Department of Biochemistry, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Hokkaido, Japan.
Mol Cell Biochem. 2011 Jun;352(1-2):163-72. doi: 10.1007/s11010-011-0750-4. Epub 2011 Feb 27.
Ubiquitination appears to be involved in proteasome-dependent proteolysis and in the membrane trafficking system including endocytosis and exocytosis. In this study, we identified MDA-9/syntenin as a novel ubiquitin-binding protein by a yeast two-hybrid system using modified ubiquitin in which lysine 48 is substituted by arginine. It has been reported that MDA-9/syntenin is a membrane-associated protein and regulates a cellular process involving endocytosis and intracellular transport. We found that MDA-9/syntenin binds to ubiquitin by a non-covalent bond and is ubiquitinated covalently. MDA-9/syntenin has no ubiquitin-binding motifs that have so far been reported, suggesting that MDA-9/syntenin physically interacts with ubiquitin via a novel binding motif. MDA-9/syntenin is stable in the cell, suggesting that ubiquitin binding of MDA-9/syntenin or ubiquitination of MDA-9/syntenin is not related to proteolysis. Furthermore, we showed that overexpression of wild-type MDA-9/syntenin enhances formation of filopodia, whereas MDA-9/syntenin lacking the PDZ domain inhibits the formation of filopodia, suggesting that MDA-9/syntenin plays an important role via interaction with ubiquitin in the regulation of cancer metastasis and invasion.
泛素化似乎参与了蛋白酶体依赖的蛋白水解和包括内吞作用和外排作用在内的膜运输系统。在这项研究中，我们通过使用赖氨酸 48 被精氨酸取代的改良泛素的酵母双杂交系统，鉴定出 MDA-9/syntenin 是一种新型的泛素结合蛋白。已经报道 MDA-9/syntenin 是一种膜相关蛋白，调节涉及内吞作用和细胞内运输的细胞过程。我们发现 MDA-9/syntenin 通过非共价键与泛素结合，并通过共价键被泛素化。MDA-9/syntenin 没有迄今为止报道的泛素结合基序，这表明 MDA-9/syntenin 通过新型结合基序与泛素物理相互作用。MDA-9/syntenin 在细胞中稳定存在，这表明 MDA-9/syntenin 的泛素结合或 MDA-9/syntenin 的泛素化与蛋白水解无关。此外，我们表明，野生型 MDA-9/syntenin 的过表达增强了丝状伪足的形成，而缺乏 PDZ 结构域的 MDA-9/syntenin 抑制了丝状伪足的形成，这表明 MDA-9/syntenin 通过与泛素相互作用在调节癌症转移和侵袭中发挥重要作用。
