Signalling proteins are often segregated into specialized intracellular domains to ensure efficient signal transduction. In Drosophila photoreceptors, transient receptor potential-like (TRPL) channels are localized to the rhabdomere (a microvillus-rich part of the apical membrane that houses most of the light signalling components) and translocate to the basolateral membrane during long-term light adaptation. On , Susan Tsunoda and co-authors reveal that this translocation involves two steps. Within 5 minutes of light exposure, TRPL channels begin to move into the stalk membrane by a phospholipase-C-dependent process. This is part of the apical membrane; so the channels may diffuse laterally to their new position, possibly after release from an anchoring mechanism involving visual arrestin 2, which holds TRPL in the rhabdomere. In the second step, which takes >6 hours, the channels move to the basolateral membrane. This step depends on the other light-activated channel, TRP, and an eye-specific protein kinase C. Because adherens junctions separate the basolateral and stalk membranes, the authors suggest it may involve transport of the channels in vesicles.
