| Summary: | <p>Recent work has demonstrated a role for Reactive Oxygen Species (ROS) in promoting sleep. In the Drosophila melanogaster brain, two dozen sleep-inducing neurons with projections to the dorsal fan-shaped body (dFB) integrate cumulative ROS burden over the duration of the day. The neurons’ exposure to ROS is thought to be integrated by the Kv channel Shaker’s β-subunit Hyperkinetic, whose oxidoreductase domain metabolises ROS-derived aldehydes with the help of a nicotinamide adenine dinucleotide phosphate (NADPH) co-factor. ROS exposure oxidises this co-factor to NADP+ and slows the inactivation of the Shaker-mediated A-type current, which is permissive of higher frequency neuronal activity and thereby aids sleep promotion. Typical models of homeostatic sleep posit that gradual integration of sleep promoting signals (e.g. ROS) must rapidly dissipate following sleep induction. However, the specific identity of ROS signalling molecules and how these signals are dissipated remains unclear.</p>
<p>Using whole cell in-vivo patch clamp recordings from dFB neurons, I demonstrate that lipid peroxidation products, such as 4-oxo-2-nonenal (4-ONE), readily interact with Hyperkinetic. 4-ONE significantly slows the A-type current inactivation and thus can act as potential physiological ROS derived messenger. Further, I show that integration of ROS molecules by Hyperkinetic can be dissipated by simulating high frequency activity within the dFB neurons. While producing a marked effect on A-type inactivation, the effects of intracellular 4-ONE in dFB neurons did not translate into an overall increased activity. Finally, assessing the sleep behaviour of a broad selection of Hyperkinetic mutants, possible amino acid residues of interest were identified as having a potential role in the long-term ROS signal integration capabilities of Hyperkinetic.</p>
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