Fumctional analysis of AEPP in skeletal muscle

锚蛋白重复序列蛋白（Ankyrin-repeat protein，Ankrd 2）是肌肉锚蛋白重复序列蛋白（muscle ankyrin repeat proteins，MARP）的一个成员，具有PEST基序和富含脯氨酸的区域（proline-rich region，Arpp），被认为参与肌肉应激反应途径。Arpp/Ankrd 2主要定位于横纹肌I带。然而，最近有报道称Arpp/Ankrd 2可以在体外与核蛋白如早幼粒细胞白血病蛋白（PML）、p53和YB- 1相互作用。在这项研究中，为了确定是否真的发生了Arpp/Ankrd 2的核积聚，我们对注射心脏毒素或与干冰接触而受伤的腓肠肌进行了免疫组织化学研究。我们发现Arpp/Ankrd 2在肌肉损伤后位于严重受损肌纤维附近的肌纤维核中积累。双标记免疫组化显示，Arpp/Ankrd 2积累在肌节损伤的肌纤维的细胞核中。此外，我们发现Arpp/Ankrd 2倾向于定位在常染色质中，在那里基因被转录激活。基于这些发现，我们认为Arpp/Ankrd 2可能在肌肉损伤时从I带转位到细胞核，并可能参与基因表达的调节。

Ankyrin-repeat protein with a PEST motif and a proline-rich region(Arpp), also designated as Ankrd2, is a member of the muscle ankyrin repeat proteins (MARPs), which have been proposed to be involved in muscle stress response pathways. Arpp/Ankrd2 is localized mainly in the I-band of striated muscle. However, it has recently been reported that Arpp/Ankrd2 can interact with nuclear proteins, such as premyelocytic leukemia protein (PML), p53 and YB- 1 in vitro. In this study, to determine whether nuclear accumulation of Arpp/Ankrd2 actually occurs, we performed an immunohistochemical investigation of gastrocnemius muscles that had been injured by injection of cardiotoxin or contact with dry ice. We found that Arpp/Ankrd2 accumulated in the nuclei of myofibers located adjacent to severely damaged myofibers after muscle injury. Double-labeled immunohistochemistry revealed that Arpp/Ankrd2 accumulated in the nuclei of sarcomere-damaged myofibers. Furthermore, we found that Arpp/Ankrd2 tended to be localized in euchromatin where genes are transcriptionally activated. Based on these findings, we suggest that Arpp/Ankrd2 may translocate from the I-band to the nucleus in response to muscle damage and may participate in the regulation of gene expression.