GAPDH Binding to TNF-α mRNA Contributes to Posttranscriptional Repression in Monocytes: A Novel Mechanism of Communication between Inflammation and Metabolism.

Expression of the inflammatory cytokine TNF is tightly controlled. During endotoxin tolerance, transcription of TNF mRNA is repressed, although not entirely eliminated. Production of TNF cytokine, however, is further controlled by posttranscriptional regulation. In this study, we detail a mechanism of posttranscriptional repression of TNF mRNA by GAPDH binding to the TNF 3' untranslated region. Using RNA immunoprecipitation, we demonstrate that GAPDH-TNF mRNA binding increases when THP-1 monocytes are in a low glycolysis state, and that this binding can be reversed by knocking down GAPDH expression or by increasing glycolysis. We show that reducing glycolysis decreases TNF mRNA association with polysomes. We demonstrate that GAPDH-TNF mRNA binding results in posttranscriptional repression of TNF and that the TNF mRNA 3' untranslated region is sufficient for repression. Finally, after exploring this model in THP-1 cells, we demonstrate this mechanism affects TNF expression in primary human monocytes and macrophages. We conclude that GAPDH-TNF mRNA binding regulates expression of TNF based on cellular metabolic state. We think this mechanism has potentially significant implications for treatment of various immunometabolic conditions, including immune paralysis during septic shock.