title: Interleukin 1β Regulation of the System xc- Substrate-specific Subunit, xCT, in Primary Mouse Astrocytes Involves the RNA-binding Protein HuR.
abstract: System xc(-) is a heteromeric amino acid cystine/glutamate antiporter that is constitutively expressed by cells of the CNS, where it functions in the maintenance of intracellular glutathione and extracellular glutamate levels. We recently determined that the cytokine, IL-1β, increases the activity of system xc(-) in CNS astrocytes secondary to an up-regulation of its substrate-specific light chain, xCT, and that this occurs, in part, at the level of transcription. However, an in silico analysis of the murine xCT 3'-UTR identified numerous copies of adenine- and uridine-rich elements, raising the possibility that undefined trans-acting factors governing mRNA stability and translation may also contribute to xCT expression. Here we show that IL-1β increases the level of mRNA encoding xCT in primary cultures of astrocytes isolated from mouse cortex in association with an increase in xCT mRNA half-life. Additionally, IL-1β induces HuR translocation from the nucleus to the cytoplasm. RNA immunoprecipitation analysis reveals that HuR binds directly to the 3'-UTR of xCT in an IL-1β-dependent manner. Knockdown of endogenous HuR protein abrogates the IL-1β-mediated increase in xCT mRNA half-life, whereas overexpression of HuR in unstimulated primary mouse astrocytes doubles the half-life of constitutive xCT mRNA. This latter effect is accompanied by an increase in xCT protein levels, as well as a functional increase in system xc(-) activity. Altogether, these data support a critical role for HuR in mediating the IL-1β-induced stabilization of astrocyte xCT mRNA.
authors.affiliation: From the Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York 13244.
authors.forename: Jingxue
authors.initials: J
authors.lastname: Shi
authors.affiliation: From the Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York 13244.
authors.forename: Yan
authors.initials: Y
authors.lastname: He
authors.affiliation: From the Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York 13244.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Hewett
authors.affiliation: From the Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York 13244. Electronic address: jhewett@syr.edu.
authors.forename: James A
authors.initials: JA
authors.lastname: Hewett
mesh_terms: D020413:3' Untranslated Regions; D027182:Amino Acid Transport System y+ / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D000067780:ELAV-Like Protein 1 / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D018698:Glutamic Acid / Q000378:metabolism; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020413:3' Untranslated Regions; D027182:Amino Acid Transport System y+; D000067780:ELAV-Like Protein 1; C000593997:Elavl1 protein, mouse; D053583:Interleukin-1beta; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C492255:Slc7a11 protein, mouse; D018698:Glutamic Acid
keywords: ELAV-like protein 1 (HuR (human antigen R)); astrocyte; central nervous system (CNS); cystine/glutamate transporter; interleukin 1 (IL-1); mRNA stability; neuroinflammation; post-transcriptional regulation; system xc-