Light-dependent subcellular translocation of Gqα in Drosophila photoreceptors is facilitated by the photoreceptor-specific myosin III NINAC

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Abstract
We examine the light-dependent subcellular translocation of the visual Gqα protein between the signaling compartment, the rhabdomere and the cell body in Drosophila photoreceptors. We characterize the translocation of Gqα and provide the first evidence implicating the involvement of the photoreceptor-specific myosin III NINAC in Gqα transport. Translocation of Gqα from the rhabdomere to the cell body is rapid, taking less than 5 minutes. Higher light intensities increased the quantity of Gqα translocated out of the rhabdomeres from 20% to 75%, consistent with a mechanism for light adaptation. We demonstrate that translocation of Gqα requires rhodopsin, but none of the known downstream phototransduction components, suggesting that the signaling pathway triggering translocation occurs upstream of Gqα. Finally, we show that ninaC mutants display a significantly reduced rate of Gqα transport from the cell body to the rhabdomere, suggesting that NINAC might function as a light-dependent plus-end motor involved in the transport of Gqα.