Overexpression of cofilin stimulates bundling of actin filaments, membrane ruffling, and cell movement in Dictyostelium.
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.
Aizawa
H
H
Department of Cell Biology, Tokyo Metropolitan Institute of Medical Science, Japan.
Sutoh
K
K
Yahara
I
I
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D002458:Cell Fractionation; D002462:Cell Membrane / Q000502:physiology; D002465:Cell Movement; D017931:DNA Primers; D018076:DNA, Complementary; D004023:Dictyostelium / Q000166:cytology / Q000502:physiology*; D015870:Gene Expression; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000502:physiology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000302:isolation & purification / Q000502:physiology; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism
D051339:Actin Depolymerizing Factors; D000199:Actins; D017931:DNA Primers; D018076:DNA, Complementary; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins