Titin-based mechanotransduction in skeletal muscle atrophy and hypertrophy

我们的目标是了解机械输入如何转换为生化信号。我们正在研究肌联蛋白缺陷小鼠模型，缺乏弹性或肌联蛋白蛋白内的信号结构域。在第一个资助期产生的这些动物模型的基础上，我们将扩展肌联蛋白激酶结构域（TK）敲除的表型分析，以研究TK依赖性运动不耐受的分子基础，这概括了糖原累积病患者的症状。因此，我们还将监测TK敲除小鼠中的糖原和葡萄糖稳态。为了了解代谢和营养表型的分子基础，我们将分别研究TK敲除小鼠在去神经支配和运动后的萎缩/肥大信号传导，并采用基于细胞培养的系统来解决激酶结构域如何被激活。我们相信，我们将能够将这些发现与我们在第一次资助期间在冬眠的灰熊中获得的蛋白质表达结果相结合。我们将分析导致小鼠机械传导受损的候选蛋白，以及与灰熊缺乏废用性萎缩相关的候选蛋白。了解保护肌肉免于萎缩的营养信号和肌联蛋白作为机械传感器的作用，将有助于我们不仅阐明原发性肌联蛋白肌病，而且了解卧床不起的患者，航天和久坐不动的老年人的萎缩。

Our aim is to understand how mechanical input is converted into biochemical signals. We are studying titin-deficient mouse models that lack elastic or signaling domains within the titin protein. Building on these animal models generated in the first funding period, we will extend the phenotypic analysis of the titin kinase domain (TK) knockout to investigate the molecular basis of the TK-dependent exercise intolerance, which recapitulates symptoms found in patients with glycogen storage disease. Therefore, we will also monitor glycogen and glucose homeostasis in the TK knockout mouse. Towards understanding the molecular basis of the metabolic and trophic phenotype, we will investigate atrophy/hypertrophy signaling in the TK knockout mouse after denervation and exercise, respectively and employ a cell culture-based system to resolve how the kinase domain is activated. We believe that we will be able to couple these findings to the protein-expression results we obtained in the hibernating grizzly bear during the first funding period. We will analyze candidate proteins that cause impaired mechano-transduction in the mouse and the candidate proteins associated with lack of disuse atrophy in grizzly bear. Understanding trophic signaling that protects muscle from atrophy and the role of titin as a mechanosensor, will help us not only to elucidate primary titin-based myopathies, but also to understand atrophy in bedridden patients, spaceflight, and the sedentary elderly.