title: Lateral Membrane-Specific MAGUK CASK Down-Regulates NaV1.5 Channel in Cardiac Myocytes.
abstract: BACKGROUND
  Mechanisms underlying membrane protein localization are crucial in the proper function of cardiac myocytes. The main cardiac sodium channel, NaV1.5, carries the sodium current (INa) that provides a rapid depolarizing current during the upstroke of the action potential. Although enriched in the intercalated disc, NaV1.5 is present in different membrane domains in myocytes and interacts with several partners.
  
  
  OBJECTIVE
  To test the hypothesis that the MAGUK (membrane-associated guanylate kinase) protein CASK (calcium/calmodulin-dependent serine protein kinase) interacts with and regulates NaV1.5 in cardiac myocytes.
  
  
  RESULTS
  Immunostaining experiments showed that CASK localizes at lateral membranes of cardiac myocytes, in association with dystrophin. Whole-cell patch clamp showed that CASK-silencing increases INa in vitro. In vivo CASK knockdown similarly increased INa recorded in freshly isolated myocytes. Pull-down experiments revealed that CASK directly interacts with the C-terminus of NaV1.5. CASK silencing reduces syntrophin expression without affecting NaV1.5 and dystrophin expression levels. Total Internal Reflection Fluorescence microscopy and biotinylation assays showed that CASK silencing increased the surface expression of NaV1.5 without changing mRNA levels. Quantification of NaV1.5 expression at the lateral membrane and intercalated disc revealed that the lateral membrane pool only was increased upon CASK silencing. The protein transport inhibitor brefeldin-A prevented INa increase in CASK-silenced myocytes. During atrial dilation/remodeling, CASK expression was reduced but its localization remained unchanged.
  
  
  CONCLUSIONS
  This study constitutes the first description of an unconventional MAGUK protein, CASK, which directly interacts with NaV1.5 channel and controls its surface expression at the lateral membrane by regulating ion channel trafficking.
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Eichel
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Adeline
authors.initials: A
authors.lastname: Beuriot
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Morgan Y E
authors.initials: MY
authors.lastname: Chevalier
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Rougier
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Florent
authors.initials: F
authors.lastname: Louault
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Gilles
authors.initials: G
authors.lastname: Dilanian
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Julien
authors.initials: J
authors.lastname: Amour
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Alain
authors.initials: A
authors.lastname: Coulombe
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Hugues
authors.initials: H
authors.lastname: Abriel
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
authors.forename: Stéphane N
authors.initials: SN
authors.lastname: Hatem
authors.affiliation: From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.). elise.balse@upmc.fr.
authors.forename: Elise
authors.initials: E
authors.lastname: Balse
mesh_terms: D000818:Animals; D015536:Down-Regulation / Q000502:physiology*; D051528:Guanylate Kinases / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000378:metabolism*; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D051381:Rats
chemical_list: D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; C106868:CASK kinases; D051528:Guanylate Kinases
keywords: calcium/calmodulin-dependent serine protein kinase; cardiac myocytes; dystrophin; ion channels; membrane-associated guanylate kinase; sodium channels; syntrophin