Hypothermia increases aquaporin 4 (AQP4) plasma membrane abundance in human primary cortical astrocytes via a calcium/ transient receptor potential vanilloid 4 (TRPV4)- and calmodulin-mediated mechanism

Research output: Contribution to journalArticlepeer-review

Authors

  • Mootaz M Salman
  • M Nicola Woodroofe
  • James E Brown
  • Roslyn M Bill
  • Alex C Conner
  • Matthew T Conner

Colleges, School and Institutes

External organisations

  • Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, S1 1WB, UK.
  • Institute of Cancer and Genomic Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom.
  • Aston University
  • Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; Celentyx Ltd, Birmingham Research Park, Edgbaston, Birmingham B15 2SQ, UK.
  • Research Institute of Health Sciences, Wolverhampton School of Sciences, University of Wolverhampton, Wulfruna St, Wolverhampton, WV1 1LY.

Abstract

Human aquaporin 4 (AQP4) is the primary water channel protein in brain astrocytes. Hypothermia is known to cause astrocyte swelling in culture, but the precise role of AQP4 in this process is unknown. Primary human cortical astrocytes were cultured under hypothermic (32°C) or normothermic (37°C) conditions. AQP4 transcript, total protein and surface localized protein were quantified using RT-qPCR, sandwich ELISA with whole cell lysates, or cell-surface biotinylation followed by ELISA analysis of the surface-localized protein, respectively. Four-hour mild hypothermic treatment increased the surface localization of AQP4 in human astrocytes to 155 ± 4% of normothermic controls, despite no change in total protein expression levels. The hypothermia-mediated increase in AQP4 surface abundance on human astrocytes was blocked using either calmodulin antagonist (trifluoperazine; TFP); TRPV4 antagonist, HC-067047 or calcium chelation using EGTA-AM. The TRPV4 agonist (GSK1016790A) mimicked the effect of hypothermia compared with untreated normothermic astrocytes. Hypothermia led to an increase in surface localization of AQP4 in human astrocytes through a mechanism likely dependent on the TRPV4 calcium channel and calmodulin activation. Understanding the effects of hypothermia on astrocytic AQP4 cell-surface expression may help develop new treatments for brain swelling based on an in-depth mechanistic understanding of AQP4 translocation. This article is protected by copyright. All rights reserved.

Details

Original languageEnglish
JournalEuropean Journal of Neuroscience
Publication statusPublished - 19 Sep 2017