Astrocyte AEG-1 regulation of Wnt/β-catenin signaling in HAND




Nooka, Shruthi
Ghorpade, Anuja


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Purpose: Glial induced chronic inflammation contributes to the pathogenesis of HIV-1-associated neurocognitive disorder (HAND), but the molecular mechanisms of inflammatory regulation have not yet been fully understood. Astrocyte elevated gene (AEG-1), an HIV-1 and tumor necrosis factor (TNF)-α inducible gene, is associated with multiple signaling cascades such as nuclear factor (NF)-κB, Wnt/β-catenin during tumor progression. Recently, upregulation of Wnt signaling proteins was observed in spinal cord dorsal horn of HIV-1 patients. In addition, Wnt signaling regulates pro-inflammatory cytokines expression in several inflammatory diseases including rheumatoid arthritis, psoriasis. However, the relationship between AEG-1 and Wnt signaling pathway in HIV-1-associated neuropathogenesis has not been studied. Hereby, we proposed that astrocyte AEG-1 induces inflammation via classical Wnt signaling in HAND. Methods: Cultured human astrocytes were treated with HIV-1DJV, interleukin (IL)-1β and TNF-α. Astrocytes were nucleofected with AEG-1 and β-catenin specific siRNA. Changes in AEG-1, β-catenin and lymphoid enhancing factor (LEF)-1 levels were determined by RT-PCR, western blot analysis and immunocytochemistry. Co-immunoprecipitation (Co-IP) studies were performed to examine AEG-1 interacting proteins and NF-κB dynamics. Pro-inflammatory molecules such as CCL2 and CXCL8 levels were measured by ELISA. Results: HIV-1DJV in combination with IL-1β and TNF-α significantly upregulated AEG-1, β-catenin and LEF-1 mRNA levels. Nuclear translocation of β-catenin decreased significantly in siAEG-1 transfected astrocytes. Further, Co-IP studies showed AEG-1 interacting with β-catenin and LEF-1, and upon activation with pro-inflammatory stimuli, interaction increased in both the cytoplasm and nucleus. Both AEG-1 and β-catenin also interacted with NF-κB, suggesting a common denominator in regulating inflammation. AEG-1 and β-catenin transient knockdown followed by IL-1β treatment altered NF-κB mediated pro-inflammatory cytokines production. Conclusion: In summary, HAND-relevant stimuli upregulated classical Wnt signaling and increased interactions between AEG-1, β-catenin and NF-κB, suggesting AEG-1 mediated Wnt signaling regulation of NF-κB activity in HAND neuropathogenesis.


Research Appreciation Day Award Winner - 2015 Robert J. Wordinger Excellence in Virology Research Poster Presentation - 1st Place Award