Highly Selective Cleavage of Cytokines and Chemokines by the Human Mast Cell Chymase and Neutrophil Cathepsin G
Highly Selective Cleavage of Cytokines and Chemokines by the Human Mast Cell Chymase and Neutrophil Cathepsin G
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DOI：
10.4049/jimmunol.1601223
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发表时间：
2017-02-15
影响因子：
4.4
通讯作者：
Hellman, Lars
中科院分区：
文献类型：
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作者：
Fu, Zhirong;Thorpe, Michael;Hellman, Lars
人肥大细胞糜酶（HC）和人中性粒细胞组织蛋白酶G（hCG）显示出相对相似的切割特异性：它们都具有胰凝乳蛋白酶活性，但也可以在亮氨酸后有效切割。它们相对广泛的特异性表明，如果以足够高的浓度或足够长的时间存在，它们可以切割几乎任何底物。已经鉴定了这些酶的许多潜在底物，并且最近，这些酶还涉及通过切割许多细胞因子和趋化因子来调节细胞因子活性。为了更好地了解它们对各种潜在体内底物的选择性，我们分析了一组51种活性重组细胞因子和趋化因子的裂解。令人惊讶的是，我们的结果显示HC的高选择性;这些蛋白质中只有4/51被基本上切割。hCG切割了一些额外的蛋白质，尽管这发生在向靶添加几乎等摩尔量的酶之后。与天然蛋白质相比，对肽或其他线性底物的活性的这种广泛差异的解释很可能与酶对折叠蛋白质中潜在切割位点的可及性降低有关。在这篇文章中，我们提出的证据表明，网站上没有暴露的蛋白质的表面不被酶切割。有趣的是，两种酶都容易切割IL-18和IL-33，两种IL-1相关的警报素，以及细胞因子IL-15，这对T细胞和NK细胞的稳态很重要。HC和hCG对alarmins的切割表明其具有调节过度炎症的功能。
Human mast cell chymase (HC) and human neutrophil cathepsin G (hCG) show relatively similar cleavage specificities: they both have chymotryptic activity but can also cleave efficiently after leucine. Their relatively broad specificity suggests that they may cleave almost any substrate if present in high enough concentrations or for a sufficiently long time. A number of potential substrates have been identified for these enzymes and, recently, these enzymes have also been implicated in regulating cytokine activity by cleaving numerous cytokines and chemokines. To obtain a better understanding of their selectivity for various potential in vivo substrates, we analyzed the cleavage of a panel of 51 active recombinant cytokines and chemokines. Surprisingly, our results showed a high selectivity of HC; only 4 of 51 of these proteins were substantially cleaved. hCG cleaved a few additional proteins, although this occurred after adding almost equimolar amounts of enzyme to target. The explanation for this wide difference in activity against peptides or other linear substrates compared with native proteins is most likely related to the reduced accessibility of the enzymes to potential cleavage sites in folded proteins. In this article, we present evidence that sites not exposed on the surface of the protein are not cleaved by the enzyme. Interestingly, both enzymes readily cleaved IL-18 and IL-33, two IL-1-related alarmins, as well as the cytokine IL-15, which is important for T cell and NK cell homeostasis. Cleavage of the alarmins by HC and hCG suggests a function in regulating excessive inflammation.