The latency of the light response is modulated by the phosphorylation state of Drosophila TRP at a specific site

摘要

Drosophila photoreceptors respond to oscillating light of high frequency (similar to 100 Hz), while increasing the oscillating light intensity raises the maximally detected frequency. Recently, we reported that dephosphorylation of the light-activated TRP ion channel at S936 is a fast, graded, light-, and Ca2+-dependent process. We further found that this process affects the detection limit of high frequency oscillating light. Accordingly, transgenic Drosophila, which do not undergo phosphorylation at the S936-TRP site (trp(S936A)), revealed a short time-interval before following the high stimulus frequency (oscillation-lock response) in both dark-and light-adapted flies. In contrast, the trp(S936D) transgenic flies, which mimic constant phosphorylation, showed a long-time interval to oscillation-lock response in both dark-and light-adapted flies. Here we extend these findings by showing that dark-adapted trp(S936A) flies reveal light-induced current (LIC) with short latency relative to trp(WT) or trp(S936D) flies, indicating that the channels are a limiting factor of response kinetics. The results indicate that properties of the light-activated channels together with the dynamic light-dependent process of TRP phosphorylation at the S936 site determine response kinetics.