TY - JOUR
T1 - Mechanism of loss of Kv11.1 K+ current in mutant T421M-Kv11.1-expressing rat ventricular myocytes
T2 - Interaction of trafficking and gating
AU - Balijepalli, Sadguna Y.
AU - Lim, Evi
AU - Concannon, Sarah P.
AU - Chew, Chen L.
AU - Holzem, Kassandra E.
AU - Tester, David J.
AU - Ackerman, Michael J.
AU - Delisle, Brian P.
AU - Balijepalli, Ravi C.
AU - January, Craig T.
PY - 2012/12/11
Y1 - 2012/12/11
N2 - BACKGROUND: Type 2 long QT syndrome involves mutations in the human ether a-go-go-related gene (hERG or KCNH2). T421M, an S1 domain mutation in the Kv11.1 channel protein, was identified in a resuscitated patient. We assessed its biophysical, protein trafficking, and pharmacological mechanisms in adult rat ventricular myocytes. METHODS AND RESULTS: Isolated adult rat ventricular myocytes were infected with wild-type (WT)-Kv11.1- and T421M-Kv11.1-expressing adenovirus and analyzed with the use of patch clamp, Western blot, and confocal imaging techniques. Expression of WT-Kv11.1 or T421M-Kv11.1 produced peak tail current (IKv11.1) of 8.78±1.18 and 1.91±0.22 pA/pF, respectively. Loss of mutant IKv11.1 resulted from (1) a partially trafficking-deficient channel protein with reduced cell surface expression and (2) altered channel gating with a positive shift in the voltage dependence of activation and altered kinetics of activation and deactivation. Coexpression of WT+T421M-Kv11.1 resulted in heterotetrameric channels that remained partially trafficking deficient with only a minimal increase in peak IKv11.1 density, whereas the voltage dependence of channel gating became WT-like. In the adult rat ventricular myocyte model, both WT-Kv11.1 and T421M-Kv11.1 channels responded to β-adrenergic stimulation by increasing IKv11.1. CONCLUSIONS: The T421M-Kv11.1 mutation caused a loss of IKv11.1 through interactions of abnormal protein trafficking and channel gating. Furthermore, for coexpressed WT+T421M-Kv11.1 channels, different dominant-negative interactions govern protein trafficking and ion channel gating, and these are likely to be reflected in the clinical phenotype. Our results also show that WT and mutant Kv11.1 channels responded to β-adrenergic stimulation.
AB - BACKGROUND: Type 2 long QT syndrome involves mutations in the human ether a-go-go-related gene (hERG or KCNH2). T421M, an S1 domain mutation in the Kv11.1 channel protein, was identified in a resuscitated patient. We assessed its biophysical, protein trafficking, and pharmacological mechanisms in adult rat ventricular myocytes. METHODS AND RESULTS: Isolated adult rat ventricular myocytes were infected with wild-type (WT)-Kv11.1- and T421M-Kv11.1-expressing adenovirus and analyzed with the use of patch clamp, Western blot, and confocal imaging techniques. Expression of WT-Kv11.1 or T421M-Kv11.1 produced peak tail current (IKv11.1) of 8.78±1.18 and 1.91±0.22 pA/pF, respectively. Loss of mutant IKv11.1 resulted from (1) a partially trafficking-deficient channel protein with reduced cell surface expression and (2) altered channel gating with a positive shift in the voltage dependence of activation and altered kinetics of activation and deactivation. Coexpression of WT+T421M-Kv11.1 resulted in heterotetrameric channels that remained partially trafficking deficient with only a minimal increase in peak IKv11.1 density, whereas the voltage dependence of channel gating became WT-like. In the adult rat ventricular myocyte model, both WT-Kv11.1 and T421M-Kv11.1 channels responded to β-adrenergic stimulation by increasing IKv11.1. CONCLUSIONS: The T421M-Kv11.1 mutation caused a loss of IKv11.1 through interactions of abnormal protein trafficking and channel gating. Furthermore, for coexpressed WT+T421M-Kv11.1 channels, different dominant-negative interactions govern protein trafficking and ion channel gating, and these are likely to be reflected in the clinical phenotype. Our results also show that WT and mutant Kv11.1 channels responded to β-adrenergic stimulation.
KW - Arrhythmia
KW - Dominant negative
KW - Ion channels
KW - Long QT syndrome
KW - Myocytes
KW - Protein trafficking
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UR - http://www.scopus.com/inward/citedby.url?scp=84870910786&partnerID=8YFLogxK
U2 - 10.1161/CIRCULATIONAHA.112.118018
DO - 10.1161/CIRCULATIONAHA.112.118018
M3 - Article
C2 - 23136156
AN - SCOPUS:84870910786
SN - 0009-7322
VL - 126
SP - 2809
EP - 2818
JO - Circulation
JF - Circulation
IS - 24
ER -