In vivo and in vitro functional characterization of Andersen's syndrome mutations.
The inward rectifier K(+) channel Kir2.1 carries all Andersen's syndrome mutations identified to date. Patients exhibit symptoms of periodic paralysis, cardiac dysrhythmia and multiple dysmorphic features. Here, we report the clinical manifestations found in three families with Andersen's syndrome. Molecular genetics analysis identified two novel missense mutations in the KCNJ2 gene leading to amino acid changes C154F and T309I of the Kir2.1 open reading frame. Patch clamp experiments showed that the two mutations produced a loss of channel function. When co-expressed with Kir2.1 wild-type (WT) channels, both mutations exerted a dominant-negative effect leading to a loss of the inward rectifying K(+) current. Confocal microscopy imaging in HEK293 cells is consistent with a co-assembly of the EGFP-fused mutant proteins with WT channels and proper traffick to the plasma membrane to produce silent channels alone or as hetero-tetramers with WT. Functional expression in C2C12 muscle cell line of newly as well as previously reported Andersen's syndrome mutations confirmed that these mutations act through a dominant-negative effect by altering channel gating or trafficking. Finally, in vivo electromyographic evaluation showed a decrease in muscle excitability in Andersen's syndrome patients. We hypothesize that Andersen's syndrome-associated mutations and hypokalaemic periodic paralysis-associated calcium channel mutations may lead to muscle membrane hypoexcitability via a common mechanism.
Bendahhou
Saïd
S
Université de Nice Sophia Antipolis, UMR 6097 CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, 660 Route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France. bendahhou@ipmc.cnrs.fr
Fournier
Emmanuel
E
Sternberg
Damien
D
Bassez
Guillaume
G
Furby
Alain
A
Sereni
Carole
C
Donaldson
Matthew R
MR
Larroque
Marie-Madeleine
MM
Fontaine
Bertrand
B
Barhanin
Jacques
J
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004576:Electromyography; D006801:Humans; D007668:Kidney / Q000166:cytology; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D032342:Muscle Cells / Q000166:cytology / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology; D020125:Mutation, Missense; D010245:Paralyses, Familial Periodic / Q000235:genetics*; D018408:Patch-Clamp Techniques; D010375:Pedigree; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000378:metabolism*
C489457:KCNJ2 protein, human; D024661:Potassium Channels, Inwardly Rectifying