title: GABAAergic stimulation modulates intracellular protein arginine methylation.
abstract: Changes in cytoplasmic pH are known to regulate diverse cellular processes and influence neuronal activities. In neurons, the intracellular alkalization is shown to occur after stimulating several channels and receptors. For example, it has previously demonstrated in P19 neurons that a sustained intracellular alkalinization can be mediated by the Na(+)/H(+) antiporter. In addition, the benzodiazepine binding subtypes of the γ-amino butyric acid type A (GABAA) receptor mediate a transient intracellular alkalinization when they are stimulated. Because the activities of many enzymes are sensitive to pH shift, here we investigate the effects of intracellular pH modulation resulted from stimulating GABAA receptor on the protein arginine methyltransferases (PRMT) activities. We show that the major benzodiazepine subtype (2α1, 2β2, 1γ2) is constitutively expressed in both undifferentiated P19 cells and retinoic acid (RA) differentiated P19 neurons. Furthermore stimulation with diazepam and, diazepam plus muscimol produce an intracellular alkalinization that can be detected ex vivo with the fluorescence dye. The alkalinization results in significant perturbation in protein arginine methylation activity as measured in methylation assays with specific protein substrates. Altered protein arginine methylation is also observed when cells are treated with the GABAA agonist muscimol but not an antagonist, bicuculline. These data suggest that pH-dependent and pH-independent methylation pathways can be activated by GABAAergic stimulation, which we verified using hippocampal slice preparations from a mouse model of fragile X syndrome.
authors.affiliation: Department of Molecular Biology, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, New York, NY 10314, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Denman
authors.affiliation: Division of Hematology and Medical Oncology, Department of Medicine, Weill Medical College of Cornell University, New York, NY 1065, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Xie
authors.affiliation: Department of Developmental Neurobiology, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, New York, NY 10314, USA.
authors.forename: George
authors.initials: G
authors.lastname: Merz
authors.affiliation: Department of Basic Sciences, The Commonwealth Medical College, 525 Pine Street, Scranton, PA 18509, USA. Electronic address: ysung@tcmedc.org.
authors.forename: Ying-Ju
authors.initials: YJ
authors.lastname: Sung
mesh_terms: D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001640:Bicuculline / Q000494:pharmacology; D002454:Cell Differentiation; D002460:Cell Line; D003975:Diazepam / Q000494:pharmacology; D004357:Drug Synergism; D058785:GABA-A Receptor Agonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D042541:Intracellular Space / Q000378:metabolism*; D008745:Methylation; D018345:Mice, Knockout; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011484:Protein-Arginine N-Methyltransferases / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism*; D015398:Signal Transduction; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001120:Arginine; D011484:Protein-Arginine N-Methyltransferases; D003975:Diazepam; D001640:Bicuculline
keywords: Fmr1 knockout mice; Fragile X syndrome; GABA(A) receptor; Protein arginine methylation