Membrane proteomics of the Drosophila circadian neural network

The Drosophila brain contains approximately 240 pacemaker neurons that control circadian behaviors. Their molecular clocks are synchronized, but the phase of their rhythmic activity differs, so that specific groups of clock neurons can properly time various behaviors. To understand in depth how the circadian neural network functions, we surveyed its membrane proteome in the morning and evening, using in situ protein labeling coupled with mass spectrometry. We detected known regulators of circadian behavior and identified novel membrane or membrane-associated proteins in clock neurons. Through genetic screens, we found that many of these proteins regulate circadian behavior. In particular, Oct{beta}1R modulates evening locomotion under long photoperiod, while Piezo regulates morning activity under short photoperiod. Loss of Piezo alters rhythmic neuronal activity and compromises the structural plasticity of the neurons controlling locomotion at dawn. Our work thus illustrates the power of proteome-guided genetic screening to understand the mechanisms underlying circadian behavior.