Cytoskeletal remodeling via Rho GTPases during oxidative and thermal stress in Caenorhabditis elegans.

Biological systems are highly sensitive to changes in their environment. Indeed, the molecular basis of the environmental stress response suggests that the specialized stress responses share more commonalities than previously believed. Here, we used the nematode C. elegans to gain insight into the role of Rho signaling during two common environmental challenges, oxidative and thermal stress. In response to heat shock (HS), wild type (N2) worms demonstrated reduced viability which was rescued by genetic suppression of CDC42 and RHO-1. Visualization of F-actin by phalloidin-rhodamine underscored a strict correlation between the levels of F-actin following GTPase suppression and survival. Additionally, genetic ablation of OSG-1, a Guanine Nucleotide Exchange Factor (GEF) previously implicated in oxidative stress, was associated with constitutively lower levels of F-actin and increased mortality. However, upon an oxidative insult F-actin stability decreased in N2 worms, a rescue of this affect was observed in OSG-1 null worms, consistent with the resistance exhibited by these worms to oxidative stress (OS). Together these data suggest that during conditions of thermal or oxidative stress Rho signaling promotes vulnerability by altering actin dynamics. Thus, the stability of the actin cytoskeleton, in part through a conserved mechanism mediated by Rho signaling, is a crucial factor for the cell's survival to environmental challenges.