|Aizawa, H., Sutoh, K.
& Yahara, I. (1996) Overexpression of cofilin stimulates bundling of
actin filaments, membrane ruffling and cell movement in Dictyostelium. J.
Cell Biol. 132, 335-344.
|Cofilin is a low molecular weight
actin-modulating protein whose structure and function are conserved
among eucaryotes. Cofilin exhibits in vitro both a monomeric
actin-sequestering activity and a filamentous actin-severing activity.
To investigate in vivo functions of cofilin, cofilin was overexpressed
in Dictyostelium discoideum cells. An increase in the content of D.
discoideum cofilin (d-cofilin) by sevenfold induced a co-overproduction
of actin by threefold. In cells over-expressing d-cofilin, the amount of
filamentous actin but not that of monomeric actin was increased.
Overexpressed d-cofilin co-sedimented with actin filaments, suggesting
that the sequestering activity of d-cofilin is weak in vivo. The
overexpression of d-cofilin increased actin bundles just beneath
ruffling membranes where d-cofilin was co-localized. The overexpression
of d-cofilin also stimulated cell movement as well as membrane ruffling.
We have demonstrated in vitro that d-cofilin transformed latticework of
actin filaments cross-linked by alpha-actinin into bundles probably by
severing the filaments. D. discoideum cofilin may sever actin filaments
in vivo and induce bundling of the filaments in the presence of
cross-linking proteins so as to generate contractile systems involved in
membrane ruffling and cell movement.