title: Initiation of multicellular differentiation in Dictyostelium discoideum is regulated by coronin A.
abstract: Many biological systems respond to environmental changes by activating intracellular signaling cascades, resulting in an appropriate response. One such system is represented by the social amoeba Dictyostelium discoideum. When food sources become scarce, these unicellular cells can initiate a cAMP-driven multicellular aggregation program to ensure long-term survival. On starvation, the cells secrete conditioned medium factors that initiate cAMP signal transduction by inducing expression of genes such as cAMP receptors and adenylate cyclase. The mechanisms involved in the activation of the first pulses of cAMP release have been unclear. We here show a crucial role for the evolutionarily conserved protein coronin A in the initiation of the cAMP response. On starvation, coronin A-deficient cells failed to up-regulate the expression of cAMP-regulated genes, thereby failing to initiate development, despite a normal prestarvation response. Of importance, external addition of cAMP to coronin A-deficient cells resulted in normal chemotaxis and aggregate formation, thereby restoring the developmental program and suggesting a functional cAMP relay in the absence of coronin A. These results suggest that coronin A is dispensable for cAMP sensing, chemotaxis, and development per se but is part of a signal transduction cascade essential for system initiation leading to multicellular development in Dictyostelium.
authors.affiliation: Biozentrum, University of Basel, 4056 Basel, Switzerland Faculty of Medicine, University of Geneva, CH-1211 Geneva 4, Switzerland.
authors.forename: Adrien F
authors.initials: AF
authors.lastname: Vinet
authors.forename: Thomas
authors.initials: T
authors.lastname: Fiedler
authors.forename: Vera
authors.initials: V
authors.lastname: Studer
authors.forename: Romain
authors.initials: R
authors.lastname: Froquet
authors.forename: Anna
authors.initials: A
authors.lastname: Dardel
authors.forename: Pierre
authors.initials: P
authors.lastname: Cosson
authors.forename: Jean
authors.initials: J
authors.lastname: Pieters
mesh_terms: D000222:Adaptation, Physiological; D002633:Chemotaxis; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D004023:Dictyostelium / Q000166:cytology*; D017353:Gene Deletion; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D059467:Transcriptome
chemical_list: D008840:Microfilament Proteins; D015800:Protozoan Proteins; C072061:coronin proteins; D000242:Cyclic AMP