title: Chronic glutamate treatment selectively modulates AMPA RNA editing and ADAR expression and activity in primary cortical neurons.
abstract: Adenosine-to-inosine RNA editing is a post-transcriptional process, catalyzed by ADAR enzymes, with an important role in diversifying the number of proteins derived from a single gene. In neurons, editing of ionotropic AMPA glutamate receptors has been shown to be altered under several experimental conditions, including severe pathologies, thus highlighting the potential significance of its modulation. In this study, we treated rat primary cortical cell cultures with a sub-lethal dose of glutamate (10 μM), focusing on RNA editing and ADAR activity. We found that chronic glutamate treatment down-regulates RNA editing levels at the R/G site of GluA2-4 subunits of AMPA receptors and at the K/E site of CYFIP2. These changes are site-specific since they were not observed either for the GluA2 Q/R site or for other non-glutamatergic sites. Glutamate treatment also down-regulates the protein expression levels of both ADAR1 and ADAR2 enzymes, through a pathway that is Ca(2+)- and calpain-dependent. Given that AMPA receptors containing unedited subunits show a slower recovery rate from desensitization compared to those containing edited forms, the reduced editing at the R/G site may, at least in part, compensate for glutamate over-stimulation, perhaps through the reduced activation of postsynaptic receptors. In summary, our data provide direct evidence of the involvement of ADAR1 and ADAR2 activity as a possible compensatory mechanism for neuronal protection following glutamate over-stimulation.
authors.affiliation: a Biology and Genetic Division; Department of Molecular and Translational Medicine; National Institute of Neuroscience; University of Brescia ; Brescia , Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bonini
authors.forename: Alice
authors.initials: A
authors.lastname: Filippini
authors.forename: Luca
authors.initials: L
authors.lastname: La Via
authors.forename: Chiara
authors.initials: C
authors.lastname: Fiorentini
authors.forename: Fabio
authors.initials: F
authors.lastname: Fumagalli
authors.forename: Marina
authors.initials: M
authors.lastname: Colombi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Barbon
mesh_terms: D000243:Adenosine Deaminase / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D061251:Primary Cell Culture; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000235:genetics* / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D012333:RNA, Messenger; D018091:Receptors, AMPA; D018698:Glutamic Acid; D002154:Calpain; C000602620:ADAR1 protein, rat; C548484:Ada protein, rat; C000602621:Adarb1 protein, rat; D000243:Adenosine Deaminase; D002118:Calcium
keywords: ADAR1; ADAR2; AMPA receptors; R/G site; RNA editing; glutamate treatment