Uekusa, Y. | Search bioRxiv

bioRxiv2024

Enhanced Visualization of Influenza A Virus Entry Using Virus-View Atomic Force Microscopy

Virus entry begins with attachment of virions to the cell surface, multivalent binding of viral proteins to receptors, signaling, and endocytosis. Using ViViD-AFM (Virus-View Dual confocal and Atomic Force Microscopy), we visualized the nanoscale morphology of influenza A virus (IAV) virions interacting with the cell membrane during virus entry. Following attachment to the cell surface, spherical IAV (90-100 nm in diameter) diffused in a sialic acid- and neuraminidase-dependent manner. Reduced diffusion signified the onset of clathrin coat assembly, followed by formation of actin-rich ruffles that promoted pit closure and IAV endocytosis. Cell surface ruffles sheared filamentous IAV (>1{micro}m in length) into shorter fragments that became internalized. ViViD-AFM is a powerful tool that provides nanoscale morphological insights of virus-cell membrane interplay in living cells.

cell biology↗

bioRxiv2017

Morphological changes of plasma membrane and protein assembly during clathrin-mediated endocytosis

Clathrin-mediated endocytosis (CME) proceeds through a series of morphological changes of the plasma membrane induced by a number of protein components. Although the spatiotemporal assembly of these proteins has been elucidated by fluorescence-based techniques, the protein-induced morphological changes of the plasma membrane have not been fully clarified in living cells. Here we visualize membrane morphology together with protein localizations during CME by utilizing high-speed atomic force microscopy combined with a confocal laser scanning unit. The plasma membrane starts to invaginate ~30 seconds after clathrin starts to assemble, and the aperture diameter increases as clathrin accumulates. Actin rapidly accumulates around the pit and induces a small membrane swelling, which within 30 seconds rapidly covers the pit irreversibly. Inhibition of actin turnover abolishes the swelling and induces a reversible open-close motion of the pit, indicating that actin dynamics are necessary for efficient and irreversible pit closure at the end of the CME.

cell biology↗