H Aizawa1, Y Kishi, K Iida, M Sameshima, I Yahara. 1. Department of Cell Biology, Electron Microscopy Center, The Tokyo Metropolitan Institute of Medical Science, Honkomagome 3-18-22, Bunkyo-ku, Tokyo 113-8613, Japan.
Abstract
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.
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.
Authors: María Galardi-Castilla; Barbara Pergolizzi; Gareth Bloomfield; Jason Skelton; Al Ivens; Robert R Kay; Salvatore Bozzaro; Leandro Sastre Journal: Dev Biol Date: 2008-01-31 Impact factor: 3.582