Background: The water channel protein aquaporin 4 (AQP4) controls water permeability of the blood-brain barrier.Results: Hypotonicity induces rapid relocalization of AQP4 in a calcium-, calmodulin-, and kinase-dependent manner.Conclusion: AQP4 can be relocalized between the cell membrane and intracellular compartments.Significance: Pharmacological modulation of AQP4 membrane localization could provide a new approach to treating brain edema.

Background: Aquaporin channels ensure appropriate membrane permeability to water in all cells.Results: Following a hypotonic stimulus, subcellular localization of aquaporin 1 occurs via a mechanism dependent on transient receptor potential channels, extracellular calcium influx, calmodulin, and the phosphorylation of two threonines (157 and 239) of aquaporin 1.Conclusion: Rapid translocation of aquaporin 1 regulates membrane water permeability.Significance: This mechanism may serve as a prototype for the rapid regulation of aquaporin function.

Preorganised urea groups moderate the anion-exchange properties of cationic receptor 2, favouring halide extraction and promoting anion transport through a bulk liquid membrane.

Four out of the five rings of the alkaloid neotuberostemonine (1) are present in the advanced precursor 2. The tetracyclic compound 2 has now been prepared in a short, linear route via lactone acid 3. A key step in the synthesis was the cuprate‐mediated SN2′ ring‐opening desymmetrization of the C2‐symmetric bislactone 4.

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Vier der fünf Ringe des Alkaloids Neotuberostemonin (1) finden sich bereits in der komplexen Vorstufe 2. Der Tetracyclus 2 wurde nun auf einem kurzen und linearen Weg über die Lactonsäure 3 erhalten. Ein Schlüsselschritt der Synthese war die kupfervermittelte SN2′‐Ringöffnungs‐Desymmetrisierung des C2‐symmetrischen Bislactons 4.