title: Cholesterol modulates the recruitment of Kv1.5 channels from Rab11-associated recycling endosome in native atrial myocytes.
abstract: Cholesterol is an important determinant of cardiac electrical properties. However, underlying mechanisms are still poorly understood. Here, we examine the hypothesis that cholesterol modulates the turnover of voltage-gated potassium channels based on previous observations showing that depletion of membrane cholesterol increases the atrial repolarizing current I(Kur). Whole-cell currents and single-channel activity were recorded in rat adult atrial myocytes (AAM) or after transduction with hKv1.5-EGFP. Channel mobility and expression were studied using fluorescence recovery after photobleaching (FRAP) and 3-dimensional microscopy. In both native and transduced-AAMs, the cholesterol-depleting agent MbetaCD induced a delayed ( approximately 7 min) increase in I(Kur); the cholesterol donor LDL had an opposite effect. Single-channel recordings revealed an increased number of active Kv1.5 channels upon MbetaCD application. Whole-cell recordings indicated that this increase was not dependent on new synthesis but on trafficking of existing pools of intracellular channels whose exocytosis could be blocked by both N-ethylmaleimide and nonhydrolyzable GTP analogues. Rab11 was found to coimmunoprecipitate with hKv1.5-EGFP channels and transfection with Rab11 dominant negative (DN) but not Rab4 DN prevented the MbetaCD-induced I(Kur) increase. Three-dimensional microscopy showed a decrease in colocalization of Kv1.5 and Rab11 in MbetaCD-treated AAM. These results suggest that cholesterol regulates Kv1.5 channel expression by modulating its trafficking through the Rab11-associated recycling endosome. Therefore, this compartment provides a submembrane pool of channels readily available for recruitment into the sarcolemma of myocytes. This process could be a major mechanism for the tuning of cardiac electrical properties and might contribute to the understanding of cardiac effects of lipid-lowering drugs.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche Scientifique-956, 75013 Paris, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Balse
authors.forename: Saïd
authors.initials: S
authors.lastname: El-Haou
authors.forename: Gilles
authors.initials: G
authors.lastname: Dillanian
authors.forename: Aurélien
authors.initials: A
authors.lastname: Dauphin
authors.forename: Jodene
authors.initials: J
authors.lastname: Eldstrom
authors.forename: David
authors.initials: D
authors.lastname: Fedida
authors.forename: Alain
authors.initials: A
authors.lastname: Coulombe
authors.forename: Stéphane N
authors.initials: SN
authors.lastname: Hatem
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006325:Heart Atria / Q000166:cytology; D006801:Humans; D051666:Kv1.5 Potassium Channel / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D014162:Transfection; D047392:beta-Cyclodextrins / Q000494:pharmacology; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D002784:Cholesterol; D049452:Green Fluorescent Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D051666:Kv1.5 Potassium Channel; D047392:beta-Cyclodextrins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C108732:methyl-beta-cyclodextrin
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