The small actin-binding protein cofilin is a member of the ADF/cofilin protein family and has important roles in regulating actin dynamics. Recent studies have also implicated cofilin in the induction of apoptosis. On page , Campbell Gourlay and colleagues now identify additional functions for the actin modulator in the regulation of mitochondrial function. To examine the roles of cofilin, they make use of a library of S. cerevisiae strains expressing mutant forms of cofilin 1. These strains reveal a role for cofilin in the regulation of mitochondrial functions, including oxidative respiration and the production of reactive oxygen species (ROS), and in controlling organelle morphology and biogenesis. Specifically, mutations in cofilin that stabilise F-actin result in the hyperactivation of Ras and an associated increase in ROS production. Cofilin mutations that do not alter actin dynamics result in the upregulation of genes encoding ATP-binding cassette (ABC) transporters, which subsequently confer multi-drug resistance. The authors conclude that cofilin has a crucial role in regulating diverse cellular processes by affecting mitochondrial function. Furthermore, they propose that cofilin acts as a biosensor that allows cells to respond to specific external stimuli by connecting environmental changes to both the cytoskeleton and mitochondria.
