A diffusible factor involved in MAP-kinase ERK2-regulated development of Dictyostelium.
Mitogen-activated protein (MAP)-kinase extracellular signal regulated kinase (ERK2) is essential for regulation of the intracellular cyclic adenosine monophosphate (cAMP) level in Dictyostelium. The mutant lacking ERK2, erk2-null, is arrested at the pre-aggregation stage, but develops into a fruiting body in a mixed population of wild-type and mutant cells. This fact implies that wild-type cells provide a certain factor that is missing in erk2-null. It was clarified that both wild-type strains KAx3 and Ax2 secreted a diffusible factor that enables erk2-null to develop. The fruiting body formed from erk2-null cells was smaller than that formed by the wild-type cells and consisted of a small sorus supported by a slender stalk with a single row of vacuolated stalk cells. The resulting spores were able to germinate and multiply on a bacterial lawn, but they were unable to develop unless the factor was provided. After 8 h of starvation, wild-type cells started to secrete the factor, which had a molecular mass of less than 3 kDa and was heat stable. The effect of this factor could not be mimicked by either cAMP or folate. Adenylyl cyclase A and cell surface cAMP receptors cAR1 and cAR3 were all indispensable components for the factor to function. Considering the molecular mass and the mode of action, this factor could be a novel one. Possible targets of this factor are discussed in terms of cAMP-dependent protein kinase activation.
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Japan. mmaeda@bio.sci.osaka-u.ac.jp
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Maeda
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Kuwayama
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001685:Biological Factors / Q000737:chemistry / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D004023:Dictyostelium / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D005492:Folic Acid / Q000378:metabolism; D006358:Hot Temperature; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D009024:Morphogenesis; D011953:Receptors, Cyclic AMP / Q000378:metabolism; D012098:Reproduction; D013170:Spores
D001685:Biological Factors; C079747:CAR3 protein, Dictyostelium discoideum; D011953:Receptors, Cyclic AMP; C068125:cyclic AMP receptor cAR1; D005492:Folic Acid; D000242:Cyclic AMP; D019950:Mitogen-Activated Protein Kinase 1; D000262:Adenylyl Cyclases