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Structural requirements of steroidal agonists of transient receptor potential melastatin 3 ( TRPM 3) cation channels
Author(s) -
Drews A,
Mohr F,
Rizun O,
Wagner T F J,
Dembla S,
Rudolph S,
Lambert S,
Konrad M,
Philipp S E,
Behrendt M,
MarchaisOberwinkler S,
Covey D F,
Oberwinkler J
Publication year - 2014
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 - 10.1111/bph.12521
Subject(s) - pregnenolone , pregnenolone sulfate , transient receptor potential channel , chemistry , biophysics , receptor , biochemistry , steroid , biology , hormone
Background and Purpose Transient receptor potential melastatin 3 ( TRPM 3) proteins form non‐selective but calcium‐permeable membrane channels, rapidly activated by extracellular application of the steroid pregnenolone sulphate and the dihydropyridine nifedipine. Our aim was to characterize the steroid binding site by analysing the structural chemical requirements for TRPM 3 activation. Experimental Approach Whole‐cell patch‐clamp recordings and measurements of intracellular calcium concentrations were performed on HEK 293 cells transfected with TRPM 3 (or untransfected controls) during superfusion with pharmacological substances. Key Results Pregnenolone sulphate and nifedipine activated TRPM 3 channels supra‐additively over a wide concentration range. Other dihydropyridines inhibited TRPM 3 channels. The natural enantiomer of pregnenolone sulphate was more efficient in activating TRPM 3 channels than its synthetic mirror image. However, both enantiomers exerted very similar inhibitory effects on proton‐activated outwardly rectifying anion channels. Epiallopregnanolone sulphate activated TRPM 3 almost equally as well as pregnenolone sulphate. Exchanging the sulphate for other chemical moieties showed that a negative charge at this position is required for activating TRPM 3 channels. Conclusions and Implications Our data demonstrate that nifedipine and pregnenolone sulphate act at different binding sites when activating TRPM 3. The latter activates TRPM 3 by binding to a chiral and thus proteinaceous binding site, as inferred from the differential effects of the enantiomers. The double bond between position C 5 and C 6 of pregnenolone sulphate is not strictly necessary for the activation of TRPM 3 channels, but a negative charge at position C 3 of the steroid is highly important. These results provide a solid basis for understanding mechanistically the rapid chemical activation of TRPM 3 channels.