Expression of a cAMP receptor gene of Dictyostelium and evidence for a multigene family.

Saxe, Charles L.; Johnson, Ronald L.; Devreotes, Peter N.; Kimmel, Alan R.

doi:10.1101/gad.5.1.1

Cited by 98 publications

(59 citation statements)

References 34 publications

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“…These data indicate that both transcripts derive from the same gene. As is the case for other genes in Dictyostelium expressing two transcripts, we expect this is due to two promoters rather than differential splicing within the open reading frame (Faure et al, 1990;Mann and Firtel, 1991;Saxe et al, 1991;Mann et al, 1992;Rogers et al, 1997). …”

mentioning

confidence: 78%

DictyosteliumStress-activated Protein Kinase α, a Novel Stress-activated Mitogen-activated Protein Kinase Kinase Kinase-like Kinase, Is Important for the Proper Regulation of the Cytoskeleton

Sun

Firtel

2003

MBoC

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Mitogen-activated protein kinase cascades regulate various cellular functions, including growth, cell differentiation, development, and stress responses. We have identified a new Dictyostelium kinase (stress-activated protein kinase [SAPK]␣), which is related to members of the mixed lineage kinase class of mitogen-activated protein kinase kinases. SAPK␣ is activated by osmotic stress, heat shock, and detachment from the substratum and by a membrane-permeable cGMP analog, a known regulator of stress responses in Dictyostelium. SAPK␣ is important for cellular resistance to stresses, because SAPK␣ null cells exhibit reduced viability in response to osmotic stress. We found that SAPK␣ mutants affect cellular processes requiring proper regulation of the actin cytoskeleton, including cell motility, morphogenesis, cytokinesis, and cell adhesion. Overexpression of SAPK␣ results in highly elevated basal and chemoattractant-stimulated F-actin levels and strong aggregation and developmental defects, including a failure to polarize and chemotax, and abnormal morphogenesis. These phenotypes require a kinase-active SAPK␣. SAPK␣ null cells exhibit reduced chemoattractant-stimulated F-actin levels, cytokinesis, developmental and adhesion defects, and a motility defect that is less severe than that exhibited by SAPK␣-overexpressing cells. SAPK␣ colocalizes with F-actin in F-actin-enriched structures, including membrane ruffles and pseudopodia during chemotaxis. Although SAPK␣ is required for these F-actin-mediated processes, it is not detectably activated in response to chemoattractant stimulation. INTRODUCTIONThe actin cytoskeleton plays a vital role in numerous cellular processes, such as cell locomotion, phagocytosis, cytokinesis, cell adhesion, cell shape changes, and stress responses. During these processes, the actin cytoskeleton is dynamically changed, a process that involves F-actin polymerization and depolymerization and the reorganization of existing filament networks. Mutations of signaling molecules or structural elements involved in these changes affect cellular processes to various extents.Eukaryotic cells are constantly exposed to stress conditions. To survive, cells adopt various mechanisms to adapt to environmental changes. Mitogen-activated protein kinase (MAPK) pathways regulate cellular responses to external stress in various organisms, including yeast, plants, and mammals (Canman and Kastan, 1996;Jonak et al., 1996;Gustin et al., 1998;Hirt, 2000;Kyriakis and Avruch, 2001;O'Rourke et al., 2002). In Saccharomyces cerevisiae, the wellcharacterized HOG1 MAPK pathway is activated by osmotic stress and leads to gene expression and glycerol production, which is critical for yeast cells to withstand osmotic stress (Gustin et al., 1998;O'Rourke et al., 2002). In mammalian cells, the c-Jun NH 2 -terminal kinase/stress-activated protein kinase (JNK/SAPK1) pathway and the p38/SAPK2 MAP kinase pathway are both activated by diverse stimuli including UV, osmotic, and thermal stresses (Canman and Kastan, 1996;Chang and Kari...

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confidence: 78%

DictyosteliumStress-activated Protein Kinase α, a Novel Stress-activated Mitogen-activated Protein Kinase Kinase Kinase-like Kinase, Is Important for the Proper Regulation of the Cytoskeleton

Sun

Firtel

2003

MBoC

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“…We chose to compare cAMPinduced expression of CAR1 in wild-type cells, g␣2-null cells, and g␣2-null cells that express G␣9 (g␣2 − [G␣9 WT ]) using the highly active, constitutive actin promoter. CAR1 is the best characterized marker for early Dictyostelium development (Saxe et al 1991;Louis et al 1993;Mu et al 1998Mu et al , 2001, and its cAMP-regulated expression requires activation of G␤␥, but not of ACA (Saxe et al 1991). Thus, the antagonistic action of G␣9 on ACA should not inhibit CAR1 expression.…”

Section: Ectopic Expression Of G␣9 Rescues G␤␥-dependent Developmentamentioning

confidence: 99%

A Gα-dependent pathway that antagonizes multiple chemoattractant responses that regulate directional cell movement

Brzostowski¹,

Parent²,

Kimmel³

2004

Genes Dev.

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Chemotactic cells, including neutrophils and Dictyostelium discoideum, orient and move directionally in very shallow chemical gradients. As cells polarize, distinct structural and signaling components become spatially constrained to the leading edge or rear of the cell. It has been suggested that complex feedback loops that function downstream of receptor signaling integrate activating and inhibiting pathways to establish cell polarity within such gradients. Much effort has focused on defining activating pathways, whereas inhibitory networks have remained largely unexplored. We have identified a novel signaling function in Dictyostelium involving a G␣ subunit (G␣9) that antagonizes broad chemotactic response. Mechanistically, G␣9 functions rapidly following receptor stimulation to negatively regulate PI3K/PTEN, adenylyl cyclase, and guanylyl cyclase pathways. The coordinated activation of these pathways is required to establish the asymmetric mobilization of actin and myosin that typifies polarity and ultimately directs chemotaxis. Most dramatically, cells lacking G␣9 have extended PI(3,4,5)P 3 , cAMP, and cGMP responses and are hyperpolarized. In contrast, cells expressing constitutively activated G␣9 exhibit a reciprocal phenotype. Their second message pathways are attenuated, and they have lost the ability to suppress lateral pseudopod formation. Potentially, functionally similar G␣-mediated inhibitory signaling may exist in other eukaryotic cells to regulate chemoattractant response.[Keywords: cAMP; cGMP; PI(3,4,5)P 3 ; actin; myosin; Dictyostelium] Supplemental material is available at http://www.genesdev.org.

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“…These genes include the cAMP receptor cAR1, the coupled G␣ subunit G␣2, and the cell adhesion molecule Contact Sites A (csA) (Noegel et al, 1986;Mann et al, 1988;Kumagai et al, 1989;Saxe et al, 1991). These genes are induced in wild-type strains during aggregation, with expression peaking at 4 -8 h of development or in shaking culture in response to cAMP pulsing (Firtel, 1995;Ginsburg et al, 1995).…”

Section: Rip3 Is Developmentally Regulated and Required For Aggregationmentioning

confidence: 99%

A Novel Ras-interacting Protein Required for Chemotaxis and Cyclic Adenosine Monophosphate Signal Relay inDictyostelium

Lee

Parent

Insall

et al. 1999

MBoC

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We have identified a novel Ras-interacting protein from Dictyostelium, RIP3, whose function is required for both chemotaxis and the synthesis and relay of the cyclic AMP (cAMP) chemoattractant signal. rip3 null cells are unable to aggregate and lack receptor activation of adenylyl cyclase but are able, in response to cAMP, to induce aggregation-stage, postaggregative, and cell-type-specific gene expression in suspension culture. In addition, rip3 null cells are unable to properly polarize in a cAMP gradient and chemotaxis is highly impaired. We demonstrate that cAMP stimulation of guanylyl cyclase, which is required for chemotaxis, is reduced ϳ60% in rip3 null cells. This reduced activation of guanylyl cyclase may account, in part, for the defect in chemotaxis. When cells are pulsed with cAMP for 5 h to mimic the endogenous cAMP oscillations that occur in wild-type strains, the cells will form aggregates, most of which, however, arrest at the mound stage. Unlike the response seen in wild-type strains, the rip3 null cell aggregates that form under these experimental conditions are very small, which is probably due to the rip3 null cell chemotaxis defect. Many of the phenotypes of the rip3 null cell, including the inability to activate adenylyl cyclase in response to cAMP and defects in chemotaxis, are very similar to those of strains carrying a disruption of the gene encoding the putative Ras exchange factor AleA. We demonstrate that aleA null cells also exhibit a defect in cAMP-mediated activation of guanylyl cyclase similar to that of rip3 null cells. A double-knockout mutant (rip3/aleA null cells) exhibits a further reduction in receptor activation of guanylyl cyclase, and these cells display almost no cell polarization or movement in cAMP gradients. As RIP3 preferentially interacts with an activated form of the Dictyostelium Ras protein RasG, which itself is important for cell movement, we propose that RIP3 and AleA are components of a Ras-regulated pathway involved in integrating chemotaxis and signal relay pathways that are essential for aggregation.

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Expression of a cAMP receptor gene of Dictyostelium and evidence for a multigene family.

Cited by 98 publications

References 34 publications

DictyosteliumStress-activated Protein Kinase α, a Novel Stress-activated Mitogen-activated Protein Kinase Kinase Kinase-like Kinase, Is Important for the Proper Regulation of the Cytoskeleton

DictyosteliumStress-activated Protein Kinase α, a Novel Stress-activated Mitogen-activated Protein Kinase Kinase Kinase-like Kinase, Is Important for the Proper Regulation of the Cytoskeleton

A Gα-dependent pathway that antagonizes multiple chemoattractant responses that regulate directional cell movement

A Novel Ras-interacting Protein Required for Chemotaxis and Cyclic Adenosine Monophosphate Signal Relay inDictyostelium

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