Cryptochrome interaction networks across different tissues in Drosophila melanogaster

Drosophila CRYPTOCHROME (dCRY) is a blue light-sensitive protein involved in various biological processes, including photoreception, circadian rhythm regulation, synaptic plasticity, and magnetoreception. Its circadian function is strictly connected with light: upon light exposure, dCRY undergoes a conformational change, becoming active and binding to various proteins. However, it can also form complexes in the absence of light, with its function varying depending on the cell type in which it is expressed. Here, we use an experimental approach based on co-immunoprecipitation followed by mass spectrometry analysis, obtaining the in vivo interactome of dCRY in two distinct cell populations - retina photoreceptors and glial cells - at two specific time points: just before lights-on (ZT0) and one hour after lights-on (ZT1). To gain deeper insights into the functional dynamics of dCRY, we constructed reliable protein-protein interaction networks in both cell types and across the two experimental conditions, revealing a complex landscape of interactions. Additionally, we explored the biological pathways associated with the identified dCRY interactors, highlighting several tissue- and time-specific enrichments. We focused on RNA-related pathways, indicating that dCRY and its interactors are involved in regulating RNA metabolism in photoreceptors at ZT0 and in glial cells at ZT1. Finally, as a case study, we further investigated the functions of the RNA-binding protein SQUID, found to interact with dCRY in both tissues. Notably, the impaired circadian locomotor behavior exhibited by Squid mutant flies accounts for the involvement of this hnRNP in the generation of the circadian rhythmicity. In conclusion, our work provides the first tissue- and time-specific dCRY interactome, offering valuable insights into previously unrecognized biological processes in which it may be involved. Specifically, its potential role in the regulation of RNA metabolism contributes crucial evidence concerning the relationship between the circadian clock and RNA metabolism, thereby laying the groundwork for future research in this area.