[show abstract][hide abstract] ABSTRACT: IL-17A and IL-17F, produced by the Th17 CD4(+) T cell lineage, have been linked to a variety of inflammatory and autoimmune conditions. We recently reported that activated human CD4(+) T cells produce not only IL-17A and IL-17F homodimers but also an IL-17F/IL-17A heterodimeric cytokine. All three cytokines can induce chemokine secretion from bronchial epithelial cells, albeit with different potencies. In this study, we used small interfering RNA and Abs to IL-17RA and IL-17RC to demonstrate that heterodimeric IL-17F/IL-17A cytokine activity is dependent on the IL-17RA/IL-17RC receptor complex. Interestingly, surface plasmon resonance studies indicate that the three cytokines bind to IL-17RC with comparable affinities, whereas they bind to IL-17RA with different affinities. Thus, we evaluated the effect of the soluble receptors on cytokine activity and we find that soluble receptors exhibit preferential cytokine blockade. IL-17A activity is inhibited by IL-17RA, IL-17F is inhibited by IL-17RC, and a combination of soluble IL-17RA/IL-17RC receptors is required for inhibition of the IL-17F/IL-17A activity. Altogether, these results indicate that human IL-17F/IL-17A cytokine can bind and signal through the same receptor complex as human IL-17F and IL-17A. However, the distinct affinities of the receptor components for IL-17A, IL-17F, and IL-17F/IL-17A heterodimer can be exploited to differentially affect the activity of these cytokines.
The Journal of Immunology 09/2008; 181(4):2799-805. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: IL-17F and IL-17A are members of the IL-17 pro-inflammatory cytokine family. IL-17A has been implicated in the pathogenesis of autoimmune diseases. IL-17F is a disulfide-linked dimer that contains a cysteine-knot motif. We hypothesized that IL-17F and IL-17A could form a heterodimer due to their sequence homology and overlapping pattern of expression. We evaluated the structure of recombinant IL-17F and IL-17A proteins, as well as that of natural IL-17F and IL-17A derived from activated human CD4+ T cells, by enzyme-linked immunosorbent assay, immunoprecipitation followed by Western blotting, and mass spectrometry. We find that both IL-17F and IL-17A can form both homodimeric and heterodimeric proteins when expressed in a recombinant system, and that all forms of the recombinant proteins have in vitro functional activity. Furthermore, we find that in addition to the homodimers of IL-17F and IL-17A, activated human CD4+ T cells also produce the IL-17F/IL-17A heterodimer. These data suggest that the IL-17F/IL-17A heterodimer may contribute to the T cell-mediated immune responses.
Journal of Biological Chemistry 06/2007; 282(18):13447-55. · 4.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Myostatin is a transforming growth factor beta family member that acts as a negative regulator of skeletal muscle growth. Myostatin circulates in the blood of adult mice in a noncovalently held complex with other proteins, including its propeptide, which maintain the C-terminal dimer in a latent, inactive state. This latent form of myostatin can be activated in vitro by treatment with acid; however, the mechanisms by which latent myostatin is activated in vivo are unknown. Here, we show that members of the bone morphogenetic protein-1/tolloid (BMP-1/TLD) family of metalloproteinases can cleave the myostatin propeptide in this complex and can thereby activate latent myostatin. Furthermore, we show that a mutant form of the propeptide resistant to cleavage by BMP-1/TLD proteinases can cause significant increases in muscle mass when injected into adult mice. These findings raise the possibility that members of the BMP-1/TLD family may be involved in activating latent myostatin in vivo and that molecules capable of inhibiting these proteinases may be effective agents for increasing muscle mass for both human therapeutic and agricultural applications.
Proceedings of the National Academy of Sciences 01/2004; 100(26):15842-6. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: A human therapeutic that specifically modulates skeletal muscle growth would potentially provide a benefit for a variety of conditions including sarcopenia, cachexia, and muscular dystrophy. Myostatin, a member of the TGF-beta family of growth factors, is a known negative regulator of muscle mass, as mice lacking the myostatin gene have increased muscle mass. Thus, an inhibitor of myostatin may be useful therapeutically as an anabolic agent for muscle. However, since myostatin is expressed in both developing and adult muscles, it is not clear whether it regulates muscle mass during development or in adults. In order to test the hypothesis that myostatin regulates muscle mass in adults, we generated an inhibitory antibody to myostatin and administered it to adult mice. Here we show that mice treated pharmacologically with an antibody to myostatin have increased skeletal muscle mass and increased grip strength. These data show for the first time that myostatin acts postnatally as a negative regulator of skeletal muscle growth and suggest that myostatin inhibitors could provide a therapeutic benefit in diseases for which muscle mass is limiting.
Biochemical and Biophysical Research Communications 02/2003; 300(4):965-71. · 2.41 Impact Factor