(464c) Investigating the Biomolecular Mechanisms of Membrane Fission By Clathrin during Endocytosis

The ability of proteins to sense membrane curvature is essential to cellular functions, including clathrin-mediated endocytosis (CME). The formation of the coated pit in CME is driven via recruitment of the clathrin triskelia to the membrane surface by adapter proteins that are known to sense regions of high membrane curvature. Clathrin itself has also been shown to sense curvature in the absence of adaptor proteins; a mechanism that is amplified by 2-to 10-fold when recruited by adapter proteins. Furthermore, many of the adaptor proteins can generate steric pressure that drives membrane vesiculation. However, the ability of clathrin to directly contribute to membrane bending has remained unknown. In this study, we use quantitative fluorescence microscopy and dynamic light scattering to examine membrane fission. We have used a synthetic affinity tag to assemble clathrin directly to small unilamellar vesicle (SUV) surfaces in the absence of adaptor proteins. By modulating clathrin’s ability to assemble, our data suggests that assembled clathrin lattices do indeed drive fission. Additionally, it’s unclear if clathrin has a direct membrane bending effects propagated through adaptor proteins or if the underlying protein network drives bending. To this end, we will probe clathrin’s ability to bend the membrane when recruited by its adaptor proteins Epsin-1 and Amphiphysin. This work will elucidate the mechanisms by which clathrin drives remodeling of lipid membranes and increase our understanding of its role in endocytosis.