MIC-1, a novel macrophage inhibitory cytokine, is a divergent member of the TGF-β superfamily

Abstract

Macrophages play a key role in both normal and pathological processes involving immune and inf lammatory responses, to a large extent through their capacity to secrete a wide range of biologically active molecules. To identify some of these as yet not characterized molecules, we have used a subtraction cloning approach designed to identify genes expressed in association with macrophage activation. One of these genes, designated macrophage inhibitory cytokine 1 (MIC-1), encodes a protein that bears the structural characteristics of a transforming growth factor ␤ (TGF-␤) superfamily cytokine. Although it belongs to this superfamily, it has no strong homology to existing families, indicating that it is a divergent member that may represent the first of a new family within this grouping. Expression of MIC-1 mRNA in monocytoid cells is up-regulated by a variety of stimuli associated with activation, including interleukin 1␤, tumor necrosis factor ␣ (TNF-␣), interleukin 2, and macrophage colony-stimulating factor but not interferon ␥, or lipopolysaccharide (LPS). Its expression is also increased by TGF-␤. Expression of MIC-1 in CHO cells results in the proteolytic cleavage of the propeptide and secretion of a cysteine-rich dimeric protein of M r 25 kDa. Purified recombinant MIC-1 is able to inhibit lipopolysaccharide -induced macrophage TNF-␣ production, suggesting that MIC-1 acts in macrophages as an autocrine regulatory molecule. Its production in response to secreted proinf lammatory cytokines and TGF-␤ may serve to limit the later phases of macrophage activation.

Enhancing the secretion of recombinant proteins by engineering N‐glycosylation sites

“…The pro-form of this protein is a homodimer of a 308 amino acid polypeptide, whereas the mature form is a dimer of the last 112 amino acids. 9 The mature form of MIC1 contains no potential N-glycosylation sites but has been shown to be expressed and secreted in CHO cells by fusion with a secretion signal peptide. 9 When an NXS/T sequon was introduced at the N-terminal of the protein (D201S, 198RNGSH, two amino acid behind an N-terminal six histidine tag), the secretion of the mature MIC1 mutant dimer increased more than about five-fold in HEK293-6E cells.…”

Molecular characterisation of canine nonsteroidal anti-inflammatory drug-activated gene (NAG-1)

“…The protein encoded by NAG-1, which has been isolated by a variety of cloning strategies, is also known as macrophage inhibitory cytokine-1 (MIC-1) (Bootcov et al, 1997), placental transforming growth factor β (PTGFB) (Tan et al, 2000), prostate derived factor (PDF) (Paralkar et al, 1998), growth differentiation factor 15 (GDF15) (Hsiao et al, 2000) and placental bone morphogenetic protein (PLAB) (Hromas et al, 1997). The diversity of biological functions indicated by this nomenclature suggests that the biological role of the NAG-1 protein depends on cell context.…”

Growth Differentiation Factor 15, a Marker of Lung Involvement in Systemic Sclerosis, Is Involved in Fibrosis Development but Is not Indispensable for Fibrosis Development

“…GDF-15, or macrophage inhibitory cytokine 1, was originally identified as a factor secreted by activated macrophages (5). Sequence analysis has shown that it is a more distant member of the TGF␤ family (6); GDF-15 shares its homology based on the typical TGF␤ cysteine domains, but shares Ͻ30% sequence homology with other family members such as TGF␤1, GDF-5, and bone morphogenetic proteins.…”