Wang Hong-Xing, Wang Hong-Mei, Lin Hai-Yan, Yang Qing, Zhang Heng, Tsang Benjamin K, Zhu Cheng
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
J Cell Physiol. 2006 Mar;206(3):616-23. doi: 10.1002/jcp.20508.
The ubiquitin-proteasome pathway (UPP) is involved in the degradation of the extracellular matrix (ECM) and trophoblastic invasion during early pregnancy. Our previous studies demonstrated that inhibition of UPP suppresses expression of matrix metalloproteinase (MMP)-2 and -9. LMP2 is an important proteasome subunit that is critical for proteasome activity. This study investigated the regulatory mechanism of LMP2 on the expression and activities of MMP-2 and MMP-9. Our results showed that transfection of LMP2 siRNA plasmid into the human invasive extravillous trophoblast cell line (HTR8/Svneo) could significantly suppress expression of LMP2 mRNA and protein. The mRNA expression of MMP-2 and MMP-9 and their activities were markedly decreased in the LMP2-inhibited cells. Inhibition of LMP2 could also reduce IkappaBalpha mRNA level, although the expression of phosphorylated IkappaBalpha was increased. In the LMP2-inhibited cells, expression of mRNA encoding NF-kappaB subunits p50 and p65 remained normal, but the p50 protein level was significantly decreased in the cytosolic and nuclear extracts, while p65 protein was markedly reduced only in the nuclear extract. We also demonstrated that blockage of the NF-kappaB pathway by the NF-kappaB translocation inhibitor SN50 markedly reduced the expression of MMP-2 and MMP-9 in HTR8/Svneo cells, a result that is fully consistent with the results from the LMP2-inhibited HTR8/Svneo cells. These data suggest that LMP2 contributes to IkappaBalpha degradation and p50 generation, and that inhibition of LMP2 suppresses expression and activities of MMP-2 and MMP-9 by blocking the transfer of active NF-kappaB heterodimers into the nucleus.
泛素-蛋白酶体途径（UPP）参与早孕期间细胞外基质（ECM）的降解和滋养层细胞侵袭。我们之前的研究表明，抑制UPP可抑制基质金属蛋白酶（MMP）-2和-9的表达。LMP2是一种对蛋白酶体活性至关重要的重要蛋白酶体亚基。本研究探讨了LMP2对MMP-2和MMP-9表达及活性的调控机制。我们的结果表明，将LMP2 siRNA质粒转染到人侵袭性绒毛外滋养层细胞系（HTR8/Svneo）中可显著抑制LMP2 mRNA和蛋白的表达。在LMP2抑制的细胞中，MMP-2和MMP-9的mRNA表达及其活性显著降低。抑制LMP2也可降低IkappaBalpha mRNA水平，尽管磷酸化的IkappaBalpha表达增加。在LMP2抑制的细胞中，编码核因子-κB亚基p50和p65的mRNA表达保持正常，但在细胞质和细胞核提取物中p50蛋白水平显著降低，而p65蛋白仅在细胞核提取物中显著减少。我们还证明，核因子-κB易位抑制剂SN50阻断核因子-κB途径可显著降低HTR8/Svneo细胞中MMP-2和MMP-9的表达，这一结果与LMP2抑制的HTR8/Svneo细胞的结果完全一致。这些数据表明，LMP2有助于IkappaBalpha降解和p50生成，并且抑制LMP2通过阻断活性核因子-κB异二聚体转移到细胞核中来抑制MMP-2和MMP-9的表达及活性。
