On the mechanical stabilization of filopodia

Alexandra Zidovska, Erich Sackmann

    Research output: Contribution to journalArticlepeer-review


    We studied force-induced elongation of filopodia by coupling magnetic tweezers to the tip through the bacterial coat protein invasin, which couples the force generator to the actin bundles (through myosin X), thus impeding the growth of the actin plus end. Single force pulses (15-30 s) with amplitudes between 20 and 600 pN and staircase-like force scenarios (amplitudes, ∼50 pN; step widths, 30 s) were applied. In both cases, the responses consist of a fast viscoelastic deflection followed by a linear flow regime. The deflections are reversible after switching off the forces, suggesting a mechanical memory. The elongation velocity exhibits an exponential distribution (half-width <v1/2>, ∼0.02 μms-1) and did not increase systematically with the force amplitudes. We estimate the bending modulus (0.4 × 10 -23 J m) and the number of actin filaments (∼10) by analyzing filopodium bending fluctuations. Sequestering of intracellular Ca2+ by BAPTA caused a strong reduction in the amplitude of elongation, whereas latrunculin A resulted in loss of the elastic response. We attribute the force-independent velocity to the elongation of actin bundles enabled by the force-induced actin membrane uncoupling and the reversibility by the treadmilling mechanism and an elastic response.

    Original languageEnglish (US)
    Pages (from-to)1428-1437
    Number of pages10
    JournalBiophysical journal
    Issue number6
    StatePublished - Mar 16 2011

    ASJC Scopus subject areas

    • Biophysics


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