Hyperosmotic stress‐induced reorganization of actin bundles in Dictyostelium cells over‐expressing cofilin

Abstract

Background: Cofilin is a low-molecular weight actinmodulating protein, which binds to, severs, and depolymerizes actin filaments in vitro. Aip1, an actininteracting protein, was recently identified as a product of a gene on a multicopy plasmid which suppresses the temperature-sensitive phenotype of a cofilin mutant in Saccharomyces cerevisiae. Actin cytoskeleton plays an essential role in resistance to hyperosmotic stress in Dictyostelium discoideum. The roles of cofilin and Aip1 in this resistance are not known.

Actin Interacting Protein1 and Actin Depolymerizing Factor Drive Rapid Actin Dynamics inPhyscomitrella patens

“…Specifically, AIP1 and ADF function in a common pathway where AIP1 requires ADF for its function. This is strongly supported by biochemical data showing that AIP1 alone has minimal effects on actin filaments; however, in combination with ADF it synergistically enhances actin filament disassembly (Aizawa et al, 1999;Okada et al, 1999;Rodal et al, 1999). We also show AIP1-mCherry is diffusely cytosolic, similar to ADF (Augustine et al, 2008).…”

“…However, in the presence of ADF/cofilin, disassembly occurs at a higher rate than either protein alone (Aizawa et al, 1999;Okada et al, 1999;Rodal et al, 1999). While the mechanism of cooperative disassembly is still unclear, evidence supports a role for AIP1 in capping the barbed end of ADF/cofilin-severed actin filaments (Okada et al, 1999(Okada et al, , 2002(Okada et al, , 2006Balcer et al, 2003;Mohri et al, 2004), enhancing actin filament severing by ADF/cofilins (Aizawa et al, 1999;Mohri et al, 2004), or a combination of these mechanisms. AIP1's activity ultimately results in further fragmentation of ADF/cofilin-severed actin filaments (Aizawa et al, 1999;Okada et al, 1999;Okreglak and Drubin, 2010), showing that AIP1 functions in the turnover of F-actin.…”

Sphingosine 1-phosphate promotes endothelial cell barrier integrity by Edg-dependent cytoskeletal rearrangement

“…PAK dominant negative constructs completely abolished Sph-1-P-mediated actin rearrangement ( Figure 10) as well as cofilin translocation to the cortical actin ring (data not shown). Unphosphorylated cofilin severs and depolymerizes actin filaments in vitro, promoting rapid actin filament turnover in vivo (58)(59)(60)(61), whereas phosphorylation of cofilin at Ser 3 catalyzed by LIM kinase, a PAK phosphorylation target, reverses cofilin-induced actin depolymerization and leads to accumulation of actin filaments (44,61,62). We overexpressed the LIM kinase target, cofilin, in endothelial monolayers and subsequently analyzed barrier properties by measuring electrical impedance.…”

Aip1 and Cofilin Promote Rapid Turnover of Yeast Actin Patches and Cables: A Coordinated Mechanism for Severing and Capping Filaments

“…However, the cellular mechanism by which Aip1 functions has remained elusive, due in part to its biochemical activities being complex. Purified Aip1 alone has negligible effects on actin, but in the presence of cofilin it induces net disassembly of actin filaments (Aizawa et al, 1999;Okada et al, 1999;Rodal et al, 1999;Mohri et al, 2003). Two recent in vitro studies suggest that filament disassembly results from Aip1 capping the barbed ends of cofilin-severed filaments (Okada et al, 2002;Balcer et al, 2003).…”