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Structural and functional characterization of a novel serine protease responsible for activation of hepatocyte growth factor

负责肝细胞生长因子激活的新型丝氨酸蛋白酶的结构和功能表征

基本信息

批准号：
05454625
负责人：
KITAMURA Naomi
金额：
$ 4.22万
依托单位：
Kansai Medical University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05454625/
关键词：
hepatocyte growth factor proteolytic processing HGF activator liver injury

项目摘要

Hepatocyte growth factor (HGF) is a potent mitogen for heptocytes and may play an important role in regeneration following hepatic injury. HGF is first synthesized as an inactive single chain precursor which is then converted to an active heterodimeric from by endoproteolytic processing. Recently, a novel serine protease responsible for this processing (HGF activator) has been purified from serum. In this study, we analyzed the structure and function of this protease and obtained the following results.1. Molecular cloning sequence analysis of a cDNA for HGF activator revealed that HGF activator purified from serum is derived from the C-terminal region of a precursor of 655 amino acids by proteolytic cleavage and that the precursor consists of multiple domains homologous to those observed in blood coagulation factor XII.2. HGF activator was present in plasma as an inactive zymogen. The zymogen was activated by the cleavage of the bond between Arg^<407> and Ile^<408> by thrombin in the presence of negatively charged substances. Thus, the HGF activator zymogen may be activated during blood coagulation pathway in response to tissue injury.3. HGF remained as an inactive single chain from in the liver, kidney, lung and spleen of normal rat. The production of HGF markedly increased in the liver after hepatotoxin treatment. A significant portion of the increased HGF was converted to the active form, whereas the conversion did not occur in other tissues. Thus, the proteolytic activation system functions in vivo as a mechanism for localizing HGF activities to injured tissues.4. An enzymatic activity that activates single chain HGF was detected in the injured liver but not in the normal liver. This activity was inhibited by an anti-HGF activator antibody. Thus, HGF activator is likely to be the key enzyme regulating the activities of HGF in the injured tissues.

肝细胞生长因子（HGF）是肝细胞的有效有丝分裂原，可能在肝损伤后的再生中发挥重要作用。 HGF 首先被合成为无活性的单链前体，然后通过内切蛋白水解加工转化为活性异二聚体。最近，一种负责此过程的新型丝氨酸蛋白酶（HGF 激活剂）已从血清中纯化出来。本研究对该蛋白酶的结构和功能进行了分析，得到以下结果： 1． HGF激活剂cDNA的分子克隆序列分析表明，从血清中纯化的HGF激活剂是通过蛋白水解裂解衍生自655个氨基酸的前体的C末端区域，并且该前体由与凝血因子XII.2中观察到的同源的多个结构域组成。 HGF 激活剂作为无活性的酶原存在于血浆中。在带负电荷的物质存在下，凝血酶通过裂解Arg^<407>和Ile^<408>之间的键来激活酶原。因此，HGF激活酶原可能在凝血途径中被激活以响应组织损伤。3． HGF 在正常大鼠的肝、肾、肺和脾中保持为无活性的单链。肝毒素治疗后，肝脏中 HGF 的产生显着增加。增加的 HGF 的很大一部分转化为活性形式，而这种转化在其他组织中并未发生。因此，蛋白水解激活系统在体内发挥作用，将HGF 活性定位于受损组织。4．在受损肝脏中检测到激活单链 HGF 的酶活性，但在正常肝脏中未检测到。该活性被抗 HGF 激活剂抗体抑制。因此，HGF激活剂很可能是调节受损组织中HGF活性的关键酶。