Actin cytoskeleton: Regulation through protein interactions and epigenetic re-programming

人体中每个细胞的形状由称为细胞骨架的内部结构决定，细胞骨架是一种相互连接的蛋白质网络，它提供了一种“承重”结构，使运动成为可能，并提供保护，免受潜在的破坏性外力的影响。两种最重要的细胞骨架蛋白是肌动蛋白和肌球蛋白。单个肌动蛋白分子可以连接在一起形成长纤维。肌球蛋白是一种大型蛋白质复合物，由2条重链、2条必需轻链和2条调节轻链组成。肌动蛋白纤维和肌球蛋白复合物相互结合，当肌球蛋白被激活时，它会拉动它们所结合的肌动蛋白纤维，缩短肌动蛋白-肌球蛋白纤维的长度，并导致细胞骨架网络的张力。由于细胞骨架负责保护细胞免受破坏性外力的影响，因此细胞调整其细胞骨架的物理强度以适应不断变化的环境非常重要。细胞强化其细胞骨架的一个重要方式是激活肌球蛋白复合物以缩短肌动蛋白-肌球蛋白纤维的长度。这种肌动蛋白-肌球蛋白纤维缩短产生细胞骨架张力，使细胞物理上更僵硬。除了肌球蛋白活化，与细胞骨架相关的蛋白质集合也可能发生变化。在这个提议中，我们将确定当细胞骨架放松时作为细胞骨架一部分的蛋白质，并发现当细胞骨架变得紧张时相关蛋白质的集合如何变化。如果环境对细胞施加压力的方式发生长期变化，细胞可能会通过快速改变特定基因的表达方式来补偿，甚至通过修改它们的DNA来改变有助于细胞骨架物理强度的基因的长期表达。在这个提议中，我们将确定如果细胞骨架张力延长，细胞是否会“重新连接”它们的DNA以改变基因表达模式，并且我们将鉴定由于这些DNA改变而表达不同的细胞因子相关基因。该提案中的实验将首次系统地研究细胞骨架中的蛋白质复合物如何在松弛和收缩状态之间变化，以及持续的细胞骨架收缩如何改变编码与细胞骨架组织和功能相关的蛋白质的基因表达。拟议的研究将使加拿大人受益：（1）导致细胞生物学和细胞骨架调节方面的新发现，这将提高加拿大的科学声誉和创新潜力;（2）培训高素质的人员，以扩大他们的职业前景，提高他们未来在学术或工业生物医学研究中的就业能力，使他们能够为加拿大的知识经济做出贡献; 3）开发新的多学科方法，并产生独特的生物研究工具，将与加拿大研究界分享。

The shape of each cell in the human body is determined by an internal structure called the cytoskeleton, which is a network of interconnected proteins that provides a "load-bearing" structure that enables movement and provides protection from potentially damaging external forces. Two of the most important cytoskeleton proteins are actin and myosin. Individual actin molecules can be joined together to form long fibres. Myosin is a large protein complex, composed of 2 heavy chains, 2 essential light chains and 2 regulatory light chains. Actin fibres and myosin complexes bind to each other, and when myosin is activated it pulls on the actin fibres they are bound to, shortening the length of actin-myosin fibres and leading to tension in the cytoskeleton network. Since the cytoskeleton is responsible for protecting cells from damaging external forces, it is important for cells to adjust the physical strength of their cytoskeleton to adapt to changing environments. An important way that cells reinforce their cytoskeleton is to activate the myosin complex to shrink the length of actin-myosin fibres. This actin-myosin fibre shortening produces cytoskeleton tension that makes cells physically stiffer. In addition to myosin activation, there may be changes in the collection of proteins that are associated with the cytoskeleton. In this proposal, we will identify the proteins that are part of the cytoskeleton when it is relaxed, and discover how the collection of associated proteins changes when the cytoskeleton becomes tense. If the environment undergoes long term changes in how it exerts pressure on cells, cells may compensate by rapidly changing how specific genes are expressed, and even by modifying their DNA to alter the long-term expression of genes that contribute to the cytoskeleton's physical strength. In this proposal, we will determine if cells "re-wire" their DNA to change gene expression patterns if cytoskeleton tension is prolonged, and we will identify the cytoskeleton-related genes that are expressed differently as a result of these DNA alterations. The experiments in this proposal will be the first to systematically examine how the complex of proteins in the cytoskeleton changes between the relaxed and contracted states, and how sustained cytoskeleton contraction alters the expression of genes encoding for proteins related to cytoskeleton organization and function. The proposed research will benefit Canadians by: 1) Leading to novel discoveries in cell biology and cytoskeleton regulation that will enhance Canada's scientific reputation and innovation potential; 2) Training of highly-qualified personnel to expand their career perspectives and increase future employability in academic or industrial biomedical research so that they may contribute to Canada's knowledge economy; 3) Development of novel multi-disciplinary approaches and generation of unique biological research tools that will be shared with the Canadian research community.