1
|
Connors CQ, Mauro MS, Wiles JT, Countryman AD, Martin SL, Lacroix B, Shirasu-Hiza M, Dumont J, Kasza KE, Davies TR, Canman JC. Germ fate determinants protect germ precursor cell division by reducing septin and anillin levels at the cell division plane. Mol Biol Cell 2024; 35:ar94. [PMID: 38696255 DOI: 10.1091/mbc.e24-02-0096-t] [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] [Indexed: 05/04/2024] Open
Abstract
Animal cell cytokinesis, or the physical division of one cell into two, is thought to be driven by constriction of an actomyosin contractile ring at the division plane. The mechanisms underlying cell type-specific differences in cytokinesis remain unknown. Germ cells are totipotent cells that pass genetic information to the next generation. Previously, using formincyk-1(ts) mutant Caenorhabditis elegans 4-cell embryos, we found that the P2 germ precursor cell is protected from cytokinesis failure and can divide with greatly reduced F-actin levels at the cell division plane. Here, we identified two canonical germ fate determinants required for P2-specific cytokinetic protection: PIE-1 and POS-1. Neither has been implicated previously in cytokinesis. These germ fate determinants protect P2 cytokinesis by reducing the accumulation of septinUNC-59 and anillinANI-1 at the division plane, which here act as negative regulators of cytokinesis. These findings may provide insight into the regulation of cytokinesis in other cell types, especially in stem cells with high potency.
Collapse
Affiliation(s)
- Caroline Q Connors
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| | - Michael S Mauro
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| | - J Tristian Wiles
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Andrew D Countryman
- Department of Biomedical Engineering, Columbia University, New York, NY 10027
| | - Sophia L Martin
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| | - Benjamin Lacroix
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
- Université de Montpellier, CNRS, Centre de Recherche en Biologie Cellulaire de Montpellier, UMR 5237 Montpellier, France
| | - Mimi Shirasu-Hiza
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032
| | - Julien Dumont
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Karen E Kasza
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Timothy R Davies
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
- Department of Biosciences, Durham University, Durham DH1 3LE, UK
| | - Julie C Canman
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Quiroz LF, Ciosek T, Grogan H, McKeown PC, Spillane C, Brychkova G. Unravelling the Transcriptional Response of Agaricus bisporus under Lecanicillium fungicola Infection. Int J Mol Sci 2024; 25:1283. [PMID: 38279283 PMCID: PMC10815960 DOI: 10.3390/ijms25021283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/14/2024] [Accepted: 01/18/2024] [Indexed: 01/28/2024] Open
Abstract
Mushrooms are a nutritionally rich and sustainably-produced food with a growing global market. Agaricus bisporus accounts for 11% of the total world mushroom production and it is the dominant species cultivated in Europe. It faces threats from pathogens that cause important production losses, including the mycoparasite Lecanicillium fungicola, the causative agent of dry bubble disease. Through quantitative real-time polymerase chain reaction (qRT-PCR), we determine the impact of L. fungicola infection on the transcription patterns of A. bisporus genes involved in key cellular processes. Notably, genes related to cell division, fruiting body development, and apoptosis exhibit dynamic transcriptional changes in response to infection. Furthermore, A. bisporus infected with L. fungicola were found to accumulate increased levels of reactive oxygen species (ROS). Interestingly, the transcription levels of genes involved in the production and scavenging mechanisms of ROS were also increased, suggesting the involvement of changes to ROS homeostasis in response to L. fungicola infection. These findings identify potential links between enhanced cell proliferation, impaired fruiting body development, and ROS-mediated defence strategies during the A. bisporus (host)-L. fungicola (pathogen) interaction, and offer avenues for innovative disease control strategies and improved understanding of fungal pathogenesis.
Collapse
Affiliation(s)
- Luis Felipe Quiroz
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland; (L.F.Q.); (C.S.)
| | - Tessa Ciosek
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland; (L.F.Q.); (C.S.)
| | - Helen Grogan
- Teagasc, Horticulture Development Department, Ashtown Research Centre, D15 KN3K Dublin, Ireland;
| | - Peter C. McKeown
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland; (L.F.Q.); (C.S.)
| | - Charles Spillane
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland; (L.F.Q.); (C.S.)
| | - Galina Brychkova
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland; (L.F.Q.); (C.S.)
| |
Collapse
|
4
|
Grupp B, Denkhaus L, Gerhardt S, Vögele M, Johnsson N, Gronemeyer T. The structure of a tetrameric septin complex reveals a hydrophobic element essential for NC-interface integrity. Commun Biol 2024; 7:48. [PMID: 38184752 PMCID: PMC10771490 DOI: 10.1038/s42003-023-05734-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 12/20/2023] [Indexed: 01/08/2024] Open
Abstract
The septins of the yeast Saccharomyces cerevisiae assemble into hetero-octameric rods by alternating interactions between neighboring G-domains or N- and C-termini, respectively. These rods polymerize end to end into apolar filaments, forming a ring beneath the prospective new bud that expands during the cell cycle into an hourglass structure. The hourglass finally splits during cytokinesis into a double ring. Understanding these transitions as well as the plasticity of the higher order assemblies requires a detailed knowledge of the underlying structures. Here we present the first X-ray crystal structure of a tetrameric Shs1-Cdc12-Cdc3-Cdc10 complex at a resolution of 3.2 Å. Close inspection of the NC-interfaces of this and other septin structures reveals a conserved contact motif that is essential for NC-interface integrity of yeast and human septins in vivo and in vitro. Using the tetrameric structure in combination with AlphaFold-Multimer allowed us to propose a model of the octameric septin rod.
Collapse
Affiliation(s)
- Benjamin Grupp
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Lukas Denkhaus
- Institute of Biochemistry, Albert-Ludwigs University, Freiburg, Germany
| | - Stefan Gerhardt
- Institute of Biochemistry, Albert-Ludwigs University, Freiburg, Germany
| | - Matthis Vögele
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Nils Johnsson
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Thomas Gronemeyer
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany.
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Müller J, Furlan M, Settele D, Grupp B, Johnsson N. Transient septin sumoylation steers a Fir1-Skt5 protein complex between the split septin ring. J Cell Biol 2024; 223:e202301027. [PMID: 37938157 PMCID: PMC10631487 DOI: 10.1083/jcb.202301027] [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: 01/06/2023] [Revised: 10/05/2023] [Accepted: 10/17/2023] [Indexed: 11/09/2023] Open
Abstract
Ubiquitylation and phosphorylation control composition and architecture of the cell separation machinery in yeast and other eukaryotes. The significance of septin sumoylation on cell separation remained an enigma. Septins form an hourglass structure at the bud neck of yeast cells that transforms into a split septin double ring during mitosis. We discovered that sumoylated septins recruit the cytokinesis checkpoint protein Fir1 to the peripheral side of the septin hourglass just before its transformation into the double-ring configuration. As this transition occurs, Fir1 is released from the septins and seamlessly relocates between the split septin rings through synchronized binding to the scaffold Spa2. Fir1 binds and carries the membrane-bound Skt5 on its route to the division plane where the Fir1-Skt5 complex serves as receptor for chitin synthase III.
Collapse
Affiliation(s)
- Judith Müller
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Monique Furlan
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - David Settele
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Benjamin Grupp
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Nils Johnsson
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| |
Collapse
|
7
|
Wang K, Okada H, Wloka C, Bi E. Unraveling the mechanisms and evolution of a two-domain module in IQGAP proteins for controlling eukaryotic cytokinesis. Cell Rep 2023; 42:113510. [PMID: 38041816 PMCID: PMC10809011 DOI: 10.1016/j.celrep.2023.113510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 08/17/2023] [Accepted: 11/13/2023] [Indexed: 12/04/2023] Open
Abstract
The IQGAP family of proteins plays a crucial role in cytokinesis across diverse organisms, but the underlying mechanisms are not fully understood. In this study, we demonstrate that IQGAPs in budding yeast, fission yeast, and human cells use a two-domain module to regulate their localization as well as the assembly and disassembly of the actomyosin ring during cytokinesis. Strikingly, the calponin homology domains (CHDs) in these IQGAPs bind to distinct cellular F-actin structures with varying specificity, whereas the non-conserved domains immediately downstream of the CHDs in these IQGAPs all target the division site, but differ in timing, localization strength, and binding partners. We also demonstrate that human IQGAP3 acts in parallel to septins and myosin-IIs to mediate the role of anillin in cytokinesis. Collectively, our findings highlight the two-domain mechanism by which IQGAPs regulate cytokinesis in distantly related organisms as well as their evolutionary conservation and divergence.
Collapse
Affiliation(s)
- Kangji Wang
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Hiroki Okada
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Carsten Wloka
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA; Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, A Corporate Member of Freie Universität, Humboldt-University, The Berlin Institute of Health, Berlin, Germany
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA.
| |
Collapse
|
8
|
Connors CQ, Mauro MS, Tristian Wiles J, Countryman AD, Martin SL, Lacroix B, Shirasu-Hiza M, Dumont J, Kasza KE, Davies TR, Canman JC. Germ fate determinants protect germ precursor cell division by restricting septin and anillin levels at the division plane. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.17.566773. [PMID: 38014027 PMCID: PMC10680835 DOI: 10.1101/2023.11.17.566773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Animal cell cytokinesis, or the physical division of one cell into two, is thought to be driven by constriction of an actomyosin contractile ring at the division plane. The mechanisms underlying cell type-specific differences in cytokinesis remain unknown. Germ cells are totipotent cells that pass genetic information to the next generation. Previously, using formin cyk-1 (ts) mutant C. elegans embryos, we found that the P2 germ precursor cell is protected from cytokinesis failure and can divide without detectable F-actin at the division plane. Here, we identified two canonical germ fate determinants required for P2-specific cytokinetic protection: PIE-1 and POS-1. Neither has been implicated previously in cytokinesis. These germ fate determinants protect P2 cytokinesis by reducing the accumulation of septin UNC-59 and anillin ANI-1 at the division plane, which here act as negative regulators of cytokinesis. These findings may provide insight into cytokinetic regulation in other cell types, especially in stem cells with high potency.
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
Wang GZ, Yang LH, Gao C. SEPTIN3 Promotes Progression of Triple-Negative Breast Cancer via Activating Wnt Pathway. Int J Gen Med 2023; 16:4155-4164. [PMID: 37720177 PMCID: PMC10505033 DOI: 10.2147/ijgm.s419827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 09/05/2023] [Indexed: 09/19/2023] Open
Abstract
Background There is a lack of targeted therapies for triple-negative breast cancer (TNBC), necessitating the search for novel targets. Patients with TNBC exhibit elevated expression of neuron-specific septin-3 (SEPTIN3), leading to poor prognosis. This study aimed to investigate the modulation of SEPTIN3 expression in TNBC cells. Methods The relative expression levels of SEPTIN3 in TNBC tissues and cell lines were determined using Western blotting and qRT-PCR. We generated lentivirally transduced TNBC cell lines so such that SEPTIN3 was overexpressed or knocked down. Next, the effect of SEPTIN3 on the biological behavior of TNBC cells was detected using a series of functional assays, including CCK8, colony formation, scratch, and transwell assays. We monitored the tumorigenicity of SEPTIN3 overexpressed cells and performed Ki-67 immunostaining in mice. The mechanism mediated by SEPTIN3 was studied using functional enrichment analysis and Western blotting. Results Protein and mRNA expression levels of SEPTIN3 were observed to be increased in TNBC tissues and cell lines. SEPTIN3 knockdown reduced cell growth, invasion, and migration, whereas SEPTIN3 overexpression exerted the opposite effects. SEPTIN3 was observed to favor cell growth and tumorigenicity in vivo. In addition, SEPTIN3 promoted TNBC cell aggressiveness and proliferation via activation of the Wnt signaling pathway. Conclusion SEPTIN3 emerged as an oncogene that accelerates tumor progression by regulating the Wnt signaling pathway.
Collapse
Affiliation(s)
- Guo-Zhou Wang
- Department of Breast Tumor Surgery, Huangshi Central Hospital, Affiliated Hospital of Hubei Polytechnic University, Edong Healthcare Group, Huangshi, Hubei Province, 435000, People’s Republic of China
| | - Li-Hua Yang
- Department of Breast Tumor Surgery, Huangshi Central Hospital, Affiliated Hospital of Hubei Polytechnic University, Edong Healthcare Group, Huangshi, Hubei Province, 435000, People’s Republic of China
| | - Chao Gao
- Department of General Practitioner, Huangshi Central Hospital, Affiliated Hospital of Hubei Polytechnic University, Edong Healthcare Group, Huangshi, Hubei Province, 435000, People’s Republic of China
| |
Collapse
|
11
|
Kim J, Mooren OL, Onken MD, Cooper JA. Septin and actin contributions to endothelial cell-cell junctions and monolayer integrity. Cytoskeleton (Hoboken) 2023; 80:228-241. [PMID: 36205643 PMCID: PMC10079785 DOI: 10.1002/cm.21732] [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: 07/08/2022] [Revised: 10/02/2022] [Accepted: 10/04/2022] [Indexed: 11/10/2022]
Abstract
Septins in endothelial cells (ECs) have important roles supporting the integrity of the endothelial monolayer. Cell-cell junctions in EC monolayers are highly dynamic, with continuous retractions and protrusions. Depletion of septins in ECs leads to disruption of cell-cell junctions, which are composed of VE-cadherin and other junctional proteins. In EC monolayers, septins are concentrated at the plasma membrane at sites of cell-cell contact, in curved- and scallop-shaped patterns. These membrane-associated septin accumulations are located in regions of positive membrane curvature, and those regions are often associated with and immediately adjacent to actin-rich protrusions with negative membrane curvature. EC septins associate directly with plasma membrane lipids, based on findings with site-specific mutations of septins in ECs, which is consistent with biochemical and cell biological studies in other systems. Loss of septins leads to disruption of the EC monolayer, and gaps form between cells. The number and breadth of cell-cell contacts and junctions decreases, and the number and frequency of retractions, ruffles, and protrusions at cell edges also decreases. In addition, loss of septins leads to decreased amounts of F-actin at the cortical membrane, along with increased amounts of F-actin in stress fibers of the cytoplasm. Endothelial monolayer disruption from loss of septins is also associated with decreased transendothelial electric resistance (TEER) and increased levels of transendothelial migration (TEM) by immune and cancer cells, owing to the gaps in the monolayer. A current working model is that assembly of septin filaments at regions of positive membrane curvature contributes to a mechanical footing or base for actin-based protrusive forces generated at adjoining regions of the membrane. Specific molecular interactions between the septin and actin components of the cytoskeleton may also be important contributors. Regulators of actin assembly may promote and support the assembly of septin filaments at the membrane, as part of a molecular feedback loop between the assembly of septin and actin filaments.
Collapse
Affiliation(s)
- Joanna Kim
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Olivia L Mooren
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Michael D Onken
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - John A Cooper
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| |
Collapse
|
12
|
Perry JA, Werner ME, Rivenbark L, Maddox AS. Caenorhabditis elegans septins contribute to the development and structure of the oogenic germline. Cytoskeleton (Hoboken) 2023; 80:215-227. [PMID: 37265173 PMCID: PMC10524836 DOI: 10.1002/cm.21763] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 04/27/2023] [Accepted: 05/04/2023] [Indexed: 06/03/2023]
Abstract
Oocytes must be exceptionally large cells in order to support embryonic development. Throughout animal phylogeny, a specialized cell called a syncytium, wherein many nuclei share a continuous cytoplasm, achieves oogenesis. The syncytial nature of germline architecture is key to its function and depends on conserved components of the cortical cytoskeleton. Septins form non-polar cytoskeletal polymers that associate with membranes. In the syncytial germline of the nematode Caenorhabditis elegans, septins are highly enriched on the cortex and generally required for fertility, but the role of septins in the germline is poorly understood. We report that the C. elegans septins, UNC-59 and UNC-61, are important for germline extension during development, the maintenance of its syncytial architecture, and production of oocytes. While much of our findings substantiate the idea that the two C. elegans septins act together, we also found evidence that they have distinct functions. Loss of UNC-61 perturbed germline extension during germline development, while the loss of UNC-59 function severely affected germline architecture in adult hermaphrodites. Consultation of clustering results from a large-scale high-throughput screen suggested that septins are involved in germ cell proliferation and/or differentiation. In sum, our findings implicate a conserved cytoskeletal component in the complex architecture of a germline syncytium.
Collapse
Affiliation(s)
- Jenna A Perry
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Michael E Werner
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Larry Rivenbark
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Amy Shaub Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| |
Collapse
|
13
|
González-Rubio G, Martín H, Molina M. The Mitogen-Activated Protein Kinase Slt2 Promotes Asymmetric Cell Cycle Arrest and Reduces TORC1-Sch9 Signaling in Yeast Lacking the Protein Phosphatase Ptc1. Microbiol Spectr 2023; 11:e0524922. [PMID: 37042757 PMCID: PMC10269544 DOI: 10.1128/spectrum.05249-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 03/18/2023] [Indexed: 04/13/2023] Open
Abstract
Mitogen-activated protein kinase (MAPK) pathways regulate essential processes in eukaryotes. However, since uncontrolled activation of these cascades has deleterious effects, precise negative regulation of signaling flow through them, mainly executed by protein phosphatases, is crucial. Previous studies showed that the absence of Ptc1 protein phosphatase results in the upregulation of the MAPK of the cell wall integrity (CWI) pathway, Slt2, and numerous functional defects in Saccharomyces cerevisiae, including a failure to undergo cell separation under heat stress. In this study, we demonstrate that multibudded ptc1Δ cells also exhibit impaired mitochondrial inheritance and that excessive Slt2 kinase activity is responsible for their growth deficiency and daughter-specific G1 cell cycle arrest, as well as other physiological alterations, namely, mitochondrial hyperpolarization and reactive oxygen species (ROS) accumulation. We bring to light the fact that sustained Slt2 kinase activity inhibits signaling through the Sch9 branch of the TORC1 pathway in ptc1Δ cells, leading to increased autophagy. After cytokinesis, septin rings asymmetrically disassembled in ptc1Δ multibudded cells, abnormally remaining at the daughter cell side and eventually relocalizing at the daughter cell periphery, where they occasionally colocalized with the autophagic protein Atg9. Finally, we show that the inability of ptc1Δ cells to undergo cell separation is not due to a failure in the regulation of Ace2 and morphogenesis (RAM) pathway, since the transcription factor Ace2 correctly enters the daughter cell nuclei. However, the Ace2-regulated endochitinase Cts1 did not localize to the septum, preventing the proper degradation of this structure. IMPORTANCE This study provides further evidence that the cell cycle is regulated by complex signaling networks whose purpose is to guarantee a robust response to environmental threats. Using the S. cerevisiae eukaryotic model, we show that, under the stress conditions that activate the CWI MAPK pathway, the absence of the protein phosphatase Ptc1 renders Slt2 hyperactive, leading to numerous physiological alterations, including perturbed mitochondrial inheritance, oxidative stress, changes in septin dynamics, increased autophagy, TORC1-Sch9 inhibition, and ultimately cell cycle arrest and the failure of daughter cells to separate, likely due to the absence of key degradative enzymes at the septum. These results imply novel roles for the CWI pathway and unravel new cell cycle-regulatory controls that operate beyond the RAM pathway, arresting buds in G1 without compromising further division rounds in the mother cell.
Collapse
Affiliation(s)
- Gema González-Rubio
- Departamento de Microbiología y Parasitología. Facultad de Farmacia. Instituto Ramón y Cajal de Investigaciones Sanitarias, Universidad Complutense de Madrid, Madrid, Spain
| | - Humberto Martín
- Departamento de Microbiología y Parasitología. Facultad de Farmacia. Instituto Ramón y Cajal de Investigaciones Sanitarias, Universidad Complutense de Madrid, Madrid, Spain
| | - María Molina
- Departamento de Microbiología y Parasitología. Facultad de Farmacia. Instituto Ramón y Cajal de Investigaciones Sanitarias, Universidad Complutense de Madrid, Madrid, Spain
| |
Collapse
|
14
|
Benoit B, Poüs C, Baillet A. Septins as membrane influencers: direct play or in association with other cytoskeleton partners. Front Cell Dev Biol 2023; 11:1112319. [PMID: 36875762 PMCID: PMC9982393 DOI: 10.3389/fcell.2023.1112319] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 01/23/2023] [Indexed: 02/19/2023] Open
Abstract
The cytoskeleton comprises three polymerizing structures that have been studied for a long time, actin microfilaments, microtubules and intermediate filaments, plus more recently investigated dynamic assemblies like septins or the endocytic-sorting complex required for transport (ESCRT) complex. These filament-forming proteins control several cell functions through crosstalks with each other and with membranes. In this review, we report recent works that address how septins bind to membranes, and influence their shaping, organization, properties and functions, either by binding to them directly or indirectly through other cytoskeleton elements.
Collapse
Affiliation(s)
- Béatrice Benoit
- INSERM UMR-S 1193, UFR de Pharmacie, University Paris-Saclay, Orsay, France
| | - Christian Poüs
- INSERM UMR-S 1193, UFR de Pharmacie, University Paris-Saclay, Orsay, France.,Laboratoire de Biochimie-Hormonologie, Hôpital Antoine Béclère, AP-HP, Hôpitaux Universitaires Paris-Saclay, Clamart, France
| | - Anita Baillet
- INSERM UMR-S 1193, UFR de Pharmacie, University Paris-Saclay, Orsay, France
| |
Collapse
|