Optopharmacological control of TRPC channels by coumarin-caged lipids is associated with a phototoxic membrane effect  

作　　者：Oleksandra Tiapko Bernadett Bacsa Gema Guedes de la Cruz Toma Glasnov Klaus Groschner 

机构地区：[1]Institute of Biophysics,Medical University of Graz,Bio Tech Med-Graz,Harrachgasse 21,Graz 8010,Austria [2]Institute of Chemistry,University of Graz,NAWI Graz,Bio Tech Med-Graz,Heinrichstrasse 28,Graz 8010,Austria

出　　处：《Science China(Life Sciences)》2016年第8期802-810,共9页中国科学（生命科学英文版）

基　　金：supported by the Austrian Science Fund(FWFW 1226-B18)

摘　　要：Photouncaging of second messengers has been successfully employed to gain mechanistic insight of cellular signaling path- ways. One of the most enigmatic processes of ion channel regulation is lipid recognition and lipid-gating of TRPC channels, which represents pivotal mechanisms of cellular Ca2＋ homeostasis. Recently, optopharmacological tools including caged lipid mediators became available, enabling an unprecedented level of temporal and spatial control of the activating lipid species within a cellular environment. Here we tested a commonly used caged ligand approach for suitability to investigate TRPC sig- naling at the level of membrane conductance and cellular Ca2＋ handling. We report a specific photouncaging artifact that is triggered by the cage structure coumarin at UV illumination. Electrophysiological characterization identified a light-dependent membrane effect of coumarin. UV light （340 nm） as used for photouncaging, initiated a membrane conductance specifically in the presence of coumarin as low as 30 pmol L-1 concentrations. This conductance masked the TRPC3 conductance evoked by photouncaging, while TRPC-mediated cellular Ca2＋ responses were largely preserved. The observed light-induced membrane effects of the released caging moiety may well interfere with certain cellular functions, and prompt caution in using couma- fin-caged second messengers in cellular studies.Photouncaging of second messengers has been successfully employed to gain mechanistic insight of cellular signaling pathways. One of the most enigmatic processes of ion channel regulation is lipid recognition and lipid-gating of TRPC channels, which represents pivotal mechanisms of cellular Ca^(2+) homeostasis. Recently, optopharmacological tools including caged lipid mediators became available, enabling an unprecedented level of temporal and spatial control of the activating lipid species within a cellular environment. Here we tested a commonly used caged ligand approach for suitability to investigate TRPC signaling at the level of membrane conductance and cellular Ca^(2+) handling. We report a specific photouncaging artifact that is triggered by the cage structure coumarin at UV illumination. Electrophysiological characterization identified a light-dependent membrane effect of coumarin. UV light(340 nm) as used for photouncaging, initiated a membrane conductance specifically in the presence of coumarin as low as 30 μmol L^(-1) concentrations. This conductance masked the TRPC3 conductance evoked by photouncaging, while TRPC-mediated cellular Ca^(2+) responses were largely preserved. The observed light-induced membrane effects of the released caging moiety may well interfere with certain cellular functions, and prompt caution in using coumarin-caged second messengers in cellular studies.

关 键 词：caged diacylglycerols TRPC channels Ca2+ signaling optopharmacology 

分 类 号：Q25[生物学—细胞生物学]