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: To assess the properties of the Sstn, we conducted sequence analyses. The protein contained a predicted CC domain in its N-terminal region but had no other predicted domains (Figure 1A). BLAST searches identified a C-terminal conserved region (CR) with high identity to sequences in a number of predicted insect proteins (Figure 1, A–C). Bioinformatic analyses of these proteins revealed that they also contain a predicted N-terminal CC domain (Figure 1A). Moreover, the proteins from monarch butterflies (Danaus plexippus) and leaf-cutter ants (Acromyrmex echinatior) were previously annotated as FRMD4A-like proteins, although they lack the FERM domain of FRMD4A. For these proteins, our BLAST analyses revealed that their top Drosophila hit was Sstn, whereas their top human hit was a predicted FRMD4A isoform (Figure 1B). Their similarity with Sstn occurs in the CR, as mentioned, but their similarity with human FRMD4A occurs within their CC domains (color coding in Figure 1B).
Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.