Identification and molecular mechanisms of the rapid tonicity-induced relocalization of the aquaporin 4 channel

Philip Kitchen, Rebecca E. Day, Luke H.J. Taylor, Mootaz M. Salman, Roslyn M. Bill*, Matthew T. Conner, Alex C. Conner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The aquaporin family of integral membrane proteins is comprised of channels that mediate cellular water flow. Aquaporin 4 (AQP4) is highly expressed in the glial cells of the central nervous system and facilitates the osmotically-driven pathological brain swelling associated with stroke and traumatic brain injury. Here we show that AQP4 cell surface expression can be rapidly and reversibly regulated in response to changes of tonicity in primary cortical rat astrocytes and in transfected HEK293 cells. The translocation mechanism involves protein kinase A (PKA) activation, influx of extracellular calcium and activation of calmodulin. We identify five putative PKA phosphorylation sites and use site-directed mutagenesis to show that only phosphorylation at one of these sites, serine- 276, is necessary for the translocation response. We discuss our findings in the context of the identification of new therapeutic approaches to treating brain oedema.
Original languageEnglish
Pages (from-to)16873-16881
Number of pages9
JournalJournal of Biological Chemistry
Issue number27
Early online date26 May 2015
Publication statusPublished - 3 Jul 2015

Bibliographical note

Final version free via Creative Commons CC-BY NC ND license.

Funding: EPSRC Grant EP/F500378/1.


  • aquaporin
  • astrocyte
  • homeostasis
  • protein translocation
  • water channel
  • hypotonicity
  • rapid trafficking
  • regulation


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