Related Experiment Video
Updated: Jul 8, 2026

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation
Published on: November 9, 2017
Rap1 activation in response to cAMP occurs downstream of ras activation during Dictyostelium aggregation
Parvin Bolourani1, George B Spiegelman, Gerald Weeks
1Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Abstract:
We have used a doubly disrupted rasC(-)/rasG(-) strain of Dictyostelium discoideum, which ectopically expresses the carA gene, to explore the relationship between the activation of RasC and RasG, the two proteins that are necessary for optimum cAMP signaling, and the activation of Rap1, a Ras subfamily protein, that is also activated by cAMP. The ectopic expression of carA restored early developmental gene expression to the rasC(-)/rasG(-) strain, rendering it suitable for an analysis of cAMP signal transduction. Because there was negligible signaling through both the cAMP chemotactic pathway and the adenylyl cyclase activation pathway in the rasC(-)/rasG(-)/[act15]:carA strain, it is clear that RasG and RasC are the only two Ras subfamily proteins that directly control these pathways. The position of Rap1 in the signal transduction cascade was clarified by the finding that Rap1 activation was totally abolished in rasC(-)/rasG(-)/[act15]:carA and rasG(-) cells but only slightly reduced in rasC(-) cells. Rap1 activation, therefore, occurs downstream of the Ras proteins and predominantly, if not exclusively, downstream of RasG. The finding that in vitro guanylyl cyclase activation is also abolished in the rasC(-)/rasG(-)/[act15]:carA strain identifies RasG/RasC as the presumptive monomeric GTPases required for this activation.
More Related Videos
09:40Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum
Published on: September 20, 2011
10:27Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
Published on: March 9, 2012
Related Concept Videos
The Ras Gene
Ras is a superfamily...
MAPK Signaling Cascades
Small GTPases - Ras and Rho
Three regulatory proteins control their activity:
Rab Proteins
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
Cell Polarization by Rho Proteins
IP3/DAG Signaling Pathway