Nav1.5 N-terminal domain binding to alpha 1-syntrophin increases membrane density of human Kir2.1, Kir2.2 and Nav1.5 channels

作者：Matamoros Marcos; Perez Hernandez Marta; Guerrero Serna Guadalupe; Amoros Irene; Barana Adriana; Nunez Mercedes; Ponce Balbuena Daniela; Sacristan Sandra; Gomez Ricardo; Tamargo Juan; Caballero Ricardo; Jalife Jose; Delpon Eva

来源：Cardiovascular Research, 2016, 110(2): 279-290.

DOI：10.1093/cvr/cvw009

• Inward rectifier current
• Sodium current
• alpha 1-syntrophin
• Kir2.x

Aims 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.
Methods and 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 alpha 1-syntrophin. Nav1.5 N-terminal domain, by itself (the 132 as peptide) (Nter), exerts a 'chaperone-like' effect that increases sodium (I-Na) and inward rectifier potassium (I-Ki) 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-I-Na density modulation. Moreover, results in rat and human atrial myocytes demonstrate that binding to alpha 1-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.

• 出版日期2016-5-15