Nuclear import of αB-crystallin is phosphorylation-dependent and hampered by hyperphosphorylation of the myopathy-related mutant R120G
Nuclear import of αB-crystallin is phosphorylation-dependent and hampered by hyperphosphorylation of the myopathy-related mutant R120G
复制标题
DOI：
10.1074/jbc.m504106200
复制
发表时间：
2005-11-04
影响因子：
4.8
通讯作者：
Boelens, WC
中科院分区：
文献类型：
--
作者：
den Englesman, J;Gerrits, D;Boelens, WC
磷酸化调节αB-晶状体蛋白作为分子伴侣的功能。在此，我们探讨了磷酸化在HeLa细胞中αB-晶状体蛋白的核输入和细胞定位中的作用。核输出的抑制表明，αB-晶状体蛋白的磷酸化是输入细胞核所必需的。突变分析表明，Ser-59的磷酸化是核输入的关键，Ser-45的磷酸化是斑点定位所必需的。免疫共沉淀实验表明，αB-晶状体蛋白的输入可能受其与存活运动神经元(SMN)蛋白磷酸化依赖的相互作用的调控，SMN蛋白是小核核糖核蛋白核输入和组装的重要因素。这种相互作用得到了内源性磷酸化的αB晶状体蛋白与SMN在核结构中的共同定位的支持。引起心肌病的αB晶状体蛋白突变体R120G被发现过度磷酸化，干扰了SMN相互作用和核输入，并导致细胞质内含物的形成。与其他蛋白质聚集障碍一样，过度磷酸化似乎是αB晶体蛋白R120G致病的一个重要方面。
Phosphorylation modulates the functioning of alpha B-crystallin as a molecular chaperone. We here explore the role of phosphorylation in the nuclear import and cellular localization of alpha B-crystallin in HeLa cells. Inhibition of nuclear export demonstrated that phosphorylation of alpha B-crystallin is required for import into the nucleus. As revealed by mutant analysis, phosphorylation at Ser-59 is crucial for nuclear import, and phosphorylation at Ser-45 is required for speckle localization. Co-immunoprecipitation experiments suggested that the import of alpha B-crystallin is possibly regulated by its phosphorylation-dependent interaction with the survival motor neuron (SMN) protein, an important factor in small nuclear ribonucleoprotein nuclear import and assembly. This interaction was supported by co-localization of endogenous phosphorylated alpha B-crystallin with SMN in nuclear structures. The cardiomyopathy-causing alpha B-crystallin mutant R120G was found to be excessively phosphorylated, which disturbed SMN interaction and nuclear import, and resulted in the formation of cytoplasmic inclusions. Like for other protein aggregation disorders, hyperphosphorylation appears as an important aspect of the pathogenicity of alpha B-crystallin R120G.