title: Kv7.1 surface expression is regulated by epithelial cell polarization.
abstract: The potassium channel K(V)7.1 is expressed in the heart where it contributes to the repolarization of the cardiac action potential. In addition, K(V)7.1 is expressed in epithelial tissues where it plays a role in salt and water transport. Mutations in the kcnq1 gene can lead to long QT syndrome and deafness, and several mutations have been described as trafficking mutations. To learn more about the basic mechanisms that regulate K(V)7.1 surface expression, we have investigated the trafficking of K(V)7.1 during the polarization process of the epithelial cell line Madin-Darby Canine Kidney (MDCK) using a modified version of the classical calcium switch. We discovered that K(V)7.1 exhibits a very dynamic localization pattern during the calcium switch. When MDCK cells are kept in low calcium medium, K(V)7.1 is mainly observed at the plasma membrane. During the first hours of the switch, K(V)7.1 is removed from the plasma membrane and an intracellular accumulation in the endoplasmic reticulum (ER) is observed. The channel is retained in the ER until the establishment of the lateral membranes at which point K(V)7.1 is released from the ER and moves to the plasma membrane. Our data furthermore suggest that while the removal of K(V)7.1 from the cell surface and its accumulation in the ER could involve activation of protein kinase C, the subsequent release of K(V)7.1 from the ER depends on phosphoinositide 3-kinase (PI3K) activation. In conclusion, our results demonstrate that K(V)7.1 surface expression is regulated by signaling mechanisms involved in epithelial cell polarization in particular signaling cascades involving protein kinase C and PI3K.
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Denmark.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Andersen
authors.forename: Søren-Peter
authors.initials: SP
authors.lastname: Olesen
authors.forename: Hanne B
authors.initials: HB
authors.lastname: Rasmussen
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D003896:Desmosomes / Q000378:metabolism; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction / Q000502:physiology; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D051657:KCNQ1 Potassium Channel; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D002118:Calcium