Essential for the homeostatic regulation of sleep and motor activity, by depressing hyperactivity and wakefulness. May function, at least in part, by ensuring dopamine biosynthesis. Localized to distinct puncta in neuronal cytoplasm. Detected in the brain (at protein level). Expressed in larval muscles. Adults display increased motor activity during locomotion, fragmented sleep and a decreased lifespan. Walking speed is not effected however flies spend more time moving with slightly fewer pauses resulting in longer uninterrupted bouts of walking. The total duration of sleep is not effected but average sleep bout length is decreased, the number of sleep bouts is increased and the amount of wake after sleep onset (WASO) is also increased. Dopamine levels are decreased by 50%. No effect on flight or climbing (negative geotaxis). RNAi-mediated knockdown in a large subset of dopaminergic neurons also results in fragmented sleep.