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

Abstract

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 post-transcriptional regulation. In this study, we detail a mechanism of post-transcriptional repression of TNF mRNA by GAPDH binding to the TNF 3’UTR. 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 post-transcriptional repression of TNF and that the TNF mRNA 3’UTR 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 believe this mechanism has potentially significant implications for treatment of various immunometabolic conditions, including immune paralysis during septic shock.

Targeting immunometabolism as an anti-inflammatory strategy

“…[161][162][163] Another key role of GAPDH involves binding to AU-rich elements in TNFα as well as IFNγ mRNA transcripts. 164,165 In the case of TNF, GAPDH binds to the 3′ untranslated region of TNF mRNA, leading to post-transcriptional repression in galactose-fed monocytes with limited availability of glucose and hence reduced rate of glycolysis. This repression of TNF translation can be reversed by increasing glycolysis at which time GAPDH binding to mRNA is lowered, thereby providing a means of fine-tuning the inflammatory response.…”

Metabolic regulation of macrophage phenotype and function

“…Similarly, Jiang and colleagues (2016) reported that the rate‐limiting glycolytic enzyme, 6‐phosphofructo‐2‐kinase/fructose‐2,6‐biphosphates 3 (PFKFB3) promotes the anti‐viral response of macrophages . Another crucial glycolytic enzyme, glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) has been shown to post‐transcriptionally regulate TNFα expression in human monocytes and macrophages . They demonstrated that a low glycolysis state in THP1 monocytes promotes GAPDH‐TNFα mRNA binding leading to TNFα repression and conversely, during high glycolysis there is little GAPDH‐TNFα mRNA binding, leaving most of the TNFα mRNA to be translated .…”

“…31 They demonstrated that a low glycolysis state in THP1 monocytes promotes GAPDH-TNFα mRNA binding leading to TNFα repression and conversely, during high glycolysis there is little GAPDH-TNFα mRNA binding, leaving most of the TNFα mRNA to be translated. 31 Stimulation of macrophages with TLR agonist also regulates the pentose phosphate pathway (PPP) by repressing its inhibitor, carbohydrate kinaselike protein (CARKL). 32 The PPP is a branch of the glycolytic pathway that results in the generation of NADPH and ribose-5-phosphate, required for nucleotide biosynthesis.…”

A novel moonlight function of glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) for immunomodulation

“…The involvement of glycolysis on TNF‐α secretion by human LPS‐stimulated monocytes has been reported . In addition, Millet P et al recently demonstrated the specific binding of GAPDH on TNF‐α mRNA in THP‐1 monocytes, resulting in the posttranscriptional repression of TNF‐α mRNA . Interestingly, GAPDH and NADH significantly enhanced the production of IL‐10, which corresponded to the suppression of TNF‐α production (Figs.…”