Novel KCNA5 mutation implicates tyrosine kinase signaling in human atrial fibrillation - PubMed (original) (raw)

Novel KCNA5 mutation implicates tyrosine kinase signaling in human atrial fibrillation

Tao Yang et al. Heart Rhythm. 2010 Sep.

Abstract

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 I(Kur) 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 approximately 60% decreased I(Kur) versus wild-type (WT) (75 +/- 8 pA/pF vs 180 +/- 15 pA/pF, P <.01) and dominant-negative effect on WT current (105 +/- 10 pA/pF, P <.01). Pretreatment with the Src inhibitor PP2 prevented v-Src TK from 90% suppressed WT current. In contrast, the mutant channel displayed no response to v-Src TK.

Conclusion: Our data implicate abnormal atrial repolarization control due to variable TK signaling as a mechanism in familial AF and thereby suggest a role for modulation of this pathway in AF and its treatment.

Keywords: KCNA5 channel; familial atrial fibrillation; genetics; tyrosine kinase; variants.

Copyright 2010 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

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Figures

Figure 1

Figure 1

A, family pedigree of Vanderbilt AF 579. Solid symbols denote AF, and open symbols individuals without a documented history of AF. Male subjects are shown as squares and female subjects as circles. The proband (arrow) and the presence (+) or absence (−) of the KCNA5 71-81del are indicated. B, location of the indel in the KCNA5 protein and a portion of the KCNA5 N-terminus amino acid showing the indel mutant sequence in red.

Figure 2

Figure 2

The 71-81del in the N-terminus of KCNA5 expressed a reduced current. Panels A, B and C show wild-type (WT), the 71-81del and the WT+71-81 del currents respectively with a dominant negative effect. Panels D and E summarize both steady-state and tail currents in the three groups.

Figure 3

Figure 3

A tyrosine kinase (TK) isoform v-Src coexpressed with KCNA5 suppressed WT current but had no effect on the mutant 71-81del expressed current. A, WT current; B, coexpression of v-Src with WT KCNA5 channel reduced the current; C, 71-81del expressed reduced the current; D, the 71-81del fail to respond to v-Src; E, current-voltage relationships in the four groups.

Figure 4

Figure 4

Suppression of KCNA5 current by Src is prevented by the selective Src inhibitor PP2 (10 μM). A, intracellular addition of v-Src (30 u/ml) progressively suppressed WT KCNA5 current elicited by repetitive pulses to +50 mV from −80 mV with the protocol shown. B, intracellular Src application did not affect the 71-81del expressed current. C, effects of intracellular Src application on WT and the 71-81del currents. D, pretreatment with PP2 (10 μM) for 30 minutes prevented the intracellular Src-induced suppression of WT current. E, intracellular Src addition did not alter the 71-81del expressed current. F, effects of intracellular Src application on WT and 71-81del currents in the presence PP2 pretreatment. The number of cells in each group was 6. Statistical differences among these groups are shown.

Comment in

References

    1. Benjamin EJ, Wolf PA, D’Agostino RB, Silbershatz H, Kannel WB, Levy D. Impact of atrial fibrillation on the risk of death: the Framingham Heart Study. Circulation. 1998;98(10):946–952. - PubMed
    1. Darbar D, Herron KJ, Ballew JD, Jahangir A, Gersh BJ, Shen WK, Hammill SC, Packer DL, Olson TM. Familial atrial fibrillation is a genetically heterogeneous disorder. J Am Coll Cardiol. 2003;41:2185–2192. - PubMed
    1. Ellinor PT, Yoerger DM, Ruskin JN, Macrae CA. Familial aggregation in lone atrial fibrillation. Hum Genet. 2005:1–6. - PubMed
    1. Arnar DO, Thorvaldsson S, Manolio TA, Thorgeirsson G, Kristjansson K, Hakonarson H, Stefansson K. Familial aggregation of atrial fibrillation in Iceland. Eur Heart J. 2006;27:708–712. - PubMed
    1. Darbar D, Kannankeril PJ, Donahue BS, Kucera G, Stubblefield T, Haines JL, George AL, Jr, Roden DM. Cardiac sodium channel (SCN5A) variants associated with atrial fibrillation. Circulation. 2008;117:1927–1935. - PMC - PubMed

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