Regulation of myosin regulatory light chain phosphorylation via cyclic GMP during chemotaxis of Dictyostelium.
Previous studies on the chemotactic movement of Dictyostelium have indicated a role for cyclic GMP in regulating the association of myosin II with the cytoskeleton. In this study we have examined the part played by phosphorylation of the 18 kDa myosin regulatory light chain in this event. Using streamer F mutant NP368 (which is deficient in the structural gene for cyclic GMP-specific phosphodiesterase) we find that, for the regulatory light chain kinase, the major peak of phosphorylation is delayed compared to the parental control strain XP55, occurring at 80 seconds rather than about 30 seconds in XP55. In two independently derived mutants that are unable to increase their cellular concentration of cyclic GMP (above basal levels) in response to a chemotactic stimulus of cyclic AMP (KI-10 and SA219), no increase in the phosphorylation of the light chain occurred, or movement of myosin II to the cytoskeleton. We also find a smaller peak of light chain phosphorylation that occurs within 10 seconds of cyclic AMP stimulation of the amoebae, and which is absent in the cyclic GMP-unresponsive strains. We conclude that cyclic GMP is involved in regulating light chain phosphorylation in this system. The possible significance of these findings is discussed and a model that relates these findings to published data on cytoskeletal myosin changes during chemotaxis is presented.
Liu
G
G
Department of Biochemistry, University of Oxford, UK.
Newell
P C
PC
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D002633:Chemotaxis; D006152:Cyclic GMP / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004023:Dictyostelium / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D006706:Homeostasis; D008954:Models, Biological; D008970:Molecular Weight; D009154:Mutation; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D009218:Myosins / Q000302:isolation & purification / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D013045:Species Specificity
D010761:Phosphorus Radioisotopes; D009219:Myosin-Light-Chain Kinase; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D009218:Myosins; D006152:Cyclic GMP