title: The role of monoubiquitination in endocytic degradation of human ether-a-go-go-related gene (hERG) channels under low K+ conditions.
abstract: A reduction in extracellular K(+) concentration ([K(+)](o)) causes cardiac arrhythmias and triggers internalization of the cardiac rapidly activating delayed rectifier potassium channel (I(Kr)) encoded by the human ether-a-go-go-related gene (hERG). We investigated the role of ubiquitin (Ub) in endocytic degradation of hERG channels stably expressed in HEK cells. Under low K(+) conditions, UbKO, a lysine-less mutant Ub that only supports monoubiquitination, preferentially interacted and selectively enhanced degradation of the mature hERG channels. Overexpression of Vps24 protein, also known as charged multivesicular body protein 3, significantly accelerated degradation of mature hERG channels, whereas knockdown of Vps24 impeded this process. Moreover, the lysosomal inhibitor bafilomycin A1 inhibited degradation of the internalized mature hERG channels. Thus, monoubiquitination directs mature hERG channels to degrade through the multivesicular body/lysosome pathway. Interestingly, the protease inhibitor lactacystin inhibited the low K(+)-induced hERG endocytosis and concomitantly led to an accumulation of monoubiquitinated mature hERG channels, suggesting that deubiquitination is also required for the endocytic degradation. Consistently, overexpression of the endosomal deubiquitinating enzyme signal transducing adaptor molecule-binding protein significantly accelerated whereas knockdown of endogenous signal transducing adaptor molecule-binding protein impeded degradation of the mature hERG channels under low K(+) conditions. Thus, monoubiquitin dynamically mediates endocytic degradation of mature hERG channels under low K(+) conditions.
authors.affiliation: Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.forename: Jun
authors.initials: J
authors.lastname: Guo
authors.forename: Heidi
authors.initials: H
authors.lastname: Shallow
authors.forename: Tonghua
authors.initials: T
authors.lastname: Yang
authors.forename: Jianmin
authors.initials: J
authors.lastname: Xu
authors.forename: Wentao
authors.initials: W
authors.lastname: Li
authors.forename: Christian
authors.initials: C
authors.lastname: Hanson
authors.forename: James G
authors.initials: JG
authors.lastname: Wu
authors.forename: Xian
authors.initials: X
authors.lastname: Li
authors.forename: Hamid
authors.initials: H
authors.lastname: Massaeli
authors.forename: Shetuan
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000072237:ERG1 Potassium Channel; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects / Q000502:physiology*
chemical_list: C498543:CHMP3 protein, human; D000072237:ERG1 Potassium Channel; D056827:Endosomal Sorting Complexes Required for Transport; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D025801:Ubiquitin; D011188:Potassium