title: A splice variant of the two-pore domain potassium channel TREK-1 with only one pore domain reduces the surface expression of full-length TREK-1 channels.
abstract: We have identified a novel splice variant of the human and rat two-pore domain potassium (K2P) channel TREK-1. The splice variant TREK-1e results from skipping of exon 5, which causes a frame shift in exon 6. The frame shift produces a novel C-terminal amino acid sequence and a premature termination of translation, which leads to a loss of transmembrane domains M3 and M4 and of the second pore domain. RT-PCR experiments revealed a preferential expression of TREK-1e in kidney, adrenal gland, and amygdala. TREK-1e was nonfunctional when expressed in Xenopus oocytes. However, both the surface expression and the current density of full-length TREK-1 were reduced by co-expression of TREK-1e. Live cell imaging in COS-7 cells transfected with GFP-tagged TREK-1e showed that this splice variant was retained in the endoplasmic reticulum (ER). Attachment of the C-terminus of TREK-1e to two different reporter proteins (Kir2.1 and CD8) led to a strong reduction in the surface expression of these fusion proteins. Progressive truncation of the C-terminus of TREK-1e in these reporter constructs revealed a critical region (amino acids 198 to 205) responsible for the intracellular retention. Mutagenesis experiments indicated that amino acids I204 and W205 are key residues mediating the ER retention of TREK-1e. Our results suggest that the TREK-1e splice variant may interfere with the vesicular traffic of full-length TREK-1 channels from the ER to the plasma membrane. Thus, TREK-1e might modulate the copy number of functional TREK-1 channels at the cell surface, providing a novel mechanism for fine tuning of TREK-1 currents.
authors.affiliation: Institute for Physiology and Pathophysiology, Cell Physiology, University of Marburg, Marburg, Germany, rinne@staff.uni-marburg.de.
authors.forename: Susanne
authors.initials: S
authors.lastname: Rinné
authors.forename: Vijay
authors.initials: V
authors.lastname: Renigunta
authors.forename: Günter
authors.initials: G
authors.lastname: Schlichthörl
authors.forename: Marylou
authors.initials: M
authors.lastname: Zuzarte
authors.forename: Stefan
authors.initials: S
authors.lastname: Bittner
authors.forename: Sven G
authors.initials: SG
authors.lastname: Meuth
authors.forename: Niels
authors.initials: N
authors.lastname: Decher
authors.forename: Jürgen
authors.initials: J
authors.lastname: Daut
authors.forename: Regina
authors.initials: R
authors.lastname: Preisig-Müller
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics* / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000235:genetics*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020798:Two-Hybrid System Techniques
chemical_list: D024683:Potassium Channels, Tandem Pore Domain; D020033:Protein Isoforms; C103742:potassium channel protein TREK-1