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Hypothermia increases aquaporin 4 ( AQP 4) plasma membrane abundance in human primary cortical astrocytes via a calcium/transient receptor potential vanilloid 4 ( TRPV 4)‐ and calmodulin‐mediated mechanism
Author(s) -
Salman Mootaz M.,
Kitchen Philip,
Woodroofe M. Nicola,
Brown James E.,
Bill Roslyn M.,
Conner Alex C.,
Conner Matthew T.
Publication year - 2017
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.13723
Subject(s) - trpv , transient receptor potential channel , chemistry , aquaporin 4 , microbiology and biotechnology , astrocyte , trifluoperazine , calmodulin , agonist , calcium , pharmacology , biochemistry , receptor , endocrinology , biology , trpv1 , central nervous system , organic chemistry
Human aquaporin 4 ( AQP 4) is the primary water channel protein in brain astrocytes. Hypothermia is known to cause astrocyte swelling in culture, but the precise role of AQP 4 in this process is unknown. Primary human cortical astrocytes were cultured under hypothermic (32 °C) or normothermic (37 °C) conditions. AQP 4 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 AQP 4 in human astrocytes to 155 ± 4% of normothermic controls, despite no change in total protein expression levels. The hypothermia‐mediated increase in AQP 4 surface abundance on human astrocytes was blocked using either calmodulin antagonist (trifluoperazine, TFP ); TRPV 4 antagonist, HC ‐067047 or calcium chelation using EGTA ‐ AM . The TRPV 4 agonist ( GSK 1016790A) mimicked the effect of hypothermia compared with untreated normothermic astrocytes. Hypothermia led to an increase in surface localization of AQP 4 in human astrocytes through a mechanism likely dependent on the TRPV 4 calcium channel and calmodulin activation. Understanding the effects of hypothermia on astrocytic AQP 4 cell surface expression may help develop new treatments for brain swelling based on an in‐depth mechanistic understanding of AQP 4 translocation.