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Hadwiger JA, Aranda RG, Fatima S. Atypical MAP kinases - new insights and directions from amoeba. J Cell Sci 2023; 136:jcs261447. [PMID: 37850857 PMCID: PMC10617611 DOI: 10.1242/jcs.261447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2023] Open
Abstract
Mitogen-activated protein kinases (MAPKs) have been the focus of many studies over the past several decades, but the understanding of one subgroup of MAPKs, orthologs of MAPK15, known as atypical MAPKs, has lagged behind others. In most organisms, specific activating signals or downstream responses of atypical MAPK signaling pathways have not yet been identified even though these MAPKs are associated with many eukaryotic processes, including cancer and embryonic development. In this Review, we discuss recent studies that are shedding new light on both the regulation and function of atypical MAPKs in different organisms. In particular, the analysis of the atypical MAPK in the amoeba Dictyostelium discoideum has revealed important roles in chemotactic responses and gene regulation. The rapid and transient phosphorylation of the atypical MAPK in these responses suggest a highly regulated activation mechanism in vivo despite the ability of atypical MAPKs to autophosphorylate in vitro. Atypical MAPK function can also impact the activation of other MAPKs in amoeba. These advances are providing new perspectives on possible MAPK roles in animals that have not been previously considered, and this might lead to the identification of potential targets for regulating cell movement in the treatment of diseases.
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Affiliation(s)
- Jeffrey A. Hadwiger
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078-3020, USA
| | - Ramee G. Aranda
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078-3020, USA
| | - Saher Fatima
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078-3020, USA
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IQGAP-related protein IqgC suppresses Ras signaling during large-scale endocytosis. Proc Natl Acad Sci U S A 2019; 116:1289-1298. [PMID: 30622175 DOI: 10.1073/pnas.1810268116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Macropinocytosis and phagocytosis are evolutionarily conserved forms of bulk endocytosis used by cells to ingest large volumes of fluid and solid particles, respectively. Both processes are regulated by Ras signaling, which is precisely controlled by mechanisms involving Ras GTPase activating proteins (RasGAPs) responsible for terminating Ras activity on early endosomes. While regulation of Ras signaling during large-scale endocytosis in WT Dictyostelium has been, for the most part, attributed to the Dictyostelium ortholog of human RasGAP NF1, in commonly used axenic laboratory strains, this gene is mutated and inactive. Moreover, none of the RasGAPs characterized so far have been implicated in the regulation of Ras signaling in large-scale endocytosis in axenic strains. In this study, we establish, using biochemical approaches and complementation assays in live cells, that Dictyostelium IQGAP-related protein IqgC interacts with active RasG and exhibits RasGAP activity toward this GTPase. Analyses of iqgC - and IqgC-overexpressing cells further revealed participation of this GAP in the regulation of both types of large-scale endocytosis and in cytokinesis. Moreover, given the localization of IqgC to phagosomes and, most prominently, to macropinosomes, we propose IqgC acting as a RasG-specific GAP in large-scale endocytosis. The data presented here functionally distinguish IqgC from other members of the Dictyostelium IQGAP family and call for repositioning of this genuine RasGAP outside of the IQGAP group.
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Kortholt A, van Haastert PJM. Highlighting the role of Ras and Rap during Dictyostelium chemotaxis. Cell Signal 2008; 20:1415-22. [PMID: 18385017 DOI: 10.1016/j.cellsig.2008.02.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Accepted: 02/06/2008] [Indexed: 10/22/2022]
Abstract
Chemotaxis, the directional movement towards a chemical compound, is an essential property of many cells and has been linked to the development and progression of many diseases. Eukaryotic chemotaxis is a complex process involving gradient sensing, cell polarity, remodelling of the cytoskeleton and signal relay. Recent studies in the model organism Dictyostelium discoideum have shown that chemotaxis does not depend on a single molecular mechanism, but rather depends on several interconnecting pathways. Surprisingly, small G-proteins appear to play essential roles in all these pathways. This review will summarize the role of small G-proteins in Dictyostelium, particularly highlighting the function of the Ras subfamily in chemotaxis.
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Affiliation(s)
- Arjan Kortholt
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751NN Haren, The Netherlands
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Schroder WA, Buck M, Cloonan N, Hancock JF, Suhrbier A, Sculley T, Bushell G. Human Sin1 contains Ras-binding and pleckstrin homology domains and suppresses Ras signalling. Cell Signal 2007; 19:1279-89. [PMID: 17303383 DOI: 10.1016/j.cellsig.2007.01.013] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 01/08/2007] [Accepted: 01/09/2007] [Indexed: 11/28/2022]
Abstract
Human Sin1 (SAPK-interacting protein 1) is a member of a conserved family of orthologous proteins that have an essential role in signal transduction in yeast and Dictyostelium. This study demonstrates that most Sin1 orthologues contain both a Raf-like Ras-binding domain (RBD) and a pleckstrin homology (PH) domain. These domains are functional in the human Sin1 protein, with the PH domain involved in lipid and membrane binding by Sin1, and the RBD able to bind activated H-and K-Ras. Sin1 and Ras co-immunoprecipitated and co-localised, showing that these proteins associate with each other in vivo. Overexpression of Sin1 inhibited the activation of ERK, Akt and JNK signalling pathways by Ras. In contrast, siRNA knockdown of endogenous Sin1 protein expression in HEK293 cells enhanced the activation of ERK1/2 by Ras. These data suggest that Sin1 is a mammalian Ras-inhibitor.
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Affiliation(s)
- Wayne A Schroder
- The Queensland Institute of Medical Research, Brisbane, Australia
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Abstract
Small GTPases are involved in the control of diverse cellular behaviours, including cellular growth, differentiation and motility. In addition, recent studies have revealed new roles for small GTPases in the regulation of eukaryotic chemotaxis. Efficient chemotaxis results from co-ordinated chemoattractant gradient sensing, cell polarization and cellular motility, and accumulating data suggest that small GTPase signalling plays a central role in each of these processes as well as in signal relay. The present review summarizes these recent findings, which shed light on the molecular mechanisms by which small GTPases control directed cell migration.
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Affiliation(s)
- Pascale G. Charest
- Section of Cell and Developmental Biology, Division of Biological Sciences and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0380, U.S.A
| | - Richard A. Firtel
- Section of Cell and Developmental Biology, Division of Biological Sciences and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0380, U.S.A
- To whom correspondence should be sent, at the following address: Natural Sciences Building Room 6316, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0380, U.S.A. (email ). Tel: 858-534-2788, fax: 858-822-5900
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Boeckeler K, Adley K, Xu X, Jenkins A, Jin T, Williams RSB. The neuroprotective agent, valproic acid, regulates the mitogen-activated protein kinase pathway through modulation of protein kinase A signalling in Dictyostelium discoideum. Eur J Cell Biol 2006; 85:1047-57. [PMID: 16759735 DOI: 10.1016/j.ejcb.2006.04.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Activation of the mitogen-activated protein kinase (MAPK) cascade gives rise to a neuroprotective effect in a variety of cell types. The bipolar disorder treatment, valproic acid (VPA), increases the activity of this pathway by modulating extracellular signal-regulated kinase 2 (ERK2) phosphorylation through an unknown mechanism. To investigate the molecular basis of this effect, we have used the biomedical model system Dictyostelium discoideum to dissect this signalling pathway. We find that, similar to mammalian systems, VPA causes a transient increase in the activation of the MAPK signalling pathway, as shown by ERK2 phosphorylation. We show that the MAP kinase and phosphatase, protein kinase A (PKA) and glycogen synthase kinase signalling pathways all function in controlling the levels of phospho-ERK2 (pERK2). We find that VPA induces elevated pERK2 levels through attenuation of the PKA signalling pathway. Interestingly, pERK2 levels are also controlled by another bipolar disorder drug, lithium, providing a common effect of these two drugs. This work therefore suggests a conserved pathway in eukaryotes that is targeted by neuroprotective and bipolar disorder drugs and allows us to propose a model for this neuroprotective effect.
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Affiliation(s)
- Katrina Boeckeler
- Department of Biology and the Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
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Bukharova T, Bukahrova T, Weijer G, Bosgraaf L, Dormann D, van Haastert PJ, Weijer CJ. Paxillin is required for cell-substrate adhesion, cell sorting and slug migration during Dictyostelium development. J Cell Sci 2006; 118:4295-310. [PMID: 16155255 DOI: 10.1242/jcs.02557] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Paxillin is a key regulatory component of focal adhesion sites, implicated in controlling cell-substrate interactions and cell movement. We analyse the function of a Dictyostelium discoideum paxillin homologue, PaxB, which contains four highly conserved LD and four LIM domains, but lacks two characteristic tyrosine residues, that form the core of vertebrate SH2-binding domains. PaxB is expressed during growth and all stages of development, but expression peaks during slug formation. Using a paxB-gfp knockin strain we show the existence of focal adhesions and characterise their dynamics. During multicellular development PaxB is not only found in focal adhesions at the cell-substrate interface, but also in the tips of filopodial structures predominantly located at the trailing ends of cells. paxB- strains are less adhesive to the substrate, they can aggregate but multicellular development from the mound stage onwards is severely impeded. paxB- strains are defective in proper cell type proportioning, cell sorting, slug migration and form-defective fruiting bodies. Mutation of a conserved JNK phosphorylation site, implicated in the control of cell migration, does not have any major effects on cell sorting, slug migration or morphogenesis in Dictyostelium. PaxB does not appear to function redundantly with its closest relative Lim2 (paxA), which when deleted also results in a mound arrest phenotype. However, analysis of paxA- and paxB- single and double null mutants suggest that PaxB may act upstream of Lim2.
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Affiliation(s)
- Tanya Bukharova
- Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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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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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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Lim CJ, Spiegelman GB, Weeks G. RasC is required for optimal activation of adenylyl cyclase and Akt/PKB during aggregation. EMBO J 2001; 20:4490-9. [PMID: 11500376 PMCID: PMC125575 DOI: 10.1093/emboj/20.16.4490] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2001] [Revised: 06/29/2001] [Accepted: 06/29/2001] [Indexed: 12/31/2022] Open
Abstract
Disruption of Dictyostelium rasC, encoding a Ras subfamily protein, generated cells incapable of aggregation. While rasC expression is enriched in a cell type-specific manner during post-aggregative development, the defect in rasC(-) cells is restricted to aggregation and fully corrected by application of exogenous cAMP pulses. cAMP is not produced in rasC(-) cells stimulated by 2'-deoxy-cAMP, but is produced in response to GTPgammaS in cell lysates, indicating that G-protein-coupled cAMP receptor activation of adenylyl cyclase is regulated by RasC. However, cAMP-induced ERK2 phosphorylation is unaffected in rasC(-) cells, indicating that RasC is not an upstream activator of the mitogen-activated protein kinase required for cAMP relay. rasC(-) cells also exhibit reduced chemotaxis to cAMP during early development and delayed response to periodic cAMP stimuli produced by wild-type cells in chimeric mixtures. Furthermore, cAMP-induced Akt/PKB phosphorylation through a phosphatidylinositide 3-kinase (PI3K)-dependent pathway is dramatically reduced in rasC(-) cells, suggesting that G-protein-coupled serpentine receptor activation of PI3K is regulated by RasC. Cells lacking the RasGEF, AleA, exhibit similar defects as rasC(-) cells, suggesting that AleA may activate RasC.
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Affiliation(s)
- Chinten James Lim
- Department of Microbiology and Immunology and Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada Corresponding author e-mail:
| | - George B. Spiegelman
- Department of Microbiology and Immunology and Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada Corresponding author e-mail:
| | - Gerald Weeks
- Department of Microbiology and Immunology and Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada Corresponding author e-mail:
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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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12
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Abstract
Starving Dictyostelium amoebae use cAMP as a chemoattractant to gather into aggregates, as a hormone-like signal to induce cell differentiation, and as an intracellular messenger to control stalk- and spore cell maturation and germination of spores. In this chapter we describe the respective roles of the three adenylyl cyclases ACA, ACB and ACG in controlling cAMP signaling during development and we discuss how cAMP signals are processed by the cells to trigger the large repertoire of gene regulatory events that is under control of this signal molecule.
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Affiliation(s)
- M Meima
- Department of Biochemistry, University of Dundee, Dow Street, Dundee, Scotland, DD1 5EH, UK
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Schenk PW, Nebl T, Fisher PR, Snaar-Jagalska BE. A serpentine receptor-dependent, Gbeta- and Ca(2+) influx-independent pathway regulates mitogen-activated protein kinase ERK2 in Dictyostelium. Biochem Biophys Res Commun 1999; 260:504-9. [PMID: 10403797 DOI: 10.1006/bbrc.1999.0862] [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: 11/22/2022]
Abstract
Ca(2+) influx and mitogen-activated protein (MAP) kinase activation are important phenomena in signal transduction, which are often interconnected. We investigated whether serpentine receptor-dependent, Gbeta-independent activation of MAP kinase ERK2 by chemoattractant cyclic AMP (cAMP) is mediated by Ca(2+) influx in the social amoeba Dictyostelium discoideum. We generated a D. discoideum double mutant, which harbours a temperature-sensitive Gbeta subunit and expresses the apoaequorin protein. Utilizing this mutant, we demonstrate that cAMP induced Ca(2+) influx into intact D. discoideum cells can be blocked completely at both the permissive and the restrictive temperature, by using either gadolinium ions or Ruthenium Red. Under the same experimental conditions, these substances do not abolish cAMP stimulation of ERK2 at either temperature. We conclude that there is a Gbeta- and Ca(2+) influx-independent pathway for the receptor-dependent activation of MAP kinase ERK2 in D. discoideum.
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Affiliation(s)
- P W Schenk
- Section of Cell Biology, Institute of Molecular Plant Sciences, Leiden University, Leiden, 2300 RA, The Netherlands
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