1
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Hansen AL, Xiang X, Yuan C, Bruschweiler-Li L, Brüschweiler R. Excited-state observation of active K-Ras reveals differential structural dynamics of wild-type versus oncogenic G12D and G12C mutants. Nat Struct Mol Biol 2023; 30:1446-1455. [PMID: 37640864 PMCID: PMC10584678 DOI: 10.1038/s41594-023-01070-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 07/17/2023] [Indexed: 08/31/2023]
Abstract
Despite the prominent role of the K-Ras protein in many different types of human cancer, major gaps in atomic-level information severely limit our understanding of its functions in health and disease. Here, we report the quantitative backbone structural dynamics of K-Ras by solution nuclear magnetic resonance spectroscopy of the active state of wild-type K-Ras bound to guanosine triphosphate (GTP) nucleotide and two of its oncogenic P-loop mutants, G12D and G12C, using a new nanoparticle-assisted spin relaxation method, relaxation dispersion and chemical exchange saturation transfer experiments covering the entire range of timescales from picoseconds to milliseconds. Our combined experiments allow detection and analysis of the functionally critical Switch I and Switch II regions, which have previously remained largely unobservable by X-ray crystallography and nuclear magnetic resonance spectroscopy. Our data reveal cooperative transitions of K-Ras·GTP to a highly dynamic excited state that closely resembles the partially disordered K-Ras·GDP state. These results advance our understanding of differential GTPase activities and signaling properties of the wild type versus mutants and may thus guide new strategies for the development of therapeutics.
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Affiliation(s)
- Alexandar L Hansen
- Campus Chemical Instrument Center, The Ohio State University, Columbus, OH, USA
| | - Xinyao Xiang
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
| | - Chunhua Yuan
- Campus Chemical Instrument Center, The Ohio State University, Columbus, OH, USA
| | - Lei Bruschweiler-Li
- Campus Chemical Instrument Center, The Ohio State University, Columbus, OH, USA.
| | - Rafael Brüschweiler
- Campus Chemical Instrument Center, The Ohio State University, Columbus, OH, USA.
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA.
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2
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Bjornson KJ, Vanderplow AM, Yang Y, Anderson DR, Kermath BA, Cahill ME. Stress-mediated dysregulation of the Rap1 small GTPase impairs hippocampal structure and function. iScience 2023; 26:107566. [PMID: 37664580 PMCID: PMC10470260 DOI: 10.1016/j.isci.2023.107566] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 05/15/2023] [Accepted: 08/02/2023] [Indexed: 09/05/2023] Open
Abstract
The effects of repeated stress on cognitive impairment are thought to be mediated, at least in part, by reductions in the stability of dendritic spines in brain regions critical for proper learning and memory, including the hippocampus. Small GTPases are particularly potent regulators of dendritic spine formation, stability, and morphology in hippocampal neurons. Through the use of small GTPase protein profiling in mice, we identify increased levels of synaptic Rap1 in the hippocampal CA3 region in response to escalating, intermittent stress. We then demonstrate that increased Rap1 in the CA3 is sufficient in and of itself to produce stress-relevant dendritic spine and cognitive phenotypes. Further, using super-resolution imaging, we investigate how the pattern of Rap1 trafficking to synapses likely underlies its effects on the stability of select dendritic spine subtypes. These findings illuminate the involvement of aberrant Rap1 regulation in the hippocampus in contributing to the psychobiological effects of stress.
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Affiliation(s)
- Kathryn J. Bjornson
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Amanda M. Vanderplow
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Yezi Yang
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Danielle R. Anderson
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Bailey A. Kermath
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Michael E. Cahill
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
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3
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Hiremath C, Gao L, Geshow K, Patterson Q, Barlow H, Cleaver O, Marciano DK. Rap1 regulates lumen continuity via Afadin in renal epithelia. Dev Biol 2023; 501:20-27. [PMID: 37276970 PMCID: PMC10460627 DOI: 10.1016/j.ydbio.2023.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 04/13/2023] [Accepted: 05/11/2023] [Indexed: 06/07/2023]
Abstract
The continuity of a lumen within an epithelial tubule is critical for its function. We previously found that the F-actin binding protein Afadin is required for timely lumen formation and continuity in renal tubules formed from the nephrogenic mesenchyme in mice. Afadin is a known effector and interactor of the small GTPase Rap1, and in the current study, we examine the role of Rap1 in nephron tubulogenesis. Here, we demonstrate that Rap1 is required for nascent lumen formation and continuity in cultured 3D epithelial spheroids and in vivo in murine renal epithelial tubules derived from the nephrogenic mesenchyme, where its absence ultimately leads to severe morphogenetic defects in the tubules. By contrast, Rap1 is not required for lumen continuity or morphogenesis in renal tubules derived from the ureteric epithelium, which differ in that they form by extension from a pre-existing tubule. We further demonstrate that Rap1 is required for correct localization of Afadin to adherens junctions both in vitro and in vivo. Together, these results suggest a model in which Rap1 localizes Afadin to junctional complexes, which in turn regulates nascent lumen formation and positioning to ensure continuous tubulogenesis.
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Affiliation(s)
- Chitkale Hiremath
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Lei Gao
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Kenya Geshow
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Quinten Patterson
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Haley Barlow
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Ondine Cleaver
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Denise K Marciano
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA.
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4
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Smith MJ. Defining bone fide effectors of RAS GTPases. Bioessays 2023; 45:e2300088. [PMID: 37401638 DOI: 10.1002/bies.202300088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/20/2023] [Accepted: 06/22/2023] [Indexed: 07/05/2023]
Abstract
RAS GTPases play essential roles in normal development and are direct drivers of human cancers. Three decades of study have failed to wholly characterize pathways stimulated by activated RAS, driven by engagement with 'effector' proteins that have RAS binding domains (RBDs). Bone fide effectors must bind directly to RAS GTPases in a nucleotide-dependent manner, and this interaction must impart a clear change in effector activity. Despite this, for most proteins currently deemed effectors there is little mechanistic understanding of how binding to the GTPase alters protein function. There has also been limited effort to comprehensively resolve the specificity of effector binding to the full array of RAS superfamily GTPase proteins. This review will summarize what is known about RAS-driven activation for an array of potential effector proteins, focusing on structural and mechanistic effects and highlighting how little is still known regarding this key paradigm of cellular signal transduction.
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Affiliation(s)
- Matthew J Smith
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec, Canada
- Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada
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5
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Goudreault M, Gagné V, Jo CH, Singh S, Killoran RC, Gingras AC, Smith MJ. Afadin couples RAS GTPases to the polarity rheostat Scribble. Nat Commun 2022; 13:4562. [PMID: 35931706 PMCID: PMC9355967 DOI: 10.1038/s41467-022-32335-8] [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] [Received: 11/12/2021] [Accepted: 07/26/2022] [Indexed: 11/10/2022] Open
Abstract
AFDN/Afadin is required for establishment and maintenance of cell-cell contacts and is a unique effector of RAS GTPases. The biological consequences of RAS complex with AFDN are unknown. We used proximity-based proteomics to generate an interaction map for two isoforms of AFDN, identifying the polarity protein SCRIB/Scribble as the top hit. We reveal that the first PDZ domain of SCRIB and the AFDN FHA domain mediate a direct but non-canonical interaction between these important adhesion and polarity proteins. Further, the dual RA domains of AFDN have broad specificity for RAS and RAP GTPases, and KRAS co-localizes with AFDN and promotes AFDN-SCRIB complex formation. Knockout of AFDN or SCRIB in epithelial cells disrupts MAPK and PI3K activation kinetics and inhibits motility in a growth factor-dependent manner. These data have important implications for understanding why cells with activated RAS have reduced cell contacts and polarity defects and implicate AFDN as a genuine RAS effector. Goudreault et al. investigate the role of Afadin downstream of RAS GTPases, substantiating this cell adhesion protein as a true RAS effector that couples its activation to cell polarity through the Scribble protein.
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Affiliation(s)
- Marilyn Goudreault
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Valérie Gagné
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Chang Hwa Jo
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Swati Singh
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Ryan C Killoran
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Anne-Claude Gingras
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, M5G 1X5, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, M5G 1X5, Canada
| | - Matthew J Smith
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, H3T 1J4, Canada. .,Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, QC, H3T 1J4, Canada.
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6
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RAS GTPase signalling to alternative effector pathways. Biochem Soc Trans 2021; 48:2241-2252. [PMID: 33125484 DOI: 10.1042/bst20200506] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 09/21/2020] [Accepted: 09/23/2020] [Indexed: 02/07/2023]
Abstract
RAS GTPases are fundamental regulators of development and drivers of an extraordinary number of human cancers. RAS oncoproteins constitutively signal through downstream effector proteins, triggering cancer initiation, progression and metastasis. In the absence of targeted therapeutics to mutant RAS itself, inhibitors of downstream pathways controlled by the effector kinases RAF and PI3K have become tools in the treatment of RAS-driven tumours. Unfortunately, the efficacy of this approach has been greatly minimized by the prevalence of acquired drug resistance. Decades of research have established that RAS signalling is highly complex, and in addition to RAF and PI3K these small GTPase proteins can interact with an array of alternative effectors that feature RAS binding domains. The consequence of RAS binding to these effectors remains relatively unexplored, but these pathways may provide targets for combinatorial therapeutics. We discuss here three candidate alternative effectors: RALGEFs, RASSF5 and AFDN, detailing their interaction with RAS GTPases and their biological significance. The metastatic nature of RAS-driven cancers suggests more attention should be granted to these alternate pathways, as they are highly implicated in the regulation of cell adhesion, polarity, cell size and cytoskeletal architecture.
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7
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Huxham J, Tabariès S, Siegel PM. Afadin (AF6) in cancer progression: A multidomain scaffold protein with complex and contradictory roles. Bioessays 2020; 43:e2000221. [PMID: 33165933 DOI: 10.1002/bies.202000221] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 09/17/2020] [Accepted: 09/24/2020] [Indexed: 11/09/2022]
Abstract
Adherens (AJ) and tight junctions (TJ) maintain cell-cell adhesions and cellular polarity in normal tissues. Afadin, a multi-domain scaffold protein, is commonly found in both adherens and tight junctions, where it plays both structural and signal-modulating roles. Afadin is a complex modulator of cellular processes implicated in cancer progression, including signal transduction, migration, invasion, and apoptosis. In keeping with the complexities associated with the roles of adherens and tight junctions in cancer, afadin exhibits both tumor suppressive and pro-metastatic functions. In this review, we will explore the dichotomous roles that afadin plays during cancer progression.
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Affiliation(s)
- Jennifer Huxham
- Goodman Cancer Research Centre, McGill University, Montréal, Québec, Canada.,Department of Medicine, McGill University, Montréal, Québec, Canada
| | - Sébastien Tabariès
- Goodman Cancer Research Centre, McGill University, Montréal, Québec, Canada.,Department of Medicine, McGill University, Montréal, Québec, Canada
| | - Peter M Siegel
- Goodman Cancer Research Centre, McGill University, Montréal, Québec, Canada.,Department of Medicine, McGill University, Montréal, Québec, Canada.,Department of Biochemistry, McGill University, Montréal, Québec, Canada.,Department of Anatomy & Cell Biology, McGill University, Montréal, Québec, Canada.,Department of Oncology, McGill University, Montréal, Québec, Canada
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8
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Johansen JS, Kavaliauskas D, Pfeil SH, Blaise M, Cooperman BS, Goldman YE, Thirup SS, Knudsen CR. E. coli elongation factor Tu bound to a GTP analogue displays an open conformation equivalent to the GDP-bound form. Nucleic Acids Res 2019; 46:8641-8650. [PMID: 30107565 PMCID: PMC6144822 DOI: 10.1093/nar/gky697] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 08/07/2018] [Indexed: 11/12/2022] Open
Abstract
According to the traditional view, GTPases act as molecular switches, which cycle between distinct ‘on’ and ‘off’ conformations bound to GTP and GDP, respectively. Translation elongation factor EF-Tu is a GTPase essential for prokaryotic protein synthesis. In its GTP-bound form, EF-Tu delivers aminoacylated tRNAs to the ribosome as a ternary complex. GTP hydrolysis is thought to cause the release of EF-Tu from aminoacyl-tRNA and the ribosome due to a dramatic conformational change following Pi release. Here, the crystal structure of Escherichia coli EF-Tu in complex with a non-hydrolysable GTP analogue (GDPNP) has been determined. Remarkably, the overall conformation of EF-Tu·GDPNP displays the classical, open GDP-bound conformation. This is in accordance with an emerging view that the identity of the bound guanine nucleotide is not ‘locking’ the GTPase in a fixed conformation. Using a single-molecule approach, the conformational dynamics of various ligand-bound forms of EF-Tu were probed in solution by fluorescence resonance energy transfer. The results suggest that EF-Tu, free in solution, may sample a wider set of conformations than the structurally well-defined GTP- and GDP-forms known from previous X-ray crystallographic studies. Only upon binding, as a ternary complex, to the mRNA-programmed ribosome, is the well-known, closed GTP-bound conformation, observed.
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Affiliation(s)
- Jesper S Johansen
- Department of Molecular Biology & Genetics, University of Aarhus, Gustav Wieds Vej 10 C, DK-8000 Aarhus C, Denmark
| | - Darius Kavaliauskas
- Department of Molecular Biology & Genetics, University of Aarhus, Gustav Wieds Vej 10 C, DK-8000 Aarhus C, Denmark
| | - Shawn H Pfeil
- Department of Physics, West Chester University, West Chester, PA 19383, USA
| | - Mickaël Blaise
- Department of Molecular Biology & Genetics, University of Aarhus, Gustav Wieds Vej 10 C, DK-8000 Aarhus C, Denmark
| | - Barry S Cooperman
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yale E Goldman
- Pennsylvania Muscle Institute, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Søren S Thirup
- Department of Molecular Biology & Genetics, University of Aarhus, Gustav Wieds Vej 10 C, DK-8000 Aarhus C, Denmark
| | - Charlotte R Knudsen
- Department of Molecular Biology & Genetics, University of Aarhus, Gustav Wieds Vej 10 C, DK-8000 Aarhus C, Denmark
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9
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CRIB effector disorder: exquisite function from chaos. Biochem Soc Trans 2018; 46:1289-1302. [PMID: 30154092 DOI: 10.1042/bst20170570] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 07/25/2018] [Accepted: 07/26/2018] [Indexed: 11/17/2022]
Abstract
The CRIB (Cdc42/Rac interactive binding) family of small G-protein effectors contain significant regions with intrinsic disorder. The G-protein-binding regions are contained within these intrinsically disordered regions. Most CRIB proteins also contain stretches of basic residues associated with their G-protein-binding regions. The basic region (BR) and G-protein-binding region together allow the CRIB effectors to bind to their cognate G-protein via a dock- and coalesce-binding mechanism. The BRs of these proteins take on multiple roles: steering G-protein binding, interacting with elements of the membrane and regulating intramolecular regulatory interactions. The ability of these regions of the CRIBs to undergo multivalent interactions and mediate charge neutralizations equips them with all the properties required to drive liquid-liquid phase separation and therefore to initiate and drive signalosome formation. It is only recently that the structural plasticity in these proteins is being appreciated as the driving force for these vital cellular processes.
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10
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Nagy JI, Lynn BD. Structural and Intermolecular Associations Between Connexin36 and Protein Components of the Adherens Junction-Neuronal Gap Junction Complex. Neuroscience 2018; 384:241-261. [PMID: 29879437 DOI: 10.1016/j.neuroscience.2018.05.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/17/2018] [Accepted: 05/18/2018] [Indexed: 11/20/2022]
Abstract
Intimate structural and functional relationships between gap junctions and adherens junctions have been demonstrated in peripheral tissues, but have not been thoroughly examined in the central nervous system, where adherens junctions are often found in close proximity to neuronal gap junctions. Here, we used immunofluorescence approaches to document the localization of various protein components of adherens junctions in relation to those that we have previously reported to occur at electrical synapses formed by neuronal gap junctions composed of connexin36 (Cx36). The adherens junction constituents N-cadherin and nectin-1 were frequently found to localize near or overlap with Cx36-containing gap junctions in several brain regions examined. This was also true of the adherens junction-associated proteins α-catenin and β-catenin, as well as the proteins zonula occludens-1 and AF6 (aka, afadin) that were reported constituents of both adherens junctions and gap junctions. The deployment of the protein constituents of these junctions was especially striking at somatic contacts between primary afferent neurons in the mesencephalic trigeminal nucleus (MesV), where the structural components of adherens junctions appeared to be maintained in connexin36 null mice. These results support emerging views concerning the multi-molecular composition of electrical synapses and raise possibilities for various structural and functional protein-protein interactions at what now can be considered the adherens junction-neuronal gap junction complex. Further, the results point to intracellular signaling pathways that could potentially contribute to the assembly, maintenance and turnover of this complex, as well as to the dynamic nature of neuronal communication at electrical synapses.
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Affiliation(s)
- J I Nagy
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada.
| | - B D Lynn
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
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11
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Sakakibara S, Maruo T, Miyata M, Mizutani K, Takai Y. Requirement of the F-actin-binding activity of l-afadin for enhancing the formation of adherens and tight junctions. Genes Cells 2018; 23:185-199. [DOI: 10.1111/gtc.12566] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Accepted: 01/09/2018] [Indexed: 12/26/2022]
Affiliation(s)
- Shotaro Sakakibara
- Division of Pathogenetic Signaling; Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe Japan
| | - Tomohiko Maruo
- Division of Pathogenetic Signaling; Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe Japan
| | - Muneaki Miyata
- Division of Pathogenetic Signaling; Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe Japan
| | - Kiyohito Mizutani
- Division of Pathogenetic Signaling; Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe Japan
| | - Yoshimi Takai
- Division of Pathogenetic Signaling; Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe Japan
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12
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Gao L, Yang Z, Hiremath C, Zimmerman SE, Long B, Brakeman PR, Mostov KE, Bryant DM, Luby-Phelps K, Marciano DK. Afadin orients cell division to position the tubule lumen in developing renal tubules. Development 2017; 144:3511-3520. [PMID: 28860115 DOI: 10.1242/dev.148908] [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: 01/13/2017] [Accepted: 08/11/2017] [Indexed: 01/05/2023]
Abstract
In many types of tubules, continuity of the lumen is paramount to tubular function, yet how tubules generate lumen continuity in vivo is not known. We recently found that the F-actin-binding protein afadin is required for lumen continuity in developing renal tubules, though its mechanism of action remains unknown. Here, we demonstrate that afadin is required for lumen continuity by orienting the mitotic spindle during cell division. Using an in vitro 3D cyst model, we find that afadin localizes to the cell cortex adjacent to the spindle poles and orients the mitotic spindle. In tubules, cell division may be oriented relative to two axes: longitudinal and apical-basal. Unexpectedly, in vivo examination of early-stage developing nephron tubules reveals that cell division is not oriented in the longitudinal (or planar-polarized) axis. However, cell division is oriented perpendicular to the apical-basal axis. Absence of afadin in vivo leads to misorientation of apical-basal cell division in nephron tubules. Together, these results support a model whereby afadin determines lumen placement by directing apical-basal spindle orientation, resulting in a continuous lumen and normal tubule morphogenesis.
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Affiliation(s)
- Lei Gao
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Zhufeng Yang
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Chitkale Hiremath
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Susan E Zimmerman
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Blake Long
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Paul R Brakeman
- Department of Pediatrics, University of California, San Francisco, CA, 94158, USA
| | - Keith E Mostov
- Department of Anatomy, University of California, San Francisco, CA, 94158, USA
| | - David M Bryant
- Institute of Cancer Sciences, University of Glasgow and Cancer Research UK Beatson Institute, Glasgow G61 1BD, UK
| | | | - Denise K Marciano
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
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13
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Nakhaeizadeh H, Amin E, Nakhaei-Rad S, Dvorsky R, Ahmadian MR. The RAS-Effector Interface: Isoform-Specific Differences in the Effector Binding Regions. PLoS One 2016; 11:e0167145. [PMID: 27936046 PMCID: PMC5147862 DOI: 10.1371/journal.pone.0167145] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 11/09/2016] [Indexed: 12/31/2022] Open
Abstract
RAS effectors specifically interact with the GTP-bound form of RAS in response to extracellular signals and link them to downstream signaling pathways. The molecular nature of effector interaction by RAS is well-studied but yet still incompletely understood in a comprehensive and systematic way. Here, structure-function relationships in the interaction between different RAS proteins and various effectors were investigated in detail by combining our in vitro data with in silico data. Equilibrium dissociation constants were determined for the binding of HRAS, KRAS, NRAS, RRAS1 and RRAS2 to both the RAS binding (RB) domain of CRAF and PI3Kα, and the RAS association (RA) domain of RASSF5, RALGDS and PLCε, respectively, using fluorescence polarization. An interaction matrix, constructed on the basis of available crystal structures, allowed identification of hotspots as critical determinants for RAS-effector interaction. New insights provided by this study are the dissection of the identified hotspots in five distinct regions (R1 to R5) in spite of high sequence variability not only between, but also within, RB/RA domain-containing effectors proteins. Finally, we propose that intermolecular β-sheet interaction in R1 is a central recognition region while R3 may determine specific contacts of RAS versus RRAS isoforms with effectors.
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Affiliation(s)
- Hossein Nakhaeizadeh
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
| | - Ehsan Amin
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
| | - Saeideh Nakhaei-Rad
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
| | - Radovan Dvorsky
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
| | - Mohammad Reza Ahmadian
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
- * E-mail:
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14
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Mott HR, Owen D. Structures of Ras superfamily effector complexes: What have we learnt in two decades? Crit Rev Biochem Mol Biol 2015; 50:85-133. [PMID: 25830673 DOI: 10.3109/10409238.2014.999191] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The Ras superfamily small G proteins are master regulators of a diverse range of cellular processes and act via downstream effector molecules. The first structure of a small G protein-effector complex, that of Rap1A with c-Raf1, was published 20 years ago. Since then, the structures of more than 60 small G proteins in complex with their effectors have been published. These effectors utilize a diverse array of structural motifs to interact with the G protein fold, which we have divided into four structural classes: intermolecular β-sheets, helical pairs, other interactions, and pleckstrin homology (PH) domains. These classes and their representative structures are discussed and a contact analysis of the interactions is presented, which highlights the common effector-binding regions between and within the small G protein families.
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Affiliation(s)
- Helen R Mott
- Department of Biochemistry, University of Cambridge , Cambridge , UK
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15
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Tanaka-Okamoto M, Itoh Y, Miyoshi J, Mizoguchi A, Mizutani K, Takai Y, Inoue M. Genetic ablation of afadin causes mislocalization and deformation of Paneth cells in the mouse small intestinal epithelium. PLoS One 2014; 9:e110549. [PMID: 25333284 PMCID: PMC4204899 DOI: 10.1371/journal.pone.0110549] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 09/15/2014] [Indexed: 12/23/2022] Open
Abstract
Afadin is an actin filament-binding protein that acts cooperatively in cell adhesion with the cell adhesion molecule nectin, and in directional cell movement with the small G protein Rap1 in a nectin-independent manner. We studied the role of afadin in the organization of the small intestinal epithelium using afadin conditional gene knockout (cKO) mice. Afadin was localized at adherens junctions of all types of epithelial cells throughout the crypt-villus axis. Paneth cells were localized at the base of the crypt in control mice, but not confined there, and migrated into the villi in afadin-cKO mice. The distribution of other types of epithelial cells did not change significantly in the mutant mice. The Paneth cells remaining in the crypt exhibited abnormal shapes, were buried between adjacent cells, and did not face the lumen. In these cells, the formation of adherens junctions and tight junctions was impaired. Rap1 and EphB3 were highly expressed in control Paneth cells but markedly down-regulated in the afadin-deficient Paneth cells. Taken together, the results indicate that afadin plays a role in the restricted localization of Paneth cells at the base of the crypt by maintaining their adhesion to adjacent crypt cells and inhibiting their movement toward the top of villi.
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Affiliation(s)
- Miki Tanaka-Okamoto
- Department of Molecular Biology, Osaka Medical Center for Cancer and Cardiovascular Disease, Osaka, Japan
- Department of Biochemistry, Osaka Medical Center for Cancer and Cardiovascular Disease, Osaka, Japan
- * E-mail: (MT-O); (MI)
| | - Yu Itoh
- Department of Molecular Biology, Osaka Medical Center for Cancer and Cardiovascular Disease, Osaka, Japan
- Department of Neural Regeneration and Cell Communication, Mie University Graduate School of Medicine, Mie, Japan
| | - Jun Miyoshi
- Department of Molecular Biology, Osaka Medical Center for Cancer and Cardiovascular Disease, Osaka, Japan
| | - Akira Mizoguchi
- Department of Neural Regeneration and Cell Communication, Mie University Graduate School of Medicine, Mie, Japan
| | - Kiyohito Mizutani
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan
| | - Yoshimi Takai
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan
| | - Masahiro Inoue
- Department of Biochemistry, Osaka Medical Center for Cancer and Cardiovascular Disease, Osaka, Japan
- * E-mail: (MT-O); (MI)
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Rosnizeck IC, Filchtinski D, Lopes RP, Kieninger B, Herrmann C, Kalbitzer HR, Spoerner M. Elucidating the mode of action of a typical Ras state 1(T) inhibitor. Biochemistry 2014; 53:3867-78. [PMID: 24866928 DOI: 10.1021/bi401689w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The small GTPase Ras is an essential component of signal transduction pathways within the cell, controlling proliferation, differentiation, and apoptosis. Only in the GTP-bound form does Ras interact strongly with effector molecules such as Raf-kinase, thus acting as a molecular switch. In the GTP-bound form, Ras exists in a dynamic equilibrium between at least two distinct conformational states, 1(T) and 2(T), offering different functional properties of the protein. Zn2+-cyclen is a typical state 1(T) inhibitor; i.e., it interacts selectively with Ras in conformational state 1(T), a weak effector binding state. Here we report that active K-Ras4B, which is prominently found to be mutated in human tumors, exhibits a dynamic equilibrium like H-Ras, which can be modulated by Zn2+-cyclen. The titration experiments of Ras with Zn2+-cyclen indicate a cooperatively coupled binding of the ligands to the two interaction sites on Ras that could be identified for H-Ras previously. Our data further indicate that as in state 2(T) where induced fit produces the substate 2(T)* after effector binding, a corresponding substate 1(T)* can be detected at the state 1(T) mutant Ras(T35A). The interaction of Zn2+-cyclen with Ras not only shifts the equilibrium toward the weak effector binding state 1(T) but also perturbs the formation of substate 1(T)*, thus enhancing the inhibitory effect. Although Zn2+-cyclen shows an affinity for Ras in only the millimolar range, its potency of inhibition corresponds to a competitive state 2 inhibitor with micromolar binding affinity. Thus, the results demonstrate the mode of action and potency of this class of allosteric Ras inhibitors.
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Filić V, Marinović M, Faix J, Weber I. The IQGAP-related protein DGAP1 mediates signaling to the actin cytoskeleton as an effector and a sequestrator of Rac1 GTPases. Cell Mol Life Sci 2014; 71:2775-85. [PMID: 24664433 PMCID: PMC11113302 DOI: 10.1007/s00018-014-1606-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 02/26/2014] [Accepted: 03/10/2014] [Indexed: 11/24/2022]
Abstract
Proteins are typically categorized into protein families based on their domain organization. Yet, evolutionarily unrelated proteins can also be grouped together according to their common functional roles. Sequestering proteins constitute one such functional class, acting as macromolecular buffers and serving as an intracellular reservoir ready to release large quantities of bound proteins or other molecules upon appropriate stimulation. Another functional protein class comprises effector proteins, which constitute essential components of many intracellular signal transduction pathways. For instance, effectors of small GTP-hydrolases are activated upon binding a GTP-bound GTPase and thereupon participate in downstream interactions. Here we describe a member of the IQGAP family of scaffolding proteins, DGAP1 from Dictyostelium, which unifies the roles of an effector and a sequestrator in regard to the small GTPase Rac1. Unlike classical effectors, which bind their activators transiently leading to short-lived signaling complexes, interaction between DGAP1 and Rac1-GTP is stable and induces formation of a complex with actin-bundling proteins cortexillins at the back end of the cell. An oppositely localized Rac1 effector, the Scar/WAVE complex, promotes actin polymerization at the cell front. Competition between DGAP1 and Scar/WAVE for the common activator Rac1-GTP might provide the basis for the oscillatory re-polarization typically seen in randomly migrating Dictyostelium cells. We discuss the consequences of the dual roles exerted by DGAP1 and Rac1 in the regulation of cell motility and polarity, and propose that similar signaling mechanisms may be of general importance in regulating spatiotemporal dynamics of the actin cytoskeleton by small GTPases.
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Affiliation(s)
- Vedrana Filić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
| | - Maja Marinović
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
| | - Jan Faix
- Hannover Medical School, Institute for Biophysical Chemistry, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Igor Weber
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
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18
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Kalbitzer HR, Rosnizeck IC, Munte CE, Narayanan SP, Kropf V, Spoerner M. Intrinsische allosterische Hemmung von Signalproteinen durch Stabilisierung gering besetzter, durch Hochdruck-NMR-Spektroskopie nachweisbarer Interaktionszustände. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201305741] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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19
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Kalbitzer HR, Rosnizeck IC, Munte CE, Narayanan SP, Kropf V, Spoerner M. Intrinsic Allosteric Inhibition of Signaling Proteins by Targeting Rare Interaction States Detected by High-Pressure NMR Spectroscopy. Angew Chem Int Ed Engl 2013; 52:14242-6. [DOI: 10.1002/anie.201305741] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/20/2013] [Indexed: 11/10/2022]
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20
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Choi W, Harris NJ, Sumigray KD, Peifer M. Rap1 and Canoe/afadin are essential for establishment of apical-basal polarity in the Drosophila embryo. Mol Biol Cell 2013; 24:945-63. [PMID: 23363604 PMCID: PMC3608504 DOI: 10.1091/mbc.e12-10-0736] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The small GTPase Rap1 and the actin-junctional linker protein Canoe/afadin are essential for the initial establishment of polarity in Drosophila, acting upstream of Bazooka/Par3 and the adherens junctions. However, feedback and cross-regulation occur, so polarity establishment is regulated by a network of proteins rather than a linear pathway. The establishment and maintenance of apical–basal cell polarity is critical for assembling epithelia and maintaining organ architecture. Drosophila embryos provide a superb model. In the current view, apically positioned Bazooka/Par3 is the initial polarity cue as cells form during cellularization. Bazooka then helps to position both adherens junctions and atypical protein kinase C (aPKC). Although a polarized cytoskeleton is critical for Bazooka positioning, proteins mediating this remained unknown. We found that the small GTPase Rap1 and the actin-junctional linker Canoe/afadin are essential for polarity establishment, as both adherens junctions and Bazooka are mispositioned in their absence. Rap1 and Canoe do not simply organize the cytoskeleton, as actin and microtubules become properly polarized in their absence. Canoe can recruit Bazooka when ectopically expressed, but they do not obligatorily colocalize. Rap1 and Canoe play continuing roles in Bazooka localization during gastrulation, but other polarity cues partially restore apical Bazooka in the absence of Rap1 or Canoe. We next tested the current linear model for polarity establishment. Both Bazooka and aPKC regulate Canoe localization despite being “downstream” of Canoe. Further, Rap1, Bazooka, and aPKC, but not Canoe, regulate columnar cell shape. These data reshape our view, suggesting that polarity establishment is regulated by a protein network rather than a linear pathway.
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Affiliation(s)
- Wangsun Choi
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
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21
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22
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Rosnizeck IC, Spoerner M, Harsch T, Kreitner S, Filchtinski D, Herrmann C, Engel D, König B, Kalbitzer HR. Metal-Bis(2-picolyl)amine Complexes as State 1(T) Inhibitors of Activated Ras Protein. Angew Chem Int Ed Engl 2012; 51:10647-51. [DOI: 10.1002/anie.201204148] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Indexed: 11/10/2022]
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23
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Rosnizeck IC, Spoerner M, Harsch T, Kreitner S, Filchtinski D, Herrmann C, Engel D, König B, Kalbitzer HR. Metall-Bis(2-picolyl)amin-Komplexe als Zustand-1(T)-Inhibitoren für aktiviertes Ras-Protein. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204148] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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O'Keefe DD, Gonzalez-Niño E, Edgar BA, Curtiss J. Discontinuities in Rap1 activity determine epithelial cell morphology within the developing wing of Drosophila. Dev Biol 2012; 369:223-34. [PMID: 22776378 DOI: 10.1016/j.ydbio.2012.06.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Revised: 05/31/2012] [Accepted: 06/28/2012] [Indexed: 11/28/2022]
Abstract
Mechanisms that govern cell-fate specification within developing epithelia have been intensely investigated, with many of the critical intercellular signaling pathways identified, and well characterized. Much less is known, however, about downstream events that drive the morphological differentiation of these cells, once their fate has been determined. In the Drosophila wing-blade epithelium, two cell types predominate: vein and intervein. After cell proliferation is complete and adhesive cell-cell contacts have been refined, the vast majority of intervein cells adopt a hexagonal morphology. Within vein territories, however, cell-shape refinement results in trapezoids. Signaling events that differentiate between vein and intervein cell fates are well understood, but the genetic pathways underlying vein/intervein cyto-architectural differences remain largely undescribed. We show here that the Rap1 GTPase plays a critical role in determining cell-type-specific morphologies within the developing wing epithelium. Rap1, together with its effector Canoe, promotes symmetric distribution of the adhesion molecule DE-cadherin about the apicolateral circumference of epithelial cells. We provide evidence that in presumptive vein tissue Rap1/Canoe activity is down-regulated, resulting in adhesive asymmetries and non-hexagonal cell morphologies. In particular Canoe levels are reduced in vein cells as they morphologically differentiate. We also demonstrate that over-expression of Rap1 disrupts vein formation both in the developing epithelium and the adult wing blade. Therefore, vein/intervein morphological differences result, at least in part, from the patterned regulation of Rap1 activity.
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Affiliation(s)
- David D O'Keefe
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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25
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Li X, Lynn BD, Nagy JI. The effector and scaffolding proteins AF6 and MUPP1 interact with connexin36 and localize at gap junctions that form electrical synapses in rodent brain. Eur J Neurosci 2012; 35:166-81. [PMID: 22211808 DOI: 10.1111/j.1460-9568.2011.07947.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Electrical synapses formed by neuronal gap junctions composed of connexin36 (Cx36) occur in most major structures in the mammalian central nervous system. These synapses link ensembles of neurons and influence their network properties. Little is known about the macromolecular constituents of neuronal gap junctions or how transmission through electrical synapses is regulated at the level of channel conductance or gap junction assembly/disassembly. Such knowledge is a prerequisite to understanding the roles of gap junctions in neuronal circuitry. Gap junctions share similarities with tight and adhesion junctions in that all three reside at close plasma membrane appositions, and therefore may associate with similar structural and regulatory proteins. Previously, we reported that the tight junction-associated protein zonula occludens-1 (ZO-1) interacts with Cx36 and is localized at gap junctions. Here, we demonstrate that two proteins known to be associated with tight and adherens junctions, namely AF6 and MUPP1, are components of neuronal gap junctions in rodent brain. By immunofluorescence, AF6 and MUPP1 were co-localized with Cx36 in many brain areas. Co-immunoprecipitation and pull-down approaches revealed an association of Cx36 with AF6 and MUPP1, which required the C-terminus PDZ domain interaction motif of Cx36 for interaction with the single PDZ domain of AF6 and with the 10th PDZ domain of MUPP1. As AF6 is a target of the cAMP/Epac/Rap1 signalling pathway and MUPP1 is a scaffolding protein that interacts with CaMKII, the present results suggest that AF6 may be a target for cAMP/Epac/Rap1 signalling at electrical synapses, and that MUPP1 may contribute to anchoring CaMKII at these synapses.
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Affiliation(s)
- X Li
- Department of Physiology, Faculty of Medicine, University of Manitoba, 745 Bannatyne Ave., Winnipeg, Manitoba, Canada
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26
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Kim J, Chang A, Dudak A, Federoff HJ, Lim ST. Characterization of nectin processing mediated by presenilin-dependent γ-secretase. J Neurochem 2011; 119:945-56. [PMID: 21910732 DOI: 10.1111/j.1471-4159.2011.07479.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nectins play an important role in forming various intercellular junctions including synapses. This role is regulated by several secretases present at intercellular junctions. We have investigated presenilin (PS)-dependent secretase-mediated processing of nectins in PS1 KO cells and primary hippocampal neurons. The loss of PS1/γ-secretase activity delayed the processing of nectin-1 and caused the accumulation of its full-length and C-terminal fragments. Over-expression of PS2 in PS1 KO cells compensated for the loss of PS1, suggesting that PS2 also has the ability to regulate nectin-1 processing. In mouse brain slices, a pronounced increase in levels of 30 and 24 kDa C-terminal fragments in response to chemical long-term potentiation was observed. The mouse brain synaptosomal fractionation study indicated that nectin-1 localized to post-synaptic and preferentially pre-synaptic membranes and that shedding occurs in both compartments. These data suggest that nectin-1 shedding and PS-dependent intramembrane cleavage occur at synapses, and is a regulated event during conditions of synaptic plasticity in the brain. Point mutation analysis identified several residues within the transmembrane domain that play a critical role in the positioning of cleavage sites by ectodomain sheddases. Nectin-3, which forms hetero-trans-dimers with nectin-1, also undergoes intramembrane cleavage mediated by PS1/γ-secretase, suggesting that PS1/γ-secreatse activity regulates synapse formation and remodeling by nectin processing.
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Affiliation(s)
- Jinsook Kim
- Department of Neuroscience, Georgetown University Medical Center, NW, Washington, District of Columbia, USA
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27
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Kurita S, Ogita H, Takai Y. Cooperative role of nectin-nectin and nectin-afadin interactions in formation of nectin-based cell-cell adhesion. J Biol Chem 2011; 286:36297-303. [PMID: 21880730 DOI: 10.1074/jbc.m111.261768] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The nectin cell adhesion molecules interact in trans with each other through their extracellular regions and with afadin through their cytoplasmic tails, forming adherens junctions in cooperation with cadherins. In a single cell, Necl-5 (nectin-like molecule-5) localizes at the leading edge and regulates directional cell movement in response to a chemoattractant. In such a single cell, afadin also localizes at the leading edge without interacting with nectins or Necl-5. It remains unknown how the nectin-nectin and nectin-afadin interactions are initiated when moving cells contact each other to initiate the formation of adherens junctions. We show here that the Necl-5-nectin interaction induced by cell-cell contact enhances the nectin-afadin interaction. This interaction then enhances the nectin-nectin interaction, which further enhances the nectin-afadin interaction in a positive feedback manner. Thus, the Necl-5-nectin, nectin-nectin, and nectin-afadin interactions cooperatively increase the clustering of the nectin-afadin complex at the cell-cell contact sites, promoting the formation of the nectin-based cell-cell adhesion.
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Affiliation(s)
- Souichi Kurita
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan
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28
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Sacco E, Metalli D, Spinelli M, Manzoni R, Samalikova M, Grandori R, Morrione A, Traversa S, Alberghina L, Vanoni M. Novel RasGRF1-derived Tat-fused peptides inhibiting Ras-dependent proliferation and migration in mouse and human cancer cells. Biotechnol Adv 2011; 30:233-43. [PMID: 21620943 DOI: 10.1016/j.biotechadv.2011.05.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 05/09/2011] [Indexed: 10/18/2022]
Abstract
Mutations of RAS genes are critical events in the pathogenesis of different human tumors and Ras proteins represent a major clinical target for the development of specific inhibitors to use as anticancer agents. Here we present RasGRF1-derived peptides displaying both in vitro and in vivo Ras inhibitory properties. These peptides were designed on the basis of the down-sizing of dominant negative full-length RasGRF1 mutants. The over-expression of these peptides can revert the phenotype of K-RAS transformed mouse fibroblasts to wild type, as monitored by several independent biological readouts, including Ras-GTP intracellular levels, ERK activity, morphology, proliferative potential and anchorage independent growth. Fusion of the RasGRF1-derived peptides with the Tat protein transduction domain allows their uptake into mammalian cells. Chemically synthesized Tat-fused peptides, reduced to as small as 30 residues on the basis of structural constraints, retain Ras inhibitory activity. These small peptides interfere in vitro with the GEF catalyzed nucleotide dissociation and exchange on Ras, reduce cell proliferation of K-RAS transformed mouse fibroblasts, and strongly reduce Ras-dependent IGF-I-induced migration and invasion of human bladder cancer cells. These results support the use of RasGRF1-derived peptides as model compounds for the development of Ras inhibitory anticancer agents.
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Affiliation(s)
- Elena Sacco
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy.
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Ulluwishewa D, Anderson RC, McNabb WC, Moughan PJ, Wells JM, Roy NC. Regulation of tight junction permeability by intestinal bacteria and dietary components. J Nutr 2011; 141:769-76. [PMID: 21430248 DOI: 10.3945/jn.110.135657] [Citation(s) in RCA: 790] [Impact Index Per Article: 60.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The human intestinal epithelium is formed by a single layer of epithelial cells that separates the intestinal lumen from the underlying lamina propria. The space between these cells is sealed by tight junctions (TJ), which regulate the permeability of the intestinal barrier. TJ are complex protein structures comprised of transmembrane proteins, which interact with the actin cytoskeleton via plaque proteins. Signaling pathways involved in the assembly, disassembly, and maintenance of TJ are controlled by a number of signaling molecules, such as protein kinase C, mitogen-activated protein kinases, myosin light chain kinase, and Rho GTPases. The intestinal barrier is a complex environment exposed to many dietary components and many commensal bacteria. Studies have shown that the intestinal bacteria target various intracellular pathways, change the expression and distribution of TJ proteins, and thereby regulate intestinal barrier function. The presence of some commensal and probiotic strains leads to an increase in TJ proteins at the cell boundaries and in some cases prevents or reverses the adverse effects of pathogens. Various dietary components are also known to regulate epithelial permeability by modifying expression and localization of TJ proteins.
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Affiliation(s)
- Dulantha Ulluwishewa
- Food Nutrition Genomics Team, Agri-Foods and Health Section, Palmerston North 4442, New Zealand
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30
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Fournier G, Cabaud O, Josselin E, Chaix A, Adélaïde J, Isnardon D, Restouin A, Castellano R, Dubreuil P, Chaffanet M, Birnbaum D, Lopez M. Loss of AF6/afadin, a marker of poor outcome in breast cancer, induces cell migration, invasiveness and tumor growth. Oncogene 2011; 30:3862-74. [DOI: 10.1038/onc.2011.106] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Meierhofer T, Rosnizeck IC, Graf T, Reiss K, König B, Kalbitzer HR, Spoerner M. Cu2+-cyclen as probe to identify conformational states in guanine nucleotide binding proteins. J Am Chem Soc 2011; 133:2048-51. [PMID: 21268614 DOI: 10.1021/ja108779j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
(31)P NMR spectroscopy is a suitable method for identifying conformational states in the active site of guanine nucleotide binding proteins detecting the nucleotide placed there. Because there is no labeling necessary, this method is gaining increasing interest. By (31)P NMR spectroscopy two major conformational states, namely state 1(T) and state 2(T), can be detected in active Ras protein characterized by different chemical shifts. Depending on the conformational state Ras shows clearly different physiological properties. Meanwhile analogous conformational equilibria could also be shown for other members of the Ras superfamily. It is often difficult to determine the conformational states of the proteins on the basis of chemical shift alone; therefore, direct detection would be a great advantage. With the use of Cu(2+)-cyclen which selectively interacts only with one of the major conformational states (state 1) one has a probe to distinguish between the two states, because only proteins existing in conformational state 1 interact with the Cu(2+)-cyclen at low millimolar concentrations. The suitability was proven using Ras(wt) and Ras mutants, Ras complexed with GTP, GppNHp, or GTPγS, as well as two further members of the Ras superfamily namely Arf1 and Ran.
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Affiliation(s)
- Tanja Meierhofer
- University of Regensburg, Institute of Physical Biochemistry and Biophysics, Universitätsstrasse 31, D-93053 Regensburg, Germany
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Rikitake Y, Takai Y. Directional Cell Migration. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 287:97-143. [DOI: 10.1016/b978-0-12-386043-9.00003-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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33
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Spoerner M, Hozsa C, Poetzl JA, Reiss K, Ganser P, Geyer M, Kalbitzer HR. Conformational states of human rat sarcoma (Ras) protein complexed with its natural ligand GTP and their role for effector interaction and GTP hydrolysis. J Biol Chem 2010; 285:39768-78. [PMID: 20937837 DOI: 10.1074/jbc.m110.145235] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The guanine nucleotide-binding protein Ras exists in solution in two different conformational states when complexed with different GTP analogs such as GppNHp or GppCH(2)p. State 1 has only a very low affinity to effectors and seems to be recognized by guanine nucleotide exchange factors, whereas state 2 represents the high affinity effector binding state. In this work we investigate Ras in complex with the physiological nucleoside triphosphate GTP. By polarization transfer (31)P NMR experiments and effector binding studies we show that Ras(wt)·Mg(2+)·GTP also exists in a dynamical equilibrium between the weakly populated conformational state 1 and the dominant state 2. At 278 K the equilibrium constant between state 1 and state 2 of C-terminal truncated wild-type Ras(1-166) K(12) is 11.3. K(12) of full-length Ras is >20, suggesting that the C terminus may also have a regulatory effect on the conformational equilibrium. The exchange rate (k(ex)) for Ras(wt)·Mg(2+)·GTP is 7 s(-1) and thus 18-fold lower compared with that found for the Ras·GppNHp complex. The intrinsic GTPase activity substantially increases after effector binding for the switch I mutants Ras(Y32F), (Y32R), (Y32W), (Y32C/C118S), (T35S), and the switch II mutant Ras(G60A) by stabilizing state 2, with the largest effect on Ras(Y32R) with a 13-fold increase compared with wild-type. In contrast, no acceleration was observed in Ras(T35A). Thus Ras in conformational state 2 has a higher affinity to effectors as well as a higher GTPase activity. These observations can be used to explain why many mutants have a low GTPase activity but are not oncogenic.
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Affiliation(s)
- Michael Spoerner
- Universität Regensburg, Institut für Biophysik und Physikalische Biochemie, Universitätsstrasse 31, 93053 Regensburg, Germany
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Rosnizeck IC, Graf T, Spoerner M, Tränkle J, Filchtinski D, Herrmann C, Gremer L, Vetter IR, Wittinghofer A, König B, Kalbitzer HR. Stabilizing a weak binding state for effectors in the human ras protein by cyclen complexes. Angew Chem Int Ed Engl 2010; 49:3830-3. [PMID: 20401883 DOI: 10.1002/anie.200907002] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Ina C Rosnizeck
- Universität Regensburg, Institut für Biophysik und Physikalische Biochemie, Universitätsstrasse 31, 93053 Regensburg, Germany
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Shima F, Ijiri Y, Muraoka S, Liao J, Ye M, Araki M, Matsumoto K, Yamamoto N, Sugimoto T, Yoshikawa Y, Kumasaka T, Yamamoto M, Tamura A, Kataoka T. Structural basis for conformational dynamics of GTP-bound Ras protein. J Biol Chem 2010; 285:22696-705. [PMID: 20479006 PMCID: PMC2903345 DOI: 10.1074/jbc.m110.125161] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 04/28/2010] [Indexed: 12/31/2022] Open
Abstract
Ras family small GTPases assume two interconverting conformations, "inactive" state 1 and "active" state 2, in their GTP-bound forms. Here, to clarify the mechanism of state transition, we have carried out x-ray crystal structure analyses of a series of mutant H-Ras and M-Ras in complex with guanosine 5'-(beta,gamma-imido)triphosphate (GppNHp), representing various intermediate states of the transition. Crystallization of H-RasT35S-GppNHp enables us to solve the first complete tertiary structure of H-Ras state 1 possessing two surface pockets unseen in the state 2 or H-Ras-GDP structure. Moreover, determination of the two distinct crystal structures of H-RasT35S-GppNHp, showing prominent polysterism in the switch I and switch II regions, reveals a pivotal role of the guanine nucleotide-mediated interaction between the two switch regions and its rearrangement by a nucleotide positional change in the state 2 to state 1 transition. Furthermore, the (31)P NMR spectra and crystal structures of the GppNHp-bound forms of M-Ras mutants, carrying various H-Ras-type amino acid substitutions, also reveal the existence of a surface pocket in state 1 and support a similar mechanism based on the nucleotide-mediated interaction and its rearrangement in the state 1 to state 2 transition. Intriguingly, the conformational changes accompanying the state transition mimic those that occurred upon GDP/GTP exchange, indicating a common mechanistic basis inherent in the high flexibility of the switch regions. Collectively, these results clarify the structural features distinguishing the two states and provide new insights into the molecular basis for the state transition of Ras protein.
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Affiliation(s)
- Fumi Shima
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Yuichi Ijiri
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Shin Muraoka
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
- the RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Jingling Liao
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Min Ye
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Mitsugu Araki
- the Department of Chemistry, Kobe University Graduate School of Science, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Kousuke Matsumoto
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Naoki Yamamoto
- the Department of Chemistry, Kobe University Graduate School of Science, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Takeshi Sugimoto
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Yoko Yoshikawa
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | - Takashi Kumasaka
- the Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan, and
| | - Masaki Yamamoto
- the RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Atsuo Tamura
- the Department of Chemistry, Kobe University Graduate School of Science, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Tohru Kataoka
- From the Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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Tawa H, Rikitake Y, Takahashi M, Amano H, Miyata M, Satomi-Kobayashi S, Kinugasa M, Nagamatsu Y, Majima T, Ogita H, Miyoshi J, Hirata KI, Takai Y. Role of Afadin in Vascular Endothelial Growth Factor– and Sphingosine 1-Phosphate–Induced Angiogenesis. Circ Res 2010; 106:1731-42. [DOI: 10.1161/circresaha.110.216747] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale
:
Angiogenesis contributes to physiological and pathological conditions, including atherosclerosis. The Rap1 small G protein regulates vascular integrity and angiogenesis. However, little is known about the effectors of Rap1 involved in angiogenesis. It is not known whether afadin, an adherens junction protein that connects immunoglobulin-like adhesion molecule nectins to the actin cytoskeleton and binds activated Rap1, plays a role in angiogenesis.
Objective
:
We investigated the role of endothelial afadin in angiogenesis and attempted to clarify the underlying molecular mechanism.
Methods and Results
:
Treatment of human umbilical vein endothelial cells (HUVECs) with vascular endothelial growth factor (VEGF) and sphingosine 1-phosphate (S1P) induced the activation of Rap1. Activated Rap1 regulated intracellular localization of afadin. Knockdown of Rap1 or afadin by small interfering RNA inhibited the VEGF- and S1P-induced capillary-like network formation, migration, and proliferation, and increased the serum deprivation-induced apoptosis of HUVECs. Knockdown of Rap1 or afadin decreased the accumulation of adherens and tight junction proteins to the cell–cell contact sites. Rap1 regulated the interaction between afadin and phosphatidylinositol 3-kinase (PI3K), recruitment of the afadin–PI3K complex to the leading edge, and the activation of Akt, indicating the involvement of Rap1 and afadin in the PI3K–Akt signaling pathway. Binding of afadin to Rap1 regulated the activity of Rap1 in a positive-feedback manner. In vivo, conditional deletion of afadin in mouse vascular endothelium using a Cre-loxP system impaired the VEGF- and S1P-induced angiogenesis.
Conclusions
:
These results demonstrate a novel molecular mechanism by which Rap1 and afadin regulate the VEGF- and S1P-induced angiogenesis.
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Affiliation(s)
- Hideto Tawa
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Yoshiyuki Rikitake
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Motonori Takahashi
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Hisayuki Amano
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Muneaki Miyata
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Seimi Satomi-Kobayashi
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Mitsuo Kinugasa
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Yuichi Nagamatsu
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Takashi Majima
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Hisakazu Ogita
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Jun Miyoshi
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Ken-ichi Hirata
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
| | - Yoshimi Takai
- From the Divisions of Molecular and Cellular Biology (H.T., Y.R., M.T., H.A., M.M., S.S.-K., M.K., Y.N., T.M., H.O., Y.T.) and Signal Transduction (Y.R., M.M.), Department of Biochemistry and Molecular Biology; and Division of Cardiovascular Medicine (H.T., Y.R., M.T., S.S.-K., M.K., K.-i.H.), Department of Internal Medicine, Kobe University Graduate School of Medicine; and Department of Molecular Biology (T.M., J.M.), Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan
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Rosnizeck I, Graf T, Spoerner M, Tränkle J, Filchtinski D, Herrmann C, Gremer L, Vetter I, Wittinghofer A, König B, Kalbitzer H. Stabilisierung eines niederaffinen Zustands für Effektoren im menschlichen Ras-Protein durch Cyclenkomplexe. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200907002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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38
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Filchtinski D, Sharabi O, Rüppel A, Vetter IR, Herrmann C, Shifman JM. What makes Ras an efficient molecular switch: a computational, biophysical, and structural study of Ras-GDP interactions with mutants of Raf. J Mol Biol 2010; 399:422-35. [PMID: 20361980 DOI: 10.1016/j.jmb.2010.03.046] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2009] [Revised: 03/19/2010] [Accepted: 03/23/2010] [Indexed: 11/16/2022]
Abstract
Ras is a small GTP-binding protein that is an essential molecular switch for a wide variety of signaling pathways including the control of cell proliferation, cell cycle progression and apoptosis. In the GTP-bound state, Ras can interact with its effectors, triggering various signaling cascades in the cell. In the GDP-bound state, Ras looses its ability to bind to known effectors. The interaction of the GTP-bound Ras (Ras(GTP)) with its effectors has been studied intensively. However, very little is known about the much weaker interaction between the GDP-bound Ras (Ras(GDP)) and Ras effectors. We investigated the factors underlying the nucleotide-dependent differences in Ras interactions with one of its effectors, Raf kinase. Using computational protein design, we generated mutants of the Ras-binding domain of Raf kinase (Raf) that stabilize the complex with Ras(GDP). Most of our designed mutations narrow the gap between the affinity of Raf for Ras(GTP) and Ras(GDP), producing the desired shift in binding specificity towards Ras(GDP). A combination of our best designed mutation, N71R, with another mutation, A85K, yielded a Raf mutant with a 100-fold improvement in affinity towards Ras(GDP). The Raf A85K and Raf N71R/A85K mutants were used to obtain the first high-resolution structures of Ras(GDP) bound to its effector. Surprisingly, these structures reveal that the loop on Ras previously termed the switch I region in the Ras(GDP).Raf mutant complex is found in a conformation similar to that of Ras(GTP) and not Ras(GDP). Moreover, the structures indicate an increased mobility of the switch I region. This greater flexibility compared to the same loop in Ras(GTP) is likely to explain the natural low affinity of Raf and other Ras effectors to Ras(GDP). Our findings demonstrate that an accurate balance between a rigid, high-affinity conformation and conformational flexibility is required to create an efficient and stringent molecular switch.
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Affiliation(s)
- Daniel Filchtinski
- Physikalische Chemie I, Fakultät für Chemie und Biochemie, Ruhr-Universität-Bochum, Universitätstr. 150, 44780 Bochum, Germany
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39
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The dual role of zonula occludens (ZO) proteins. J Biomed Biotechnol 2010; 2010:402593. [PMID: 20224657 PMCID: PMC2836178 DOI: 10.1155/2010/402593] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Accepted: 01/06/2010] [Indexed: 02/07/2023] Open
Abstract
ZO (zonula occludens) proteins are scaffolding proteins providing the structural basis for the assembly of multiprotein complexes at the cytoplasmic surface of intercellular junctions. In addition, they provide a link between the integral membrane proteins and the filamentous cytoskeleton. ZO proteins belong to the large family of membrane-associated guanylate kinase (MAGUK)-like proteins comprising a number of subfamilies based on domain content and sequence similarity. Besides their structural function at cell-cell contacts, ZO proteins appear to participate in the regulation of cell growth and proliferation. Detailed molecular studies have shown that ZO proteins exhibit conserved functional nuclear localization and nuclear export motifs within their amino acid sequence. Further, ZO proteins interact with dual residency proteins localizing to the plasma membrane and the nucleus. Although the nuclear targeting of ZO proteins has well been described, many questions concerning the biological significance of this process have remained open. This review focuses on the dual role of ZO proteins, being indispensable structural components at the junctional site and functioning in signal transduction pathways related to gene expression and cell behavior.
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40
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Miyata M, Ogita H, Komura H, Nakata S, Okamoto R, Ozaki M, Majima T, Matsuzawa N, Kawano S, Minami A, Waseda M, Fujita N, Mizutani K, Rikitake Y, Takai Y. Localization of nectin-free afadin at the leading edge and its involvement in directional cell movement induced by platelet-derived growth factor. J Cell Sci 2009; 122:4319-29. [DOI: 10.1242/jcs.048439] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Afadin is an actin-filament-binding protein that binds to nectin, an immunoglobulin-like cell-cell adhesion molecule, and plays an important role in the formation of adherens junctions. Here, we show that afadin, which did not bind to nectin and was localized at the leading edge of moving cells, has another role: enhancement of the directional, but not random, cell movement. When NIH3T3 cells were stimulated with platelet-derived growth factor (PDGF), afadin colocalized with PDGF receptor, αvβ3 integrin and nectin-like molecule-5 at the leading edge and facilitated the formation of leading-edge structures and directional cell movement in the direction of PDGF stimulation. However, these phenotypes were markedly perturbed by knockdown of afadin, and were dependent on the binding of afadin to active Rap1. Binding of Rap1 to afadin was necessary for the recruitment of afadin and the tyrosine phosphatase SHP-2 to the leading edge. SHP-2 was previously reported to tightly regulate the activation of PDGF receptor and its downstream signaling pathway for the formation of the leading edge. These results indicate that afadin has a novel role in PDGF-induced directional cell movement, presumably in cooperation with active Rap1 and SHP-2.
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Affiliation(s)
- Muneaki Miyata
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Hisakazu Ogita
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Hitomi Komura
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Shinsuke Nakata
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine, Osaka 565-0871 Japan
| | - Ryoko Okamoto
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine, Osaka 565-0871 Japan
| | - Misa Ozaki
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Takashi Majima
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine, Osaka 565-0871 Japan
| | - Naomi Matsuzawa
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Satoshi Kawano
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Akihiro Minami
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Masumi Waseda
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Naoyuki Fujita
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine, Osaka 565-0871 Japan
| | - Kiyohito Mizutani
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Yoshiyuki Rikitake
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Yoshimi Takai
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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Kiel C, Filchtinski D, Spoerner M, Schreiber G, Kalbitzer HR, Herrmann C. Improved binding of raf to Ras.GDP is correlated with biological activity. J Biol Chem 2009; 284:31893-902. [PMID: 19776012 DOI: 10.1074/jbc.m109.031153] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The GTP-binding protein Ras plays a central role in the regulation of various cellular processes, acting as a molecular switch that triggers signaling cascades. Only Ras bound to GTP is able to interact strongly with effector proteins like Raf kinase, phosphatidylinositol 3-kinase, and RalGDS, whereas in the GDP-bound state, the stability of the complex is strongly decreased, and signaling is interrupted. To determine whether this process is only controlled by the stability of the complex, we used computer-aided protein design to improve the interaction between Ras and effector. We challenged the Ras.Raf complex in this study because Raf among all effectors shows the highest Ras affinity and the fastest association kinetics. The proposed mutations were characterized as to their changes in dynamics and binding strength. We demonstrate that Ras-Raf interaction can only be improved at the cost of a loss in specificity of Ras.GTP versus Ras.GDP. As shown by NMR spectroscopy, the Raf mutation A85K leads to a shift of Ras switch I in the GTP-bound as well as in the GDP-bound state, thereby increasing the complex stability. In a luciferase-based reporter gene assay, Raf A85K is associated with higher signaling activity, which appears to be a mere matter of Ras-Raf affinity.
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Affiliation(s)
- Christina Kiel
- Abteilung Strukturelle Biologie, Max-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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Sawyer JK, Harris NJ, Slep KC, Gaul U, Peifer M. The Drosophila afadin homologue Canoe regulates linkage of the actin cytoskeleton to adherens junctions during apical constriction. ACTA ACUST UNITED AC 2009; 186:57-73. [PMID: 19596848 PMCID: PMC2712996 DOI: 10.1083/jcb.200904001] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cadherin-based adherens junctions (AJs) mediate cell adhesion and regulate cell shape change. The nectin–afadin complex also localizes to AJs and links to the cytoskeleton. Mammalian afadin has been suggested to be essential for adhesion and polarity establishment, but its mechanism of action is unclear. In contrast, Drosophila melanogaster’s afadin homologue Canoe (Cno) has suggested roles in signal transduction during morphogenesis. We completely removed Cno from embryos, testing these hypotheses. Surprisingly, Cno is not essential for AJ assembly or for AJ maintenance in many tissues. However, morphogenesis is impaired from the start. Apical constriction of mesodermal cells initiates but is not completed. The actomyosin cytoskeleton disconnects from AJs, uncoupling actomyosin constriction and cell shape change. Cno has multiple direct interactions with AJ proteins, but is not a core part of the cadherin–catenin complex. Instead, Cno localizes to AJs by a Rap1- and actin-dependent mechanism. These data suggest that Cno regulates linkage between AJs and the actin cytoskeleton during morphogenesis.
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Affiliation(s)
- Jessica K Sawyer
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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43
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Severson EA, Parkos CA. Structural determinants of Junctional Adhesion Molecule A (JAM-A) function and mechanisms of intracellular signaling. Curr Opin Cell Biol 2009; 21:701-7. [PMID: 19608396 DOI: 10.1016/j.ceb.2009.06.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 06/01/2009] [Accepted: 06/17/2009] [Indexed: 10/20/2022]
Abstract
Junctional Adhesion Molecule A (JAM-A) is a multifunctional cell surface protein that has multiple evolutionarily conserved structural features. There is now conclusive evidence that discrete structural elements on JAM-A mediate intracellular signaling events that alter cell migration and paracellular permeability. Specifically, self-dimerization between extracellular Ig-like loops and close apposition of PDZ-dependent, JAM-A-associated intracellular scaffold proteins such as Afadin and guanine-nucleotide exchange factors mediate activation of Rap1 and modulation of epithelial cell migration by effects on beta1 integrin. While the same JAM-A structural features also modulate migration of other cell types and paracellular permeability in epithelia/endothelia, additional signaling proteins/mechanisms are probably involved. Recent insights into JAM-A outside-in signaling events that regulate these cellular functions are discussed.
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Affiliation(s)
- Eric A Severson
- Department of Pathology and Laboratory Medicine, Emory University, 615 Michael Street, Atlanta, GA 30322, USA
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Miyata M, Rikitake Y, Takahashi M, Nagamatsu Y, Yamauchi Y, Ogita H, Hirata KI, Takai Y. Regulation by afadin of cyclical activation and inactivation of Rap1, Rac1, and RhoA small G proteins at leading edges of moving NIH3T3 cells. J Biol Chem 2009; 284:24595-609. [PMID: 19589776 DOI: 10.1074/jbc.m109.016436] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyclical activation and inactivation of Rho family small G proteins, such as Rho, Rac, and Cdc42, are needed for moving cells to form leading edge structures in response to chemoattractants. However, the mechanisms underlying the dynamic regulation of their activities are not fully understood. We recently showed that another small G protein, Rap1, plays a crucial role in the platelet-derived growth factor (PDGF)-induced formation of leading edge structures and activation of Rac1 in NIH3T3 cells. We showed here that knockdown of afadin, an actin-binding protein, in NIH3T3 cells resulted in a failure to develop leading edge structures in association with an impairment of the activation of Rap1 and Rac1 and inactivation of RhoA in response to PDGF. Overexpression of a constitutively active mutant of Rap1 (Rap1-CA) and knockdown of SPA-1, a Rap1 GTPase-activating protein that was negatively regulated by afadin by virtue of binding to it, in afadin-knockdown NIH3T3 cells restored the formation of leading edge structures and the reduction of the PDGF-induced activation of Rac1 and inactivation of RhoA, suggesting that the inactivation of Rap1 by SPA-1 is responsible for inhibition of the formation of leading edge structures. The effect of Rap1-CA on the restoration of the formation of leading edge structures and RhoA inactivation was diminished by additional knockdown of ARAP1, a Rap-activated Rho GAP, which localized at the leading edges of moving NIH3T3 cells. These results indicate that afadin regulates the cyclical activation and inactivation of Rap1, Rac1, and RhoA through SPA-1 and ARAP1.
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Affiliation(s)
- Muneaki Miyata
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
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O'Keefe DD, Gonzalez-Niño E, Burnett M, Dylla L, Lambeth SM, Licon E, Amesoli C, Edgar BA, Curtiss J. Rap1 maintains adhesion between cells to affect Egfr signaling and planar cell polarity in Drosophila. Dev Biol 2009; 333:143-60. [PMID: 19576205 DOI: 10.1016/j.ydbio.2009.06.032] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 06/06/2009] [Accepted: 06/23/2009] [Indexed: 11/19/2022]
Abstract
The small GTPase Rap1 affects cell adhesion and cell motility in numerous developmental contexts. Loss of Rap1 in the Drosophila wing epithelium disrupts adherens junction localization, causing mutant cells to disperse, and dramatically alters epithelial cell shape. While the adhesive consequences of Rap1 inactivation have been well described in this system, the effects on cell signaling, cell fate specification, and tissue differentiation are not known. Here we demonstrate that Egfr-dependent cell types are lost from Rap1 mutant tissue as an indirect consequence of DE-cadherin mislocalization. Cells lacking Rap1 in the developing wing and eye are capable of responding to an Egfr signal, indicating that Rap1 is not required for Egfr/Ras/MAPK signal transduction. Instead, Rap1 regulates adhesive contacts necessary for maintenance of Egfr signaling between cells, and differentiation of wing veins and photoreceptors. Rap1 is also necessary for planar cell polarity in these tissues. Wing hair alignment and ommatidial rotation, functional readouts of planar cell polarity in the wing and eye respectively, are both affected in Rap1 mutant tissue. Finally, we show that Rap1 acts through the effector Canoe to regulate these developmental processes.
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Affiliation(s)
- David D O'Keefe
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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Severson EA, Lee WY, Capaldo CT, Nusrat A, Parkos CA. Junctional adhesion molecule A interacts with Afadin and PDZ-GEF2 to activate Rap1A, regulate beta1 integrin levels, and enhance cell migration. Mol Biol Cell 2009; 20:1916-25. [PMID: 19176753 DOI: 10.1091/mbc.e08-10-1014] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Junctional adhesion molecule-A (JAM-A) is a transmembrane tight junction protein that has been shown to regulate barrier function and cell migration through incompletely understood mechanisms. We have previously demonstrated that JAM-A regulates cell migration by dimerization of the membrane-distal immunoglobulin-like loop and a C-terminal postsynaptic density 95/disc-large/zona occludens (PDZ) binding motif. Disruption of dimerization resulted in decreased epithelial cell migration secondary to diminished levels of beta1 integrin and active Rap1. Here, we report that JAM-A is physically and functionally associated with the PDZ domain-containing molecules Afadin and PDZ-guanine nucleotide exchange factor (GEF) 2, but not zonula occludens (ZO)-1, in epithelial cells, and these interactions mediate outside-in signaling events. Both Afadin and PDZ-GEF2 colocalized and coimmunoprecipitated with JAM-A. Furthermore, association of PDZ-GEF2 with Afadin was dependent on the expression of JAM-A. Loss of JAM-A, Afadin, or PDZ-GEF2, but not ZO-1 or PDZ-GEF1, similarly decreased cellular levels of activated Rap1, beta1 integrin protein, and epithelial cell migration. The functional effects observed were secondary to decreased levels of Rap1A because knockdown of Rap1A, but not Rap1B, resulted in decreased beta1 integrin levels and reduced cell migration. These findings suggest that JAM-A dimerization facilitates formation of a complex with Afadin and PDZ-GEF2 that activates Rap1A, which regulates beta1 integrin levels and cell migration.
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Affiliation(s)
- Eric A Severson
- Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
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Kiel C, Aydin D, Serrano L. Association rate constants of ras-effector interactions are evolutionarily conserved. PLoS Comput Biol 2008; 4:e1000245. [PMID: 19096503 PMCID: PMC2588540 DOI: 10.1371/journal.pcbi.1000245] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 11/06/2008] [Indexed: 12/31/2022] Open
Abstract
Evolutionary conservation of protein interaction properties has been shown to be a valuable indication for functional importance. Here we use homology interface modeling of 10 Ras-effector complexes by selecting ortholog proteins from 12 organisms representing the major eukaryotic branches, except plants. We find that with increasing divergence time the sequence similarity decreases with respect to the human protein, but the affinities and association rate constants are conserved as predicted by the protein design algorithm, FoldX. In parallel we have done computer simulations on a minimal network based on Ras-effector interactions, and our results indicate that in the absence of negative feedback, changes in kinetics that result in similar binding constants have strong consequences on network behavior. This, together with the previous results, suggests an important biological role, not only for equilibrium binding constants but also for kinetics in signaling processes involving Ras-effector interactions. Our findings are important to take into consideration in system biology approaches and simulations of biological networks. Cellular signal transductions processes are based on protein interactions. Proteins can either associate transiently with each other or form stable complexes, and the strength of the interaction is described by the affinity (the affinity is the ratio between the rate of dissociation and association). Protein complexes with similar affinities can bind and dissociate with different rates, and these rates describe the kinetic properties of protein binding. These kinetic rates are important for signaling; however, to what extent individual changes in such rate constants are biologically important or whether the affinity is more crucial might be different in different signaling processes. In this study we analyze whether association rates are conserved during evolution, because evolutionary conservation of protein biochemical properties is usually a valuable indication of its importance. We analyzed the binding of Ras proteins to effector domains, which are central proteins in many signal transduction pathways, in different organisms. On the basis of homology modeling and energy calculations we find that association rates are conserved, although the sequence similarity decreases compared to the human protein. Our finding should encourage further analysis of the importance of kinetics for cellular signal transduction.
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Affiliation(s)
- Christina Kiel
- EMBL-CRG Systems Biology Unit, Centre de Regulacio Genomica, Barcelona, Spain.
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Takai Y, Ikeda W, Ogita H, Rikitake Y. The immunoglobulin-like cell adhesion molecule nectin and its associated protein afadin. Annu Rev Cell Dev Biol 2008; 24:309-42. [PMID: 18593353 DOI: 10.1146/annurev.cellbio.24.110707.175339] [Citation(s) in RCA: 279] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Nectins are immunoglobulin-like cell adhesion molecules (CAMs) that compose a family of four members. Nectins homophilically and heterophilically interact in trans with each other to form cell-cell adhesions. In addition, they heterophilically interact in trans with other immunoglobulin-like CAMs. Nectins bind afadin, an actin filament (F-actin)-binding protein, at its cytoplasmic tail and associate with the actin cytoskeleton. Afadin additionally serves as an adaptor protein by further binding many scaffolding proteins and F-actin-binding proteins and contributes to the association of nectins with other cell-cell adhesion and intracellular signaling systems. Nectins and afadin play roles in the formation of a variety of cell-cell junctions cooperatively with, or independently of, cadherins. Cooperation between nectins and cadherins is required for the formation of cell-cell junctions; cadherins alone are not sufficient. Additionally, nectins regulate many other cellular activities (such as movement, proliferation, survival, differentiation, polarization, and the entry of viruses) in cooperation with other CAMs and cell surface membrane receptors.
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Affiliation(s)
- Yoshimi Takai
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
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Filchtinski D, Bee C, Savopol T, Engelhard M, Becker CFW, Herrmann C. Probing Ras Effector Interactions on Nanoparticle Supported Lipid Bilayers. Bioconjug Chem 2008; 19:1938-44. [DOI: 10.1021/bc800099p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel Filchtinski
- Physikalische Chemie 1, Ruhr-Universität-Bochum, Fakultät für Chemie and Biochemie, Universitätsstr. 150, 44780 Bochum, Germany, and Max-Planck Institut für Molekulare Physiologie, Abt. Physikalische Biochemie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Christine Bee
- Physikalische Chemie 1, Ruhr-Universität-Bochum, Fakultät für Chemie and Biochemie, Universitätsstr. 150, 44780 Bochum, Germany, and Max-Planck Institut für Molekulare Physiologie, Abt. Physikalische Biochemie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Tudor Savopol
- Physikalische Chemie 1, Ruhr-Universität-Bochum, Fakultät für Chemie and Biochemie, Universitätsstr. 150, 44780 Bochum, Germany, and Max-Planck Institut für Molekulare Physiologie, Abt. Physikalische Biochemie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Martin Engelhard
- Physikalische Chemie 1, Ruhr-Universität-Bochum, Fakultät für Chemie and Biochemie, Universitätsstr. 150, 44780 Bochum, Germany, and Max-Planck Institut für Molekulare Physiologie, Abt. Physikalische Biochemie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Christian F. W. Becker
- Physikalische Chemie 1, Ruhr-Universität-Bochum, Fakultät für Chemie and Biochemie, Universitätsstr. 150, 44780 Bochum, Germany, and Max-Planck Institut für Molekulare Physiologie, Abt. Physikalische Biochemie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Christian Herrmann
- Physikalische Chemie 1, Ruhr-Universität-Bochum, Fakultät für Chemie and Biochemie, Universitätsstr. 150, 44780 Bochum, Germany, and Max-Planck Institut für Molekulare Physiologie, Abt. Physikalische Biochemie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
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Lim ST, Lim KC, Giuliano RE, Federoff HJ. Temporal and spatial localization of nectin-1 and l-afadin during synaptogenesis in hippocampal neurons. J Comp Neurol 2008; 507:1228-44. [PMID: 18181141 DOI: 10.1002/cne.21608] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Nectins are cell adhesion molecules that, together with the intracellular binding partner afadin, mediate adhesion and signaling at a variety of intercellular junctions. In this work we studied the distribution of nectin-1 and afadin during hippocampal synapse formation using cultured primary hippocampal neurons. Nectin-1 and afadin cluster at developing synapses between hippocampal neurons. These nectin-afadin clusters uniformly colocalize with N-cadherin-catenin pairs, suggesting that formation of developing synapses involves participation of both bimolecular systems. Nectin-1 is initially expressed at excitatory and inhibitory synapses but is progressively lost at inhibitory synapses during their maturation. Treatment of neurons with actin depolymerizing agents disrupts the synaptically localized nectin-1 and afadin cluster at an early stage and elicits nectin-1 ectodomain shedding. These data indicate that the synaptic localization of nectin-1 and l-afadin are F-actin-dependent and that the shedding of nectin-1 is a mechanism contributing to synaptic plasticity.
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Affiliation(s)
- Seung T Lim
- Department of Neurology, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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