1: Proc Natl Acad Sci U S A  1999 Mar 2;96(5):2048-53 

Protrusive growth from giant liposomes driven by actin polymerization.

Miyata H, Nishiyama S, Akashi K, Kinosita K Jr.

Department of Physics, Faculty of Science and Technology, Keio University.
3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
miyata@bio.phys.tohoku.ac.jp

Development of protrusions in the cell is indispensable in the process of cell
motility. Membrane protrusion has long been suggested to occur as a result of
actin polymerization immediately beneath the cell membrane at the leading edge,
but elucidation of the mechanism is insufficient because of the complexity of
the cell. To study the mechanism, we prepared giant liposomes containing
monomeric actin (100 or 200 microM) and introduced KCl into individual liposomes
by an electroporation technique. On the electroporation, the giant liposomes
deformed. Most importantly, protrusive structure grew from the liposomes
containing 200 microM actin at rates (ranging from 0.3 to 0.7 micrometer/s)
similar to those obtained in the cell. The deformation occurred in a time range
(30 approximately 100 s) similar to that of actin polymerization monitored in a
cuvette (ca. 50 s). Concomitant with deformation, Brownian motion of
micron-sized particles entrapped in the liposomes almost ceased. From these
observations, we conclude that actin polymerization in the liposomes caused the
protrusive formation.

PMID: 10051592 [PubMed - indexed for MEDLINE]