title: A general anaesthetic propofol inhibits aquaporin-4 in the presence of Zn²⁺.
abstract: AQP4 (aquaporin-4), a water channel protein that is predominantly expressed in astrocyte end-feet, plays an important role in the brain oedema formation, and is thereby considered to be a potential therapeutic target. Using a stopped-flow analysis, we showed that propofol (2,6-diisopropylphenol), a general anaesthetic drug, profoundly inhibited the osmotic water permeability of AQP4 proteoliposomes in the presence of Zn²⁺. This propofol inhibition was not observed in AQP1, suggesting the specificity for AQP4. In addition, the inhibitory effects of propofol could be reversed by the removal of Zn²⁺. Other lipid membrane fluidizers also similarly inhibited AQP4, suggesting that the modulation of protein-lipid interactions plays an essential role in the propofol-induced inhibition of AQP4. Accordingly, we used Blue native PAGE and showed that the profound inhibition caused by propofol in the presence of Zn²⁺ is coupled with the reversible clustering of AQP4 tetramers. Site-directed mutagenesis identified that Cys²⁵³, located at the membrane interface connecting to the C-terminal tail, is responsible for Zn²⁺-mediated propofol inhibition. Overall, we discovered that propofol specifically and reversibly inhibits AQP4 through the interaction between Zn²⁺ and Cys²⁵³. The findings provide new insight into the functional regulation of AQP4 and may facilitate the identification of novel AQP4-specific inhibitors.
authors.affiliation: Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: Jungo
authors.initials: J
authors.lastname: Kato
authors.forename: Mariko Kato
authors.initials: MK
authors.lastname: Hayashi
authors.forename: Shinnosuke
authors.initials: S
authors.lastname: Aizu
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Yukutake
authors.forename: Junzo
authors.initials: J
authors.lastname: Takeda
authors.forename: Masato
authors.initials: M
authors.lastname: Yasui
mesh_terms: D019943:Amino Acid Substitution; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D051398:Aquaporin 1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051401:Aquaporin 4 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism*; D008081:Liposomes; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D063347:Native Polyacrylamide Gel Electrophoresis; D009994:Osmolar Concentration; D010539:Permeability / Q000187:drug effects; D015742:Propofol / Q000494:pharmacology*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D014867:Water / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: C496020:AQP1 protein, human; C496030:AQP4 protein, human; D018686:Anesthetics, Intravenous; D051401:Aquaporin 4; D008051:Lipid Bilayers; D008081:Liposomes; D050505:Mutant Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D014867:Water; D051398:Aquaporin 1; D015032:Zinc; D003545:Cysteine; D015742:Propofol