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Montrose K, Lac DT, Burnetti AJ, Tong K, Bozdag GO, Hukkanen M, Ratcliff WC, Saarikangas J. Proteostatic tuning underpins the evolution of novel multicellular traits. Sci Adv 2024; 10:eadn2706. [PMID: 38457507 PMCID: PMC10923498 DOI: 10.1126/sciadv.adn2706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 02/06/2024] [Indexed: 03/10/2024]
Abstract
The evolution of multicellularity paved the way for the origin of complex life on Earth, but little is known about the mechanistic basis of early multicellular evolution. Here, we examine the molecular basis of multicellular adaptation in the multicellularity long-term evolution experiment (MuLTEE). We demonstrate that cellular elongation, a key adaptation underpinning increased biophysical toughness and organismal size, is convergently driven by down-regulation of the chaperone Hsp90. Mechanistically, Hsp90-mediated morphogenesis operates by destabilizing the cyclin-dependent kinase Cdc28, resulting in delayed mitosis and prolonged polarized growth. Reinstatement of Hsp90 or Cdc28 expression resulted in shortened cells that formed smaller groups with reduced multicellular fitness. Together, our results show how ancient protein folding systems can be tuned to drive rapid evolution at a new level of biological individuality by revealing novel developmental phenotypes.
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Affiliation(s)
- Kristopher Montrose
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Dung T. Lac
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Anthony J. Burnetti
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Kai Tong
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Interdisciplinary Graduate Program in Quantitative Biosciences (QBioS), Georgia Institute of Technology, Atlanta, GA, USA
| | - G. Ozan Bozdag
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Mikaela Hukkanen
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - William C. Ratcliff
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Juha Saarikangas
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
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2
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Montrose K, Lac DT, Burnetti AJ, Tong K, Ozan Bozdag G, Hukkanen M, Ratcliff WC, Saarikangas J. Proteostatic tuning underpins the evolution of novel multicellular traits. bioRxiv 2024:2023.05.31.543183. [PMID: 37333256 PMCID: PMC10274739 DOI: 10.1101/2023.05.31.543183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
The evolution of multicellularity paved the way for the origin of complex life on Earth, but little is known about the mechanistic basis of early multicellular evolution. Here, we examine the molecular basis of multicellular adaptation in the Multicellularity Long Term Evolution Experiment (MuLTEE). We demonstrate that cellular elongation, a key adaptation underpinning increased biophysical toughness and organismal size, is convergently driven by downregulation of the chaperone Hsp90. Mechanistically, Hsp90-mediated morphogenesis operates by destabilizing the cyclin-dependent kinase Cdc28, resulting in delayed mitosis and prolonged polarized growth. Reinstatement of Hsp90 or Cdc28 expression resulted in shortened cells that formed smaller groups with reduced multicellular fitness. Together, our results show how ancient protein folding systems can be tuned to drive rapid evolution at a new level of biological individuality by revealing novel developmental phenotypes.
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Affiliation(s)
- Kristopher Montrose
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki
- Faculty of Biological and Environmental Sciences, University of Helsinki
| | - Dung T. Lac
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Anthony J. Burnetti
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Kai Tong
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki
- Faculty of Biological and Environmental Sciences, University of Helsinki
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Interdisciplinary Graduate Program in Quantitative Biosciences (QBioS)
| | - G. Ozan Bozdag
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Mikaela Hukkanen
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki
- Faculty of Biological and Environmental Sciences, University of Helsinki
| | - William C. Ratcliff
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Juha Saarikangas
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki
- Faculty of Biological and Environmental Sciences, University of Helsinki
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3
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Paukštytė J, López Cabezas RM, Feng Y, Tong K, Schnyder D, Elomaa E, Gregorova P, Doudin M, Särkkä M, Sarameri J, Lippi A, Vihinen H, Juutila J, Nieminen A, Törönen P, Holm L, Jokitalo E, Krisko A, Huiskonen J, Sarin LP, Hietakangas V, Picotti P, Barral Y, Saarikangas J. Global analysis of aging-related protein structural changes uncovers enzyme-polymerization-based control of longevity. Mol Cell 2023; 83:3360-3376.e11. [PMID: 37699397 DOI: 10.1016/j.molcel.2023.08.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 05/18/2023] [Accepted: 08/11/2023] [Indexed: 09/14/2023]
Abstract
Aging is associated with progressive phenotypic changes. Virtually all cellular phenotypes are produced by proteins, and their structural alterations can lead to age-related diseases. However, we still lack comprehensive knowledge of proteins undergoing structural-functional changes during cellular aging and their contributions to age-related phenotypes. Here, we conducted proteome-wide analysis of early age-related protein structural changes in budding yeast using limited proteolysis-mass spectrometry (LiP-MS). The results, compiled in online ProtAge catalog, unraveled age-related functional changes in regulators of translation, protein folding, and amino acid metabolism. Mechanistically, we found that folded glutamate synthase Glt1 polymerizes into supramolecular self-assemblies during aging, causing breakdown of cellular amino acid homeostasis. Inhibiting Glt1 polymerization by mutating the polymerization interface restored amino acid levels in aged cells, attenuated mitochondrial dysfunction, and led to lifespan extension. Altogether, this comprehensive map of protein structural changes enables identifying mechanisms of age-related phenotypes and offers opportunities for their reversal.
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Affiliation(s)
- Jurgita Paukštytė
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Rosa María López Cabezas
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Yuehan Feng
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Kai Tong
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA; Interdisciplinary Graduate Program in Quantitative Biosciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | | | - Ellinoora Elomaa
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Pavlina Gregorova
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Matteo Doudin
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Meeri Särkkä
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Jesse Sarameri
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Alice Lippi
- Department of Experimental Neurodegeneration, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Helena Vihinen
- Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Juhana Juutila
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland; Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Anni Nieminen
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland; Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Petri Törönen
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland; Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Liisa Holm
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland; Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Eija Jokitalo
- Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Anita Krisko
- Department of Experimental Neurodegeneration, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Juha Huiskonen
- Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - L Peter Sarin
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland
| | - Ville Hietakangas
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland; Institute of Biotechnology, HiLIFE, University of Helsinki, 00790 Helsinki, Finland
| | - Paola Picotti
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland; Institute of Molecular Systems Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Yves Barral
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Juha Saarikangas
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland.
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Senju Y, Mushtaq T, Vihinen H, Manninen A, Saarikangas J, Ven K, Engel U, Varjosalo M, Jokitalo E, Lappalainen P. Actin-rich lamellipodia-like protrusions contribute to the integrity of epithelial cell-cell junctions. J Biol Chem 2023; 299:104571. [PMID: 36871754 PMCID: PMC10173786 DOI: 10.1016/j.jbc.2023.104571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Revised: 01/11/2023] [Accepted: 02/01/2023] [Indexed: 03/06/2023] Open
Abstract
Metastasis-suppressor 1 (MTSS1) is a membrane-interacting scaffolding protein that regulates the integrity of epithelial cell-cell junctions and functions as a tumor suppressor in a wide range of carcinomas. MTSS1 binds phosphoinositide-rich membranes through its I-BAR domain, and is capable of sensing and generating negative membrane curvature in vitro. However, the mechanisms by which MTSS1 localizes to intercellular junctions in epithelial cells, and contributes to their integrity and maintenance have remained elusive. By carrying out electron microscopy and live-cell imaging on cultured Madin-Darby canine kidney (MDCK) cell monolayers, we provide evidence that adherens junctions of epithelial cells harbor lamellipodia-like, dynamic actin-driven membrane folds, which exhibit high negative membrane curvature at their distal edges. BioID proteomics and imaging experiments demonstrated that MTSS1 associates with an Arp2/3 complex activator, the WAVE-2 complex, in dynamic actin-rich protrusions at cell-cell junctions. Inhibition of Arp2/3 or WAVE-2 suppressed actin filament assembly at adherens junctions, decreased the dynamics of junctional membrane protrusions, and led to defects in epithelial integrity. Together, these results support a model in which membrane-associated MTSS1, together with the WAVE-2 and Arp2/3 complexes, promotes the formation of dynamic lamellipodia-like actin protrusions that contribute to the integrity of cell-cell junctions in epithelial monolayers.
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Affiliation(s)
- Yosuke Senju
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Japan.
| | - Toiba Mushtaq
- Helsinki Institute of Life Science (HiLIFE) - Institute of Biotechnology, University of Helsinki, Finland
| | - Helena Vihinen
- Helsinki Institute of Life Science (HiLIFE) - Institute of Biotechnology, University of Helsinki, Finland
| | - Aki Manninen
- Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Finland
| | - Juha Saarikangas
- Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Finland; Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, Neuroscience Center, University of Helsinki, Finland
| | - Katharina Ven
- Helsinki Institute of Life Science (HiLIFE) - Institute of Biotechnology, University of Helsinki, Finland
| | - Ulrike Engel
- Nikon Imaging Center and Centre for Organismal Studies, Heidelberg University, Germany
| | - Markku Varjosalo
- Helsinki Institute of Life Science (HiLIFE) - Institute of Biotechnology, University of Helsinki, Finland
| | - Eija Jokitalo
- Helsinki Institute of Life Science (HiLIFE) - Institute of Biotechnology, University of Helsinki, Finland
| | - Pekka Lappalainen
- Helsinki Institute of Life Science (HiLIFE) - Institute of Biotechnology, University of Helsinki, Finland
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5
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Oamen HP, Romero Romero N, Knuckles P, Saarikangas J, Radman‐Livaja M, Dong Y, Caudron F. A rare natural lipid induces neuroglobin expression to prevent amyloid oligomers toxicity and retinal neurodegeneration. Aging Cell 2022; 21:e13645. [PMID: 35656861 PMCID: PMC9282837 DOI: 10.1111/acel.13645] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 03/10/2022] [Accepted: 05/10/2022] [Indexed: 11/29/2022] Open
Abstract
Most neurodegenerative diseases such as Alzheimer's disease are proteinopathies linked to the toxicity of amyloid oligomers. Treatments to delay or cure these diseases are lacking. Using budding yeast, we report that the natural lipid tripentadecanoin induces expression of the nitric oxide oxidoreductase Yhb1 to prevent the formation of protein aggregates during aging and extends replicative lifespan. In mammals, tripentadecanoin induces expression of the Yhb1 orthologue, neuroglobin, to protect neurons against amyloid toxicity. Tripentadecanoin also rescues photoreceptors in a mouse model of retinal degeneration and retinal ganglion cells in a Rhesus monkey model of optic atrophy. Together, we propose that tripentadecanoin affects p-bodies to induce neuroglobin expression and offers a potential treatment for proteinopathies and retinal neurodegeneration.
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Affiliation(s)
- Henry Patrick Oamen
- School of Biological and Behavioural SciencesQueen Mary University of LondonLondonUK
| | - Nathaly Romero Romero
- School of Biological and Behavioural SciencesQueen Mary University of LondonLondonUK
| | - Philip Knuckles
- Friedrich Miescher Institute for Biomedical ResearchBaselSwitzerland
| | - Juha Saarikangas
- Helsinki Institute of Life Science, HiLIFE, University of HelsinkiHelsinkiFinland
- Research Programme in Molecular and Integrative Biosciences, Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
- Neuroscience Center, University of HelsinkiHelsinkiFinland
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6
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Lau Y, Oamen HP, Grogg M, Parfenova I, Saarikangas J, Hannay R, Nichols RA, Hilvert D, Barral Y, Caudron F. Whi3 mnemon association with endoplasmic reticulum membranes confines the memory of deceptive courtship to the yeast mother cell. Curr Biol 2022; 32:963-974.e7. [PMID: 35085498 PMCID: PMC8938615 DOI: 10.1016/j.cub.2022.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 10/19/2021] [Accepted: 01/04/2022] [Indexed: 12/17/2022]
Abstract
Prion-like proteins are involved in many aspects of cellular physiology, including cellular memory. In response to deceptive courtship, budding yeast escapes pheromone-induced cell-cycle arrest through the coalescence of the G1/S inhibitor Whi3 into a dominant, inactive super-assembly. Whi3 is a mnemon (Whi3mnem), a protein that conformational change maintains as a trait in the mother cell but is not inherited by the daughter cells. How the maintenance and asymmetric inheritance of Whi3mnem are achieved is unknown. Here, we report that Whi3mnem is closely associated with endoplasmic reticulum (ER) membranes and is retained in the mother cell by the lateral diffusion barriers present at the bud neck. Strikingly, barrier defects made Whi3mnem propagate in a mitotically stable, prion-like manner. The amyloid-forming glutamine-rich domain of Whi3 was required for both mnemon and prion-like behaviors. Thus, we propose that Whi3mnem is in a self-templating state, lending temporal maintenance of memory, whereas its association with the compartmentalized membranes of the ER prevents infectious propagation to the daughter cells. These results suggest that confined self-templating super-assembly is a powerful mechanism for the long-term encoding of information in a spatially defined manner. Yeast courtship may provide insights on how individual synapses become potentiated in neuronal memory.
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Affiliation(s)
- Yasmin Lau
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Henry Patrick Oamen
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Marcel Grogg
- Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg, 8093 Zürich, Switzerland
| | - Iuliia Parfenova
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg, 8093 Zürich, Switzerland
| | - Juha Saarikangas
- Helsinki Institute of Life Science HiLIFE, Viikinkaari 5, 00790 Helsinki, Finland; Faculty of Biological and Environmental Sciences, Viikinkaari 5, 00790 Helsinki, Finland; Neuroscience Center, University of Helsinki, Viikinkaari 5, 00790 Helsinki, Finland
| | - Robin Hannay
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Richard Alan Nichols
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg, 8093 Zürich, Switzerland
| | - Yves Barral
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg, 8093 Zürich, Switzerland
| | - Fabrice Caudron
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK; IGMM, Univ Montpellier, CNRS, Route de Mende, 34293 Montpellier, France.
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7
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van Oosten-Hawle P, Saarikangas J. Special issue on "Cell stress in development, aging and disease". Exp Cell Res 2021; 408:112839. [PMID: 34560102 DOI: 10.1016/j.yexcr.2021.112839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Montrose K, López Cabezas RM, Paukštytė J, Saarikangas J. Winter is coming: Regulation of cellular metabolism by enzyme polymerization in dormancy and disease. Exp Cell Res 2020; 397:112383. [PMID: 33212148 DOI: 10.1016/j.yexcr.2020.112383] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 11/12/2020] [Accepted: 11/14/2020] [Indexed: 12/20/2022]
Abstract
Metabolism feeds growth. Accordingly, metabolism is regulated by nutrient-sensing pathways that converge growth promoting signals into biosynthesis by regulating the activity of metabolic enzymes. When the environment does not support growth, organisms invest in survival. For cells, this entails transitioning into a dormant, quiescent state (G0). In dormancy, the activity of biosynthetic pathways is dampened, and catabolic metabolism and stress tolerance pathways are activated. Recent work in yeast has demonstrated that dormancy is associated with alterations in the physicochemical properties of the cytoplasm, including changes in pH, viscosity and macromolecular crowding. Accompanying these changes, numerous metabolic enzymes transition from soluble to polymerized assemblies. These large-scale self-assemblies are dynamic and depolymerize when cells resume growth. Here we review how enzyme polymerization enables metabolic plasticity by tuning carbohydrate, nucleic acid, amino acid and lipid metabolic pathways, with particular focus on its potential adaptive value in cellular dormancy.
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Affiliation(s)
- Kristopher Montrose
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Finland; Research Programme in Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
| | - Rosa María López Cabezas
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Finland; Research Programme in Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
| | - Jurgita Paukštytė
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Finland; Research Programme in Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
| | - Juha Saarikangas
- Helsinki Institute of Life Science, HiLIFE, University of Helsinki, Finland; Research Programme in Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland; Neuroscience Center, University of Helsinki, Finland.
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Sawarkar R, Scherz-Shouval R, Denzel MS, Saarikangas J. Chaperoning junior faculty: Institutional support and guidance can relieve challenges for early-career group leaders and improve academic performance. EMBO Rep 2018; 20:embr.201847163. [PMID: 30470689 DOI: 10.15252/embr.201847163] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Ritwick Sawarkar
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
| | | | - Martin S Denzel
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Juha Saarikangas
- Helsinki Institute of Life Science HiLIFE, Helsinki, Finland.,Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland
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10
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Affiliation(s)
- Ritwick Sawarkar
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
| | | | - Martin Denzel
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Juha Saarikangas
- Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.
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Abstract
Organisms rely on correctly folded proteins to carry out essential functions. Protein quality control factors guard proteostasis and prevent protein misfolding. When quality control fails and in response to diverse stresses, many proteins start to accumulate at specific deposit sites that maintain cellular organization and protect the functionality of coalescing proteins. These transitions involve dedicated proteins that promote coalescence and are facilitated by endo-membranes and cytoskeletal platforms. Moreover, several proteins make use of weak multivalent interactions or conformational templating to drive the formation of large-scale assemblies. Formation of such assemblies is often associated with a change in biochemical activity that can be used by cells to execute biochemical decisions in a localized manner during development and adaption. Since all assembly types impact cell physiology, their localization and dynamics need to be tightly regulated. Interestingly, at least some of the regulatory mechanisms are shared by functional membrane-less organelles and assemblies of terminally aggregated proteins. Furthermore, constituents of functional assemblies can aggregate and become non-functional during aging. Here we present the current knowledge as to how coalescing protein assemblies are spatially organized in cells and we postulate that failures in their spatial confinement might underscore certain aspects of aging and neurodegenerative diseases.
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Affiliation(s)
- Juha Saarikangas
- a ETH Zurich, Institute of Biochemistry , Zurich , Switzerland.,b Wissenschaftskolleg zu Berlin , Institute for Advanced Study , Berlin , Germany.,c Helsinki Institute of Life Science, University of Helsinki , Helsinki , Finland.,d Faculty of Biological and Environmental Sciences , University of Helsinki , Helsinki , Finland
| | - Fabrice Caudron
- e Randall Division of Cell and Molecular Biophysics , King's College London , London , UK
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12
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Saarikangas J, Caudron F, Prasad R, Moreno DF, Bolognesi A, Aldea M, Barral Y. Compartmentalization of ER-Bound Chaperone Confines Protein Deposit Formation to the Aging Yeast Cell. Curr Biol 2017; 27:773-783. [PMID: 28262489 DOI: 10.1016/j.cub.2017.01.069] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 12/21/2016] [Accepted: 01/31/2017] [Indexed: 11/19/2022]
Abstract
In order to produce rejuvenated daughters, dividing budding yeast cells confine aging factors, including protein aggregates, to the aging mother cell. The asymmetric inheritance of these protein deposits is mediated by organelle and cytoskeletal attachment and by cell geometry. Yet it remains unclear how deposit formation is restricted to the aging lineage. Here, we show that selective membrane anchoring and the compartmentalization of the endoplasmic reticulum (ER) membrane confine protein deposit formation to aging cells during division. Supporting the idea that the age-dependent deposit forms through coalescence of smaller aggregates, two deposits rapidly merged when placed in the same cell by cell-cell fusion. The deposits localized to the ER membrane, primarily to the nuclear envelope (NE). Strikingly, weakening the diffusion barriers that separate the ER membrane into mother and bud compartments caused premature formation of deposits in the daughter cells. Detachment of the Hsp40 protein Ydj1 from the ER membrane elicited a similar phenotype, suggesting that the diffusion barriers and farnesylated Ydj1 functioned together to confine protein deposit formation to mother cells during division. Accordingly, fluorescence correlation spectroscopy measurements in dividing cells indicated that a slow-diffusing, possibly client-bound Ydj1 fraction was asymmetrically enriched in the mother compartment. This asymmetric distribution depended on Ydj1 farnesylation and intact diffusion barriers. Taking these findings together, we propose that ER-anchored Ydj1 binds deposit precursors and prevents them from spreading into daughter cells during division by subjecting them to the ER diffusion barriers. This ensures that the coalescence of precursors into a single deposit is restricted to the aging lineage.
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Affiliation(s)
- Juha Saarikangas
- Institute of Biochemistry, ETH Zurich, Otto-Stern-Weg 3, 8093 Zurich, Switzerland; Wissenschaftskolleg zu Berlin, Institute for Advanced Study, Wallotstrasse 19, 14193 Berlin, Germany
| | - Fabrice Caudron
- Institute of Biochemistry, ETH Zurich, Otto-Stern-Weg 3, 8093 Zurich, Switzerland; Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Rupali Prasad
- Institute of Biochemistry, ETH Zurich, Otto-Stern-Weg 3, 8093 Zurich, Switzerland
| | - David F Moreno
- Molecular Biology Institute of Barcelona, CSIC, Baldiri i Reixac 15, 08028 Barcelona, Spain
| | - Alessio Bolognesi
- Institute of Biochemistry, ETH Zurich, Otto-Stern-Weg 3, 8093 Zurich, Switzerland
| | - Martí Aldea
- Molecular Biology Institute of Barcelona, CSIC, Baldiri i Reixac 15, 08028 Barcelona, Spain
| | - Yves Barral
- Institute of Biochemistry, ETH Zurich, Otto-Stern-Weg 3, 8093 Zurich, Switzerland.
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13
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Abstract
The post-synaptic spines of neuronal dendrites are highly elaborate membrane protrusions. Their anatomy, stability and density are intimately linked to cognitive performance. The morphological transitions of spines are powered by coordinated polymerization of actin filaments against the plasma membrane, but how the membrane-associated polymerization is spatially and temporally regulated has remained ill defined. Here, we discuss our recent findings showing that dendritic spines can be initiated by direct membrane bending by the I-BAR protein MIM/Mtss1. This lipid phosphatidylinositol (PI(4,5)P2) signaling-activated membrane bending coordinated spatial actin assembly and promoted spine formation. From recent advances, we formulate a general model to discuss how spatially concentrated protein-lipid microdomains formed by multivalent interactions between lipids and actin/membrane regulatory proteins might launch cell protrusions.
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Affiliation(s)
- Pirta Hotulainen
- Neuroscience Center, University of Helsinki, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
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Saarikangas J, Barral Y. Protein aggregates are associated with replicative aging without compromising protein quality control. eLife 2015; 4. [PMID: 26544680 PMCID: PMC4635334 DOI: 10.7554/elife.06197] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 10/19/2015] [Indexed: 12/12/2022] Open
Abstract
Differentiation of cellular lineages is facilitated by asymmetric segregation of fate determinants between dividing cells. In budding yeast, various aging factors segregate to the aging (mother)-lineage, with poorly understood consequences. In this study, we show that yeast mother cells form a protein aggregate during early replicative aging that is maintained as a single, asymmetrically inherited deposit over the remaining lifespan. Surprisingly, deposit formation was not associated with stress or general decline in proteostasis. Rather, the deposit-containing cells displayed enhanced degradation of cytosolic proteasome substrates and unimpaired clearance of stress-induced protein aggregates. Deposit formation was dependent on Hsp42, which collected non-random client proteins of the Hsp104/Hsp70-refolding machinery, including the prion Sup35. Importantly, loss of Hsp42 resulted in symmetric inheritance of its constituents and prolonged the lifespan of the mother cell. Together, these data suggest that protein aggregation is an early aging-associated differentiation event in yeast, having a two-faceted role in organismal fitness. DOI:http://dx.doi.org/10.7554/eLife.06197.001 Aging is a complex process. Studies involving a single-celled organism called budding yeast are commonly used to investigate the factors that contribute to aging. When these yeast cells divide, a small daughter cell buds out from a large mother cell. A mother cell has a limited lifespan and produces a finite number of daughter cells and then dies (a phenomenon referred to ‘replicative aging’). However, when a daughter cell forms, the daughter's age is reset to zero, giving it the full potential to produce new offspring. Previous research on budding yeast has shown that damaged or aggregated proteins accumulate in the mother cells but not the daughter cells, and that this accumulation of proteins contributes to shortening the lifespan of the mother cell. Furthermore, protein aggregation has also been associated with a number of age-related diseases in humans, including neurodegenerative disorders such as Alzheimer's and Parkinson's disease. However, it remains unclear how cells respond to protein aggregation that occurs during aging. Many studies that have previously investigated this question have relied on exposing cells to stressful conditions, such as high temperatures, in order to trigger proteins to aggregate. But now, Saarikangas and Barral have studied how proteins aggregate under normal, unstressed conditions in budding yeast as they age. The experiments revealed that most unstressed yeast cells develop a single deposit of aggregated proteins already during early aging. This age-associated structure proved to be a different type of response than the protein aggregation that occurs during stress. Furthermore, the deposit did not form as a consequence of the cell having obvious problems with folding its proteins, nor did the deposit hinder cells from coping with stressful conditions that trigger protein misfolding. Rather, this deposit supported the ability of the cell to degrade defective proteins. This suggests that the deposit represents an early adaptive response to aging, which might consequently provide aged cells some advantage over their younger counterparts. Saarikangas and Barral also found that this protein deposit was always retained in the mother cell and not passed onto the daughters at cell division. Further experiments showed that an enzyme called heat shock protein 42 was responsible for collecting target proteins and bring them together to form the single deposit. Reducing the levels of this enzyme prevented the deposit from forming and extended the lifespan of the mother cells. Thus, these findings suggest that mother cells collect harmful protein aggregates into a single deposit and prevent them from entering the daughter cells. Further work is needed to understand how the deposit is preferentially retained within the mother cell. DOI:http://dx.doi.org/10.7554/eLife.06197.002
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Affiliation(s)
- Juha Saarikangas
- Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland
| | - Yves Barral
- Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland
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15
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Maddugoda MP, Stefani C, Gonzalez-Rodriguez D, Saarikangas J, Torrino S, Janel S, Munro P, Doye A, Prodon F, Aurrand-Lions M, Goossens PL, Lafont F, Bassereau P, Lappalainen P, Brochard F, Lemichez E. cAMP signaling by anthrax edema toxin induces transendothelial cell tunnels, which are resealed by MIM via Arp2/3-driven actin polymerization. Cell Host Microbe 2012; 10:464-74. [PMID: 22100162 DOI: 10.1016/j.chom.2011.09.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 07/19/2011] [Accepted: 09/14/2011] [Indexed: 12/22/2022]
Abstract
RhoA-inhibitory bacterial toxins, such as Staphylococcus aureus EDIN toxin, induce large transendothelial cell macroaperture (TEM) tunnels that rupture the host endothelium barrier and promote bacterial dissemination. Host cells repair these tunnels by extending actin-rich membrane waves from the TEM edges. We reveal that cyclic-AMP signaling produced by Bacillus anthracis edema toxin (ET) also induces TEM formation, which correlates with increased vascular permeability. We show that ET-induced TEM formation resembles liquid dewetting, a physical process of nucleation and growth of holes within a thin liquid film. We also identify the cellular mechanisms of tunnel closure and reveal that the I-BAR domain protein Missing in Metastasis (MIM) senses de novo membrane curvature generated by the TEM, accumulates at the TEM edge, and triggers Arp2/3-dependent actin polymerization, which induces actin-rich membrane waves that close the TEM. Thus, the balance between ET-induced TEM formation and resealing likely determines the integrity of the host endothelium barrier.
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Affiliation(s)
- Madhavi P Maddugoda
- INSERM, U, Université de Nice-Sophia-Antipolis, Centre Méditerranéen de Médecine Moléculaire, Nice, France
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16
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Pykäläinen A, Boczkowska M, Zhao H, Saarikangas J, Rebowski G, Jansen M, Hakanen J, Koskela EV, Peränen J, Vihinen H, Jokitalo E, Salminen M, Ikonen E, Dominguez R, Lappalainen P. Pinkbar is an epithelial-specific BAR domain protein that generates planar membrane structures. Nat Struct Mol Biol 2011; 18:902-7. [PMID: 21743456 DOI: 10.1038/nsmb.2079] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 05/05/2011] [Indexed: 12/16/2022]
Abstract
Bin/amphipysin/Rvs (BAR)-domain proteins sculpt cellular membranes and have key roles in processes such as endocytosis, cell motility and morphogenesis. BAR domains are divided into three subfamilies: BAR- and F-BAR-domain proteins generate positive membrane curvature and stabilize cellular invaginations, whereas I-BAR-domain proteins induce negative curvature and stabilize protrusions. We show that a previously uncharacterized member of the I-BAR subfamily, Pinkbar, is specifically expressed in intestinal epithelial cells, where it localizes to Rab13-positive vesicles and to the plasma membrane at intercellular junctions. Notably, the BAR domain of Pinkbar does not induce membrane tubulation but promotes the formation of planar membrane sheets. Structural and mutagenesis analyses reveal that the BAR domain of Pinkbar has a relatively flat lipid-binding interface and that it assembles into sheet-like oligomers in crystals and in solution, which may explain its unique membrane-deforming activity.
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Affiliation(s)
- Anette Pykäläinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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Saarikangas J, Mattila PK, Varjosalo M, Bovellan M, Hakanen J, Calzada-Wack J, Tost M, Jennen L, Rathkolb B, Hans W. Missing-in-metastasis MIM/MTSS1 promotes actin assembly at intercellular junctions and is required for integrity of kidney epithelia. Development 2011. [DOI: 10.1242/dev.067769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Saarikangas J, Mattila PK, Varjosalo M, Bovellan M, Hakanen J, Calzada-Wack J, Tost M, Jennen L, Rathkolb B, Hans W, Horsch M, Hyvönen ME, Perälä N, Fuchs H, Gailus-Durner V, Esposito I, Wolf E, de Angelis MH, Frilander MJ, Savilahti H, Sariola H, Sainio K, Lehtonen S, Taipale J, Salminen M, Lappalainen P. Missing-in-metastasis MIM/MTSS1 promotes actin assembly at intercellular junctions and is required for integrity of kidney epithelia. J Cell Sci 2011; 124:1245-55. [PMID: 21406566 DOI: 10.1242/jcs.082610] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
MIM/MTSS1 is a tissue-specific regulator of plasma membrane dynamics, whose altered expression levels have been linked to cancer metastasis. MIM deforms phosphoinositide-rich membranes through its I-BAR domain and interacts with actin monomers through its WH2 domain. Recent work proposed that MIM also potentiates Sonic hedgehog (Shh)-induced gene expression. Here, we generated MIM mutant mice and found that full-length MIM protein is dispensable for embryonic development. However, MIM-deficient mice displayed a severe urinary concentration defect caused by compromised integrity of kidney epithelia intercellular junctions, which led to bone abnormalities and end-stage renal failure. In cultured kidney epithelial (MDCK) cells, MIM displayed dynamic localization to adherens junctions, where it promoted Arp2/3-mediated actin filament assembly. This activity was dependent on the ability of MIM to interact with both membranes and actin monomers. Furthermore, results from the mouse model and cell culture experiments suggest that full-length MIM is not crucial for Shh signaling, at least during embryogenesis. Collectively, these data demonstrate that MIM modulates interplay between the actin cytoskeleton and plasma membrane to promote the maintenance of intercellular contacts in kidney epithelia.
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Affiliation(s)
- Juha Saarikangas
- Institute of Biotechnology, PO Box 56, University of Helsinki, 00014 Finland
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Abstract
The plasma membrane and the underlying cortical actin cytoskeleton undergo continuous dynamic interplay that is responsible for many essential aspects of cell physiology. Polymerization of actin filaments against cellular membranes provides the force for a number of cellular processes such as migration, morphogenesis, and endocytosis. Plasma membrane phosphoinositides (especially phosphatidylinositol bis- and trisphosphates) play a central role in regulating the organization and dynamics of the actin cytoskeleton by acting as platforms for protein recruitment, by triggering signaling cascades, and by directly regulating the activities of actin-binding proteins. Furthermore, a number of actin-associated proteins, such as BAR domain proteins, are capable of directly deforming phosphoinositide-rich membranes to induce plasma membrane protrusions or invaginations. Recent studies have also provided evidence that the actin cytoskeleton-plasma membrane interactions are misregulated in a number of pathological conditions such as cancer and during pathogen invasion. Here, we summarize the wealth of knowledge on how the cortical actin cytoskeleton is regulated by phosphoinositides during various cell biological processes. We also discuss the mechanisms by which interplay between actin dynamics and certain membrane deforming proteins regulate the morphology of the plasma membrane.
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Affiliation(s)
- Juha Saarikangas
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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Saarikangas J, Zhao H, Pykäläinen A, Laurinmäki P, Mattila PK, Kinnunen PKJ, Butcher SJ, Lappalainen P. Molecular mechanisms of membrane deformation by I-BAR domain proteins. Curr Biol 2009; 19:95-107. [PMID: 19150238 DOI: 10.1016/j.cub.2008.12.029] [Citation(s) in RCA: 232] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 11/26/2008] [Accepted: 12/08/2008] [Indexed: 02/06/2023]
Abstract
BACKGROUND Generation of membrane curvature is critical for the formation of plasma membrane protrusions and invaginations and for shaping intracellular organelles. Among the central regulators of membrane dynamics are the BAR superfamily domains, which deform membranes into tubular structures. In contrast to the relatively well characterized BAR and F-BAR domains that promote the formation of plasma membrane invaginations, I-BAR domains induce plasma membrane protrusions through a poorly understood mechanism. RESULTS We show that I-BAR domains induce strong PI(4,5)P(2) clustering upon membrane binding, bend the membrane through electrostatic interactions, and remain dynamically associated with the inner leaflet of membrane tubules. Thus, I-BAR domains induce the formation of dynamic membrane protrusions to the opposite direction than do BAR and F-BAR domains. Strikingly, comparison of different I-BAR domains revealed that they deform PI(4,5)P(2)-rich membranes through distinct mechanisms. IRSp53 and IRTKS I-BARs bind membranes mainly through electrostatic interactions, whereas MIM and ABBA I-BARs additionally insert an amphipathic helix into the membrane bilayer, resulting in larger tubule diameter in vitro and more efficient filopodia formation in vivo. Furthermore, FRAP analysis revealed that whereas the mammalian I-BAR domains display dynamic association with filopodia, the C. elegans I-BAR domain forms relatively stable structures inside the plasma membrane protrusions. CONCLUSIONS These data define I-BAR domain as a functional member of the BAR domain superfamily and unravel the mechanisms by which I-BAR domains deform membranes to induce filopodia in cells. Furthermore, our work reveals unexpected divergence in the mechanisms by which evolutionarily distinct groups of I-BAR domains interact with PI(4,5)P(2)-rich membranes.
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Affiliation(s)
- Juha Saarikangas
- Program in Cell and Molecular Biology, Institute of Biotechnology, P.O. Box 56, University of Helsinki, FIN-00014 Helsinki, Finland
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Saarikangas J, Hakanen J, Mattila PK, Grumet M, Salminen M, Lappalainen P. ABBA regulates plasma-membrane and actin dynamics to promote radial glia extension. J Cell Sci 2008; 121:1444-54. [PMID: 18413296 DOI: 10.1242/jcs.027466] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Radial glia play key roles in neuronal migration, axon guidance, and neurogenesis during development of the central nervous system. However, the molecular mechanisms regulating growth and morphology of these extended cells are unknown. We show that ABBA, a novel member of the IRSp53-MIM protein family, is enriched in different types of radial glia. ABBA binds ATP-actin monomers with high affinity and deforms PtdIns(4,5)P(2)-rich membranes in vitro through its WH2 and IM domains, respectively. In radial-glia-like C6-R cells, ABBA localises to the interface between the actin cytoskeleton and plasma membrane, and its depletion by RNAi led to defects in lamellipodial dynamics and process extension. Together, this study identifies ABBA as a novel regulator of actin and plasma membrane dynamics in radial glial cells, and provides evidence that membrane binding and deformation activity is critical for the cellular functions of IRSp53-MIM-ABBA family proteins.
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Affiliation(s)
- Juha Saarikangas
- Program in Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, Finland
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Mattila PK, Pykäläinen A, Saarikangas J, Paavilainen VO, Vihinen H, Jokitalo E, Lappalainen P. Missing-in-metastasis and IRSp53 deform PI(4,5)P2-rich membranes by an inverse BAR domain-like mechanism. ACTA ACUST UNITED AC 2007; 176:953-64. [PMID: 17371834 PMCID: PMC2064081 DOI: 10.1083/jcb.200609176] [Citation(s) in RCA: 299] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The actin cytoskeleton plays a fundamental role in various motile and morphogenetic processes involving membrane dynamics. We show that actin-binding proteins MIM (missing-in-metastasis) and IRSp53 directly bind PI(4,5)P(2)-rich membranes and deform them into tubular structures. This activity resides in the N-terminal IRSp53/MIM domain (IMD) of these proteins, which is structurally related to membrane-tubulating BAR (Bin/amphiphysin/Rvs) domains. We found that because of a difference in the geometry of the PI(4,5)P(2)-binding site, IMDs induce a membrane curvature opposite that of BAR domains and deform membranes by binding to the interior of the tubule. This explains why IMD proteins induce plasma membrane protrusions rather than invaginations. We also provide evidence that the membrane-deforming activity of IMDs, instead of the previously proposed F-actin-bundling or GTPase-binding activities, is critical for the induction of the filopodia/microspikes in cultured mammalian cells. Together, these data reveal that interplay between actin dynamics and a novel membrane-deformation activity promotes cell motility and morphogenesis.
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Affiliation(s)
- Pieta K Mattila
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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