NET37, a Nuclear Envelope Transmembrane Protein with Glycosidase Homology, Is Involved in Myoblast Differentiation
NET37, a Nuclear Envelope Transmembrane Protein with Glycosidase Homology, Is Involved in Myoblast Differentiation
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DOI：
10.1074/jbc.m109.034041
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发表时间：
2009-10-23
影响因子：
4.8
通讯作者：
Gerace, Larry
中科院分区：
文献类型：
--
作者：
Datta, Kaustuv;Guan, Tinglu;Gerace, Larry
核纤层及其相关蛋白对于核结构和染色质组织是重要的，并且还涉及细胞信号传导和基因表达的调节。在这项研究中，我们证明，核纤层相关的核膜跨膜蛋白NET 37所需的肌分化的C2 C12细胞。NET 37是糖苷酶家族31的成员，在小鼠骨骼肌中高度表达，并且在C2 C12分化期间强烈上调。通过蛋白酶作图，我们发现它的糖苷酶同源结构域位于核膜/内质网的内腔。当NET 37通过RNAi从增殖的成肌细胞中耗尽时，成肌分化显著受损，并且伴随着晚期成肌转录因子肌细胞生成素的上调延迟。我们表达了在糖苷酶结构域中的保守残基处突变的沉默抗性NET 37，并发现这种预测的催化失活蛋白不能支持野生型NET 37耗尽的细胞中的肌生成。因此，NET 37的酶功能似乎对肌源性分化很重要。NET 37耗尽的C2 C12细胞在转移到分化培养基后具有降低的Akt活化，并且在胰岛素样生长因子-II（IGF-II）分泌方面有缺陷，胰岛素样生长因子-II是参与Akt活化的自分泌/旁分泌因子。我们还观察到pro-IGF-II与NET 37共免疫沉淀。基于我们的研究结果，我们提出NET 37在成肌细胞分化过程中的分泌途径中IGF-II成熟中起作用。NET 37在核膜上的定位提高了它可能通过跨膜通讯在核内部和内质网腔之间协调肌源性事件的可能性。
The nuclear lamina and its associated proteins are important for nuclear structure and chromatin organization and also have been implicated in the regulation of cell signaling and gene expression. In this study we demonstrate that the lamina-associated nuclear envelope transmembrane protein NET37 is required for myogenic differentiation of C2C12 cells. NET37, a member of glycosidase family 31, is highly expressed in mouse skeletal muscle and is strongly up-regulated during C2C12 differentiation. By protease mapping we show that its glycosidase homology domain is located in the lumen of the nuclear envelope/endoplasmic reticulum. When NET37 is depleted from proliferating myoblasts by RNAi, myogenic differentiation is significantly impaired, and there is a concomitant delay in up-regulation of the late myogenic transcription factor myogenin. We expressed silencing-resistant NET37 mutated at a conserved residue in the glycosidase domain and found that this predicted catalytically inactive protein is unable to support myogenesis in cells depleted of wild type NET37. Therefore, the enzymatic function of NET37 appears to be important for myogenic differentiation. C2C12 cells depleted of NET37 have reduced activation of Akt after shifting to differentiation medium and are defective in insulin like growth factor-II (IGF-II) secretion, an autocrine/paracrine factor involved in Akt activation. We also observed that pro-IGF-II co-immunoprecipitates with NET37. Based on our results, we propose that NET37 has a role in IGF-II maturation in the secretory pathway during myoblast differentiation. The localization of NET37 at the nuclear envelope raises the possibility that it may coordinate myogenic events between the nuclear interior and the endoplasmic reticulum lumen via transmembrane communication.