Examining protein interactions that stabilize the structure and function of SERCA pumps in muscle

我们身体中的肌肉细胞经常暴露在各种应激条件下，如高温或氧化应激，或者与各种疾病有关，如肌肉营养不良。当肌肉细胞暴露在应激中时，细胞内的钙水平会增加，据信细胞内钙的增加会导致细胞损伤甚至死亡。钙随应激而增加的一个主要原因是，负责维持肌肉中正常钙水平的酶，即钙泵，在应激时会受损。因此，如果能以某种方式保护钙泵，预计应激后细胞损伤将会减少，存活率将会提高。我们已经通过我们的研究确定，体内一种自然存在的蛋白质，称为热休克蛋白70(Hsp70)，可以在热应激时保护肌肉中的钙泵；然而，我们还没有弄清楚这是如何起作用的，也没有弄清楚肌肉中正常存在的其他蛋白质是否也可能保护钙泵。这个研究计划的一个主要的、长期的目标是进一步了解Hsp70和另外两种肌肉蛋白--磷蛋白(PLN)和肌磷脂(SLN)--如何在健康和患病的肌肉中，在广泛的环境条件下与钙泵相互作用并保护钙泵。为此，我们将使用这些蛋白质中的一种(Hsp70)的肌肉水平高于正常肌肉或完全缺乏蛋白质(S)(PLN和/或SLN)的转基因小鼠，然后我们将把肌肉组织暴露在各种类型的应激(即热、低氧、氧化应激)下，以确定在这些条件下，HSP70、PLN和SLN是否以及如何保护骨骼钙泵和保存肌肉功能。这项工作的第二个主要目标是了解PLN和SLN在从休息到运动条件的转变过程中如何控制钙泵和肌肉收缩特性。在肌肉收缩开始的一秒钟内，骨骼肌的力量产生和松弛诱导特性都得到了增强，但其中涉及的机制尚不完全清楚。我们将使用转基因小鼠来测试PLN和SLN在骨骼肌的这些经典特性中扮演重要角色的假设。总的来说，这项基础研究将建立对肌肉中钙泵的复杂调节以及在应激时保护这些至关重要的肌肉酶的结构和功能的细胞机制的更好理解。这项工作可能具有重要的影响，延伸到许多领域(即癌症和心脏病研究)，因为保护钙泵可以防止钙的增加，并在应激和某些疾病中改善细胞存活。

Muscle cells in our body are often exposed to a variety of stressful conditions such as heat or oxidative stress or in association with a variety of diseases such as muscular dystrophy. When muscle cells are exposed to stress, the calcium level inside the cells increases and it is believed that cell damage and even cell death will occur as a result of the increased cellular calcium. One major reason for the increase in calcium with stress is that the enzyme responsible for maintaining normal calcium levels in muscle, namely the calcium pump, becomes damaged with stress. Therefore, it would be expected that cell damage would be reduced and survival would be increased after stress if the calcium pump could somehow be protected. We have established through our research that a naturally occurring protein in the body, called heat shock protein 70 (Hsp70), can protect the calcium pump in muscle during heat stress; however, we haven't figured out exactly how this works yet or whether other proteins normally found in muscle might also protect the calcium pump. One major, long-term objective of this program of research is to understand how Hsp70 and two other muscle proteins called phospholamban (PLN) and sarcolipin (SLN), interact with and protect the calcium pump under a wide range of conditions in both healthy and diseased muscle. For this objective, we will use genetically modified mice that either have higher than normal muscle levels of one of these proteins (Hsp70) or completely lack the protein(s) (PLN and/or SLN) and we will expose the muscle tissues to various types of stress (i.e. heat, low oxygen, oxidative stress) to determine if, and how, Hsp70, PLN and SLN can protect the calcium pump and preserve muscle function under those conditions. A second major objective this work addresses is understanding how PLN and SLN control calcium pumps and muscle contractile properties during transitions from rest to exercising conditions. Within one second of the onset of muscle contraction there are enhancements in both force producing and relaxation inducing properties of skeletal muscle but the mechanisms involved are not completely understood. We will use genetically modified mice to test the hypotheses that PLN and SLN play an important role in these classic properties of skeletal muscle. Overall, this basic research will build better understanding of the complex regulation of calcium pumps in muscle and the cellular mechanisms that exist to protect the structure and function of these vital muscle enzymes during stress. This work could have important implications that extend into a number of fields (i.e. cancer and heart disease research) because protecting the calcium pump could prevent increases in calcium and improve cell survival following stress and in certain diseases.