RasG protein accumulation occurs just prior to amoebae emergence during spore germination in Dictyostelium discoideum

Khosla, Meenal; Spiegelman, George B.; Sands, Todd W.; Virdy, Kiran J.; Cotter, David A.

doi:10.1111/j.1574-6968.1994.tb06782.x

Cited by 13 publications

(5 citation statements)

References 14 publications

(19 reference statements)

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“…In Dictyostelium discoideum, RasG protein levels were very low in dormant spores, remained low during the lag period, but only increased late during spore swelling just prior to the emergence stage of germination (Khosla et al, 1994). Our data show that many more new proteins were synthesized during the period of germ tube emergence (4 h) which may be accounted for by the activation of ribosomes and increasing capacity of the protein synthesizing system (Horikoshi and Ikeda, 1968).…”

Section: Discussionmentioning

confidence: 66%

Dormancy, activation and viability of Rhizopus oligosporus sporangiospores

Thành

Nout

2004

International Journal of Food Microbiology

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Section: Discussionmentioning

confidence: 66%

Dormancy, activation and viability of Rhizopus oligosporus sporangiospores

Thành

Nout

2004

International Journal of Food Microbiology

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“…Thus, the third objective was to monitor the changes in the phosphorylation of proteins that occurred upon RasG(G12T) expression and to identify these proteins using proteomic techniques. (Khosla et al, 1994;Lim, 2002).…”

Section: Objectivesmentioning

confidence: 99%

The identification of Dictyostelium phosphoproteins altered in response to the activation of RasG

et al. 2004

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Dictyostelium RasG has been implicated in the regulation of a variety of cellular processes, including the initiation of development, cell movement, and cytokinesis, but the molecular components of the signaling pathways involved are largely unknown. We used a tetracycline-regulated protein expression system to study the effect of activated RasG, RasG(G12T), expression on the phosphorylation state of Dictyostelium proteins. Over 70 vegetative phosphoprotein components were resolved by two-dimensional (2-D) immunoblot analysis and of these 16 phosphothreonine and three phosphotyrosine protein components were found to reproducibly change upon RasG(G12T) expression. Thirteen of these were recovered from 2-D gels and identified by mass spectrometry of in-gel tryptic digestions. The proteins identified include the signaling proteins RasGEF-R and protein kinase B, the adhesion protein DdCAD-1, the cytoskeletal protein actin, the mitochondrial division protein FtsZA, and proteins involved in translation and metabolism. In addition to the direct demonstration of the phosphorylation of putative downstream targets of RasG activation, these findings reveal previously undetected phosphorylation of several proteins.

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“…After electrophoresis, the proteins were transferred to nitrocellulose membranes for 1 h at 90 V (41) and probed with a purified polyclonal anti-RasG antibody (22). The membranes were incubated in 5% powdered milk (Carnation) in Tris-buffered saline (TBS)-Tween (25 mM Tris-Cl [pH 8.0], 1.0% NaCl, 0.5% Tween 20) overnight at 4ЊC and were then washed twice for 5 min with TBS.…”

Section: Methodsmentioning

confidence: 99%

Overexpression of an Activated rasG Gene during Growth Blocks the Initiation of Dictyostelium Development

Khosla

Spiegelman

Weeks

1996

Molecular and Cellular Biology

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Transformants that expressed either the wild-type rasG gene, an activated rasG-G12T gene, or a dominant negative rasG-S17N gene, all under the control of the folate-repressible discoidin (dis1␥) promoter, were isolated. All three transformants expressed high levels of Ras protein which were reduced by growth in the presence of folate. All three transformants grew slowly, and the reduction in growth rate correlated with the amount of RasG protein produced, suggesting that RasG is important in regulating cell growth. The pVEIIrasG transformant containing the wild-type rasG gene developed normally despite the presence of high levels of RasG throughout development. This result indicates that the down regulation of rasG that normally occurs during aggregation of wild-type strains is not essential for the differentiation process. Dictyostelium transformants expressing the dominant negative rasG-S17N gene also differentiated normally. Dictyostelium transformants that overexpressed the activated rasG-G12T gene did not aggregate. The defect occurred very early in development, since the expression of car1 and pde, genes that are normally induced soon after the initiation of development, was repressed. However, when the transformant cells were pulsed with cyclic AMP, expression of both genes returned to wild-type levels. The transformants exhibited chemotaxis to cyclic AMP, and development was synergized by mixing with wild-type cells. Furthermore, cells that were pulsed with cyclic AMP for 4 h before being induced to differentiate by plating on filters produced small, but otherwise normal, fruiting bodies. These results suggest that the rasG-G12T transformants are defective in cyclic AMP production and that RasG ⅐ GTP blocks development by interfering with the initial generation of cyclic AMP pulses.

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RasG protein accumulation occurs just prior to amoebae emergence during spore germination in Dictyostelium discoideum

Cited by 13 publications

References 14 publications

Dormancy, activation and viability of Rhizopus oligosporus sporangiospores

Dormancy, activation and viability of Rhizopus oligosporus sporangiospores

The identification of Dictyostelium phosphoproteins altered in response to the activation of RasG

Overexpression of an Activated rasG Gene during Growth Blocks the Initiation of Dictyostelium Development

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