Impaired muscle growth and response to insulin-like growth factor 1 in dysferlin-mediated muscular dystrophy
Impaired muscle growth and response to insulin-like growth factor 1 in dysferlin-mediated muscular dystrophy
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DOI：
10.1093/hmg/ddq522
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发表时间：
2011-02-15
影响因子：
3.5
通讯作者：
McNally, Elizabeth M.
中科院分区：
文献类型：
--
作者：
Demonbreun, Alexis R.;Fahrenbach, John P.;McNally, Elizabeth M.
dysferlin的功能丧失突变导致肌营养不良，dysferlin与肌纤维中的重新密封膜破坏有关。鉴于膜融合在肌肉功能的许多方面的重要性，我们研究了dysferlin在肌肉生长中的作用。我们发现dysferlin缺失的成肌细胞在成肌细胞-肌管融合方面存在缺陷，导致培养物中的肌管较小。在体内，发现dysferlin无效肌肉具有错误定位的核和空泡化。我们发现，从dysferlin基因敲除小鼠分离的成肌细胞积累扩大的溶酶体相关膜蛋白2（LAMP 2）阳性溶酶体。Dysferlin无效成肌细胞积累转铁蛋白-488，反映异常囊泡运输。此外，dysferlin无效成肌细胞显示胰岛素样生长因子（IGF）受体的异常运输，其中受体穿梭于LAMP 2阳性溶酶体。我们研究了生长，在体内，通过注入生长刺激剂IGF 1的小鼠。对照组IGF 1治疗的小鼠如预期的那样增加了30%的肌纤维直径，而dysferlin null肌肉对IGF 1没有反应，表明肌纤维生长缺陷。我们还注意到，dysferlin空成纤维细胞也积累酸性囊泡，IGF受体和转铁蛋白，表明dysferlin是重要的非肌肉囊泡运输。这些数据表明dysferlin参与细胞内的多个膜融合事件，并提示dysferlin丢失导致肌肉疾病的多种途径。
Loss-of-function mutations in dysferlin cause muscular dystrophy, and dysferlin has been implicated in resealing membrane disruption in myofibers. Given the importance of membrane fusion in many aspects of muscle function, we studied the role of dysferlin in muscle growth. We found that dysferlin null myoblasts have a defect in myoblast-myotube fusion, resulting in smaller myotubes in culture. In vivo, dysferlin null muscle was found to have mislocalized nuclei and vacuolation. We found that myoblasts isolated from dysferlin null mice accumulate enlarged, lysosomal-associated membrane protein 2 (LAMP2)-positive lysosomes. Dysferlin null myoblasts accumulate transferrin-488, reflecting abnormal vesicular trafficking. Additionally, dysferlin null myoblasts display abnormal trafficking of the insulin-like growth factor (IGF) receptor, where the receptor is shuttled to LAMP2-positive lyososomes. We studied growth, in vivo, by infusing mice with the growth stimulant IGF1. Control IGF1-treated mice increased myofiber diameter by 30% as expected, whereas dysferlin null muscles had no response to IGF1, indicating a defect in myofiber growth. We also noted that dysferlin null fibroblasts also accumulate acidic vesicles, IGF receptor and transferrin, indicating that dysferlin is important for nonmuscle vesicular trafficking. These data implicate dysferlin in multiple membrane fusion events within the cell and suggest multiple pathways by which loss of dysferlin contributes to muscle disease.