title: Beyond water homeostasis: Diverse functional roles of mammalian aquaporins.
abstract: BACKGROUND
  Aquaporin (AQP) water channels are best known as passive transporters of water that are vital for water homeostasis.
  
  
  METHODS
  AQP knockout studies in whole animals and cultured cells, along with naturally occurring human mutations suggest that the transport of neutral solutes through AQPs has important physiological roles. Emerging biophysical evidence suggests that AQPs may also facilitate gas (CO2) and cation transport. AQPs may be involved in cell signalling for volume regulation and controlling the subcellular localization of other proteins by forming macromolecular complexes. This review examines the evidence for these diverse functions of AQPs as well their physiological relevance.
  
  
  CONCLUSIONS
  As well as being crucial for water homeostasis, AQPs are involved in physiologically important transport of molecules other than water, regulation of surface expression of other membrane proteins, cell adhesion, and signalling in cell volume regulation.
  
  
  CONCLUSIONS
  Elucidating the full range of functional roles of AQPs beyond the passive conduction of water will improve our understanding of mammalian physiology in health and disease. The functional variety of AQPs makes them an exciting drug target and could provide routes to a range of novel therapies.
authors.affiliation: Molecular Organisation and Assembly in Cells Doctoral Training Centre, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: Philip
authors.initials: P
authors.lastname: Kitchen
authors.affiliation: Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Day
authors.affiliation: Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: Mootaz M
authors.initials: MM
authors.lastname: Salman
authors.affiliation: Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Conner
authors.affiliation: School of Life & Health Sciences and Aston Research Centre for Healthy Ageing, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
authors.forename: Roslyn M
authors.initials: RM
authors.lastname: Bill
authors.affiliation: Institute of Clinical Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. Electronic address: a.c.conner@bham.ac.uk.
authors.forename: Alex C
authors.initials: AC
authors.lastname: Conner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020346:Aquaporins / Q000737:chemistry / Q000502:physiology*; D006706:Homeostasis; D008322:Mammals; D008969:Molecular Sequence Data; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D014867:Water
keywords: Aquaporin; Cell volume regulation; Ion transport; Membrane trafficking; Solute transport