Transcriptional regulation of the astrocytic excitatory amino acid transporter 1 (EAAT1) via NF-kB and Yin Yang 1 (YY1) [Gene Regulation]

August 12th, 2015 by Karki, P., Kim, C., Smith, K., Son, D.-S., Aschner, M., Lee, E.

Astrocytic glutamate transporter excitatory amino acid transporter (EAAT)1, also known as glutamate aspartate transporter (GLAST) in rodents, is one of two glial glutamate transporters that are responsible for removing excess glutamate from synaptic clefts to prevent excitotoxic neuronal death. Despite its important role in neurophysiological functions, the molecular mechanisms of EAAT1 regulation at the transcriptional level remain to be established. Here, we report that NF-kB is a main positive transcription factor for EAAT1, supported by 1) EAAT1 contains two consensus sites for NF-kB, 2) mutation of NF-kB binding sites decreased EAAT1 promoter activity, and 3) activation of NF-kB increased, while inhibition of NF-kB decreased EAAT1 promoter activity and mRNA/protein levels. Epidermal growth factor (EGF) increased EAAT1 mRNA/protein levels and glutamate uptake via NF-kB. The transcription factor yin yang 1 (YY1) plays as a critical negative regulator of EAAT1, supported by 1) the EAAT1 promoter contains multiple consensus sites for YY1, 2) overexpression of YY1 decreased EAAT1 promoter activity and mRNA/protein levels, and 3) knockdown of YY1 increased EAAT1 promoter activity and mRNA/protein levels. Manganese (Mn) decreased EAAT1 expression via YY1. Epigenetic modifiers histone deacetylases (HDACs) served as co-repressors of YY1 to further decrease EAAT1 promoter activity, whereas inhibition of HDACs reversed Mn-induced decrease of EAAT1 expression. Taken together, our findings suggest that NF-kB is a critical positive regulator of EAAT1, mediating the stimulatory effects of EGF, while YY1 is a negative regulator of EAAT1 with HDACs as co-repressors, mediating the inhibitory effects of Mn on EAAT1 regulation.