Histidine-rich glycoprotein (HRG) is a plasma protein synthesized by the liver. We have given the first evidence of a tissue localization of HRG demonstrating its presence in skeletal muscle, associated with the zinc enzyme AMP deaminase (AMPD1). Moreover, we have shown that muscle cells do not synthesize HRG, but they can internalize it from plasma. We have recently demonstrated by confocal laser scanning microscopy that in human skeletal muscle, HRG is mainly localized in the myofibrils, preferentially at the I-band of the sarcomere, in the sarcoplasm, and in the nuclei. Using transmission electron microscopy and immunogold analysis, we carried out this study on human and rat normal skeletal muscles with the purpose to deepen the ultrastructural localization of HRG in skeletal muscle fibers. The immunogold analysis evidenced the presence of HRG in the sarcomeres, mainly in the I-band and to a less extent in the A-band, in the heterochromatin of nuclei, and in the sarcoplasmic reticulum. The colocalization of HRG and skeletal muscle AMPD1 was also analyzed. A colabeling of HRG and AMPD1 was evident at sarcomeric, sarcoplasmic reticulum, and nuclear levels. The significance of these interesting and new results is discussed in this article.

中文翻译：

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骨骼肌纤维中富含组氨酸的糖蛋白的超微结构定位：与AMP脱氨酶共定位。

富含组氨酸的糖蛋白（HRG）是由肝脏合成的血浆蛋白。我们已经给出了HRG的组织定位的第一个证据，表明它在骨骼肌中的存在与锌酶AMP脱氨酶（AMPD1）有关。而且，我们已经表明，肌肉细胞不能合成HRG，但是它们可以从血浆中将其内在化。最近，我们通过共聚焦激光扫描显微镜证明，HRG在人的骨骼肌中主要位于肌原纤维中，优先位于肌节的I带，肌浆和细胞核中。使用透射电镜和免疫金分析，我们对人和大鼠的正常骨骼肌进行了这项研究，目的是加深HRG在骨骼肌纤维中的超微结构定位。免疫金分析表明HRG存在于肉瘤中，主要存在于I波段，而在A波段，核异染色质和肌浆网中存在程度较低。还分析了HRG和骨骼肌AMPD1的共定位。HRG和AMPD1的共标记在肌节，肌浆网和核水平很明显。本文讨论了这些有趣的新结果的重要性。