Astrocyte elevated gene-1 is a novel modulator of HIV-1-associated neuroinflammation via regulation of nuclear factor-?B signaling and excitatory amino acid transporter-2 repression.

Authors:
Vartak-Sharma N, Gelman BB, Joshi C, Borgamann K, Ghorpade A
In:
Source: J Biol Chem
Publication Date: (2014)
Issue: 289(28): 19599-612
Research Area:
Neurobiology
Gene Expression
Cells used in publication:
Astrocyte (NHA), human
Species: human
Tissue Origin: brain
Platform:
4D-Nucleofector® 96-well Systems
4D-Nucleofector® X-Unit
Experiment
1.6 x10e6 fetal human astrocytes/20µl sample, P3 primary cell 96 well solution, 100nM siAEG-1 or siControl; or Control-GFP plasmid or AEG-1-GFP (0.125µg/10e6 cells); or pTat (0.15µg/10e6 cells) no program mentioned; plated cells in 25cm2 flask in astrocyte media for 48h; -observed 80% transfection efficiency with Con-GFP plasmid
Abstract
Astrocyte elevated gene-1 (AEG-1), a novel human immunodeficiency virus (HIV)-1 and tumor necrosis factor (TNF)-a-inducible oncogene, has generated significant interest in the field of cancer research as a therapeutic target for many metastatic aggressive tumors. However, little is known about its role in astrocyte responses during HIV-1 central nervous system (CNS) infection and whether it contributes toward the development of HIV-associated neurocognitive disorders (HAND). Therefore, in this study, we investigated changes in AEG-1 CNS expression in HIV-1-infected brain tissues and elucidated a potential mechanism of AEG-1-mediated regulation of HAND. Immunoblotting and immunohistochemical analyses of HIV-1 seropositive and HIV-1 encephalitic human brain tissues revealed significantly elevated levels of AEG-1 protein. Immunohistochemical analyses of HIV-1 Tat transgenic mouse brain tissues also showed a marked increase in AEG-1 staining. Similar to in vivo observations, cultured astrocytes expressing HIV-1 Tat also revealed AEG-1 and cytokine up-regulation. Astrocytes treated with HAND-relevant stimuli, TNF-a, interleukin (IL)-1ß, and HIV-1, also significantly induced AEG-1 expression and nuclear translocation via activation of the nuclear factor (NF)-?B pathway. Co-immunoprecipitation studies demonstrated IL-1ß- or TNF-a-induced AEG-1 interaction with NF-?B p65 subunit. AEG-1 knockdown decreased NF-?B activation, nuclear translocation, and transcriptional output in TNF-a-treated astrocytes. Moreover, IL-1ß treatment of AEG-1-overexpressing astrocytes significantly lowered expression of excitatory amino acid transporter 2, increased expression of excitatory amino acid transporter 2 repressor ying yang 1, and reduced glutamate clearance, a major transducer of excitotoxic neuronal damage. Findings from this study identify a novel transcriptional co-factor function of AEG-1 and further implicate AEG-1 in HAND-associated neuroinflammation.