Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Tuesday Speaker Abstracts

EVOLUTIONARY CELL BIOLOGY APPROACH TO CLATHRIN-MEDIATED ENDOCYTOSIS

Marko Kaksonen 1 ; Andrea Picco 1 ; Christopher P Toret 1 ; Anne-Sophie Rivier-Cordey 1 ; 1 University of Geneva, Department of Biochemistry, Geneva, Switzerland

Clathrin-mediated endocytosis is an ancient trafficking pathway that is conserved throughout eukaryotes. However, the molecular mechanisms of this process have diverged significantly in different eukaryotic lineages. We know relatively little about the molecular changes and the evolutionary pathways that have given rise to these mechanistic differences in endocytosis. We aimed to quantitatively characterize phenotypic differences in the endocytic process across different species to gain understanding of how cell level processes can evolve. We chose three distantly related fungal species as model organisms: Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Ustilago maydis. These species are highly amenable to genetic manipulation and can be grown as single celled yeasts under similar conditions, thus providing a powerful model clade for evolutionary cell biology. We focused on analyzing the assembly sequence of the endocytic protein machinery and the dynamics of the membrane invagination growth. We used quantitative live-cell imaging to compare the assembly dynamics and movements of seven groups of orthologous endocytic proteins tagged with fluorophores. Our data has revealed unexpected interspecies diversity in protein assembly dynamics throughout the different stages of endocytosis from initiation to the final vesicle budding. We also found that the endocytic invaginations grow to different lengths in these species, possibly resulting in vesicles of different sizes. We have started to dissect the molecular mechanisms behind the differences in endocytic phenotypes and aim to map the evolutionary pathways leading to these differences.

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