Surface Immobilization of Viruses and Nanoparticles Elucidates Early Events in Clathrin-mediated Endocytosis.

Clathrin-mediated endocytosis (CME) is an important entry pathway for viruses. Here， we applied click chemistry to covalently immobilize reovirus on surfaces to study CME during early host-pathogen interactions. To uncouple chemical and physical properties of viruses and determine their impact on CME initiation， we used the same strategy to covalently immobilize nanoparticles of different sizes. Using fluorescence live microscopy and electron microscopy， we confirmed that clathrin recruitment depends on particle size and discovered that the maturation into clathrin-coated vesicles (CCVs) is independent from cargo internalization. Surprisingly， we found that the final size of CCVs appears to be imprinted on the clathrin coat at early stages of cargo-cell interactions. Our approach has allowed us to unravel novel aspects of early interaction between viruses and clathrin machinery that influence late stages of CME and CCVs formation. This method can be easily and broadly applied to the field of nanotechnology， endocytosis and virology.