Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Wednesday Speaker Abstracts

ATP-DEPENDENT MEMBRANE REMODELING LINKS EHD1 FUNCTIONS TO ENDOCYTIC RECYCLING Thomas J. Pucadyil 1 ; Raunaq Deo 1 ; Manish Kushwah 1 ; Nagesh Kadam 2 ; Kavita Babu 2 ; Anand Srivastava 3 ;

1 IISER Pune, Pune, Maharashtra, India 2 IISER Mohali, Mohali, Punjab, India 3 Indian Institute of Science, Bengaluru, Karnataka, India

Endocytic and recycling pathways generate cargo-laden transport carriers by membrane fission. Classical dynamins, which generate transport carriers during endocytosis, are known to constrict the membrane and cause fission in response to GTP hydrolysis. Relatively, less is known about the ATP-binding Eps15-homology domain-containing protein1 (EHD1), a dynamin family member that localizes to the endocytic-recycling compartment (ERC). Using cross complementation assays in C. elegans, we find that EHD1's membrane binding and ATP hydrolysis activities are necessary for endocytic recycling. In reconstitution assays, a preference for high positive membrane curvature directs EHD1 to bind and organize into membrane-active scaffolds that bulge the tube. Reactions with ATP promote self-assembly of the scaffold, which propagates the bulge along the length of the tube causing intermediate regions to thin down. On tubes below 25 nm in radius, such thinning leads to scission. Coarse-grained molecular dynamics simulations corroborate this pathway to fission. N-terminal residues in EHD1 are important since their absence renders membrane bulges to catastrophically disappear in presence of ATP leading to defects in stable scaffolding, scission and endocytic recycling. Due to its significantly lower ATPase activity, the closely related ortholog EHD2 is dramatically less effective in membrane remodeling. Thus, ATP hydrolysis-dependent membrane remodeling links EHD1 functions to endocytic recycling.

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