title: Impaired trafficking of mutated AVP prohormone in cells expressing rare disease genes causing autosomal dominant familial neurohypophyseal diabetes insipidus.
abstract: OBJECTIVE
  Two different mutations in the arginine vasopressin (AVP) gene associated with autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) predict Y21H (AVP2) and V67A (NP36) amino acid substitutions of the AVP prohormone. They are unique in that they change, respectively, the AVP moiety and a region of the neurophysin II domain not so far affected by any mutations. To test whether they affect the cellular handling of the AVP prohormone in a similar manner to previously investigated mutations, they were examined by heterologous expression in cell lines.
  
  
  RESULTS
  Both mutations resulted in significantly reduced amounts of immunoreactive AVP in the cell culture medium as determined by radioimmunoassay analysis. Metabolic labelling combined with immunoprecipitation demonstrated that processing and secretion of the mutant prohormones was reduced but not prevented. Finally, confocal laser scanning microscopy showed that normal AVP prohormone and/or its processed products were localized in the tips of the cellular processes, whereas both mutant prohormones were accumulated in the endoplasmic reticulum (ER) and in the case of the V67A prohormone, also in perinuclear structures outside the ER.
  
  
  CONCLUSIONS
  Both mutations result in reduced AVP prohormone processing and secretion probably due to retention in the ER. This supports, at least partly, the hypothesis that the mutations lead to the production of a mutant hormone precursor that fails to fold and/or dimerize properly and, as a consequence, is retained by the ER protein quality control machinery. Perinuclear accumulation of the V67A prohormone outside the ER indicates that additional mechanisms could be involved.
authors.affiliation: Pediatric Research Laboratory, Aarhus University Hospital, Skejby Sygehus, Denmark.
authors.forename: Jane H
authors.initials: JH
authors.lastname: Christensen
authors.forename: Charlotte
authors.initials: C
authors.lastname: Siggaard
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Corydon
authors.forename: Gary L
authors.initials: GL
authors.lastname: Robertson
authors.forename: Niels
authors.initials: N
authors.lastname: Gregersen
authors.forename: Lars
authors.initials: L
authors.lastname: Bolund
authors.forename: Søren
authors.initials: S
authors.lastname: Rittig
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D045744:Cell Line, Tumor; D003470:Culture Media / Q000737:chemistry; D020790:Diabetes Insipidus, Neurogenic / Q000235:genetics* / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000737:chemistry; D005799:Genes, Dominant; D006801:Humans; D016014:Linear Models; D018613:Microscopy, Confocal; D009154:Mutation; D009481:Neurophysins / Q000032:analysis; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011498:Protein Precursors / Q000032:analysis / Q000235:genetics* / Q000378:metabolism
chemical_list: D003470:Culture Media; D009481:Neurophysins; D011498:Protein Precursors; D001127:Arginine Vasopressin