PT - JOURNAL ARTICLE AU - Olaf Voolstra AU - Elisheva Rhodes-Mordov AU - Ben Katz AU - Jonas-Peter Bartels AU - Claudia Oberegelsbacher AU - Susanne Katharina Schotthöfer AU - Bushra Yasin AU - Hanan Tzadok AU - Armin Huber AU - Baruch Minke TI - The Phosphorylation State of the <em>Drosophila</em> TRP Channel Modulates the Frequency Response to Oscillating Light <em>in Vivo</em> AID - 10.1523/JNEUROSCI.3670-16.2017 DP - 2017 Mar 17 TA - The Journal of Neuroscience PG - 3670-16 4099 - http://www.jneurosci.org/content/early/2017/03/15/JNEUROSCI.3670-16.2017.short 4100 - http://www.jneurosci.org/content/early/2017/03/15/JNEUROSCI.3670-16.2017.full AB - Drosophila photoreceptors respond to oscillating light of high frequency (∼100 Hz), while the detected maximal frequency is modulated by the light rearing conditions, thus maintaining high sensitivity to light and high temporal resolution. However, the molecular basis for this adaptive process is unclear. Here, we report that dephosphorylation of the light-activated Transient Receptor Potential (TRP) ion channel at S936 is a fast, graded, light-, and Ca2+-dependent process that is partially modulated by the rhodopsin phosphatase Retinal Degeneration C (RDGC). Electroretinogram (ERG) measurements of the frequency response to oscillating lights in vivo revealed that dark-reared flies expressing wild type TRP exhibited a detection limit of oscillating light at relatively low frequencies, which was shifted to higher frequencies upon light adaptation. Strikingly, preventing phosphorylation of the S936-TRP site by alanine substitution in transgenic Drosophila (trpS936A) abolished the difference in frequency response between dark- and light-adapted flies, resulting in high frequency response also in dark adapted flies. In contrast, inserting a phosphomimetic mutation by substituting the S936-TRP site to aspartic acid (trpS936D) set the frequency response of light-adapted flies to low frequencies typical of dark-adapted flies. Light-adapted rdgC mutant flies showed relatively high S936-TRP phosphorylation levels and light-dark phosphorylation dynamics. These findings suggest that RDGC is one but not the only phosphatase involved in pS936-TRP dephosphorylation. Together, this study indicates that TRP channel dephosphorylation is a regulatory process that affects the detection limit of oscillating light according to the light rearing condition, thus adjusting dynamic processing of visual information under varying light conditions.SIGNIFICANCE STATEMENTDrosophila photoreceptors exhibit high temporal resolution as manifested in frequency response to oscillating light of high frequency (up to ∼100 Hz). The detected maximal frequency is modulated by the light rearing conditions, thus maintaining high sensitivity to light and high temporal resolution via unclear mechanisms. Here, we show by combination of biochemistry and in vivo electrophysiology that TRP channel dephosphorylation at a specific site is a fast, light-activated and Ca2+-dependent regulatory process. TRP dephosphorylation affects the detection limit of oscillating light according to the adaptation state of the photoreceptor cells by shifting the detection limit to higher frequencies upon light adaptation. This novel mechanism thus adjusts dynamic processing of visual information under varying light conditions.