title: Repulsion between Lys258 and upstream arginines explains the missorting of the AQP2 mutant p.Glu258Lys in nephrogenic diabetes insipidus.
abstract: Regulation of body water homeostasis occurs by the vasopressin-dependent sorting of aquaporin-2 (AQP2) water channels to and from the apical membrane of renal principal cells. Mutations in AQP2 cause autosomal nephrogenic diabetes insipidus (NDI), a disease that renders the kidney unresponsive to vasopressin, resulting in polyuria and polydipsia. The AQP2 mutant c.772G>A; p.Glu258Lys (AQP2-E258K) causes dominant NDI by oligomerizing with wild-type AQP2 and missorting of this AQP2 complex to multivesicular bodies instead of the apical membrane. The motif causing this missorting of AQP2-E258K was identified here. Functional analyses and plasma membrane expression studies of truncation mutants in oocytes revealed that AQP2-E258K shortened to Leu259 is still intracellular retained. Alanine scanning and glutamic acid to arginine exchanges revealed increased function and plasma membrane expression for AQP2-E258K mutants with the following additional changes: Leu259Ala, Arg252Glu, Arg253Glu, or Arg252Ala-Arg254Ala, or for the AQP2 mutant p.Glu258Ala, indicating that the motif RRRxxxK(258)L confers AQP2-E258K retention. Fusion of this motif to aquaporin-1 also resulted in missorting of that water channel, indicating that this retention motif is transferable. In conclusion, our data reveal that the RRRxxxKL motif and repulsion between K258 and the arginine-triplet within this motif are the primary cause of missorting of AQP2-E258K in NDI.
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Erik-Jan
authors.initials: EJ
authors.lastname: Kamsteeg
authors.forename: Monique
authors.initials: M
authors.lastname: Stoffels
authors.forename: Grazia
authors.initials: G
authors.lastname: Tamma
authors.forename: Irene B M
authors.initials: IB
authors.lastname: Konings
authors.forename: Peter M T
authors.initials: PM
authors.lastname: Deen
mesh_terms: D000595:Amino Acid Sequence; D051399:Aquaporin 2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001120:Arginine / Q000235:genetics*; D002451:Cell Compartmentation; D018500:Diabetes Insipidus, Nephrogenic / Q000235:genetics*; D005998:Glycine / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008239:Lysine / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D017386:Sequence Homology, Amino Acid
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D001120:Arginine; D008239:Lysine; D005998:Glycine