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

我们体内的肌肉细胞经常暴露在各种压力条件下，如高温或氧化应激，或与各种疾病有关，如肌肉萎缩症。当肌肉细胞受到压力时，细胞内的钙含量会增加，据信，细胞损伤甚至细胞死亡都会发生，这是细胞钙含量增加的结果。压力下钙含量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，在压力下受到损害。因此，如果能以某种方式保护钙泵，可以减少应激后的细胞损伤，提高细胞存活率。我们通过研究发现，人体内天然存在一种叫做热休克蛋白70 （Hsp70）的蛋白质，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通常发现的其他蛋白质是否也能保护钙泵。该研究项目的一个主要长期目标是了解Hsp70和另外两种肌肉蛋白，即磷蛋白（PLN）和肌磷脂（SLN），如何在健康和患病肌肉的广泛条件下与钙泵相互作用并保护钙泵。为此，我们将使用具有高于正常肌肉水平的这些蛋白质（Hsp70）或完全缺乏蛋白质（PLN和/或SLN）的转基因小鼠，我们将使肌肉组织暴露于各种类型的应激（即热，低氧，氧化应激），以确定Hsp70， PLN和SLN是否以及如何在这些条件下保护钙泵并保持肌肉功能。本研究的第二个主要目标是了解PLN和SLN如何在从休息到运动状态的过渡过程中控制钙泵和肌肉收缩特性。在肌肉收缩开始的一秒钟内，骨骼肌产生力和诱导松弛的特性都有所增强，但其中的机制尚不完全清楚。我们将使用转基因小鼠来验证PLN和SLN在骨骼肌的这些经典特性中起重要作用的假设。总的来说，这项基础研究将更好地理解肌肉中钙泵的复杂调节，以及存在的细胞机制，以保护这些重要肌肉酶在压力下的结构和功能。这项工作可能会对许多领域（如癌症和心脏病研究）产生重要影响，因为保护钙泵可以防止钙的增加，并提高压力和某些疾病后的细胞存活率。

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.