Defective potassium channel Kir2.1 trafficking underlies Andersen-Tawil syndrome.
Andersen-Tawil syndrome is a skeletal and cardiac muscle disease with developmental features caused by mutations in the inward rectifier K+ channel gene KCNJ2. Patients harboring these mutations exhibit extremely variable expressivities. To explore whether these mutations can be correlated with a specific patient phenotype, we expressed both wild-type (WT) and mutant genes cloned into a bi-cistronic vector. Functional expression in human embryonic kidney 293 cells showed that none of the mutant channels express current when present alone. When co-expressed with WT channels, only construct V302M-WT yields inward current. Confocal microscopy fluorescence revealed three patterns of channel expression in the cell: 1) mutations D71V, N216H, R218Q, and pore mutations co-assemble and co-localize to the membrane with the WT and exert a dominant-negative effect on the WT channels; 2) mutation V302M leads to channels that lose their ability to co-assemble with WT and traffic to the cell surface; 3) deletions Delta 95-98 and Delta 314-315 lead to channels that do not traffic to the membrane but retain their ability to co-assemble with WT channels. These data show that the Andersen-Tawil syndrome phenotype may occur through a dominant-negative effect as well as through haplo-insufficiency and reveal amino acids critical in trafficking and conductance of the inward rectifier K+ channels.
Bendahhou
Saïd
S
Department of Human Molecular Biology and Genetics, University of Utah, Salt Lake City, Utah 84112, USA. bendahhou@ipmc.cnrs.fr
Donaldson
Matthew R
MR
Plaster
Nikki M
NM
Tristani-Firouzi
Martin
M
Fu
Ying-Hui
YH
Ptácek
Louis J
LJ
D019943:Amino Acid Substitution; D002460:Cell Line; D004594:Electrophysiology; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics*; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D009154:Mutation / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000172:deficiency / Q000235:genetics*; D021381:Protein Transport / Q000235:genetics; D014162:Transfection
D024661:Potassium Channels, Inwardly Rectifying