Peroxiredoxinylation; a new post-translational modification promoting redox signal transduction?

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All oxygen-using organisms inevitably encounter reactive oxygen species (ROS), produced by a multitude of exogenous and endogenous sources. ROS can be extremely damaging, hence highly conserved mechanisms have evolved to prevent this damage. In yeast, plants and animal cells, these include activating conserved signalling pathways, such as p38/JNK MAPK pathways, that initiate a variety of responses, including increasing the levels of protective proteins. However, ROS have many other signalling functions in these organisms too; promoting wound healing, root tip growth, movement of cancer cells etc through effects on cell growth, division, differentiation and migration. Moreover, although oxidative damage is a general hallmark of many diseases and ageing, small increases in ROS are actually essential for the pro-longevity effects of dietary restriction/changes in mitochondrial activity. This discovery has challenged the theory that ROS cause ageing and led to the current view that localised ROS signals are able to protect against ageing and age-associated diseases. Nevertheless, despite the ever-increasing number of important biological processes in which ROS signals are implicated, there remain big gaps in our understanding of how these ROS signals are actually sensed and transmitted. For instance, in most cases, the identity of the ROS-regulated signalling proteins, and the mechanisms by which ROS regulate their activity are both unknown. This work will address these questions, exploiting the well-established advantages of yeast (Schizosaccharomyces pombe) and microscopic nematode worms (Caenorhabditis elegans) as powerful model systems for studying the mechanisms involved in regulating cell division, ROS responses and ageing.The applicant's previous work has established important roles for ubiquitous, peroxide-reactive proteins, 2-Cys peroxiredoxins (Prx), in promoting ROS-signalling and longevity in yeast and worms. Importantly, ROS-signalling and anti-ageing functions have been found to be shared by Prx in mammals and plants, illustrating the value of studies in these models for identifying conserved ROS-signalling and pro-longevity mechanisms. However, the mechanisms underlying many of the ROS-signalling and pro-longevity functions of Prx have yet to be uncovered. Pilot data: Our approach to identify ROS-regulated target proteins has identified a number of proteins that form ROS-induced disulphide-bonded complexes with Prx. These Prx-complexed proteins include multiple components of a p38-related MAPK signalling pathway, that plays a key role in coordinating responses to environmental/metabolic stimuli. Here we will test the hypothesis that the formation of these reversible chemical bonds with a Prx, or 'peroxiredoxinylation', represents a new protein modification, regulating these proteins and thus mediating many of the physiological effects of ROS. By establishing how Prx regulates these signalling proteins, we hope to establish a new paradigm for how ROS signals are transduced into cell responses. We will use yeast and worms containing mutant versions targeting specific activities to determine which of Prx's functions require its ability to form disulphide complexes with (or 'peroxiredoxinylate') other proteins, or to come together to form stackable, doughnut-like ring structures. For instance, we will determine whether 'peroxiredoxinylation' or the ability of Prx to form these ring structures is important for Prx's anti-ageing function. This will be important for understanding how the new mechanisms we have identified contribute to some of the beneficial effects of ROS e.g.on ageing. Indeed, we expect this work to fill a significant gap in our current understanding of how ROS effect many biological responses.