Rho Signaling in Dictyostelium discoideum.

Small GTPases of the Rho family are ubiquitous molecular switches involved in the regulation of most actin cytoskeleton dependent processes and many other processes not directly linked to actin. D. discoideum is a well-established model organism for studies of the actin cytoskeleton and its regulation by signal transduction pathways. D. discoideum is equipped with a complex repertoire of Rho signaling components, with 20 Rho GTPases, more than 100 regulators (including exchange factors, GTPase activating proteins and guanine nucleotide dissociation inhibitors), and nearly 80 effectors or components of effector complexes. In this review we examine the knowledge accumulated to date about proteins involved in Rho-regulated signaling pathways in D. discoideum, with an emphasis on functional studies. We integrate the information about individual components into defined signaling pathways, with a focus on three extensively investigated processes: chemotaxis, vesicle trafficking, and cytokinesis.