C-terminal HERG (LQT2) mutations disrupt IKr channel regulation through 14-3-3epsilon.

Hum Mol Genet 2006 Oct 21;15(19):2888-902. Epub 2006 Aug 21.

Institute for Neural Signal Transduction, ZMNH, Department of Pediatrics, University Hospital Hamburg-Eppendorf, Hamburg, Germany.

Beta-adrenergic receptor-mediated cAMP or protein kinase A (PKA)-dependent modulation of cardiac potassium currents controls ventricular action potential duration (APD) at faster heart rates. HERG (KCNH2) gene mutations are associated with congenital long-QT syndrome (LQT2) and affect IKr activity, a key determinant in ventricular repolarization. Physical activity or emotional stress often triggers lethal arrhythmias in LQT2 patients. Beta-adrenergic stimulation of HERG channel activity is amplified and prolonged in vitro by the adaptor protein 14-3-3epsilon. In LQT2 families, we identified three novel heterozygous HERG mutations (G965X, R1014PfsX39, V1038AfsX21) in the C-terminus that led to protein truncation and loss of a PKA phosphorylation site required for binding of 14-3-3epsilon. When expressed in CHO cells, the mutants produced functional HERG channels with normal kinetic properties. We now provide evidence that HERG channel regulation by 14-3-3epsilon is of physiological significance in humans. Upon co-expression with 14-3-3epsilon, mutant channels still bound 14-3-3epsilon but did not respond with a hyperpolarizing shift in voltage dependence as seen in wild-type channels. Co-expression experiments of wild-type and mutant channels revealed dominant-negative behavior of all three HERG mutations. Simulations of the effects of sympathetic stimulation of HERG channel activity on the whole-cell action potential suggested a role in rate-dependent control of APD and an impaired ability of mutant cardiac myocytes to respond to a triggered event or an ectopic beat. In summary, the attenuated functional effects of 14-3-3epsilon on C-terminally truncated HERG channels demonstrate the physiological importance of coupling beta-adrenergic stimulation and HERG channel activity.

Download full-text PDF

Source
http://academic.oup.com/hmg/article/15/19/2888/630544/Ctermi
Publisher Site
http://dx.doi.org/10.1093/hmg/ddl230DOI Listing
October 2006
19 Reads

Publication Analysis

Top Keywords

herg channel
16
channel activity
12
stimulation herg
12
herg
9
regulation 14-3-3epsilon
8
beta-adrenergic stimulation
8
action potential
8
herg channels
8
herg mutations
8
channel regulation
8
mutant channels
8
14-3-3epsilon
7
channel
5
activity
5
channels
5
functional herg
4
binding 14-3-3epsilon
4
produced functional
4
cells mutants
4
mutants produced
4

Similar Publications