Function, subcellular localization and assembly of a novel mutation of KCNJ2 in Andersen's syndrome.
Andersen's syndrome (AS) (which is characterized by periodic paralysis, cardiac arrhythmias and dysmorphic features), a hereditary disease, and missense mutations of KCNJ2 (which encodes an inward rectifying potassium channel) have been reported recently. We performed clinical and molecular analyses of a patient with AS, and found a novel mutation (G215D) of KCNJ2. Twelve-lead electrocardiography revealed a long QT interval and frequent premature ventricular contractions, and polymorphic ventricular tachycardia was induced by programmed electrical stimulation. Use of a conventional whole-cell patch-clamp system with COS7 cells demonstrated that the G215D mutant was non-functional, and that co-expression of wild type (WT)- and mutant-KCNJ2 shows a dominant negative effect on both inward and outward currents. We performed confocal laser scanning microscopy to assess the cellular trafficking of WT- and mutant-KCNJ2 subunits tagged with yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP), respectively. Tagging with the YFP did not affect the channel function of WT-KCNJ2 and both proteins showed similar plasma membrane fluorescence patterns. Furthermore, the result of fluorescence resonance energy transfer (FRET) studies at the plasma membrane region suggested that both YFP-tagged WT- and CFP-tagged mutant-KCNJ2 combine to construct a hetero-multimer of the potassium channel. In conclusion, the G215D mutant of KCNJ2 is distributed normally in the plasma membrane, but exhibits a dominant-negative effect and reduces the Kir2.1 current, presumably due to hetero-multimer construction.
Hosaka
Yukio
Y
Division of Cardiology, Niigata University Graduate School of Medical and Dental Sciences, Asahimachi 1-754, Niigata 951-8510, Japan. hosaka@med.niigata-u.ac.jp
Hanawa
Haruo
H
Washizuka
Takashi
T
Chinushi
Masaomi
M
Yamashita
Fumio
F
Yoshida
Tsuyoshi
T
Komura
Satoru
S
Watanabe
Hiroshi
H
Aizawa
Yoshifusa
Y
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D004252:DNA Mutational Analysis; D005260:Female; D031541:Fluorescence Resonance Energy Transfer; D018014:Gene Transfer Techniques; D006011:Glycogen Storage Disease Type IV / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D020125:Mutation, Missense; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000378:metabolism
D024661:Potassium Channels, Inwardly Rectifying