科研之友
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摘要
The chemical structures of the thyroid hormones triiodothyronine (T-3) and thyroxine (T-4) resemble those of small-molecules that inhibit the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel. We therefore tested the acute effects of T-3, T-4 and reverse T-3 (rT(3)) on recombinant wild-type human CFTR using the patch-clamp technique. When added directly to the intracellular solution bathing excised membrane patches, T-3, T-4, and rT(3) (all tested at 50 mu M) inhibited CFTR in several ways: they strongly reduced CFTR open probability by impeding channel opening; they moderately decreased single-channel current amplitude, and they promoted transitions to subconductance states. To investigate the mechanism of CFTR inhibition, we studied T-3. T-3 (50 mu M) had multiple effects on CFTR gating kinetics, suggestive of both allosteric inhibition and open-channel blockade. Channel inhibition by T-3 was weakly voltage dependent and stronger than the allosteric inhibitor genistein, but weaker than the open-channel blocker glibenclamide. Raising the intracellular ATP concentration abrogated T-3 inhibition of CFTR gating, but not the reduction in single-channel current amplitude nor the transitions to subconductance states. The decrease in single-channel current amplitude was relieved by membrane depolarization, but not the transitions to subconductance states. We conclude that T-3 has complex effects on CFTR consistent with both allosteric inhibition and open-channel blockade. Our results suggest that there are multiple allosteric mechanisms of CFTR inhibition, including interference with ATP-dependent channel gating and obstruction of conformational changes that gate the CFTR pore. CFTR inhibition by thyroid hormones has implications for the development of innovative small-molecule CFTR inhibitors.
- 出版日期2013-10
