title: Helical buckling of actin inside filopodia generates traction.
abstract: Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell-cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.
authors.affiliation: Niels Bohr Institute and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: Natascha
authors.initials: N
authors.lastname: Leijnse
authors.affiliation: Niels Bohr Institute and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: Lene B
authors.initials: LB
authors.lastname: Oddershede
authors.affiliation: Niels Bohr Institute and bendix@nbi.dk.
authors.forename: Poul M
authors.initials: PM
authors.lastname: Bendix
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D001696:Biomechanical Phenomena; D066146:Cell Body / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D011554:Pseudopodia / Q000378:metabolism*; D054159:Torsion, Mechanical
chemical_list: D000199:Actins
keywords: filopodia rotation; filopodial retrograde flow; helical buckling; membrane nanotubes; membrane–cytoskeleton interactions