The D -dopachrome tautomerase ( DDT ) gene product is a cytokine and functional homolog of macrophage migration inhibitory factor (MIF)

Abstract

Macrophage migration inhibitory factor (MIF) is a pivotal regulator of the immune response. Neutralization or genetic deletion of MIF does not completely abrogate activation responses, however, and deletion of the MIF receptor, CD74, produces a more pronounced phenotype than MIF deficiency. We hypothesized that these observations may be explained by a second MIF-like ligand, and we considered a probable candidate to be the protein encoded by the homologous, D-dopachrome tautomerase (D-DT) gene. We show that recombinant D-DT protein binds CD74 with high affinity, leading to activation of ERK1/2 MAP kinase and downstream proinflammatory pathways. Circulating D-DT levels correlate with disease severity in sepsis or malignancy, and the specific immunoneutralization of D-DT protects mice from lethal endotoxemia by reducing the expression of downstream effector cytokines. These data indicate that D-DT is a MIF-like cytokine with an overlapping spectrum of activities that are important for our understanding of MIF-dependent physiology and pathology.inflammation | lipopolysaccharide | septic shock M acrophage migration inhibitory factor (MIF) is the first cytokine activity described and a key regulatory mediator that is released upon activation of different cell types (1-3). MIF increases macrophage antimicrobial responses and it is expressed upstream of cytokines such as tumor necrosis factor (TNF)-α, IFN-γ, and IL-1β (4). MIF activates immune cells by binding to CD74, leading to the recruitment of CD44 into a signaling complex, the stimulation of nonreceptor tyrosine kinases, and initiation of the ERK1/2 MAP kinase pathway (5, 6). The chemokine receptors CXCR2 and CXCR4 also become activated by MIF via noncognate interactions that are reinforced in the presence of CD74 (7). Among mesenchymal cell types, MIF binding to cardiomyocyte CD74 stimulates the AMP-activated kinase (AMPK) cascade to mediate protection from ischemic injury (8, 9).Although MIF receptor knockout mice (CD74) phenocopy features of MIF deficiency (10-12), recent observations have led to the hypothesis that there may be a second ligand for CD74. MIF-deficient B cells, for example, are more sensitive to apoptosis than wild-type B cells, but the magnitude of this defect is twofold more pronounced in CD74-deficient cells (13). Intravital microscopy studies also have shown a more pronounced effect of antagonism of CD74 than MIF in monocyte arrest (7). Finally, anti-MIF antibodies, although highly effective in experimental studies, do not completely inhibit CD74-dependent cellular activation responses (14).We hypothesized that these observations may be explained by a second MIF-like ligand, and we considered a likely candidate to be the protein encoded by the DDT gene, D-dopachrome tautomerase (D-DT). DDT and MIF show a conserved intron-exon structure and their coding regions are highly homologous. The genes for MIF and D-DT are in close apposition to each other and to two theta-class glutathione S-transferases, suggesting that these gene clusters arose by...

APlasmodium-encoded cytokine suppresses T-cell immunity during malaria

“…cDNA for PfMIF and PbMIF were synthesized (GenScript), and PfMIF and PbMIF were expressed and purified following a previously described methodology with <20 pg endotoxin/ mg protein as assessed by the PyroGene Recombinant Factor C assay (Cambrex BioScience) (58). Real-time binding interaction of PfMIF to the soluble ectodomain of CD74 was analyzed using the BIAcore 2000 biosensor (60).…”

“…Briefly, polyclonal antibodies against PfMIF or PbMIF were produced in rabbits (PFR&L), and antibody specificity was verified by both Western blotting and ELISA, as described recently (60). IgG antibody fractions were purified and used to coat microtiter plates (Nunc) at 1 μg/mL anti-PfMIF or anti-PbMIF IgG overnight.…”

Macrophage Migration Inhibitory Factor Potentiates Autoimmune-Mediated Neuroinflammation

“…MIF was among the first cytokines to be discovered, and new insights into its role in inflammatory responses continue to be elucidated (18). Recently, a new member of the MIF superfamily, D-dopachrome tautomerase, a structural homolog dubbed MIF-2, has been described (19). MIF is a multipotent cytokine that exerts a variety of mitogenic and proinflammatory functions (20).…”

Analysis of serum macrophage migration inhibitory factor and D‐dopachrome tautomerase in systemic sclerosis

“…A second member of the MIF superfamily, D‐dopachrome tautomerase (DDT; MIF‐2), has also been identified, with similar physiological and biochemical properties to MIF 11. In particular, DDT is found in most tissues and is present at similar levels to MIF in serum and the two proteins appear to work cooperatively 12. DDT has been associated with pathology in a number of diseases, including multiple sclerosis 4.…”