Estrogen, Myosin Phosphorylation and Muscle Thermogenesis

雌激素、肌球蛋白磷酸化和肌肉生热作用

• 批准号: RGPIN-2019-04339
• 负责人: Vandenboom, Rene
• 金额: $ 2.04万
• 依托单位: Brock University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=682334
• 关键词: Estrogen; Myosin; Phosphorylation; Muscle; Thermogenesis

The long term goals of my research program are to further our understanding of how the posttranslational modification of myosin by phosphorylation modulates contractile function of skeletal muscle. In mammalian striated muscle the transfer of a phosphate moiety from adenosine triphosphate (i.e. ATP) to a serine residue on the myosin regulatory light chain (RLC) is catalyzed by skeletal myosin light chain kinase (skMLCK). This reaction is regulated by a calcium and calmodulin signalling cascade that is activated during contraction. In turn, skMLCK catalyzed phosphorylation of the myosin RLC increases the calcium sensitivity of the contractile proteins, thus increasing submaximal force and producing what is known as "potentiation". Strong associations between contraction-induced RLC phosphorylation and potentiation have been demonstrated in a variety of rodent fast twitch skeletal muscle models. By contrast, although rodent slow twitch muscle has a limited enzymatic ability to phosphorylate the RLC they display no potentiation; accordingly, the presence of basal RLC phosphorylation in the slow twitch muscle phenotype may serve a different purpose that may or may not be shared with the fast muscle phenotype. Because the same calcium signals that regulate muscle contraction also activate skMLCK activity it is possible that working skeletal muscle most often operates in the potentiated state produced by myosin RLC phosphorylation. Interesting in this regard is the possibility that skMLCK activity and thus RLC phosphorylation may be sensitive to hormonal influences, a signalling pathway linking system and muscle physiology. Accordingly, the goals of this application are to examine how hormones such as estrogen may influence myosin RLC phosphorylation (and thus potentiation) of mouse fast twitch skeletal muscle (as suggested by Lai et al. 2016) and if this influence involves skMLCK signalling. Another way we will study the system physiology-muscle physiology link is by examining how myosin RLC phosphorylation modulates muscle metabolic rate and heat production, i.e. thermogenesis. The putative ability of myosin RLC phosphorylation to regulate muscle thermogenesis (McNamara et al. 2015) may influence both resting and shivering thermogenesis. A key feature of all of the experiments is the use of skMLCK “knockout” mice from our colony to provide a robust negative control condition that is simply not feasible with wildtype mice. Thus, we will be able to critically examine how estrogen effects muscle function in the presence and/or absence of myosin RLC phosphorylation. We will also be able to assess the influence of environmental interventions such as diet and cold on resting and shivering thermogenesis, respectively, in mice with and without myosin RLC phosphorylation in their skeletal muscles. These studies will thus examine pathways regulating myosin RLC phosphorylation and how, in turn, this molecular mechanism may regulate muscle metabolism.

我的研究计划的长期目标是进一步了解肌球蛋白通过磷酸化的翻译后修饰如何调节骨骼肌的收缩功能。在哺乳动物横纹肌中，骨骼肌球蛋白轻链激酶(SkMLCK)催化肌球蛋白调节轻链(RLC)上的丝氨酸残基从三磷酸腺苷(即三磷酸腺苷)向丝氨酸残基的转移。这一反应受钙和钙调蛋白信号级联的调节，在收缩过程中被激活。反过来，skMLCK催化的肌球蛋白RLC的磷酸化增加了收缩蛋白的钙敏感性，从而增加了次最大力，并产生了众所周知的“增强”。在各种啮齿动物快速抽动骨骼肌模型中，已经证明了收缩诱导的RLC磷酸化和增强之间的强烈关联。相比之下，尽管啮齿动物慢抽动肌肉对RLC的磷酸化能力有限，但它们没有表现出增强作用；因此，在慢抽动肌肉表型中存在基础RLC磷酸化可能起到不同的作用，这可能与快速肌肉表型相同，也可能不同。因为调节肌肉收缩的同样的钙信号也激活了skMLCK的活性，所以工作的骨骼肌最可能在肌球蛋白RLC磷酸化产生的增强状态下工作。在这方面，有趣的是，SkMLCK活性和RLC磷酸化可能对激素影响敏感，这是连接系统和肌肉生理学的信号通路。因此，这项应用的目标是研究雌激素等激素如何影响小鼠快速抽动骨骼肌的肌球蛋白RLC磷酸化(从而增强)(由Lai等人建议)。2016)以及这种影响是否涉及SkMLCK信令。我们将研究系统生理学-肌肉生理学联系的另一种方式是通过研究肌球蛋白RLC磷酸化如何调节肌肉代谢率和产热，即产热。肌球蛋白RLC磷酸化调节肌肉产热的假定能力(McNamara等人)。2015年)可能同时影响静止和颤抖的生热作用。所有实验的一个关键特征是使用我们群体中的skMLCK“敲除”小鼠来提供一个强大的阴性对照条件，这在野生型小鼠中是不可行的。因此，我们将能够关键地研究在存在和/或不存在肌球蛋白RLC磷酸化的情况下，雌激素如何影响肌肉功能。我们还将能够评估环境干预，如饮食和寒冷，分别对骨骼肌肌球蛋白RLC磷酸化和不肌球蛋白RLC磷酸化的小鼠的休息和颤抖产热的影响。因此，这些研究将研究调节肌球蛋白RLC磷酸化的途径，以及这一分子机制如何反过来调节肌肉代谢。