title: Transcriptional Regulation of Human Transforming Growth Factor-α in Astrocytes.
abstract: Transforming growth factor-alpha (TGF-α) is known to play multifunctional roles in the central nervous system (CNS), including the provision of neurotropic properties that protect neurons against various neurotoxic insults. Previously, we reported that TGF-α mediates estrogen-induced enhancement of glutamate transporter GLT-1 function in astrocytes. However, the regulatory mechanism of TGF-α at the transcriptional level remains to be established. Our findings revealed that the human TGF-α promoter contains consensus sites for several transcription factors, such as NF-κB and yin yang 1 (YY1). NF-κB served as a positive regulator of TGF-α promoter activity, corroborated by observations that overexpression of NF-κB p65 increased, while mutation in the NF-κB binding sites in the TGF-α promoter reduced the promoter activity in rat primary astrocytes. Pharmacological inhibition of NF-κB with pyrrolidine dithiocarbamate (PDTC; 50 μM) or quinazoline (QNZ; 10 μM) also abolished TGF-α promoter activity, and NF-κB directly bound to its consensus site in the TGF-α promoter as evidenced by electrophoretic mobility shift assay (EMSA). Dexamethasone (DX) increased TGF-α promoter activity by activation of NF-κB. Treatment of astrocytes with 100 nM of DX for 24 h activated its glucocorticoid receptor and signaling proteins, including MAPK, PI3K/Akt, and PKA, via non-genomic pathways, to enhance TGF-α promoter activity and expression. YY1 served as a critical negative regulator of the TGF-α promoter as overexpression of YY1 decreased, while mutation of YY1 binding site in the promoter increased TGF-α promoter activity. Treatment for 3 h with 250 μM of manganese (Mn), an environmental neurotoxin, decreased astrocytic TGF-α expression by activation of YY1. Taken together, our results suggest that NF-κB is a critical positive regulator, whereas YY1 is a negative regulator of the TGF-α promoter. These findings identify potential molecular targets for neurotherapeutics that may modulate TGF-α regulation and afford neuroprotection.
authors.affiliation: Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, 37208, USA.
authors.forename: Pratap
authors.initials: P
authors.lastname: Karki
authors.affiliation: Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, 37208, USA.
authors.forename: James
authors.initials: J
authors.lastname: Johnson
authors.affiliation: Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, 37208, USA.
authors.forename: Deok-Soo
authors.initials: DS
authors.lastname: Son
authors.affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Aschner
authors.affiliation: Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, 37208, USA. elee@mmc.edu.
authors.forename: Eunsook
authors.initials: E
authors.lastname: Lee
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D001483:Base Sequence; D002478:Cells, Cultured; D006801:Humans; D011799:Quinazolines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D016211:Transforming Growth Factor alpha / Q000502:physiology*
chemical_list: D011799:Quinazolines; C587886:TGFA protein, human; D016211:Transforming Growth Factor alpha
keywords: Dexamethasone; Manganese; NF-κB; Transforming growth factor-alpha; YY1