Hepatocyte growth factor activator inhibitor type 1 is a specific cell surface binding protein of hepatocyte growth factor activator (HGFA) and regulates HGFA activity in the pericellular microenvironment
Hepatocyte growth factor activator inhibitor type 1 is a specific cell surface binding protein of hepatocyte growth factor activator (HGFA) and regulates HGFA activity in the pericellular microenvironment
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DOI：
10.1074/jbc.m006412200
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发表时间：
2000-12-22
影响因子：
4.8
通讯作者：
Koono, M
中科院分区：
文献类型：
--
作者：
Kataoka, H;Shimomura, T;Koono, M
肝细胞生长因子激活剂（HGFA）负责损伤组织中肝细胞生长因子前体形式的蛋白水解激活。迄今为止，已经确定了两种HGFA特异性抑制剂，即HGFA抑制剂1型（HAI-1）和2型(HAI-2)/胎盘bikunin （PB）。这两种抑制剂首先作为具有两个Kunitz结构域和一个跨膜结构域的完整膜蛋白合成，随后通过脱落从细胞表面释放。本研究表明，在表达这两种抑制剂的上皮细胞表面，一种活性形式的HGFA与膜状的HAI-1特异性络合，而不是与HAI-2/PB特异性络合。这种结合需要HGFA的酶活性。在中国仓鼠卵巢细胞的工程系统中进一步证实了HGFA与细胞表面HAI-1的选择性结合，只有表达HAI-1的细胞保留了外源HGFA。HGFA与HAI-1的结合是可逆的，在结合过程中没有发生影响酶活性的不可逆修饰。重要的是，通过12-肉芽酸酯- 13-醋酸酯或白细胞间素-1 β处理，HAI-1和HGFA HAI-1复合物可以迅速从细胞表面释放，同时产生58-kDa的HAI-1片段，这些片段对HGFA的抑制作用较弱，并且培养上清中HGFA活性显著恢复。这种受调节的脱落被合成锌金属蛋白酶抑制剂BB3103完全抑制。我们得出结论，HAI-1不仅是活性HGFA的抑制剂，而且是活性HGFA的特异性受体，在细胞表面充当该酶的储存库。后一种特性似乎通过上调HGFA的脱落，在某些细胞条件下，如组织损伤和炎症，确保了细胞周围高浓度的HGFA活性。HAI-1复杂。这些发现揭示了整体膜kunitz型抑制剂在调节细胞周围蛋白酶活性中的新功能。
Hepatocyte growth factor activator (HGFA) is responsible for proteolytic activation of the precursor form of hepatocyte growth factor in injured tissues. To date, two specific inhibitors of HGFA have been identified, namely HGFA inhibitor type 1 (HAI-1) and type 2 (HAI-2)/placental bikunin (PB). Both inhibitors are first synthesized as integral membrane proteins having two Kunitz domains and a transmembrane domain, and are subsequently released from cell surface by shedding. Here we show that an active form of HGFA is specifically complexed with membrane-form HAI-1, but not with HAI-2/PB, on the surface of epithelial cells expressing both inhibitors. This binding required the enzyme activity of HGFA. The selective binding of HGFA to the cell surface HAI-1 was further confirmed in an engineered system using Chinese hamster ovary cells, in which only the cells expressing HAI-1 retained exogenous HGFA. The binding of HGFA to HAI-1 was reversible, and no irreversible modifications affecting the enzyme activity occurred during the binding. Importantly, HAI-1 and the HGFA HAI-1 complex were quickly released from the cell surface by treatment with phorbol 12-myristate 13-acetate or interleukin 1 beta accompanying the generation of 58-kDa fragments of HAI-1, which are less potent against HGFA, as well as significant recovery of HGFA activity in the culture supernatant. This regulated shedding was completely inhibited by BB3103, a synthetic zinc-metalloproteinase inhibitor. We conclude that HAI-1 is not only an inhibitor but also a specific acceptor of active HGFA, acting as a reservoir of this enzyme on the cell surface. The latter property appears to ensure the concentrated pericellular HGFA activity in certain cellular conditions, such as tissue injury and inflammation, via the up-regulated shedding of HGFA.HAI-1 complex. These findings shed light on a novel function of the integral membrane Kunitz-type inhibitor in the regulation of pericellular proteinase activity.