Kwan Jennifer A, Schulze Costas J, Wang Wenjie, Leon Hernando, Sariahmetoglu Meltem, Sung Miranda, Sawicka Jolanta, Sims David E, Sawicki Grzegorz, Schulz Richard
Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada.
FASEB J. 2004 Apr;18(6):690-2. doi: 10.1096/fj.02-1202fje. Epub 2004 Feb 6.
Matrix metalloproteinases (MMPs) are traditionally known for their role in extracellular matrix remodeling. Increasing evidence reveals several alternative substrates and novel biological roles for these proteases. Recent evidence showed the intracellular localization of MMP-2 within cardiac myocytes, colocalized with troponin I within myofilaments. Here we investigated the presence of MMP-2 in the nucleus of cardiac myocytes using both immunogold electron microscopy and biochemical assays with nuclear extracts. The gelatinase activity found in both human heart and rat liver nuclear extracts was blocked with MMP inhibitors. In addition, the ability of MMP-2 to cleave poly (ADP-ribose) polymerase (PARP) as a substrate was examined as a possible role for MMP-2 in the nucleus. PARP is a nuclear matrix enzyme involved in the repair of DNA strand breaks, which is known to be inactivated by proteolytic cleavage. PARP was susceptible to cleavage by MMP-2 in vitro in a concentration-dependent manner, yielding novel degradation products of ~66 and <45 kDa. The cleavage of PARP by MMP-2 was also blocked by MMP inhibitors. This is the first characterization of MMP-2 within the nucleus and we hereby suggest its possible role in PARP degradation.
基质金属蛋白酶（MMPs）传统上因其在细胞外基质重塑中的作用而闻名。越来越多的证据揭示了这些蛋白酶的几种替代底物和新的生物学作用。最近的证据表明，MMP-2在心肌细胞内的定位在细胞内，与肌丝中的肌钙蛋白I共定位。在这里，我们使用免疫金电子显微镜和核提取物的生化分析方法，研究了心肌细胞核中MMP-2的存在情况。在人心脏和大鼠肝脏核提取物中发现的明胶酶活性被MMP抑制剂阻断。此外，还研究了MMP-2作为底物切割聚（ADP-核糖）聚合酶（PARP）的能力，以此作为MMP-2在细胞核中可能发挥的作用。PARP是一种参与DNA链断裂修复的核基质酶，已知其会因蛋白水解切割而失活。PARP在体外易被MMP-2以浓度依赖的方式切割，产生约66 kDa和<45 kDa的新降解产物。MMP-2对PARP的切割也被MMP抑制剂阻断。这是首次对细胞核内的MMP-2进行表征，我们在此提出其在PARP降解中可能发挥的作用。
