title: Nav1.5 N-terminal domain binding to α1-syntrophin increases membrane density of human Kir2.1, Kir2.2 and Nav1.5 channels.
abstract: OBJECTIVE
  Cardiac excitability and refractoriness are largely determined by the function and number of inward rectifier K⁺ channels (Kir2.1-2.3), which are differentially expressed in the atria and ventricles, and Nav1.5 channels. We have focused on how Nav1.5 and Kir2.x function within a macromolecular complex by elucidating the molecular determinants that govern Nav1.5/Kir2.x reciprocal modulation.
  
  
  RESULTS
  The results demonstrate that there is an unexpected 'internal' PDZ-like binding domain located at the N-terminus of the Nav1.5 channel that mediates its binding to α1-syntrophin. Nav1.5 N-terminal domain, by itself (the 132 aa peptide) (Nter), exerts a 'chaperone-like' effect that increases sodium (I(Na)) and inward rectifier potassium (I(K1)) currents by enhancing the expression of Nav1.5, Kir2.1, and Kir2.2 channels as demonstrated in Chinese hamster ovary (CHO) cells and in rat cardiomyocytes. Site-directed mutagenesis analysis demonstrates that the Nter chaperone-like effect is determined by Serine 20. Nav1.5-Kir2.x reciprocal positive interactions depend on a specific C-terminal PDZ-binding domain sequence (SEI), which is present in Kir2.1 and Kir2.2 channels but not in Kir2.3. Therefore, in human atrial myocytes, the presence of Kir2.3 isoforms precludes reciprocal I(K1)-INa density modulation. Moreover, results in rat and human atrial myocytes demonstrate that binding to α1-syntrophin is necessary for the Nav1.5-Kir2.x-positive reciprocal modulation.
  
  
  CONCLUSIONS
  The results demonstrate the critical role of the N-terminal domain of Nav1.5 channels in Nav1.5-Kir2.x-reciprocal interactions and suggest that the molecular mechanisms controlling atrial and ventricular cellular excitability may be different.
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Marcos
authors.initials: M
authors.lastname: Matamoros
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Pérez-Hernández
authors.affiliation: Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109, USA Department of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Guerrero-Serna
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Amorós
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Adriana
authors.initials: A
authors.lastname: Barana
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Núñez
authors.affiliation: Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109, USA Department of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Daniela
authors.initials: D
authors.lastname: Ponce-Balbuena
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: Sacristán
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Gómez
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Tamargo
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain rcaballero@med.ucm.es.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Caballero
authors.affiliation: Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109, USA Department of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: José
authors.initials: J
authors.lastname: Jalife
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Delpón
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D006224:Cricetinae; D006352:Heart Ventricles / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D032383:Myocytes, Cardiac / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D051381:Rats
chemical_list: D002135:Calcium-Binding Proteins; C489457:KCNJ2 protein, human; C575188:KCNJ2 protein, rat; C489463:Kir2.2 channel; D008565:Membrane Proteins; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D024661:Potassium Channels, Inwardly Rectifying; C568320:SCN5A protein, human; C568322:Scn5a protein, rat; C091825:syntrophin alpha1
keywords: Inward rectifier current; Kir2.x; Sodium current; α1-syntrophin