The integrated endoplasmic reticulum stress response in Leishmania amazonensis macrophage infection: the role of X-box binding protein 1 transcription factor

Endoplasmic reticulum (ER) stress triggers the integrated ER-stress response (IERSR) that ensures cellular survival of ER stress and represents a primordial form of innate immunity. We investigated the role of IERSR during Leishmania amazonensis infection. Treatment of RAW 264.7 infected macrophages with the ER stress-inducing agent thapsigargin (TG; 1 mu M) increased L. amazonensis infectivity in an IFN1-alpha receptor (IFNAR)-dependent manner. In Western blot assays, we showed that L. amazonensis activates the inositol-requiring enzyme (IRE1)/X-box binding protein (XBP)-1-splicing arms of the IERSR in host cells. In chromatin immunoprecipitation (ChIP) assays, we showed an increased occupancy of enhancer and promoter sequences for the Ifnb gene by XBP1 in infected RAW 264.7 cells. Knocking down XBP1 expression by transducing RAW 264.7 cells with the short hairpin XBP1 lentiviral vector significantly reduced the parasite proliferation associated with impaired translocation of phosphorylated IFN regulatory transcription factor (IRF)-3 to the nucleus and a decrease in IFN1-beta expression. Knocking down XBP1 expression also increased NO concentration, as determined by Griess reaction and reduced the expression of antioxidant genes, such as heme oxygenase (HO)-1, that protect parasites from oxidative stress. We conclude that L. amazonensis activation of XBP1 plays a critical role in infection by protecting the parasites from oxidative stress and increasing IFN1-beta expression.-Dias-Teixeira, K. L., Calegari-Silva, T. C., Dos Santos, G. R. R. M., Vitorino dos Santos, J., Lima, C., Medina, J. M., Aktas, B. H., Lopes, U. G. The integrated endoplasmic reticulum stress response in Leishmania amazonensis macrophage infection: the role of X-box binding protein 1 transcription factor. FASEB J. 30, 1557-1565 (2016). www.fasebj.org