Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Monday Speaker Abstracts

MECHANISTIC ANALYSIS OF MEMBRANE FISSION AND DISCOVERY OF NOVEL FISSION PROTEINS

Thomas J. Pucadyil ; 1 Indian Institute of Science Education and Research, Pune, Biology, Pune, India

The lipid bilayer is highly resilient to rupture and explains why it was selected over the course of evolution to serve a barrier function. Yet fission, or the splitting of a membrane compartment, is a central theme in biology that manifests during cell division, organelle biogenesis and vesicular transport. Fission involves the local application of forces to bend and constrict a tubular membrane intermediate. Using a facile assay system of supported membrane nanotubes that can be tuned for size and lipid composition, we have analyzed fission mechanisms of candidate proteins and discovered novel proteins that catalyze fission. My talk will describe recent developments in our efforts at understanding the pathway to fission and expanding the repertoire of fission proteins.

HARNESSING ACTIN ASSEMBLY FORCES TO DRIVE VESICLE FORMATION DURING CLATHRIN-MEDIATED ENDOCYTOSIS

David G. Drubin ; Daniel G Serwas 1 ; Jennifer G Hill 1 ; Matt Akamatsu 1 ; Ross Pedersen 1 ; 1 UC Berkeley, Molecular and Cell Biology, Berkeley, CA, USA

From yeast to humans, forces generated by the actin cytoskeleton assist in formation of clathrin coated vesicles during endocytosis. While the principles for how actin assembly generates pushing forces for cell motility have been well established, how actin assembly generates pulling forces for vesicle formation is not well understood. Studies conducted examined the ultrastructure of the actin cytoskeleton at endocytic sites, and investigated how cross-linking proteins, myosins and a force-sensitive coat protein, Hip1R/Sla2, generate pulling forces. Single molecule biophysics shows that the myosin is an active motor that generates pulling force. Actin assembly in mammalian cells is asymmetric at endocytic sites, while in yeast assembly occurs uniformly around the endocytic site. When membrane tension increases, load adaptation mechanisms increase actin assembly, suggesting coupling between force-sensing proteins and the actin assembly machinery. An integrated model for how actin mediates endocytic vesicle formation will be presented.

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