Aging affects circadian control of glutathione biosynthesis in Drosophila melanogaster. Eileen Chow¹, Vladimir Klichko², Joanna Kotwica-Rolinska^1,3, Dani Long¹, William Orr², Svetlana Radyuk², Jadwiga Giebultowicz¹. 1) Department of Zoology, Oregon State University, Corvallis, OR, USA; 2) Department of Biological Sciences, Southern Methodist University, Dallas, TX, USA; 3) Department of Animal Physiology, University of Warsaw, Warsaw, Poland.

   Circadian clocks control many biological processes that are vital to maintain health, including daily sleep/activity patterns and oscillations in neuronal, physiological, and metabolic functions. The focus of our work is to understand how clock-controlled processes are altered during aging in Drosophila melanogaster. We recently determined that levels of the major redox regulator glutathione (GSH) fluctuate in fly heads in a circadian manner. Significant rhythms were observed in the expression of genes encoding the catalytic (Gclc) and modulatory (Gclm) subunits of glutamate cysteine ligase (GCL), the rate-limiting enzyme in GSH biosynthesis, in the activity of the GCL, and expression of GstD1 (which utilizes GSH in cellular detoxification). The circadian system consists of ~150 central pacemaker neurons which control rest/activity rhythms, and so-called peripheral oscillators in many tissues such as retinal photoreceptors, glia, and fat body. We are mapping which circadian loci contribute to rhythmic expression of Gclc by disrupting clocks in specific cells such as Pdf positive neurons, glia, and photoreceptors. In addition, we investigate age-related changes in GSH biosynthesis, as we and others determined that aging is associated with dampened expression of clock genes and proteins. Our data suggests that rhythmic expression of Gclc and Gclm is impaired in old flies. We are testing whether loss of circadian regulation leads to a decline in GSH levels and compromised redox homeostasis by evaluating reduced and oxidized glutathione, and analyzing the profiles of protein mixed disulfides across lifespan. Our results should provide insights into relationships between the clock system and GSH, a compound which acts as a major antioxidant, regulates activity of detoxification enzymes, and mediates redox-sensitive signaling.