title: Plasma Membrane Abundance of Human Aquaporin 5 Is Dynamically Regulated by Multiple Pathways.
abstract: Aquaporin membrane protein channels mediate cellular water flow. Human aquaporin 5 (AQP5) is highly expressed in the respiratory system and secretory glands where it facilitates the osmotically-driven generation of pulmonary secretions, saliva, sweat and tears. Dysfunctional trafficking of AQP5 has been implicated in several human disease states, including Sjögren's syndrome, bronchitis and cystic fibrosis. In order to investigate how the plasma membrane expression levels of AQP5 are regulated, we studied real-time translocation of GFP-tagged AQP5 in HEK293 cells. We show that AQP5 plasma membrane abundance in transfected HEK293 cells is rapidly and reversibly regulated by at least three independent mechanisms involving phosphorylation at Ser156, protein kinase A activity and extracellular tonicity. The crystal structure of a Ser156 phosphomimetic mutant indicates that its involvement in regulating AQP5 membrane abundance is not mediated by a conformational change of the carboxy-terminus. We suggest that together these pathways regulate cellular water flow.
authors.affiliation: Molecular Organization and Assembly in Cells Doctoral Training Centre, University of Warwick, Coventry, United Kingdom.
authors.forename: Philip
authors.initials: P
authors.lastname: Kitchen
authors.affiliation: Department of Chemistry, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Öberg
authors.affiliation: Department of Chemistry, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Jennie
authors.initials: J
authors.lastname: Sjöhamn
authors.affiliation: Department of Chemistry, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Hedfalk
authors.affiliation: School of Life and Health Sciences, Aston University, Birmingham, United Kingdom.
authors.forename: Roslyn M
authors.initials: RM
authors.lastname: Bill
authors.affiliation: Clinical and Experimental Medicine, The Medical School, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Alex C
authors.initials: AC
authors.lastname: Conner
authors.affiliation: Biomedical Research Centre, Sheffield Hallam University, Sheffield, United Kingdom.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Conner
authors.affiliation: Department of Biochemistry and Structural Biology, Centre for Molecular Protein Science, Lund University, Lund, Sweden.
authors.forename: Susanna
authors.initials: S
authors.lastname: Törnroth-Horsefield
mesh_terms: D051402:Aquaporin 5 / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D018360:Crystallography, X-Ray; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017433:Protein Structure, Secondary; D021381:Protein Transport / Q000187:drug effects; D012694:Serine / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D051402:Aquaporin 5; D007038:Hypotonic Solutions; D050505:Mutant Proteins; D047428:Protein Kinase Inhibitors; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases