BAR scaffolds drive membrane fission by crowding disordered domains

Wilton T. Snead; Wade F. Zeno; Grace Kago; Ryan W. Perkins; J Blair Richter; Chi Zhao; Eileen M. Lafer; Jeanne C. Stachowiak

If BAR scaffolds drive membrane fission by concentrating large disordered domains at membrane surfaces, then the ability of Amph-FL to drive fission (Figs. 1 and 2) should extend to other proteins that contain both BAR domains and substantial regions of intrinsic disorder. Interestingly, many proteins that contain the modestly-curved F-BAR domain also have this architecture (Roberts-Galbraith and Gould, 2010), including the endocytic proteins FCHo1/2 (Henne et al., 2010) and its yeast homolog Syp1 (Reider et al., 2009) , the srGAP proteins involved in neuronal development (Wuertenberger and Groemping, 2015) , and the cytokinesis proteins Cdc15 and Imp2 (McDonald et al., 2016) in S. pombe and Hof1 (Meitinger et al., 2011) in S. cerevisiae. To test this idea, we examined FCHo1 (C. elegans), which consists of an Nterminal F-BAR domain followed by an intrinsically disordered domain of 412 amino acids and a C-terminal µ-homology domain (Henne et al., 2010; Ma et al., 2016; Umasankar et al., 2014; Wang et al., 2016) (Fig. 5E ). Negative stain TEM revealed that exposure of vesicles with an initial average diameter of 200 nm to the F-BAR domain of FCHo1 drove formation of lipid tubules with an average diameter of 21±2 nm s.d. (Fig. 5F ,G and S5A,B), in agreement with previous findings (Henne et al., 2010; Henne et al., 2007) . In contrast, full-length FCHo1 (FCHo1-FL) did not generate lipid tubules, but instead divided the 200 nm diameter vesicles into a population of highly curved vesicles with average diameter 17±7 nm s.d. (Fig. 5H and S5C,D) .