Mechanism of block of hEag1 K+ channels by imipramine and astemizole

Rafael E. Garcïa-Ferreiro, Daniel Kerschensteiner, Felix Major, Francisco Monje, Walter Stühmer, Luis A. Pardo

Research output: Contribution to journalArticle

92 Scopus citations

Abstract

Ether à go-go (Eag; KV10.1) voltage-gated K+ channels have been detected in cancer cell lines of diverse origin and shown to influence their rate of proliferation. The tricyclic antidepressant imipramine and the antihistamine astemizole inhibit the current through Eag1 channels and reduce the proliferation of cancer cells. Here we describe the mechanism by which both drugs block human Eag1 (hEag1) channels. Even if both drugs differ in their affinity for hEag1 channels (IC50s are ∼2 μM for imipramine and ∼200 nM for astemizole) and in their blocking kinetics, both drugs permeate the membrane and inhibit the hEag1 current by selectively binding to open channels. Furthermore, both drugs are weak bases and the IC 50s depend on both internal an external pH, suggesting that both substances cross the membrane in their uncharged form and act from inside the cell in their charged forms. Accordingly, the block by imipramine is voltage dependent and antagonized by intracellular TEA, consistent with imipramine binding in its charged form to a site located close to the inner end of the selectivity filter. Using inside- and outside-out patch recordings, we found that a permanently charged, quaternary derivative of imipramine (N-methyl-imipramine) only blocks channels from the intracellular side of the membrane. In contrast, the block by astemizole is voltage independent. However, as astemizole competes with imipramine and intracellular TEA for binding to the channel, it is proposed to interact with an overlapping intracellular binding site. The significance of these findings, in the context of structure-function of channels of the eag family is discussed.

Original languageEnglish
Pages (from-to)301-317
Number of pages17
JournalJournal of General Physiology
Volume124
Issue number4
DOIs
StatePublished - Oct 1 2004
Externally publishedYes

Keywords

  • Ether à go-go
  • N-methyl-imipramine
  • Open channel blockade
  • Potassium channel
  • pH dependence

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    Garcïa-Ferreiro, R. E., Kerschensteiner, D., Major, F., Monje, F., Stühmer, W., & Pardo, L. A. (2004). Mechanism of block of hEag1 K+ channels by imipramine and astemizole. Journal of General Physiology, 124(4), 301-317. https://doi.org/10.1085/jgp.200409041