title: Diacylglycerol activates the light-dependent channel TRP in the photosensitive microvilli of Drosophila melanogaster photoreceptors.
abstract: Drosophila light-dependent channels, TRP and TRPL, reside in the light-sensitive microvilli of the photoreceptor's rhabdomere. Phospholipase C mediates TRP/TRPL opening, but the gating process remains unknown. Controversial evidence has suggested diacylglycerol (DAG), polyunsaturated fatty acids (PUFAs, a DAG metabolite), phosphatidylinositol bisphosphate (PIP2), and H(+) as possible channel activators. We tested each of them directly in inside-out TRP-expressing patches excised from the rhabdomere, making use of mutants and pharmacology. When patches were excised in darkness TRP remained closed, while when excised under illumination it stayed constitutively active. TRP was opened by DAG and silenced by ATP, suggesting DAG-kinase (DGK) involvement. The ATP effect was abolished by inhibiting DGK and in the rdgA mutant, lacking functional DGK, implicating DGK. DAG activated TRP even in the presence of a DAG-lipase inhibitor, inconsistent with a requirement of PUFAs in opening TRP. PIP2 had no effect and acidification, pH 6.4, activated TRP irreversibly, unlike the endogenous activator. Complementary liquid-chromatography/mass-spectrometry determinations of DAG and PUFAs in membranes enriched in rhabdomere obtained from light- and dark-adapted eyes showed light-dependent increment in six DAG species and no changes in PUFAs. The results strongly support DAG as the endogenous TRP agonist, as some of its vertebrate TRPC homologs of the same channel family.
authors.affiliation: Department of Biology, Faculty of Sciences, University of Chile, 7800024 Santiago, Chile, Biotechnology Center D. Alkalay L., Technical University Federico Santa María, 2340000 Valparaíso, Chile, and Max Planck Institute of Molecular Plant Physiology, 14776 Potsdam, Germany.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Delgado
authors.forename: Yorka
authors.initials: Y
authors.lastname: Muñoz
authors.forename: Hugo
authors.initials: H
authors.lastname: Peña-Cortés
authors.forename: Patrick
authors.initials: P
authors.lastname: Giavalisco
authors.forename: Juan
authors.initials: J
authors.lastname: Bacigalupo
mesh_terms: D000221:Adaptation, Ocular; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D003624:Darkness; D019852:Diacylglycerol Kinase / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology*; D029721:Drosophila Proteins / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008027:Light; D050356:Lipid Metabolism / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000187:drug effects*; D008566:Membranes / Q000502:physiology; D008871:Microvilli / Q000187:drug effects*; D017956:Photoreceptor Cells, Invertebrate / Q000187:drug effects*; D011522:Protons
chemical_list: D004075:Diglycerides; D029721:Drosophila Proteins; D005231:Fatty Acids, Unsaturated; D008565:Membrane Proteins; D011522:Protons; C090530:Trp1 protein, Drosophila; D000255:Adenosine Triphosphate; D019852:Diacylglycerol Kinase
keywords: Drosophila; TRP; diacylglycerol; microvilli; photoreceptors; phototransduction