Myosin II redistribution during rear retraction and the role of filament assembly and disassembly.
The literature to date suggests a role for myosin II in rear retraction, including evidence that myosin undergoes a characteristic 'C'-to-spot redistribution at the cell posterior which is associated with retraction. Here we investigate the mechanism of both retraction and the'C'-to-spot using Dictyostelium cells containing mutant forms of myosin that affect its polymerization. 3 x Asp-myosin forms few if any filaments. When 3 x Asp cells are added to a wild-type mound, the mutant cells move directionally, but rear retraction is markedly delayed,demonstrating that myosin II filaments are essential for efficient retraction. In addition, using a GFP-tagged 3 x Asp-myosin, we observed a posterior spot pattern associated with retraction,but no cortical 'C' pattern preceding it. This suggests that filamentous myosin is required to produce the 'C', and that its failure to form results in defective rear retraction. In contrast, an alternate mutant myosin that forms filaments constitutively, 3 x Ala-myosin, forms 'Cs' and then spot patterns at the posterior, but in the interim the spots do not disintegrate. This suggests that spot dissolution occurs by filament depolymerization. In summary our data demonstrate a role for myosin II and the 'C'-to-spot in efficient rear retraction, and define filament assembly as critical for formation of the 'C' and filament disassembly as critical for dissolution of the spot.
Koehl
Gudrun
G
Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, Bethesda, MD 20892, USA.
McNally
James G
JG
D008841:Actin Cytoskeleton / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D004023:Dictyostelium; D018613:Microscopy, Confocal; D024462:Myosin Type II / Q000172:deficiency / Q000378:metabolism*
D024462:Myosin Type II