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Membrane Protrusion Driven by Actin
Polymerization
Protrusion
of
cell membranes, as occurs at the leading edge of a crawling cell, is
considered to be driven by polymerization of actin. Whether
polymerization alone is sufficient to drive this process, however, has
not been clear. Here we demonstrate, in a simple system of a
giant liposome containing actin monomers, that actin polymerization
indeed pushes out the lipid membrane into several
protrusions. The observed growth rate of ~0.5 μm/s
is comparable to the rate in living cells. In the three
movies, polymerization is initiated by KCl, which is introduced in the
liposomes by electroporation. Note, in the third movie, that
the movement of small vesicles inside the lipsomes ceases when
protrusive growth begins, presumably because actin filaments impede
their motion.
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