# Berlin 2018 – wissenschaftliches Programm

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# BP: Fachverband Biologische Physik

## BP 16: Membranes and Vesicles I (joint session BP/CPP)

### BP 16.2: Vortrag

### Mittwoch, 14. März 2018, 09:45–10:00, H 1028

**Modeling the flat-to-curved transition during clathrin-mediated endocytosis** — •Felix Frey^{1}, Delia Bucher^{2}, Kem Sochacki^{3}, Justin Taraska^{3}, Steeve Boulant^{2}, and Ulrich Schwarz^{1} — ^{1}Institute for Theoretical Physics, Heidelberg University — ^{2}Department of Infectious Diseases, Virology, University Hospital Heidelberg — ^{3}NIH, Bethesda, U.S.A.

Clathrin-mediated endocytosis (CME) is essential for the cellular uptake of nutrients and receptors. Although CME has been studied for decades, the exact sequence of molecular and structural events remains elusive. Two basic models have been suggested for the way CME proceeds. (1) In the constant curvature model, it is assumed that clathrin-coated pits grow with constant curvature, determined by the geometry of clathrin triskelia. (2) In the constant area model, it is assumed that clathrin triskelia first assemble into flat hexagonal arrays that later invaginate with a constant surface area. This second model implicitly assumes that during bending, some hexagons are converted into pentagons. Here, we integrate data sets from correlative electron and light microscopy and quantify the sequence of ultrastructural rearrangements of the clathrin coat during endocytosis in mammalian cells with the help of some simple mathematical growth laws. Our analysis shows that clathrin-coated structures initially grow flat but start to acquire curvature when 70% of the final clathrin content is reached. Hence, our analysis suggests that elements of both suggested models are present and that mechanical and cellular factors will decide about the relative weights of growth versus curvature formation.