  Many biological functions rely on the reshaping of cell membranes, in
particular into nanotubes, which are covered in vivo by dynamic actin networks.
Nanotubes are subject to thermal fluctuations, but the effect of these on cell
functions is unknown. Here, we form nanotubes from liposomes using an optically
trapped bead adhering to the liposome membrane. From the power spectral density
of this bead, we study the nanotube fluctuations in the range of membrane
tensions measured in vivo. We show that an actin sleeve covering the nanotube
damps its high frequency fluctuations because of the network viscoelasticity.
Our work paves the way for further studies on the effect of nanotube
fluctuations in cellular functions.
