Stepping stone: a cytohesin adaptor for membrane cytoskeleton restraint in the syncytial Drosophila embryo.
Bottom Line: Elevating Sstn furrow levels had no effect on the steppke phenotype, but elevating Steppke furrow levels reversed the sstn phenotype, suggesting that Steppke acts downstream of Sstn and that additional mechanisms can recruit Steppke to furrows.Finally, the coiled-coil domain of Steppke was required for Sstn binding and in addition homodimerization, and its removal disrupted Steppke furrow localization and activity in vivo.Overall we propose that Sstn acts as a cytohesin adaptor that promotes Steppke activity for localized membrane cytoskeleton restraint in the syncytial Drosophila embryo.
Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.Show MeSH
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Mentions: The abnormal membrane expansion of step loss-of-function embryos was shown to be the result of Rho1 pathway and actomyosin overactivity through suppression experiments (Lee and Harris, 2013). To determine whether the abnormal membrane expansion of sstn loss-of-function embryos was due to similar misregulation, we reduced Rho1 pathway activity through rho1 mutant heterozygosity, as done previously (Lee and Harris, 2013). Maternal heterozygosity for rho172O substantially suppressed the sstn RNAi phenotype versus offspring of sibling mothers without the rho1 reduction (Figure 6A; quantified in Figure 6B). Thus Sstn seems to antagonize effects of the Rho1 pathway in a manner very similar to that of Step.
Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.