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Zhou Q, Zhang Q, Liao L, Li Q, Qu H, Wang X, Zhou Y, Zhang G, Sun M, Zhang K, Zhang B. Isocorydine Exerts Anticancer Activity by Disrupting the Energy Metabolism and Filamentous Actin Structures of Oral Squamous Carcinoma Cells. Curr Issues Mol Biol 2024; 46:650-662. [PMID: 38248344 PMCID: PMC10814041 DOI: 10.3390/cimb46010042] [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: 11/18/2023] [Revised: 12/17/2023] [Accepted: 12/22/2023] [Indexed: 01/23/2024] Open
Abstract
Isocorydine (ICD) exhibits strong antitumor effects on numerous human cell lines. However, the anticancer activity of ICD against oral squamous cell carcinoma (OSCC) has not been reported. The anticancer activity, migration and invasion ability, and changes in the cytoskeleton morphology and mechanical properties of ICD in OSCC were determined. Changes in the contents of reactive oxygen species (ROS), the mitochondrial membrane potential (MMP), ATP, and mitochondrial respiratory chain complex enzymes Ⅰ-Ⅳ in cancer cells were studied. ICD significantly inhibited the proliferation of oral tongue squamous cells (Cal-27), with an IC50 of 0.61 mM after 24 h of treatment. The invasion, migration, and adhesion of cancer cells were decreased, and cytoskeletal actin was deformed and depolymerized. In comparison to an untreated group, the activities of mitochondrial respiratory chain complex enzymes I-IV were significantly decreased by 50.72%, 27.39%, 77.27%, and 73.89%, respectively. The ROS production increased, the MMP decreased by 43.65%, and the ATP content decreased to 17.1 ± 0.001 (mmol/mL); ultimately, the apoptosis rate of cancer cells increased up to 10.57% after 24 h of action. These findings suggest that ICD exerted an obvious anticancer activity against OSCC and may inhibit Cal-27 proliferation and growth by causing mitochondrial dysfunction and interrupting cellular energy.
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Affiliation(s)
- Qiaozhen Zhou
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Qianqian Zhang
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Lingzi Liao
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Qian Li
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Huidan Qu
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Xinyu Wang
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Ying Zhou
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Guangzeng Zhang
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Mingliang Sun
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
| | - Kailiang Zhang
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
- Key Laboratory of Dental Maxillofacial Reconstruction and Biological Intelligence Manufacturing, Lanzhou University, Lanzhou 730000, China
| | - Baoping Zhang
- Department (Hospital) of Stomatology, Lanzhou University, Lanzhou 730000, China; (Q.Z.); (Q.Z.); (L.L.); (Q.L.); (H.Q.); (X.W.); (Y.Z.); (G.Z.); (M.S.)
- Key Laboratory of Dental Maxillofacial Reconstruction and Biological Intelligence Manufacturing, Lanzhou University, Lanzhou 730000, China
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2
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Narvaez-Ortiz HY, Nolen BJ. Unconcerted conformational changes in Arp2/3 complex integrate multiple activating signals to assemble functional actin networks. Curr Biol 2022; 32:975-987.e6. [PMID: 35090589 PMCID: PMC8930562 DOI: 10.1016/j.cub.2022.01.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/25/2021] [Accepted: 01/04/2022] [Indexed: 11/16/2022]
Abstract
Arp2/3 complex nucleates branched actin filaments important for processes such as DNA repair, endocytosis, and cellular motility. Multiple factors are required to activate branching nucleation by Arp2/3 complex, including a WASP family protein and a pre-existing actin filament. Activation is achieved through two major conformational changes-subunit flattening and movement into the short pitch conformation-that allow the actin-related proteins (Arps) within the complex (Arp2 and Arp3) to mimic filamentous actin subunits, thereby templating new filament assembly. Some models suggest that these changes are concerted and stimulated cooperatively by WASP and actin filaments, but how Arp2/3 complex integrates signals from multiple factors to drive switch-like activation of branching nucleation has been unknown. Here, we use biochemical assays to show that instead of a concerted mechanism, signal integration by Arp2/3 complex occurs via distinct and unconcerted conformational changes; WASP stimulates the short pitch arrangement of Arp2 and Arp3, while actin filaments trigger a different activation step. An engineered Arp2/3 complex that bypasses the need for WASP but not actin filaments in activation potently assembles isotropic actin networks but fails to assemble sustained force-producing actin networks in bead motility assays. The engineered complex, which is crosslinked into the short pitch conformation, fails to target nucleation to the surface of the bead, creating unproductive branching events that deplete unpolymerized actin and halt assembly. Together, our data demonstrate the requirement for multifactor signal integration by Arp2/3 complex and highlight the importance of both the WASP- and actin filament-mediated activation steps in the assembly of functional actin networks.
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Affiliation(s)
- Heidy Y Narvaez-Ortiz
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Brad J Nolen
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
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3
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Autism, heparan sulfate and potential interventions. Exp Neurol 2022; 353:114050. [DOI: 10.1016/j.expneurol.2022.114050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 02/25/2022] [Accepted: 03/13/2022] [Indexed: 11/16/2022]
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4
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Ahmed S, Kim Y. PGE 2 mediates hemocyte-spreading behavior by activating aquaporin via cAMP and rearranging actin cytoskeleton via Ca 2. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2021; 125:104230. [PMID: 34388674 DOI: 10.1016/j.dci.2021.104230] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/04/2021] [Accepted: 08/08/2021] [Indexed: 06/13/2023]
Abstract
Spreading behavior of hemocytes (= insect blood cells) is essential for cellular immune responses against various microbial pathogens. It is activated by prostaglandin E2 (PGE2) via its membrane receptor associated with secondary messenger, cAMP, in insects. This study observed an increase of calcium ion (Ca2+) level after an acute increase of cAMP induced by PGE2 treatment and clarified the intracellular signals underlying the hemocyte-spreading behavior. Inhibition of Ca2+ flux significantly impaired the hemocyte-spreading and subsequent cellular immune response, phagocytosis. The up-regulation of intracellular Ca2+ in response to PGE2 was dependent on cAMP because RNA interference (RNAi) of PGE2 receptor expression or inhibiting adenylate cyclase prevented Ca2+ mobilization. The up-regulation of Ca2+ was induced by inositol triphosphate (IP3) via its specific IP3 receptor. Furthermore, inhibition of ryanodine receptor impaired Ca2+ mobilization, suggesting Ca2+-induced Ca2+ release. However, the effective spreading behavior of hemocytes was dependent on both secondary messengers. Ca2+ signal stimulated by cAMP was required for activating small G proteins because RNAi treatments of small G proteins such as Rac1, RhoA, and Cdc42 failed to stimulate hemocyte-spreading. In contrast, aquaporin was activated by cAMP. Its activity was necessary for changing cell volume during hemocyte-spreading. These results indicate that PGE2 mediates hemocyte-spreading via cAMP signal to activate aquaporin and via Ca2+ signal to activate actin cytoskeletal rearrangement.
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Affiliation(s)
- Shabbir Ahmed
- Department of Plant Medicals, Andong National University, Andong, 36729, South Korea
| | - Yonggyun Kim
- Department of Plant Medicals, Andong National University, Andong, 36729, South Korea.
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5
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Law AL, Jalal S, Pallett T, Mosis F, Guni A, Brayford S, Yolland L, Marcotti S, Levitt JA, Poland SP, Rowe-Sampson M, Jandke A, Köchl R, Pula G, Ameer-Beg SM, Stramer BM, Krause M. Nance-Horan Syndrome-like 1 protein negatively regulates Scar/WAVE-Arp2/3 activity and inhibits lamellipodia stability and cell migration. Nat Commun 2021; 12:5687. [PMID: 34584076 PMCID: PMC8478917 DOI: 10.1038/s41467-021-25916-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 09/03/2021] [Indexed: 12/02/2022] Open
Abstract
Cell migration is important for development and its aberrant regulation contributes to many diseases. The Scar/WAVE complex is essential for Arp2/3 mediated lamellipodia formation during mesenchymal cell migration and several coinciding signals activate it. However, so far, no direct negative regulators are known. Here we identify Nance-Horan Syndrome-like 1 protein (NHSL1) as a direct binding partner of the Scar/WAVE complex, which co-localise at protruding lamellipodia. This interaction is mediated by the Abi SH3 domain and two binding sites in NHSL1. Furthermore, active Rac binds to NHSL1 at two regions that mediate leading edge targeting of NHSL1. Surprisingly, NHSL1 inhibits cell migration through its interaction with the Scar/WAVE complex. Mechanistically, NHSL1 may reduce cell migration efficiency by impeding Arp2/3 activity, as measured in cells using a Arp2/3 FRET-FLIM biosensor, resulting in reduced F-actin density of lamellipodia, and consequently impairing the stability of lamellipodia protrusions.
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Affiliation(s)
- Ah-Lai Law
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
- School of Life Sciences, University of Bedfordshire, Luton, LU1 3JU, UK
| | - Shamsinar Jalal
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Tommy Pallett
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Fuad Mosis
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Ahmad Guni
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Simon Brayford
- Stramer Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Lawrence Yolland
- Stramer Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Stefania Marcotti
- Stramer Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - James A Levitt
- Ameer-Beg Group, Richard Dimbleby Cancer Research Laboratories, Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Simon P Poland
- Ameer-Beg Group, Richard Dimbleby Cancer Research Laboratories, Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Maia Rowe-Sampson
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
- Stramer Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Anett Jandke
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
- Immunosurveillance Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Robert Köchl
- School of Immunology and Microbial Sciences, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - Giordano Pula
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg (UKE), Martinistrasse 52, O26, 20246, Hamburg, Germany
| | - Simon M Ameer-Beg
- Ameer-Beg Group, Richard Dimbleby Cancer Research Laboratories, Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Brian Marc Stramer
- Stramer Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Matthias Krause
- Krause Group, Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
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6
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Actin filament debranching regulates cell polarity during cell migration and asymmetric cell division. Proc Natl Acad Sci U S A 2021; 118:2100805118. [PMID: 34507987 DOI: 10.1073/pnas.2100805118] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2021] [Indexed: 01/10/2023] Open
Abstract
The formation of the branched actin networks is essential for cell polarity, but it remains unclear how the debranching activity of actin filaments contributes to this process. Here, we showed that an evolutionarily conserved coronin family protein, the Caenorhabditis elegans POD-1, debranched the Arp2/3-nucleated actin filaments in vitro. By fluorescence live imaging analysis of the endogenous POD-1 protein, we found that POD-1 colocalized with Arp2/3 at the leading edge of the migrating C. elegans neuroblasts. Conditional mutations of POD-1 in neuroblasts caused aberrant actin assembly, disrupted cell polarity, and impaired cell migration. In C. elegans one-cell-stage embryos, POD-1 and Arp2/3, moved together during cell polarity establishment, and inhibition of POD-1 blocked Arp2/3 motility and affected the polarized cortical flow, leading to symmetric segregation of cell fate determinants. Together, these results indicate that F-actin debranching organizes actin network and cell polarity in migrating neuroblasts and asymmetrically dividing embryos.
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7
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Fäßler F, Dimchev G, Hodirnau VV, Wan W, Schur FKM. Cryo-electron tomography structure of Arp2/3 complex in cells reveals new insights into the branch junction. Nat Commun 2020; 11:6437. [PMID: 33353942 PMCID: PMC7755917 DOI: 10.1038/s41467-020-20286-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 11/24/2020] [Indexed: 12/21/2022] Open
Abstract
The actin-related protein (Arp)2/3 complex nucleates branched actin filament networks pivotal for cell migration, endocytosis and pathogen infection. Its activation is tightly regulated and involves complex structural rearrangements and actin filament binding, which are yet to be understood. Here, we report a 9.0 Å resolution structure of the actin filament Arp2/3 complex branch junction in cells using cryo-electron tomography and subtomogram averaging. This allows us to generate an accurate model of the active Arp2/3 complex in the branch junction and its interaction with actin filaments. Notably, our model reveals a previously undescribed set of interactions of the Arp2/3 complex with the mother filament, significantly different to the previous branch junction model. Our structure also indicates a central role for the ArpC3 subunit in stabilizing the active conformation.
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Affiliation(s)
- Florian Fäßler
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | - Georgi Dimchev
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | | | - William Wan
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, United States of America
| | - Florian K M Schur
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria.
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8
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Shaaban M, Chowdhury S, Nolen BJ. Cryo-EM reveals the transition of Arp2/3 complex from inactive to nucleation-competent state. Nat Struct Mol Biol 2020; 27:1009-1016. [PMID: 32839613 DOI: 10.1038/s41594-020-0481-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 07/10/2020] [Indexed: 12/29/2022]
Abstract
Arp2/3 complex, a crucial actin filament nucleator, undergoes structural rearrangements during activation by nucleation-promoting factors (NPFs). However, the conformational pathway leading to the nucleation-competent state is unclear due to lack of high-resolution structures of the activated state. Here we report a ~3.9 Å resolution cryo-EM structure of activated Schizosaccharomyces pombe Arp2/3 complex bound to the S. pombe NPF Dip1 and attached to the end of the nucleated actin filament. The structure reveals global and local conformational changes that allow the two actin-related proteins in Arp2/3 complex to mimic a filamentous actin dimer and template nucleation. Activation occurs through a clamp-twisting mechanism, in which Dip1 forces two core subunits in Arp2/3 complex to pivot around one another, shifting half of the complex into a new activated position. By showing how Dip1 stimulates activation, the structure reveals how NPFs can activate Arp2/3 complex in diverse cellular processes.
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Affiliation(s)
- Mohammed Shaaban
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
| | - Saikat Chowdhury
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA.
| | - Brad J Nolen
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, USA.
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9
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Merino F, Pospich S, Raunser S. Towards a structural understanding of the remodeling of the actin cytoskeleton. Semin Cell Dev Biol 2019; 102:51-64. [PMID: 31836290 PMCID: PMC7221352 DOI: 10.1016/j.semcdb.2019.11.018] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 12/03/2022]
Abstract
Actin filaments (F-actin) are a key component of eukaryotic cells. Whether serving as a scaffold for myosin or using their polymerization to push onto cellular components, their function is always related to force generation. To control and fine-tune force production, cells have a large array of actin-binding proteins (ABPs) dedicated to control every aspect of actin polymerization, filament localization, and their overall mechanical properties. Although great advances have been made in our biochemical understanding of the remodeling of the actin cytoskeleton, the structural basis of this process is still being deciphered. In this review, we summarize our current understanding of this process. We outline how ABPs control the nucleation and disassembly, and how these processes are affected by the nucleotide state of the filaments. In addition, we highlight recent advances in the understanding of actomyosin force generation, and describe recent advances brought forward by the developments of electron cryomicroscopy.
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Affiliation(s)
- Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Sabrina Pospich
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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10
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López CA, Swift MF, Xu XP, Hanein D, Volkmann N, Gnanakaran S. Biophysical Characterization of a Nanodisc with and without BAX: An Integrative Study Using Molecular Dynamics Simulations and Cryo-EM. Structure 2019; 27:988-999.e4. [DOI: 10.1016/j.str.2019.03.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 12/21/2018] [Accepted: 03/15/2019] [Indexed: 10/27/2022]
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11
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Markwell SM, Ammer AG, Interval ET, Allen JL, Papenberg BW, Hames RA, Castaño JE, Schafer DA, Weed SA. Cortactin Phosphorylation by Casein Kinase 2 Regulates Actin-Related Protein 2/3 Complex Activity, Invadopodia Function, and Tumor Cell Invasion. Mol Cancer Res 2019; 17:987-1001. [PMID: 30610108 DOI: 10.1158/1541-7786.mcr-18-0391] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 09/18/2018] [Accepted: 12/12/2018] [Indexed: 12/13/2022]
Abstract
Malregulation of the actin cytoskeleton enhances tumor cell motility and invasion. The actin-binding protein cortactin facilitates branched actin network formation through activation of the actin-related protein (Arp) 2/3 complex. Increased cortactin expression due to gene amplification is observed in head and neck squamous cell carcinoma (HNSCC) and other cancers, corresponding with elevated tumor progression and poor patient outcome. Arp2/3 complex activation is responsible for driving increased migration and extracellular matrix (ECM) degradation by governing invadopodia formation and activity. Although cortactin-mediated activation of Arp2/3 complex and invadopodia regulation has been well established, signaling pathways responsible for governing cortactin binding to Arp2/3 are unknown and potentially present a new avenue for anti-invasive therapeutic targeting. Here we identify casein kinase (CK) 2α phosphorylation of cortactin as a negative regulator of Arp2/3 binding. CK2α directly phosphorylates cortactin at a conserved threonine (T24) adjacent to the canonical Arp2/3 binding motif. Phosphorylation of cortactin T24 by CK2α impairs the ability of cortactin to bind Arp2/3 and activate actin nucleation. Decreased invadopodia activity is observed in HNSCC cells with expression of CK2α phosphorylation-null cortactin mutants, shRNA-mediated CK2α knockdown, and with the CK2α inhibitor Silmitasertib. Silmitasertib inhibits HNSCC collective invasion in tumor spheroids and orthotopic tongue tumors in mice. Collectively these data suggest that CK2α-mediated cortactin phosphorylation at T24 is critical in regulating cortactin binding to Arp2/3 complex and pro-invasive activity, identifying a potential targetable mechanism for impairing HNSCC invasion. IMPLICATIONS: This study identifies a new signaling pathway that contributes to enhancing cancer cell invasion.Visual Overview: http://mcr.aacrjournals.org/content/molcanres/17/4/987/F1.large.jpg.
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Affiliation(s)
- Steven M Markwell
- Program in Cancer Cell Biology, Department of Biochemistry, West Virginia University, Morgantown, West Virginia
| | - Amanda G Ammer
- Program in Cancer Cell Biology, Department of Biochemistry, West Virginia University, Morgantown, West Virginia
| | - Erik T Interval
- Department of Otolaryngology, Head and Neck Surgery, West Virginia University, Morgantown, West Virginia
| | - Jessica L Allen
- Program in Cancer Cell Biology, Department of Biochemistry, West Virginia University, Morgantown, West Virginia
| | - Brenen W Papenberg
- Program in Cancer Cell Biology, Department of Biochemistry, West Virginia University, Morgantown, West Virginia
| | - River A Hames
- Program in Cancer Cell Biology, Department of Biochemistry, West Virginia University, Morgantown, West Virginia
| | - Johnathan E Castaño
- Department of Otolaryngology, Head and Neck Surgery, West Virginia University, Morgantown, West Virginia
| | - Dorothy A Schafer
- Department of Biology, University of Virginia, Charlottesville, Virginia
| | - Scott A Weed
- Program in Cancer Cell Biology, Department of Biochemistry, West Virginia University, Morgantown, West Virginia.
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12
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Higgs HN. A fruitful tree: developing the dendritic nucleation model of actin-based cell motility. Mol Biol Cell 2018. [PMCID: PMC6333179 DOI: 10.1091/mbc.e18-07-0426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
A fundamental question in cell biology concerns how cells move, and this has been the subject of intense research for decades. In the 1990s, a major leap forward was made in our understanding of cell motility, with the proposal of the dendritic nucleation model. This essay describes the events leading to the development of the model, including findings from many laboratories and scientific disciplines. The story is an excellent example of the scientific process in action, with the combination of multiple perspectives leading to robust conclusions.
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Affiliation(s)
- Henry N. Higgs
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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13
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Balzer CJ, Wagner AR, Helgeson LA, Nolen BJ. Dip1 Co-opts Features of Branching Nucleation to Create Linear Actin Filaments that Activate WASP-Bound Arp2/3 Complex. Curr Biol 2018; 28:3886-3891.e4. [PMID: 30471998 DOI: 10.1016/j.cub.2018.10.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 10/01/2018] [Accepted: 10/17/2018] [Indexed: 12/21/2022]
Abstract
When activated by Wiskott-Aldrich syndrome proteins (WASP), Arp2/3 complex nucleates branched actin filaments important for processes like cellular motility and endocytosis [1]. WASP-mediated activation of Arp2/3 complex requires a preformed actin filament, ensuring that activation by WASP creates branched instead of linear filaments. However, this biochemical requirement also means that assembly of branched actin networks must be primed with an initial seed filament [2-4]. We recently described a class of activators called WISH/DIP/SPIN90 (WDS) proteins, which, unlike WASP, activate Arp2/3 complex without a preformed filament [4]. Although this property may allow WDS proteins to serve as seed filament generators, it is unknown whether actin filaments nucleated by WDS-activated Arp2/3 complex can activate WASP-bound Arp2/3 complex. Further, despite their potential importance as branched actin network initiators, little is known about how WDS proteins turn on Arp2/3 complex. Here, we use two-color single-molecule total internal reflection fluorescence (TIRF) microscopy to show that Dip1, the S. pombe WDS protein [5], co-opts features of branching nucleation to activate Arp2/3 complex. Specifically, it activates Arp2/3 complex to nucleate linear filaments analogous to the branch created by WASP-mediated activation. The barbed ends of Dip1-Arp2/3 nucleated filaments are free to elongate, and their pointed ends remain anchored to Dip1-bound Arp2/3 complex. The linear filaments nucleated by Dip1-bound Arp2/3 complex activate WASP-bound Arp2/3 complex as potently as spontaneously nucleated or branched actin filaments. These observations provide important insights into the regulation of Arp2/3 complex by its activators and the molecular basis for initiation of branched actin networks.
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Affiliation(s)
- Connor J Balzer
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, 1229 University of Oregon, Eugene, OR 97403, USA
| | - Andrew R Wagner
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, 1229 University of Oregon, Eugene, OR 97403, USA
| | - Luke A Helgeson
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, 1229 University of Oregon, Eugene, OR 97403, USA
| | - Brad J Nolen
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, 1229 University of Oregon, Eugene, OR 97403, USA.
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14
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Luan Q, Liu SL, Helgeson LA, Nolen BJ. Structure of the nucleation-promoting factor SPIN90 bound to the actin filament nucleator Arp2/3 complex. EMBO J 2018; 37:embj.2018100005. [PMID: 30322896 DOI: 10.15252/embj.2018100005] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 08/31/2018] [Accepted: 09/06/2018] [Indexed: 11/09/2022] Open
Abstract
Unlike the WASP family of Arp2/3 complex activators, WISH/DIP/SPIN90 (WDS) family proteins activate actin filament nucleation by the Arp2/3 complex without the need for a preformed actin filament. This allows WDS proteins to initiate branched actin network assembly by providing seed filaments that activate WASP-bound Arp2/3 complex. Despite their important role in actin network initiation, it is unclear how WDS proteins drive the activating steps that require both WASP and pre-existing actin filaments during WASP-mediated nucleation. Here, we show that SPIN90 folds into an armadillo repeat domain that binds a surface of Arp2/3 complex distinct from the two WASP sites, straddling a hinge point that may stimulate movement of the Arp2 subunit into the activated short-pitch conformation. SPIN90 binds a surface on Arp2/3 complex that overlaps with actin filament binding, explaining how it could stimulate the same structural rearrangements in the complex as pre-existing actin filaments. By revealing how WDS proteins activate the Arp2/3 complex, these data provide a molecular foundation to understand initiation of dendritic actin networks and regulation of Arp2/3 complex by its activators.
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Affiliation(s)
- Qing Luan
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, USA
| | - Su-Ling Liu
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, USA
| | - Luke A Helgeson
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, USA
| | - Brad J Nolen
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, USA
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15
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Conformational changes in Arp2/3 complex induced by ATP, WASp-VCA, and actin filaments. Proc Natl Acad Sci U S A 2018; 115:E8642-E8651. [PMID: 30150414 DOI: 10.1073/pnas.1717594115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
We used fluorescence spectroscopy and EM to determine how binding of ATP, nucleation-promoting factors, actin monomers, and actin filaments changes the conformation of Arp2/3 complex during the process that nucleates an actin filament branch. We mutated subunits of Schizosaccharomyces pombe Arp2/3 complex for labeling with fluorescent dyes at either the C termini of Arp2 and Arp3 or ArpC1 and ArpC3. We measured Förster resonance energy transfer (FRET) efficiency (ETeff) between the dyes in the presence of the various ligands. We also computed class averages from electron micrographs of negatively stained specimens. ATP binding made small conformational changes of the nucleotide-binding cleft of the Arp2 subunit. WASp-VCA, WASp-CA, and WASp-actin-VCA changed the ETeff between the dyes on the Arp2 and Arp3 subunits much more than between dyes on ArpC1 and ArpC3. Ensemble FRET detected an additional structural change that brought ArpC1 and ArpC3 closer together when Arp2/3 complex bound actin filaments. VCA binding to Arp2/3 complex causes a conformational change that favors binding to the side of an actin filament, which allows further changes required to nucleate a daughter filament.
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16
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Abp1 promotes Arp2/3 complex-dependent actin nucleation and stabilizes branch junctions by antagonizing GMF. Nat Commun 2018; 9:2895. [PMID: 30042427 PMCID: PMC6057921 DOI: 10.1038/s41467-018-05260-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 06/22/2018] [Indexed: 12/26/2022] Open
Abstract
Formation and turnover of branched actin networks underlies cell migration and other essential force-driven processes. Type I nucleation-promoting factors (NPFs) such as WASP recruit actin monomers to Arp2/3 complex to stimulate nucleation. In contrast, mechanisms of type II NPFs such as Abp1 (also known as HIP55 and Drebrin-like protein) are less well understood. Here, we use single-molecule analysis to investigate yeast Abp1 effects on Arp2/3 complex, and find that Abp1 strongly enhances Arp2/3-dependent branch nucleation by stabilizing Arp2/3 on sides of mother filaments. Abp1 binds dynamically to filament sides, with sub-second lifetimes, yet associates stably with branch junctions. Further, we uncover a role for Abp1 in protecting filament junctions from GMF-induced debranching by competing with GMF for Arp2/3 binding. These data, combined with EM structures of Abp1 dimers bound to Arp2/3 complex in two different conformations, expand our mechanistic understanding of type II NPFs. Abp1, a type II actin nucleation promoting factor, is a known component of branched actin networks but its mechanism remains poorly understood. Here, the authors find that Abp1 enhances Arp2/3-mediated actin branch formation, and blocks ‘debranching’ by GMF, making it a pro-branching factor.
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17
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Identification of Wiskott-Aldrich syndrome protein (WASP) binding sites on the branched actin filament nucleator Arp2/3 complex. Proc Natl Acad Sci U S A 2018; 115:E1409-E1418. [PMID: 29386393 DOI: 10.1073/pnas.1716622115] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Arp2/3 complex nucleates branched actin filaments important for cellular motility and endocytosis. WASP family proteins are Arp2/3 complex activators that play multiple roles in branching nucleation, but little is known about the structural bases of these WASP functions, owing to an incomplete understanding of how WASP binds Arp2/3 complex. Recent data show WASP binds two sites, and biochemical and structural studies led to models in which the WASP C segment engages the barbed ends of the Arp3 and Arp2 subunits while the WASP A segment binds the back side of the complex on Arp3. However, electron microscopy reconstructions showed density for WASP inconsistent with these models on the opposite (front) side of Arp2/3 complex. Here we use chemical cross-linking and mass spectrometry (XL-MS) along with computational docking and structure-based mutational analysis to map the two WASP binding sites on the complex. Our data corroborate the barbed end and back side binding models and show one WASP binding site on Arp3, on the back side of the complex, and a second site on the bottom of the complex, spanning Arp2 and ARPC1. The XL-MS-identified cross-links rule out the front side binding model and show that the A segment of WASP binds along the bottom side of the ARPC1 subunit, instead of at the Arp2/ARPC1 interface, as suggested by FRET experiments. The identified binding sites support the Arp3 tail release model to explain WASP-mediated activating conformational changes in Arp2/3 complex and provide insight into the roles of WASP in branching nucleation.
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18
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Popinako A, Antonov M, Dibrova D, Chemeris A, Sokolova OS. Analysis of the interactions between GMF and Arp2/3 complex in two binding sites by molecular dynamics simulation. Biochem Biophys Res Commun 2018; 496:529-535. [PMID: 29339159 DOI: 10.1016/j.bbrc.2018.01.080] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 01/11/2018] [Indexed: 12/17/2022]
Abstract
The Arp2/3 complex plays a key role in nucleating actin filaments branching. The glia maturation factor (GMF) competes with activators for interacting with the Arp2/3 complex and initiates the debranching of actin filaments. In this study, we performed a comparative analysis of interactions between GMF and the Arp2/3 complex and identified new amino acid residues involved in GMF binding to the Arp2/3 complex at two separate sites, revealed by X-ray and single particle EM techniques. Using molecular dynamics simulations we demonstrated the quantitative and qualitative changes in hydrogen bonds upon binding with GMF. We identified the specific amino acid residues in GMF and Arp2/3 complex that stabilize the interactions and estimated the mean force profile for the GMF using umbrella sampling. Phylogenetic and structural analyses of the recently defined GMF binding site on the Arp3 subunit indicate a new mechanism for Arp2/3 complex inactivation that involves interactions between the Arp2/3 complex and GMF at two binding sites.
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Affiliation(s)
- A Popinako
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of RAS, 33 Leninsky Ave, bld. 2, Moscow, 119071, Russia
| | - M Antonov
- M.K. Ammosov North-Eastern Federal University, 58 Belinskiy str, suite 312, Yakutsk, 677980, Republic of Sakha (Yakutia), Russia
| | - D Dibrova
- Lomonosov Moscow State University, Faculty of Biology, 1 Leninskie gory, bld 12, Moscow, 119234, Russia
| | - A Chemeris
- Lomonosov Moscow State University, Faculty of Biology, 1 Leninskie gory, bld 12, Moscow, 119234, Russia
| | - O S Sokolova
- Lomonosov Moscow State University, Faculty of Biology, 1 Leninskie gory, bld 12, Moscow, 119234, Russia.
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19
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Fabre L, Santelli E, Mountassif D, Donoghue A, Biswas A, Blunck R, Hanein D, Volkmann N, Liddington R, Rouiller I. Structure of anthrax lethal toxin prepore complex suggests a pathway for efficient cell entry. J Gen Physiol 2017; 148:313-24. [PMID: 27670897 PMCID: PMC5037343 DOI: 10.1085/jgp.201611617] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/25/2016] [Indexed: 01/20/2023] Open
Abstract
Anthrax toxin comprises three soluble proteins: protective antigen (PA), lethal factor (LF), and edema factor (EF). PA must be cleaved by host proteases before it oligomerizes and forms a prepore, to which LF and EF bind. After endocytosis of this tripartite complex, the prepore transforms into a narrow transmembrane pore that delivers unfolded LF and EF into the host cytosol. Here, we find that translocation of multiple 90-kD LF molecules is rapid and efficient. To probe the molecular basis of this translocation, we calculated a three-dimensional map of the fully loaded (PA63)7-(LF)3 prepore complex by cryo-electron microscopy (cryo-EM). The map shows three LFs bound in a similar way to one another, via their N-terminal domains, to the surface of the PA heptamer. The model also reveals contacts between the N- and C-terminal domains of adjacent LF molecules. We propose that this molecular arrangement plays an important role in the maintenance of translocation efficiency through the narrow PA pore.
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Affiliation(s)
- Lucien Fabre
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
| | - Eugenio Santelli
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Driss Mountassif
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
| | - Annemarie Donoghue
- Departments of Physics, Université de Montréal, Montréal, Québec H3T 1J4, Canada Department of Physiology, Université de Montréal, Montréal, Québec H3T 1J4, Canada Groupe d'Étude des Protéines Membranaires (GÉPROM), Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Aviroop Biswas
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
| | - Rikard Blunck
- Departments of Physics, Université de Montréal, Montréal, Québec H3T 1J4, Canada Department of Physiology, Université de Montréal, Montréal, Québec H3T 1J4, Canada Groupe d'Étude des Protéines Membranaires (GÉPROM), Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Robert Liddington
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Isabelle Rouiller
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
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20
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Bertier L, Boucherie C, Zwaenepoel O, Vanloo B, Van Troys M, Van Audenhove I, Gettemans J. Inhibitory cortactin nanobodies delineate the role of NTA- and SH3-domain-specific functions during invadopodium formation and cancer cell invasion. FASEB J 2017; 31:2460-2476. [PMID: 28235780 DOI: 10.1096/fj.201600810rr] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 02/07/2017] [Indexed: 01/08/2023]
Abstract
Cancer cells exploit different strategies to escape from the primary tumor, gain access to the circulation, disseminate throughout the body, and form metastases, the leading cause of death by cancer. Invadopodia, proteolytically active plasma membrane extensions, are essential in this escape mechanism. Cortactin is involved in every phase of invadopodia formation, and its overexpression is associated with increased invadopodia formation, extracellular matrix degradation, and cancer cell invasion. To analyze endogenous cortactin domain function in these processes, we characterized the effects of nanobodies that are specific for the N-terminal acidic domain of cortactin and expected to target small epitopes within this domain. These nanobodies inhibit cortactin-mediated actin-related protein (Arp)2/3 activation, and, after their intracellular expression in cancer cells, decrease invadopodia formation, extracellular matrix degradation, and cancer cell invasion. In addition, one of the nanobodies affects Arp2/3 interaction and invadopodium stability, and a nanobody targeting the Src homology 3 domain of cortactin enabled comparison of 2 functional regions in invadopodium formation or stability. Given their common and distinct effects, we validate cortactin nanobodies as an instrument to selectively block and study distinct domains within a protein with unprecedented precision, aiding rational future generation of protein domain-selective therapeutic compounds.-Bertier, L., Boucherie, C., Zwaenepoel, O., Vanloo, B., Van Troys, M., Van Audenhove, I., Gettemans, J. Inhibitory cortactin nanobodies delineate the role of NTA- and SH3-domain-specific functions during invadopodium formation and cancer cell invasion.
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Affiliation(s)
- Laurence Bertier
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
| | - Ciska Boucherie
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
| | - Olivier Zwaenepoel
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
| | - Berlinda Vanloo
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
| | - Marleen Van Troys
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
| | - Isabel Van Audenhove
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
| | - Jan Gettemans
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University-Campus Rommelaere, Ghent, Belgium
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21
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Xu XP, Kim E, Swift M, Smith JW, Volkmann N, Hanein D. Three-Dimensional Structures of Full-Length, Membrane-Embedded Human α(IIb)β(3) Integrin Complexes. Biophys J 2016; 110:798-809. [PMID: 26910421 DOI: 10.1016/j.bpj.2016.01.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 12/08/2015] [Accepted: 01/13/2016] [Indexed: 10/22/2022] Open
Abstract
Integrins are bidirectional, allosteric transmembrane receptors that play a central role in hemostasis and arterial thrombosis. Using cryo-electron microscopy, multireference single-particle reconstruction methods, and statistics-based computational fitting approaches, we determined three-dimensional structures of human integrin αIIbβ3 embedded in a lipid bilayer (nanodiscs) while bound to domains of the cytosolic regulator talin and to extracellular ligands. We also determined the conformations of integrin in solution by itself to localize the membrane and the talin-binding site. To our knowledge, our data provide unprecedented three-dimensional information about the conformational states of intact, full-length integrin within membrane bilayers under near-physiological conditions and in the presence of cytosolic activators and extracellular ligands. We show that αIIbβ3 integrins exist in a conformational equilibrium clustered around four main states. These conformations range from a compact bent nodule to two partially extended intermediate conformers and finally to a fully upright state. In the presence of nanodiscs and the two ligands, the equilibrium is significantly shifted toward the upright conformation. In this conformation, the receptor extends ∼20 nm upward from the membrane. There are no observable contacts between the two subunits other than those in the headpiece near the ligand-binding pocket, and the α- and β-subunits are well separated with their cytoplasmic tails ∼8 nm apart. Our results indicate that extension of the ectodomain is possible without separating the legs or extending the hybrid domain, and that the ligand-binding pocket is not occluded by the membrane in any conformations of the equilibrium. Further, they suggest that integrin activation may be influenced by equilibrium shifts.
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Affiliation(s)
- Xiao-Ping Xu
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Eldar Kim
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Mark Swift
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Jeffrey W Smith
- Infectious Disease Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
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22
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Sokolova OS, Chemeris A, Guo S, Alioto SL, Gandhi M, Padrick S, Pechnikova E, David V, Gautreau A, Goode BL. Structural Basis of Arp2/3 Complex Inhibition by GMF, Coronin, and Arpin. J Mol Biol 2016; 429:237-248. [PMID: 27939292 DOI: 10.1016/j.jmb.2016.11.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 11/23/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022]
Abstract
The evolutionarily conserved Arp2/3 complex plays a central role in nucleating the branched actin filament arrays that drive cell migration, endocytosis, and other processes. To better understand Arp2/3 complex regulation, we used single-particle electron microscopy to compare the structures of Arp2/3 complex bound to three different inhibitory ligands: glia maturation factor (GMF), Coronin, and Arpin. Although the three inhibitors have distinct binding sites on Arp2/3 complex, they each induced an "open" nucleation-inactive conformation. Coronin promoted a standard (previously described) open conformation of Arp2/3 complex, with the N-terminal β-propeller domain of Coronin positioned near the p35/ARPC2 subunit of Arp2/3 complex. GMF induced two distinct open conformations of Arp2/3 complex, which correlated with the two suggested binding sites for GMF. Furthermore, GMF synergized with Coronin in inhibiting actin nucleation by Arp2/3 complex. Arpin, which uses VCA-related acidic (A) motifs to interact with the Arp2/3 complex, induced the standard open conformation, and two new masses appeared at positions near Arp2 and Arp3. Furthermore, Arpin showed additive inhibitory effects on Arp2/3 complex with Coronin and GMF. Together, these data suggest that Arp2/3 complex conformation is highly polymorphic and that its activities can be controlled combinatorially by different inhibitory ligands.
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Affiliation(s)
- Olga S Sokolova
- Department of Biology, Moscow M.V. Lomonosov University, Moscow 119234, Russia
| | - Angelina Chemeris
- Department of Biology, Moscow M.V. Lomonosov University, Moscow 119234, Russia; Ecole Polytechnique, CNRS UMR7654, Palaiseau 91120, France
| | - Siyang Guo
- Department of Biology, Brandeis University, Waltham, MA 02453, USA
| | | | - Meghal Gandhi
- Department of Biology, Brandeis University, Waltham, MA 02453, USA
| | - Shae Padrick
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | | | - Violaine David
- Ecole Polytechnique, CNRS UMR7654, Palaiseau 91120, France
| | | | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, MA 02453, USA.
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23
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Rodnick-Smith M, Liu SL, Balzer CJ, Luan Q, Nolen BJ. Identification of an ATP-controlled allosteric switch that controls actin filament nucleation by Arp2/3 complex. Nat Commun 2016; 7:12226. [PMID: 27417392 PMCID: PMC4947185 DOI: 10.1038/ncomms12226] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 06/10/2016] [Indexed: 01/07/2023] Open
Abstract
Nucleation of branched actin filaments by Arp2/3 complex is tightly regulated to control actin assembly in cells. Arp2/3 complex activation involves conformational changes brought about by ATP, Nucleation Promoting Factor (NPF) proteins, actin filaments and NPF-recruited actin monomers. To understand how these factors promote activation, we must first understand how the complex is held inactive in their absence. Here we demonstrate that the Arp3 C-terminal tail is a structural switch that prevents Arp2/3 complex from adopting an active conformation. The interaction between the tail and a hydrophobic groove in Arp3 blocks movement of Arp2 and Arp3 into an activated filament-like (short pitch) conformation. Our data indicate ATP binding destabilizes this interaction via an allosteric link between the Arp3 nucleotide cleft and the hydrophobic groove, thereby promoting the short-pitch conformation. Our results help explain how Arp2/3 complex is locked in an inactive state without activators and how autoinhibition is relieved.
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Affiliation(s)
- Max Rodnick-Smith
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
| | - Su-Ling Liu
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA
| | - Connor J Balzer
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
| | - Qing Luan
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA
| | - Brad J Nolen
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
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24
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Role and structural mechanism of WASP-triggered conformational changes in branched actin filament nucleation by Arp2/3 complex. Proc Natl Acad Sci U S A 2016; 113:E3834-43. [PMID: 27325766 DOI: 10.1073/pnas.1517798113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The Arp2/3 (Actin-related proteins 2/3) complex is activated by WASP (Wiskott-Aldrich syndrome protein) family proteins to nucleate branched actin filaments that are important for cellular motility. WASP recruits actin monomers to the complex and stimulates movement of Arp2 and Arp3 into a "short-pitch" conformation that mimics the arrangement of actin subunits within filaments. The relative contribution of these functions in Arp2/3 complex activation and the mechanism by which WASP stimulates the conformational change have been unknown. We purified budding yeast Arp2/3 complex held in or near the short-pitch conformation by an engineered covalent cross-link to determine if the WASP-induced conformational change is sufficient for activity. Remarkably, cross-linked Arp2/3 complex bypasses the need for WASP in activation and is more active than WASP-activated Arp2/3 complex. These data indicate that stimulation of the short-pitch conformation is the critical activating function of WASP and that monomer delivery is not a fundamental requirement for nucleation but is a specific requirement for WASP-mediated activation. During activation, WASP limits nucleation rates by releasing slowly from nascent branches. The cross-linked complex is inhibited by WASP's CA region, even though CA potently stimulates cross-linking, suggesting that slow WASP detachment masks the activating potential of the short-pitch conformational switch. We use structure-based mutations and WASP-Arp fusion chimeras to determine how WASP stimulates movement toward the short-pitch conformation. Our data indicate that WASP displaces the autoinhibitory Arp3 C-terminal tail from a hydrophobic groove at Arp3's barbed end to destabilize the inactive state, providing a mechanism by which WASP stimulates the short-pitch conformation and activates Arp2/3 complex.
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25
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Abella JVG, Galloni C, Pernier J, Barry DJ, Kjær S, Carlier MF, Way M. Isoform diversity in the Arp2/3 complex determines actin filament dynamics. Nat Cell Biol 2015; 18:76-86. [PMID: 26655834 DOI: 10.1038/ncb3286] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 11/09/2015] [Indexed: 12/16/2022]
Abstract
The Arp2/3 complex consists of seven evolutionarily conserved subunits (Arp2, Arp3 and ARPC1-5) and plays an essential role in generating branched actin filament networks during many different cellular processes. In mammals, however, the ARPC1 and ARPC5 subunits are each encoded by two isoforms that are 67% identical. This raises the possibility that Arp2/3 complexes with different properties may exist. We found that Arp2/3 complexes containing ARPC1B and ARPC5L are significantly better at promoting actin assembly than those with ARPC1A and ARPC5, both in cells and in vitro. Branched actin networks induced by complexes containing ARPC1B or ARPC5L are also disassembled ∼2-fold slower than those formed by their counterparts. This difference reflects the ability of cortactin to stabilize ARPC1B- and ARPC5L- but not ARPC1A- and ARPC5-containing complexes against coronin-mediated disassembly. Our observations demonstrate that the Arp2/3 complex in higher eukaryotes is actually a family of complexes with different properties.
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Affiliation(s)
- Jasmine V G Abella
- Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London, WC2A 3LY, UK
| | - Chiara Galloni
- Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London, WC2A 3LY, UK
| | - Julien Pernier
- Laboratoire d'Enzymologie et Biochimie Structurale, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - David J Barry
- Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London, WC2A 3LY, UK
| | - Svend Kjær
- The Structural Biology Science Technology Platform, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London, WC2A 3LY, UK
| | - Marie-France Carlier
- Laboratoire d'Enzymologie et Biochimie Structurale, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Michael Way
- Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London, WC2A 3LY, UK
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26
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Krutetskaya ZI, Milenina LS, Naumova AA, Butov SN, Antonov VG, Nozdrachev AD. Involvement of the Arp2/3 complex and WASP proteins in the effect of glutoxim and molixan on intracellular Ca(2+) concentration in macrophages. DOKL BIOCHEM BIOPHYS 2015; 464:279-82. [PMID: 26518547 DOI: 10.1134/s1607672955050013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Indexed: 11/23/2022]
Abstract
The Fura-2AM fluorescent Ca(2+) probe was used to study the possibility that the Arp2/3 complex and WASP proteins are involved in the effects of glutoxim and molixan on the intracellular Ca(2+) concentration in macrophages. It has been demonstrated that preincubation of macrophages with inhibitors of the Arp2/3 complex or WASP proteins (CK-0944666 or wiskostatin, respectively) results in a significant suppression of Ca(2+)-responses induced by glutoxim or molixan. This suggests that polymerization of actin filaments is a process involved in the effect of glutoxim or molixan on intracellular Ca(2+) concentration in macrophages.
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Affiliation(s)
- Z I Krutetskaya
- St. Petersburg State University, St. Petersburg, 199034, Russia.
| | - L S Milenina
- St. Petersburg State University, St. Petersburg, 199034, Russia
| | - A A Naumova
- St. Petersburg State University, St. Petersburg, 199034, Russia
| | - S N Butov
- St. Petersburg State University, St. Petersburg, 199034, Russia
| | - V G Antonov
- St. Petersburg State University, St. Petersburg, 199034, Russia
| | - A D Nozdrachev
- St. Petersburg State University, St. Petersburg, 199034, Russia
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27
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Structural analysis of the transitional state of Arp2/3 complex activation by two actin-bound WCAs. Nat Commun 2015; 5:3308. [PMID: 24518936 DOI: 10.1038/ncomms4308] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 01/22/2014] [Indexed: 11/08/2022] Open
Abstract
Actin filament nucleation and branching by Arp2/3 complex is activated by nucleation-promoting factors (NPFs), whose C-terminal WCA region contains binding sites for actin (W) and Arp2/3 complex (CA). It is debated whether one or two NPFs are required for activation. Here we present evidence in support of the two-NPF model and show that actin plays a crucial role in the interactions of two mammalian NPFs, N-WASP and WAVE2, with Arp2/3 complex. Competition between actin-WCA and glia maturation factor (GMF) for binding to Arp2/3 complex suggests that during activation the first actin monomer binds at the barbed end of Arp2. Based on distance constraints obtained by time-resolved fluorescence resonance energy transfer, we define the relative position of the two actin-WCAs on Arp2/3 complex and propose an atomic model of the 11-subunit transitional complex.
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28
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McCabe Pryor M, Steinkamp MP, Halasz AM, Chen Y, Yang S, Smith MS, Zahoransky-Kohalmi G, Swift M, Xu XP, Hanein D, Volkmann N, Lidke DS, Edwards JS, Wilson BS. Orchestration of ErbB3 signaling through heterointeractions and homointeractions. Mol Biol Cell 2015; 26:4109-23. [PMID: 26378253 PMCID: PMC4710241 DOI: 10.1091/mbc.e14-06-1114] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 09/09/2015] [Indexed: 12/27/2022] Open
Abstract
Members of the ErbB family of receptor tyrosine kinases are capable of both homointeractions and heterointeractions. Because each receptor has a unique set of binding sites for downstream signaling partners and differential catalytic activity, subtle shifts in their combinatorial interplay may have a large effect on signaling outcomes. The overexpression and mutation of ErbB family members are common in numerous human cancers and shift the balance of activation within the signaling network. Here we report the development of a spatial stochastic model that addresses the dynamics of ErbB3 homodimerization and heterodimerization with ErbB2. The model is based on experimental measures for diffusion, dimer off-rates, kinase activity, and dephosphorylation. We also report computational analysis of ErbB3 mutations, generating the prediction that activating mutations in the intracellular and extracellular domains may be subdivided into classes with distinct underlying mechanisms. We show experimental evidence for an ErbB3 gain-of-function point mutation located in the C-lobe asymmetric dimerization interface, which shows enhanced phosphorylation at low ligand dose associated with increased kinase activity.
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Affiliation(s)
- Meghan McCabe Pryor
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM 87131 Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545
| | - Mara P Steinkamp
- Department of Pathology, University of New Mexico, Albuquerque, NM 87131 Cancer Center, University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, NM 87131
| | - Adam M Halasz
- Department of Mathematics, West Virginia University, Morgantown, WV 25606
| | - Ye Chen
- Department of Mathematics, West Virginia University, Morgantown, WV 25606
| | - Shujie Yang
- Department of OB/GYN, University of Iowa Carver College of Medicine, Iowa City, IA 52242
| | | | | | - Mark Swift
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Xiao-Ping Xu
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Dorit Hanein
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Niels Volkmann
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Diane S Lidke
- Department of Pathology, University of New Mexico, Albuquerque, NM 87131 Cancer Center, University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, NM 87131
| | - Jeremy S Edwards
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM 87131 Cancer Center, University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, NM 87131 Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM 87131
| | - Bridget S Wilson
- Department of Pathology, University of New Mexico, Albuquerque, NM 87131 Cancer Center, University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, NM 87131
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29
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Jurgenson CT, Pollard TD. Crystals of the Arp2/3 complex in two new space groups with structural information about actin-related protein 2 and potential WASP binding sites. Acta Crystallogr F Struct Biol Commun 2015; 71:1161-8. [PMID: 26323303 PMCID: PMC4555924 DOI: 10.1107/s2053230x15013515] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/14/2015] [Indexed: 02/06/2023] Open
Abstract
Co-crystals of the bovine Arp2/3 complex with the CA motif from N-WASP in two new space groups were analyzed by X-ray diffraction. The crystals in the orthorhombic space group P212121 contained one complex per asymmetric unit, with unit-cell parameters a = 105.48, b = 156.71, c = 177.84 Å, and diffracted to 3.9 Å resolution. The crystals in the tetragonal space group P41 contained two complexes per asymmetric unit, with unit-cell parameters a = b = 149.93, c = 265.91 Å, and diffracted to 5.0 Å resolution. The electron-density maps of both new crystal forms had densities for small segments of subdomains 1 and 2 of Arp2. Both maps had density at the binding site on Arp3 for the C-terminal EWE tripeptide from N-WASP and a binding site proposed for the C motif of N-WASP in the barbed-end groove of Arp2. The map from the tetragonal crystal form had density near the barbed end of Arp3 that may correspond to the C helix of N-WASP. The noise levels and the low resolution of the maps made the assignment of specific molecular structures for any of these CA peptides impossible.
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Affiliation(s)
- Christopher T. Jurgenson
- Department of Chemistry and Physics, Delta State University, 1003 West Sunflower Road, Cleveland, MS 38733, USA
| | - Thomas D. Pollard
- Departments of Molecular, Cellular and Developmental Biology and Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
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30
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Xu XP, Volkmann N. Validation methods for low-resolution fitting of atomic structures to electron microscopy data. Arch Biochem Biophys 2015; 581:49-53. [PMID: 26116787 DOI: 10.1016/j.abb.2015.06.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 06/12/2015] [Accepted: 06/23/2015] [Indexed: 12/19/2022]
Abstract
Fitting of atomic-resolution structures into reconstructions from electron cryo-microscopy is routinely used to understand the structure and function of macromolecular machines. Despite the fact that a plethora of fitting methods has been developed over recent years, standard protocols for quality assessment and validation of these fits have not been established. Here, we present the general concepts underlying current validation ideas as they relate to fitting of atomic-resolution models into electron cryo-microscopy reconstructions, with an emphasis on reconstructions with resolutions below the sub-nanometer range.
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Affiliation(s)
- Xiao-Ping Xu
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, 10901 N Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, 10901 N Torrey Pines Rd, La Jolla, CA 92037, USA.
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31
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Control of polarized assembly of actin filaments in cell motility. Cell Mol Life Sci 2015; 72:3051-67. [PMID: 25948416 PMCID: PMC4506460 DOI: 10.1007/s00018-015-1914-2] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 04/02/2015] [Accepted: 04/23/2015] [Indexed: 10/25/2022]
Abstract
Actin cytoskeleton remodeling, which drives changes in cell shape and motility, is orchestrated by a coordinated control of polarized assembly of actin filaments. Signal responsive, membrane-bound protein machineries initiate and regulate polarized growth of actin filaments by mediating transient links with their barbed ends, which elongate from polymerizable actin monomers. The barbed end of an actin filament thus stands out as a hotspot of regulation of filament assembly. It is the target of both soluble and membrane-bound agonists as well as antagonists of filament assembly. Here, we review the molecular mechanisms by which various regulators of actin dynamics bind, synergize or compete at filament barbed ends. Two proteins can compete for the barbed end via a mutually exclusive binding scheme. Alternatively, two regulators acting individually at barbed ends may be bound together transiently to terminal actin subunits at barbed ends, leading to the displacement of one by the other. The kinetics of these reactions is a key in understanding how filament length and membrane-filament linkage are controlled. It is also essential for understanding how force is produced to shape membranes by mechano-sensitive, processive barbed end tracking machineries like formins and by WASP-Arp2/3 branched filament arrays. A combination of biochemical and biophysical approaches, including bulk solution assembly measurements using pyrenyl-actin fluorescence, single filament dynamics, single molecule fluorescence imaging and reconstituted self-organized filament assemblies, have provided mechanistic insight into the role of actin polymerization in motile processes.
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32
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Sweeney MO, Collins A, Padrick SB, Goode BL. A novel role for WAVE1 in controlling actin network growth rate and architecture. Mol Biol Cell 2014; 26:495-505. [PMID: 25473116 PMCID: PMC4310740 DOI: 10.1091/mbc.e14-10-1477] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
A novel functional role for WAVE1 is found that is lacking in N-WASP and WAVE2. Through its unique WH2 domain, WAVE1 dramatically reduces the rate of actin filament elongation independently of its interactions with the Arp2/3 complex. These findings help explain how cells build actin networks with distinct geometries and growth rates. Branched actin filament networks in cells are assembled through the combined activities of Arp2/3 complex and different WASP/WAVE proteins. Here we used TIRF and electron microscopy to directly compare for the first time the assembly kinetics and architectures of actin filament networks produced by Arp2/3 complex and dimerized VCA regions of WAVE1, WAVE2, or N-WASP. WAVE1 produced strikingly different networks from WAVE2 or N-WASP, which comprised unexpectedly short filaments. Further analysis showed that the WAVE1-specific activity stemmed from an inhibitory effect on filament elongation both in the presence and absence of Arp2/3 complex, which was observed even at low stoichiometries of WAVE1 to actin monomers, precluding an effect from monomer sequestration. Using a series of VCA chimeras, we mapped the elongation inhibitory effects of WAVE1 to its WH2 (“V”) domain. Further, mutating a single conserved lysine residue potently disrupted WAVE1's inhibitory effects. Taken together, our results show that WAVE1 has unique activities independent of Arp2/3 complex that can govern both the growth rates and architectures of actin filament networks. Such activities may underlie previously observed differences between the cellular functions of WAVE1 and WAVE2.
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Affiliation(s)
- Meredith O Sweeney
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454
| | - Agnieszka Collins
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454
| | - Shae B Padrick
- Howard Hughes Medical Institute and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Bruce L Goode
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454;
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33
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Pauker MH, Reicher B, Joseph N, Wortzel I, Jakubowicz S, Noy E, Perl O, Barda-Saad M. WASp family verprolin-homologous protein-2 (WAVE2) and Wiskott-Aldrich syndrome protein (WASp) engage in distinct downstream signaling interactions at the T cell antigen receptor site. J Biol Chem 2014; 289:34503-19. [PMID: 25342748 DOI: 10.1074/jbc.m114.591685] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
T cell antigen receptor (TCR) engagement has been shown to activate pathways leading to actin cytoskeletal polymerization and reorganization, which are essential for lymphocyte activation and function. Several actin regulatory proteins were implicated in regulating the actin machinery, such as members of the Wiskott-Aldrich syndrome protein (WASp) family. These include WASp and the WASp family verprolin-homologous protein-2 (WAVE2). Although WASp and WAVE2 share several structural features, the precise regulatory mechanisms and potential redundancy between them have not been fully characterized. Specifically, unlike WASp, the dynamic molecular interactions that regulate WAVE2 recruitment to the cell membrane and specifically to the TCR signaling complex are largely unknown. Here, we identify the molecular mechanism that controls the recruitment of WAVE2 in comparison with WASp. Using fluorescence resonance energy transfer (FRET) and novel triple-color FRET (3FRET) technology, we demonstrate how WAVE2 signaling complexes are dynamically regulated during lymphocyte activation in vivo. We show that, similar to WASp, WAVE2 recruitment to the TCR site depends on protein-tyrosine kinase, ZAP-70, and the adaptors LAT, SLP-76, and Nck. However, in contrast to WASp, WAVE2 leaves this signaling complex and migrates peripherally together with vinculin to the membrane leading edge. Our experiments demonstrate that WASp and WAVE2 differ in their dynamics and their associated proteins. Thus, this study reveals the differential mechanisms regulating the function of these cytoskeletal proteins.
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Affiliation(s)
- Maor H Pauker
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Barak Reicher
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Noah Joseph
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Inbal Wortzel
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Shlomi Jakubowicz
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Elad Noy
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Orly Perl
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Mira Barda-Saad
- From the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
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34
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Volkmann N, Martásek P, Roman LJ, Xu XP, Page C, Swift M, Hanein D, Masters BS. Holoenzyme structures of endothelial nitric oxide synthase - an allosteric role for calmodulin in pivoting the FMN domain for electron transfer. J Struct Biol 2014; 188:46-54. [PMID: 25175399 DOI: 10.1016/j.jsb.2014.08.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 08/18/2014] [Indexed: 01/26/2023]
Abstract
While the three-dimensional structures of heme- and flavin-binding domains of the NOS isoforms have been determined, the structures of the holoenzymes remained elusive. Application of electron cryo-microscopy and structural modeling of the bovine endothelial nitric oxide synthase (eNOS) holoenzyme produced detailed models of the intact holoenzyme in the presence and absence of Ca(2+)/calmodulin (CaM). These models accommodate the cross-electron transfer from the reductase in one monomer to the heme in the opposite monomer. The heme domain acts as the anchoring dimeric structure for the entire enzyme molecule, while the FMN domain is activated by CaM to move flexibly to bridge the distance between the reductase and oxygenase domains. Our results indicate that the key regulatory role of CaM involves the stabilization of structural intermediates and precise positioning of the pivot for the FMN domain tethered shuttling motion to accommodate efficient and rapid electron transfer in the homodimer of eNOS.
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Affiliation(s)
- Niels Volkmann
- Bioinformatics and Systems Biology Program, Sanford Burnham Medical Research Institute, La Jolla, CA 92075, USA.
| | - Pavel Martásek
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; Department of Pediatrics, First School of Medicine, Charles University, 12109 Prague, Czech Republic
| | - Linda J Roman
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Xiao-Ping Xu
- Bioinformatics and Systems Biology Program, Sanford Burnham Medical Research Institute, La Jolla, CA 92075, USA
| | - Christopher Page
- Bioinformatics and Systems Biology Program, Sanford Burnham Medical Research Institute, La Jolla, CA 92075, USA
| | - Mark Swift
- Bioinformatics and Systems Biology Program, Sanford Burnham Medical Research Institute, La Jolla, CA 92075, USA
| | - Dorit Hanein
- Bioinformatics and Systems Biology Program, Sanford Burnham Medical Research Institute, La Jolla, CA 92075, USA.
| | - Bettie Sue Masters
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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35
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Helgeson LA, Prendergast JG, Wagner AR, Rodnick-Smith M, Nolen BJ. Interactions with actin monomers, actin filaments, and Arp2/3 complex define the roles of WASP family proteins and cortactin in coordinately regulating branched actin networks. J Biol Chem 2014; 289:28856-69. [PMID: 25160634 DOI: 10.1074/jbc.m114.587527] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arp2/3 complex is an important actin filament nucleator that creates branched actin filament networks required for formation of lamellipodia and endocytic actin structures. Cellular assembly of branched actin networks frequently requires multiple Arp2/3 complex activators, called nucleation promoting factors (NPFs). We recently presented a mechanism by which cortactin, a weak NPF, can displace a more potent NPF, N-WASP, from nascent branch junctions to synergistically accelerate nucleation. The distinct roles of these NPFs in branching nucleation are surprising given their similarities. We biochemically dissected these two classes of NPFs to determine how their Arp2/3 complex and actin interacting segments modulate their influences on branched actin networks. We find that the Arp2/3 complex-interacting N-terminal acidic sequence (NtA) of cortactin has structural features distinct from WASP acidic regions (A) that are required for synergy between the two NPFs. Our mutational analysis shows that differences between NtA and A do not explain the weak intrinsic NPF activity of cortactin, but instead that cortactin is a weak NPF because it cannot recruit actin monomers to Arp2/3 complex. We use TIRF microscopy to show that cortactin bundles branched actin filaments using actin filament binding repeats within a single cortactin molecule, but that N-WASP antagonizes cortactin-mediated bundling. Finally, we demonstrate that multiple WASP family proteins synergistically activate Arp2/3 complex and determine the biochemical requirements in WASP proteins for synergy. Our data indicate that synergy between WASP proteins and cortactin may play a general role in assembling diverse actin-based structures, including lamellipodia, podosomes, and endocytic actin networks.
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Affiliation(s)
- Luke A Helgeson
- From the Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1229
| | - Julianna G Prendergast
- From the Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1229
| | - Andrew R Wagner
- From the Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1229
| | - Max Rodnick-Smith
- From the Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1229
| | - Brad J Nolen
- From the Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1229
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36
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Han SP, Gambin Y, Gomez GA, Verma S, Giles N, Michael M, Wu SK, Guo Z, Johnston W, Sierecki E, Parton RG, Alexandrov K, Yap AS. Cortactin scaffolds Arp2/3 and WAVE2 at the epithelial zonula adherens. J Biol Chem 2014; 289:7764-75. [PMID: 24469447 DOI: 10.1074/jbc.m113.544478] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Cadherin junctions arise from the integrated action of cell adhesion, signaling, and the cytoskeleton. At the zonula adherens (ZA), a WAVE2-Arp2/3 actin nucleation apparatus is necessary for junctional tension and integrity. But how this is coordinated with cadherin adhesion is not known. We now identify cortactin as a key scaffold for actin regulation at the ZA, which localizes to the ZA through influences from both E-cadherin and N-WASP. Using cell-free protein expression and fluorescent single molecule coincidence assays, we demonstrate that cortactin binds directly to the cadherin cytoplasmic tail. However, its concentration with cadherin at the apical ZA also requires N-WASP. Cortactin is known to bind Arp2/3 directly (Weed, S. A., Karginov, A. V., Schafer, D. A., Weaver, A. M., Kinley, A. W., Cooper, J. A., and Parsons, J. T. (2000) J. Cell Biol. 151, 29-40). We further show that cortactin can directly bind WAVE2, as well as Arp2/3, and both these interactions are necessary for actin assembly at the ZA. We propose that cortactin serves as a platform that integrates regulators of junctional actin assembly at the ZA.
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Affiliation(s)
- Siew Ping Han
- From the Division of Molecular Cell Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia
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37
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Three-dimensional reconstructions of actin filaments capped by Arp2/3 complex. Eur J Cell Biol 2014; 93:179-83. [PMID: 24552843 DOI: 10.1016/j.ejcb.2014.01.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/01/2014] [Accepted: 01/09/2014] [Indexed: 11/20/2022] Open
Abstract
The primary function of Arp2/3 complex is the generation of free barbed ends by nucleating new filaments from the sides of pre-existing filaments. The pathway of branch formation is complex and involves nucleation promoting factors, actin monomers and nucleotides. A less prominent function of Arp2/3 complex is capping of actin filament pointed ends. Here we show, using electron microscopy, electron tomography, and image reconstruction of negatively-stained samples at ∼2-3nm resolution, that Arp2/3 complex bound to the pointed ends of actin filaments has a conformation similar to that in the branch junction with the Arps arranged in an actin-filament like configuration. This is direct evidence for the existence of two distinct activation pathways for Arp2/3 complex, one in the context of branch formation, one in the context of pointed-end capping, with essentially the same conformational end point.
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38
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Volkmann N. The joys and perils of flexible fitting. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 805:137-55. [PMID: 24446360 DOI: 10.1007/978-3-319-02970-2_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
While performing their functions, biological macromolecules often form large, dynamically changing macromolecular assemblies. Only a relatively small number of such assemblies have been accessible to the atomic-resolution techniques X-ray crystallography and NMR. Electron microscopy in conjunction with image reconstruction has become the preferred alternative for revealing the structures of such macromolecular complexes. However, for most assemblies the achievable resolution is too low to allow accurate atomic modeling directly from the data. Yet, useful models often can be obtained by fitting atomic models of individual components into a low-resolution reconstruction of the entire assembly. Several algorithms for achieving optimal fits in this context were developed recently, many allowing considerable degrees of flexibility to account for binding-induced conformational changes of the assembly components. This chapter describes the advantages and potential pitfalls of these methods and puts them into perspective with alternative approaches such as iterative modular fitting of rigid-body domains.
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Affiliation(s)
- Niels Volkmann
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, 10901 N Torrey Pines Rd, La Jolla, CA, 92037, USA,
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Zahm JA, Padrick SB, Chen Z, Pak CW, Yunus AA, Henry L, Tomchick DR, Chen Z, Rosen MK. The bacterial effector VopL organizes actin into filament-like structures. Cell 2013; 155:423-34. [PMID: 24120140 DOI: 10.1016/j.cell.2013.09.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 07/22/2013] [Accepted: 09/11/2013] [Indexed: 12/28/2022]
Abstract
VopL is an effector protein from Vibrio parahaemolyticus that nucleates actin filaments. VopL consists of a VopL C-terminal domain (VCD) and an array of three WASP homology 2 (WH2) motifs. Here, we report the crystal structure of the VCD dimer bound to actin. The VCD organizes three actin monomers in a spatial arrangement close to that found in the canonical actin filament. In this arrangement, WH2 motifs can be modeled into the binding site of each actin without steric clashes. The data suggest a mechanism of nucleation wherein VopL creates filament-like structures, organized by the VCD with monomers delivered by the WH2 array, that can template addition of new subunits. Similarities with Arp2/3 complex and formin proteins suggest that organization of monomers into filament-like structures is a general and central feature of actin nucleation.
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Affiliation(s)
- Jacob A Zahm
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Abstract
Clustered N-WASP binds directly to actin-filament barbed ends and can either slow individual filament growth or processively accelerate the assembly of bundled actin filaments. This novel Arp2/3-independent mechanism of N-WASP likely plays a role in invadopodia and podosome formation, in which both N-WASP and actin filaments are tightly clustered. Neuronal Wiskott–Aldrich syndrome protein (N-WASP)–activated actin polymerization drives extension of invadopodia and podosomes into the basement layer. In addition to activating Arp2/3, N-WASP binds actin-filament barbed ends, and both N-WASP and barbed ends are tightly clustered in these invasive structures. We use nanofibers coated with N-WASP WWCA domains as model cell surfaces and single-actin-filament imaging to determine how clustered N-WASP affects Arp2/3-independent barbed-end assembly. Individual barbed ends captured by WWCA domains grow at or below their diffusion-limited assembly rate. At high filament densities, however, overlapping filaments form buckles between their nanofiber tethers and myosin attachment points. These buckles grew ∼3.4-fold faster than the diffusion-limited rate of unattached barbed ends. N-WASP constructs with and without the native polyproline (PP) region show similar rate enhancements in the absence of profilin, but profilin slows barbed-end acceleration from constructs containing the PP region. Increasing Mg2+ to enhance filament bundling increases the frequency of filament buckle formation, consistent with a requirement of accelerated assembly on barbed-end bundling. We propose that this novel N-WASP assembly activity provides an Arp2/3-independent force that drives nascent filament bundles into the basement layer during cell invasion.
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Affiliation(s)
- Nimisha Khanduja
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
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41
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Matalon O, Reicher B, Barda-Saad M. Wiskott-Aldrich syndrome protein - dynamic regulation of actin homeostasis: from activation through function and signal termination in T lymphocytes. Immunol Rev 2013; 256:10-29. [DOI: 10.1111/imr.12112] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Omri Matalon
- The Mina and Everard Goodman Faculty of Life Sciences; Bar-Ilan University; Ramat-Gan Israel
| | - Barak Reicher
- The Mina and Everard Goodman Faculty of Life Sciences; Bar-Ilan University; Ramat-Gan Israel
| | - Mira Barda-Saad
- The Mina and Everard Goodman Faculty of Life Sciences; Bar-Ilan University; Ramat-Gan Israel
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42
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Smith BA, Padrick SB, Doolittle LK, Daugherty-Clarke K, Corrêa IR, Xu MQ, Goode BL, Rosen MK, Gelles J. Three-color single molecule imaging shows WASP detachment from Arp2/3 complex triggers actin filament branch formation. eLife 2013; 2:e01008. [PMID: 24015360 PMCID: PMC3762362 DOI: 10.7554/elife.01008] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 07/29/2013] [Indexed: 01/22/2023] Open
Abstract
During cell locomotion and endocytosis, membrane-tethered WASP proteins stimulate actin filament nucleation by the Arp2/3 complex. This process generates highly branched arrays of filaments that grow toward the membrane to which they are tethered, a conflict that seemingly would restrict filament growth. Using three-color single-molecule imaging in vitro we revealed how the dynamic associations of Arp2/3 complex with mother filament and WASP are temporally coordinated with initiation of daughter filament growth. We found that WASP proteins dissociated from filament-bound Arp2/3 complex prior to new filament growth. Further, mutations that accelerated release of WASP from filament-bound Arp2/3 complex proportionally accelerated branch formation. These data suggest that while WASP promotes formation of pre-nucleation complexes, filament growth cannot occur until it is triggered by WASP release. This provides a mechanism by which membrane-bound WASP proteins can stimulate network growth without restraining it. DOI:http://dx.doi.org/10.7554/eLife.01008.001.
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Affiliation(s)
- Benjamin A Smith
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Shae B Padrick
- Department of Biophysics, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Lynda K Doolittle
- Department of Biophysics, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Karen Daugherty-Clarke
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
- Department of Biology, Brandeis University, Waltham, United States
| | | | | | - Bruce L Goode
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
- Department of Biology, Brandeis University, Waltham, United States
| | - Michael K Rosen
- Department of Biophysics, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Jeff Gelles
- Department of Biochemistry, Brandeis University, Waltham, United States
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Xu XP, Slaughter BD, Volkmann N. Probabilistic determination of probe locations from distance data. J Struct Biol 2013; 184:75-82. [PMID: 23770585 DOI: 10.1016/j.jsb.2013.05.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/28/2013] [Accepted: 05/30/2013] [Indexed: 12/24/2022]
Abstract
Distance constraints, in principle, can be employed to determine information about the location of probes within a three-dimensional volume. Traditional methods for locating probes from distance constraints involve optimization of scoring functions that measure how well the probe location fits the distance data, exploring only a small subset of the scoring function landscape in the process. These methods are not guaranteed to find the global optimum and provide no means to relate the identified optimum to all other optima in scoring space. Here, we introduce a method for the location of probes from distance information that is based on probability calculus. This method allows exploration of the entire scoring space by directly combining probability functions representing the distance data and information about attachment sites. The approach is guaranteed to identify the global optimum and enables the derivation of confidence intervals for the probe location as well as statistical quantification of ambiguities. We apply the method to determine the location of a fluorescence probe using distances derived by FRET and show that the resulting location matches that independently derived by electron microscopy.
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Affiliation(s)
- Xiao-Ping Xu
- Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, United States
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Small molecules CK-666 and CK-869 inhibit actin-related protein 2/3 complex by blocking an activating conformational change. ACTA ACUST UNITED AC 2013; 20:701-12. [PMID: 23623350 DOI: 10.1016/j.chembiol.2013.03.019] [Citation(s) in RCA: 238] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/27/2013] [Accepted: 03/19/2013] [Indexed: 11/24/2022]
Abstract
Actin-related protein 2/3 (Arp2/3) complex is a seven-subunit assembly that nucleates branched actin filaments. Small molecule inhibitors CK-666 and CK-869 bind to Arp2/3 complex and inhibit nucleation, but their modes of action are unknown. Here, we use biochemical and structural methods to determine the mechanism of each inhibitor. Our data indicate that CK-666 stabilizes the inactive state of the complex, blocking movement of the Arp2 and Arp3 subunits into the activated filament-like (short pitch) conformation, while CK-869 binds to a serendipitous pocket on Arp3 and allosterically destabilizes the short pitch Arp3-Arp2 interface. These results provide key insights into the relationship between conformation and activity in Arp2/3 complex and will be critical for interpreting the influence of the inhibitors on actin filament networks in vivo.
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Weichsel J, Baczynski K, Schwarz US. Unifying autocatalytic and zeroth-order branching models for growing actin networks. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:040701. [PMID: 23679361 DOI: 10.1103/physreve.87.040701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 12/06/2012] [Indexed: 06/02/2023]
Abstract
The directed polymerization of actin networks is an essential element of many biological processes, including cell migration. Different theoretical models considering the interplay between the underlying processes of polymerization, capping, and branching have resulted in conflicting predictions. One of the main reasons for this discrepancy is the assumption of a branching reaction that is either first order (autocatalytic) or zeroth order in the number of existing filaments. Here we introduce a unifying framework from which the two established scenarios emerge as limiting cases for low and high filament numbers. A smooth transition between the two cases is found at intermediate conditions. We also derive a threshold for the capping rate above which autocatalytic growth is predicted at sufficiently low filament number. Below the threshold, zeroth-order characteristics are predicted to dominate the dynamics of the network for all accessible filament numbers. Together, these mechanisms allow cells to grow stable actin networks over a large range of different conditions.
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Affiliation(s)
- Julian Weichsel
- Bioquant and Institute for Theoretical Physics, University of Heidelberg, Germany.
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Oda A, Eto K. WASPs and WAVEs: from molecular function to physiology in hematopoietic cells. Semin Cell Dev Biol 2013; 24:308-13. [PMID: 23499790 DOI: 10.1016/j.semcdb.2013.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Accepted: 03/04/2013] [Indexed: 12/29/2022]
Abstract
The actin cytoskeleton is critically involved in a variety of cell functions. The Arp2/3 complex mediates branching of filamentous actin. The members of the Wiskott-Aldrich syndrome protein (WASP) family are major regulators of the complex. As such, the family proteins are also involved in numerous aspects of cell biology. In this short review, we first define the expanding WASP family. Next, we compare the domain structure of the members, and explain the known or proposed functions of each domain or region. Finally, we demonstrate the well-characterized roles of the proteins in specific cellular functions.
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Affiliation(s)
- Atsushi Oda
- Department of Internal Medicine, Noguchi Hospital, Ashibetsu 075-0002, Japan.
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Ingerman E, Hsiao JY, Mullins RD. Arp2/3 complex ATP hydrolysis promotes lamellipodial actin network disassembly but is dispensable for assembly. ACTA ACUST UNITED AC 2013; 200:619-33. [PMID: 23439681 PMCID: PMC3587832 DOI: 10.1083/jcb.201211069] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ATP hydrolysis on both Arp2 and Arp3 influences dissociation of the Arp2/3 complex from the lamellipodial actin network but is not strictly necessary for network disassembly. We examined the role of ATP hydrolysis by the Arp2/3 complex in building the leading edge of a cell by studying the effects of hydrolysis defects on the behavior of the complex in the lamellipodial actin network of Drosophila S2 cells and in a reconstituted, in vitro, actin-based motility system. In S2 cells, nonhydrolyzing Arp2 and Arp3 subunits expanded and delayed disassembly of lamellipodial actin networks and the effect of mutant subunits was additive. Arp2 and Arp3 ATP hydrolysis mutants remained in lamellipodial networks longer and traveled greater distances from the plasma membrane, even in networks still containing wild-type Arp2/3 complex. In vitro, wild-type and ATP hydrolysis mutant Arp2/3 complexes each nucleated actin and built similar dendritic networks. However, networks constructed with Arp2/3 hydrolysis-defective mutants were more resistant to disassembly by cofilin. Our results indicate that ATP hydrolysis on both Arp2 and Arp3 contributes to dissociation of the complex from the actin network but is not strictly necessary for lamellipodial network disassembly.
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Affiliation(s)
- Elena Ingerman
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
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48
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Structure of an actin-related subcomplex of the SWI/SNF chromatin remodeler. Proc Natl Acad Sci U S A 2013; 110:3345-50. [PMID: 23401505 DOI: 10.1073/pnas.1215379110] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The packaging of DNA into nucleosomal structures limits access for templated processes such as transcription and DNA repair. The repositioning or ejection of nucleosomes is therefore critically important for regulated events, including gene expression. This activity is provided by chromatin remodeling complexes, or remodelers, which are typically large, multisubunit complexes that use an ATPase subunit to translocate the DNA. Many remodelers contain pairs or multimers of actin-related proteins (ARPs) that contact the helicase-SANT-associated (HSA) domain within the catalytic ATPase subunit and are thought to regulate ATPase activity. Here, we determined the structure of a four-protein subcomplex within the SWI/SNF remodeler that comprises the Snf2 HSA domain, Arp7, Arp9, and repressor of Ty1 transposition, gene 102 (Rtt102). Surprisingly, unlike characterized actin-actin associations, the two ARPs pack like spoons and straddle the HSA domain, which forms a 92-Å-long helix. The ARP-HSA interactions are reminiscent of contacts between actin and many binding partners and are quite different from those in the Arp2/3 complex. Rtt102 wraps around one side of the complex in a highly extended conformation that contacts both ARPs and therefore stabilizes the complex, yet functions to reduce by ∼2.4-fold the remodeling and ATPase activity of complexes containing the Snf2 ATPase domain. Thus, our structure provides a foundation for developing models of remodeler function, including mechanisms of coupling between ARPs and the ATPase translocation activity.
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49
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Shen QT, Hsiue PP, Sindelar CV, Welch MD, Campellone KG, Wang HW. Structural insights into WHAMM-mediated cytoskeletal coordination during membrane remodeling. ACTA ACUST UNITED AC 2013; 199:111-24. [PMID: 23027905 PMCID: PMC3461504 DOI: 10.1083/jcb.201204010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Structural analysis of the WHAMM–microtubule interaction provides insight into WHAMM’s coordination of microtubule binding, membrane association, and actin nucleation. The microtubule (MT) and actin cytoskeletons drive many essential cellular processes, yet fairly little is known about how their functions are coordinated. One factor that mediates important cross talk between these two systems is WHAMM, a Golgi-associated protein that utilizes MT binding and actin nucleation activities to promote membrane tubulation during intracellular transport. Using cryoelectron microscopy and other biophysical and biochemical approaches, we unveil the underlying mechanisms for how these activities are coordinated. We find that WHAMM bound to the outer surface of MT protofilaments via a novel interaction between its central coiled-coil region and tubulin heterodimers. Upon the assembly of WHAMM onto MTs, its N-terminal membrane-binding domain was exposed at the MT periphery, where it can recruit vesicles and remodel them into tubular structures. In contrast, MT binding masked the C-terminal portion of WHAMM and prevented it from promoting actin nucleation. These results give rise to a model whereby distinct MT-bound and actin-nucleating populations of WHAMM collaborate during membrane tubulation.
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Affiliation(s)
- Qing-Tao Shen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
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50
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MacGrath SM, Koleske AJ. Cortactin in cell migration and cancer at a glance. J Cell Sci 2013; 125:1621-6. [PMID: 22566665 DOI: 10.1242/jcs.093781] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Stacey M MacGrath
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
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