Involvement of caveolin in low K+-induced endocytic degradation of cell-surface human ether-a-go-go-related gene (hERG) channels.
Reduction in the rapidly activating delayed rectifier K(+) channel current (I(Kr)) due to either mutations in the human ether-a-go-go-related gene (hERG) or drug block causes inherited or drug-induced long QT syndrome. A reduction in extracellular K(+) concentration ([K(+)](o)) exacerbates long QT syndrome. Recently, we demonstrated that lowering [K(+)](o) promotes degradation of I(Kr) in rabbit ventricular myocytes and of the hERG channel stably expressed in HEK 293 cells. In this study, we investigated the degradation pathways of hERG channels under low K(+) conditions. We demonstrate that under low K(+) conditions, mature hERG channels and caveolin-1 (Cav1) displayed a parallel time-dependent reduction. Mature hERG channels coprecipitated with Cav1 in co-immunoprecipitation analysis, and internalized hERG channels colocalized with Cav1 in immunocytochemistry analysis. Overexpression of Cav1 accelerated internalization of mature hERG channels in 0 mM K(+)(o), whereas knockdown of Cav1 impeded this process. In addition, knockdown of dynamin 2 using siRNA transfection significantly impeded hERG internalization and degradation under low K(+)(o) conditions. In cultured neonatal rat ventricular myocytes, knockdown of caveolin-3 significantly impeded low K(+)(o)-induced reduction of I(Kr). Our data indicate that a caveolin-dependent endocytic route is involved in low K(+)(o)-induced degradation of mature hERG channels.
Massaeli
Hamid
H
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Sun
Tao
T
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Li
Xian
X
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Shallow
Heidi
H
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Wu
Jimmy
J
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Xu
Jianmin
J
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Li
Wentao
W
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Hanson
Christian
C
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Guo
Jun
J
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Zhang
Shetuan
S
Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada. Electronic address: shetuan.zhang@queensu.ca.
D000818:Animals; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D034285:Dynamin II / Q000235:genetics / Q000378:metabolism; D000072237:ERG1 Potassium Channel; D004705:Endocytosis; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006352:Heart Ventricles / Q000378:metabolism*; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics / Q000378:metabolism; D008297:Male; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley
C495540:CAV1 protein, human; C495537:Cav1 protein, rat; D051242:Caveolin 1; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D034741:RNA, Small Interfering; D034285:Dynamin II; D011188:Potassium