RasC is required for optimal activation of adenylyl cyclase and Akt/PKB during aggregation.
Disruption of Dictyostelium rasC, encoding a Ras subfamily protein, generated cells incapable of aggregation. While rasC expression is enriched in a cell type-specific manner during post-aggregative development, the defect in rasC(-) cells is restricted to aggregation and fully corrected by application of exogenous cAMP pulses. cAMP is not produced in rasC(-) cells stimulated by 2'-deoxy-cAMP, but is produced in response to GTPgammaS in cell lysates, indicating that G-protein-coupled cAMP receptor activation of adenylyl cyclase is regulated by RasC. However, cAMP-induced ERK2 phosphorylation is unaffected in rasC(-) cells, indicating that RasC is not an upstream activator of the mitogen-activated protein kinase required for cAMP relay. rasC(-) cells also exhibit reduced chemotaxis to cAMP during early development and delayed response to periodic cAMP stimuli produced by wild-type cells in chimeric mixtures. Furthermore, cAMP-induced Akt/PKB phosphorylation through a phosphatidylinositide 3-kinase (PI3K)-dependent pathway is dramatically reduced in rasC(-) cells, suggesting that G-protein-coupled serpentine receptor activation of PI3K is regulated by RasC. Cells lacking the RasGEF, AleA, exhibit similar defects as rasC(-) cells, suggesting that AleA may activate RasC.
Lim
C J
CJ
Department of Microbiology and Immunology and Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
Spiegelman
G B
GB
Weeks
G
G
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002633:Chemotaxis; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D004789:Enzyme Activation; D005656:Fungal Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D016296:Mutagenesis; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011953:Receptors, Cyclic AMP / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D000262:Adenylyl Cyclases; D000242:Cyclic AMP; D005656:Fungal Proteins; D019950:Mitogen-Activated Protein Kinase 1; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011953:Receptors, Cyclic AMP; D011993:Recombinant Fusion Proteins; D018631:ras Proteins; C489016:ras protein, Dictyostelium