Gremlin-1 C-terminus regulates function of macrophage migration inhibitory factor (MIF)

Abstract

Background/Aims: The counterbalance of macrophage migration inhibitory factor (MIF) and Gremlin-1 is a useful tool to predict the acuity of coronary artery disease (CAD) and plaque stability. Gremlin-1 is an endogenous antagonist of MIF and therefore influences plaque vulnerability. This study was designed to elucidate the mechanistic basis determining the biophysical binding of Gremlin-1 to MIF. Methods: An in silico model suggested that several charged C-terminal amino acids are crucial in mediating Gremlin-1/MIF-binding. We produced several single amino acid exchange mutants of Gremlin-1 by site-directed mutagenesis. These Gremlin-1 mutants were tested for their ability to reduce MIF effects on monocytes. Results: We observed that the critical element of the Gremlin-1 molecule for regulating MIF-induced chemotactic activity lies at the C-terminal region. A single amino acid exchange of an arginine to an alanine residue is sufficient to abolish the antagonistic effect of Gremlin-1 on MIF. Therefore, the Gremlin-1 mutant R172A failed to reduce MIF-induced monocyte differentiation into macrophages. Conclusion: Gremlin-1 C-terminus is essential for antagonizing MIF effects. Our results could offer a novel strategy utilizing Gremlin-1 to target pro-inflammatory effects of MIF in various diseases.