Novel KCNA5 mutation implicates tyrosine kinase signaling in human atrial fibrillation

Background Emerging evidence has strongly implicated hereditary determinants for atrial fibrillation (AF). Loss-of-function mutations in KCNA5 encoding the ultrarapid delayed rectifier potassium current IKur have been identified in AF families. Objective The purpose of this study was to determine the clinical and biophysical phenotypes in a KCNA5 mutation with deletion of 11 amino acids in the N-terminus of the protein, which was identified in patients with lone AF. Methods Patients with AF confirmed by ECG were prospectively enrolled in the Vanderbilt AF Registry, which comprises clinical and genetic databases. A KCNA5 mutation was generated by mutagenesis for electrophysiologic characterization. Results We identified a novel 33-bp coding region deletion in two Caucasian probands. One proband was part of a kindred that included four other members with AF, and all were mutation carriers. The mutation results in deletion of 11 amino acids in the N-terminus of the protein, a proline-rich region as a binding site for Src homology 3 (SH3) domains associated with Src-family protein tyrosine kinase (TK) pathway. In transfected cells, the mutant caused ∼60% decreased IKur versus wild-type (WT) (75 ± 8 pA/pF vs 180 ± 15 pA/pF, P