Time-dependent membrane proteomics in circadian pacemaker neurons

About This Grant

Project summary Circadian clocks optimize metabolism, physiology and behavior with the time-of-day. Thus, they play a key role in human health and well-being, and their disruption is associated with increased risks of mental disorders, metabolic diseases and cancers. Circadian pacemaker neurons, located in the brain, determine the timing of essential behaviors such as the sleep-wake cycle and feeding. These neurons express core circadian proteins, which form a network of transcriptional feedback loops that determines the timing of gene expression. Interestingly, in Drosophila, these neurons show synchronized oscillations of their circadian molecular clock, but also extraordinarily diverse phases of neural activity between functional groups of neurons. For example, the M-cells, which drive morning behavior, are mostly active at dawn. On the other hand, the E-cells, which promote evening activity, fire action potentials preferentially at dusk. This diversity in temporal neural activity is essential for determining the timing of behaviors, but it raises a fundamental question: how can synchronized circadian clocks generate desynchronized neural activity rhythms? Our hypothesis is that local circadian clocks regulate the time-dependent and neuron-specific expression of membrane proteins such as ion channels and receptors. To identify these proteins, we propose to use cutting-edge proteomic approaches combined with biotin proximity labeling to survey the membrane proteome of circadian neurons during the day/night cycle. The function of rhythmic membrane proteins will be tested in circadian behavior and sleep screens. This project should thus shed light on the mechanisms by which circadian clocks determine the temporal patterns of neural activity in diverse populations of pacemaker neurons, and thus the timing of behavior. It will also considerably help with the development of novel proteomic approaches that should be broadly applicable to study circadian rhythms and other neural processes in various species. Moreover, since the mechanisms underlying circadian rhythms are highly conserved in animals, our work could ultimately help understanding how the timing of the sleep/wake cycle is determined in humans and contribute to the design of therapeutic approaches aimed at alleviating ailments associated with circadian disruption.