An Isoform of Nedd4-2 Plays a Pivotal Role in Electrophysiological Cardiac Abnormalities

Abstract

We have previously shown that neural precursor cell-expressed developmentally downregulated gene 4-2 (Nedd4-2) isoforms with a C2 domain are closely related to ubiquitination of epithelial sodium channel (ENaC), resulting in salt-sensitive hypertension by Nedd4-2 C2 targeting in mice. The sodium voltage-gated channel alpha subunit 5 (SCN5A) gene encodes the α subunit of the human cardiac voltage-gated sodium channel (I Na), and the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene encodes rapidly activating delayed rectifier K channels (I Kr). Both ion channels have also been shown to bind to Nedd4-2 via a conserved Proline-Tyrosine (PY) motif in C-terminal with subsequent ubiquitination and degradation by proteasome. Therefore, loss of Nedd4-2 C2 isoform might be involved in electrophysiological impairment under various conditions. We demonstrate here that Nedd4-2 C2 isoform causes cardiac conduction change in resting condition as well as proarrhythmic change after acute myocardial infarction (MI). The Nedd4-2 C2 knockout (KO) mice showed bradycardia, prolonged QRS, QT intervals, and suppressed PR interval in resting condition. In addition, enhancement of T peak/T end interval was found in mice with surgical ligation of the distal left coronary artery. Morphological analyses based on both ultrasonography of the living heart, as well as histopathological findings revealed that Nedd4-2 C2 KO mice show no significant structural changes from wild-type littermates under resting conditions. These results suggested that Nedd4-2 with C2 domain might play an important role in cardio-renal syndrome through post-transcriptional modification of both ENaC and cardiac ion channels, which are critical for kidney and heart functions.

Functional Consequences of the SCN5A-p.Y1977N Mutation within the PY Ubiquitylation Motif: Discrepancy between HEK293 Cells and Transgenic Mice

“…Recent findings in HEK293 cells and neonatal rat cardiomyocytes indicate that increased calcium levels (as observed during heart failure) enhance Nedd4-2 expression and consequent ubiquitylation and downregulation of Na v 1.5 [23]. Furthermore, mice deficient for the Nedd4-2 C2 isoform (isoform containing a C2 domain in the N-terminus) displayed electrocardiographic signs of cardiac conduction and repolarization abnormalities in the absence of overt cardiac structural abnormalities [24]. However, no molecular or functional measurements of ion channel expression/function were performed, and it is unclear to what extent the observed alterations are primary or secondary to the renal phenotype present in these mice [24].…”

“…Furthermore, mice deficient for the Nedd4-2 C2 isoform (isoform containing a C2 domain in the N-terminus) displayed electrocardiographic signs of cardiac conduction and repolarization abnormalities in the absence of overt cardiac structural abnormalities [24]. However, no molecular or functional measurements of ion channel expression/function were performed, and it is unclear to what extent the observed alterations are primary or secondary to the renal phenotype present in these mice [24]. Our current study is the first to directly investigate the functional in vivo role of the PY-motif in the cardiomyocyte environment.…”

Regulators of Epithelial Sodium Channels in Aldosterone-Sensitive Distal Nephrons (ASDN): Critical Roles of Nedd4L/Nedd4-2 and Salt-Sensitive Hypertension

“…Additionally, to determine detailed characteristics of salt-sensitive hypertension of the mice, we tried a mineral corticoid receptor antagonist treatment for Nedd4-2 C2 KO mice. Finally, us and other authors [63,64], have previously found that Nedd4-2 C2 KO mice showed eplerenone-resistant salt-sensitive hypertension [65] and enhanced electrophysiological abnormalities, after myocardial infarction [66], suggesting a pivotal role of the Nedd4-2 isoform with C2 domain for cardio-renal association, with regards to target-organ damages of the subjects with salt-sensitive hypertension.…”

“…Ultimately, we found that the lack of single isoform of the gene caused a significant change in vivo, resulting in a higher oral salt intake suppressing sodium excretion in urine and elevated blood pressures, the pathophysiology of which is called "salt-sensitive" [62]. In accordance with human genetic studies, the impairment of tubular sodium transport might be pivotal in the onset and development of salt-sensitive hypertension [65,66].…”

The Role of HECT-Type E3 Ligase in the Development of Cardiac Disease

“…Therefore, calcium-mediated increase in NEDD4-2 induced Nav1.5 ubiquitylation with a resultant reduction in Nav1.5 cardiomyocyte membrane density in HF [ 186 ]. Mutations in the gene encoding Nav1.5, SCN5A, have been associated with various arrhythmic disorders such as long QT syndrome, Brugada syndrome, and sick sinus syndrome, indicating the association of NEDD4-2 with cardiac arrhythmia [ 209 , 210 ].…”