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Block of TRPC5 channels by 2‐aminoethoxydiphenyl borate: a differential, extracellular and voltage‐dependent effect
Author(s) -
Xu ShangZhong,
Zeng Fanning,
Boulay Guylain,
Grimm Christian,
Harteneck Christian,
Beech David J
Publication year - 2005
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0706197
Subject(s) - extracellular , trpc5 , block (permutation group theory) , differential (mechanical device) , chemistry , neuroscience , biophysics , microbiology and biotechnology , biology , biochemistry , transient receptor potential channel , physics , mathematics , trpc , receptor , geometry , thermodynamics
1 2‐Aminoethoxydiphenyl borate (2‐APB) has been widely used to examine the roles of inositol 1,4,5‐trisphosphate receptors (IP 3 Rs) and store‐operated Ca 2+ entry and is an emerging modulator of cationic channels encoded by transient receptor potential (TRP) genes. 2 Using Ca 2+ ‐indicator dye and patch‐clamp recording we first examined the blocking effect of 2‐APB on human TRPC5 channels expressed in HEK‐293 cells. 3 The concentration–response curve has an IC 50 of 20 μ M and slope close to 1.0, suggesting one 2‐APB molecule binds per channel. The blocking effect is not shared by other Ca 2+ channel blockers including methoxyverapamil, nifedipine, N ‐propargylnitrendipine, or berberine. 4 In whole‐cell and excised membrane patch recordings, 2‐APB acts from the extracellular but not intracellular face of the membrane. 5 Block of TRPC5 by 2‐APB is less at positive voltages, suggesting that it enters the electric field or acts by modulating channel gating. 6 2‐APB also blocks TRPC6 and TRPM3 expressed in HEK‐293 cells, but not TRPM2. 7 Block of TRP channels by 2‐APB may be relevant to cell proliferation because 2‐APB has a greater inhibitory effect on proliferation in cells overexpressing TRPC5. 8 Our data indicate a specific and functionally important binding site on TRPC5 that enables block by 2‐APB. The site is only available via an extracellular route and the block shows mild voltage‐dependence.British Journal of Pharmacology (2005) 145 , 405–414. doi: 10.1038/sj.bjp.0706197