RT Journal Article SR Electronic T1 A Common Mechanism Underlies Vertebrate Calcium Signaling andDrosophila Phototransduction JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 2622 OP 2629 DO 10.1523/JNEUROSCI.21-08-02622.2001 VO 21 IS 8 A1 Irit Chorna-Ornan A1 Tamar Joel-Almagor A1 Hagit Cohen Ben-Ami A1 Shahar Frechter A1 Boaz Gillo A1 Zvi Selinger A1 Donald L. Gill A1 Baruch Minke YR 2001 UL http://www.jneurosci.org/content/21/8/2622.abstract AB Drosophila phototransduction is an important model system for studies of inositol lipid signaling. Light excitation inDrosophila photoreceptors depends on phospholipase C, because null mutants of this enzyme do not respond to light. Surprisingly, genetic elimination of the apparently single inositol trisphosphate receptor (InsP3R) ofDrosophila has no effect on phototransduction. This led to the proposal that Drosophila photoreceptors do not use the InsP3 branch of phospholipase C (PLC)-mediated signaling for phototransduction, unlike most other inositol lipid-signaling systems. To examine this hypothesis we applied the membrane-permeant InsP3R antagonist 2-aminoethoxydiphenyl borate (2-APB), which has proved to be an important probe for assessing InsP3R involvement in various signaling systems. We first examined the effects of 2-APB onXenopus oocytes. We found that 2-APB is efficient at reversibly blocking the robust InsP3-mediated Ca2+ release and store-operated Ca2+ entry in Xenopus oocytes at a stage operating after production of InsP3 but before the opening of the surface membrane Cl− channels by Ca2+. We next demonstrated that 2-APB is effective at reversibly blocking the response to light ofDrosophila photoreceptors in a light-dependent manner at a concentration range similar to that effective inXenopus oocytes and other cells. We show furthermore that 2-APB does not directly block the light-sensitive channels, indicating that it operates upstream in the activation of these channels. The results indicate an important link in the coupling mechanism of vertebrate store-operated channels andDrosophila TRP channels, which involves the InsP3 branch of the inositol lipid-signaling pathway.