Paka, a Putative Pak Family Member, Is Required for Cytokinesis and the Regulation of the Cytoskeleton in <i>Dictyostelium discoideum</i> Cells during Chemotaxis

Chung, Chang Y.; Firtel, Richard A.

doi:10.1083/jcb.147.3.559

Cited by 145 publications

(162 citation statements)

References 86 publications

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“…Twenty-four hours after transferring the cells from a Petri dish to shaking culture, spkA null cells with one or two nuclei/cell increased to ϳ69% compared with ϳ78% for JH10 cells. The decrease in the number of multinucleate cells when grown in suspension culture is the opposite of observations for mutants in the myosin II pathway (e.g., myosin II, PAKa, RLC null strains; Fukui et al, 1990;Zang et al, 1997;Chaudoir et al, 1999;Chung and Firtel, 1999). These strains produce large, multinucleate cells in suspension but are often mono-or dinucleate when grown on Petri plates, as the cells are able to pull themselves apart by traction-mediated cytofission (Fukui et al, 1990).…”

Section: Spka Null Cells Are Defective In Cytokinesismentioning

confidence: 90%

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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Section: Spka Null Cells Are Defective In Cytokinesismentioning

confidence: 90%

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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“…Several signal transduction components are involved in regulating the actin-myosin cytoskeleton during chemotaxis, including phosphatidylinositol 3-kinase, PAK, WASP, and Ras (Tuxworth et al, 1997;Chung and Firtel, 1999;Lim et al, 2005;Myers et al, 2005). Mutants with deletions of the encoding genes suggest that none of these signaling pathways is essential but that each contributes to chemotaxis to a different extent.…”

Section: Discussionmentioning

confidence: 99%

Guanylyl Cyclase Protein and cGMP Product Independently Control Front and Back of ChemotaxingDictyosteliumCells

Veltman

Haastert

2006

MBoC

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Chemotaxis of amoeboid cells is driven by actin filaments in leading pseudopodia and actin-myosin filaments in the back and at the side of the cell to suppress pseudopodia. In Dictyostelium, cGMP plays an important role during chemotaxis and is produced predominantly by a soluble guanylyl cyclase (sGC). The sGC protein is enriched in extending pseudopodia at the leading edge of the cell during chemotaxis. We show here that the sGC protein and the cGMP product have different functions during chemotaxis, using two mutants that lose either catalytic activity (sGC⌬cat) or localization to the leading edge (sGC⌬N). Cells expressing sGC⌬N exhibit excellent cGMP formation and myosin localization in the back of the cell, but they exhibit poor orientation at the leading edge. Cells expressing the catalytically dead sGC⌬cat mutant show poor myosin localization at the back, but excellent localization of the sGC protein at the leading edge, where it enhances the probability that a new pseudopod is made in proximity to previous pseudopodia, resulting in a decrease of the degree of turning. Thus cGMP suppresses pseudopod formation in the back of the cell, whereas the sGC protein refines pseudopod formation at the leading edge. INTRODUCTIONChemotaxis is a vital process in a variety of organisms, ranging from bacteria to vertebrates. Prokaryotes use chemotaxis to move toward high nutrient concentrations or away from unfavorable conditions, whereas in eukaryotes chemotaxis is also involved in embryogenesis, wound healing, and the immune response. Chemotaxis is achieved by coupling gradient sensing to basic cell movement. Prokaryotes are too small to sense spatial gradients and therefore rely on temporal changes of the chemoattractant concentration to achieve chemotaxis. They do this by adjusting their tumbling frequency in response to temporal changes of the chemoattractant concentration (Szurmant and Ordal, 2004;Wadhams and Armitage, 2004). Eukaryotic cells are typically large enough to be able to measure a spatial gradient. The difference in receptor occupation between each side of the cell leads to an internal polarization. A pseudopod is extended at the side with the highest receptor occupation and at the same time, pseudopod formation at all other sides is repressed, resulting in directional cell migration (Devreotes and Janetopoulos, 2003;Postma et al., 2004).Dictyostelium is a eukaryotic organism that is widely used to study chemotaxis (Williams and Harwood, 2003;Parent, 2004;Affolter and Weijer, 2005). Starved Dictyostelium cells periodically secrete cAMP. Through relay of the cAMP signal by neighboring cells, concentric cAMP waves are generated. Starved Dictyostelium cells are chemotactically sensitive to cAMP and by movement in the direction of the origin of the cAMP waves, the cells are able to aggregate into groups of up to 100,000 cells. The chemotactic response of Dictyostelium is optimized for the dynamic cAMP waves that coordinate both aggregation and multicellular development. Cells show a much stronger chemotact...

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“…Upon chemoattractant stimulation, there is a rapid release of cortexillin I from the cortex followed by a transient translocation to the cell cortex with a peak at ~5 s and a subsequent decrease to the basal level. An initial delocalization from the cell cortex upon stimulation is also found in the translocation kinetics of several proteins including myosin II, PTEN, and PakA (Chung and Firtel, 1999;Funamoto et al, 2002;Jeon et al, 2007b), but the subsequent transient translocation of cortexillin I to the cortex within 10 s is not observed with other proteins. The transient translocation kinetics of cortexillin I, except the initial delocalization of the proteins, is similar to that of the Arp2/3 complex, a nucleator of F-actin assembly.…”

Section: Discussionmentioning

confidence: 91%

Dynamic Localization of the Actin-Bundling Protein Cortexillin I during Cell Migration

Cha

Jeon

2011

Molecules and Cells

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Cortexillins are actin-bundling proteins that play a critical role in regulating cell morphology and actin cytoskeleton reorganization in Dictyostelium. Here, we investigated dynamic subcellular localization of cortexillin I in chemotaxing Dictyostelium cells. Most of the cortexillin I was enriched on the lateral sides of moving cells. Upon chemoattractant stimulation, cortexillin I was rapidly released from the cortex followed by a transient translocation to the cell cortex with a peak at ~5 s and a subsequent decrease to basal levels, indicating that localization of cor-texillin I at the cortex in chemotaxing cells is controlled by two more signaling components, one for the initial delocalization from the cortex and another for the translocation to the cortex ~5 s after chemoattractant stimulation. Loss of cortexillins leads to reduced cell polarity and an in-creased number of lateral pseudopodia during chemotaxis, suggesting that cortexillins play an inhibitory role in producing pseudopodia along the lateral sides of the cell. Cells lacking cortexillins displayed extended chemoattrac-tantmediated Arp2/3 complex translocation kinetics to the cortex. Our present study provides a new insight into the function of cortexillins during reorganization of the actin cytoskeleton and cell migration.

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Paka, a Putative Pak Family Member, Is Required for Cytokinesis and the Regulation of the Cytoskeleton in Dictyostelium discoideum Cells during Chemotaxis

Cited by 145 publications

References 86 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

Guanylyl Cyclase Protein and cGMP Product Independently Control Front and Back of ChemotaxingDictyosteliumCells

Dynamic Localization of the Actin-Bundling Protein Cortexillin I during Cell Migration

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