title: A dual phosphorylation switch controls 14-3-3-dependent cell surface expression of TASK-1.
abstract: The transport of the K(+) channels TASK-1 and TASK-3 (also known as KCNK3 and KCNK9, respectively) to the cell surface is controlled by the binding of 14-3-3 proteins to a trafficking control region at the extreme C-terminus of the channels. The current model proposes that phosphorylation-dependent binding of 14-3-3 sterically masks a COPI-binding motif. However, the direct effects of phosphorylation on COPI binding and on the binding parameters of 14-3-3 isoforms are still unknown. We find that phosphorylation of the trafficking control region prevents COPI binding even in the absence of 14-3-3, and we present a quantitative analysis of the binding of all human 14-3-3 isoforms to the trafficking control regions of TASK-1 and TASK-3. Surprisingly, the affinities of 14-3-3 proteins for TASK-1 are two orders of magnitude lower than for TASK-3. Furthermore, we find that phosphorylation of a second serine residue in the C-terminus of TASK-1 inhibits 14-3-3 binding. Thus, phosphorylation of the trafficking control region can stimulate or inhibit transport of TASK-1 to the cell surface depending on the target serine residue. Our findings indicate that control of TASK-1 trafficking by COPI, kinases, phosphatases and 14-3-3 proteins is highly dynamic.
authors.affiliation: Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, Göttingen 37073, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kilisch
authors.affiliation: Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, Göttingen 37073, Germany.
authors.forename: Olga
authors.initials: O
authors.lastname: Lytovchenko
authors.affiliation: Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, Göttingen 37073, Germany.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Arakel
authors.affiliation: Department of Biochemistry, University of Kassel, Kassel 34132, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bertinetti
authors.affiliation: Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, Göttingen 37073, Germany Max-Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany blanche.schwappach@med.uni-goettingen.de.
authors.forename: Blanche
authors.initials: B
authors.lastname: Schwappach
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane; D002522:Chlorocebus aethiops; D020755:Coat Protein Complex I / Q000378:metabolism; D006801:Humans; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D024683:Potassium Channels, Tandem Pore Domain / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D011499:Protein Processing, Post-Translational; D021381:Protein Transport
chemical_list: D048948:14-3-3 Proteins; D020755:Coat Protein Complex I; D009419:Nerve Tissue Proteins; D024683:Potassium Channels, Tandem Pore Domain; C420132:potassium channel subfamily K member 3
keywords: 14-3-3 protein; COPI; Endoplasmic reticulum; Golgi; Membrane trafficking; Phosphorylation; Protein kinase A; TASK-1; Two-pore-domain K+ channel