title: Myosin I phosphorylation is increased by chemotactic stimulation.
abstract: Directed cell migration occurs in response to extracellular cues. Following stimulation of a cell with chemoattractant, a significant rearrangement of the actin cytoskeleton is mediated by intracellular signaling pathways and results in polarization of the cell and movement via pseudopod extension. Amoeboid myosin Is play a critical role in regulating pseudopod formation in Dictyostelium, and their activity is activated by heavy chain phosphorylation. The effect of chemotactic stimulation on the in vivo phosphorylation level of a Dictyostelium myosin I, myoB, was tested. The myoB heavy chain is phosphorylated in vivo on serine 322 (the myosin TEDS rule phosphorylation site) in chemotactically competent cells. The level of myoB phosphorylation increases following stimulation of starving cells with the chemoattractant cAMP. A 3-fold peak increase in the level of phosphorylation is observed at 60 s following stimulation, a time at which the Dictyostelium cell actively extends pseudopodia. These findings suggest that chemotactic stimulation results in increased myoB activity via heavy chain phosphorylation and contributes to the global extension of pseudopodia that occurs prior to polarization and directed motility.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Gliksman
authors.forename: G
authors.initials: G
authors.lastname: Santoyo
authors.forename: K D
authors.initials: KD
authors.lastname: Novak
authors.forename: M A
authors.initials: MA
authors.lastname: Titus
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002630:Chemotactic Factors / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004023:Dictyostelium / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D018995:Myosin Heavy Chains / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism
chemical_list: D002630:Chemotactic Factors; D010768:Phosphoserine; D000242:Cyclic AMP; D018995:Myosin Heavy Chains; D009218:Myosins