Mechanics of polyhedral clathrin cages

Clathrin-mediated-endocytosis is a remarkable process involving the formation of complex polyhedral protein structures to invaginate small (from 40 to 100 nm) clathrin coated vesicles (CCVs) from the cell membrane. These natural assemblies, made of 12 pentagons and up to 20 hexagons, show similarities with the tensegrity-based Buckminster Fuller architecture which suggest a prominent mechanical role for the clathrin coat. However, our atomic force microscopy experiments have showed that this comparison does not hold and that the measured polyhedral response cannot be explained by tension and compression alone. To further evaluate the structural performance of these protein cages, we modelled the various polyhedral shapes, including the non-linear loading by the AFM tip, with finite element analysis.