title: [Ca2+]i elevation and oxidative stress induce KCNQ1 protein translocation from the cytosol to the cell surface and increase slow delayed rectifier (IKs) in cardiac myocytes.
abstract: Our goals are to simultaneously determine the three-dimensional distribution patterns of KCNQ1 and KCNE1 in cardiac myocytes and to study the mechanism and functional implications for variations in KCNQ1/KCNE1 colocalization in myocytes. We monitored the distribution patterns of KCNQ1, KCNE1, and markers for subcellular compartments/organelles using immunofluorescence/confocal microscopy and confirmed the findings in ventricular myocytes by directly observing fluorescently tagged KCNQ1-GFP and KCNE1-dsRed expressed in these cells. We also monitored the effects of stress on KCNQ1-GFP and endoplasmic reticulum (ER) remodeling during live cell imaging. The data showed that 1) KCNE1 maintained a stable cell surface localization, whereas KCNQ1 exhibited variations in the cytosolic compartment (striations versus vesicles) and the degree of presence on the cell surface; 2) the degree of cell surface KCNQ1/KCNE1 colocalization was positively correlated with slow delayed rectifier (IKs) current density; 3) KCNQ1 and calnexin (an ER marker) shared a cytosolic compartment; and 4) in response to stress ([Ca(2+)]i elevation, oxidative overload, or AT1R stimulation), KCNQ1 exited the cytosolic compartment and trafficked to the cell periphery in vesicles. This was accompanied by partial ER fragmentation. We conclude that the cellular milieu regulates KCNQ1 distribution in cardiac myocytes and that stressful conditions can increase IKs by inducing KCNQ1 movement to the cell surface. This represents a hitherto unrecognized mechanism by which IKs fulfills its function as a repolarization reserve in ventricular myocytes.
authors.affiliation: From the Department of Physiology and Biophysics and.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Wang
authors.forename: Dimitar P
authors.initials: DP
authors.lastname: Zankov
authors.forename: Min
authors.initials: M
authors.lastname: Jiang
authors.forename: Mei
authors.initials: M
authors.lastname: Zhang
authors.forename: Scott C
authors.initials: SC
authors.lastname: Henderson
authors.forename: Gea-Ny
authors.initials: GN
authors.lastname: Tseng
mesh_terms: D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D037281:Calnexin / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D003600:Cytosol / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006168:Guinea Pigs; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018384:Oxidative Stress; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C489622:KCNE1 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D044140:Receptor, Angiotensin, Type 1; D011993:Recombinant Fusion Proteins; D037281:Calnexin; D002118:Calcium
keywords: Confocal Microscopy; Endoplasmic Reticulum (ER); Potassium Channels; Stress Response; Trafficking