Chyb S, Raghu P, Hardie R C
Cambridge University Department of Anatomy, UK.
Nature. 1999 Jan 21;397(6716):255-9. doi: 10.1038/16703.
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. Most attention has 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 acids, such as arachidonic acid and linolenic acid. Here we show that both of these fatty acids reversibly activate native light-sensitive channels (transient receptor potential (TRP) and TRP-like (TRPL)) in Drosophila photoreceptors as well as recombinant TRPL channels expressed in Drosophila S2 cells. Recombinant channels are activated rapidly in both whole-cell recordings and inside-out patches, with a half-maximal effector concentration for linolenic acid of approximately 10 microM. Four different lipoxygenase inhibitors, which might be expected to lead to build-up of endogenous fatty acids, also activate native TRP and TRPL channels in intact photoreceptors. As arachidonic acid may not be found in Drosophila, we suggest that another polyunsaturated fatty acid, such as linolenic acid, may be a messenger of excitation in Drosophila photoreceptors.
无脊椎动物微绒毛光感受器中的光转导被认为是由磷脂酶C（PLC）的激活介导的，但这如何导致光敏感通道的门控尚不清楚。大多数注意力都集中在肌醇-1,4,5-三磷酸上，它是PLC从磷脂酰肌醇-4,5-二磷酸产生的第二信使；然而，PLC还会生成二酰基甘油，它是几种多不饱和脂肪酸（如花生四烯酸和亚麻酸）的潜在前体。在这里，我们表明这两种脂肪酸都能可逆地激活果蝇光感受器中的天然光敏感通道（瞬时受体电位（TRP）和TRP样（TRPL）通道）以及在果蝇S2细胞中表达的重组TRPL通道。在全细胞记录和内向外膜片中，重组通道都能被迅速激活，亚麻酸的半数最大效应浓度约为10微摩尔。四种不同的脂氧合酶抑制剂，可能会导致内源性脂肪酸的积累，也能激活完整光感受器中的天然TRP和TRPL通道。由于在果蝇中可能找不到花生四烯酸，我们认为另一种多不饱和脂肪酸，如亚麻酸，可能是果蝇光感受器中的兴奋信使。
