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Assembly of a perivascular astrocyte protein scaffold at the mammalian blood–brain barrier is dependent on α-syntrophin



α-Syntrophin, a member of the dystrophin-associated protein complex, is required for proper localization of the water channel aquaporin-4 at the blood–brain barrier. Mice lacking α-syntrophin have reduced levels of aquaporin-4 in perivascular astroglial endfeet. Consequently, they exhibit reduced edema and infarct volume in brain trauma models and reduced K+ clearance from the neuropil, leading to increased seizure susceptibility. We have used the α-syntrophin null mice to investigate whether α-syntrophin is required for proper localization of other components of the dystrophin complex at the blood–brain barrier. We find that α-syntrophin is required for the full recruitment of γ2-syntrophin and α-dystrobrevin-2 to glial endfeet in adult cerebellum. In contrast, the localization of β1- and β2-syntrophin and α-dystrobrevin-1 at the blood–brain barrier is not dependent on the presence of α-syntrophin. The localization patterns of α-dystrobrevin-1 and -2 in wild type cerebellum are strikingly different; while α-dystrobrevin-1 is present in glial endfeet throughout the cerebellum, α-dystrobrevin-2 is restricted to glial endfeet in the granular layer alone. Finally, we show that the enrichment of dystrophin in glial endfeet depends on the presence of α-syntrophin. This finding is the first demonstration that dystrophin localization is dependent on syntrophin. Since the localization of γ2-syntrophin, α-dystrobrevin-2, and dystrophin is contingent on α-syntrophin, we conclude that α-syntrophin is a central organizer of the astrocyte dystrophin complex, an important molecular scaffold for localization of aquaporin-4 at the blood–brain barrier. © 2006 Wiley-Liss, Inc.

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