title: Kir2.6 regulates the surface expression of Kir2.x inward rectifier potassium channels.
abstract: Precise trafficking, localization, and activity of inward rectifier potassium Kir2 channels are important for shaping the electrical response of skeletal muscle. However, how coordinated trafficking occurs to target sites remains unclear. Kir2 channels are tetrameric assemblies of Kir2.x subunits. By immunocytochemistry we show that endogenous Kir2.1 and Kir2.2 are localized at the plasma membrane and T-tubules in rodent skeletal muscle. Recently, a new subunit, Kir2.6, present in human skeletal muscle, was identified as a gene in which mutations confer susceptibility to thyrotoxic hypokalemic periodic paralysis. Here we characterize the trafficking and interaction of wild type Kir2.6 with other Kir2.x in COS-1 cells and skeletal muscle in vivo. Immunocytochemical and electrophysiological data demonstrate that Kir2.6 is largely retained in the endoplasmic reticulum, despite high sequence identity with Kir2.2 and conserved endoplasmic reticulum and Golgi trafficking motifs shared with Kir2.1 and Kir2.2. We identify amino acids responsible for the trafficking differences of Kir2.6. Significantly, we show that Kir2.6 subunits can coassemble with Kir2.1 and Kir2.2 in vitro and in vivo. Notably, this interaction limits the surface expression of both Kir2.1 and Kir2.2. We provide evidence that Kir2.6 functions as a dominant negative, in which incorporation of Kir2.6 as a subunit in a Kir2 channel heterotetramer reduces the abundance of Kir2 channels on the plasma membrane.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology and the Neuroscience Research Institute, University of California, Santa Barbara, California 93106, USA.
authors.forename: Lior
authors.initials: L
authors.lastname: Dassau
authors.forename: Lisa R
authors.initials: LR
authors.lastname: Conti
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Radeke
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Ptáček
authors.forename: Carol A
authors.initials: CA
authors.lastname: Vandenberg
mesh_terms: D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D020514:Hypokalemic Periodic Paralysis / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D009154:Mutation; D024661:Potassium Channels, Inwardly Rectifying / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D013958:Thyroid Crisis / Q000235:genetics / Q000378:metabolism
chemical_list: C546860:KCNJ18 protein, human; C489457:KCNJ2 protein, human; C489463:Kir2.2 channel; D024661:Potassium Channels, Inwardly Rectifying