Functional effects of KCNE3 mutation and its role in the development of Brugada syndrome.
BACKGROUND
The Brugada Syndrome (BrS), an inherited syndrome associated with a high incidence of sudden cardiac arrest, has been linked to mutations in four different genes leading to a loss of function in sodium and calcium channel activity. Although the transient outward current (I(to)) is thought to play a prominent role in the expression of the syndrome, mutations in I(to)-related genes have not been identified as yet.


RESULTS
One hundred and five probands with BrS were screened for ion channel gene mutations using single strand conformation polymorphism (SSCP) electrophoresis and direct sequencing. A missense mutation (R99H) in KCNE3 (MiRP2) was detected in one proband. The R99H mutation was found 4/4 phenotype positive and 0/3 phenotype-negative family members. Chinese hamster ovary (CHO)-K1 cells were co-transfected using wild-type (WT) or mutant KCNE3 and either WT KCND3 or KCNQ1. Whole-cell patch clamp studies were performed after 48 hours. Interactions between Kv4.3 and KCNE3 were analyzed in co-immunoprecipitation experiments in human atrial samples. Co-transfection of R99H-KCNE3 with KCNQ1 produced no alteration in current magnitude or kinetics. However, co-transfection of R99H KCNE3 with KCND3 resulted in a significant increase in the I(to) intensity compared to WT KCNE3+KCND3. Using tissues isolated from left atrial appendages of human hearts, we also demonstrate that K(v)4.3 and KCNE3 can be co-immunoprecipitated.


CONCLUSIONS
These results provide definitive evidence for a functional role of KCNE3 in the modulation of I(to) in the human heart and suggest that mutations in KCNE3 can underlie the development of BrS.
Delpón
Eva
E
Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid, Spain.
Cordeiro
Jonathan M
JM
Núñez
Lucía
L
Thomsen
Poul Erik Bloch
PE
Guerchicoff
Alejandra
A
Pollevick
Guido D
GD
Wu
Yuesheng
Y
Kanters
Jørgen K
JK
Larsen
Carsten Toftager
CT
Hofman-Bang
Jacob
J
Burashnikov
Elena
E
Christiansen
Michael
M
Antzelevitch
Charles
C
D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000368:Aged; D053840:Brugada Syndrome / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D002478:Cells, Cultured; D002648:Child; D004247:DNA / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D047468:Immunoprecipitation; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D018408:Patch-Clamp Techniques; D010375:Pedigree; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics* / Q000378:metabolism; D055815:Young Adult
C418492:KCNE3 protein, human; D024642:Potassium Channels, Voltage-Gated; D004247:DNA