Abstract
Theta-defensins (θ-defensins) are macrocyclic peptides expressed exclusively in granulocytes and selected epithelia of Old World monkeys. They contribute to anti-pathogen host defense responses by directly killing a diverse range of microbes. Of note, θ-defensins also modulate microbe-induced inflammation by affecting the production of soluble tumor necrosis factor (sTNF) and other proinflammatory cytokines. Here, we report that natural rhesus macaque θ-defensin (RTD) isoforms regulate sTNF cellular release by inhibiting TNF-α-converting enzyme (TACE; also known as adisintegrin and metalloprotease 17; ADAM17), the primary pro-TNF sheddase. Dose-dependent inhibition of cellular TACE activity by RTDs occurred when leukocytes were stimulated with live Escherichia coli cells as well as numerous Toll-like receptor agonists. Moreover, the relative inhibitory potencies of the RTD isoforms strongly correlated with their suppression of TNF release by stimulated blood leukocytes and THP-1 monocytes. RTD isoforms also inhibited ADAM10, a sheddase closely related to TACE. TACE inhibition was abrogated by introducing a single opening in the RTD-1 backbone, demonstrating that the intact macrocycle is required for enzyme inhibition. Enzymologic analyses showed that RTD-1 is a fast binding, reversible, non-competitive inhibitor of TACE. We conclude that θ-defensin-mediated inhibition of pro-TNF proteolysis by TACE represents a rapid mechanism for the regulation of sTNF and TNF-dependent inflammatory pathways. Molecules with structural and functional features mimicking those of θ-defensins may have clinical utility as TACE inhibitors for managing TNF-driven diseases.
Keywords:
ADAM; ADAM17; TACE; cytokine; defensin; enzyme inhibitor; inflammation; proteolytic enzyme; sheddase inhibitors; shedding; theta defensin; tumor necrosis factor (TNF).
© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.
Publication types
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Comparative Study
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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ADAM10 Protein / antagonists & inhibitors
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ADAM10 Protein / genetics
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ADAM10 Protein / metabolism
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ADAM17 Protein / antagonists & inhibitors*
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ADAM17 Protein / genetics
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ADAM17 Protein / metabolism
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Amyloid Precursor Protein Secretases / antagonists & inhibitors
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Amyloid Precursor Protein Secretases / genetics
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Amyloid Precursor Protein Secretases / metabolism
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Animals
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Anti-Inflammatory Agents, Non-Steroidal / chemistry
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Anti-Inflammatory Agents, Non-Steroidal / pharmacology*
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Cell Line
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Chlorocebus aethiops
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Colon / drug effects
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Colon / immunology
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Colon / metabolism
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Defensins / chemistry
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Defensins / pharmacology*
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Escherichia coli / immunology
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Escherichia coli / physiology
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Humans
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Intestinal Mucosa / drug effects
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Intestinal Mucosa / immunology
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Intestinal Mucosa / metabolism
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Leukocytes / drug effects*
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Leukocytes / immunology
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Leukocytes / metabolism
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Lipopolysaccharides / toxicity
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Macaca mulatta
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Membrane Proteins / antagonists & inhibitors
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Monocytes / drug effects*
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Monocytes / immunology
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Monocytes / metabolism
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Protein Conformation
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Protein Isoforms / chemistry
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Protein Isoforms / pharmacology
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Proteolysis / drug effects
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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Solubility
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Toll-Like Receptors / agonists
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Toll-Like Receptors / metabolism
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Tumor Necrosis Factor-alpha / antagonists & inhibitors*
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Tumor Necrosis Factor-alpha / chemistry
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Tumor Necrosis Factor-alpha / metabolism
Substances
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Anti-Inflammatory Agents, Non-Steroidal
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Defensins
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Lipopolysaccharides
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Membrane Proteins
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Protein Isoforms
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Recombinant Proteins
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TNF protein, human
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Toll-Like Receptors
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Tumor Necrosis Factor-alpha
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theta-defensin
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Amyloid Precursor Protein Secretases
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ADAM10 Protein
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ADAM10 protein, human
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ADAM17 Protein
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ADAM17 protein, human