Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California 90089.
Hospital for Special Surgery, Weill Cornell Medicine, New York, New York 10021; Inflammation Program and Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242.
J Biol Chem. 2018 Feb 23;293(8):2725-2734. doi: 10.1074/jbc.RA117.000793. Epub 2018 Jan 9.
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 isintegrin nd etalloprotease 17; ADAM17), the primary pro-TNF sheddase. Dose-dependent inhibition of cellular TACE activity by RTDs occurred when leukocytes were stimulated with live 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.
θ-防御素（θ-defensins）是仅在粒细胞和旧世界猴的某些上皮细胞中表达的大环肽。它们通过直接杀死多种微生物，有助于宿主防御反应抵御病原体。值得注意的是，θ-防御素还通过影响可溶性肿瘤坏死因子（sTNF）和其他促炎细胞因子的产生来调节微生物诱导的炎症。在这里，我们报告天然恒河猴θ-防御素（RTD）同工型通过抑制 TNF-α 转化酶（TACE；也称为整合素和金属蛋白酶 17；ADAM17），即主要的 pro-TNF 脱落酶，调节 sTNF 细胞释放。当白细胞受到活细胞以及许多 Toll 样受体激动剂刺激时，RTD 对细胞 TACE 活性的剂量依赖性抑制作用发生。RTD 同工型的相对抑制效力与其抑制刺激血液白细胞和 THP-1 单核细胞释放 TNF 强烈相关。RTD 同工型还抑制 ADAM10，一种与 TACE 密切相关的脱落酶。在 RTD-1 骨干中引入单个开口会消除 TACE 抑制作用，表明完整的大环是酶抑制所必需的。酶学分析表明，RTD-1 是 TACE 的快速结合、可逆、非竞争性抑制剂。我们得出结论，θ-防御素通过 TACE 抑制 pro-TNF 蛋白水解代表了调节 sTNF 和 TNF 依赖性炎症途径的快速机制。具有模仿 θ-防御素结构和功能特征的分子可能具有作为 TACE 抑制剂的临床用途，用于治疗 TNF 驱动的疾病。
