remodeled in a temporally controlled manner to perform distinct functions during the cell cycle.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
- Current affiliation: Department of Biology, Western Kentucky University, Bowling Green, KY
| | - Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
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5
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Sharma K, Menon MB. Decoding post-translational modifications of mammalian septins. Cytoskeleton (Hoboken) 2023; 80:169-181. [PMID: 36797225 DOI: 10.1002/cm.21747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 01/21/2023] [Accepted: 02/10/2023] [Indexed: 02/18/2023]
Abstract
Septins are cytoskeletal GTPases that form nonpolar filaments and higher-ordered structures and they take part in a wide range of cellular processes. Septins are conserved from yeast to mammals but absent from higher plants. The number of septin genes vary between organisms and they usually form complex heteropolymeric networks. Most septins are known to be capable of GTP hydrolysis which may regulate septin dynamics. Knowledge on regulation of septin function by post-translational modifications is still in its infancy. In this review article, we highlight the post-translational modifications reported for the 13 human septins and discuss their implications on septin functions. In addition to the functionally investigated modifications, we also try to make sense of the complex septin post-translational modification code revealed from large-scale phospho-proteomic datasets. Future studies may determine how these isoform-specific and homology group specific modifications affect septin structure and function.
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Affiliation(s)
- Khushboo Sharma
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, India
| | - Manoj B Menon
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, India
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6
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Arbizzani F, Mavrakis M, Hoya M, Ribas JC, Brasselet S, Paoletti A, Rincon SA. Septin filament compaction into rings requires the anillin Mid2 and contractile ring constriction. Cell Rep 2022; 39:110722. [PMID: 35443188 DOI: 10.1016/j.celrep.2022.110722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 02/10/2022] [Accepted: 03/30/2022] [Indexed: 11/19/2022] Open
Abstract
Septin filaments assemble into high-order molecular structures that associate with membranes, acting as diffusion barriers and scaffold proteins crucial for many cellular processes. How septin filaments organize in such structures is still not understood. Here, we used fission yeast to explore septin filament organization during cell division and its cell cycle regulation. Live-imaging and polarization microscopy analysis uncovered that septin filaments are initially recruited as a diffuse meshwork surrounding the acto-myosin contractile ring (CR) in anaphase, which undergoes compaction into two rings when CR constriction is initiated. We found that the anillin-like protein Mid2 is necessary to promote this compaction step, possibly acting as a bundler for septin filaments. Moreover, Mid2-driven septin compaction requires inputs from the septation initiation network as well as CR constriction and the β(1,3)-glucan synthase Bgs1. This work highlights that anillin-mediated septin ring assembly is under strict cell cycle control.
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Affiliation(s)
| | - Manos Mavrakis
- Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, UMR 7249, 13013 Marseille, France
| | - Marta Hoya
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain
| | - Juan Carlos Ribas
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain
| | - Sophie Brasselet
- Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, UMR 7249, 13013 Marseille, France
| | - Anne Paoletti
- Institut Curie, PSL University, CNRS UMR 144, 75005 Paris, France.
| | - Sergio A Rincon
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain.
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7
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Argüello-Miranda O, Marchand AJ, Kennedy T, Russo MAX, Noh J. Cell cycle-independent integration of stress signals by Xbp1 promotes Non-G1/G0 quiescence entry. J Cell Biol 2022; 221:212720. [PMID: 34694336 PMCID: PMC8548912 DOI: 10.1083/jcb.202103171] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 08/27/2021] [Accepted: 10/05/2021] [Indexed: 12/15/2022] Open
Abstract
Cellular quiescence is a nonproliferative state required for cell survival under stress and during development. In most quiescent cells, proliferation is stopped in a reversible state of low Cdk1 kinase activity; in many organisms, however, quiescent states with high-Cdk1 activity can also be established through still uncharacterized stress or developmental mechanisms. Here, we used a microfluidics approach coupled to phenotypic classification by machine learning to identify stress pathways associated with starvation-triggered high-Cdk1 quiescent states in Saccharomyces cerevisiae. We found that low- and high-Cdk1 quiescent states shared a core of stress-associated processes, such as autophagy, protein aggregation, and mitochondrial up-regulation, but differed in the nuclear accumulation of the stress transcription factors Xbp1, Gln3, and Sfp1. The decision between low- or high-Cdk1 quiescence was controlled by cell cycle-independent accumulation of Xbp1, which acted as a time-delayed integrator of the duration of stress stimuli. Our results show how cell cycle-independent stress-activated factors promote cellular quiescence outside G1/G0.
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Affiliation(s)
- Orlando Argüello-Miranda
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX.,Lyda Hill Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Ashley J Marchand
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Taylor Kennedy
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX.,School of Natural Sciences and Mathematics, University of Texas at Dallas, Richardson, TX
| | - Marielle A X Russo
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Jungsik Noh
- Lyda Hill Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX
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8
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Marquardt J, Chen X, Bi E. Septin Assembly and Remodeling at the Cell Division Site During the Cell Cycle. Front Cell Dev Biol 2021; 9:793920. [PMID: 34901034 PMCID: PMC8656427 DOI: 10.3389/fcell.2021.793920] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 11/08/2021] [Indexed: 11/17/2022] Open
Abstract
The septin family of proteins can assemble into filaments that further organize into different higher order structures to perform a variety of different functions in different cell types and organisms. In the budding yeast Saccharomyces cerevisiae, the septins localize to the presumptive bud site as a cortical ring prior to bud emergence, expand into an hourglass at the bud neck (cell division site) during bud growth, and finally “split” into a double ring sandwiching the cell division machinery during cytokinesis. While much work has been done to understand the functions and molecular makeups of these structures, the mechanisms underlying the transitions from one structure to another have largely remained elusive. Recent studies involving advanced imaging and in vitro reconstitution have begun to reveal the vast complexity involved in the regulation of these structural transitions, which defines the focus of discussion in this mini-review.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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9
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Lecinski S, Shepherd JW, Frame L, Hayton I, MacDonald C, Leake MC. Investigating molecular crowding during cell division and hyperosmotic stress in budding yeast with FRET. CURRENT TOPICS IN MEMBRANES 2021; 88:75-118. [PMID: 34862033 PMCID: PMC7612257 DOI: 10.1016/bs.ctm.2021.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cell division, aging, and stress recovery triggers spatial reorganization of cellular components in the cytoplasm, including membrane bound organelles, with molecular changes in their compositions and structures. However, it is not clear how these events are coordinated and how they integrate with regulation of molecular crowding. We use the budding yeast Saccharomyces cerevisiae as a model system to study these questions using recent progress in optical fluorescence microscopy and crowding sensing probe technology. We used a Förster Resonance Energy Transfer (FRET) based sensor, illuminated by confocal microscopy for high throughput analyses and Slimfield microscopy for single-molecule resolution, to quantify molecular crowding. We determine crowding in response to cellular growth of both mother and daughter cells, in addition to osmotic stress, and reveal hot spots of crowding across the bud neck in the burgeoning daughter cell. This crowding might be rationalized by the packing of inherited material, like the vacuole, from mother cells. We discuss recent advances in understanding the role of crowding in cellular regulation and key current challenges and conclude by presenting our recent advances in optimizing FRET-based measurements of crowding while simultaneously imaging a third color, which can be used as a marker that labels organelle membranes. Our approaches can be combined with synchronized cell populations to increase experimental throughput and correlate molecular crowding information with different stages in the cell cycle.
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Affiliation(s)
- Sarah Lecinski
- Department of Physics, University of York, York, United Kingdom
| | - Jack W Shepherd
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom
| | - Lewis Frame
- School of Natural Sciences, University of York, York, United Kingdom
| | - Imogen Hayton
- Department of Biology, University of York, York, United Kingdom
| | - Chris MacDonald
- Department of Biology, University of York, York, United Kingdom
| | - Mark C Leake
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom.
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10
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Prabhakar A, González B, Dionne H, Basu S, Cullen PJ. Spatiotemporal control of pathway sensors and cross-pathway feedback regulate a differentiation MAPK pathway in yeast. J Cell Sci 2021; 134:jcs258341. [PMID: 34347092 PMCID: PMC8353523 DOI: 10.1242/jcs.258341] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 06/21/2021] [Indexed: 12/22/2022] Open
Abstract
Mitogen-activated protein kinase (MAPK) pathways control cell differentiation and the response to stress. In Saccharomyces cerevisiae, the MAPK pathway that controls filamentous growth (fMAPK) shares components with the pathway that regulates the response to osmotic stress (HOG). Here, we show that the two pathways exhibit different patterns of activity throughout the cell cycle. The different patterns resulted from different expression profiles of genes encoding mucin sensors that regulate the pathways. Cross-pathway regulation from the fMAPK pathway stimulated the HOG pathway, presumably to modulate fMAPK pathway activity. We also show that the shared tetraspan protein Sho1p, which has a dynamic localization pattern throughout the cell cycle, induced the fMAPK pathway at the mother-bud neck. A Sho1p-interacting protein, Hof1p, which also localizes to the mother-bud neck and regulates cytokinesis, also regulated the fMAPK pathway. Therefore, spatial and temporal regulation of pathway sensors, and cross-pathway regulation, control a MAPK pathway that regulates cell differentiation in yeast.
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Affiliation(s)
| | | | | | | | - Paul J. Cullen
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA
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11
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Wang X, Wang W, Wang X, Wang M, Zhu L, Garba F, Fu C, Zieger B, Liu X, Liu X, Yao X. The septin complex links the catenin complex to the actin cytoskeleton for establishing epithelial cell polarity. J Mol Cell Biol 2021; 13:395-408. [PMID: 34143183 PMCID: PMC8436676 DOI: 10.1093/jmcb/mjab036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 03/16/2021] [Accepted: 03/23/2021] [Indexed: 11/13/2022] Open
Abstract
Cell polarity is essential for spatially regulating of physiological processes in metazoans by which hormonal stimulation‒secretion coupling is precisely coupled for tissue homeostasis and organ communications. However, the molecular mechanisms underlying epithelial cell polarity establishment remain elusive. Here, we show that septin cytoskeleton interacts with catenin complex to organize a functional domain to separate apical from basal membranes in polarized epithelial cells. Using polarized epithelial cell monolayer as a model system with transepithelial electrical resistance as functional readout, our studies show that septins are essential for epithelial cell polarization. Our proteomic analyses discovered a novel septin‒catenin complex during epithelial cell polarization. The functional relevance of septin‒catenin complex was then examined in three-dimensional (3D) culture in which suppression of septins resulted in deformation of apical lumen in cysts, a hallmark seen in polarity-deficient 3D cultures and animals. Mechanistically, septin cytoskeleton stabilizes the association of adherens catenin complex with actin cytoskeleton, and depletion or disruption of septin cytoskeleton liberates adherens junction and polarity complexes into the cytoplasm. Together, these findings reveal a previously unrecognized role for septin cytoskeleton in the polarization of the apical‒basal axis and lumen formation in polarized epithelial cells.
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Affiliation(s)
- Xueying Wang
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Keck Center for Organoids Plasticity Control, Atlanta, GA 30310, USA
| | - Wenwen Wang
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Anhui Key Laboratory for Cellular Dynamics & Chemical Biology and CAS Center for Excellence in Molecular Cell Science, Hefei 230027, China.,Keck Center for Organoids Plasticity Control, Atlanta, GA 30310, USA
| | - Xiwei Wang
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Keck Center for Organoids Plasticity Control, Atlanta, GA 30310, USA
| | - Ming Wang
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China
| | - Lijuan Zhu
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Anhui Key Laboratory for Cellular Dynamics & Chemical Biology and CAS Center for Excellence in Molecular Cell Science, Hefei 230027, China
| | - Fatima Garba
- Keck Center for Organoids Plasticity Control, Atlanta, GA 30310, USA
| | - Chuanhai Fu
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Anhui Key Laboratory for Cellular Dynamics & Chemical Biology and CAS Center for Excellence in Molecular Cell Science, Hefei 230027, China
| | - Barbara Zieger
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Xu Liu
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Keck Center for Organoids Plasticity Control, Atlanta, GA 30310, USA
| | - Xing Liu
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Anhui Key Laboratory for Cellular Dynamics & Chemical Biology and CAS Center for Excellence in Molecular Cell Science, Hefei 230027, China
| | - Xuebiao Yao
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China.,Anhui Key Laboratory for Cellular Dynamics & Chemical Biology and CAS Center for Excellence in Molecular Cell Science, Hefei 230027, China
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12
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Spiliotis ET, McMurray MA. Masters of asymmetry - lessons and perspectives from 50 years of septins. Mol Biol Cell 2021; 31:2289-2297. [PMID: 32991244 PMCID: PMC7851956 DOI: 10.1091/mbc.e19-11-0648] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Septins are a unique family of GTPases, which were discovered 50 years ago as essential genes for the asymmetric cell shape and division of budding yeast. Septins assemble into filamentous nonpolar polymers, which associate with distinct membrane macrodomains and subpopulations of actin filaments and microtubules. While structurally a cytoskeleton-like element, septins function predominantly as spatial regulators of protein localization and interactions. Septin scaffolds and barriers have provided a long-standing paradigm for the generation and maintenance of asymmetry in cell membranes. Septins also promote asymmetry by regulating the spatial organization of the actin and microtubule cytoskeleton, and biasing the directionality of membrane traffic. In this 50th anniversary perspective, we highlight how septins have conserved and adapted their roles as effectors of membrane and cytoplasmic asymmetry across fungi and animals. We conclude by outlining principles of septin function as a module of symmetry breaking, which alongside the monomeric small GTPases provides a core mechanism for the biogenesis of molecular asymmetry and cell polarity.
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Affiliation(s)
| | - Michael A McMurray
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
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13
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Huang M, Wang Y. GLOBAL AND TARGETED PROFILING OF GTP-BINDING PROTEINS IN BIOLOGICAL SAMPLES BY MASS SPECTROMETRY. MASS SPECTROMETRY REVIEWS 2021; 40:215-235. [PMID: 32519381 PMCID: PMC7725852 DOI: 10.1002/mas.21637] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/04/2020] [Accepted: 05/15/2020] [Indexed: 05/05/2023]
Abstract
GTP-binding proteins are among the most important enzyme families that are involved in a plethora of biological processes. However, owing to the enormous diversity of the nucleotide-binding protein family, comprehensive analyses of the expression level, structure, activity, and regulatory mechanisms of GTP-binding proteins remain challenging with the use of conventional approaches. The many advances in mass spectrometry (MS) instrumentation and data acquisition methods, together with a variety of enrichment approaches in sample preparation, render MS a powerful tool for the comprehensive characterizations of the activities and expression levels of various GTP-binding proteins. We review herein the recent developments in the application of MS-based techniques, together with general and widely used affinity enrichment approaches, for the proteome-wide and targeted capture, identification, and quantification of GTP-binding proteins. The working principles, advantages, and limitations of various strategies for profiling the expression level, activity, posttranslational modifications, and interactome of GTP-binding proteins are discussed. It can be envisaged that future applications of MS-based proteomics will lead to a better understanding about the roles of GTP-binding proteins in different biological processes and human diseases. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.
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Affiliation(s)
- Ming Huang
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, CA 92521, USA
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, CA 92521, USA
- Department of Chemistry, University of California Riverside, Riverside, CA 92521, USA
- Correspondence author: Yinsheng Wang. Telephone: (951)827-2700;
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14
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Chen TY, Lin TC, Kuo PL, Chen ZR, Cheng HL, Chao YY, Syu JS, Lu FI, Wang CY. Septin 7 is a centrosomal protein that ensures S phase entry and microtubule nucleation by maintaining the abundance of p150 glued. J Cell Physiol 2020; 236:2706-2724. [PMID: 32869310 DOI: 10.1002/jcp.30037] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 08/18/2020] [Accepted: 08/20/2020] [Indexed: 12/16/2022]
Abstract
Septins play important roles in regulating development and differentiation. Septin 7 (SEPT7) is a crucial component in orchestrating the septin core complex into highly ordered filamentous structures. Here, we showed that genetic depletion of SEPT7 or treatment with forchlorfenuron (FCF; a compound known to affect septin filament assembly) led to reduced the S phase entry in cell models and zebrafish embryos. In addition to colocalizing with actin filaments, SEPT7 resided in the centrosome, and SEPT7 depletion led to aberrant mitotic spindle pole formation. This mitotic defect was rescued in SEPT7-deficient cells by wild-type SEPT7, suggesting that SEPT7 maintained mitotic spindle poles. In addition, we observed disorganized microtubule nucleation and reduced cell migration with SEPT7 depletion. Furthermore, SEPT7 formed a complex with and maintained the abundance of p150glued , the component of centriole subdistal appendages. Depletion of p150glued resulted in a phenotype reminiscent of SEPT7-deficient cells, and overexpression of p150glued reversed the defective phenotypes. Thus, SEPT7 is a centrosomal protein that maintains proper cell proliferation and microtubule array formation via maintaining the abundance of p150glued .
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Affiliation(s)
- Ting-Yu Chen
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Tzu-Chien Lin
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Pao-Lin Kuo
- Department of Obstetrics and Gynecology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Zi-Rong Chen
- Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.,The iEGG and Animal Biotechnology Center, National Chung Hsing University, Taichung, Taiwan
| | - Hui-Ling Cheng
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yu-Ying Chao
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Jhih-Siang Syu
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Fu-I Lu
- Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.,The iEGG and Animal Biotechnology Center, National Chung Hsing University, Taichung, Taiwan
| | - Chia-Yih Wang
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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15
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Farkašovský M. Septin architecture and function in budding yeast. Biol Chem 2020; 401:903-919. [PMID: 31913844 DOI: 10.1515/hsz-2019-0401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/28/2019] [Indexed: 01/22/2023]
Abstract
The septins constitute a conserved family of guanosine phosphate-binding and filament-forming proteins widespread across eukaryotic species. Septins appear to have two principal functions. One is to form a cortical diffusion barrier, like the septin collar at the bud neck of Saccharomyces cerevisiae, which prevents movement of membrane-associated proteins between the mother and daughter cells. The second is to serve as a polymeric scaffold for recruiting the proteins required for critical cellular processes to particular subcellular areas. In the last decade, structural information about the different levels of septin organization has appeared, but crucial structural determinants and factors responsible for septin assembly remain largely unknown. This review highlights recent findings on the architecture and function of septins and their remodeling with an emphasis on mitotically dividing budding yeasts.
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Affiliation(s)
- Marian Farkašovský
- Department of Biochemistry and Protein Structure, Institute of Molecular Biology SAS, Dubravska cesta 21, 84551 Bratislava, Slovak Republic
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16
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Marquardt J, Yao LL, Okada H, Svitkina T, Bi E. The LKB1-like Kinase Elm1 Controls Septin Hourglass Assembly and Stability by Regulating Filament Pairing. Curr Biol 2020; 30:2386-2394.e4. [PMID: 32386534 PMCID: PMC7314651 DOI: 10.1016/j.cub.2020.04.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/20/2020] [Accepted: 04/16/2020] [Indexed: 01/22/2023]
Abstract
Septins form rod-shaped hetero-oligomeric complexes that assemble into filaments and other higher-order structures, such as rings or hourglasses, at the cell division site in fungal and animal cells [1-4] to carry out a wide range of functions, including cytokinesis and cell morphogenesis. However, the architecture of septin higher-order assemblies and their control mechanisms, including regulation by conserved kinases [5, 6], remain largely unknown. In the budding yeast Saccharomyces cerevisiae, the five mitotic septins (Cdc3, Cdc10, Cdc11, Cdc12, and Shs1) localize to the bud neck and form an hourglass before cytokinesis that acts as a scaffold for proteins involved in multiple processes as well as a membrane-diffusible barrier between the mother and developing bud [7-9]. The hourglass is remodeled into a double ring that sandwiches the actomyosin ring at the onset of cytokinesis [10-13]. How septins are assembled into a highly ordered hourglass structure at the division site [13] is largely unexplored. Here we show that the LKB1-like kinase Elm1, which has been implicated in septin organization [14], cell morphogenesis [15], and mitotic exit [16, 17], specifically associates with the septin hourglass during the cell cycle and controls hourglass assembly and stability, especially for the daughter half, by regulating filament pairing and the functionality of its substrate, the septin-binding protein Bni5. This study illustrates how a protein kinase regulates septin architecture at the filament level and suggests that filament pairing is a highly regulated process during septin assembly and remodeling in vivo.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Lin-Lin Yao
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA; Group of Cell Motility and Muscle Contraction, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hiroki Okada
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Tatyana Svitkina
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA.
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17
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Dahiya R, Mohammad T, Alajmi MF, Rehman MT, Hasan GM, Hussain A, Hassan MI. Insights into the Conserved Regulatory Mechanisms of Human and Yeast Aging. Biomolecules 2020; 10:E882. [PMID: 32526825 PMCID: PMC7355435 DOI: 10.3390/biom10060882] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 05/22/2020] [Accepted: 05/27/2020] [Indexed: 12/12/2022] Open
Abstract
Aging represents a significant biological process having strong associations with cancer, diabetes, and neurodegenerative and cardiovascular disorders, which leads to progressive loss of cellular functions and viability. Astonishingly, age-related disorders share several genetic and molecular mechanisms with the normal aging process. Over the last three decades, budding yeast Saccharomyces cerevisiae has emerged as a powerful yet simple model organism for aging research. Genetic approaches using yeast RLS have led to the identification of hundreds of genes impacting lifespan in higher eukaryotes. Numerous interventions to extend yeast lifespan showed an analogous outcome in multi-cellular eukaryotes like fruit flies, nematodes, rodents, and humans. We collected and analyzed a multitude of observations from published literature and provide the contribution of yeast in the understanding of aging hallmarks most applicable to humans. Here, we discuss key pathways and molecular mechanisms that underpin the evolutionarily conserved aging process and summarize the current understanding and clinical applicability of its trajectories. Gathering critical information on aging biology would pave the way for future investigation targeted at the discovery of aging interventions.
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Affiliation(s)
- Rashmi Dahiya
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
| | - Taj Mohammad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
| | - Mohamed F. Alajmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.F.A.); (M.T.R.); (A.H.)
| | - Md. Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.F.A.); (M.T.R.); (A.H.)
| | - Gulam Mustafa Hasan
- Department of Biochemistry, College of Medicine, Prince Sattam Bin Abdulaziz University, P.O. Box 173, Al-Kharj 11942, Saudi Arabia;
| | - Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.F.A.); (M.T.R.); (A.H.)
| | - Md. Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
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18
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Chen X, Wang K, Svitkina T, Bi E. Critical Roles of a RhoGEF-Anillin Module in Septin Architectural Remodeling during Cytokinesis. Curr Biol 2020; 30:1477-1490.e3. [PMID: 32197082 DOI: 10.1016/j.cub.2020.02.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/23/2019] [Accepted: 02/10/2020] [Indexed: 12/24/2022]
Abstract
How septin architecture is remodeled from an hourglass to a double ring during cytokinesis in fungal and animal cells remains unknown. Here, we show that during the hourglass-to-double-ring transition in budding yeast, septins acquire a "zonal architecture" in which paired septin filaments that are organized along the mother-bud axis associate with circumferential single septin filaments, the Rho guanine-nucleotide-exchange factor (RhoGEF) Bud3, and the anillin-like protein Bud4 exclusively at the outer zones and with myosin-II filaments in the middle zone. Deletion of Bud3 or its Bud4-interacting domain, but not its RhoGEF domain, leads to a complete loss of the single filaments, whereas deletion of Bud4 or its Bud3-interacting domain destabilizes the transitional hourglass, especially at the mother side, with partial loss of both filament types. Deletion of Bud3 and Bud4 together further weakens the transitional structure and abolishes the double ring formation while causing no obvious defect in actomyosin ring constriction. This and further analyses suggest that Bud3 stabilizes the single filaments, whereas Bud4 strengthens the interaction between the paired and single filaments at the outer zones of the transitional hourglass, as well as in the double ring. This study reveals a striking zonal architecture for the transitional hourglass that pre-patterns two cytokinetic structures-a septin double ring and an actomyosin ring-and also defines the essential roles of a RhoGEF-anillin module in septin architectural remodeling during cytokinesis at the filament level.
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Affiliation(s)
- Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Kangji Wang
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Tatyana Svitkina
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA.
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19
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Qiu R, Runxiang Q, Geng A, Liu J, Xu CW, Menon MB, Gaestel M, Lu Q. SEPT7 Interacts with KIF20A and Regulates the Proliferative State of Neural Progenitor Cells During Cortical Development. Cereb Cortex 2019; 30:3030-3043. [PMID: 31813992 DOI: 10.1093/cercor/bhz292] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 02/01/2019] [Accepted: 10/21/2019] [Indexed: 02/06/2023] Open
Abstract
Balanced proliferation and differentiation of neural progenitor cells (NPCs) are critical for brain development, but how the process is regulated and what components of the cell division machinery is involved are not well understood. Here we report that SEPT7, a cell division regulator originally identified in Saccharomyces cerevisiae, interacts with KIF20A in the intercellular bridge of dividing NPCs and plays an essential role in maintaining the proliferative state of NPCs during cortical development. Knockdown of SEPT7 in NPCs results in displacement of KIF20A from the midbody and early neuronal differentiation. NPC-specific inducible knockout of Sept7 causes early cell cycle exit, precocious neuronal differentiation, and ventriculomegaly in the cortex, but surprisingly does not lead to noticeable cytokinesis defect. Our data uncover an interaction of SEPT7 and KIF20A during NPC divisions and demonstrate a crucial role of SEPT7 in cell fate determination. In addition, this study presents a functional approach for identifying additional cell fate regulators of the mammalian brain.
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Affiliation(s)
- Runxiang Qiu
- Department of Developmental and Stem Cell Biology, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
| | - Qiu Runxiang
- Department of Developmental and Stem Cell Biology, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
| | - Anqi Geng
- Department of Developmental and Stem Cell Biology, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA.,Institute of Medical Research, Northwestern Polytechnical University, Xian, Shaanxi Province, China
| | - Jiancheng Liu
- Department of Developmental and Stem Cell Biology, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
| | - C Wilson Xu
- Balto Pharmaceuticals, Inc., South Pasadena, CA 91030, USA
| | - Manoj B Menon
- Institute of Cell Biochemistry, Hannover Medical School, Hannover 30625, Germany.,Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New-Delhi 110016, India
| | - Matthias Gaestel
- Institute of Cell Biochemistry, Hannover Medical School, Hannover 30625, Germany
| | - Qiang Lu
- Department of Developmental and Stem Cell Biology, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
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20
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Perez AM, Thorner J. Septin-associated proteins Aim44 and Nis1 traffic between the bud neck and the nucleus in the yeast Saccharomyces cerevisiae. Cytoskeleton (Hoboken) 2018; 76:15-32. [PMID: 30341817 PMCID: PMC6474838 DOI: 10.1002/cm.21500] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 09/25/2018] [Accepted: 10/10/2018] [Indexed: 12/20/2022]
Abstract
In budding yeast, a collar of septin filaments at the neck between a mother cell and its bud marks the incipient site for cell division and serves as a scaffold that recruits proteins required for proper spatial and temporal execution of cytokinesis. A set of interacting proteins that localize at or near the bud neck, including Aim44/Gps1, Nba1 and Nis1, also has been implicated in preventing Cdc42‐dependent bud site re‐establishment at the division site. We found that, at their endogenous level, Aim44 and Nis1 robustly localize sequentially at the septin collar. Strikingly, however, when overproduced, both proteins shift their subcellular distribution predominantly to the nucleus. Aim44 localizes with the inner nuclear envelope, as well as at the plasma membrane, whereas Nis1 accumulates within the nucleus, indicating that these proteins normally undergo nucleocytoplasmic shuttling. Of the 14 yeast karyopherins, Kap123/Yrb4 is the primary importin for Aim44, whereas several importins mediate Nis1 nuclear entry. Conversely, Kap124/Xpo1/Crm1 is the primary exportin for Nis1, whereas both Xpo1 and Cse1/Kap109 likely contribute to Aim44 nuclear export. Even when endogenously expressed, Nis1 accumulates in the nucleus when Nba1 is absent. When either Aim44 or Nis1 are overexpressed, Nba1 is displaced from the bud neck, further consistent with the mutual interactions of these proteins. Collectively, our results indicate that a previously unappreciated level at which localization of septin‐associated proteins is controlled is via regulation of their nucleocytoplasmic shuttling, which places constraints on their availability for complex formation with other partners at the bud neck.
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Affiliation(s)
- Adam M Perez
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California
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21
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Vissa A, Giuliani M, Froese CD, Kim MS, Soroor F, Kim PK, Trimble WS, Yip CM. Single‐molecule localization microscopy of septin bundles in mammalian cells. Cytoskeleton (Hoboken) 2018; 76:63-72. [DOI: 10.1002/cm.21481] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 07/04/2018] [Accepted: 07/16/2018] [Indexed: 12/25/2022]
Affiliation(s)
- Adriano Vissa
- Institute of Biomaterials and Biomedical EngineeringUniversity of Toronto Toronto Ontario Canada
- Donnelly Centre for Cellular and Biomolecular ResearchUniversity of Toronto Toronto Ontario Canada
| | - Maximiliano Giuliani
- Institute of Biomaterials and Biomedical EngineeringUniversity of Toronto Toronto Ontario Canada
- Donnelly Centre for Cellular and Biomolecular ResearchUniversity of Toronto Toronto Ontario Canada
| | - Carol D. Froese
- Program in Cell BiologyThe Hospital for Sick Children Toronto Ontario Canada
| | - Moshe S. Kim
- Program in Cell BiologyThe Hospital for Sick Children Toronto Ontario Canada
| | - Forooz Soroor
- Program in Cell BiologyThe Hospital for Sick Children Toronto Ontario Canada
- Department of BiochemistryUniversity of Toronto Toronto Ontario Canada
| | - Peter K. Kim
- Program in Cell BiologyThe Hospital for Sick Children Toronto Ontario Canada
- Department of BiochemistryUniversity of Toronto Toronto Ontario Canada
| | - William S. Trimble
- Program in Cell BiologyThe Hospital for Sick Children Toronto Ontario Canada
- Department of BiochemistryUniversity of Toronto Toronto Ontario Canada
- Department of PhysiologyUniversity of Toronto Toronto Ontario Canada
| | - Christopher M. Yip
- Institute of Biomaterials and Biomedical EngineeringUniversity of Toronto Toronto Ontario Canada
- Donnelly Centre for Cellular and Biomolecular ResearchUniversity of Toronto Toronto Ontario Canada
- Department of BiochemistryUniversity of Toronto Toronto Ontario Canada
- Department of Chemical Engineering and Applied ChemistryUniversity of Toronto Toronto Ontario Canada
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22
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Marquardt J, Chen X, Bi E. Architecture, remodeling, and functions of the septin cytoskeleton. Cytoskeleton (Hoboken) 2018; 76:7-14. [PMID: 29979831 DOI: 10.1002/cm.21475] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 06/05/2018] [Accepted: 06/22/2018] [Indexed: 01/22/2023]
Abstract
The septin family of proteins has fascinated cell biologists for decades due to the elaborate architecture they adopt in different eukaryotic cells. Whether they exist as rings, collars, or gauzes in different cell types and at different times in the cell cycle illustrates a complex series of regulation in structure. While the organization of different septin structures at the cortex of different cell types during the cell cycle has been described to various degrees, the exact structure and regulation at the filament level are still largely unknown. Recent advances in fluorescent and electron microscopy, as well as work in septin biochemistry, have allowed new insights into the aspects of septin architecture, remodeling, and function in many cell types. This mini-review highlights many of the recent findings with an emphasis on the budding yeast model.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
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23
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Vitulo N, Dalla Valle L, Skobo T, Valle G, Alibardi L. Downregulation of lizard immuno-genes in the regenerating tail and myogenes in the scarring limb suggests that tail regeneration occurs in an immuno-privileged organ. PROTOPLASMA 2017; 254:2127-2141. [PMID: 28357509 DOI: 10.1007/s00709-017-1107-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 03/20/2017] [Indexed: 06/06/2023]
Abstract
Amputated tails of lizards regenerate while limbs form scars which histological structure is very different from the original organs. Lizards provide useful information for regenerative medicine and some hypotheses on the loss of regeneration in terrestrial vertebrates. Analysis of tail and limb transcriptomes shows strong downregulation in the tail blastema for immunoglobulins and surface B and T receptors, cell function, and metabolism. In contrast, in the limb blastema genes for myogenesis, muscle and cell function, and extracellular matrix deposition but not immunity are variably downregulated. The upregulated genes show that the regenerating tail is an embryonic organ driven by the Wnt pathway and non-coding RNAs. The strong inflammation following amputation, the non-activation of the Wnt pathway, and the upregulation of inflammatory genes with no downregulation of immune genes indicate that the amputated limb does not activate an embryonic program. Intense inflammation in limbs influences in particular the activity of genes coding for muscle proteins, cell functions, and stimulates the deposition of dense extracellular matrix proteins resulting in scarring limb outgrowths devoid of muscles. The present study complements that on upregulated genes, and indicates that the regenerating tail requires immune suppression to maintain this embryonic organ connected to the rest of the tail without be rejected or turned into a scar. It is hypothesized that the evolution of the adaptive immune system determined scarring instead of organ regeneration in terrestrial vertebrates and that lizards evolved the process of tail regeneration through a mechanism of immuno-evasion.
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Affiliation(s)
- Nicola Vitulo
- Department of Biotechnology, University of Verona, Verona, Italy
| | | | - Tatjana Skobo
- Department of Biology, University of Padova, Padova, Italy
| | - Giorgio Valle
- Department of Biology, University of Padova, Padova, Italy
| | - Lorenzo Alibardi
- Comparative Histolab, Padova, Italy.
- Dipartimento Bigea, Università di Bologna, Via Selmi 3, 40126, Bologna, Italy.
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24
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Melloy PG, Rose MD. Influence of the bud neck on nuclear envelope fission in Saccharomyces cerevisiae. Exp Cell Res 2017; 358:390-396. [PMID: 28711459 DOI: 10.1016/j.yexcr.2017.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 07/06/2017] [Accepted: 07/11/2017] [Indexed: 11/30/2022]
Abstract
Studies have shown that nuclear envelope fission (karyokinesis) in budding yeast depends on cytokinesis, but not distinguished whether this was a direct requirement, indirect, because of cell cycle arrest, or due to bud neck-localized proteins impacting both processes. To determine the requirements for karyokinesis, we examined mutants conditionally defective for bud emergence and/or nuclear migration. The common mutant phenotype was completion of the nuclear division cycle within the mother cell, but karyokinesis did not occur. In the cdc24 swe1 mutant, at the non-permissive temperature, multiple nuclei accumulated within the unbudded cell, with connected nuclear envelopes. Upon return to the permissive temperature, the cdc24 swe1 mutant initiated bud emergence, but only the nucleus spanning the neck underwent fission suggesting that the bud neck region is important for fission initiation. The neck may be critical for either mechanical reasons, as the contractile ring might facilitate fission, or for regulatory reasons, as the site of a protein network regulating nuclear envelope fission, mitotic exit, and cytokinesis. We also found that 77-85% of pairs of septin mutant nuclei completed nuclear envelope fission. In addition, 27% of myo1Δ mutant nuclei completed karyokinesis. These data suggested that fission is not dependent on mechanical contraction at the bud neck, but was instead controlled by regulatory proteins there.
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Affiliation(s)
- Patricia G Melloy
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States; Department of Biological and Allied Health Sciences, Fairleigh Dickinson University, Madison, NJ, United States.
| | - Mark D Rose
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States
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25
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Rai U, Najm F, Tartakoff AM. Nucleolar asymmetry and the importance of septin integrity upon cell cycle arrest. PLoS One 2017; 12:e0174306. [PMID: 28339487 PMCID: PMC5365125 DOI: 10.1371/journal.pone.0174306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 03/07/2017] [Indexed: 12/31/2022] Open
Abstract
Cell cycle arrest can be imposed by inactivating the anaphase promoting complex (APC). In S. cerevisiae this arrest has been reported to stabilize a metaphase-like intermediate in which the nuclear envelope spans the bud neck, while chromatin repeatedly translocates between the mother and bud domains. The present investigation was undertaken to learn how other features of nuclear organization are affected upon depletion of the APC activator, Cdc20. We observe that the spindle pole bodies and the spindle repeatedly translocate across the narrow orifice at the level of the neck. Nevertheless, we find that the nucleolus (organized around rDNA repeats on the long right arm of chromosome XII) remains in the mother domain, marking the polarity of the nucleus. Accordingly, chromosome XII is polarized: TelXIIR remains in the mother domain and its centromere is predominantly located in the bud domain. In order to learn why the nucleolus remains in the mother domain, we studied the impact of inhibiting rRNA synthesis in arrested cells. We observed that this fragments the nucleolus and that these fragments entered the bud domain. Taken together with earlier observations, the restriction of the nucleolus to the mother domain therefore can be attributed to its massive structure. We also observed that inactivation of septins allowed arrested cells to complete the cell cycle, that the alternative APC activator, Cdh1, was required for completion of the cell cycle and that induction of Cdh1 itself caused arrested cells to progress to the end of the cell cycle.
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Affiliation(s)
- Urvashi Rai
- Cell Biology Program/Department of Molecular and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Fadi Najm
- Division of Medical Sciences, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Alan M. Tartakoff
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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26
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Kim SW, Lee KJ, Kim S, Kim J, Cho K, Ro HS, Park HS. Genetic incorporation of N ε-acetyllysine reveals a novel acetylation-sumoylation switch in yeast. Biochim Biophys Acta Gen Subj 2017; 1861:3030-3037. [PMID: 28188860 DOI: 10.1016/j.bbagen.2017.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 02/02/2017] [Indexed: 10/20/2022]
Abstract
The lysine acetylation of proteins plays a key role in regulating protein functions, thereby controlling a wide range of cellular processes. Despite the prevalence and significance of lysine acetylation in eukaryotes, however, its systematic study has been challenged by the technical limitations of conventional approaches for selective lysine acetylation in vivo. Here, we report the in vivo study of lysine acetylation via the genetic incorporation of Nε-acetyllysine in yeast. We demonstrate that a newly discovered acetylation-sumoylation switch precisely controls the localization and cellular function of the yeast septin protein, Cdc11, during the cell cycle. This approach should facilitate the comprehensive in vivo study of lysine acetylation across a wide range of proteins in eukaryotic organisms. This article is part of a Special Issue entitled "Biochemistry of Synthetic Biology - Recent Developments" Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue.
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Affiliation(s)
- Sang-Woo Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Kyung Jin Lee
- Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Sinil Kim
- Division of Applied Life Science and Research Institute for Life Science, Gyeongsang National University, Jinju 660-701, Republic of Korea
| | - Jihyo Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Kyukwang Cho
- Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Hyeon-Su Ro
- Division of Applied Life Science and Research Institute for Life Science, Gyeongsang National University, Jinju 660-701, Republic of Korea.
| | - Hee-Sung Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
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27
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Abstract
Cytokinesis is essential for the survival of all organisms. It requires concerted functions of cell signaling, force production, exocytosis, and extracellular matrix remodeling. Due to the conservation in core components and mechanisms between fungal and animal cells, the budding yeast Saccharomyces cerevisiae has served as an attractive model for studying this fundamental process. In this review, we discuss the mechanics and regulation of distinct events of cytokinesis in budding yeast, including the assembly, constriction, and disassembly of the actomyosin ring, septum formation, abscission, and their spatiotemporal coordination. We also highlight the key concepts and questions that are common to animal and fungal cytokinesis.
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Affiliation(s)
- Yogini P Bhavsar-Jog
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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28
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Booth EA, Sterling SM, Dovala D, Nogales E, Thorner J. Effects of Bni5 Binding on Septin Filament Organization. J Mol Biol 2016; 428:4962-4980. [PMID: 27806918 DOI: 10.1016/j.jmb.2016.10.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 10/17/2016] [Accepted: 10/24/2016] [Indexed: 12/31/2022]
Abstract
Septins are a protein family found in all eukaryotes (except higher plants) that have roles in membrane remodeling and formation of diffusion barriers and as a scaffold to recruit other proteins. In budding yeast, proper execution of cytokinesis and cell division requires the formation of a collar of circumferential filaments at the bud neck. These filaments are assembled from apolar septin hetero-octamers. Currently, little is known about the mechanisms that control the arrangement and dynamics of septin structures. In this study, we utilized both Förster resonance energy transfer and electron microscopy to analyze the biophysical properties of the septin-binding protein Bni5 and how its association with septin filaments affects their organization. We found that the interaction of Bni5 with the terminal subunit (Cdc11) at the junctions between adjacent hetero-octamers in paired filaments is highly cooperative. Both the C-terminal end of Bni5 and the C-terminal extension of Cdc11 make important contributions to their interaction. Moreover, this binding may stabilize the dimerization of Bni5, which, in turn, forms cross-filament braces that significantly narrow, and impose much more uniform spacing on, the gap between paired filaments.
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Affiliation(s)
- Elizabeth A Booth
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA.
| | - Sarah M Sterling
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA.
| | - Dustin Dovala
- Program in Microbial Pathogenesis and Host Defense, Department of Microbiology and Immunology, University of California School of Medicine, San Francisco, CA 94143, USA.
| | - Eva Nogales
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; Life Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA.
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29
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Perez AM, Finnigan GC, Roelants FM, Thorner J. Septin-Associated Protein Kinases in the Yeast Saccharomyces cerevisiae. Front Cell Dev Biol 2016; 4:119. [PMID: 27847804 PMCID: PMC5088441 DOI: 10.3389/fcell.2016.00119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 10/14/2016] [Indexed: 01/19/2023] Open
Abstract
Septins are a family of eukaryotic GTP-binding proteins that associate into linear rods, which, in turn, polymerize end-on-end into filaments, and further assemble into other, more elaborate super-structures at discrete subcellular locations. Hence, septin-based ensembles are considered elements of the cytoskeleton. One function of these structures that has been well-documented in studies conducted in budding yeast Saccharomyces cerevisiae is to serve as a scaffold that recruits regulatory proteins, which dictate the spatial and temporal control of certain aspects of the cell division cycle. In particular, septin-associated protein kinases couple cell cycle progression with cellular morphogenesis. Thus, septin-containing structures serve as signaling platforms that integrate a multitude of signals and coordinate key downstream networks required for cell cycle passage. This review summarizes what we currently understand about how the action of septin-associated protein kinases and their substrates control information flow to drive the cell cycle into and out of mitosis, to regulate bud growth, and especially to direct timely and efficient execution of cytokinesis and cell abscission. Thus, septin structures represent a regulatory node at the intersection of many signaling pathways. In addition, and importantly, the activities of certain septin-associated protein kinases also regulate the state of organization of the septins themselves, creating a complex feedback loop.
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Affiliation(s)
- Adam M Perez
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley Berkeley, CA, USA
| | - Gregory C Finnigan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley Berkeley, CA, USA
| | - Françoise M Roelants
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley Berkeley, CA, USA
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley Berkeley, CA, USA
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30
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Angelis D, Spiliotis ET. Septin Mutations in Human Cancers. Front Cell Dev Biol 2016; 4:122. [PMID: 27882315 PMCID: PMC5101219 DOI: 10.3389/fcell.2016.00122] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 10/17/2016] [Indexed: 12/22/2022] Open
Abstract
Septins are GTP-binding proteins that are evolutionarily and structurally related to the RAS oncogenes. Septin expression levels are altered in many cancers and new advances point to how abnormal septin expression may contribute to the progression of cancer. In contrast to the RAS GTPases, which are frequently mutated and actively promote tumorigenesis, little is known about the occurrence and role of septin mutations in human cancers. Here, we review septin missense mutations that are currently in the Catalog of Somatic Mutations in Cancer (COSMIC) database. The majority of septin mutations occur in tumors of the large intestine, skin, endometrium and stomach. Over 25% of the annotated mutations in SEPT2, SEPT4, and SEPT9 belong to large intestine tumors. From all septins, SEPT9 and SEPT14 exhibit the highest mutation frequencies in skin, stomach and large intestine cancers. While septin mutations occur with frequencies lower than 3%, recurring mutations in several invariant and highly conserved amino acids are found across different septin paralogs and tumor types. Interestingly, a significant number of these mutations occur in the GTP-binding pocket and septin dimerization interfaces. Future studies may determine how these somatic mutations affect septin structure and function, whether they contribute to the progression of specific cancers and if they could serve as tumor-specific biomarkers.
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31
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Vargas-Muñiz JM, Juvvadi PR, Steinbach WJ. Forging the ring: from fungal septins' divergent roles in morphology, septation and virulence to factors contributing to their assembly into higher order structures. MICROBIOLOGY-SGM 2016; 162:1527-1534. [PMID: 27559018 DOI: 10.1099/mic.0.000359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Septins are a conserved family of GTP-binding proteins that are distributed across different lineages of the eukaryotes, with the exception of plants. Septins perform a myriad of functions in fungal cells, ranging from controlling morphogenetic events to contributing to host tissue invasion and virulence. One key attribute of the septins is their ability to assemble into heterooligomeric complexes that organizse into higher order structures. In addition to the established role of septins in the model budding yeast, Saccharomyces cerevisiae, their importance in other fungi recently emerges. While newer roles for septins are being uncovered in these fungi, the mechanism of how septins assemble into a complex and their regulation is only beginning to be comprehended. In this review, we summarize recent findings on the role of septins in different fungi and focus on how the septin complexes of different fungi are organized in vitro and in vivo. Furthermore, we discuss on how phosphorylation/dephosphorylation can serve as an important mechanism of septin complex assembly and regulation.
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Affiliation(s)
- Jose M Vargas-Muñiz
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Praveen R Juvvadi
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - William J Steinbach
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
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32
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Finnigan GC, Duvalyan A, Liao EN, Sargsyan A, Thorner J. Detection of protein-protein interactions at the septin collar in Saccharomyces cerevisiae using a tripartite split-GFP system. Mol Biol Cell 2016; 27:2708-25. [PMID: 27385335 PMCID: PMC5007091 DOI: 10.1091/mbc.e16-05-0337] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 06/30/2016] [Indexed: 01/22/2023] Open
Abstract
A tripartite split-GFP system faithfully reports the order of the subunits in septin hetero-octamers (and thus can serve as a “molecular ruler”), conversely yields little or no false signal even with very highly expressed cytosolic proteins, and detects authentic interactions of other cellular proteins that are bona fide septin-binding proteins. Various methods can provide a readout of the physical interaction between two biomolecules. A recently described tripartite split-GFP system has the potential to report by direct visualization via a fluorescence signal the intimate association of minimally tagged proteins expressed at their endogenous level in their native cellular milieu and can capture transient or weak interactions. Here we document the utility of this tripartite split-GFP system to assess in living cells protein–protein interactions in a dynamic cytoskeletal structure—the septin collar at the yeast bud neck. We show, first, that for septin–septin interactions, this method yields a robust signal whose strength reflects the known spacing between the subunits in septin filaments and thus serves as a “molecular ruler.” Second, the method yields little or no spurious signal even with highly abundant cytosolic proteins readily accessible to the bud neck (including molecular chaperone Hsp82 and glycolytic enzyme Pgk1). Third, using two proteins (Bni5 and Hsl1) that have been shown by other means to bind directly to septins at the bud neck in vivo, we validate that the tripartite split-GFP method yields the same conclusions and further insights about specificity. Finally, we demonstrate the capacity of this approach to uncover additional new information by examining whether three other proteins reported to localize to the bud neck (Nis1, Bud4, and Hof1) are able to interact physically with any of the subunits in the septin collar and, if so, with which ones.
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Affiliation(s)
- Gregory C Finnigan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Angela Duvalyan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Elizabeth N Liao
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Aspram Sargsyan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
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33
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Abstract
Polarized growth is critical for the development and maintenance of diverse organisms and tissues but particularly so in fungi, where nutrient uptake, communication, and reproduction all rely on cell asymmetries. To achieve polarized growth, fungi spatially organize both their cytosol and cortical membranes. Septins, a family of GTP-binding proteins, are key regulators of spatial compartmentalization in fungi and other eukaryotes. Septins form higher-order structures on fungal plasma membranes and are thought to contribute to the generation of cell asymmetries by acting as molecular scaffolds and forming diffusional barriers. Here we discuss the links between septins and polarized growth and consider molecular models for how septins contribute to cellular asymmetry in fungi.
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Affiliation(s)
- Anum Khan
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755;
| | - Molly McQuilken
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755;
| | - Amy S Gladfelter
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755;
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34
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Kaplan C, Yu C, Ewers H. Ashbya gossypii as a model system to study septin organization by single-molecule localization microscopy. Methods Cell Biol 2016; 136:161-82. [PMID: 27473909 DOI: 10.1016/bs.mcb.2016.04.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Heteromeric complexes of GTP-binding proteins from the septin family assemble into higher order structures that are essential for cell division in many organisms. The correct organization of the subunits into filaments, gauzes, and rings is the basis of septin function in this process. Electron microscopy and polarization fluorescence microscopy contributed greatly to the understanding of the dynamics and organization of such structures. However, both methods show technical limitations in resolution and specificity that do not allow the identification of individual septin complexes in assemblies in intact cells. Single-molecule localization-based fluorescence superresolution microscopy methods combine the resolution of cellular structures at the nanometer level with highest molecular specificity and excellent contrast. Here, we provide a protocol that enables the investigation of the organization of septin complexes in higher order structures in cells by combining advantageous features of the model organism Ashbya gossypii with single-molecule localization microscopy. Our assay is designed to investigate the general assembly mechanism of septin complexes in cells and is applicable to many cell types.
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Affiliation(s)
| | - C Yu
- ETH Zurich, Zurich, Switzerland
| | - H Ewers
- ETH Zurich, Zurich, Switzerland
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35
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Finnigan GC, Sterling SM, Duvalyan A, Liao EN, Sargsyan A, Garcia G, Nogales E, Thorner J. Coordinate action of distinct sequence elements localizes checkpoint kinase Hsl1 to the septin collar at the bud neck in Saccharomyces cerevisiae. Mol Biol Cell 2016; 27:2213-33. [PMID: 27193302 PMCID: PMC4945140 DOI: 10.1091/mbc.e16-03-0177] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 05/13/2016] [Indexed: 01/05/2023] Open
Abstract
A long-standing conundrum is resolved about the underlying sequence determinants and molecular mechanism responsible for the recruitment of the protein kinase Hsl1 (an indispensable component of the so-called “morphogenesis checkpoint”) exclusively to the septin collar at the bud neck. Passage through the eukaryotic cell cycle requires processes that are tightly regulated both spatially and temporally. Surveillance mechanisms (checkpoints) exert quality control and impose order on the timing and organization of downstream events by impeding cell cycle progression until the necessary components are available and undamaged and have acted in the proper sequence. In budding yeast, a checkpoint exists that does not allow timely execution of the G2/M transition unless and until a collar of septin filaments has properly assembled at the bud neck, which is the site where subsequent cytokinesis will occur. An essential component of this checkpoint is the large (1518-residue) protein kinase Hsl1, which localizes to the bud neck only if the septin collar has been correctly formed. Hsl1 reportedly interacts with particular septins; however, the precise molecular determinants in Hsl1 responsible for its recruitment to this cellular location during G2 have not been elucidated. We performed a comprehensive mutational dissection and accompanying image analysis to identify the sequence elements within Hsl1 responsible for its localization to the septins at the bud neck. Unexpectedly, we found that this targeting is multipartite. A segment of the central region of Hsl1 (residues 611–950), composed of two tandem, semiredundant but distinct septin-associating elements, is necessary and sufficient for binding to septin filaments both in vitro and in vivo. However, in addition to 611–950, efficient localization of Hsl1 to the septin collar in the cell obligatorily requires generalized targeting to the cytosolic face of the plasma membrane, a function normally provided by the C-terminal phosphatidylserine-binding KA1 domain (residues 1379–1518) in Hsl1 but that can be replaced by other, heterologous phosphatidylserine-binding sequences.
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Affiliation(s)
- Gregory C Finnigan
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Sarah M Sterling
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Angela Duvalyan
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Elizabeth N Liao
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Aspram Sargsyan
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Galo Garcia
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Eva Nogales
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 Life Sciences Division, Lawrence Berkeley National Laboratory, and Howard Hughes Medical Institute, Berkeley, CA 94720
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
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36
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Abstract
Septins are polymerizing eukaryotic proteins that play conserved roles in cell cortex organization and are essential in many cell types. How septin dynamics and protein-protein interactions determine their function at the plasma membrane remains a mystery. Here, we present a method for recapitulating septin polymerization and lipid interaction utilizing supported lipid bilayers to mimic the eukaryotic plasma membrane. Septins on supported lipid bilayers can be visualized with single-molecule sensitivity using total internal reflective fluorescence microscopy. Microscopy-based in vitro assays have revolutionized our understanding of actin, microtubules, and bacterial cytoskeletal systems, and will likely immediately advance our understanding of the septin proteins. As such, we hope that this technique will be adopted and widely utilized by those interested in uncovering septin properties and functions of septin interacting proteins.
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37
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Abstract
Primary cilia are cellular antennae that receive and transduce extracellular cues. These microtubule-rich structures are comprised of at least three distinct ciliary compartments: basal bodies, transition zone, and axoneme. Septins have been implicated in cilia function at the transition zone, but accumulating evidence suggests that they localize predominantly within the axoneme. Here, we describe three fixation conditions that preserve the substructure of primary cilia and demonstrate known ciliary proteins that localize to these distinct ciliary substructures. Finally, we show immunostaining and live microscopy methods to detect septins within the axoneme.
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Affiliation(s)
- M S Kim
- University of Toronto, Toronto, ON, Canada
| | - C D Froese
- University of Toronto, Toronto, ON, Canada
| | - H Xie
- University of Toronto, Toronto, ON, Canada
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38
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Ong K, Svitkina T, Bi E. Visualization of in vivo septin ultrastructures by platinum replica electron microscopy. Methods Cell Biol 2016; 136:73-97. [PMID: 27473904 PMCID: PMC5497467 DOI: 10.1016/bs.mcb.2016.03.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Septins are cytoskeletal proteins involved in diverse biological processes including cytokinesis, cell morphogenesis, motility, and ciliogenesis. Septins form various filamentous structures in vitro and in vivo, but the higher-order architecture of septin structures in vivo remains poorly defined. The best understood system in this respect is the budding yeast Saccharomyces cerevisiae, where septins form a ring structure that undergoes multiple stages of remodeling during the cell cycle. In this chapter, we describe a method for visualizing supramolecular septin structures in yeast at high spatial resolution using platinum replica electron microscopy. This approach can be applied to further understand the regulation of assembly and remodeling of septin higher-order structures, as well as the relationship between septin architecture and function.
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Affiliation(s)
- K. Ong
- University of Pennsylvania, Philadelphia, PA, United States
| | - T. Svitkina
- University of Pennsylvania, Philadelphia, PA, United States
| | - E. Bi
- University of Pennsylvania, Philadelphia, PA, United States
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39
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Renz C, Oeljeklaus S, Grinhagens S, Warscheid B, Johnsson N, Gronemeyer T. Identification of Cell Cycle Dependent Interaction Partners of the Septins by Quantitative Mass Spectrometry. PLoS One 2016; 11:e0148340. [PMID: 26871441 PMCID: PMC4752459 DOI: 10.1371/journal.pone.0148340] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 01/15/2016] [Indexed: 01/21/2023] Open
Abstract
The septins are a conserved family of GTP-binding proteins that, in the baker's yeast, assemble into a highly ordered array of filaments at the mother bud neck. These filaments undergo significant structural rearrangements during the cell cycle. We aimed at identifying key components that are involved in or regulate the transitions of the septins. By combining cell synchronization and quantitative affinity-purification mass-spectrometry, we performed a screen for specific interaction partners of the septins at three distinct stages of the cell cycle. A total of 83 interaction partners of the septins were assigned. Surprisingly, we detected DNA-interacting/nuclear proteins and proteins involved in ribosome biogenesis and protein synthesis predominantly present in alpha-factor arrested that do not display an assembled septin structure. Furthermore, two distinct sets of regulatory proteins that are specific for cells at S-phase with a stable septin collar or at mitosis with split septin rings were identified. Complementary methods like SPLIFF and immunoprecipitation allowed us to more exactly define the spatial and temporal characteristics of selected hits of the AP-MS screen.
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Affiliation(s)
- Christian Renz
- Ulm University, Department of Molecular Genetics and Cell Biology, Ulm, Germany
| | - Silke Oeljeklaus
- University of Freiburg, Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology and BIOSS Centre for Biological Signalling Studies, Freiburg, Germany
| | - Sören Grinhagens
- Ulm University, Department of Molecular Genetics and Cell Biology, Ulm, Germany
| | - Bettina Warscheid
- University of Freiburg, Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology and BIOSS Centre for Biological Signalling Studies, Freiburg, Germany
| | - Nils Johnsson
- Ulm University, Department of Molecular Genetics and Cell Biology, Ulm, Germany
| | - Thomas Gronemeyer
- Ulm University, Department of Molecular Genetics and Cell Biology, Ulm, Germany
- * E-mail:
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40
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Abstract
Cytokinesis is the final process in the cell cycle that physically divides one cell into two. In budding yeast, cytokinesis is driven by a contractile actomyosin ring (AMR) and the simultaneous formation of a primary septum, which serves as template for cell wall deposition. AMR assembly, constriction, primary septum formation and cell wall deposition are successive processes and tightly coupled to cell cycle progression to ensure the correct distribution of genetic material and cell organelles among the two rising cells prior to cell division. The role of the AMR in cytokinesis and the molecular mechanisms that drive AMR constriction and septation are the focus of current research. This review summarizes the recent progresses in our understanding of how budding yeast cells orchestrate the multitude of molecular mechanisms that control AMR driven cytokinesis in a spatio-temporal manner to achieve an error free cell division.
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41
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Stable Pseudohyphal Growth in Budding Yeast Induced by Synergism between Septin Defects and Altered MAP-kinase Signaling. PLoS Genet 2015; 11:e1005684. [PMID: 26640955 PMCID: PMC4671653 DOI: 10.1371/journal.pgen.1005684] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 10/29/2015] [Indexed: 11/19/2022] Open
Abstract
Upon nutrient limitation, budding yeasts like Saccharomyces cerevisiae can be induced to adopt alternate filament-like growth patterns called diploid pseudohyphal or invasive haploid growth. Here, we report a novel constitutive pseudohyphal growth state, sharing some characteristics with classic forms of filamentous growth, but differing in crucial aspects of morphology, growth conditions and genetic regulation. The constitutive pseudohyphal state is observed in fus3 mutants containing various septin assembly defects, which we refer to as sadF growth (septin assembly defect induced filamentation) to distinguish it from classic filamentation pathways. Similar to other filamentous states, sadF cultures comprise aggregated chains of highly elongated cells. Unlike the classic pathways, sadF growth occurs in liquid rich media, requiring neither starvation nor the key pseudohyphal proteins, Flo8p and Flo11p. Moreover sadF growth occurs in haploid strains of S288C genetic background, which normally cannot undergo pseudohyphal growth. The sadF cells undergo highly polarized bud growth during prolonged G2 delays dependent on Swe1p. They contain septin structures distinct from classical pseudo-hyphae and FM4-64 labeling at actively growing tips similar to the Spitzenkörper observed in true hyphal growth. The sadF growth state is induced by synergism between Kss1p-dependent signaling and septin assembly defects; mild disruption of mitotic septins activates Kss1p-dependent gene expression, which exacerbates the septin defects, leading to hyper-activation of Kss1p. Unlike classical pseudo-hyphal growth, sadF signaling requires Ste5, Ste4 and Ste18, the scaffold protein and G-protein β and γ subunits from the pheromone response pathway, respectively. A swe1 mutation largely abolished signaling, breaking the positive feedback that leads to amplification of sadF signaling. Taken together, our findings show that budding yeast can access a stable constitutive pseudohyphal growth state with very few genetic and regulatory changes. Many pathogenic fungi alternate between unicellular and multicellular filamentous forms, which is often critical for host-cell attachment, tissue invasion, and virulence. Certain strains of the nonpathogenic budding yeast Saccharomyces cerevisiae are also capable of forming invasive pseudohyphal filaments in nutrient poor conditions, which has served as a model system for the study of filamentous fungal pathogens. Here, we show that the most commonly used laboratory strain, S288c, previously known as being non-filamentous, can adopt a permanent stable pseudohyphal growth phase even under rich growth conditions. Although some features are shared, the degree of filamentation, genetic requirements, cell cycle, and mechanism of regulation are distinct from the previously described forms of filamentous growth. Stable pseudohyphal growth arises as a result of only two mutations, neither of which causes pseudohyphal growth on their own. One mutation causes subtle defects in the mechanism of cell separation (septation), which activate intracellular signaling pathways that slow cell division and promote filamentation. Normally this pathway is kept in check by a related signaling protein. However, when the inhibitor is also defective, activation of the filamentation signaling pathway exacerbates the septation defects, which causes a synergistic hyper-activation of pseudohyphal growth. These findings expand our understanding of fungal pathogenesis mechanisms at the molecular level.
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42
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Wu CF, Chiou JG, Minakova M, Woods B, Tsygankov D, Zyla TR, Savage NS, Elston TC, Lew DJ. Role of competition between polarity sites in establishing a unique front. eLife 2015; 4:e11611. [PMID: 26523396 PMCID: PMC4728132 DOI: 10.7554/elife.11611] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 11/01/2015] [Indexed: 01/15/2023] Open
Abstract
Polarity establishment in many cells is thought to occur via positive feedback that reinforces even tiny asymmetries in polarity protein distribution. Cdc42 and related GTPases are activated and accumulate in a patch of the cortex that defines the front of the cell. Positive feedback enables spontaneous polarization triggered by stochastic fluctuations, but as such fluctuations can occur at multiple locations, how do cells ensure that they make only one front? In polarizing cells of the model yeast Saccharomyces cerevisiae, positive feedback can trigger growth of several Cdc42 clusters at the same time, but this multi-cluster stage rapidly evolves to a single-cluster state, which then promotes bud emergence. By manipulating polarity protein dynamics, we show that resolution of multi-cluster intermediates occurs through a greedy competition between clusters to recruit and retain polarity proteins from a shared intracellular pool.
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Affiliation(s)
- Chi-Fang Wu
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
| | - Jian-Geng Chiou
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
| | - Maria Minakova
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Benjamin Woods
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
| | - Denis Tsygankov
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Trevin R Zyla
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
| | - Natasha S Savage
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Timothy C Elston
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Daniel J Lew
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
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43
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Booth EA, Vane EW, Dovala D, Thorner J. A Förster Resonance Energy Transfer (FRET)-based System Provides Insight into the Ordered Assembly of Yeast Septin Hetero-octamers. J Biol Chem 2015; 290:28388-28401. [PMID: 26416886 PMCID: PMC4653696 DOI: 10.1074/jbc.m115.683128] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Indexed: 12/21/2022] Open
Abstract
Prior studies in both budding yeast (Saccharomyces cerevisiae) and in human cells have established that septin protomers assemble into linear hetero-octameric rods with 2-fold rotational symmetry. In mitotically growing yeast cells, five septin subunits are expressed (Cdc3, Cdc10, Cdc11, Cdc12, and Shs1) and assemble into two types of rods that differ only in their terminal subunit: Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11 and Shs1-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Shs1. EM analysis has shown that, under low salt conditions, the Cdc11-capped rods polymerize end to end to form long paired filaments, whereas Shs1-capped rods form arcs, spirals, and rings. To develop a facile method to study septin polymerization in vitro, we exploited our previous work in which we generated septin complexes in which all endogenous cysteine (Cys) residues were eliminated by site-directed mutagenesis, except an introduced E294C mutation in Cdc11 in these experiments. Mixing samples of a preparation of such single-Cys containing Cdc11-capped rods that have been separately derivatized with organic dyes that serve as donor and acceptor, respectively, for FRET provided a spectroscopic method to monitor filament assembly mediated by Cdc11-Cdc11 interaction and to measure its affinity under specified conditions. Modifications of this same FRET scheme also allow us to assess whether Shs1-capped rods are capable of end to end association either with themselves or with Cdc11-capped rods. This FRET approach also was used to follow the binding to septin filaments of a septin-interacting protein, the type II myosin-binding protein Bni5.
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Affiliation(s)
- Elizabeth A Booth
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202
| | - Eleanor W Vane
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202
| | - Dustin Dovala
- Program in Microbial Pathogenesis and Host Defense, Department of Microbiology and Immunology, University of California School of Medicine, San Francisco, California 94158-2200
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics, and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202.
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44
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Finnigan GC, Takagi J, Cho C, Thorner J. Comprehensive Genetic Analysis of Paralogous Terminal Septin Subunits Shs1 and Cdc11 in Saccharomyces cerevisiae. Genetics 2015; 200:821-41. [PMID: 25971665 PMCID: PMC4512546 DOI: 10.1534/genetics.115.176495] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/08/2015] [Indexed: 02/07/2023] Open
Abstract
Septins are a family of GTP-binding proteins considered to be cytoskeletal elements because they self-assemble into filaments and other higher-order structures in vivo. In budding yeast, septins establish a diffusion barrier at the bud neck between a mother and daughter cell, promote membrane curvature there, and serve as a scaffold to recruit other proteins to the site of cytokinesis. However, the mechanism by which any septin engages a partner protein has been unclear. The two most related and recently evolved subunits appear to be Cdc11 and Shs1, and the basic building blocks for assembling septin structures are hetero-octameric rods (Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11 and Shs1-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Shs1). Loss of Cdc11 is not normally tolerated, whereas cells lacking Shs1 do not appear grossly abnormal. We established several different sensitized genetic backgrounds wherein Shs1 is indispensable, which allowed us to carry out the first comprehensive and detailed genetic analysis of Shs1 in vivo. Our analysis revealed several novel insights, including: (i) the sole portion of Shs1 essential for its function is a predicted coiled-coil-forming segment in its C-terminal extension (CTE); (ii) the CTE of Cdc11 shares this function; (iii) this role for the CTEs of Cdc11 and Shs1 is quite distinct from that of the CTEs of Cdc3 and Cdc12; and (iv) heterotypic Cdc11 and Shs1 junctions likely occur in vivo.
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Affiliation(s)
- Gregory C Finnigan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202
| | - Julie Takagi
- Department of Microbiology and Immunology, University of California School of Medicine, San Francisco, California 94158-2200
| | - Christina Cho
- Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202 Department of Microbiology and Immunology, University of California School of Medicine, San Francisco, California 94158-2200 Harvard School of Dental Medicine, Boston, Massachusetts 02115
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45
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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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Roelants FM, Su BM, von Wulffen J, Ramachandran S, Sartorel E, Trott AE, Thorner J. Protein kinase Gin4 negatively regulates flippase function and controls plasma membrane asymmetry. ACTA ACUST UNITED AC 2015; 208:299-311. [PMID: 25646086 PMCID: PMC4315245 DOI: 10.1083/jcb.201410076] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In yeast, the protein kinase Gin4 locally controls plasma membrane lipid asymmetry, which is necessary for optimal cytokinesis. Plasma membrane function requires distinct leaflet lipid compositions. Two of the P-type ATPases (flippases) in yeast, Dnf1 and Dnf2, translocate aminoglycerophospholipids from the outer to the inner leaflet, stimulated via phosphorylation by cortically localized protein kinase Fpk1. By monitoring Fpk1 activity in vivo, we found that Fpk1 was hyperactive in cells lacking Gin4, a protein kinase previously implicated in septin collar assembly. Gin4 colocalized with Fpk1 at the cortical site of future bud emergence and phosphorylated Fpk1 at multiple sites, which we mapped. As judged by biochemical and phenotypic criteria, a mutant (Fpk111A), in which 11 sites were mutated to Ala, was hyperactive, causing increased inward transport of phosphatidylethanolamine. Thus, Gin4 is a negative regulator of Fpk1 and therefore an indirect negative regulator of flippase function. Moreover, we found that decreasing flippase function rescued the growth deficiency of four different cytokinesis mutants, which suggests that the primary function of Gin4 is highly localized control of membrane lipid asymmetry and is necessary for optimal cytokinesis.
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Affiliation(s)
- Françoise M Roelants
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Brooke M Su
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Joachim von Wulffen
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Subramaniam Ramachandran
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Elodie Sartorel
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Amy E Trott
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
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47
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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: 89] [Impact Index Per Article: 8.9] [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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48
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Wang N, Wang M, Zhu YH, Grosel TW, Sun D, Kudryashov DS, Wu JQ. The Rho-GEF Gef3 interacts with the septin complex and activates the GTPase Rho4 during fission yeast cytokinesis. Mol Biol Cell 2014; 26:238-55. [PMID: 25411334 PMCID: PMC4294672 DOI: 10.1091/mbc.e14-07-1196] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Rho GTPases, activated by Rho guanine nucleotide exchange factors (GEFs), are conserved molecular switches for signal transductions that regulate diverse cellular processes, including cell polarization and cytokinesis. The fission yeast Schizosaccharomyces pombe has six Rho GTPases (Cdc42 and Rho1-Rho5) and seven Rho GEFs (Scd1, Rgf1-Rgf3, and Gef1-Gef3). The GEFs for Rho2-Rho5 have not been unequivocally assigned. In particular, Gef3, the smallest Rho GEF, was barely studied. Here we show that Gef3 colocalizes with septins at the cell equator. Gef3 physically interacts with septins and anillin Mid2 and depends on them to localize. Gef3 coprecipitates with GDP-bound Rho4 in vitro and accelerates nucleotide exchange of Rho4, suggesting that Gef3 is a GEF for Rho4. Consistently, Gef3 and Rho4 are in the same genetic pathways to regulate septum formation and/or cell separation. In gef3∆ cells, the localizations of two potential Rho4 effectors--glucanases Eng1 and Agn1--are abnormal, and active Rho4 level is reduced, indicating that Gef3 is involved in Rho4 activation in vivo. Moreover, overexpression of active Rho4 or Eng1 rescues the septation defects of mutants containing gef3∆. Together our data support that Gef3 interacts with the septin complex and activates Rho4 GTPase as a Rho GEF for septation in fission yeast.
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Affiliation(s)
| | - Mo Wang
- Department of Molecular Genetics
| | | | | | | | | | - Jian-Qiu Wu
- Department of Molecular Genetics Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, OH 43210
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49
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Sellin ME, Stenmark S, Gullberg M. Cell type-specific expression of SEPT3-homology subgroup members controls the subunit number of heteromeric septin complexes. Mol Biol Cell 2014; 25:1594-607. [PMID: 24648497 PMCID: PMC4019491 DOI: 10.1091/mbc.e13-09-0553] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Heteromeric septin complexes serve as building blocks of filaments that organize the cortex of fungal and animal cells. This report addresses determinants that direct hetero-oligomerization of the 13 septin paralogues of mammals. It shows that three distinct septins direct assembly of tissue-specific heterotetramers. Septins are filament-forming proteins important for organizing the cortex of animal and fungal cells. In mammals, 13 septin paralogues were recently shown to assemble into core heterohexamer and heterooctamer complexes, which serve as building blocks for apolar filamentous structures that differ among cell types. To determine how tissue-specific septin paralogue expression may shape core heteromer repertoires and thereby modulate properties of septin filaments, we devised protocols to analyze native septin heteromers with distinct numbers of subunits. Our evidence based on genetically manipulated human cells supports and extends recent concepts of homology subgroup–restricted assembly into distinct categories of apolar heterohexamers and heterooctamers. We also identify a category of tetramers that have a subunit composition equivalent to an octameric building block. These atypical tetramers are prevalent in lymphocytes and neural tissues, in which octamers are abundant but hexamers are rare. Our results can be explained by tissue-specific expression of SEPT3 subgroup members: SEPT3, SEPT9, and SEPT12. These serve as cognate subunits in either heterooctamers or atypical tetramers but exhibit different preferences in various tissues. The identified tissue-specific repertoires of septin heteromers provide insights into how higher-order septin structures with differential properties and stabilities may form in diverse animal cell types.
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Affiliation(s)
- Mikael E Sellin
- Department of Molecular Biology, Umeå University, SE-901 87 Umeå, SwedenInstitute of Microbiology, D-BIOL, ETH Zürich, 8093 Zürich, Switzerland
| | - Sonja Stenmark
- Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Martin Gullberg
- Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
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50
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Phosphoregulation of Nap1 plays a role in septin ring dynamics and morphogenesis in Candida albicans. mBio 2014; 5:e00915-13. [PMID: 24496790 PMCID: PMC3950511 DOI: 10.1128/mbio.00915-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Nap1 has long been identified as a potential septin regulator in yeasts. However, its function and regulation remain poorly defined. Here, we report functional characterization of Nap1 in the human-pathogenic fungus Candida albicans. We find that deletion of NAP1 causes constitutive filamentous growth and changes of septin dynamics. We present evidence that Nap1’s cellular localization and function are regulated by phosphorylation. Phos-tag gel electrophoresis revealed that Nap1 phosphorylation is cell cycle dependent, exhibiting the lowest level around the time of bud emergence. Mass spectrometry identified 10 phosphoserine and phosphothreonine residues in a cluster near the N terminus, and mutation of these residues affected Nap1’s localization to the septin ring and cellular function. Nap1 phosphorylation involves two septin ring-associated kinases, Cla4 and Gin4, and its dephosphorylation occurs at the septin ring in a manner dependent on the phosphatases PP2A and Cdc14. Furthermore, the nap1Δ/Δ mutant and alleles carrying mutations of the phosphorylation sites exhibited greatly reduced virulence in a mouse model of systemic candidiasis. Together, our findings not only provide new mechanistic insights into Nap1’s function and regulation but also suggest the potential to target Nap1 in future therapeutic design. Septins are conserved filament-forming GTPases involved in a wide range of cellular events, such as cytokinesis, exocytosis, and morphogenesis. In Candida albicans, the most prevalent human fungal pathogen, septin functions are indispensable for its virulence. However, the molecular mechanisms by which septin structures are regulated are poorly understood. In this study, we deleted NAP1, a gene encoding a putative septin regulator, in C. albicans and found that cells lacking NAP1 showed abnormalities in morphology, invasive growth, and septin ring dynamics. We identified a conserved N-terminal phosphorylation cluster on Nap1 and demonstrated that phosphorylation at these sites regulates Nap1 localization and function. Importantly, deletion of NAP1 or mutation in the N-terminal phosphorylation cluster strongly reduced the virulence of C. albicans in a mouse model of systemic infection. Thus, this study not only provides mechanistic insights into septin regulation but also suggests Nap1 as a potential antifungal target.
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