Fiorentino Maria, Fu Liezhen, Shi Yun-Bo
Section on Molecular Morphogenesis, Laboratory of Gene Regulation and Development, PCRM, NICHD, NIH, Bethesda, MD 20892, USA.
Int J Mol Med. 2009 Mar;23(3):389-97. doi: 10.3892/ijmm_00000143.
The matrix metalloproteinase stromelysin-3 (ST3) has long been implicated to play an important role in cell fate determination during normal and pathological processes. Using the thyroid hormone-dependent Xenopus laevis metamorphosis as a model, we have previously shown that ST3 is required for apoptosis during intestinal remodeling and that laminin receptor (LR) is an in vivo substrate of ST3 during this process. ST3 cleaves LR at two distinct sites that are conserved in mammalian LR. Human ST3 and LR are both associated with tumor development and cancer progression and human LR can also be cleaved by ST3, implicating a role of LR cleavage by ST3 in human cancers. Here, we carried out a series of mutational analyses on the two cleavage sites in LR. Our findings revealed that in addition to primary sequence at the cleavage site (positions P3-P3', with the cleavage occurring between P1-P1'), flanking sequences/conformation also influenced the cleavage of LR by ST3. Furthermore, alanine substitution studies led to a surprising finding that surrounding sequence and/or conformation dictated the site of cleavage in LR by ST3. These results thus have important implications in our understanding of substrate recognition and cleavage by ST3 and argue for the importance of studying ST3 cleavage in the context of full-length substrates. Furthermore, the LR cleavage mutants generated here will also be valuable tools for future studies on the role of LR cleavage by ST3 in vertebrate development and cancer progression.
基质金属蛋白酶基质溶解素-3（ST3）长期以来一直被认为在正常和病理过程中的细胞命运决定中起重要作用。我们之前以甲状腺激素依赖的非洲爪蟾变态为模型，表明ST3是肠道重塑过程中细胞凋亡所必需的，并且层粘连蛋白受体（LR）在此过程中是ST3的体内底物。ST3在哺乳动物LR中保守的两个不同位点切割LR。人ST3和LR都与肿瘤发生和癌症进展相关，并且人LR也可被ST3切割，这表明ST3切割LR在人类癌症中起作用。在此，我们对LR中的两个切割位点进行了一系列突变分析。我们的研究结果表明，除了切割位点的一级序列（P3 - P3'位置，切割发生在P1 - P1'之间）外，侧翼序列/构象也影响ST3对LR的切割。此外，丙氨酸替代研究得出了一个惊人的发现，即周围序列和/或构象决定了ST3在LR中的切割位点。因此，这些结果对我们理解ST3的底物识别和切割具有重要意义，并表明在全长底物的背景下研究ST3切割的重要性。此外，这里产生的LR切割突变体也将成为未来研究ST3切割LR在脊椎动物发育和癌症进展中的作用的有价值工具。
