Glia-synapse interaction through Ca²⁺-permeable AMPA receptors in Bergmann glia

Glial cells express a variety of neurotransmitter receptors. Notably, Bergmann glial cells in the cerebellum have Ca²⁺-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) assembled without the GluR2 subunit. To elucidate the role of these Ca²⁺-permeable AMPARs, we converted them into Ca²⁺-impermeable receptors by adenoviral-mediated delivery of the GluR2 gene. This conversion retracted the glial processes ensheathing synapses on Purkinje cell dendritic spines and retarded the removal of synaptically released glutamate. Furthermore, it caused multiple innervation of Purkinje cells by the climbing fibers. Thus, the glial Ca²⁺-permeable AMPARs are indispensable for proper structural and functional relations between Bergmann glia and glutamatergic synapses.