Switching of chemoattractant receptors programs development and morphogenesis in Dictyostelium: receptor subtypes activate common responses at different agonist concentrations.
One of the common functional features among G-protein coupled receptors is the occurrence of multiple subtypes involved in similar signal transduction events. The cAMP chemoattractant receptor family of Dictyostelium discoideum is composed of four receptors (cAR1-cAR4), which are expressed sequentially throughout the developmental transition from a unicellular to a multicellular organism. The receptors differ in affinity for cAMP and in the sequences of their C-terminal domains. In this study, we constitutively expressed cAR1, cAR2, and cAR3 as well as a series of chimeric and mutant receptors and assessed the capacity of each to mediate chemotaxis, activation of adenylyl cyclase and actin polymerization, and rescue the developmental defect of car1-/car3- cells. We found that various receptors and mutants sense different concentration ranges of cAMP but all can mediate identical responses during the aggregation stage of development. The responses displayed very similar kinetics, suggesting no major differences in regulatory properties attributable to the C-terminal domains. We speculate that switching of receptor subtypes during development enables the organism to respond to the changing concentrations of the chemoattractant and thereby program morphogenesis appropriately.
Kim
J Y
JY
Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Borleis
J A
JA
Devreotes
P N
PN
D000199:Actins / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004023:Dictyostelium / Q000254:growth & development* / Q000378:metabolism; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D011108:Polymers; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins; D011953:Receptors, Cyclic AMP / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
D000199:Actins; C079746:CAR2 protein, Dictyostelium discoideum; C079747:CAR3 protein, Dictyostelium discoideum; C090317:CAR4 protein, Dictyostelium discoideum; D005656:Fungal Proteins; D011108:Polymers; D015800:Protozoan Proteins; D011953:Receptors, Cyclic AMP; C068125:cyclic AMP receptor cAR1; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases