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Kay RR, Lutton JE, King JS, Bretschneider T. Making cups and rings: the 'stalled-wave' model for macropinocytosis. Biochem Soc Trans 2024:BST20231426. [PMID: 38934501 DOI: 10.1042/bst20231426] [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: 03/13/2024] [Revised: 05/29/2024] [Accepted: 06/07/2024] [Indexed: 06/28/2024]
Abstract
Macropinocytosis is a broadly conserved endocytic process discovered nearly 100 years ago, yet still poorly understood. It is prominent in cancer cell feeding, immune surveillance, uptake of RNA vaccines and as an invasion route for pathogens. Macropinocytic cells extend large cups or flaps from their plasma membrane to engulf droplets of medium and trap them in micron-sized vesicles. Here they are digested and the products absorbed. A major problem - discussed here - is to understand how cups are shaped and closed. Recently, lattice light-sheet microscopy has given a detailed description of this process in Dictyostelium amoebae, leading to the 'stalled-wave' model for cup formation and closure. This is based on membrane domains of PIP3 and active Ras and Rac that occupy the inner face of macropinocytic cups and are readily visible with suitable reporters. These domains attract activators of dendritic actin polymerization to their periphery, creating a ring of protrusive F-actin around themselves, thus shaping the walls of the cup. As domains grow, they drive a wave of actin polymerization across the plasma membrane that expands the cup. When domains stall, continued actin polymerization under the membrane, combined with increasing membrane tension in the cup, drives closure at lip or base. Modelling supports the feasibility of this scheme. No specialist coat proteins or contractile activities are required to shape and close cups: rings of actin polymerization formed around PIP3 domains that expand and stall seem sufficient. This scheme may be widely applicable and begs many biochemical questions.
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Affiliation(s)
- Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, U.K
| | - Judith E Lutton
- Department of Computer Science, University of Warwick, Coventry CV4 7AL, U.K
| | - Jason S King
- Department of Biomedical Sciences, Western Bank, Sheffield S10 2TN, U.K
| | - Till Bretschneider
- Department of Computer Science, University of Warwick, Coventry CV4 7AL, U.K
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2
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Rioux DJ, Prosser DC. A CIE change in our understanding of endocytic mechanisms. Front Cell Dev Biol 2023; 11:1334798. [PMID: 38192364 PMCID: PMC10773762 DOI: 10.3389/fcell.2023.1334798] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/04/2023] [Indexed: 01/10/2024] Open
Abstract
The past six decades have seen major advances in our understanding of endocytosis, ranging from descriptive studies based on electron microscopy to biochemical and genetic characterization of factors required for vesicle formation. Most studies focus on clathrin as the major coat protein; indeed, clathrin-mediated endocytosis (CME) is the primary pathway for internalization. Clathrin-independent (CIE) pathways also exist, although mechanistic understanding of these pathways remains comparatively elusive. Here, we discuss how early studies of CME shaped our understanding of endocytosis and describe recent advances in CIE, including pathways in model organisms that are poised to provide key insights into endocytic regulation.
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Affiliation(s)
- Daniel J. Rioux
- Life Sciences, Virginia Commonwealth University, Richmond, VA, United States
- Department of Biology, Virginia Commonwealth University, Richmond, VA, United States
| | - Derek C. Prosser
- Department of Biology, Virginia Commonwealth University, Richmond, VA, United States
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3
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Lutton JE, Coker HLE, Paschke P, Munn CJ, King JS, Bretschneider T, Kay RR. Formation and closure of macropinocytic cups in Dictyostelium. Curr Biol 2023; 33:3083-3096.e6. [PMID: 37379843 PMCID: PMC7614961 DOI: 10.1016/j.cub.2023.06.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 05/05/2023] [Accepted: 06/05/2023] [Indexed: 06/30/2023]
Abstract
Macropinocytosis is a conserved endocytic process by which cells engulf droplets of medium into micron-sized vesicles. We use light-sheet microscopy to define an underlying set of principles by which macropinocytic cups are shaped and closed in Dictyostelium amoebae. Cups form around domains of PIP3 stretching almost to their lip and are supported by a specialized F-actin scaffold from lip to base. They are shaped by a ring of actin polymerization created by recruiting Scar/WAVE and Arp2/3 around PIP3 domains, but how cups evolve over time to close and form a vesicle is unknown. Custom 3D analysis shows that PIP3 domains expand from small origins, capturing new membrane into the cup, and crucially, that cups close when domain expansion stalls. We show that cups can close in two ways: either at the lip, by inwardly directed actin polymerization, or the base, by stretching and delamination of the membrane. This provides the basis for a conceptual mechanism whereby closure is brought about by a combination of stalled cup expansion, continued actin polymerization at the lip, and membrane tension. We test this through the use of a biophysical model, which can recapitulate both forms of cup closure and explain how 3D cup structures evolve over time to mediate engulfment.
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Affiliation(s)
- Judith E Lutton
- Department of Computer Science, University of Warwick, Coventry CV4 7AL, UK
| | - Helena L E Coker
- CAMDU, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Peggy Paschke
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | | | - Jason S King
- School of Biosciences, Western Bank, Sheffield S10 2TN, UK.
| | - Till Bretschneider
- Department of Computer Science, University of Warwick, Coventry CV4 7AL, UK.
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
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4
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Salloum G, Bresnick AR, Backer JM. Macropinocytosis: mechanisms and regulation. Biochem J 2023; 480:335-362. [PMID: 36920093 DOI: 10.1042/bcj20210584] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/22/2023] [Accepted: 02/27/2023] [Indexed: 03/16/2023]
Abstract
Macropinocytosis is defined as an actin-dependent but coat- and dynamin-independent endocytic uptake process, which generates large intracellular vesicles (macropinosomes) containing a non-selective sampling of extracellular fluid. Macropinocytosis provides an important mechanism of immune surveillance by dendritic cells and macrophages, but also serves as an essential nutrient uptake pathway for unicellular organisms and tumor cells. This review examines the cell biological mechanisms that drive macropinocytosis, as well as the complex signaling pathways - GTPases, lipid and protein kinases and phosphatases, and actin regulatory proteins - that regulate macropinosome formation, internalization, and disposition.
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Affiliation(s)
- Gilbert Salloum
- Department of Molecular Pharamacology, Albert Einstein College of Medicine, Bronx, NY, U.S.A
| | - Anne R Bresnick
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, U.S.A
| | - Jonathan M Backer
- Department of Molecular Pharamacology, Albert Einstein College of Medicine, Bronx, NY, U.S.A
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, U.S.A
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5
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Diaz-Valencia JD, Estrada-Abreo LA, Rodríguez-Cruz L, Salgado-Aguayo AR, Patiño-López G. Class I Myosins, molecular motors involved in cell migration and cancer. Cell Adh Migr 2022; 16:1-12. [PMID: 34974807 PMCID: PMC8741282 DOI: 10.1080/19336918.2021.2020705] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 12/02/2021] [Accepted: 12/16/2021] [Indexed: 01/13/2023] Open
Abstract
Class I Myosins are a subfamily of motor proteins with ATPase activity and a characteristic structure conserved in all myosins: A N-Terminal Motor Domain, a central Neck and a C terminal Tail domain. Humans have eight genes for these myosins. Class I Myosins have different functions: regulate membrane tension, participate in endocytosis, exocytosis, intracellular trafficking and cell migration. Cell migration is influenced by many cellular components including motor proteins, like myosins. Recently has been reported that changes in myosin expression have an impact on the migration of cancer cells, the formation of infiltrates and metastasis. We propose that class I myosins might be potential markers for future diagnostic, prognostic or even as therapeutic targets in leukemia and other cancers.Abbreviations: Myo1g: Myosin 1g; ALL: Acute Lymphoblastic Leukemia, TH1: Tail Homology 1; TH2: Tail Homology 2; TH3: Tail Homology 3.
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Affiliation(s)
- Juan D. Diaz-Valencia
- Immunology and Proteomics Laboratory, Children’s Hospital of Mexico, Mexico City, Mexico
| | - Laura A. Estrada-Abreo
- Immunology and Proteomics Laboratory, Children’s Hospital of Mexico, Mexico City, Mexico
- Cell Biology and Flow Cytometry Laboratory, Metropolitan Autonomous University, México City, Mexico
| | - Leonor Rodríguez-Cruz
- Cell Biology and Flow Cytometry Laboratory, Metropolitan Autonomous University, México City, Mexico
| | - Alfonso R. Salgado-Aguayo
- Rheumatic Diseases Laboratory, National Institute of Respiratory Diseases “Ismael Cosío Villegas”, Mexico City, Mexico
| | - Genaro Patiño-López
- Immunology and Proteomics Laboratory, Children’s Hospital of Mexico, Mexico City, Mexico
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6
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Abstract
The distinct movements of macropinosome formation and maturation have corresponding biochemical activities which occur in a defined sequence of stages and transitions between those stages. Each stage in the process is regulated by variously phosphorylated derivatives of phosphatidylinositol (PtdIns) which reside in the cytoplasmic face of the membrane lipid bilayer. PtdIns derivatives phosphorylated at the 3' position of the inositol moiety, called 3' phosphoinositides (3'PIs), regulate different stages of the sequence. 3'PIs are synthesized by numerous phosphoinositide 3'-kinases (PI3K) and other lipid kinases and phosphatases, which are themselves regulated by small GTPases of the Ras superfamily. The combined actions of these enzymes localize four principal species of 3'PI to distinct domains of the plasma membrane or to discrete organelles, with distinct biochemical activities confined to those domains. Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) and phosphatidylinositol (3,4)-bisphosphate (PtdIns(3,4)P2) regulate the early stages of macropinosome formation, which include cell surface ruffling and constrictions of circular ruffles which close into macropinosomes. Phosphatidylinositol 3-phosphate (PtdIns3P) regulates macropinosome fusion with other macropinosomes and early endocytic organelles. Phosphatidylinositol (3,5)-bisphosphate (PtdIns(3,5)P2) mediates macropinosome maturation and shrinkage, through loss of ions and water, and subsequent traffic to lysosomes. The different characteristic rates of macropinocytosis in different cell types indicate levels of regulation which may be governed by the cell's capacity to generate 3'PIs.
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Affiliation(s)
- Joel A Swanson
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA.
| | - Nobukazu Araki
- Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa, Japan
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Kay RR, Lutton J, Coker H, Paschke P, King JS, Bretschneider T. The Amoebal Model for Macropinocytosis. Subcell Biochem 2022; 98:41-59. [PMID: 35378702 DOI: 10.1007/978-3-030-94004-1_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Macropinocytosis is a relatively unexplored form of large-scale endocytosis driven by the actin cytoskeleton. Dictyostelium amoebae form macropinosomes from cups extended from the plasma membrane, then digest their contents and absorb the nutrients in the endo-lysosomal system. They use macropinocytosis for feeding, maintaining a high rate of fluid uptake that makes assay and experimentation easy. Mutants collected over the years identify cytoskeletal and signalling proteins required for macropinocytosis. Cups are organized around plasma membrane domains of intense PIP3, Ras and Rac signalling, proper formation of which also depends on the RasGAPs NF1 and RGBARG, PTEN, the PIP3-regulated protein kinases Akt and SGK and their activators PDK1 and TORC2, Rho proteins, plus other components yet to be identified. This PIP3 domain directs dendritic actin polymerization to the extending lip of macropinocytic cups by recruiting a ring of the SCAR/WAVE complex around itself and thus activating the Arp2/3 complex. The dynamics of PIP3 domains are proposed to shape macropinocytic cups from start to finish. The role of the Ras-PI3-kinase module in organizing feeding structures in unicellular organisms most likely predates its adoption into growth factor signalling, suggesting an evolutionary origin for growth factor signalling.
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Affiliation(s)
- Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge, UK.
| | - Josiah Lutton
- Department of Computer Science, University of Warwick, Coventry, UK
| | - Helena Coker
- Warwick Medical School, University of Warwick, Coventry, UK
| | - Peggy Paschke
- MRC Laboratory of Molecular Biology, Cambridge, UK.,Cancer Research UK Beatson Institute, Garscube Estate, Glasgow, UK
| | - Jason S King
- School of Biomedical Sciences, University of Sheffield, Sheffield, UK
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Xie L, Huang H, Zheng Z, Yang Q, Wang S, Chen Y, Yu J, Cui C. MYO1B enhances colorectal cancer metastasis by promoting the F-actin rearrangement and focal adhesion assembly via RhoA/ROCK/FAK signaling. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:1543. [PMID: 34790749 PMCID: PMC8576704 DOI: 10.21037/atm-21-4702] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 10/22/2021] [Indexed: 12/12/2022]
Abstract
Background Colorectal cancer (CRC) has a high worldwide incidence and mortality. Tumor metastasis is one of the primary reasons for the poor prognosis of CRC patients. However, the mechanism underlying CRC metastasis is still unclear. Myosin 1B (MYO1B) is important for cell migration and motility and is part of the myosin superfamily that contains various myosins. Studies of prostate, cervical, and head and neck cancer have revealed preliminary findings concerning the effect of MYO1B on tumor metastasis. However, the role of MYO1B in CRC metastasis, as well as its underlying mechanism, remains unknown. Methods Quantitative real-time PCR and immunohistochemical staining methods were used to analyze the expression of MYO1B in human CRC and normal mucosa tissues. Lentivirus vector-based MYO1B oligonucleotides and short hairpin RNA (shRNA) were used to examine the functional relevance of MYO1B in CRC cells. Co-immunoprecipitation, western blotting, and immunofluorescence assays were used to investigate the underlying mechanism of MYO1B-mediated cell migration. Results The expression of MYO1B was increased in most CRC tissues and was positively associated with a greater risk of tumor metastasis and poor prognosis for patients. MYO1B was significantly associated with the migration and invasion properties of CRC cells in vitro and in vivo. MYO1B promoted F-actin rearrangement through the ROCK2/LIMK/Cofilin axis by enhancing the activation of RhoA. MYO1B also promoted the assembly of focal adhesions by targeting RhoA. Conclusions MYO1B plays a vital role in CRC metastasis by promoting the activation of RhoA. MYO1B may not only be a valid biomarker for predicting the risk of metastasis and poor prognosis in CRC but may also be a potential therapeutic target for patients with a high risk of tumor metastasis.
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Affiliation(s)
- Lang Xie
- Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Hongyun Huang
- Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Zheng Zheng
- Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Qian Yang
- Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Shubo Wang
- The Medical Department, 3D Medicines Inc., Shanghai, China
| | - Yaoxu Chen
- The Medical Department, 3D Medicines Inc., Shanghai, China
| | - Jinlong Yu
- Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Chunhui Cui
- Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
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9
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Schink KO, Tan KW, Spangenberg H, Martorana D, Sneeggen M, Stévenin V, Enninga J, Campsteijn C, Raiborg C, Stenmark H. The phosphoinositide coincidence detector Phafin2 promotes macropinocytosis by coordinating actin organisation at forming macropinosomes. Nat Commun 2021; 12:6577. [PMID: 34772942 PMCID: PMC8590015 DOI: 10.1038/s41467-021-26775-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 10/08/2021] [Indexed: 01/14/2023] Open
Abstract
Uptake of large volumes of extracellular fluid by actin-dependent macropinocytosis has an important role in infection, immunity and cancer development. A key question is how actin assembly and disassembly are coordinated around macropinosomes to allow them to form and subsequently pass through the dense actin network underlying the plasma membrane to move towards the cell center for maturation. Here we show that the PH and FYVE domain protein Phafin2 is recruited transiently to newly-formed macropinosomes by a mechanism that involves coincidence detection of PtdIns3P and PtdIns4P. Phafin2 also interacts with actin via its PH domain, and recruitment of Phafin2 coincides with actin reorganization around nascent macropinosomes. Moreover, forced relocalization of Phafin2 to the plasma membrane causes rearrangement of the subcortical actin cytoskeleton. Depletion of Phafin2 inhibits macropinosome internalization and maturation and prevents KRAS-transformed cancer cells from utilizing extracellular protein as an amino acid source. We conclude that Phafin2 promotes macropinocytosis by controlling timely delamination of actin from nascent macropinosomes for their navigation through the dense subcortical actin network.
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Affiliation(s)
- Kay Oliver Schink
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway.
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway.
| | - Kia Wee Tan
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway
| | - Hélène Spangenberg
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway
| | - Domenica Martorana
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway
| | - Marte Sneeggen
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway
| | - Virginie Stévenin
- Department of Cell and Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France
| | - Jost Enninga
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France
| | - Coen Campsteijn
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, PO Box 1112 Blindern, 0317, Oslo, Norway
| | - Camilla Raiborg
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway.
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0379, Oslo, Norway.
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10
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Saito N, Sawai S. Three-dimensional morphodynamic simulations of macropinocytic cups. iScience 2021; 24:103087. [PMID: 34755081 PMCID: PMC8560551 DOI: 10.1016/j.isci.2021.103087] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 08/13/2021] [Accepted: 09/01/2021] [Indexed: 12/02/2022] Open
Abstract
Macropinocytosis refers to the non-specific uptake of extracellular fluid, which plays ubiquitous roles in cell growth, immune surveillance, and virus entry. Despite its widespread occurrence, it remains unclear how its initial cup-shaped plasma membrane extensions form without any external solid support, as opposed to the process of particle uptake during phagocytosis. Here, by developing a computational framework that describes the coupling between the bistable reaction-diffusion processes of active signaling patches and membrane deformation, we demonstrated that the protrusive force localized to the edge of the patches can give rise to a self-enclosing cup structure, without further assumptions of local bending or contraction. Efficient uptake requires a balance among the patch size, magnitude of protrusive force, and cortical tension. Furthermore, our model exhibits cyclic cup formation, coexistence of multiple cups, and cup-splitting, indicating that these complex morphologies self-organize via a common mutually-dependent process of reaction-diffusion and membrane deformation.
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Affiliation(s)
- Nen Saito
- Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Satoshi Sawai
- Department of Basic Science, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
- Research Center for Complex Systems Biology, Graduate School of Arts and Sciences, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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11
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Brzeska H, Bagnoli M, Korn ED, Titus MA. Dictyostelium myosin 1F and myosin 1E inhibit actin waves in a lipid-binding-dependent and motor-independent manner. Cytoskeleton (Hoboken) 2021; 77:295-302. [PMID: 32734648 DOI: 10.1002/cm.21627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 07/21/2020] [Accepted: 07/24/2020] [Indexed: 12/23/2022]
Abstract
Actin waves are F-actin-rich entities traveling on the ventral plasma membrane by the treadmilling mechanism. Actin waves were first discovered and are best characterized in Dictyostelium. Class I myosins are unconventional monomeric myosins that bind lipids through their tails. Dictyostelium has seven class I myosins, six of these have tails (Myo1A-F) while one has a very short tail (Myo1K), and three of them (Myo1D, Myo1E and Myo1F) bind PIP3 with high affinity. Localization of five Dictyostelium Class I myosins synchronizes with localization and propagation of actin waves. Myo1B and Myo1C colocalize with actin in actin waves, whereas Myo1D, E and F localize to the PIP3-rich region surrounded by actin waves. Here, we studied the effect of overexpression of the three PIP3 specific Class I myosins on actin waves. We found that ectopic expression of the short-tail Myo1F inhibits wave formation, short-tail Myo1E has similar but weaker inhibitory effect, but long-tail Myo1D does not affect waves. A study of Myo1F mutants shows that its membrane-binding site is absolutely required for wave inhibition, but the head portion is not. The results suggest that PIP3 specificity and the presence of two membrane-binding sites are required for inhibition of actin waves, and that inhibition may be caused by crosslinking of PIP3 heads groups.
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Affiliation(s)
- Hanna Brzeska
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Michael Bagnoli
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Edward D Korn
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Margaret A Titus
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, USA
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12
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Kay RR. Macropinocytosis: Biology and mechanisms. Cells Dev 2021; 168:203713. [PMID: 34175511 DOI: 10.1016/j.cdev.2021.203713] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/25/2021] [Accepted: 06/21/2021] [Indexed: 12/24/2022]
Abstract
Macropinocytosis is a form of endocytosis performed by ruffles and cups of the plasma membrane. These close to entrap droplets of medium into micron-sized vesicles, which are trafficked through the endocytic system, their contents digested and useful products absorbed. Macropinocytosis is constitutive in certain immune cells and stimulated in many other cells by growth factors. It occurs across the animal kingdom and in amoebae, implying a deep evolutionary history. Its scientific history goes back 100 years, but increasingly work is focused on its medical importance in the immune system, cancer cell feeding, and as a backdoor into cells for viruses and drugs. Macropinocytosis is driven by the actin cytoskeleton whose dynamics can be appreciated with lattice light sheet microscopy: this reveals a surprising variety of routes for forming macropinosomes. In Dictyostelium amoebae, macropinocytic cups are organized around domains of PIP3 and active Ras and Rac in the plasma membrane. These attract activators of the Arp2/3 complex to their periphery, creating rings of actin polymerization that shape the cups. The size of PIP3 domains is controlled by RasGAPs, such as NF1, and the lipid phosphatase, PTEN. It is likely that domain dynamics determine the shape, evolution and closing of macropinocytic structures.
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Affiliation(s)
- Robert R Kay
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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13
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Yang Y, Li D, Chao X, Singh SP, Thomason P, Yan Y, Dong M, Li L, Insall RH, Cai H. Leep1 interacts with PIP3 and the Scar/WAVE complex to regulate cell migration and macropinocytosis. J Cell Biol 2021; 220:212090. [PMID: 33978708 PMCID: PMC8127007 DOI: 10.1083/jcb.202010096] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 03/23/2021] [Accepted: 04/21/2021] [Indexed: 12/20/2022] Open
Abstract
Polarity is essential for diverse functions in many cell types. Establishing polarity requires targeting a network of specific signaling and cytoskeleton molecules to different subregions of the cell, yet the full complement of polarity regulators and how their activities are integrated over space and time to form morphologically and functionally distinct domains remain to be uncovered. Here, by using the model system Dictyostelium and exploiting the characteristic chemoattractant-stimulated translocation of polarly distributed molecules, we developed a proteomic screening approach, through which we identified a leucine-rich repeat domain–containing protein we named Leep1 as a novel polarity regulator. We combined imaging, biochemical, and phenotypic analyses to demonstrate that Leep1 localizes selectively at the leading edge of cells by binding to PIP3, where it modulates pseudopod and macropinocytic cup dynamics by negatively regulating the Scar/WAVE complex. The spatiotemporal coordination of PIP3 signaling, Leep1, and the Scar/WAVE complex provides a cellular mechanism for organizing protrusive structures at the leading edge.
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Affiliation(s)
- Yihong Yang
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Dong Li
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Xiaoting Chao
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Shashi P Singh
- Cancer Research UK Beatson Institute, Glasgow, UK.,University of Glasgow Institute of Cancer Sciences, Glasgow, UK
| | - Peter Thomason
- Cancer Research UK Beatson Institute, Glasgow, UK.,University of Glasgow Institute of Cancer Sciences, Glasgow, UK
| | - Yonghong Yan
- National Institute of Biological Sciences, Beijing, China
| | - Mengqiu Dong
- National Institute of Biological Sciences, Beijing, China
| | - Lei Li
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Robert H Insall
- Cancer Research UK Beatson Institute, Glasgow, UK.,University of Glasgow Institute of Cancer Sciences, Glasgow, UK
| | - Huaqing Cai
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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14
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Brzeska H, Gonzalez J, Korn ED, Titus MA. Basic-hydrophobic sites are localized in conserved positions inside and outside of PH domains and affect localization of Dictyostelium myosin 1s. Mol Biol Cell 2020; 31:101-117. [PMID: 31774725 PMCID: PMC6960411 DOI: 10.1091/mbc.e19-08-0475] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/14/2019] [Accepted: 11/22/2019] [Indexed: 11/21/2022] Open
Abstract
Myosin 1s have critical roles in linking membranes to the actin cytoskeleton via direct binding to acidic lipids. Lipid binding may occur through PIP3/PIP2-specific PH domains or nonspecific ionic interactions involving basic-hydrophobic (BH) sites but the mechanism of myosin 1s distinctive lipid targeting is poorly understood. Now we show that PH domains occur in all Dictyostelium myosin 1s and that the BH sites of Myo1A, B, C, D, and F are in conserved positions near the β3/β4 loops of their PH domains. In spite of these shared lipid-binding sites, we observe significant differences in myosin 1s highly dynamic localizations. All myosin 1s except Myo1A are present in macropinocytic structures but only Myo1B and Myo1C are enriched at the edges of macropinocytic cups and associate with the actin in actin waves. In contrast, Myo1D, E, and F are enclosed by the actin wave. Mutations of BH sites affect localization of all Dictyostelium myosin 1s. Notably, mutation of the BH site located within the PH domains of PIP3-specific Myo1D and Myo1F completely eradicates membrane binding. Thus, BH sites are important determinants of motor targeting and may have a similar role in the localization of other myosin 1s.
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Affiliation(s)
- Hanna Brzeska
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Jesus Gonzalez
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Edward D. Korn
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Margaret A. Titus
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455
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15
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Zhang Y, Jiang X, Deng Q, Gao Z, Tang X, Fu R, Hu J, Li Y, Li L, Gao N. Downregulation of MYO1C mediated by cepharanthine inhibits autophagosome-lysosome fusion through blockade of the F-actin network. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2019; 38:457. [PMID: 31699152 PMCID: PMC6836678 DOI: 10.1186/s13046-019-1449-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 10/15/2019] [Indexed: 01/10/2023]
Abstract
Background MYO1C, an actin-based motor protein, is involved in the late stages of autophagosome maturation and fusion with the lysosome. The molecular mechanism by which MYO1C regulates autophagosome-lysosome fusion remains largely unclear. Methods Western blotting was used to determine the expression of autophagy-related proteins. Transmission electron microscopy (TEM) was used to observe the ultrastructural changes. An immunoprecipitation assay was utilized to detect protein-protein interactions. Immunofluorescence analysis was used to detect autophagosome-lysosome fusion and colocalization of autophagy-related molecules. An overexpression plasmid or siRNA against MYO1C were sequentially introduced into human breast cancer MDA-MB-231 cells. Results We show here that cepharanthine (CEP), a novel autophagy inhibitor, inhibited autophagy/mitophagy through blockage of autophagosome-lysosome fusion in human breast cancer cells. Mechanistically, we found for the first time that MYO1C was downregulated by CEP treatment. Furthermore, the interaction/colocalization of MYO1C and F-actin with either LC3 or LAMP1 was inhibited by CEP treatment. Knockdown of MYO1C further decreased the interaction/colocalization of MYO1C and F-actin with either LC3 or LAMP1 inhibited by CEP treatment, leading to blockade of autophagosome-lysosome fusion. In contrast, overexpression of MYO1C significantly restored the interaction/colocalization of MYO1C and F-actin with either LC3 or LAMP1 inhibited by CEP treatment. Conclusion These findings highlight a key role of MYO1C in the regulation of autophagosome-lysosome fusion through F-actin remodeling. Our findings also suggest that CEP could potentially be further developed as a novel autophagy/mitophagy inhibitor, and a combination of CEP with classic chemotherapeutic drugs could become a promising treatment for breast cancer.
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Affiliation(s)
- Yanhao Zhang
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Xiuxing Jiang
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Qin Deng
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Ziyi Gao
- Greater Philadelphia Pharmacy, Philadelphia, USA
| | - Xiangyu Tang
- Biomedical Analysis Center, Army Medical University, Chongqing, 400038, China
| | - Ruoqiu Fu
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Jinjiao Hu
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Yunong Li
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Lirong Li
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China
| | - Ning Gao
- College of Pharmacy, Army Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, China. .,Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi, China.
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16
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Girón-Pérez DA, Piedra-Quintero ZL, Santos-Argumedo L. Class I myosins: Highly versatile proteins with specific functions in the immune system. J Leukoc Biol 2019; 105:973-981. [PMID: 30821871 DOI: 10.1002/jlb.1mr0918-350rrr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 02/04/2019] [Accepted: 02/06/2019] [Indexed: 12/20/2022] Open
Abstract
Connections established between cytoskeleton and plasma membrane are essential in cellular processes such as cell migration, vesicular trafficking, and cytokinesis. Class I myosins are motor proteins linking the actin-cytoskeleton with membrane phospholipids. Previous studies have implicated these molecules in cell functions including endocytosis, exocytosis, release of extracellular vesicles and the regulation of cell shape and membrane elasticity. In immune cells, those proteins also are involved in the formation and maintenance of immunological synapse-related signaling. Thus, these proteins are master regulators of actin cytoskeleton dynamics in different scenarios. Although the localization of class I myosins has been described in vertebrates, their functions, regulation, and mechanical properties are not very well understood. In this review, we focused on and summarized the current understanding of class I myosins in vertebrates with particular emphasis in leukocytes.
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Affiliation(s)
- Daniel Alberto Girón-Pérez
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, México
| | - Zayda Lizbeth Piedra-Quintero
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, México
| | - Leopoldo Santos-Argumedo
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, México
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17
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Abstract
In macropinocytosis, cells take up micrometre-sized droplets of medium into internal vesicles. These vesicles are acidified and fused to lysosomes, their contents digested and useful compounds extracted. Indigestible contents can be exocytosed. Macropinocytosis has been known for approaching 100 years and is described in both metazoa and amoebae, but not in plants or fungi. Its evolutionary origin goes back to at least the common ancestor of the amoebozoa and opisthokonts, with apparent secondary loss from fungi. The primary function of macropinocytosis in amoebae and some cancer cells is feeding, but the conserved processing pathway for macropinosomes, which involves shrinkage and the retrieval of membrane to the cell surface, has been adapted in immune cells for antigen presentation. Macropinocytic cups are large actin-driven processes, closely related to phagocytic cups and pseudopods and appear to be organized around a conserved signalling patch of PIP3, active Ras and active Rac that directs actin polymerization to its periphery. Patches can form spontaneously and must be sustained by excitable kinetics with strong cooperation from the actin cytoskeleton. Growth-factor signalling shares core components with macropinocytosis, based around phosphatidylinositol 3-kinase (PI3-kinase), and we suggest that it evolved to take control of ancient feeding structures through a coupled growth factor receptor. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
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Affiliation(s)
- Jason S. King
- Department of Biomedical Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Robert R. Kay
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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18
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Williams TD, Peak-Chew SY, Paschke P, Kay RR. Akt and SGK protein kinases are required for efficient feeding by macropinocytosis. J Cell Sci 2019; 132:jcs.224998. [PMID: 30617109 DOI: 10.1242/jcs.224998] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 12/19/2018] [Indexed: 12/20/2022] Open
Abstract
Macropinocytosis is an actin-driven process of large-scale and non-specific fluid uptake used for feeding by some cancer cells and the macropinocytosis model organism Dictyostelium discoideum In Dictyostelium, macropinocytic cups are organized by 'macropinocytic patches' in the plasma membrane. These contain activated Ras, Rac and phospholipid PIP3, and direct actin polymerization to their periphery. We show that a Dictyostelium Akt (PkbA) and an SGK (PkbR1) protein kinase act downstream of PIP3 and, together, are nearly essential for fluid uptake. This pathway enables the formation of larger macropinocytic patches and macropinosomes, thereby dramatically increasing fluid uptake. Through phosphoproteomics, we identify a RhoGAP, GacG, as a PkbA and PkbR1 target, and show that it is required for efficient macropinocytosis and expansion of macropinocytic patches. The function of Akt and SGK in cell feeding through control of macropinosome size has implications for cancer cell biology.
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Affiliation(s)
| | | | - Peggy Paschke
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
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19
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Actin Waves: Origin of Cell Polarization and Migration? Trends Cell Biol 2017; 27:515-526. [DOI: 10.1016/j.tcb.2017.02.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/26/2017] [Accepted: 02/07/2017] [Indexed: 01/22/2023]
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20
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Veltman DM, Williams TD, Bloomfield G, Chen BC, Betzig E, Insall RH, Kay RR. A plasma membrane template for macropinocytic cups. eLife 2016; 5:e20085. [PMID: 27960076 PMCID: PMC5154761 DOI: 10.7554/elife.20085] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/14/2016] [Indexed: 12/18/2022] Open
Abstract
Macropinocytosis is a fundamental mechanism that allows cells to take up extracellular liquid into large vesicles. It critically depends on the formation of a ring of protrusive actin beneath the plasma membrane, which develops into the macropinocytic cup. We show that macropinocytic cups in Dictyostelium are organised around coincident intense patches of PIP3, active Ras and active Rac. These signalling patches are invariably associated with a ring of active SCAR/WAVE at their periphery, as are all examined structures based on PIP3 patches, including phagocytic cups and basal waves. Patch formation does not depend on the enclosing F-actin ring, and patches become enlarged when the RasGAP NF1 is mutated, showing that Ras plays an instructive role. New macropinocytic cups predominantly form by splitting from existing ones. We propose that cup-shaped plasma membrane structures form from self-organizing patches of active Ras/PIP3, which recruit a ring of actin nucleators to their periphery.
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Affiliation(s)
- Douwe M Veltman
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
- Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | | | | | - Bi-Chang Chen
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Eric Betzig
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Robert H Insall
- Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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21
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A Diaphanous-related formin links Ras signaling directly to actin assembly in macropinocytosis and phagocytosis. Proc Natl Acad Sci U S A 2016; 113:E7464-E7473. [PMID: 27821733 DOI: 10.1073/pnas.1611024113] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Phagocytosis and macropinocytosis are Ras-regulated and actin-driven processes that depend on the dynamic rearrangements of the plasma membrane that protrudes and internalizes extracellular material by cup-shaped structures. However, the regulatory mechanisms underlying actin assembly in large-scale endocytosis remain elusive. Here, we show that the Diaphanous-related formin G (ForG) from the professional phagocyte Dictyostelium discoideum localizes to endocytic cups. Biochemical analyses revealed that ForG is a rather weak nucleator but efficiently elongates actin filaments in the presence of profilin. Notably, genetic inactivation of ForG is associated with a strongly impaired endocytosis and a markedly diminished F-actin content at the base of the cups. By contrast, ablation of the Arp2/3 (actin-related protein-2/3) complex activator SCAR (suppressor of cAMP receptor) diminishes F-actin mainly at the cup rim, being consistent with its known localization. These data therefore suggest that ForG acts as an actin polymerase of Arp2/3-nucleated filaments to allow for efficient membrane expansion and engulfment of extracellular material. Finally, we show that ForG is directly regulated in large-scale endocytosis by RasB and RasG, which are highly related to the human proto-oncogene KRas.
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22
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Ha KD, Bidlingmaier SM, Liu B. Macropinocytosis Exploitation by Cancers and Cancer Therapeutics. Front Physiol 2016; 7:381. [PMID: 27672367 PMCID: PMC5018483 DOI: 10.3389/fphys.2016.00381] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/22/2016] [Indexed: 12/19/2022] Open
Abstract
Macropinocytosis has long been known as a primary method for cellular intake of fluid-phase and membrane-bound bulk cargo. This review seeks to re-examine the latest studies to emphasize how cancers exploit macropinocytosis to further their tumorigenesis, including details in how macropinocytosis can be adapted to serve diverse functions. Furthermore, this review will also cover the latest endeavors in targeting macropinocytosis as an avenue for novel therapeutics.
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Affiliation(s)
- Kevin D Ha
- Department of Anesthesia, UCSF Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco San Francisco, CA, USA
| | - Scott M Bidlingmaier
- Department of Anesthesia, UCSF Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco San Francisco, CA, USA
| | - Bin Liu
- Department of Anesthesia, UCSF Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco San Francisco, CA, USA
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23
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Abstract
Macropinocytosis is a means by which eukaryotic cells ingest extracellular liquid and dissolved molecules. It is widely conserved amongst cells that can take on amoeboid form and, therefore, appears to be an ancient feature that can be traced back to an early stage of evolution. Recent advances have highlighted how this endocytic process can be subverted during pathology - certain cancer cells use macropinocytosis to feed on extracellular protein, and many viruses and bacteria use it to enter host cells. Prion and prion-like proteins can also spread and propagate from cell to cell through macropinocytosis. Progress is being made towards using macropinocytosis therapeutically, either to deliver drugs to or cause cell death by inducing catastrophically rapid fluid uptake. Mechanistically, the Ras signalling pathway plays a prominent and conserved activating role in amoebae and in mammals; mutant amoebae with abnormally high Ras activity resemble tumour cells in their increased capacity for growth using nutrients ingested through macropinocytosis. This Commentary takes a functional and evolutionary perspective to highlight progress in understanding and use of macropinocytosis, which is an ancient feeding process used by single-celled phagotrophs that has now been put to varied uses by metazoan cells and is abused in disease states, including infection and cancer.
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Affiliation(s)
- Gareth Bloomfield
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
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