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Chemoattractant-induced Ras activation during Dictyostelium aggregation.
Helmut Kae1, Chinten James Lim, George B Spiegelman
1Department of Microbiology and Immunology, University of British Columbia, 300-6174 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z3.
EMBO Reports
|May 15, 2004
Summary
Researchers developed a new assay to measure activated Ras proteins in Dictyostelium discoideum. This study reveals rapid, transient activation of RasC and RasG proteins in response to cAMP signaling during early development.
Area of Science:
- Cellular signaling and molecular biology
- Developmental biology in Dictyostelium discoideum
Background:
- Ras proteins act as molecular switches regulating cellular responses.
- Dictyostelium discoideum possesses a diverse Ras protein family involved in key cellular processes.
- Limited understanding of Ras protein activation mechanisms in Dictyostelium due to assay limitations.
Purpose of the Study:
- To adapt a biochemical assay for measuring activated Ras proteins in Dictyostelium.
- To investigate the activation patterns of RasC and RasG proteins in response to cAMP.
- To elucidate the role of RasC and RasG in early Dictyostelium development.
Main Methods:
- Adaptation of a mammalian cell-based assay to measure activated Ras proteins.
- Utilized Ras-binding domains (RBDs) from mammalian Raf1 and S. pombe Byr2 for detection.
- Stimulated aggregation-competent Dictyostelium cells with cAMP and monitored Ras activation.
Main Results:
- Mammalian Raf1 RBD bound activated RasG but not RasC; S. pombe Byr2 RBD bound both RasC and RasG.
- RasC and RasG exhibited rapid, transient activation upon cAMP stimulation in wild-type cells.
- This activation was absent in several cAMP signaling mutants, indicating pathway dependency.
Conclusions:
- The adapted assay effectively monitors Ras protein activation in Dictyostelium.
- RasC and RasG are rapidly activated by cAMP signaling during early Dictyostelium development.
- These findings support a crucial role for RasC and RasG in Dictyostelium morphogenesis and development.