VCP-dependent muscle degeneration is linked to defects in a dynamic tubular lysosomal network in vivo.
VCP-dependent muscle degeneration is linked to defects in a dynamic tubular lysosomal network in vivo.
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DOI：
10.7554/elife.07366
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发表时间：
2015-07-13
期刊：
影响因子：
7.7
通讯作者：
Davis GW
中科院分区：
文献类型：
--
作者：
Johnson AE;Shu H;Hauswirth AG;Tong A;Davis GW
溶酶体被经典地看作是囊泡结构，货物被递送到其中进行降解。在这里，我们确定了一个网络的动态，管状溶酶体延伸到整个果蝇肌肉，在体内。活体成像显示自噬体与管状溶酶体合并，溶酶体膜经历延伸、收缩、融合和分裂。这种管状溶酶体网络的动力学和完整性需要VCP，VCP是一种AAA-ATP酶，当突变时，会导致肌肉，骨骼和神经元的退行性疾病。我们发现，人类VCP挽救了果蝇VCP缺失和疾病相关VCP转基因过表达导致的缺陷，使肾小管溶酶体功能障碍与人类VCP相关疾病联系起来。最后，管状溶酶体的破坏与受损的自噬体-溶酶体融合、增加的细胞质多聚泛素聚集体、脂褐质物质、受损的线粒体和受损的肌肉功能相关。我们建议，VCP维持肌浆蛋白质，在一定程度上，通过控制动态管状溶酶体网络的完整性。DOI：http://dx.doi.org/10.7554/eLife.07366.001一种产生含瓦洛辛蛋白（简称VCP）的蛋白质的基因突变会导致影响大脑、肌肉和骨骼的退行性疾病。在近一半患有这些与VCP相关的疾病的人中-也可能导致痴呆症，佩吉特骨病和肌萎缩侧索硬化症（ALS）-第一个症状是肌肉无力。目前，人们对VCP如何影响肌肉知之甚少。VCP相关疾病的患者通常难以清除细胞中受损的蛋白质，最近的研究表明，VCP对于形成称为溶酶体的细胞结构很重要。溶酶体含有强大的酶，可以破坏受损的蛋白质和其他细胞结构，否则这些蛋白质和其他细胞结构会在细胞中积累。在大多数细胞中，溶酶体看起来像气泡样的隔间，称为囊泡。然而，在某些类型的细胞中，已经观察到溶酶体形成了一个在整个细胞内部延伸的小管网络。然而，目前尚不清楚这些小管的作用，它们如何在细胞中形成以及它们是否在疾病中发生变化。约翰逊等人分析了果蝇（Drosophila melanogaster）肌肉中的溶酶体，发现溶酶体以微管网络的形式遍布每个肌细胞。这些小管在活体肌肉中不断变化;延伸，收缩，断裂和合并，形成一个大的管状溶酶体网络。当约翰逊等人通过一种称为RNA干扰的方法减少肌肉细胞产生的VCP量时，溶酶体小管分解成不再不断变化的囊泡。修改这些有缺陷的苍蝇肌肉细胞，使它们产生人类VCP蛋白质，导致小管再次形成。这些结果表明，人类和苍蝇的VCP蛋白是非常相似的，他们发挥了关键作用，无论是溶酶体形成小管的能力或现有的小管的维护。然后，约翰逊等人改造果蝇，使其产生一种VCP蛋白，这种蛋白具有在退行性疾病患者中常见的突变。在这些果蝇的肌肉细胞中，溶酶体小管没有正确形成。这些果蝇还有其他异常;例如，它们的细胞显示出大量受损蛋白质的积累，并且它们移动肌肉的能力较弱。这些发现表明，溶酶体小管网络对于健康的肌肉细胞是必要的，但是这些小管网络是如何以及为什么形成或维持的仍然是个谜。是什么导致溶酶体膜形成小管？它们是如何断裂和融合的？为什么它们是必要的？果蝇的遗传实验将是发现这些机制并了解与人类退行性疾病联系的好地方。DOI：http://dx.doi.org/10.7554/eLife.07366.002网站
Lysosomes are classically viewed as vesicular structures to which cargos are delivered for degradation. Here, we identify a network of dynamic, tubular lysosomes that extends throughout Drosophila muscle, in vivo. Live imaging reveals that autophagosomes merge with tubular lysosomes and that lysosomal membranes undergo extension, retraction, fusion and fission. The dynamics and integrity of this tubular lysosomal network requires VCP, an AAA-ATPase that, when mutated, causes degenerative diseases of muscle, bone and neurons. We show that human VCP rescues the defects caused by loss of Drosophila VCP and overexpression of disease relevant VCP transgenes dismantles tubular lysosomes, linking tubular lysosome dysfunction to human VCP-related diseases. Finally, disruption of tubular lysosomes correlates with impaired autophagosome-lysosome fusion, increased cytoplasmic poly-ubiquitin aggregates, lipofuscin material, damaged mitochondria and impaired muscle function. We propose that VCP sustains sarcoplasmic proteostasis, in part, by controlling the integrity of a dynamic tubular lysosomal network. DOI: http://dx.doi.org/10.7554/eLife.07366.001 Mutations in a gene that produces a protein called Valosin-containing protein (VCP for short) causes degenerative diseases that affect the brain, muscle and bone. In nearly half of the individuals with these VCP-related diseases—which can also result in dementia, Paget's disease of the bone and amyotrophic lateral sclerosis (ALS)—the first symptom is muscle weakness. Currently, very little is known about how VCP affects muscles. Patients with VCP-related diseases often have problems clearing damaged proteins from their cells, and recent research suggests that VCP is important for forming a cellular structure known as a lysosome. Lysosomes contain powerful enzymes that destroy damaged proteins and other cellular structures that would otherwise accumulate in the cells. In most cells, lysosomes look like bubble-like compartments called vesicles. However, in some types of cells lysosomes have been observed to form a network of tubules that extend throughout the cell interior. However, it remains unclear what these tubules do, how they form in cells and whether they are altered in disease. Johnson et al. analyzed lysosomes in the muscle of the fruit fly species Drosophila melanogaster and discovered that lysosomes were in the form of a network of tubules that spread throughout each muscle cell. These tubules constantly changed in living muscles; extending, retracting, breaking and merging to form a large tubular lysosome network. When Johnson et al. reduced the amount of VCP produced by the muscle cells, via a method called RNA interference, the lysosome tubules broke down into vesicles that were no longer constantly changing. Modifying these defective fly muscle cells so that they produced the human VCP protein caused the tubules to form again. These results suggest that the human and fly VCP proteins are very similar and that they play a key role in either the ability of lysosomes to form tubules or the maintenance of existing tubules. Johnson et al. then engineered flies to produce a version of the VCP protein that had mutations commonly seen in individuals with degenerative diseases. Lysosome tubules did not form correctly in the muscle cells of these flies. These flies also had other abnormalities; for example, their cells showed a great build-up of damaged proteins, and their ability to move their muscles was weaker. These findings suggest that a network of lysosomal tubules is necessary for healthy muscle cells, but how and why these tubular networks are formed or maintained is still mysterious. What causes lysosomal membranes to form tubules? How do they break and fuse? And why are they necessary? Genetic experiments in fruit flies will be a great place to discover these mechanisms and understand the links to degenerative diseases in humans. DOI: http://dx.doi.org/10.7554/eLife.07366.002