Egr3 stimulation of GABRA4 promoter activity as a mechanism for seizure-induced up-regulation of GABA _A receptor α4 subunit expression

Abstract

Fig. 1. Protein-protein interactions between gp32 and gp59 on fDNA. (A) The fluorescence from individual molecules of fDNA with the proteins bound in the order as indicated at the side of each row. The gp32 protein is labeled with A488 (gp32 D ) and the gp59 protein is labeled with A555 (gp59 A ). The filter sets are described in Experimental Methods: F1 is for A488 emission, F2 for FRET between A488 and A555, and F3 for A555 emission. (B) Ensemble FRET studies of Oregon-green-488-maleimide-labeled gp59 titrated into a solution of 400 nM CPM-labeled gp32 and 100 nM fDNA. The fluorescence spectra of 400 nM CPM-gp32 alone (black line), the endpoint of the titration at 1 M Oregon-green-488-maleimide-gp59 (dark gray line), and several intermediate spectra (light gray lines) are shown. (C) Analysis of the donor quenching and acceptor sensitization plotted against the gp59 concentration determines the stoichiometry among gp32, gp59, and fDNA to be 1:1:1 with a calculated binding constant of Ϸ40 nM.

Neurosteroid regulation of GABAA receptors: Focus on the α4 and δ subunits

“…More recent studies have shown that brain derived neurotrophic factor is the endogenous signal which initiates these events via the tyrosine kinase receptor (Roberts et al, 2006). In addition to GABAR ligands, seizure activity also increases α4 expression, suggesting that altered neuronal excitability states may underlie the expression of the receptor (Roberts et al, 2005). However, multiple start boxes have also been identified on the α4 promoter, suggesting that multiple mechanisms may exist for triggering its expression (Ma et al, 2004).…”

“…Another steroid hormone, 17β-estradiol, increases α4 levels when administered across a 48-hr or 7-day exposure (Pierson et al, 2005;Zhou & Smith, 2007), most likely through a different mechanism. Recent studies have identified the α4 promoter (Ma et al, 2004;Roberts et al, 2005), which is activated by PKC and early growth factor 3 to increase α4 expression. More recent studies have shown that brain derived neurotrophic factor is the endogenous signal which initiates these events via the tyrosine kinase receptor (Roberts et al, 2006).…”

Dihydromyricetin Prevents Fetal Alcohol Exposure-Induced Behavioral and Physiological Deficits: The Roles of GABAA Receptors in Adolescence

“…Protein kinase C c was later shown to be selectively involved in the incorporation of such EtOH-up-regulated a4-GABA A Rs into the plasma membrane [121]. Analogous decreases in a1-and increases in a4-containing GABA A Rs have been observed in DGCs in a rat model of temporal lobe epilepsy [122,123], later shown to involve inducible early growth response factor 3 (Egr3) up-regulation of the Gabra4 minimal promoter [124]. Consistent with the similarity of the GABA A R alterations, the heightened anxiety, depression, and spatial learning deficits in epilepsy models [125][126][127][128] are also observed in rodent FAE models [60, 64,80,129,130].…”

Silencing Hyper-Excitable Neurons as a Treatment for Status Epilepticus and Temporal Lobe Epilepsy.

“…The human and rat GABRA4 promoters have consensus binding sites for early growth response (Egr) transcription factor 3 (Egr3). The expression of Egr3 is also upregulated in the dentate gyrus after seizures (Roberts, Raol et al 2005). Second, the GABRA4 promoter is 542 bp long which is useful to fit in the 2.4 kb packaging size of self-complementary scAAV virus.…”

“…This effect is mediated by activation of GABA A receptors. GABA A receptors are composed of six α subunits, four β subunits, three types of γ subunits and one of each δ, θ, ε and π subunits (Macdonald and Botzolakis 2009).GABRA4 is the human promoter for the α4 subunit (Roberts, Raol et al 2005). The dentate granule cells in the hippocampus show high expression of α4 GABA A subunit receptors (Sun, Sieghart et al 2004).…”