Isoform-specific roles of the Na,K-ATPase in skeletal muscle

描述（由申请人提供）：骨骼肌无力和疲劳是心力衰竭、肌肉减少症、恶病质、肌肉营养不良症、慢性阻塞性肺病和其他疾病中常见的衰弱状态。Na， k - atp酶活性在肌肉收缩过程中被显著刺激，这是维持力量和运动表现所绝对需要的。然而，很少有研究检查Na， k - atp酶同工型在肌肉无力和疲劳中的作用。成人骨骼肌主要表达？Na， k - atp酶的2异构体，与大多数主要表达？1)同种型。的作用？2在骨骼肌中的异构体及其激活其活性的机制尚不清楚。本研究的中心假设是Na， k - atp酶？2异构体提供了一种储备能力，这种储备能力在休息时基本上不活跃，但在收缩时迅速受到刺激，以满足对Na/K运输的增加需求；它的调节部分是通过Na - k - atp酶的肌肉特异性FXYD1亚基的磷酸化来实现的。这一假设将通过一种新的基因来验证，这种基因专门针对缺乏Na， k - atp酶？在成人骨骼肌（sk?? ?）2-/-)，表现出明显的运动不耐受和骨骼肌无力。具体目的是：1)确定Na， k - atp酶的急性作用？2酶维持力量和运动表现；2)确定Na， k - atp酶的作用？2 .酶在膜上激发横小管和抗疲劳；3) a，明确FXYD1磷酸化在Na， k - atp酶急性刺激中的作用？2 .活动由？收缩时2-肾上腺素能受体的激活；b、确定Na、k - atp酶含量或功能改变对心力衰竭患者肌肉疲劳和运动不耐受的影响。这些目标将采用一种综合策略来实现，该策略将小鼠的遗传操作与从动物到细胞和亚细胞水平的功能测量相结合。总的来说，这个项目将促进我们对Na， k - atp酶？2异构体及其在骨骼肌中的调节机制，并确定肌肉无力和疲劳治疗干预的新分子靶点。

DESCRIPTION (provided by applicant): Skeletal muscle weakness and fatigue is a common, debilitating condition in heart failure, sarcopenia, cachexia, muscular dystrophies, COPD, and other disorders. Na,K-ATPase activity is dramatically stimulated during muscle contraction and is absolutely required to maintain force and exercise performance. However, few studies have examined the role the Na,K-ATPase isoforms in muscle weakness and fatigue. Adult skeletal muscles express mainly the ?2 isoform of the Na,K-ATPase, in contrast to most other tissues which express mainly the ?1 isoform. The role of the ?2 isoform in skeletal muscle and the mechanisms by which its activity is stimulated are not known. The central hypotheses of this research is that the Na,K-ATPase ?2 isoform provides a reserve capacity which is largely inactive at rest but is rapidly stimulated during contraction, to meet the increased demand for Na/K transport; and that its regulation is achieved in part by phosphorylation of the muscle-specific FXYD1 subunit of the Na,K-ATPase. This hypothesis will be tested using a novel gene targeted mouse which specifically lacks the Na,K-ATPase ?2 in adult skeletal muscles (sk??2-/-) and shows marked exercise intolerance and skeletal muscle weakness. The Specific Aims are to: 1) Determine the acute role of the Na,K-ATPase ?2 enzyme in maintaining force and exercise performance; 2) Determine the role of the Na,K-ATPase ?2 enzyme in membrane excitation in the transverse tubules and resistance to fatigue; and 3) a, Define the role of FXYD1 phosphorylation in the acute stimulation of Na,K-ATPase ?2 activity by ?2- adrenergic receptor activation during contraction; b, Determine the contribution of altered Na,K-ATPase content or function to muscle fatigue and exercise intolerance in heart failure. These Aims will be approached using an integrated strategy which combines genetic manipulations in the mouse with functional measurements from the animal to the cellular and subcellular level. Collectively, this project will advance our understanding of the physiological roles of the Na,K-ATPase ?2 isoform and the mechanisms by which it is regulated in skeletal muscle, and identify new molecular targets for therapeutic interventions in muscle weakness and fatigue.