TEMPERATURE-SENSITIVE G-BETA-MUTANTS DISCRIMINATE BETWEEN G-PROTEIN-DEPENDENT AND G-PROTEIN-INDEPENDENT SIGNALING MEDIATED BY SERPENTINE RECEPTORS

Deletion of the single gene for the Dictyostelium G protein beta-subun it blocks development at an early stage. We have now isolated temperat ure-sensitive alleles of G beta to investigate its role in later devel opment. We show that G beta is directly required for adenylyl cyclase A activation and for morphogenetic signaling during the entire develop mental program. G beta was also essential for induction of aggregative gene expression by cAMP pulses, a process that is mediated by serpent ine cAMP receptors (cARs), However, G beta was not required for cAR-me diated induction of prespore genes and repression of stalk genes, and neither was G beta needed for induction of prestalk genes by the diffe rentiation inducing factor (DIF), cAMP induction of prespore genes and repression of stalk genes is mediated by the protein kinase GSK-3, GS K-3 also determines cell-type specification in insects and vertebrates and is regulated by the wingless/wnt morphogens that are detected by serpentine fi receptors, The G protein-dependent and -independent mode s of cAR-mediated signaling reported here may also exist for the wingl ess/wnt signaling pathways in higher organisms.