Ubiquitin Localization Changes as C. elegans Undergo Stress

Abstract

Muscle tissue is constantly undergoing protein turnover and reacts quickly to stress. Organisms have developed various mechanisms to help deal with stresses induced by their environment or other factors. The ubiquitin-proteasome degradation pathway has been shown to aid in the removal of misfolded or damaged proteins. Ubiquitination participates in tagging unwanted proteins for degradation and in other important signaling pathways such as endocytosis, cell cycle, histone modifications, etc. Ubiquitin, a highly conserved 76 amino acid protein, is the focus of our studies. Using confocal microscopy, we analyzed the localization of ubiquitin in aging, salt stressed and nutrient deprived muscle cells of Caenorhabditis elegans in the hopes of understanding the role ubiquitin has during stress induced conditions. Utilizing a GFP::Ub fusion protein and the unc-54 promoter, we have shown that ubiquitin is evenly distributed in unstressed muscle nuclei; however, muscle nuclei that undergo stress form nuclear foci. Our research shows that C. elegans exposed to high salt and nutrient deprivation induce foci formation within the muscle nuclei. We have shown that Ub foci also form as worms age. However, heat shock and cold shock do not cause the formation of nuclear foci. Furthermore, we have shown that intestinal cells also exhibit nuclear foci when exposed to stress, albeit at a slightly smaller frequency.