Olfactory receptor signaling in skeletal muscle

描述(申请人提供)：适当的肌肉再生对于恢复创伤后正常的肌肉结构和功能是必要的。异常再生可导致肌纤维大小、数量和结构的改变。肌纤维具有异常的分支细胞结构，在各种神经肌肉疾病以及包括人类在内的各种严重肌肉损伤后都普遍存在。这些异常的肌纤维是脆弱的，含有高比例肌纤维的肌肉与虚弱和损伤发生率增加之间存在相关性。含有高水平分支肌纤维的肌肉不太可能以正常的生理方式发挥作用。到目前为止，调控肌纤维分支的机制和分子还不清楚。调控肌纤维分支的机制对于从基础和临床角度阐明肌纤维分支具有重要意义。我们最近确定了小鼠气味受体23(MOR23)在小鼠骨骼肌再生中的新作用，并确定了第一个在肌纤维分支中起功能作用的分子。嗅觉神经元上的气味受体信号通过腺酰环化酶3(AC3)和蛋白激酶A(PKA)依赖的信号通路来调节几种黏附和化学吸引分子的表达。在骨骼肌中受MOR23信号调控的下游分子在肌纤维分支中发挥作用尚不清楚。这一建议将阐明MOR23调节小鼠肌纤维分支的分子途径。根据我们的初步数据，我们假设骨骼肌中MOR23的激活刺激了AC3和蛋白激酶A(PKA)信号，导致调节肌肉细胞迁移和黏附的下游分子发生变化，从而导致肌纤维分支。我们将使用不同的遗传小鼠模型来测试这些不同的分子在调节肌肉细胞迁移和黏附以及肌纤维分支方面的作用。提出的实验是新颖的，因为他们是第一个从机械上剖析肌纤维分支调节的实验。气味受体信号通路及其下游分子效应器可作为减少各种神经肌肉疾病肌纤维分支的有效药理靶点。减少分支肌纤维的数量可能有利于改善肌肉生理学，并提高细胞和基因治疗肌肉疾病的效率。 公共卫生相关性：具有异常分支形状的肌肉细胞通常在各种肌肉疾病以及严重肌肉损伤后被发现。这些异常的肌肉细胞是脆弱的，含有高比例这类细胞的肌肉更虚弱，更容易受伤。这些分枝的肌肉细胞是如何产生的尚不清楚。无论从基础科学还是临床角度来看，调控这些异常肌肉细胞形成的机制都是重要的。我们将使用生化和遗传方法来操纵几个我们假设在肌肉细胞分支中发挥作用的分子的功能，并分析结果。拟议中的实验是新颖的，因为它们是第一个从机械上剖析肌肉细胞分支调节的实验。在未来，正在研究的途径可能会导致药物治疗，以消除各种肌肉疾病中的这些异常肌肉细胞。

DESCRIPTION (provided by applicant): Proper muscle regeneration is necessary to restore normal muscle architecture and function after traumatic injury. Aberrant regeneration can result in alterations in myofiber size, number and architecture. Myofibers with an abnormal branching cytoarchitecture are commonly found in various neuromuscular diseases as well as after severe muscle injury in various species, including human. These aberrant myofibers are fragile and a correlation exists between muscles containing a high percentage of these myofibers and weakness and increased incidence of injury. Muscles containing high levels of branched myofibers are unlikely to function in a normal physiologic manner. To date the mechanisms and molecules regulating myofiber branching have been obscure. The mechanisms regulating myofiber branching are significant to elucidate from both a basic and a clinical standpoint. We recently established a novel role for mouse odorant receptor 23 (MOR23) in skeletal muscle regeneration in mice and identified the first molecule with a functional role in myofiber branching. Odorant receptor signaling in olfactory neurons regulates expression of several adhesion and chemoattractant molecules through an adenylyl cyclase 3 (AC3) and protein kinase A (PKA) dependent signaling pathway. The downstream molecules regulated by MOR23 signaling in skeletal muscle that play a role in myofiber branching are unknown. This proposal will elucidate the molecular pathway by which MOR23 regulates myofiber branching in mice. Based on our preliminary data we hypothesize that activation of MOR23 in skeletal muscle stimulates AC3 and protein kinase A (PKA) signaling leading to changes in downstream molecules that regulate muscle cell migration and adhesion and thus, myofiber branching. We will use various genetic mouse models to test the roles of these different molecules in regulating muscle cell migration and adhesion as well as myofiber branching. The proposed experiments are novel because they are the first to mechanistically dissect regulation of myofiber branching. Odorant receptor signaling pathways and their downstream molecular effectors may serve as effective pharmacologic targets for decreasing myofiber branching in various neuromuscular disorders. Decreasing the number of branched myofibers will likely be beneficial for improving both muscle physiology and the efficiency of cell and gene therapy approaches for muscular disorders. PUBLIC HEALTH RELEVANCE: Muscle cells with an abnormal branching shape are commonly found in various muscle diseases as well as after severe muscle injury. These abnormal muscle cells are fragile and muscles containing a high percentage of these types of cells are weaker and become injured more easily. How these branched muscle cells arise is unknown. The mechanisms regulating the formation of these abnormal muscle cells is important to define from both a basic science and a clinical standpoint. We will use biochemical and genetic methods to manipulate the function of several molecules we hypothesize to play a role in muscle cell branching and analyze the outcome. The proposed experiments are novel because they are the first to mechanistically dissect regulation of muscle cell branching. In the future, the pathway under study may lead to drug therapies for eliminating these abnormal muscle cells in various muscle disorders.