TY - JOUR T1 - A Ca<sup>2+</sup>/Calmodulin-Dependent Protein Kinase Modulates<em>Drosophila</em> Photoreceptor K<sup>+</sup> Currents: A Role in Shaping the Photoreceptor Potential JF - The Journal of Neuroscience JO - J. Neurosci. SP - 9153 LP - 9162 DO - 10.1523/JNEUROSCI.18-22-09153.1998 VL - 18 IS - 22 AU - Asher Peretz AU - Ilane Abitbol AU - Alexander Sobko AU - Chun-Fang Wu AU - Bernard Attali Y1 - 1998/11/15 UR - http://www.jneurosci.org/content/18/22/9153.abstract N2 - Light activation of Drosophila photoreceptors leads to the generation of a depolarizing receptor potential via opening of transient receptor potential and transient receptor potential-like cationic channels. Counteracting the light-activated depolarizing current are two voltage-gated K+ conductances, IA andIK, that are expressed in these sensory neurons. Here we show that Drosophilaphotoreceptors IA andIK are regulated by calcium–calmodulin (Ca2+/calmodulin) via a Ca2+/calmodulin-dependent protein kinase (CaM kinase), with IK being far more sensitive than IA. Inhibition of Ca2+/calmodulin by N-(6 aminohexyl)-5-chloro-1-naphthalenesulfonamide or trifluoperazine markedly reduced the K+ current amplitudes. Likewise, inhibition of CaM kinases by KN-93 potently depressedIK and accelerated its C-type inactivation kinetics. The effect of KN-93 was specific because its structurally related but functionally inactive analog KN-92 was totally ineffective. In Drosophila photoreceptor mutantShKS133 , which allows isolation ofIK, we demonstrate by current-clamp recording that inhibition of IK by quinidine or tetraethylammonium increased the amplitude of the photoreceptor potential, depressed light adaptation, and slowed down the termination of the light response. Similar results were obtained when CaM kinases were blocked by KN-93. These findings place photoreceptor K+ channels as an additional target for Ca2+/calmodulin and suggest thatIK is well suited to act in concert with other components of the signaling machinery to sharpen light response termination and fine tune photoreceptor sensitivity during light adaptation. ER -