Jiang J L, Chan H C, Zhou Q, Yu M K, Yao X Y, Lam S Y, Zhu H, Ho L S, Leung K M, Chen Z N
Cell Engineering Research Center, Fourth Military Medical University, 710032, Xi'an, China.
Cell Mol Life Sci. 2004 Aug;61(16):2083-91. doi: 10.1007/s00018-004-4146-4.
HAb18G/CD147 is a heavily glycosylated protein containing two immunoglobulin superfamily domains. Our previous studies have indicated that overexpression of HAb18G/CD147 enhances metastatic potentials in human hepatoma cells by disrupting the regulation of store-operated Ca2+ entry by nitric oxide (NO)/cGMP. In the present study, we investigated the structure-function of HAb18G/CD147 by transfecting truncated HAb18G/CD147 fragments into human 7721 hepatoma cells. The inhibitory effect of HAb18G/CD147 on 8-bromo-cGMP-regulated thapsigargin-induced Ca2+ entry was reversed by the expression of either C or N terminus truncated HAb18G/CD147 in T7721deltaC and T7721deltaN cells, respectively. The potential effect of HAb18G/CD147 on metastatic potentials, both adhesion and invasion capacities, of hepatoma cells was abolished in T7721deltaC cells, but not affected in T7721deltaN cells. Release and activation of matrix metalloproteinases (MMPs), MMP-2 and MMP-9, were found to be enhanced by the expression of HAb18G/CD147, and this effect was abolished by both truncations. Thapsigargin significantly enhanced release and activation of MMPs (MMP-2 and MMP-9) in non-transfected 7721 cells, and this effect was negatively regulated by SNAP. However, no effects of thapsigargin or SNAP were observed in T7721 cells, and expression of HAb18G/CD147 enhanced secretion and activation of MMPs at a stable and high level. Taken together, these results suggest that both ectodomain and intracellular domains of HAb18G/CD147 are required to mediate the effect of HAb18G/CD147 on the secretion and activation of MMPs and metastasis-related processes in human hepatoma cells by disrupting the regulation of NO/cGMP-sensitive intracellular Ca2+ mobilization although each domain may play different roles.
HAb18G/CD147是一种高度糖基化的蛋白质，含有两个免疫球蛋白超家族结构域。我们之前的研究表明，HAb18G/CD147的过表达通过破坏一氧化氮（NO）/环鸟苷酸（cGMP）对储存式Ca2+内流的调节，增强了人肝癌细胞的转移潜能。在本研究中，我们通过将截短的HAb18G/CD147片段转染到人7721肝癌细胞中来研究HAb18G/CD147的结构功能。在T7721deltaC和T7721deltaN细胞中分别表达C端或N端截短的HAb18G/CD147，可逆转HAb18G/CD147对8-溴-cGMP调节的毒胡萝卜素诱导的Ca2+内流的抑制作用。HAb18G/CD147对肝癌细胞转移潜能（包括黏附能力和侵袭能力）的潜在影响在T7721deltaC细胞中被消除，但在T7721deltaN细胞中未受影响。发现基质金属蛋白酶（MMPs）-2和MMP-9的释放和激活因HAb18G/CD147的表达而增强，且这种作用在两种截短情况下均被消除。毒胡萝卜素显著增强了未转染的7721细胞中MMPs（MMP-2和MMP-9）的释放和激活，且这种作用受到硝普钠（SNAP）的负调节。然而，在T7721细胞中未观察到毒胡萝卜素或SNAP的作用，且HAb18G/CD147的表达稳定且高水平地增强了MMPs的分泌和激活。综上所述，这些结果表明，HAb18G/CD147的胞外结构域和胞内结构域均是介导HAb18G/CD147对人肝癌细胞中MMPs的分泌和激活以及转移相关过程的作用所必需的，尽管每个结构域可能发挥不同作用，其作用机制是通过破坏NO/cGMP敏感的细胞内Ca2+动员的调节。
