AMPA receptors modulate the reorganization of F‐actin in Bergmann glia cells through the activation of RhoA

Alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid glutamate receptors have been shown to modulate the morphology of the lamelar processes of Bergmann glia cells in the molecular layer of the cerebellum. Here we suggest that reorganization of F‐actin may underlay the changes in the morphology of the lamelar processes. Using the fluorescent staining of F‐actin with Phalloidin and the quantification of RhoA activation through immunoprecipitation or pull‐down assays, we show that RhoA is activated after stimulation of alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid receptors and leads to the reorganization of the actin cytoskeleton of Bergmann fibers. This reorganization of the actin cytoskeleton is reflected in the form of an increase in the intensity of the F‐actin staining as well as in the loss of the number of Bergmann fibers stained with Phalloidin. Moreover, using a pharmacological approach, we show that activation of RhoA and the change in the intensity of the F‐actin staining depends on the activation of PI3‐K, focal adhesion kinase, and protein kinase C, whereas changes in the number of Bergmann fibers depend on external calcium in a RhoA independent manner. Our findings show that glutamate may induce a form of structural plasticity in Bergmann glia cells through the reorganization of the actin cytoskeleton. This may have implications in the way the synaptic transmission is processed in the cerebellum. Stimulation of Bergmann glia AMPA receptors induces changes in the fluorescent staining of F‐acting which represents the reorganization of the actin cytoskeleton. The reorganization of the F‐actin cytoskeleton requires the activation of RhoA and the influx of external calcium. Our results lead us to propose that upon AMPA receptors stimulation two separate pathways are initiated, on one side, RhoA is activated on a signal pathway involving FAK, PI3‐K, and PKC, and on the other, calcium influx through AMPA receptors modulate focal adhesions. Our findings suggest that both pathways converge on the modulation of the F‐actin cytoskeleton to allow Bergmann glia cells to undergo a form of structural plasticity in response to glutamatergic neurotransmission.