Polyunsaturated fatty acids activate the Drosophila light-sensitive channels TRP and TRPL

Phototransduction in invertebrate microvillar photoreceptors is thought to be mediated by the activation of phospholipase C (PLC), but how this leads to gating of the light-sensitive channels is unknown(1,2). Most attention h as focused on inositol-1,4,5-trisphosphate, a second messenger produced by PLC from phosphatidylinositol-4,5-bisphosphate; however, PLC also generates diacylglycerol, a potential precursor for several polyunsaturated fatty ac ids, such as arachidonic acid and linolenic acid. Here we show that both of these fatty acids reversibly activate native light-sensitive channels (tra nsient receptor potential (TRP) and TRP-like (TRPL)) in Drosophila photorec eptors as well as recombinant TRPL channels expressed in Drosophila S2 cell s. Recombinant channels are activated rapidly in both whole-cell recordings and inside-out patches, with a half-maximal effector concentration for lin olenic acid of similar to 10 mu M Four different Lipoxygenase inhibitors, w hich might be expected to lead to build-up of endogenous fatty [GRAPHICS] acids, also activate native TRP and TRPL channels in intact photoreceptors, As arachidonic acid may not be found in Drosophila, we suggest that anothe r polyunsaturated fatty acid, such as linolenic acid, may be a messenger of excitation in Drosophila photoreceptors.