Fan X, Dion P, Laganiere J, Brais B, Rouleau G A
Center for Research in Neuroscience, McGill University, and the McGill University Health Center, 1650 Cedar Avenue, Montreal, Quebec H3G 1A4, Canada.
Hum Mol Genet. 2001 Oct 1;10(21):2341-51. doi: 10.1093/hmg/10.21.2341.
Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disorder characterized by progressive eyelid drooping, swallowing difficulties and proximal limb weakness. The autosomal dominant form of this disease is caused by short expansions of a (GCG)(6) repeat to (GCG)(8-13) in the PABPN1 gene, which results in the expansion of a polyalanine stretch from 10 to 12-17 alanines in the N-terminus of the protein. Mutated PABPN1 (mPABPN1) is able to induce nuclear protein aggregation and form filamentous nuclear inclusions, which are the pathological hallmarks of OPMD. PABPN1, when bound to poly(A) RNA, forms both linear filaments and discrete-sized, compact oligomeric particles in vitro. In the absence of poly(A) RNA, PABPN1 can form oligomers. Here we report that: (i) oligomerization of PABPN1 is mediated by two potential oligomerization domains (ODs); (ii) inactivating oligomerization of mPABPN1 by deletions of 6-8 amino acids in either of the ODs prevents nuclear protein aggregation; (iii) expression of mPABPN1 in COS-7 cells is associated with cell death; and (iv) preventing nuclear protein aggregation by inactivating oligomerization of mPABPN1 significantly reduces cell death. These findings suggest that oligomerization of PABPN1 plays a crucial role in the formation of OPMD nuclear protein aggregation, while the expanded polyalanine stretch is necessary but not sufficient to induce OPMD protein aggregation, and that the nuclear protein aggregation might be toxic and cause cell death. These observations also imply that inactivation of oligomerization of mPABPN1 might be a useful therapeutic strategy for OPMD.
眼咽型肌营养不良症（OPMD）是一种成年起病的疾病，其特征为进行性眼睑下垂、吞咽困难和近端肢体无力。该疾病的常染色体显性形式是由PABPN1基因中（GCG）（6）重复序列短片段扩展为（GCG）（8 - 13）所致，这导致蛋白质N端的多聚丙氨酸序列从10个丙氨酸扩展至12 - 17个丙氨酸。突变的PABPN1（mPABPN1）能够诱导核蛋白聚集并形成丝状核内包涵体，这些是OPMD的病理标志。PABPN1与多聚腺苷酸（poly(A)）RNA结合时，在体外形成线性细丝和离散大小的紧密寡聚颗粒。在没有poly(A) RNA的情况下，PABPN1可以形成寡聚物。在此我们报告：（i）PABPN1的寡聚化由两个潜在的寡聚化结构域（ODs）介导；（ii）通过缺失任一OD中的6 - 8个氨基酸使mPABPN1的寡聚化失活可防止核蛋白聚集；（iii）mPABPN1在COS - 7细胞中的表达与细胞死亡相关；（iv）通过使mPABPN1的寡聚化失活来防止核蛋白聚集可显著减少细胞死亡。这些发现表明，PABPN1的寡聚化在OPMD核蛋白聚集的形成中起关键作用，而扩展的多聚丙氨酸序列是诱导OPMD蛋白聚集所必需但不充分的条件，并且核蛋白聚集可能具有毒性并导致细胞死亡。这些观察结果还暗示，使mPABPN1的寡聚化失活可能是治疗OPMD的一种有用策略。
