Chiu Yi-Lin, Wu Yi-Ying, Barndt Robert B, Lin Yu-Wen, Sytwo Hou-Ping, Cheng Amy, Yang Kacy, Chan Khee-Siang, Wang Jehng-Kang, Johnson Michael D, Lin Chen-Yong
Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington, DC 20057, USA.
Department of Biochemistry, National Defense Medical Center, Tapei 114, Chinese Taipei.
Genes Dis. 2020 Dec 9;9(4):1049-1061. doi: 10.1016/j.gendis.2020.12.001. eCollection 2022 Jul.
The integral membrane, Kunitz-type serine protease inhibitors HAI-1 and HAI-2, can suppress the proteolytic activity of the type 2 transmembrane serine protease matriptase with high specificity and potency. High levels of extracellular matriptase proteolytic activity have, however, been observed in some neoplastic B-cells with high levels of endogenous HAI-2, indicating that HAI-2 may be an ineffective matriptase inhibitor at the cellular level. The different effectiveness of the HAIs in the control of extracellular matriptase proteolytic activity is examined here. Upon inducing matriptase zymogen activation in the HAI Teton Daudi Burkitt lymphoma cells, which naturally express matriptase with very low levels of HAI-2 and no HAI-1, nascent active matriptase was rapidly inhibited or shed as an enzymatically active enzyme. With increasing HAI-1 expression, cellular matriptase-HAI-1 complex increased, and extracellular active matriptase decreased proportionally. Increasing HAI-2 expression, however, resulted in cellular matriptase-HAI-2 complex levels reaching a plateau, while extracellular active matriptase remained high. In contrast to this differential effect, both HAI-1 and HAI-2, even at very low levels, were shown to promote the expression and cell-surface translocation of endogenous matriptase. The difference in the suppression of extracellular active matriptase by the two closely related serine protease inhibitors could result from the primarily cell surface expression of HAI-1 compared to the mainly intracellular localization of HAI-2. The HAIs, therefore, resemble one another with respect to promoting matriptase expression and surface translocation but differ in their effectiveness in the control of extracellular matriptase enzymatic activity.
整合膜蛋白、Kunitz型丝氨酸蛋白酶抑制剂HAI-1和HAI-2能够高度特异性且高效地抑制2型跨膜丝氨酸蛋白酶matriptase的蛋白水解活性。然而，在一些内源性HAI-2水平较高的肿瘤性B细胞中，已观察到高水平的细胞外matriptase蛋白水解活性，这表明HAI-2在细胞水平上可能是一种无效的matriptase抑制剂。本文研究了HAIs在控制细胞外matriptase蛋白水解活性方面的不同有效性。在HAI Teton Daudi伯基特淋巴瘤细胞中诱导matriptase酶原激活时，这些细胞天然表达极低水平的HAI-2且不表达HAI-1，新生的活性matriptase会迅速被抑制或作为一种具有酶活性的酶脱落。随着HAI-1表达的增加，细胞内matriptase-HAI-1复合物增加，而细胞外活性matriptase成比例下降。然而，增加HAI-2的表达会导致细胞内matriptase-HAI-2复合物水平达到平台期，而细胞外活性matriptase仍保持在较高水平。与这种差异效应相反，HAI-1和HAI-2即使在非常低的水平时，也都能促进内源性matriptase的表达和细胞表面转位。这两种密切相关的丝氨酸蛋白酶抑制剂在抑制细胞外活性matriptase方面的差异可能是由于HAI-1主要在细胞表面表达，而HAI-2主要定位于细胞内。因此，HAIs在促进matriptase表达和表面转位方面彼此相似，但在控制细胞外matriptase酶活性的有效性方面存在差异。
