Genetic suppression of a phosphomimic myosin II identifies system-level factors that promote myosin II cleavage furrow accumulation.
Bottom Line: How myosin II localizes to the cleavage furrow in Dictyostelium and metazoan cells remains largely unknown despite significant advances in understanding its regulation.Analysis of several mutant strains revealed that different thresholds of myosin II activity are required for daughter cell symmetry than for furrow ingression dynamics.Finally, an engineered myosin II with a longer lever arm (2xELC), producing a highly mechanosensitive motor, could also partially suppress the intragenic 3xAsp.
Affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.Show MeSH
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Mentions: The genes that rescued 3xAsp myosin II furrow accumulation in the myoII- background might play an important role in myosin II assembly dynamics and/or in pathways involved in myosin II localization and may include “hypothetical receptors” that might be involved in recruiting myosin II to the cleavage furrow during cytokinesis. We focused on three proteins—RMD1, rcdBB, and mmsdh—which are among the top hits in the 3xAsp furrow localization rescue and suspension growth assays. We analyzed the subcellular localizations of these proteins by live-cell imaging of WT cells expressing N-terminal GFP- or mCherry-tagged fusion proteins. Suspension growth and 3xAsp furrow localization assays were repeated to confirm that these fusions did not impair protein function. Both GFP-RMD1 and GFP-mmsdh increased suspension growth of WT::3xAsp cells and rescued the 3xAsp furrow accumulation in myoII- cells (Figure 4A). These data are similar to those acquired for the non–fluorophore-tagged versions, confirming that the N-terminal GFP-fusion proteins were functional. We note that the C-terminal–labeled RMD1 protein lost its spindle localization, indicating that this fusion protein did not function normally.
Affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.