Glutamate-Dependent Dynamic DNA Methylation Regulates Excitatory Amino Acid Transporters in Bergmann Glia Cells: Role of AMPA Receptors.

Glial glutamate uptake through sodium-dependent excitatory amino acid transporters (EAATs) is essential for synaptic homeostasis. Epigenetic modifications and neurotransmitter receptor signaling influence glial function although their interactive effects on glutamate transporter regulation remain poorly understood. To investigate how DNA methylation affects glutamate receptor-mediated regulation of its own removal, primary cultures from chick cerebellar Bergmann glial cells were used. Confluent monolayers were treated with a DNA methylation inhibitor. Glutamate transporter activity was assessed through radioactive uptake assays, while methylation levels within distinct regions of the chGLAST promoter were analyzed by methylated DNA immunoprecipitation (MeDIP)-PCR. The role of cytoskeletal dynamics and calcium signaling was evaluated using pharmacological modulators. DNA hypomethylation sensitizes glial cells to glutamate receptors stimulation. Kinetic analyses show a statistically significant increase in the Michaelis-Menten constant VMax and a non-significant change in KM, changes in VMax reflect alterations in plasma membrane transporter numberinity. Pharmacological analysis revealed the involvement of the phosphatidyl inositol 3 kinase (PI3K), the Ca2+/calmodulin-dependent kinase II (CaMKII) and the mammalian target of rapamycin (mTOR) pathways, suggesting coordinated regulation of glutamate transport. Importantly, short-term activation of AMPA receptors induced hypomethylation of the chglast promoter, suggesting the engagement of active demethylation pathways that sustain transporter expression during heightened excitatory activity. Together, these findings reveal a novel mechanism in which epigenetic flexibility and synaptic receptor activity converge to enhance glutamate uptake in glial cells. This synergy between DNA methylation and AMPA receptor signaling provide new insights into the mechanisms by which glial cells dynamically adapt to excitatory stress.