MIF is a proinflammatory cytokine that has been implicated in the pathogenesis of sepsis, arthritis, and other inflammatory diseases. Antibodies against MIF are effective in experimental models of inflammation, and there is interest in strategies to inhibit its deleterious cytokine activities. Here we identify a mechanism of inhibiting MIF pro-inflammatory activities by targeting MIF tautomerase activity. We designed small molecules to inhibit this tautomerase activity; a lead molecule, “ISO-1 ((S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester),” significantly inhibits the cytokine activity in vitro. Moreover, ISO-1 inhibits tumor necrosis factor release from macrophages isolated from LPStreated wild type mice but has no effect on cytokine release from MIFdeficient macrophages. The therapeutic importance of the MIF inhibition by ISO-1 is demonstrated by the significant protection from sepsis, induced by cecal ligation and puncture in a clinically relevant time frame. These results identify ISO-1 as the first small molecule inhibitor of MIF proinflammatory activities with therapeutic implications and indicate the potential of the MIF active site as a novel target for therapeutic interventions in human sepsis.

ISO-1 Binding to the Tautomerase Active Site of MIF Inhibits Its Pro-inflammatory Activity and Increases Survival

Macrophage migration inhibitory factor (MIF) and its homolog D-dopachrome tautomerase (D-DT) are significant promotors of UVB- but not chemically induced non-melanoma skin cancer

Identifying mitophagy-related genes as prognostic biomarkers and therapeutic targets of gastric carcinoma by integrated analysis of single-cell and bulk-RNA sequencing data.

Macrophage migration inhibitory factor (MIF) and its homologue D-dopachrome tautomerase (D-DT) are ubiquitous, pro-inflammatory cytokines with chemokine-like functions that coordinate a wide spectrum of biological activities like migration. Here, we biotin-tagged intracellular MIF/D-DT in vivo to identify important cytosolic interactors and found a plethora of actin cytoskeleton-associated proteins. While the CD74/CD44 receptor complex is essential for signalling transduction in fibroblasts by extracellular MIF/D-DT, our interactome data rather suggested direct effects. We thus investigated whether MIF/D-DT can modulate cell migration independent of CD74/CD44. To differentiate between receptor- and non-receptor-mediated motility, we treated fibroblasts that are deficient in CD74 and CD44 or that express both proteins with recombinant MIF/D-DT. Interestingly, only MIF could stimulate chemokinesis in the presence or absence of CD74/CD44. The pro-migratory effects of MIF depended on lipid raft/caveolae-mediated but not clathrin-mediated endocytosis, on its tautomerase activity and, likely, on its thiol protein oxidoreductase activity. As MIF treatment restrained actin polymerisation in vitro our findings establish a new intracellular role for MIF/D-DT in driving cell motility by modulating the actin cytoskeleton.

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Tamara Henke

Papers

Extracellular MIF, but not its homologue D-DT, promotes fibroblast motility independent of its receptor CD74/CD44.