The heart rate decrease caused by acute FTY720 administration is mediated by the G protein-gated potassium channel I.
Sphingosine-1-phosphate (S1P) is an endogenous agonist for a family of five G protein-coupled receptors (S1P(1-5)) involved in cell proliferation, cardiovascular development and lymphocyte trafficking. The sphingolipid drug FTY720 displays structural similarity to S1P and efficacy as an immunosuppressant in models of autoimmune disease and in solid organ transplantation. While FTY720 is well-tolerated in humans, it produces a transient reduction of heart rate (HR). As S1P activates the cardiac G protein-gated potassium channel I(KACh), we speculated that the FTY720-induced HR reduction reflects I(KACh) activation. We examined FTY720 effects on atrial myocytes from wild-type and I(KACh)-deficient mice. In wild-type myocytes, the active phosphate metabolite of FTY720 (FTY720-P) induced single channel activity with conductance, open time, GTP sensitivity and rectification identical to that of I(KACh). In whole-cell recordings, FTY720-P evoked an inwardly rectifying potassium current in approximately 90% of myocytes responding to acetylcholine. Comparable channel activity was never observed in myocytes from I(KACh)-deficient mice. In wild-type mice, acute FTY720 administration produced a dose-dependent, robust HR reduction. In contrast, the HR reduction induced by FTY720 in I(KACh)-deficient mice was blunted. We conclude that the effect of acute FTY720 administration on HR is mediated primarily by I(KACh) activation.
Koyrakh
Lev
L
Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA.
Roman
Maria I
MI
Brinkmann
Volker
V
Wickman
Kevin
K
D000818:Animals; D003864:Depression, Chemical; D000068876:Fingolimod Hydrochloride; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011409:Propylene Glycols / Q000494:pharmacology*; D013110:Sphingosine / Q000031:analogs & derivatives
D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D007166:Immunosuppressive Agents; C497067:Kcnj3 protein, mouse; D024661:Potassium Channels, Inwardly Rectifying; D011409:Propylene Glycols; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine