Screen for Chemical Modulators of the Laminin‐induced Clustering of Dystroglycan Reveals Novel Inhibitors of Aquaporin‐4 Polarized Distribution in Astrocytes

Abstract

Aquaporin‐4 (AQP4) is the principal water channel in the brain and is mainly concentrated at perivascular astrocyte endfeet. This distribution of AQP4 is of major importance because it renders the channel capable of regulating water fluxes between the brain and the bloodstream and therefore plays a role in the water homeostasis. Evidence points to a role of the dystrophin‐associated protein (DAP) complex in the localization of AQP4 at astrocyte endfeet, via dystroglycan (DG) interaction with perivascular laminin. Interestingly, lack of AQP4 concentration at these endfeet in the dystrophin null mouse has been associated with a delayed onset of brain edema. It is therefore of particular importance to identify molecules that modulate the perivascular localization of AQP4. Here, we carried out a high‐throughput screen, using a chemical library of 3,594 small molecules, to identify modulators of the laminin‐induced co‐clustering of the DAP complex and AQP4 in primary astrocyte cultures. Of the 6 inhibitory molecules identified, one induced the reduction of the clustering by promoting the metalloproteinase‐mediated shedding of DG. These findings demonstrate the robustness of our in vitro model that provides a powerful tool for high‐throughput screening and allows us to identify and validate new compounds capable of disrupting the laminin‐induced co‐clustering of the DAP complex with AQP4.Grant Funding Source: Canadian Institutes of Health Research (CIHR), Muscular Dystrophy Canada (MDC)