title: The identification of novel, high affinity AQP9 inhibitors in an intracellular binding site.
abstract: BACKGROUND
  The involvement of aquaporin (AQP) water and small solute channels in the etiology of several diseases, including cancer, neuromyelitis optica and body fluid imbalance disorders, has been suggested previously. Furthermore, results obtained in a mouse model suggested that AQP9 function contributes to hyperglycemia in type-2 diabetes. In addition, the physiological role of several AQP family members remains poorly understood. Small molecule inhibitors of AQPs are therefore desirable to further study AQP physiological and pathophysiological functions.
  
  
  METHODS
  The binding of recently established AQP9 inhibitors to a homology model of AQP9 was investigated by molecular dynamics simulations and molecular docking. Putative inhibitor binding sites identified with this procedure were modified by site-directed mutagenesis. Active compounds were measured in a mammalian cell water permeability assay of mutated AQP9 isoforms and tested for changes in inhibitory effects.
  
  
  METHODS
  Three independent cell lines were established for each mutated AQP9 isoform and functionality of mutant isoforms was established.
  
  
  RESULTS
  We have identified putative binding sites of recently established AQP9 inhibitors. This information facilitated successful identification of novel AQP9 inhibitors with low micromolar IC50 values in a cell based assay by in silico screening of a compound library targeting specifically this binding site.
  
  
  CONCLUSIONS
  We have established a successful strategy for AQP small molecule inhibitor identification. AQP inhibitors may be relevant as experimental tools, to enhance our understanding of AQP function, and in the treatment of various diseases.
authors: The Max Planck Institute for Biophysical Chemistry, Computational Biomolecular Dynamics Group, Göttingen, Germany.
authors: Sören J
authors: SJ
authors: Wacker
authors: Camilo
authors: C
authors: Aponte-Santamaría
authors: Per
authors: P
authors: Kjellbom
authors: Søren
authors: S
authors: Nielsen
authors: Bert L
authors: BL
authors: de Groot
authors: Michael
authors: M
authors: Rützler
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D045744:Cell Line, Tumor; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D054852:Small Molecule Libraries / Q000737:chemistry* / Q000378:metabolism; D040681:Structural Homology, Protein
chemical_list: C109669:AQP9 protein, human; C491638:Aqp9 protein, mouse; D020346:Aquaporins; D054852:Small Molecule Libraries