Cyclic AMP signalling in <i>Dictyostelium:</i> G‐proteins activate separate Ras pathways using specific RasGEFs

Kae, Helmut; Kortholt, Arjan; Rehmann, Holger; Insall, Robert H.; Haastert, Peter J.M. van; Spiegelman, George B.; Weeks, Gerald

doi:10.1038/sj.embor.7400936

Cited by 40 publications

(45 citation statements)

References 26 publications

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“…Consistently, the strongest defects in symmetry breaking were observed for cells lacking nfaA and gefR, the only RasG-specific GAP and GEF, respectively, reported so far (Kae et al, 2004;Zhang et al, 2008). Much smaller defects in the chemotactic response were observed in cells lacking the RasC-specific gefA (Kae et al, 2007). However, the deletion experiments also show that activation, symmetry breaking and confinement use a multitude of Ras-GEFs, which are probably not all directly regulating RasG activity (Kae et al, 2007).…”

Section: Discussionmentioning

confidence: 47%

“…Much smaller defects in the chemotactic response were observed in cells lacking the RasC-specific gefA (Kae et al, 2007). However, the deletion experiments also show that activation, symmetry breaking and confinement use a multitude of Ras-GEFs, which are probably not all directly regulating RasG activity (Kae et al, 2007). Furthermore, during confinement the amplification pathways and cell cortex provide feedback regulation on Ras activity.…”

Section: Discussionmentioning

confidence: 99%

“…The strains used are wild-type AX3, rasC-null (Bolourani et al, 2006), gb-null (Wu et al, 1995), ga2-null (Kumagai et al, 1991), gc-null , myoII-null (Yumura et al, 2005), gefA-null (Insall et al, 1996), gefB-null (Wilkins et al, 2000a), gefC-null, gefD-null, gefE-null, gefG-null, gefLnull (Wilkins et al, 2005), gefM-null (Arigoni et al, 2005), gefR-null (Kae et al, 2007) and nfaA-null (Zhang et al, 2008). RasG activation was inhibited by expressing dominant-negative RasGS17N from the previously described doxycycline-inducible vector pDM310 (Veltman et al, 2009b).…”

Section: Cell Culture and Preparationmentioning

confidence: 99%

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Ras activation and symmetry breaking duringDictyosteliumchemotaxis

Kortholt

Keizer‐Gunnink

Kataria

et al. 2013

Journal of Cell Science

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SummaryCentral to chemotaxis is the molecular mechanism by which a shallow spatial gradient of chemoattractant induces symmetry breaking of activated signaling molecules. Previously, we have used Dictyostelium mutants to investigate the minimal requirements for chemotaxis, and identified a basal signaling module providing activation of Ras and F-actin at the leading edge. Here, we show that Ras activation after application of a pipette releasing the chemoattractant cAMP has three phases, each depending on specific guanine-nucleotideexchange factors (GEFs). Initially a transient activation of Ras occurs at the entire cell boundary, which is proportional to the local cAMP concentrations and therefore slightly stronger at the front than in the rear of the cell. This transient Ras activation is present in ga2 (gpbB)-null cells but not in gb (gpbA)-null cells, suggesting that Gbc mediates the initial activation of Ras. The second phase is symmetry breaking: Ras is activated only at the side of the cell closest to the pipette. Symmetry breaking absolutely requires Ga2 and Gbc, but not the cytoskeleton or four cAMP-induced signaling pathways, those dependent on phosphatidylinositol (3,4,5)-triphosphate [PtdIns(3,4,5)P 3 ], cGMP, TorC2 and PLA2. As cells move in the gradient, the crescent of activated Ras in the front half of the cell becomes confined to a small area at the utmost front of the cell. Confinement of Ras activation leads to cell polarization, and depends on cGMP formation, myosin and F-actin. The experiments show that activation, symmetry breaking and confinement of Ras during Dictyostelium chemotaxis uses different G-protein subunits and a multitude of Ras GEFs and GTPase-activating proteins (GAPs).

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Section: Discussionmentioning

confidence: 47%

Section: Discussionmentioning

confidence: 99%

Section: Cell Culture and Preparationmentioning

confidence: 99%

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Ras activation and symmetry breaking duringDictyosteliumchemotaxis

Kortholt

Keizer‐Gunnink

Kataria

et al. 2013

Journal of Cell Science

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“…To monitor how a response governed by the intrinsic polarity of the cell is converted into a response directed by the external gradient, we used a Rasbinding domain (RBD) as a front marker (Zhang et al, 2008). The RBD of human Raf1 recognizes the GTP-bound state of Ras G (Kae et al, 2007), which is important for chemotaxis in Dictyostelium (Takeda et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Local Ras activation, PTEN pattern, and global actin flow in the chemotactic responses of oversized cells

Lange

Prassler

Ecke

et al. 2016

Journal of Cell Science

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Chemotactic responses of eukaryotic cells require a signal processing system that translates an external gradient of attractant into directed motion. To challenge the response system to its limits, we increased the size of Dictyostelium discoideum cells by using electric-pulse-induced fusion. Large cells formed multiple protrusions at different sites along the gradient of chemoattractant, independently turned towards the gradient and competed with each other. Finally, these cells succeeded to re-establish polarity by coordinating front and tail activities. To analyse the responses, we combined two approaches, one aimed at local responses by visualising the dynamics of Ras activation at the front regions of reorientating cells, the other at global changes of polarity by monitoring front-to-tail-directed actin flow. Asymmetric Ras activation in turning protrusions underscores that gradients can be sensed locally and translated into orientation. Different to cells of normal size, the polarity of large cells is not linked to an increasing front-to-tail gradient of the PIP3-phosphatase PTEN. But even in large cells, the front communicates with the tail through an actin flow that might act as carrier of a protrusion inhibitor

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“…The RasC protein is mainly expressed during cell growth and is regulated by RasGefA. It was shown that RasC is critical for chemotaxis toward a cAMP gradient and also for activating adenylyl cyclase (ACA) (Kae et al, 2007). It was also demonstrated that RasC is essential for proper TorC2 activation in response to cAMP and thus chemotaxis (Cai et al, 2010).…”

Section: Effects Of Magnesium Deficiency At the Cellular Levelmentioning

confidence: 99%

Redox Regulation of Ras Proteins in Dictyostelium discoideum

Chabeco¹

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Cyclic AMP signalling in Dictyostelium: G‐proteins activate separate Ras pathways using specific RasGEFs

Cited by 40 publications

References 26 publications

Ras activation and symmetry breaking duringDictyosteliumchemotaxis

Ras activation and symmetry breaking duringDictyosteliumchemotaxis

Local Ras activation, PTEN pattern, and global actin flow in the chemotactic responses of oversized cells

Redox Regulation of Ras Proteins in Dictyostelium discoideum

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