title: Cholesterol increases the open probability of cardiac KACh currents.
abstract: Cholesterol is one of the major lipid components of membranes in mammalian cells. In recent years, cholesterol has emerged as a major regulator of ion channel function. The most common effect of cholesterol on ion channels in general and on inwardly rectifying potassium (Kir) channels in particular is a decrease in activity. In contrast, we have recently shown that native G-protein gated Kir (GIRK or Kir3) channels that underlie atrial KACh currents are up-regulated by cholesterol. Here we unveil the biophysical basis of cholesterol-induced increase in KACh activity. Using planar lipid bilayers we show that cholesterol significantly enhances the channel open frequency of the Kir3.1/Kir3.4 channels, which underlie KACh currents. In contrast, our data indicate that cholesterol does not affect their unitary conductance. Furthermore, using fluorescent and TIRF microscopy as well as surface protein biotinylation, we also show that cholesterol enrichment in vitro has no effect on surface expression of GFP-tagged channels expressed in Xenopus oocytes or transfected into HEK293 cells. Together, these data demonstrate for the first time that cholesterol enhances Kir3-mediated current by increasing the channel open probability.
authors.affiliation: Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, United States.
authors.forename: Anna N
authors.initials: AN
authors.lastname: Bukiya
authors.affiliation: Department of Medicine, Pulmonary Section, University of Illinois at Chicago, Chicago, IL 60612, United States.
authors.forename: Catherine V
authors.initials: CV
authors.lastname: Osborn
authors.affiliation: Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, United States.
authors.forename: Guruprasad
authors.initials: G
authors.lastname: Kuntamallappanavar
authors.affiliation: Research Resources Center, University of Illinois at Chicago, Chicago, IL 60612, United States.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Toth
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, United States.
authors.forename: Lia
authors.initials: L
authors.lastname: Baki
authors.affiliation: Department of Medicine, Pulmonary Section, University of Illinois at Chicago, Chicago, IL 60612, United States.
authors.forename: Gregory
authors.initials: G
authors.lastname: Kowalsky
authors.affiliation: Department of Medicine, Pulmonary Section, University of Illinois at Chicago, Chicago, IL 60612, United States.
authors.forename: Myung J
authors.initials: MJ
authors.lastname: Oh
authors.affiliation: Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, United States.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Dopico
authors.affiliation: Department of Medicine, Pulmonary Section, University of Illinois at Chicago, Chicago, IL 60612, United States.
authors.forename: Irena
authors.initials: I
authors.lastname: Levitan
authors.affiliation: Department of Medicine, Pulmonary Section, University of Illinois at Chicago, Chicago, IL 60612, United States; Department of Pharmacology, University of Illinois at Chicago, Chicago, IL 60612, United States; Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, United States. Electronic address: dantsker@uic.edu.
authors.forename: Avia
authors.initials: A
authors.lastname: Rosenhouse-Dantsker
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000378:metabolism*; D003198:Computer Simulation; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000737:chemistry / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D008954:Models, Biological; D008956:Models, Chemical; D015233:Models, Statistical; D009865:Oocytes / Q000737:chemistry / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D002784:Cholesterol; D011188:Potassium
keywords: Cholesterol; GIRK channel; Lipids; Potassium channels