Ras-mediated activation of the TORC2–PKB pathway is critical for chemotaxis

Cai, Huaqing; Das, Satarupa; Kamimura, Yoichiro; Lan, Yu; Parent, Carole A.; Devreotes, Peter N.

doi:10.1083/jcb.201001129

Cited by 119 publications

(157 citation statements)

References 43 publications

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“…Because TORC2 activation is necessary for ACA activity, we first examined the cAMP-mediated phosphorylation of PKBR1 at different developmental time points in WT and mutant cell lines. TORC2 mediates the phosphorylation of the hydrophobic motif of PKBR1 within its C-terminal regulatory domain (19,41). In agreement with what we observed for ACA activation, we found that in 3-and 5-h developed WT cells, a saturating cAMP stimulus triggers a rapid phosphorylation of the hydrophobic motif of PKBR1, which peaks at 30 -60 s and declines to basal levels by 2-3 min (Fig.…”

Section: Basal Car1 Phosphorylation Increases During Dictyosteliumsupporting

confidence: 78%

Direct Biochemical Measurements of Signal Relay during Dictyostelium Development

Das

Rericha

Bagorda

et al. 2011

Journal of Biological Chemistry

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Upon starvation, individual Dictyostelium discoideum cells enter a developmental program that leads to collective migration and the formation of a multicellular organism. The process is mediated by extracellular cAMP binding to the G proteincoupled cAMP receptor 1, which initiates a signaling cascade leading to the activation of adenylyl cyclase A (ACA), the synthesis and secretion of additional cAMP, and an autocrine and paracrine activation loop. The release of cAMP allows neighboring cells to polarize and migrate directionally and form characteristic chains of cells called streams. We now report that cAMP relay can be measured biochemically by assessing ACA, ERK2, and TORC2 activities at successive time points in development after stimulating cells with subsaturating concentrations of cAMP. We also find that the activation profiles of ACA, ERK2, and TORC2 change in the course of development, with later developed cells showing a loss of sensitivity to the relayed signal. We examined mutants in PKA activity that have been associated with precocious development and find that this loss in responsiveness occurs earlier in these mutants. Remarkably, we show that this loss in sensitivity correlates with a switch in migration patterns as cells transition from streams to aggregates. We propose that as cells proceed through development, the cAMP-induced desensitization and down-regulation of cAMP receptor 1 impacts the sensitivities of chemotactic signaling cascades leading to changes in migration patterns.The directed migration of individual cells or chains or sheets of cells requires cells to transduce external cues into internal signals that regulate cytoskeletal reorganization and cell polarity. Signal transduction is important during development where the transition from single to collective cell migration is regulated by multiple external cues (1). Cell-cell communication, a process that can be manifested through the relay of external chemical signals (2, 3), is critical for a wide range of developmental processes including the survival of the social amoebae Dictyostelium discoideum.Upon starvation, Dictyostelium cells enter a developmental program leading to the transition from cells operating individually to groups of cells operating as a population. Aggregation of starving cells is controlled by signaling centers that emit periodic pulses of 3Ј-5Ј-cAMP. This process is mediated by the binding of extracellular cAMP to the G protein-coupled receptor cAR1, 3 which initiates a signaling cascade leading to, among other things, the activation of ACA (4). When ACA is first activated, rapid cAMP synthesis leads to a burst in internal cAMP levels. Although part of the synthesized cAMP remains inside cells to activate PKA and regulate gene expression, the majority of it is rapidly secreted (5-7). The secreted cAMP binds to cAR1 and, in an autocrine and paracrine amplification step, results in the production and secretion of more cAMP (2, 3). For a spatially extended cell population, the stimulated release of cAMP result...

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Section: Basal Car1 Phosphorylation Increases During Dictyosteliumsupporting

confidence: 78%

Direct Biochemical Measurements of Signal Relay during Dictyostelium Development

Das

Rericha

Bagorda

et al. 2011

Journal of Biological Chemistry

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“…S2 C and D). These transient redistributions in response to global stimulation are characteristic of other known "front" and "back" proteins (1,(24)(25)(26)(27)(28)(29)(30). Taken together, these observations suggest that the accumulation of CynA at the lagging edge is stabilized in polarized cells, preventing the protein from relocalizing in response to chemoattractant.…”

Section: Significancesupporting

confidence: 51%

Novel protein Callipygian defines the back of migrating cells

Swaney

Borleis

Iglesias

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Asymmetric protein localization is essential for cell polarity and migration. We report a novel protein, Callipygian (CynA), which localizes to the lagging edge before other proteins and becomes more tightly restricted as cells polarize; additionally, it accumulates in the cleavage furrow during cytokinesis. CynA protein that is tightly localized, or "clustered," to the cell rear is immobile, but when polarity is disrupted, it disperses throughout the membrane and responds to uniform chemoattractant stimulation by transiently localizing to the cytosol. These behaviors require a pleckstrin homology-domain membrane tether and a WD40 clustering domain, which can also direct other membrane proteins to the back. Fragments of CynA lacking the pleckstrin homology domain, which are normally found in the cytosol, localize to the lagging edge membrane when coexpressed with full-length protein, showing that CynA clustering is mediated by oligomerization. Cells lacking CynA have aberrant lateral protrusions, altered leading-edge morphology, and decreased directional persistence, whereas those overexpressing the protein display exaggerated features of polarity. Consistently, actin polymerization is inhibited at sites of CynA accumulation, thereby restricting protrusions to the opposite edge. We suggest that the mutual antagonism between CynA and regions of responsiveness creates a positive feedback loop that restricts CynA to the rear and contributes to the establishment of the cell axis.chemotaxis | polarity | asymmetry | Dictyostelium | protein localization

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“…Although Pia, like the other interacting subunits of the TORC2 complex, fails to form a stable complex with TOR (Cai et al, 2010), ACA activation in Dictyostelium appears to require a pre-formed TORC2 complex (Lee et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

“…Chemotactic cell motility is regulated by a TORC2-PDKA-PKB (PKBA and PKBR1) signalling network, that transduces G-protein and RasC-or RasG-linked membrane signals to the actin cytoskeleton, leading to cell polarization and oriented movement (Lim et al, 2001;Sasaki et al, 2004;Cai et al, 2010;Zhang et al, 2008;Lee et al, 2005;Kamimura et al, 2008). PKBA and PKBR1 are transiently phosphorylated within seconds after cAMP stimulation (Meili et al, 2000;Kamimura et al, 2008;Kamimura and Devreotes, 2010).…”

Section: Spontaneous Hsb1mentioning

confidence: 99%

A new HECT ubiquitin ligase regulating chemotaxis and development in Dictyostelium discoideum

Pergolizzi

Bracco

Bozzaro

2017

Journal of Cell Science

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Cyclic AMP (cAMP) binding to G-protein-coupled receptors (GPCRs) orchestrates chemotaxis and development in Dictyostelium. By activating the RasC-TORC2-PKB (PKB is also known as AKT in mammals) module, cAMP regulates cell polarization during chemotaxis. TORC2 also mediates GPCR-dependent stimulation of adenylyl cyclase A (ACA), enhancing cAMP relay and developmental gene expression. Thus, mutants defective in the TORC2 Pia subunit (also known as Rictor in mammals) are impaired in chemotaxis and development. Near-saturation mutagenesis of a Pia mutant by random gene disruption led to selection of two suppressor mutants in which spontaneous chemotaxis and development were restored. PKB phosphorylation and chemotactic cell polarization were rescued, whereas Pia-dependent ACA stimulation was not restored but bypassed, leading to cAMP-dependent developmental gene expression. Knocking out the gene encoding the adenylylcyclase B (ACB) in the parental strain showed ACB to be essential for this process. The gene tagged in the suppressor mutants encodes a newly unidentified HECT ubiquitin ligase that is homologous to mammalian HERC1, but harbours a pleckstrin homology domain. Expression of the isolated wild-type HECT domain, but not a mutant HECT C5185S form, from this protein was sufficient to reconstitute the parental phenotype. The new ubiquitin ligase appears to regulate cell sensitivity to cAMP signalling and TORC2-dependent PKB phosphorylation.

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Ras-mediated activation of the TORC2–PKB pathway is critical for chemotaxis

Abstract: RasC controls the spatial and temporal activity of TORC2 to regulate directional cell migration.

Cited by 119 publications

References 43 publications

Direct Biochemical Measurements of Signal Relay during Dictyostelium Development

Direct Biochemical Measurements of Signal Relay during Dictyostelium Development

Novel protein Callipygian defines the back of migrating cells

A new HECT ubiquitin ligase regulating chemotaxis and development in Dictyostelium discoideum

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