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Bement WM, Goryachev AB, Miller AL, von Dassow G. Patterning of the cell cortex by Rho GTPases. Nat Rev Mol Cell Biol 2024; 25:290-308. [PMID: 38172611 DOI: 10.1038/s41580-023-00682-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2023] [Indexed: 01/05/2024]
Abstract
The Rho GTPases - RHOA, RAC1 and CDC42 - are small GTP binding proteins that regulate basic biological processes such as cell locomotion, cell division and morphogenesis by promoting cytoskeleton-based changes in the cell cortex. This regulation results from active (GTP-bound) Rho GTPases stimulating target proteins that, in turn, promote actin assembly and myosin 2-based contraction to organize the cortex. This basic regulatory scheme, well supported by in vitro studies, led to the natural assumption that Rho GTPases function in vivo in an essentially linear matter, with a given process being initiated by GTPase activation and terminated by GTPase inactivation. However, a growing body of evidence based on live cell imaging, modelling and experimental manipulation indicates that Rho GTPase activation and inactivation are often tightly coupled in space and time via signalling circuits and networks based on positive and negative feedback. In this Review, we present and discuss this evidence, and we address one of the fundamental consequences of coupled activation and inactivation: the ability of the Rho GTPases to self-organize, that is, direct their own transition from states of low order to states of high order. We discuss how Rho GTPase self-organization results in the formation of diverse spatiotemporal cortical patterns such as static clusters, oscillatory pulses, travelling wave trains and ring-like waves. Finally, we discuss the advantages of Rho GTPase self-organization and pattern formation for cell function.
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Affiliation(s)
- William M Bement
- Center for Quantitative Cell Imaging, Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Andrew B Goryachev
- Center for Engineering Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
| | - Ann L Miller
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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2
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Phillips TA, Marcotti S, Cox S, Parsons M. Imaging actin organisation and dynamics in 3D. J Cell Sci 2024; 137:jcs261389. [PMID: 38236161 PMCID: PMC10906668 DOI: 10.1242/jcs.261389] [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] [Indexed: 01/19/2024] Open
Abstract
The actin cytoskeleton plays a critical role in cell architecture and the control of fundamental processes including cell division, migration and survival. The dynamics and organisation of F-actin have been widely studied in a breadth of cell types on classical two-dimensional (2D) surfaces. Recent advances in optical microscopy have enabled interrogation of these cytoskeletal networks in cells within three-dimensional (3D) scaffolds, tissues and in vivo. Emerging studies indicate that the dimensionality experienced by cells has a profound impact on the structure and function of the cytoskeleton, with cells in 3D environments exhibiting cytoskeletal arrangements that differ to cells in 2D environments. However, the addition of a third (and fourth, with time) dimension leads to challenges in sample preparation, imaging and analysis, necessitating additional considerations to achieve the required signal-to-noise ratio and spatial and temporal resolution. Here, we summarise the current tools for imaging actin in a 3D context and highlight examples of the importance of this in understanding cytoskeletal biology and the challenges and opportunities in this domain.
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Affiliation(s)
- Thomas A. Phillips
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunts House, Guys Campus, London SE1 1UL, UK
| | - Stefania Marcotti
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunts House, Guys Campus, London SE1 1UL, UK
- Microscopy Innovation Centre, King's College London, Guys Campus, London SE1 1UL, UK
| | - Susan Cox
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunts House, Guys Campus, London SE1 1UL, UK
| | - Maddy Parsons
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunts House, Guys Campus, London SE1 1UL, UK
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3
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Cazzagon G, Roubinet C, Baum B. Polarized SCAR and the Arp2/3 complex regulate apical cortical remodeling in asymmetrically dividing neuroblasts. iScience 2023; 26:107129. [PMID: 37434695 PMCID: PMC10331462 DOI: 10.1016/j.isci.2023.107129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 05/03/2023] [Accepted: 06/10/2023] [Indexed: 07/13/2023] Open
Abstract
Although the formin-nucleated actomyosin cortex has been shown to drive the changes in cell shape that accompany animal cell division in both symmetric and asymmetric cell divisions, the mitotic role of cortical Arp2/3-nucleated actin networks remain unclear. Here using asymmetrically dividing Drosophila neural stem cells as a model system, we identify a pool of membrane protrusions that form at the apical cortex of neuroblasts as they enter mitosis. Strikingly, these apically localized protrusions are enriched in SCAR, and depend on SCAR and Arp2/3 complexes for their formation. Because compromising SCAR or the Arp2/3 complex delays the apical clearance of Myosin II at the onset of anaphase and induces cortical instability at cytokinesis, these data point to a role for an apical branched actin filament network in fine-tuning the actomyosin cortex to enable the precise control of cell shape changes during an asymmetric cell division.
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Affiliation(s)
- Giulia Cazzagon
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Chantal Roubinet
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Buzz Baum
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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4
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Jeyasimman D, Ercan B, Dharmawan D, Naito T, Sun J, Saheki Y. PDZD-8 and TEX-2 regulate endosomal PI(4,5)P 2 homeostasis via lipid transport to promote embryogenesis in C. elegans. Nat Commun 2021; 12:6065. [PMID: 34663803 PMCID: PMC8523718 DOI: 10.1038/s41467-021-26177-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 09/22/2021] [Indexed: 11/10/2022] Open
Abstract
Different types of cellular membranes have unique lipid compositions that are important for their functional identity. PI(4,5)P2 is enriched in the plasma membrane where it contributes to local activation of key cellular events, including actomyosin contraction and cytokinesis. However, how cells prevent PI(4,5)P2 from accumulating in intracellular membrane compartments, despite constant intermixing and exchange of lipid membranes, is poorly understood. Using the C. elegans early embryo as our model system, we show that the evolutionarily conserved lipid transfer proteins, PDZD-8 and TEX-2, act together with the PI(4,5)P2 phosphatases, OCRL-1 and UNC-26/synaptojanin, to prevent the build-up of PI(4,5)P2 on endosomal membranes. In the absence of these four proteins, large amounts of PI(4,5)P2 accumulate on endosomes, leading to embryonic lethality due to ectopic recruitment of proteins involved in actomyosin contractility. PDZD-8 localizes to the endoplasmic reticulum and regulates endosomal PI(4,5)P2 levels via its lipid harboring SMP domain. Accumulation of PI(4,5)P2 on endosomes is accompanied by impairment of their degradative capacity. Thus, cells use multiple redundant systems to maintain endosomal PI(4,5)P2 homeostasis.
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Affiliation(s)
- Darshini Jeyasimman
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Bilge Ercan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Dennis Dharmawan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Jingbo Sun
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore.
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, 860-8556, Japan.
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5
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LaFoya B, Prehoda KE. Actin-dependent membrane polarization reveals the mechanical nature of the neuroblast polarity cycle. Cell Rep 2021; 35:109146. [PMID: 34010656 PMCID: PMC8174105 DOI: 10.1016/j.celrep.2021.109146] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/26/2021] [Accepted: 04/26/2021] [Indexed: 12/18/2022] Open
Abstract
The Par complex directs fate-determinant segregation from the apical membrane of asymmetrically dividing Drosophila neuroblasts. While the physical interactions that recruit the Par complex have been extensively studied, little is known about how the membrane itself behaves during polarization. We examined the membrane dynamics of neuroblasts and surrounding cells using a combination of super-resolution and time-lapse imaging, revealing cellular-scale movements of diverse membrane features during asymmetric division cycles. Membrane domains that are distributed across the neuroblast membrane in interphase become polarized in early mitosis, where they mediate formation of cortical patches of the Par protein atypical protein kinase C (aPKC). Membrane and protein polarity cycles are precisely synchronized and are generated by extensive actin-dependent forces that deform the surrounding tissue. In addition to suggesting a role for the membrane in asymmetric division, our results reveal the mechanical nature of the neuroblast polarity cycle. LaFoya and Prehoda examine the membrane dynamics of asymmetrically dividing Drosophila neuroblasts and discover that the membrane undergoes a polarity cycle. Their studies show that membrane and protein polarity is precisely correlated and that cellular-scale forces generated during the cycle significantly deform the surrounding tissue.
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Affiliation(s)
- Bryce LaFoya
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
| | - Kenneth E Prehoda
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA.
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Hewlett B, Singh NP, Vannier C, Galli T. ER-PM Contact Sites - SNARING Actors in Emerging Functions. Front Cell Dev Biol 2021; 9:635518. [PMID: 33681218 PMCID: PMC7928305 DOI: 10.3389/fcell.2021.635518] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 01/21/2021] [Indexed: 11/13/2022] Open
Abstract
The compartmentalisation achieved by confining cytoplasm into membrane-enclosed organelles in eukaryotic cells is essential for maintaining vital functions including ATP production, synthetic and degradative pathways. While intracellular organelles are highly specialised in these functions, the restricting membranes also impede exchange of molecules responsible for the synchronised and responsive cellular activities. The initial identification of contact sites between the ER and plasma membrane (PM) provided a potential candidate structure for communication between organelles without mixing by fusion. Over the past decades, research has revealed a far broader picture of the events. Membrane contact sites (MCSs) have been recognized as increasingly important actors in cell differentiation, plasticity and maintenance, and, upon dysfunction, responsible for pathological conditions such as cancer and neurodegenerative diseases. Present in multiple organelles and cell types, MCSs promote transport of lipids and Ca2+ homoeostasis, with a range of associated protein families. Interestingly, each MCS displays a unique molecular signature, adapted to organelle functions. This review will explore the literature describing the molecular components and interactions taking place at ER-PM contact sites, their functions, and implications in eukaryotic cells, particularly neurons, with emphasis on lipid transfer proteins and emerging function of SNAREs.
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Affiliation(s)
- Bailey Hewlett
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France
| | - Neha Pratap Singh
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France
| | - Christian Vannier
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France
| | - Thierry Galli
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France.,GHU PARIS Psychiatrie and Neurosciences, Paris, France
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7
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Samandar Eweis D, Plastino J. Roles of Actin in the Morphogenesis of the Early Caenorhabditis elegans Embryo. Int J Mol Sci 2020; 21:ijms21103652. [PMID: 32455793 PMCID: PMC7279410 DOI: 10.3390/ijms21103652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/18/2020] [Accepted: 05/19/2020] [Indexed: 12/23/2022] Open
Abstract
The cell shape changes that ensure asymmetric cell divisions are crucial for correct development, as asymmetric divisions allow for the formation of different cell types and therefore different tissues. The first division of the Caenorhabditis elegans embryo has emerged as a powerful model for understanding asymmetric cell division. The dynamics of microtubules, polarity proteins, and the actin cytoskeleton are all key for this process. In this review, we highlight studies from the last five years revealing new insights about the role of actin dynamics in the first asymmetric cell division of the early C. elegans embryo. Recent results concerning the roles of actin and actin binding proteins in symmetry breaking, cortical flows, cortical integrity, and cleavage furrow formation are described.
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Affiliation(s)
- Dureen Samandar Eweis
- Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS, 75005 Paris, France;
- Sorbonne Université, 75005 Paris, France
| | - Julie Plastino
- Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS, 75005 Paris, France;
- Sorbonne Université, 75005 Paris, France
- Correspondence:
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8
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Clémot M, Sênos Demarco R, Jones DL. Lipid Mediated Regulation of Adult Stem Cell Behavior. Front Cell Dev Biol 2020; 8:115. [PMID: 32185173 PMCID: PMC7058546 DOI: 10.3389/fcell.2020.00115] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 02/11/2020] [Indexed: 12/18/2022] Open
Abstract
Adult stem cells constitute an important reservoir of self-renewing progenitor cells and are crucial for maintaining tissue and organ homeostasis. The capacity of stem cells to self-renew or differentiate can be attributed to distinct metabolic states, and it is now becoming apparent that metabolism plays instructive roles in stem cell fate decisions. Lipids are an extremely vast class of biomolecules, with essential roles in energy homeostasis, membrane structure and signaling. Imbalances in lipid homeostasis can result in lipotoxicity, cell death and diseases, such as cardiovascular disease, insulin resistance and diabetes, autoimmune disorders and cancer. Therefore, understanding how lipid metabolism affects stem cell behavior offers promising perspectives for the development of novel approaches to control stem cell behavior either in vitro or in patients, by modulating lipid metabolic pathways pharmacologically or through diet. In this review, we will first address how recent progress in lipidomics has created new opportunities to uncover stem-cell specific lipidomes. In addition, genetic and/or pharmacological modulation of lipid metabolism have shown the involvement of specific pathways, such as fatty acid oxidation (FAO), in regulating adult stem cell behavior. We will describe and compare findings obtained in multiple stem cell models in order to provide an assessment on whether unique lipid metabolic pathways may commonly regulate stem cell behavior. We will then review characterized and potential molecular mechanisms through which lipids can affect stem cell-specific properties, including self-renewal, differentiation potential or interaction with the niche. Finally, we aim to summarize the current knowledge of how alterations in lipid homeostasis that occur as a consequence of changes in diet, aging or disease can impact stem cells and, consequently, tissue homeostasis and repair.
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Affiliation(s)
- Marie Clémot
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, United States
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, United States
| | - Rafael Sênos Demarco
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, United States
| | - D. Leanne Jones
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, United States
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
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9
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Chan FY, Silva AM, Carvalho AX. Using the Four-Cell C. elegans Embryo to Study Contractile Ring Dynamics During Cytokinesis. Methods Mol Biol 2020; 2101:297-325. [PMID: 31879911 DOI: 10.1007/978-1-0716-0219-5_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cytokinesis is the process that completes cell division by partitioning the contents of the mother cell between the two daughter cells. It involves the highly regulated assembly and constriction of an actomyosin contractile ring, whose function is to pinch the mother cell in two. Research on the contractile ring has particularly focused on the signaling mechanisms that dictate when and where the ring is formed. In vivo studies of ring constriction are however scarce and its mechanistic understanding is therefore limited. Here we present several experimental approaches for monitoring ring constriction in vivo, using the four-cell C. elegans embryo as model. These approaches allow for the ring to be perturbed only after it forms and include the combination of live imaging with acute drug treatments, temperature-sensitive mutants and rapid temperature shifts, as well as laser microsurgery. In addition, we explain how to combine these with RNAi-mediated depletion of specific components of the cytokinetic machinery.
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Affiliation(s)
- Fung Yi Chan
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Ana Marta Silva
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Ana Xavier Carvalho
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.
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10
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Marhava P, Aliaga Fandino AC, Koh SW, Jelínková A, Kolb M, Janacek DP, Breda AS, Cattaneo P, Hammes UZ, Petrášek J, Hardtke CS. Plasma Membrane Domain Patterning and Self-Reinforcing Polarity in Arabidopsis. Dev Cell 2020; 52:223-235.e5. [DOI: 10.1016/j.devcel.2019.11.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/08/2019] [Accepted: 11/21/2019] [Indexed: 10/25/2022]
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11
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Hirani N, Illukkumbura R, Bland T, Mathonnet G, Suhner D, Reymann AC, Goehring NW. Anterior-enriched filopodia create the appearance of asymmetric membrane microdomains in polarizing C. elegans zygotes. J Cell Sci 2019; 132:jcs.230714. [PMID: 31221727 PMCID: PMC6679585 DOI: 10.1242/jcs.230714] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 06/17/2019] [Indexed: 12/19/2022] Open
Abstract
The association of molecules within membrane microdomains is critical for the intracellular organization of cells. During polarization of the C. elegans zygote, both polarity proteins and actomyosin regulators associate within dynamic membrane-associated foci. Recently, a novel class of asymmetric membrane-associated structures was described that appeared to be enriched in phosphatidylinositol 4,5-bisphosphate (PIP2), suggesting that PIP2 domains could constitute signaling hubs to promote cell polarization and actin nucleation. Here, we probe the nature of these domains using a variety of membrane- and actin cortex-associated probes. These data demonstrate that these domains are filopodia, which are stimulated transiently during polarity establishment and accumulate in the zygote anterior. The resulting membrane protrusions create local membrane topology that quantitatively accounts for observed local increases in the fluorescence signal of membrane-associated molecules, suggesting molecules are not selectively enriched in these domains relative to bulk membrane and that the PIP2 pool as revealed by PHPLCδ1 simply reflects plasma membrane localization. Given the ubiquity of 3D membrane structures in cells, including filopodia, microvilli and membrane folds, similar caveats are likely to apply to analysis of membrane-associated molecules in a broad range of systems. Summary: Apparent accumulation of PIP2 and cortex/polarity-related proteins within plasma membrane microdomains in polarizing C. elegans zygotes reflects local membrane topology induced by filopodia, not selective enrichment within signaling domains.
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Affiliation(s)
- Nisha Hirani
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | | | - Tom Bland
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.,Institute for the Physics of Living Systems, University College London, London WC1E 6BT, UK
| | - Grégoire Mathonnet
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, UMR7104, Institut National de la Santé et de la Recherche Médicale, U1258, and Université de Strasbourg, 67404 Illkirch, France
| | - Delphine Suhner
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, UMR7104, Institut National de la Santé et de la Recherche Médicale, U1258, and Université de Strasbourg, 67404 Illkirch, France
| | - Anne-Cecile Reymann
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, UMR7104, Institut National de la Santé et de la Recherche Médicale, U1258, and Université de Strasbourg, 67404 Illkirch, France
| | - Nathan W Goehring
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK .,Institute for the Physics of Living Systems, University College London, London WC1E 6BT, UK.,MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
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