Department of Dermatology, University Hospital Muenster, Von-Esmarch-Straße 58, 48149, Muenster, Germany.
Institute of Zoophysiology, University of Muenster, Schlossplatz 8, 48143, Muenster, Germany.
Br J Dermatol. 2019 Nov;181(5):999-1008. doi: 10.1111/bjd.17820. Epub 2019 Jun 6.
Transglutaminase (TG)1 plays a key role in the formation of the cornified envelope and thus in the maintenance of the epidermal barrier. Patients with Netherton syndrome (LEKTI deficiency) have increased activity of both TG1 and serin proteases.
To determine whether there is a functional biochemical link between TG1 and LEKTI and whether LEKTI domains could possibly serve as substrates for TG1.
We analysed the protein sequence of LEKTI for possible TG1 recognition sites using bioinformatics. Synthetic peptides and recombinant LEKTI domains D6, D7 and D8+9 were examined in vitro and in situ for possible substrate specificity. The recombinant LEKTI domains were studied for inhibitory activity in a kallikrein (KLK)5 activity test.
We identified possible TG1 consensus sequences in LEKTI domains D6, D7 and D8+9, pointing to a novel biological link between these two proteins. Indeed, synthesized short peptides from these consensus sequences were incorporated into the TG1 activity zone of the epidermis. In vitro the entire recombinant domains of LEKTI showed substrate specificity for TG1, which was again confirmed in situ. The inhibitory activity of the recombinant LEKTI domains was confirmed by a KLK5 inhibition test. The strongest inhibition was observed for domains D8+9.
There are specific domains of LEKTI that are recognized and processed by TG1. LEKTI domains D6, D7 and D8+9 contribute to the formation and protection of the cornified envelope. These results impact the development of protein replacement therapy approaches for Netherton syndrome. What's already known about this topic? LEKTI and transglutaminase (TG)1 are key proteins involved in the terminal differentiation of the epidermis. Lack of LEKTI causes Netherton syndrome; TG1 deficiency causes lamellar ichthyosis. The serine protease inhibitor LEKTI is processed into different functional units. Among different target proteases, kallikrein (KLK)5 appears to be a key player in disease pathology. It has been demonstrated that LEKTI domain 6 inhibits KLK5 and KLK7; LEKTI domains 8-11 also inhibit KLK14. What does this study add? The single LEKTI domains 6, 7 and the functional unit of domains 8 and 9 contain recognition motifs for TG1. We show that these domains and unit are crosslinked into the epidermis by TG1. Functional analyses of the recombinant LEKTI domains revealed that LEKTI D8+9 has the strongest inhibitory effect on KLK5. What is the translational message? The novel functional link between LEKTI and TG1 should be taken into account when considering the development of a targeted topical protein therapy for Netherton syndrome. The unit of domains D8+9 may be sufficient for this purpose.
转谷氨酰胺酶（TG）1 在角蛋白包膜的形成中起关键作用，从而维持表皮屏障。 Netherton 综合征（Lekti 缺乏）患者的 TG1 和丝氨酸蛋白酶活性均增加。
确定 TG1 和 Lekti 之间是否存在功能生化联系，以及 Lekti 结构域是否可能作为 TG1 的底物。
我们使用生物信息学分析了 Lekti 的蛋白质序列，以确定可能的 TG1 识别位点。在体外和原位检测合成肽和重组 Lekti 结构域 D6、D7 和 D8+9 可能的底物特异性。研究了重组 Lekti 结构域在 Kallikrein（KLK）5 活性试验中的抑制活性。
我们在 Lekti 的 D6、D7 和 D8+9 结构域中鉴定出可能的 TG1 共有序列，这表明这两种蛋白质之间存在新的生物学联系。事实上，来自这些共有序列的合成短肽被掺入表皮的 TG1 活性区。体外，整个重组 Lekti 结构域对 TG1 表现出底物特异性，这一点在原位再次得到证实。重组 Lekti 结构域的抑制活性通过 KLK5 抑制试验得到证实。观察到最强的抑制作用是在结构域 D8+9。
Lekti 具有被 TG1 识别和加工的特定结构域。Lekti 的 D6、D7 和 D8+9 结构域有助于角蛋白包膜的形成和保护。这些结果影响了 Netherton 综合征的蛋白质替代治疗方法的发展。
关于这个主题已经知道了什么？Lekti 和转谷氨酰胺酶（TG）1 是参与表皮终末分化的关键蛋白。缺乏 Lekti 会导致 Netherton 综合征；TG1 缺乏会导致板层状鱼鳞病。丝氨酸蛋白酶抑制剂 Lekti 被加工成不同的功能单位。在不同的靶蛋白酶中，激肽释放酶（KLK）5 似乎是疾病发病机制中的关键因素。已经证明 Lekti 结构域 6 抑制 KLK5 和 KLK7；Lekti 结构域 8-11 也抑制 KLK14。
这项研究增加了什么？单个 Lekti 结构域 6、7 和结构域 8 和 9 的功能单元包含 TG1 的识别基序。我们表明这些结构域和单元通过 TG1 交联到表皮中。重组 Lekti 结构域的功能分析表明，Lekti D8+9 对 KLK5 具有最强的抑制作用。
这有什么翻译意义？在考虑为 Netherton 综合征开发靶向局部蛋白治疗时，应考虑 Lekti 和 TG1 之间的新功能联系。结构域 D8+9 的单元可能足以达到此目的。
