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
AuthorsSalman, Mootaz M.
Woodroofe, M. Nicola
Brown, James E.
Bill, Roslyn M.
Conner, Alex C.
Conner, Matthew T.
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AbstractHuman 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 hypothermiamediated 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.
CitationSalman MM., Kitchen P., Woodroofe MN., Brown JE., Bill RM., Conner AC., Conner MT. (2017) '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', European Journal of Neuroscience, 46(9) pp. 2542-2547. doi: 10.1111/ejn.13723
JournalEuropean Journal of Neuroscience
SponsorsBMRC Sheffield Hallam University, RIHS University of Wolverhampton, School of Life and Health Sciences Aston University and the HCED/Iraq grant number GD-13-3 (M Salman).
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