EAAT4 is a post-synaptic glutamate transporter at Purkinje cell synapses

To study cellular and subcellular localizations of the glutamate transporter EAAT4, antibody was raised against the N-terminal peptide. On immunoblotting the antibody recognized a band in membrane extracts from the cerebellum, but not from the forebrain. Immunohistochemistry revealed that its distribution was restricted to the cerebellar molecular layer, where the immunoreactivity was observed as numerous punctate stainings. Electron microscopy showed the antibody to label dendritic spines of the Purkinje cells. EAAT4 is, therefore, a Purkinje cell-specific, postsynaptic transporter. Together with dense localization of other transporter subtypes in Bergmann astrocytic membranes, Purkinje cell synapses are thus provided with distinct glutamate transporter subtypes at discrete synaptic elements, which would play important roles in regulating excitability of the Purkinje cells and protecting against excitotoxicity.