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: To investigate the pathway relationship between Sstn and Step, we tested how they affect each other's localization and RNA interference (RNAi) phenotypes. For GFP-Sstn, we observed similar local levels of the protein at the base of furrows in control embryos and in step RNAi embryos with abnormal perpendicular expansion of furrow tips (Figure 7A). Thus it seems that Step is not essential for the localization of overexpressed Sstn. Moreover, the Sstn overexpression could not overcome the effects of Step loss. Sstn overexpression also had no noticeable effect on otherwise genetically wild-type syncytial embryos.
Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.