Cryptochrome and magnetosensitivity in Drosophila

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The precise biophysical origin of animal magnetoreception remains uncertain. Among the proposed primary magnetoreceptors is the flavoprotein CRYPTOCHROME (CRY), which is thought to provide geomagnetic information via a quantum effect in a light-initiated radical pair (RP) reaction. Our recent work shows that magnetosensitivity, in Drosophila, is maintained when just the CRY C-terminal (CRY-CT) is expressed. This seriously undermines the canonical RP model, which requires full-length CRY, as the main mechanism (not considering magnetite) to sense a magnetic field in vivo. Additionally, we have preliminary evidence that free FAD is able to sense a magnetic field in a cellular model and that CRY-CT amplifies such a mechanism, an avenue that we will pursue further in this application.

On this premise we suggest an alternative scenario to the canonical RP model to be tested in this proposal. Specifically, we suggest that independently of whether CRY may be acting as the primary magnetoreceptor (when full length) or not (as the CRY-CT fragment), identified amino acid motifs in the C-terminal end of the protein are crucial to bring the 'receptor' in to close proximity of the cellular effectors. Published and unpublished evidence suggest that alpha and beta K+ channels may be such effectors, but their role in magnetoreception has never been experimentally demonstrated before. This will be investigated in our proposal. Additionally, as the activity of beta K+ channels depend on cellular redox, we will test the impact of redox on the magnetoresponse. Finally, we will undertake an unbiased approach to identify potential partners of CRY and CRY-CT that might contribute to the magnetic response through additional and unexpected mechanisms.