Sustained Downregulation of {beta}-Dystroglycan and Associated Dysfunctions of Astrocytic Endfeet in Epileptic Cerebral Cortex [Molecular Bases of Disease]

September 16th, 2014 by Gondo, A., Shinotsuka, T., Morita, A., Abe, Y., Yasui, M., Nuriya, M.

Epilepsy is characterized by the abnormal activation of neurons in the cerebral cortex, but the molecular and cellular mechanisms contributing to the development of recurrent seizures are largely unknown. Recently, the critical involvement of astrocytes in the pathophysiology of epilepsy has been proposed. However, the nature of plastic modulations of astrocytic proteins in the epileptic cortex remains poorly understood. In this study, we utilized the zero magnesium in vitro model of epilepsy and examined the potential molecular changes of cortical astrocytes, focusing specifically on endfeet where specialized biochemical compartments exist. We find that the continuous epileptic activation of neurons for 1 hour decreases the expression level of β-dystroglycan (βDG) in acute cortical brain slices prepared from mice. This change is completely abolished by the pharmacological blockade of NMDA-type glutamate receptors as well as by matrix metalloproteinase (MMP) inhibitors. Consistent with the highly specialized localization of βDG at astrocytic endfeet, where it plays a pivotal role in anchoring endfeet-enriched proteins in astrocytes, the downregulation of βDG is accompanied by a decrease in the expression of AQP4, but not laminin. Importantly, this downregulation of βDG persists for at least 1 hour, even after the apparent recovery of neuronal activation. Finally, we show that the downregulation of βDG is associated with the dysfunction of the endfeet at the blood-brain interface as a diffusion barrier. These results suggest that the sustained downregulation of βDG leads to dysfunctions of astrocytic endfeet in the epileptic cerebral cortex and may contribute to the pathogenesis of epilepsy.
  • Posted in Journal of Biological Chemistry, Publications
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