Analysis of the cyclic nucleotide binding domain of the HERG potassium channel and interactions with KCNE2.
Mutations in the cyclic nucleotide binding domain (CNBD) of the human ether-a-go-go-related gene (HERG) K+ channel are associated with LQT2, a form of hereditary Long QT syndrome (LQTS). Elevation of cAMP can modulate HERG K+ channels both by direct binding and indirect regulation through protein kinase A. To assess the physiological significance of cAMP binding to HERG, we introduced mutations to disrupt the cyclic nucleotide binding domain. Eight mutants including two naturally occurring LQT2 mutants V822M and R823W were constructed. Relative cAMP binding capacity was reduced or absent in CNBD mutants. Mutant homotetramers carry little or no K+ current despite normal protein abundance and surface expression. Co-expression of mutant and wild-type HERG resulted in currents with altered voltage dependence but without dominant current suppression. The data from co-expression of V822M and wild-type HERG best fit a model where one normal subunit within a tetramer allows nearly normal current expression. The presence of KCNE2, an accessory protein that associates with HERG, however, conferred a partially dominant current suppression by CNBD mutants. Thus KCNE2 plays a pivotal role in determining the phenotypic severity of some forms of LQT2, which suggests that the CNBD of HERG may be involved in its interaction with KCNE2.
Section of Molecular Cardiology, Departments of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J
J
Cui
A
A
Kagan
D
D
Qin
J
J
Mathew
Y F
YF
Melman
T V
TV
McDonald
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D027682:Cation Transport Proteins; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism*; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D007700:Kinetics; D008133:Long QT Syndrome / Q000235:genetics; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010641:Phenotype; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; D014162:Transfection
D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D046911:Macromolecular Substances; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; C059983:potassium channel protein I(sk); D000242:Cyclic AMP