Receptor for PDF, a neuropeptide controlling circadian behavioral rhythms. Probably regulates circadian behavioral rhythms through coordination of activities of clock neurons. PDF-binding results in the elevation of cAMP synthesis. Plays a role in sleep regulation and regulates the state transition from sleep to wake (PubMed:19038223, PubMed:19230663). Mainly present in clock neurons of the brain. Localizes in all 4 s-LNv neurons, 1 LNd neuron, 7 DN1 neurons, and 1 DN3 neuron. In addition to the clock neurons, it is also present in approximately 13 pairs of neurons along the ventral nerve cord in third instar larvae, which do not overlap with dopaminergic or serotonergic neurons. Not present in DN2 neurons (at protein level). Not expressed in embryos. Does not exhibit diurnal or circadian variation. RNAi-mediated knockdown in small and large ventral lateral neurons increases total sleep in both the day-time and the nighttime and decreases sleep latency during daytime only. Belongs to the G-protein coupled receptor 2 family.