NaV1.6 dysregulation within myocardial T-tubules by D96V calmodulin enhances proarrhythmic sodium and calcium mishandling

Calmodulin (CaM) plays critical roles in cardiomyocytes, regulating Na+ (NaV) and L-type Ca2+ channels (LTCC). LTCC dysregulation by mutant CaMs has been implicated in action potential duration (APD) prolongation and arrhythmogenic long QT (LQT) syndrome. Intriguingly, D96V-CaM prolongs APD more than other LQT-associated CaMs despite inducing comparable levels of LTCC dysfunction, suggesting dysregulation of other depolarizing channels. Here, we provide evidence implicating NaV dysregulation within transverse (T)-tubules in D96V-CaM-associated arrhythmias. D96V-CaM induces pro-arrhythmic late Na+ current (INa) by impairing inactivation of NaV1.6, but not the predominant cardiac NaV isoform, NaV1.5. We investigated arrhythmia mechanisms using mice with cardiac-specific expression of D96V-CaM (cD96V). Super-resolution microscopy revealed close proximity of NaV1.6 and RyR2 within T-tubules. NaV1.6 density within these regions increased in cD96V relative to WT. Consistent with NaV1.6 dysreg..., , STORM: Zip file containing single molecule localization data from STORM
AP and Ca records: Zip file containing action potential (AP) and calcium imaging (Ca2+) records
4,9 ahTTX IC50: Zip file containing patch clamp records from dose-response (IC50) experiments for 4,9ah TTX blockade of human and mouse NaV1.5 and NaV1.6
AIP AP in cD96V: Zip file containing action potential (AP) records from cD96V myocytes incubated in Autocamtide-2-related inhibitory peptide, myristoylated (AIP)
Ca Sparks: Zip file containing records of Ca2+ sparks
Cardiac myocytes and CHO whole cell D96V-CaM INa: Zip file containing whole cell sodium current (INa) records from mouse cardiac myocytes and CHO cells dialyzed with WT-CaM and D96V-CaM
ECG: Zip file containing ECG data
Fibrosis: Zip file containing fibrosis assessment data
ICa: Zip file containing whole cell patch clamp records of Ca2+ current (ICa) in cD96V and cD96V x cNaV1.6KO myocytes
IPSC INa: Zip file containing whole cell patch clamp records of Na+ cu...