Enzymatically inactive macrophage migration inhibitory factor inhibits monocyte chemotaxis and random migration.
Macrophage migration inhibitory factor (MIF) is a cytokine that was first described as an inhibitor of the random migration of monocytes and macrophages and has since been proposed to have a number of immune and catalytic functions. One of the functions assigned to MIF is that of a tautomerase that interconverts the enol and keto forms of phenylpyruvate and (p-hydroxyphenyl)pyruvate and converts D-dopachrome, a stereoisomer of naturally occurring L-dopachrome, to 5,6-dihydroxyindole-2-carboxylic acid. The physiological significance of the MIF enzymatic activity is unclear. The three-dimensional structure of MIF is strikingly similar to that of two microbial enzymes (4-oxalocrotonate tautomerase and 5-carboxymethyl-2-hydroxymuconate isomerase) that otherwise share little sequence identity with MIF. MIF and these two enzymes have an invariant N-terminal proline that serves as a catalytic base. Here we report a new biological function for MIF, as an inhibitor of monocyte chemoattractant protein 1- (MCP-1-) induced chemotaxis of human peripheral blood monocytes. We find that MIF inhibition of chemotaxis does not occur at the level of the CC chemokine receptor for MCP-1, CCR2, since MIF does not alter the binding of (125)I-MCP-1 to monocytes. The role of MIF enzymatic activity in inhibition of monocyte chemotaxis and random migration was studied with two MIF mutants in which the N-terminal proline was replaced with either a serine or a phenylalanine. Both mutants remain capable of inhibiting monocyte chemotaxis and random migration despite significantly reduced or no phenylpyruvate tautomerase activity. These data suggest that this enzymatic activity of MIF does not play a role in its migration inhibiting properties.
Hermanowski-Vosatka
A
A
Departments of Endocrinology and Chemical Biology and of Immunology and Rheumatology, Merck Research Laboratories, 126 East Lincoln Avenue, Rahway, New Jersey 07065, USA. anne_vosatka@merck.com
Mundt
S S
SS
Ayala
J M
JM
Goyal
S
S
Hanlon
W A
WA
Czerwinski
R M
RM
Wright
S D
SD
Whitman
C P
CP
D000818:Animals; D001483:Base Sequence; D002465:Cell Movement / Q000187:drug effects*; D018932:Chemokine CCL2 / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D002942:Circular Dichroism; D017931:DNA Primers; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008263:Macrophage Migration-Inhibitory Factors / Q000494:pharmacology*; D013058:Mass Spectrometry; D051379:Mice; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology
C515334:CCR2 protein, human; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D017931:DNA Primers; D008263:Macrophage Migration-Inhibitory Factors; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine; D011994:Recombinant Proteins