Single-Molecule Approaches to Membrane Nanotubes

Abstract

Membrane nanotubes (MNT) are thin (50∼200 nm in diameter), long-ranged (< hundreds of micrometer) membrane tubes that are formed by a physical connection between actin-driven protrusions from cell surfaces, which expedite intercellular communications between cells. However, the process of formation of MNTs that are heterogeneous even in the same cell type has been poorly understood. To explore the dynamic formation of MNTs, we visualized and manipulated MNTs in real time using single-molecule fluorescence imaging combined with optical tweezers. Real-time pulling and imaging a MNT attached to beads optically trapped revealed the detailed mechanical properties of how two protrusive F-actin bundles are connected. We also followed individual epidermal growth factor receptor (EGFR) on MNTs in various living cells, which allows for studying the mechanics of the transport of ligand-receptor signaling through MNTs. We will present how we achieved the single molecule tracking of receptors moving along a MNT that is placed in 3D space without interrupting the bead trapping.