Guanine Nucleotide Exchange Factor OSG-1 Confers Functional Aging via Dysregulated Rho Signaling in Caenorhabditis elegans Neurons

Abstract

Rho signaling regulates a variety of biological processes, but whether it is implicated in aging remains an open question. Here we show that a guanine nucleotide exchange factor of the Dbl family, OSG-1, confers functional aging by dysregulating Rho GTPases activities in C. elegans. Thus, gene reporter analysis revealed widespread OSG-1 expression in muscle and neurons. Loss of OSG-1 gene function was not associated with developmental defects. In contrast, suppression of OSG-1 lessened loss of function (chemotaxis) in ASE sensory neurons subjected to conditions of oxidative stress generated during natural aging, by oxidative challenges, or by genetic mutations. RNAi analysis showed that OSG-1 was specific toward activation of RHO-1 GTPase signaling. RNAi further implicated actin-binding proteins ARX-3 and ARX-5, thus the actin cytoskeleton, as one of the targets of OSG-1/RHO-1 signaling. Taken together these data suggest that OSG-1 is recruited under conditions of oxidative stress, a hallmark of aging, and contributes to promote loss of neuronal function by affecting the actin cytoskeleton via altered RHO-1 activity.

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

“…RHO-1 has been previously implicated in the response to oxidative stress of C. elegans , where, likewise the HS, its knock down was protective [12]. Indeed, exposure to 1.0 mM hydrogen peroxide (H 2 O 2 ) for 20 min [12] led to a 25% decrease in the amounts of F-actin in N2 worms (Fig.…”

“…1A. These GTPases function redundantly [16]) homologues of respectively RhoA, Cdc42 and Rac1 [17] by bacterial RNAi [12]. Notably, knock down of RHO-1 and CDC42 improved thermotolerance whereas RAC-2/CED-10/MIG-2 knock down did not affect survival.…”

“…Toward this end, we quantified F-actin by fluorimetry and densitometry in worms stained with phalloidin-rhodamine- (P-R, Figs 1B–1C) or in transgenic worms named P OSG-1 ::ABDmoe::mCherry (Figs. 1B–1D), that expressed F-actin binding protein moesin (moe) driven by the OSG-1 [12] promoter (P OSG-1 ). Both approaches revealed significant decreases in the levels of F-actin following a HS, thereby corroborating the notion that the integrity of the actin cytoskeleton is important for thermotolerance.…”

“…Rho signaling has been previously implicated in the response to oxidative stress [12] suggesting that its malfunctioning may represent a general factor of cellular vulnerability. Consistent with this emerging notion we further show the existence of a common mechanism in which Rho GTPase RHO-1 and CDC42 act in concert to decrease the levels of F-actin in the cell increasing susceptibility to stress.…”

Next-Generation Sequencing-Based Approaches for Mutation Mapping and Identification inCaenorhabditis elegans

“…Most modern genotypers can only detect indels of 5 bp and are incapable of detecting larger deletions or other forms of SV. Several bioinformatics tools have been developed that allow SVs to be identified, and most make use of paired-end reads (Abel and Duncavage 2013;Duan and Sesti 2015;Tattini et al 2015). The CloudMap pipeline uses genome coverage tools (such as Bedtools) to flag uncovered regions.…”