SUMO蛋白轉譯後修飾之基質金屬蛋白酶-7在細胞核中參與核纖層蛋白蛋白質裂解之研究

Abstract

Matrix metalloptroteinase-7 (MMP-7; matrilysin) is a member of the MMPs family, which is involved in the extracellular matrix (ECM) component degradation and tissue remodeling. MMP-7 was reported as a secreted enzyme localized in the epical surface of normal glandular epithelial cells by Western blot and zymography analysis. Interestingly, a 31 kDa protein with protease activity found in nucleus was identified as pro-MMP-7. Furthermore, the protein sequence of MMP-7 was analyzed and a putative sumoylation site was defined by Dr. Wei-Hsuan Yu. (1998 Gordon Research Conferences poster) To determine the sumoylation state of MMP-7, we used two anti-MMP7 antibodies to immunoprecipitate MMP-7, and then analyzed by Western blot with an anti-SUMO3 antibody. These results demonstrated that MMP-7 was modified by SUMO3. The prominent SUMO3 modified MMP-7 in the nucleus fraction implicated that SUMOylation post-translational modification for MMP-7 could be a nucleus trafficking signature for MMP-7. Also, by analyzing the total cell lysate with immunoprecipitation method, we found that MMP-7 were also ubiquitinated. The SUMO3 and ubiquitin tagged on MMP-7 could be responsible for MMP-7 intracellular trafficking route. The detail mechanism remains for further investigation. After the nuclear translocation of MMP-7 was verified, we further found that lamin B1 became fragmented when MMP-7 was overexpressed. Using an anti-lamin B1 antibody, the immunoprecipitation data showed that the active site mutated MMP-7 was pulled down and was detected by Western blotting. Furthermore, the intact structure of lamin B1 at nuclear lamina was changed when MMP-7 was overexpressed. My data suggested that lamin B1 could be a substrate of MMP-7 in the nucleus. As the MMP-7/SUMO3 overexpressed cells formed colonies in the soft agar assay, the SUMOylated MMP-7 might involved in cancer progression by chromatin remodeling. The detailed underlying mechanism will be addressed in the near future.