Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, Japan.
FEBS J. 2010 Dec;277(23):4888-900. doi: 10.1111/j.1742-4658.2010.07894.x. Epub 2010 Oct 26.
Type II transmembrane serine proteases (TTSPs) are structurally defined by the presence of a transmembrane domain located near the N-terminus and a C-terminal extracellular serine protease domain. The human TTSP family consists of 17 members. Some members of the family have pivotal functions in development and homeostasis, and are involved in tumorigenesis and viral infections. The activities of TTSPs are regulated by endogenous protease inhibitors. However, protease inhibitors of most TTSPs have not yet been identified. In this study, we investigated the inhibitory effect of hepatocyte growth factor activator inhibitor type 1 (HAI-1), a Kunitz-type serine protease inhibitor, on several members of the TTSP family. We found that the protease activity of a member, TMPRSS13, was inhibited by HAI-1. A detailed analysis revealed that a soluble form of HAI-1 with one Kunitz domain (NK1) more strongly inhibited TMPRSS13 than another soluble form of HAI-1 with two Kunitz domains (NK1LK2). In addition, an in vitro protein binding assay showed that NK1 formed complexes with TMPRSS13, but NK1LK2 did not. TMPRSS13 converted single-chain pro-hepatocyte growth factor (pro-HGF) to a two-chain form in vitro, and the pro-HGF converting activity of TMPRSS13 was inhibited by NK1. The two-chain form of HGF exhibited biological activity, assessed by phosphorylation of the HGF receptor (c-Met) and extracellular signal-regulated kinase, and scattered morphology in human hepatocellular carcinoma cell line HepG2. These results suggest that TMPRSS13 functions as an HGF-converting protease, the activity of which may be regulated by HAI-1.
II 型跨膜丝氨酸蛋白酶（TTSPs）的结构定义为靠近 N 端的跨膜结构域和 C 端细胞外丝氨酸蛋白酶结构域的存在。人类 TTSP 家族由 17 个成员组成。该家族的一些成员在发育和体内平衡中具有关键功能，并参与肿瘤发生和病毒感染。TTSPs 的活性受内源性蛋白酶抑制剂的调节。然而，大多数 TTSP 的蛋白酶抑制剂尚未被鉴定。在这项研究中，我们研究了肝细胞生长因子激活物抑制剂 1（HAI-1），一种 Kunitz 型丝氨酸蛋白酶抑制剂，对 TTSP 家族几个成员的抑制作用。我们发现，一个成员 TMPRSS13 的蛋白酶活性被 HAI-1 抑制。详细分析表明，具有一个 Kunitz 结构域（NK1）的可溶性 HAI-1 形式比具有两个 Kunitz 结构域（NK1LK2）的另一种可溶性 HAI-1 形式更强烈地抑制 TMPRSS13。此外，体外蛋白结合测定表明，NK1 与 TMPRSS13 形成复合物，但 NK1LK2 没有。TMPRSS13 在体外将单链前肝细胞生长因子（pro-HGF）转化为双链形式，并且 TMPRSS13 的 pro-HGF 转化活性被 NK1 抑制。HGF 的双链形式表现出生物活性，通过 HGF 受体（c-Met）和细胞外信号调节激酶的磷酸化以及人肝癌细胞系 HepG2 中的分散形态来评估。这些结果表明 TMPRSS13 作为 HGF 转化蛋白酶发挥作用，其活性可能受 HAI-1 调节。
