Mucosal inflammation, through cytokines like interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), has many effects on the intestinal epithelium, including selective translational inhibition of the cytoprotective protein heat shock protein 70 (Hsp70). To further elucidate the mechanisms underlying this effect, we examined the role of stress granules in mediating the actions of these pro-inflammatory cytokines. Using conditionally-immortalized young adult mouse colonic epithelial cells, we demonstrate that IFN-γ and TNF-α, which up-regulate eukaryotic initiation factor-α (eIF-2α) phosphorylation and reduce Hsp70 translation, significantly enhance stress granule formation in heat-shocked intestinal epithelial cells. The IFN-γ and TNF-α effects in up-regulation of stress granule formation and down-regulation of Hsp70 were eIF-2α dependent and the effect could be negated by blocking eIF-2α phosphorylation using PKR-Inhibitor. Correspondingly, IFN-γ and TNF-α increased binding of cytoplasmic proteins to the 3'UTR region of Hsp70 mRNA, thus suggesting specific recruitment of Hsp70 to stress granules as the mechanism of IFN-γ and TNF-α inhibition of Hsp70 translation. We thus report a novel linkage between inflammatory cytokine production, stress granule formation and Hsp70 translation inhibition, providing additional insights into the response of intestinal epithelial cells to inflammatory stress.
- Inflammatory bowel disease
- Stress granules
- Copyright © 2009, American Journal of Physiology- Gastrointestinal and Liver Physiology