Expression of the GluA2 subunit of glutamate receptors is required for the normal dendritic differentiation of cerebellar Purkinje cells.

Cerebellar Purkinje cells differentiate the most elaborate dendritic trees among neurons in the brain and constitute the principal part of cerebellar neuronal circuitry. In the present study, we examined the role of the GluA2 subunit of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors in the dendritic differentiation of Purkinje cells. Since mature Purkinje cells express the GluA2 subunit, AMPA receptors on them exhibit a low Ca permeability. Does this expression of GluA2, leading to the loss of Ca permeability of AMPA receptors, have a positive significance in the dendritic differentiation of Purkinje cells? To answer this question, we introduced GluA2 siRNA into immature Purkinje cells in cerebellar cell cultures using a single-cell electroporation technique. The dendritic elongation and branching, as well as spine formation, were inhibited by GluA2 knockdown in Purkinje cells. GluA2 knockdown augmented the elevation of intracellular Ca concentrations and a higher incidence of oscillation of intracellular Ca concentrations in response to glutamate. These findings suggest that excessive elevation of intracellular Ca concentrations has a negative effect on the dendritic differentiation of Purkinje cells and that the expression of GluA2 inhibits this negative effect in the development of Purkinje cells.