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

Abstract

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 mM) increased L. amazonensis infectivity in an IFN1-a 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-b 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-b expression.-

Leishmania infantum Induces Mild Unfolded Protein Response in Infected Macrophages

“…Recently, the activation of XBP1 splicing arm of the ER stress response has been reported in a murine macrophage cell line infected with L . amazonensis [40]. The confirmation of this finding, although with some differences, in our infection models suggests some common pathogenic mechanism between cutaneous and visceral species.…”

SILAC-based quantitative proteomics reveals pleiotropic, phenotypic modulation in primary murine macrophages infected with the protozoan pathogenLeishmania donovani

“…In our system several of these proteins including disulfide-isomerase forms [Protein disulfide-isomerase A3 (Pdia3/ P27773, r 1 =1.39,r 2 =1.27), A4 (Pdia4/P08003, r 1 =1.35, r 2 =1.27) and A6 (Pdia6/Q922R8, r 1 =1.43 r 2 =1.31)] [93] and Hypoxia up-regulated 1 (Hyou1/Q9JKR6, r 1 = 1.86, r 2 =1.38 [94], displayed higher levels in infected macrophages ( Table 1 ). Likewise, ER stress and induction of the unfolded protein response was previously documented for RAW 264.7 cells infected with L. amazonensis [50]. Overall, these results suggest that L. donovani infection induces ROS production and ER stress [10, 95], with specific proteins involved in this process displaying higher abundance, and likely acting as a defense mechanism against the oxidants’ deleterious effects.…”

“…Moreover, enrichment in cellular components included the cytoplasm (GO-ID: 5737), intracellular membrane bounded organelle (GO-ID: 43231) and endoplasmic reticulum (GO-ID: 5783), with many of the up-regulated endoplasmic reticulum (ER) proteins involved in protein folding and post-translation modification ( Fig. 4C , Table S2 ), revealing a potential impact of L. donovani infection on endoplasmic reticulum stress and the unfolded protein response as previously documented [50].…”

Endoplasmic Reticulum Stress and Unfolded Protein Response in Infection By Intracellular Parasites

“…The role of UPR during Leishmania infection has been investigated in RAW 264.7 macrophages infected with L. amazonensis [ 67 ]. It has been shown that L. amazonensis infection activates the IRE1-XBP1 arm of UPR in host cells in a TLR2-dependent manner, leading to the expression of IFN-β, which has an established role in L. amazonensis pathogenesis [ 81 ].…”

“…Moreover, XBP1s was necessary to sustain the expression of the antioxidant gene HO-1, that inhibited ROS production. The authors concluded that the activation of XBP1 has an important role in infection by increasing IFN-β expression and protecting the parasites from oxidative stress, thereby promoting parasite proliferation [ 67 ].…”