Cofilin-2, a novel type of cofilin, is expressed specifically at aggregation stage of Dictyostelium discoideum development.
BACKGROUND
A conventional cofilin, cofilin-1 in Dictyostelium discoideum plays significant roles in cell proliferation, phagocytosis, chemotactic movement and macropinocytosis.


RESULTS
We identified a new member of the cofilin family, named cofilin-2 in D. discoideum. Cofilin-2 shows significant homology to a conventional Dictyostelium cofilin, cofilin-1, through its entire sequence, and contains residues conserved among the cofilin family that are responsible for actin-binding. On the other hand, several residues that are conserved among the cofilin family are missing from cofilin-2. Purified cofilin-2 depolymerized actin filaments in a dose- and pH-dependent manner and reduced the apparent viscosity of an actin solution, although they did not co-sediment with actin filaments at all. Cofilin-2 was not expressed in vegetative cells, but was transiently induced during the aggregation stage of development, whereas cofilin-1 was predominantly expressed in vegetative cells. Immunocytochemistry revealed that cofilin-2 localizes at substrate adhesion sites, where cofilin-1 is almost completely excluded. Disruption of the cofilin-2 gene caused an increase in actin accumulation at the substrate adhesion sites. We also found that cofilin-2 did not rescue Deltacof1 yeast cells, whereas cofilin-1 did.


CONCLUSIONS
Cofilin-2 may play a distinct role from that of cofilin-1 in destabilization of the actin cytoskeleton during Dictyostelium development.
Aizawa
H
H
Department of Cell Biology, Electron Microscopy Center, The Tokyo Metropolitan Institute of Medical Science, Honkomagome 3-18-22, Bunkyo-ku, Tokyo 113-8613, Japan.
Kishi
Y
Y
Iida
K
K
Sameshima
M
M
Yahara
I
I
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion; D051340:Cofilin 2; D003599:Cytoskeleton / Q000378:metabolism; D004023:Dictyostelium / Q000235:genetics* / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D017386:Sequence Homology, Amino Acid; D015003:Yeasts / Q000235:genetics
D051339:Actin Depolymerizing Factors; D000199:Actins; D051340:Cofilin 2; D008840:Microfilament Proteins