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Mozzarelli AM, Simanshu DK, Castel P. Functional and structural insights into RAS effector proteins. Mol Cell 2024; 84:2807-2821. [PMID: 39025071 PMCID: PMC11316660 DOI: 10.1016/j.molcel.2024.06.027] [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: 03/08/2024] [Revised: 06/24/2024] [Accepted: 06/25/2024] [Indexed: 07/20/2024]
Abstract
RAS proteins are conserved guanosine triphosphate (GTP) hydrolases (GTPases) that act as molecular binary switches and play vital roles in numerous cellular processes. Upon GTP binding, RAS GTPases adopt an active conformation and interact with specific proteins termed RAS effectors that contain a conserved ubiquitin-like domain, thereby facilitating downstream signaling. Over 50 effector proteins have been identified in the human proteome, and many have been studied as potential mediators of RAS-dependent signaling pathways. Biochemical and structural analyses have provided mechanistic insights into these effectors, and studies using model organisms have complemented our understanding of their role in physiology and disease. Yet, many critical aspects regarding the dynamics and biological function of RAS-effector complexes remain to be elucidated. In this review, we discuss the mechanisms and functions of known RAS effector proteins, provide structural perspectives on RAS-effector interactions, evaluate their significance in RAS-mediated signaling, and explore their potential as therapeutic targets.
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Affiliation(s)
- Alessandro M Mozzarelli
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA; Laura and Isaac Perlmutter NYU Cancer Center, NYU Langone Health, New York, NY, USA
| | - Dhirendra K Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA.
| | - Pau Castel
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA; Laura and Isaac Perlmutter NYU Cancer Center, NYU Langone Health, New York, NY, USA.
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2
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Ghosh N, Garg I, Srivastava S, Kumar B. Influence of integrins on thrombus formation: a road leading to the unravelling of DVT. Mol Cell Biochem 2021; 476:1489-1504. [PMID: 33398665 DOI: 10.1007/s11010-020-03961-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 10/23/2020] [Indexed: 01/18/2023]
Abstract
Integrins are a group of transmembrane glycoprotein receptors that are responsible for platelet activation through bidirectional signalling. These receptors have left their footprints in various cellular events and have intrigued many groups of scientists that have led to some significant discoveries. A lot of the recent understanding of haemostasis has been possible due to the integrins filling the gaps in between several cellular mechanism. Apart from this, other important functions carried out by integrins are growth and maturation of cardiomyocytes, mechano-transduction, and interaction with actin cytoskeleton. The signalling cascade for integrin activation involves certain intracellular interacting proteins, which initiates the step-by-step activation procedure through 'inside-out' signalling. The signalling cascade gets activated through 'outside-in' signalling with the involvement of agonists such as ADP, Fibronectin, Vitronectin, and so on. This is a crucial step for the downstream processes of platelet spreading, followed by aggregation, clot progression and finally thrombus formation. Researchers throughout the world have shown direct relation of integrins with CVD and cardiac remodelling. The present review aims to summarize the information available so far on the involvement of integrins in thrombosis and its relationship to DVT. This information could be a bedrock of hidden answers to several questions on pathogenesis of deep vein thrombosis.
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Affiliation(s)
- Nilanjana Ghosh
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi, 110054, India
| | - Iti Garg
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi, 110054, India.
| | - Swati Srivastava
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi, 110054, India
| | - Bhuvnesh Kumar
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi, 110054, India
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3
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Sauter RJ, Sauter M, Reis ES, Emschermann FN, Nording H, Ebenhöch S, Kraft P, Münzer P, Mauler M, Rheinlaender J, Madlung J, Edlich F, Schäffer TE, Meuth SG, Duerschmied D, Geisler T, Borst O, Gawaz M, Kleinschnitz C, Lambris JD, Langer HF. Functional Relevance of the Anaphylatoxin Receptor C3aR for Platelet Function and Arterial Thrombus Formation Marks an Intersection Point Between Innate Immunity and Thrombosis. Circulation 2019; 138:1720-1735. [PMID: 29802205 DOI: 10.1161/circulationaha.118.034600] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Platelets have distinct roles in the vascular system in that they are the major mediator of thrombosis, critical for restoration of tissue integrity, and players in vascular inflammatory conditions. In close spatiotemporal proximity, the complement system acts as the first line of defense against invading microorganisms and is a key mediator of inflammation. Whereas the fluid phase cross-talk between the complement and coagulation systems is well appreciated, the understanding of the pathophysiological implications of such interactions is still scant. METHODS We analyzed coexpression of the anaphylatoxin receptor C3aR with activated glycoprotein IIb/IIIa on platelets of 501 patients with coronary artery disease using flow cytometry; detected C3aR expression in human or murine specimen by polymerase chain reaction, immunofluorescence, Western blotting, or flow cytometry; and examined the importance of platelet C3aR by various in vitro platelet function tests, in vivo bleeding time, and intravital microscopy. The pathophysiological relevance of C3aR was scrutinized with the use of disease models of myocardial infarction and stroke. To approach underlying molecular mechanisms, we identified the platelet small GTPase Rap1b using nanoscale liquid chromatography coupled to tandem mass spectrometry. RESULTS We found a strong positive correlation of platelet complement C3aR expression with activated glycoprotein IIb/IIIa in patients with coronary artery disease and coexpression of C3aR with glycoprotein IIb/IIIa in thrombi obtained from patients with myocardial infarction. Our results demonstrate that the C3a/C3aR axis on platelets regulates distinct steps of thrombus formation such as platelet adhesion, spreading, and Ca2+ influx. Using C3aR-/- mice or C3-/- mice with reinjection of C3a, we uncovered that the complement activation fragment C3a regulates bleeding time after tail injury and thrombosis. Notably, C3aR-/- mice were less prone to experimental stroke and myocardial infarction. Furthermore, reconstitution of C3aR-/- mice with C3aR+/+ platelets and platelet depletion experiments demonstrated that the observed effects on thrombosis, myocardial infarction, and stroke were specifically caused by platelet C3aR. Mechanistically, C3aR-mediated signaling regulates the activation of Rap1b and thereby bleeding arrest after injury and in vivo thrombus formation. CONCLUSIONS Overall, our findings uncover a novel function of the anaphylatoxin C3a for platelet function and thrombus formation, highlighting a detrimental role of imbalanced complement activation in cardiovascular diseases.
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Affiliation(s)
- Reinhard J Sauter
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany.,Section for Cardioimmunology (R.J.S., M.S., F.N.E., H.N., S.E., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Manuela Sauter
- Section for Cardioimmunology (R.J.S., M.S., F.N.E., H.N., S.E., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Edimara S Reis
- Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia (E.S.R., J.D.L.)
| | - Frederic N Emschermann
- Section for Cardioimmunology (R.J.S., M.S., F.N.E., H.N., S.E., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Henry Nording
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany.,Section for Cardioimmunology (R.J.S., M.S., F.N.E., H.N., S.E., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Sonja Ebenhöch
- Section for Cardioimmunology (R.J.S., M.S., F.N.E., H.N., S.E., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Peter Kraft
- Department of Neurology, University of Würzburg, Germany (P.K.)
| | - Patrick Münzer
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Maximilian Mauler
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine (M.M., D.D.), University of Freiburg, Germany
| | - Johannes Rheinlaender
- Institute of Applied Physics (J.R., T.E.S.), Eberhard Karls-University Tübingen, Germany
| | - Johannes Madlung
- Proteom Center, Interfaculty Institute for Cell Biology (J.M.), Eberhard Karls-University Tübingen, Germany
| | - Frank Edlich
- Institute of Biochemistry (F.E.), University of Freiburg, Germany.,Institute for Biochemistry and Molecular Biology, University of Freiburg, Germany (F.E.).,BIOSS, Centre for Biological Signaling Studies, University of Freiburg, Germany (F.E.)
| | - Tilman E Schäffer
- Institute of Applied Physics (J.R., T.E.S.), Eberhard Karls-University Tübingen, Germany
| | - Sven G Meuth
- Department of Neurology, University of Münster, Germany (S.G.M.)
| | - Daniel Duerschmied
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine (M.M., D.D.), University of Freiburg, Germany
| | - Tobias Geisler
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Oliver Borst
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | - Meinrad Gawaz
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany
| | | | - John D Lambris
- Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia (E.S.R., J.D.L.)
| | - Harald F Langer
- Department of Cardiology and Cardiovascular Medicine, University Clinic (R.J.S., H.N., P.M., T.G., O.B., M.G., H.F.L.), Eberhard Karls-University Tübingen, Germany.,Section for Cardioimmunology (R.J.S., M.S., F.N.E., H.N., S.E., H.F.L.), Eberhard Karls-University Tübingen, Germany
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Williams TD, Paschke PI, Kay RR. Function of small GTPases in Dictyostelium macropinocytosis. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180150. [PMID: 30967009 PMCID: PMC6304742 DOI: 10.1098/rstb.2018.0150] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2018] [Indexed: 12/17/2022] Open
Abstract
Macropinocytosis-the large-scale, non-specific uptake of fluid by cells-is used by Dictyostelium discoideum amoebae to obtain nutrients. These cells form circular ruffles around regions of membrane defined by a patch of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) and the activated forms of the small G-proteins Ras and Rac. When this ruffle closes, a vesicle of the medium is delivered to the cell interior for further processing. It is accepted that PIP3 is required for efficient macropinocytosis. Here, we assess the roles of Ras and Rac in Dictyostelium macropinocytosis. Gain-of-function experiments show that macropinocytosis is stimulated by persistent Ras activation and genetic analysis suggests that RasG and RasS are the key Ras proteins involved. Among the activating guanine exchange factors (GEFs), GefF is implicated in macropinocytosis by an insertional mutant. The individual roles of Rho family proteins are little understood but activation of at least some may be independent of PIP3. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
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Affiliation(s)
| | | | - Robert R. Kay
- MRC-Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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5
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Saad IIF, Saha SB, Thomas G. The RAS subfamily Evolution - tracing evolution for its utmost exploitation. Bioinformation 2014; 10:293-8. [PMID: 24966537 PMCID: PMC4070039 DOI: 10.6026/97320630010293] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 05/04/2014] [Indexed: 11/23/2022] Open
Abstract
In the development of multicellularity, signaling proteins has played a very important role. Among them, RAS family is one of the most widely studied protein family. However, evolutionary analysis has been carried out mainly on super family level leaving sub family information in scanty. Thus, a subfamily evolutionary study on RAS evolutionary expansion is imperative as it will aid in better drug designing against dreadful diseases like Cancer and other developmental diseases. The present study was aimed to understand RAS evolution on both holistic as well as reductive level. All human RAS family genes and protein were subjected to BLAST tools to find orthologs and paralogs with different parameters followed by phylogenetic tree generation. Our results clearly showed that H-RAS is the most primitive RAS in higher eukaryotes and then diverged into other RAS family members due to different gene modification events. Furthermore, a site specific selection pressure analysis was carried out using SELECTON server which showed that H-RAS, M-RAS and N-RAS are evolving faster than K-RAS and R-RAS. Thus, the results ascertain a new ground to cancer biologists to exploit negatively selected K-RAS and R-RAS as potent drug targets in cancer therapeutics.
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Affiliation(s)
- Ismail IF Saad
- Department of Zoology, Faculty of Science, Omar Al Mukhtar University, Al Bayda, Libya
| | - Saurav B Saha
- Department of Computational Biology and Bioinformatics, JSBB, SHIATS, Allahabad - 211007, India
| | - George Thomas
- Department of Molecular and Cellular Engineering, JSBB, SHIATS, Allahabad - 211007, India
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6
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Uncovering a role for the tail of the Dictyostelium discoideum SadA protein in cell-substrate adhesion. EUKARYOTIC CELL 2011; 10:662-71. [PMID: 21441344 DOI: 10.1128/ec.00221-10] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesion deficiency, and overexpression of the SadA tail domain reduced adhesion in wild-type cells. We also show that SadA is closely associated with the actin cytoskeleton. Mutagenesis studies suggested that four serine residues in the tail, S924/S925 and S940/S941, may regulate association of SadA with the actin cytoskeleton. Glutathione S-transferase pull-down assays identified at least one likely interaction partner of the SadA tail, cortexillin I, a known actin bundling protein. Thus, our data demonstrate an important role for the carboxy-terminal cytoplasmic tail in SadA function and strongly suggest that a phosphorylation event in this tail regulates an interaction with cortexillin I. Based on our data, we propose a model for the function of SadA.
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7
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Newman SM, Tantasawat P, Steffens JC. Tomato polyphenol oxidase B is spatially and temporally regulated during development and in response to ethylene. Molecules 2011; 16:493-517. [PMID: 21224781 PMCID: PMC6259212 DOI: 10.3390/molecules16010493] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 01/07/2011] [Indexed: 01/14/2023] Open
Abstract
Plant polyphenol oxidases (PPOs) are ubiquitous plastid-localized enzymes. A precise analysis of PPO function in plants has been complicated by the presence of several family members with immunological cross reactivity. Previously we reported the isolation of genomic clones coding for the seven members of the tomato (Solanum lycopersicum) PPO family (A, A', B, C, D, E, and F). Here we report the complex spatial and temporal expression of one of the members, PPO B. The PPO B promoter was sequenced and subjected to homology analysis. Sequence similarities were found to nucleotide sequences of genes encoding enzymes/proteins active in the following systems: phenylpropanoid biosynthesis, signal transduction and responsiveness to hormones and stresses, fruit and seed proteins/enzymes, and photosynthesis. Chimeric gene fusions were constructed linking PPO B 5' flanking regions to the reporter gene, b-glucuronidase (GUS). The resultant transgenic plants were histochemically analyzed for GUS activity in various vegetative and reproductive tissues, and evaluated for PPO B responsiveness to ethylene induction. It was shown that PPO B expression was tissue specific, developmentally regulated, ethylene induced, and localized predominantly to mitotic or apoptotic tissues.
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Affiliation(s)
- Sally M. Newman
- Department of Plant Breeding and Genetics, 252 Emerson Hall, Cornell University, Ithaca, NY 14853, USA
| | - Piyada Tantasawat
- Department of Plant Breeding and Genetics, 252 Emerson Hall, Cornell University, Ithaca, NY 14853, USA
- Suranaree University of Technology, 111 University Ave., Muang District, Nakhon Ratchasima 30000, Thailand
| | - John C. Steffens
- Department of Plant Breeding and Genetics, 252 Emerson Hall, Cornell University, Ithaca, NY 14853, USA
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8
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Parkinson K, Bolourani P, Traynor D, Aldren NL, Kay RR, Weeks G, Thompson CRL. Regulation of Rap1 activity is required for differential adhesion, cell-type patterning and morphogenesis in Dictyostelium. J Cell Sci 2009; 122:335-44. [PMID: 19126673 PMCID: PMC2724730 DOI: 10.1242/jcs.036822] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2008] [Indexed: 12/19/2022] Open
Abstract
Regulated cell adhesion and motility have important roles during growth, development and tissue homeostasis. Consequently, great efforts have been made to identify genes that control these processes. One candidate is Rap1, as it has been implicated in the regulation of adhesion and motility in cell culture. To further study the role of Rap1 during multicellular development, we generated a mutant in a potential Rap1 GTPase activating protein (RapGAPB) in Dictyostelium. rapGAPB(-) cells have increased levels of active Rap1 compared with wild-type cells, indicating that RapGAPB regulates Rap1 activity. Furthermore, rapGAPB(-) cells exhibit hallmark phenotypes of other known mutants with hyperactivated Rap1, including increased substrate adhesion and abnormal F-actin distribution. However, unlike these other mutants, rapGAPB(-) cells do not exhibit impaired motility or chemotaxis, indicating that RapGAPB might only regulate specific roles of Rap1. Importantly, we also found that RapGAPB regulates Rap1 activity during multicellular development and is required for normal morphogenesis. First, streams of aggregating rapGAPB(-) cells break up as a result of decreased cell-cell adhesion. Second, rapGAPB(-) cells exhibit cell-autonomous defects in prestalk cell patterning. Using cell-type-specific markers, we demonstrate that RapGAPB is required for the correct sorting behaviour of different cell types. Finally, we show that inactivation of RapGAPB affects prestalk and prespore cell adhesion. We therefore propose that a possible mechanism for RapGAPB-regulated cell sorting is through differential adhesion.
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Affiliation(s)
- Katie Parkinson
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Manchester, UK
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9
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Chrzanowska-Wodnicka M, Smyth SS, Schoenwaelder SM, Fischer TH, White GC. Rap1b is required for normal platelet function and hemostasis in mice. J Clin Invest 2005; 115:680-7. [PMID: 15696195 PMCID: PMC546455 DOI: 10.1172/jci22973] [Citation(s) in RCA: 246] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Accepted: 12/14/2004] [Indexed: 11/17/2022] Open
Abstract
Rap1b, an abundant small GTPase in platelets, becomes rapidly activated upon stimulation with agonists. Though it has been implicated to act downstream from G protein-coupled receptors (GPCRs) and upstream of integrin alpha IIbbeta3, the precise role of Rap1b in platelet function has been elusive. Here we report the generation of a murine rap1b knockout and show that Rap1b deficiency results in a bleeding defect due to defective platelet function. Aggregation of Rap1b-null platelets is reduced in response to stimulation with both GPCR-linked and GPCR-independent agonists. Underlying the defective Rap1b-null platelet function is decreased activation of integrin alphaIIbbeta3 in response to stimulation with agonists and signaling downstream from the integrin alpha IIbbeta3. In vivo, Rap1b-null mice are protected from arterial thrombosis. These data provide genetic evidence that Rap1b is involved in a common pathway of integrin activation, is required for normal hemostasis in vivo, and may be a clinically relevant antithrombotic therapy target.
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Affiliation(s)
- Magdalena Chrzanowska-Wodnicka
- Department of Medicine and Carolina Cardiovascular Biology Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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10
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Lim CJ, Spiegelman GB, Weeks G. Cytoskeletal regulation by Dictyostelium Ras subfamily proteins. J Muscle Res Cell Motil 2003; 23:729-36. [PMID: 12952071 DOI: 10.1023/a:1024471527153] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The Ras subfamily proteins are monomeric GTPases that function as molecular switches in cellular signal transduction. The roles of six of these proteins in regulating actin cytoskeletal functions in Dictyostelium discoideum are discussed in this review.
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Affiliation(s)
- Chinten James Lim
- Department of Microbiology and Immunology, University of British Columbia, 300-6174 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z3
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11
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Weeks G, Spiegelman GB. Roles played by Ras subfamily proteins in the cell and developmental biology of microorganisms. Cell Signal 2003; 15:901-9. [PMID: 12873703 DOI: 10.1016/s0898-6568(03)00073-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The Ras subfamily proteins are monomeric GTPases that function as molecular switches in cellular signal transduction pathways. This review describes our current knowledge of the roles that these proteins play in the growth and differentiation of single celled microorganisms.
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Affiliation(s)
- Gerald Weeks
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
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12
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Kang R, Kae H, Ip H, Spiegelman GB, Weeks G. Evidence for a role for the Dictyostelium Rap1 in cell viability and the response to osmotic stress. J Cell Sci 2002; 115:3675-82. [PMID: 12186953 DOI: 10.1242/jcs.00039] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Dictyostelium genome contains a single rapA gene, which encodes a Rap1 monomeric G protein. As attempts at generating rapA-null Dictyostelium cells had been unsuccessful, expression of antisense RNA from the rapA gene under control of the folate repressible discoidin promoter was used to reduce cellular levels of the Rap1 protein. As Rap1 levels gradually decreased following antisense rapA RNA induction, growth rate and cell viability also decreased, a result consistent with the idea that rapA is an essential gene. The Rap1-depleted cells exhibited reduced viability in response to osmotic shock. The accumulation of cGMP in response to 0.4 M sorbitol was reduced after rapA antisense RNA induction and was enhanced in cells expressing the constitutively activated Rap1(G12V) protein, suggesting a role for Rap1 in the generation of cGMP. Dictyostelium Rap1 formed a complex with the Ras-binding domain of RalGDS only when it was in a GTP-bound state. This assay was used to demonstrate that activation of Rap1 in response to 0.4 M sorbitol occurred with initial kinetics similar to those observed for the accumulation of cGMP. Furthermore, the addition of 2 mM EDTA to osmotically shocked cells, a treatment that enhances cGMP accumulation, also enhanced Rap1 activation. These results suggest a direct role for Rap1 in the activation of guanylyl cyclase during the response to hyperosmotic conditions. Rap1 was also activated in response to low temperature but not in response to low osmolarity or high temperature.
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Affiliation(s)
- Rujun Kang
- Department of Microbiology and Immunology, University of British Columbia, 300-6174 University Blvd., Vancouver, BC V6T 1Z3, Canada
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Chubb JR, Insall RH. Dictyostelium: an ideal organism for genetic dissection of Ras signalling networks. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1525:262-71. [PMID: 11257439 DOI: 10.1016/s0304-4165(01)00111-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Signalling pathways based on the small GTPase Ras regulate a multitude of cellular events in eukaryotic cells. Dictyostelium expresses a large and varied family of Ras proteins. It also uses a range of known Ras regulators, in particular RasGEFs, and effectors. The genetic tractability of Dictyostelium, together with the wide range of Ras proteins and regulators, make it an ideal model for the genetic dissection of Ras pathways. This review highlights the recent advances in our understanding of Ras function in Dictyostelium, and considers the implications of these findings for our understanding of eukaryotic signal transduction.
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Affiliation(s)
- J R Chubb
- School of Biosciences, Birmingham University, B15 2TT, Birmingham, UK
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14
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Wilkins A, Chubb JR, Insall RH. A novel Dictyostelium RasGEF is required for normal endocytosis, cell motility and multicellular development. Curr Biol 2000; 10:1427-37. [PMID: 11102804 DOI: 10.1016/s0960-9822(00)00797-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Dictyostelium possesses a surprisingly large number of Ras proteins and little is known about their activators, the guanine nucleotide exchange factors (GEFs). It is also unclear, in Dictyostelium or in higher eukaryotes, whether Ras pathways are linear, with each Ras controlled by its own GEF, or networked, with multiple GEFs acting on multiple Ras proteins. RESULTS We have identified the Dictyostelium gene that encodes RasGEFB, a protein with homology to known RasGEFs such as the Son-of-sevenless (Sos) protein. Dictyostelium cells in which the gene for RasGEFB was disrupted moved unusually rapidly, but lost the ability to perform macropinocytosis and therefore to grow in liquid medium. Crowns, the sites of macropinocytosis, were replaced by polarised lamellipodia. Mutant cells were also profoundly defective in early development, although they eventually formed tiny but normally proportioned fruiting bodies. This defect correlated with loss of discoidin Igamma mRNA, a starvation-induced gene, although other genes required for development were expressed normally or even precociously. RasGEFB was able to rescue a Saccharomyces CDC25 mutant, indicating that it is a genuine GEF for Ras proteins. CONCLUSIONS RasGEFB appears to be the principal activator of the RasS protein, which regulates macropinocytosis and cell speed, but it also appears to regulate one or more other Ras proteins.
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Affiliation(s)
- A Wilkins
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, WC1E 6BT, London, UK
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15
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Khosla M, Spiegelman GB, Insall R, Weeks G. Functional overlap of the dictyostelium RasG, RasD and RasB proteins. J Cell Sci 2000; 113 ( Pt 8):1427-34. [PMID: 10725225 DOI: 10.1242/jcs.113.8.1427] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Disruption of the rasG gene in Dictyostelium discoideum results in several distinct phenotypes: a defect in cytokinesis, reduced motility and reduced growth. Reintroduction of the rasG gene restores all of the properties of the rasG(-) cells to those of the wild type. To determine whether the defects are due to impaired interactions with a single or multiple downstream effectors, we tested the ability of the highly related but non identical Dictyostelium ras genes, rasD and rasB, to rescue the defects. Introduction of the rasD gene under the control of the rasG promoter into rasG null (rasG(-)) cells corrected all phenotypes except the motility defect, suggesting that motility is regulated by a RasG mediated pathway that is different to those regulating growth or cytokinesis. Western blot analysis of RasD protein levels revealed that vegetative rasG(-)cells contained considerably more protein than the parental AX-3 cells, suggesting that RasD protein levels are negatively regulated in vegetative cells by RasG. The level of RasD was enhanced when the rasD gene was introduced under the control of the rasG promoter, and this increase in protein is presumably responsible for the reversal of the growth and cytokinesis defects of the rasG(-)cells. Thus, RasD protein levels are controlled by the level of RasG, but not by the level of RasD. Introduction of the rasB gene under the control of the rasG promoter into rasG(-) cells produced a complex phenotype. The transformants were extremely small and mononucleate and exhibited enhanced motility. However, the growth of these cells was considerably slower than the growth of the rasG(-) cells, suggesting the possibility that high levels of RasB inhibit an essential process. This was confirmed by expressing rasB in wild-type cells; the resulting transformants exhibited severely impaired growth. When RasB protein levels were determined by western blot analysis, it was found that levels were higher in the rasG(-)cells than they were in the wild-type parental, suggesting that RasG also negatively regulates rasB expression in vegetative cells. Overexpression of rasB in the rasG(-)cells also reduced the level of RasD protein. In view of the fact that alternate Ras proteins correct some, but not all, of the defects exhibited by the rasG(-) cells, we propose that RasG interacts with more than one downstream effector. In addition, it is clear that the levels of the various Ras proteins are tightly regulated in vegetative cells and that overexpression can be deleterious.
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Affiliation(s)
- M Khosla
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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16
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Chubb JR, Wilkins A, Thomas GM, Insall RH. The Dictyostelium RasS protein is required for macropinocytosis, phagocytosis and the control of cell movement. J Cell Sci 2000; 113 ( Pt 4):709-19. [PMID: 10652263 DOI: 10.1242/jcs.113.4.709] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endocytosis and cell migration both require transient localised remodelling of the cell cortex. Several lines of evidence suggest a key regulatory role in these activities for members of the Ras family of small GTPases. We have generated Dictyostelium cells lacking one member of this family, RasS, and the mutant cells are perturbed in endocytosis and cell migration. Mutant amoebae are defective in phagocytosis and fluid-phase endocytosis and are impaired in growth. Conversely, the rasS(-)cells show an enhanced rate of cell migration, moving three times faster than wild-type controls. The mutant cells display an aberrant morphology, are highly polarised, carry many elongated actin protrusions and show a concomitant decrease in formation of pinocytic crowns on the cell surface. These morphological aberrations are paralleled by changes in the actin cytoskeleton, with a significant proportion of the cortical F-actin relocalised to prominent pseudopodia. Rapid migration and endocytosis appear to be mutually incompatible and it is likely that RasS protein is required to maintain the normal balance between these two actin-dependent processes.
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Affiliation(s)
- J R Chubb
- MRC Laboratory for Molecular Cell Biology, Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK
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17
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18
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Zhang T, Rebstein PJ, Khosla M, Cardelli J, Buczynski G, Bush J, Spiegelman GB, Weeks G. A mutation that separates the RasG signals that regulate development and cytoskeletal function in Dictyostelium. Exp Cell Res 1999; 247:356-66. [PMID: 10066363 DOI: 10.1006/excr.1998.4368] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of an activated RasG, RasG-G12T, in vegetative cells of Dictyostelium discoideium produced an alteration in cell morphology. Cells underwent a transition between an extensively flattened form that exhibited lateral membrane ruffling to a less flattened form that exhibited prominent dorsal membrane ruffling. These rasG-G12T transformants exhibited a redistribution of F-actin at the cell periphery and did not undergo the rapid contraction upon refeeding that is characteristic of wild-type cells. These results suggest a role for RasG in regulating cytoskeletal rearrangement in D. discoideum. We had shown previously that expression of rasG-G12T inhibited starvation induced aggregation (M. Khosla et al., 1996, Mol. Cell. Biol. 16, 4156-4162). rasG-G12T genes containing secondary mutations were transformed into cells to test whether the effects of rasG-G12T were transmitted through a single downstream effector. Cells expressing rasG-G12T/T35S or rasG-G12T/Y40C (secondary mutations within the effector domain) exhibited normal morphology and underwent normal aggregation, suggesting that signaling through the effector domain was required for both the morphological and the development changes induced by rasG-G12T. In contrast, cells expressing rasG-G12T/T45Q (a secondary mutation in the effector distal flanking domain) exhibited normal aggregation but a morphology indistinguishable from that of rasG-G12T transformants. This result suggests that RasG regulates developmental and cytoskeletal functions by direct interaction with more than one downstream effector.
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Affiliation(s)
- T Zhang
- Department of Microbiology and Immunology, Department of Medical Genetics, University of British Columbia, 6174 University Boulevard, Vancouver, British Columbia, V6T 1Z3, Canada
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19
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Seastone DJ, Zhang L, Buczynski G, Rebstein P, Weeks G, Spiegelman G, Cardelli J. The small Mr Ras-like GTPase Rap1 and the phospholipase C pathway act to regulate phagocytosis in Dictyostelium discoideum. Mol Biol Cell 1999; 10:393-406. [PMID: 9950684 PMCID: PMC25176 DOI: 10.1091/mbc.10.2.393] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The function of the small-Mr Ras-like GTPase Rap1 remains largely unknown, but this protein has been demonstrated to regulate cortical actin-based morphologic changes in Dictyostelium and the oxidative burst in mammalian neutrophils. To test whether Rap1 regulates phagocytosis, we biochemically analyzed cell lines that conditionally and modestly overexpressed wild-type [Rap1 WT(+)], constitutively active [Rap1 G12T(+)], and dominant negative [Rap1 S17N(+)] forms of D. discoideum Rap1. The rates of phagocytosis of bacteria and latex beads were significantly higher in Rap1 WT(+) and Rap1 G12T(+) cells and were reduced in Rap1 S17N(+) cells. The addition of inhibitors of protein kinase A, protein kinase G, protein tyrosine kinase, or phosphatidylinositide 3-kinase did not affect phagocytosis rates in wild-type cells. In contrast, the addition of U73122 (a phospholipase C inhibitor), calphostin C (a protein kinase C inhibitor), and BAPTA-AM (an intracellular Ca2+ chelator) reduced phagocytosis rates by 90, 50, and 65%, respectively, suggesting both arms of the phospholipase C signaling pathways played a role in this process. Other protein kinase C-specific inhibitors, such as chelerythrine and bisindolylmaleimide I, did not reduce phagocytosis rates in control cells, suggesting calphostin C was affecting phagocytosis by interfering with a protein containing a diacylglycerol-binding domain. The addition of calphostin C did not reduce phagocytosis rates in Rap1 G12T(+) cells, suggesting that the putative diacylglycerol-binding protein acted upstream in a signaling pathway with Rap1. Surprisingly, macropinocytosis was significantly reduced in Rap1 WT(+) and Rap1 G12T(+) cells compared with control cells. Together our results suggest that Rap1 and Ca2+ may act together to coordinate important early events regulating phagocytosis.
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Affiliation(s)
- D J Seastone
- Department of Microbiology and Immunology, Shreveport, Louisiana 71130, USA
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20
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Louis SA, Weeks G, Spiegelman GB. Rap1 overexpression reveals that activated RasD induces separable defects during Dictyostelium development. Dev Biol 1997; 190:273-83. [PMID: 9344544 DOI: 10.1006/dbio.1997.8675] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
One of the Dictyostelium ras genes, rasD, is expressed preferentially in prestalk cells at the slug stage of development and overexpression of this gene containing a G12T activating mutation causes the formation of aberrant multitipped aggregates that are blocked from further development (Reymond et al., 1986, Nature, 323, 340-343). The ability of the Dictyostelium rap1 gene to suppress this abnormal developmental phenotype was investigated. The rap1 gene and G12V activated and G10V negative mutant forms of the rap1 gene were independently linked to the rasD promoter and each construct used to transform M1, a Dictyostelium cell line expressing RasD[G12T]. Transformants of M1 that expressed Rap1 or Rap1[G12V] protein still formed multitipped aggregates, but most tips were able to complete development and form fruiting bodies. Cell lines showing this modified phenotype were designated ME (multitipped escape). The rap1[G10V] construct did not modify the M1 phenotype. These data suggest that overexpression of RasD[G12T] has two effects, the formation of a multitipped aggregate and a block in subsequent differentiation and that the expression of Rap1 or Rap1[G12V] reverses only the latter. Differentiation of ME cells in low density monolayers showed the identical low level of stalk and spore cell formation seen for M1 cells under the same conditions. Thus the cell autonomous defect in monolayer differentiation induced in the M1 strain was not corrected in the ME strain. Cell type-specific gene expression during the development of M1 cells is dramatically altered: prestalk cell-specific gene expression is greatly enhanced, whereas prespore-specific gene expression is almost suppressed (Louis et al., 1997, Mol. Biol. Cell, 8, 303-312). During the development of ME cells, ecmA mRNA levels were restored to those seen for Ax3, and tagB mRNA levels were also markedly reduced, although not to Ax3 levels. cotC expression in ME cells was enhanced severalfold relative to M1, although levels were still lower than those observed during the development of Ax3. The low expression of car1 mRNA during early development of the M1 strain remained low during the development of ME cells. These data are consistent with the idea that the expression of RasD[G12T] affects two independent and temporally separated events and that only the later defect is reversed by rap1.
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Affiliation(s)
- S A Louis
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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21
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Rebstein PJ, Cardelli J, Weeks G, Spiegelman GB. Mutational analysis of the role of Rap1 in regulating cytoskeletal function in Dictyostelium. Exp Cell Res 1997; 231:276-83. [PMID: 9087168 DOI: 10.1006/excr.1996.3466] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
It was shown previously that increased expression of the ras-related rap1 gene in Dictyostelium discoideum altered cell morphology (Rebstein et al., Dev. Genet., 1993, 14, 347-355). Vegetative Rap1 transformants were more flattened and spread than parental Ax2 cells and had increased F-actin near the cell periphery. In addition, Rap1 cells were inhibited in the rapid cell contraction that occurs upon refeeding with nutrient media. In this communication, we show that expression of Rap also markedly reduces the contraction response that occurs upon addition of azide to vegetative cells. The changes in cell morphology, the refeeding contraction response, and the azide contraction response have been used to analyze mutants of Rap1 generated by site-directed mutagenesis. The substitution G12V, predicted to increase the proportion of protein binding GTP, did not alter the effect of Rap on cell morphology or on its ability to inhibit the contraction response to azide, but modestly enhanced the ability of Rap1 to inhibit cell rounding in response to nutrient media. The substitution S17N, predicted to restrict the protein to the GDP-bound state, did not produce the flattened cell morphology and abolished the inhibitory effects of Rap in the two cell contraction assays. These results are consistent with a requirement of GTP binding for the Rap-induced effects. Transformants carrying the Rap-S17N protein had a more polar morphology than the parental Ax2 cells, suggesting the possibility that Rap-S17N interferes with the ability of endogenous Rap to regulate the cytoskeleton. Substitutions at amino acid 38, within the presumptive effector domain, reduced but did not abolish the effects of Rap1 on cell contraction, while the substitution T61Q had no effect on Rap1 activity. Taken together, the results suggest that Rap may have multiple regulatory effects on cytoskeletal function.
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Affiliation(s)
- P J Rebstein
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
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22
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Insall RH, Borleis J, Devreotes PN. The aimless RasGEF is required for processing of chemotactic signals through G-protein-coupled receptors in Dictyostelium. Curr Biol 1996; 6:719-29. [PMID: 8793298 DOI: 10.1016/s0960-9822(09)00453-9] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Ras proteins are small GTP-binding proteins that play an essential role in a wide range of processes, particularly in mammalian growth control. They act as molecular switches, being inactive when GDP is bound, and active when associated with GTP. Activation is accomplished by guanine nucleotide exchange factors (RasGEFs); when RasGEFs interact with Ras proteins, GDP is allowed to escape, and is replaced by GTP. Dictyostelium responds to chemoattractants through typical seven transmembrane domain receptors and heterotrimeric G proteins. There are at least five different Dictyostelium Ras genes, whose functions are not yet known. RESULTS We have isolated the aimless gene, which encodes the Dictyostelium homologue of RasGEFs, during a screen for insertional mutants that fail to aggregate. We found that aimless null mutants grew at a normal rate, but were severely impaired in both chemotaxis and activation of adenylyl cyclase, both of which are critical for the early stages of development. Although coupling between receptors and their G proteins is unaffected, and several cyclic AMP (cAMP)-mediated responses appear normal, activation of adenylyl cyclase by receptors and GTP gamma S (a non-hydrolyzable GTP analogue) is reduced by up to 95%. The motility of mutant cells appears normal, suggesting a true defect in gradient sensing. CONCLUSIONS The discovery of the aimless gene adds an interesting new member to the family of RasGEFs. Our data suggest an unforeseen role for a RasGEF, and therefore presumably a complete Ras pathway, in the processing of chemotactic signals through G-protein-coupled receptors.
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Affiliation(s)
- R H Insall
- MRC Laboratory for Molecular Cell Biology, University College London, UK.
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23
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Kozlowski P, Trzcinska-Danielewicz J, Toczko K. Identification and sequence analysis of a rap gene from the true slime mold Physarum polycephalum. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1305:29-33. [PMID: 8605245 DOI: 10.1016/0167-4781(95)00207-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A member of the ras gene superfamily, belonging to the rap family and designated Pprap1, was isolated from a cDNA library from the true slime mold Physarum polycephalum by plaque hybridization in combination with 5'-RACE. The assembled nucleotide sequence of Pprap1 (1062 bp) has an open reading frame coding for a protein of 188 amino acids of a calculated M(r) of 21035. This protein exhibits: (i) a highly conserved GTP binding domain containing a putative effector domain, with the threonine-for-glutamine substitution characteristic of rap proteins, (ii) a hypervariable domain, and (iii) the CAAX motif. Analysis of the C-terminal amino acid sequence of Pprap1 shows that it presumably undergoes geranylgeranylation but is not palmitoylated; however, it contains a lysine-rich domain which might serve as the second membrane localization signal. Pprap1 exhibits significantly high amino acid homology within the GTP binding domain with its homologues: Ddrap1 from Dictyostelium discoideum (92%) and human Rap1A (83%), and relatively low homology (59%) with the Saccharomyces cerevisiae homologue, RSR1. It has also 59% and 61% homology with the P. polycephalum Ppras1 and Ppras2 proteins, respectively. This gene is the third member of the ras gene superfamily identified in P. polycephalum so far.
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Affiliation(s)
- P Kozlowski
- Institute of Biochemistry, Warsaw University, Poland
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24
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Bosch TC, Benitez E, Gellner K, Praetzel G, Salgado LM. Cloning of a ras-related gene from Hydra which responds to head-specific signals. Gene 1995; 167:191-5. [PMID: 8566776 DOI: 10.1016/0378-1119(95)00703-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Members of the Ras family of proteins are important components of signal transduction pathways responding to external signals and leading to changes in cell behavior. Analysis of two ras-related genes in the phylogenetically old metazoan Hydra indicates that in normal animals both genes are expressed in all body regions of the polyp. Upon head removal, however, the transcript level of one of the two genes, ras2, decreases rapidly in the upper gastric region which is adjacent to the former head. The decrease is transient and specific for ras2, since no changes could be observed in the transcript level of the related ras1 gene or any other gene. The disappearance of the ras2 mRNA can be prevented completely by brief exposure of decapitated polyps to the protein kinase C activator TPA, which previously was shown to be capable of converting gastric tissue into head tissue [Müller, W.A. In: Othmer, H.G. (Ed.) Experimental and Theoretical Advances in Biological Pattern Formation. Plenum Press, New York, NY, 1993, pp. 237-253]. The finding that Hydra ras2 expression is strongly dependent on a signal from the head provides the first evidence for ras expression being regulated in pattern formation.
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Affiliation(s)
- T C Bosch
- Zoological Institute, University of Munich, Germany
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25
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Skala J, Nawrocki A, Goffeau A. The sequence of a 27 kb segment on the right arm of chromosome VII from Saccharomyces cerevisiae reveals MOL1, NAT2, RPL30B, RSR1, CYS4, PEM1/CHO2, NSR1 genes and ten new open reading frames. Yeast 1995; 11:1421-7. [PMID: 8585325 DOI: 10.1002/yea.320111410] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The DNA sequence of a 26,677 bp fragment from the right arm of chromosome VII from Saccharomyces cerevisiae reveals 18 open reading frames (ORFs) longer than 300 bp. Eight ORFs correspond to previously characterized genes. G6620 is the 3' end of the MOL1 gene coding for a polypeptide similar to stress-inducible proteins from Fusarium; G6630 is the NAT2 gene which encodes a methionine N-acetyltransferase; G6635 is the RPL30B gene coding for the ribosomal protein L30; G6658 is RSR1 encoding a ras-related protein; G6667 is CYS4, the gene for cystathionine beta-synthase; G6670 is identical to ORF2 located close to CYS4; G6673 is PEM1/CHO2 encoding a phosphatidylethanolamine methyltransferase; G7001 is the NSR1 gene coding for a nuclear signal recognition protein. G6664 shares significant homology with the ORF YKR076w from chromosome XI. The other nine ORFs show no significant homology to any protein sequence presently available in the public data bases.
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Affiliation(s)
- J Skala
- Institute of Microbiology, Wroclaw University, Poland
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26
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Loomis WF, Welker D, Hughes J, Maghakian D, Kuspa A. Integrated maps of the chromosomes in Dictyostelium discoideum. Genetics 1995; 141:147-57. [PMID: 8536963 PMCID: PMC1206713 DOI: 10.1093/genetics/141.1.147] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Detailed maps of the six chromosomes that carry the genes of Dictyostelium discoideum were constructed by correlating physically mapped regions with parasexually determined linkage groups. Chromosomally assigned regions were ordered and positioned by the pattern of altered fragment sizes seen in a set of restriction enzyme mediated integration-restriction fragment length polymorphism (REMI-RFLP) strains each harboring an inserted plasmid that carries sites recognized by NotI, SstI, SmaI, BglI and ApaI. These restriction enzymes were used to digest high molecular weight DNA prepared from more than 100 REMI-RFLP strains and the resulting fragments were separated and sized by pulsed-field gels. More than 150 gene probes were hybridized to blots of these gels and used to map the insertion sites relative to flanking restriction sites. In this way, we have been able to restriction map the 35 mb genome as well as determine the map position of more than 150 genes to with approximately 40 kb resolution. These maps provide a framework for subsequent refinement.
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Affiliation(s)
- W F Loomis
- Department of Biology, University of California at San Diego, La Jolla 92093, USA
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27
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Abstract
A set of 147 Dictyostelium discoideum strains was constructed by random integration of a vector containing rare restriction sites. The strains were generated by transformation using restriction enzyme-mediated integration (REMI) which results in the integration of linear DNA fragments into randomly distributed genomic restriction sites. Restriction fragment length polymorphism (RFLP) was generated in a single genomic site in each strain. These REMI-RFLP strains were used to confirm gene linkages previously supported by two other physical mapping techniques: yeast artificial chromosome (YAC) contig construction, and megabase-scale restriction mapping. New linkages were uncovered when two or more hybridization probes identified the same RFLP fragments. Probes for 100 genes have marked 53% of the RFLPs, representing greater than 22 Mb of the 40 Mb Dictyostelium genome. Alignment of these and other large fragments along each chromosome should lead to a complete physical map of the Dictyostelium genome.
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Affiliation(s)
- A Kuspa
- Department of Biology, University of California, San Diego, La Jolla 92093-0322
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28
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Bush J, Nolta K, Rodriguez-Paris J, Kaufmann N, O'Halloran T, Ruscetti T, Temesvari L, Steck T, Cardelli J. A Rab4-like GTPase in Dictyostelium discoideum colocalizes with V-H(+)-ATPases in reticular membranes of the contractile vacuole complex and in lysosomes. J Cell Sci 1994; 107 ( Pt 10):2801-12. [PMID: 7876348 DOI: 10.1242/jcs.107.10.2801] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In the course of screening a cDNA library for ras-related Dictyostelium discoideum genes, we cloned a 0.7 kb cDNA (rabD) encoding a putative protein that was 70% identical at the amino acid level to human Rab4. Rab4 is a small M(r) GTPase, which belongs to the Ras superfamily and functions to regulate endocytosis in mammalian cells. Southern blot analysis indicated that the rabD cDNA was encoded by a single copy gene while Northern blot analysis revealed that the rabD gene was expressed at relatively constant levels during growth and differentiation. Affinity-purified antibodies were prepared against a RabD fusion protein expressed in bacteria; the antibodies recognized a single 23 kDa polypeptide on western blots of cell extracts. Density gradient fractionation revealed that the RabD antigen co-distributed primarily with buoyant membranes rich in vacuolar protons pumps (V-H(+)-ATPases) and, to a lesser extent, with lysosomes. This result was confirmed by examining cell lines expressing an epitope-tagged version of RabD. Magnetically purified early endocytic vesicles and post-lysosomal vacuoles reacted more weakly with anti-RabD antibodies than did lysosomes. Other organelles were negative for RabD. Double-label indirect immunofluorescence microscopy revealed that RabD and the 100 kDa V-H(+)-ATPase subunit colocalized in a fine reticular network throughout the cytoplasm. This network was reminiscent of spongiomes, the tubular elements of the contractile vacuole system. Immunoelectron microscopy confirmed the presence of RabD in lysosome fractions and in the membranes rich in V-H(+)-ATPase. We conclude that a Rab4-like GTPase in D. discoideum is principally associated with the spongiomes of contractile vacuole complex.
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Affiliation(s)
- J Bush
- Department of Microbiology and Immunology, LSU Medical Center, Shreveport 71130
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29
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Bush J, Franek K, Cardelli J. Cloning and characterization of seven novel Dictyostelium discoideum rac-related genes belonging to the rho family of GTPases. Gene 1993; 136:61-8. [PMID: 8294042 DOI: 10.1016/0378-1119(93)90448-c] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cellular processes including proliferation, organization of the actin cytoskeleton, vesicular traffic and secretion of proteins comprising the lysosomal/endosomal system are regulated by low-molecular-weight GTP-binding proteins of the Ras superfamily. However, to date only three Dictyostelium discoideum ras-like genes and two ypt-1/sec4-like genes have been identified and characterized. We report here the identification (using an oligodeoxyribonucleotide probe) of seven additional cDNAs coding for members highly related to the Rac proteins (Ras-related-C3 botulinum toxin substrate) which belong to the Rho (Ras homologous) family of GTPases. Three of these rac-related genes (rac1A, rac1B and rac1C) predict proteins with > 90% amino acid (aa) sequence identity with each other and > 80% identity to the human rac1 gene product, whereas the other members (racA, racB, racC and racD) predict proteins with 46-74% identity to the rac1 and rhoA gene products and to each other. The D. discoideum proteins were entirely conserved over the four regions known to be important for GTP binding and all contained the C-terminal CAAX aa motifs shared by other Rho proteins. Interestingly, the D. discoideum rac-related genes revealed unique patterns of expression during growth and development. For instance, the steady-state level of rac1 mRNA, encoded by three highly related genes, increased transiently during aggregation and then rapidly decreased. In contrast, the cellular abundance of mRNAs encoded by the other rac-like genes decreased at different rates and to different levels during development from the peak levels observed during growth. This suggests that the GTP-binding proteins encoded by these genes may play unique roles during the different stages of the D. discoideum life cycle.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Bush
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130
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Bush J, Franek K, Daniel J, Spiegelman GB, Weeks G, Cardelli J. Cloning and characterization of five novel Dictyostelium discoideum rab-related genes. Gene 1993; 136:55-60. [PMID: 8294041 DOI: 10.1016/0378-1119(93)90447-b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Low-M(r) GTPases belonging to the Ras superfamily are known to regulate a wide range of cellular processes including cell proliferation, actin cytoskeleton organization, and vesicular trafficking along the secretory and endosomal/lysosomal pathway. We are studying the regulation of lysosomal and endosomal vesicular trafficking in the simple eukaryote, Dictyostelium discoideum. Using an oligodeoxyribonucleotide (oligo) encoding one of the most highly conserved amino acid (aa) regions found in the low-M(r) GTPases (important in GTP binding), we have cloned 18 new cDNAs encoding proteins belonging to the Ras superfamily. In this report, we describe the characterization of five of these cDNAs coding for proteins belonging to the Ypt1/Sec4/Rab family; mammalian members of this family have been shown to function in the regulation of vesicular trafficking. Two of the cDNAs, rab1A and rab1B, code for proteins highly homologous to mammalian Rab1. An additional cDNA, rabA, codes for a protein that is only 60% identical to Rab1 at the aa sequence level and probably represents a new member of the rab gene family. Finally, two cDNAs, rabB and rabC, code for novel proteins belonging to the Rab gene family that are no greater than 50% identical in aa sequence to any previously described member. Southern blot analysis indicated that rab1A and and rab1B belong to a small Dictyostelium family of at least five related genes, while rabA belongs to a different and smaller family of related genes. In contrast, rabB and rabC appear to be represented by single genes.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Bush
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130
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Noda M. Structures and functions of the K rev-1 transformation suppressor gene and its relatives. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1155:97-109. [PMID: 8504133 DOI: 10.1016/0304-419x(93)90024-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- M Noda
- Department of Viral Oncology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
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Rebstein PJ, Weeks G, Spiegelman GB. Altered morphology of vegetative amoebae induced by increased expression of the Dictyostelium discoideum ras-related gene rap1. DEVELOPMENTAL GENETICS 1993; 14:347-55. [PMID: 7507418 DOI: 10.1002/dvg.1020140504] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The rap1 gene of Dictyostelium discoideum is a member of the ras-gene superfamily of low molecular weight GTPase proteins. The rap1 gene is expressed both during growth and development in D. discoideum. To examine the action of the Rap1 protein in D. discoideum, the rap1 cDNA was expressed under the control of the inducible discoidin promoter. Treatment with conditioned media, which induces the discoidin promoter, increased Rap1 protein levels in vegetative cells approximately six fold. Overexpression of the Rap1 protein correlated with the appearance of morphologically aberrant vegetative amoebae: cells were extensively spread and flattened. The distribution of F-actin was altered in these cells, with an increase in actin staining around the cell periphery. Induction of the discoidin promoter by starvation in the rap1 transformants also resulted in spread flat cells. When starved D. discoideum amoebae are refed with HL5 media, the cells rapidly respond by rounding up. By contrast, the rap1 transformant cells showed a pronounced delay in rounding up. Rapid tyrosine phosphorylation of a p45 protein occurred in both control cells and the rap1 transformant upon refeeding, implying that the signal transduction pathway leading to tyrosine phosphorylation remained functional in the rap1 transformant. We propose that the Rap1 protein functions in the regulation of cell morphology in D. discoideum.
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Affiliation(s)
- P J Rebstein
- Department of Microbiology, University of British Columbia, Vancouver, Canada
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Thioredoxins from Dictyostelium discoideum are a developmentally regulated multigene family. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50177-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Robbins SM, Khosla M, Thiery R, Weeks G, Spiegelman GB. Ras-related genes in Dictyostelium discoideum. DEVELOPMENTAL GENETICS 1991; 12:147-53. [PMID: 2049874 DOI: 10.1002/dvg.1020120123] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Dictyostelium discoideum, like other eukaryotes, has been shown to express several ras-related genes. Two gene products, Ddras and DdrasG, are highly conserved relative to the human ras proteins. Ddras is expressed at the pseudoplasmodial stage of development, whereas DdrasG is expressed in vegetative cells and during early development. In addition, Dictyostelium possesses three ras-related genes, SAS1, SAS2 and Ddrap1, whose gene products are only partially conserved relative to those of the ras genes. The expression of these three genes is also developmentally regulated.
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Affiliation(s)
- S M Robbins
- Department of Microbiology, University of British Columbia, Vancouver, Canada
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Affiliation(s)
- R Herzog
- Institute of Human Genetics, Saar-University, Homburg/Saar, FRG
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New nucleotide sequence data on the EMBL File Server. Nucleic Acids Res 1990; 18:6747-51. [PMID: 2251162 PMCID: PMC332687 DOI: 10.1093/nar/18.22.6747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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