Actin‐ADF/cofilin rod formation in Caenorhabditis elegans muscle requires a putative F‐actin binding site of ADF/cofilin at the C‐terminus

Abstract

Under a number of stress or pathological conditions, actin and actin depolymerizing factor (ADF)/cofilin form rod‐like structures that contain abnormal bundles of actin filaments that are heavily decorated with ADF/cofilin. However, the mechanism of actin rod formation and the physiological role of actin rods are not clearly understood. Here, we report that overexpression of green fluorescent protein‐fused UNC‐60B, a muscle‐specific ADF/cofilin isoform, in Caenorhabditis elegans body wall muscle induces formation of rod‐like structures. The rods contained GFP‐UNC‐60B, actin‐interacting protein 1 (AIP1), and actin, but not other major actin‐associated proteins, thus resembling actin‐ADF/cofilin rods found in other organisms. However, depletion or overexpression of AIP1 did not affect formation of the actin‐GFP‐UNC‐60B rods, suggesting that AIP1 does not play a significant role in the rod assembly. Truncation of the C‐terminal tail, a putative F‐actin binding site, of UNC‐60B abolished induction of the rod formation, strongly suggesting that stable association of UNC‐60B with F‐actin, which is mediated by its C‐terminus, is required for inducing actin‐ADF/cofilin rods. This study suggests that C. elegans can be a new model to study functions of actin‐ADF/cofilin rods. Cell Motil. Cytoskeleton 66: 398–408, 2009.