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
Mentions: Because we found that the Sstn–Step interaction required the CC domains of each protein, we performed a final set of in vivo experiments interrogating the CC domain of Step. Specifically, we compared GFP-Step with a derivative in which the CC domain was deleted, expressing them from the same genomic site with the Gal-4-UAS system. First, we assessed in vivo associations with a mCh-tagged Sstn construct. Coexpression of GFP-Step with mCh-Sstn led to increased furrow abundance of both proteins versus single-expression controls (Figure 8A), as observed for proteins with the reciprocal tags (Figure 4A). In contrast, coexpression of GFP-Step∆CC with mCh-Sstn did not enhance the furrow level of either protein (Figure 8A).
Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.