Dystroglycan in the Cerebellum is a Laminin α2-chain Binding Protein at the Glial-Vascular Interface and is Expressed in Purkinje cells

Dystroglycan is a core component of the dystrophin receptor complex in skeletal muscle which links the extracellular matrix to the muscle cytoskeleton. Dystrophin, dystrophin‐related protein (DRP, utrophin) and dystroglycan are present not only in muscles but also in the brain. Dystrophin is expressed in certain neuronal populations while DRP is associated with perivascular astrocytes. To gain insights into the function and molecular interactions of dystroglycan in the brain, we examined the localization of α‐and β‐dystroglycan at the cellular and subcellular levels in the rat cerebellum. In blood vessels, we find a‐dystroglycan associated with the laminin a2‐chain‐rich parenchymal vascular basement membrane and β‐dystroglycan associated with the endfeet of perivascular astrocytes. We also show that a‐dystroglycan purified from the brain binds a2‐chain‐containing laminin‐2. These observations suggest a dystroglycan‐mediated linkage between DRP in perivascular astrocytic endfeet and laminin‐2 in the parenchymal basement membrane similar to that described in skeletal muscle. This linkage of the astrocytic endfeet to the vascular basement membrane is likely to be important for blood vessel formation and stabilization and for maintaining the integrity of the blood‐brain barrier. In addition to blood vessel labelling, we show that β‐dystroglycan in the rat cerebellum is associated with the surface of Purkinje cell bodies, dendrites and dendritic spines. Dystrophin has previously been localized to the inner surface of the plasma membrane of Purkinje cells and is enriched at postsynaptic sites. Thus, the present results also support the hypothesis that dystrophin interacts with dystroglycan in cerebellar Purkinje neurons.