Signaling from sarcomere to mitochondria: a new paradigm for optimal muscle performance

肌肉功能允许动物移动，保持姿势，并进行心脏泵血。肌肉活动所需的大部分能量，由一种叫做ATP的小化学物质储存和释放，由细胞的“发电站”线粒体提供。预计这些线粒体和产生肌肉力量的分子机制（肌原纤维）之间存在通信，以便能量生产满足能量需求。然而，迄今为止，尚未收到此类来文的报告。参与该项目的实验室研究人员已经为这种交流提供了证据，他们现在试图了解潜在的分子机制。为了提高非科学家对科学的理解，该项目还将：（1）创建一个本科课程，“音乐和生物学的结构”，这将研究在音乐和生物系统的结构和形式的相似性，（2）进行为期一天的年度研讨会开放给整个大学，音乐/科学双学位学生将（a）发表一个非科学家可以理解的关于他们研究的演讲;和（B）表演一首他们写的由他们的科学研究启发的作品。在横纹肌中，肌肉收缩需要大量的ATP，并且这种ATP主要由线粒体提供。线粒体形成与肌原纤维/SR/T-小管紧密并列的复杂3D网络。然而，线粒体网络与收缩机制的结构协调的机制以及将收缩的能量需求整合到能量产生机制的机制尚不清楚。研究者对C. elegans巨大的肌节蛋白E10 -89（人类的obscurin），提供了新的见解。unc-89突变体蠕虫显示出降低的整个蠕虫运动，并且具有紊乱的肌节和肌浆网（SR）。β-89蛋白定位于肌节M系，并且是具有两个蛋白激酶结构域（PK 1和PK 2）的多结构域蛋白。CRISPR/Cas9用于产生表达具有失活PK 2激酶结构域的正常水平的pk 89的线虫。与所有其他unc-89突变体不同，死亡突变体具有正常的肌节结构、正常的SR组织和正常的全身运动和力产生。令人惊讶的是，PK 2激酶死亡突变体肌肉具有破碎的线粒体，产生更多的ATP，并且它们的线粒体呼吸水平高于野生型。这些结果表明：（1）来自肌节蛋白G40 -89的激酶活性调节线粒体形态和能量学，和（2）与在疾病或衰老中观察到的线粒体断裂和功能障碍不同，这种断裂改善线粒体功能。据推测，β-89作为一个信号平台，以协调肌肉结构和活动与线粒体形态和能量输出，β-89 PK 2磷酸化的关键蛋白在这个信号。为了验证这些假设，研究将：（1）确定线粒体被片段化并在MAPK-89激酶死亡突变体中功能增强的机制，（2）测定肌节-肌球蛋白激酶α-89的表达。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Muscle function allows an animal to move, to maintain posture, and to perform heart pumping. Most of the energy required for muscle activity, stored and released from the small chemical called ATP, is provided by the “powerhouses” of cells, the mitochondria. It is expected that there is communication between these mitochondria and the molecular machinery that produces muscle force, the myofibrils, so that energy production meets energy demand. However, to date, such communication has not been reported. Investigators from the laboratory engaged in this project have provided evidence for this communication, and they now seek to understand the underlying molecular mechanisms. To increase the understanding of science by non-scientists, the project will also: (1) create an undergraduate course, “Structure in Music and Biology”, which will examine similarities in structure and form in music and in biological systems, and (2) conduct an annual day-long symposium open to the entire university, in which music/science double majors will (a) present a talk about their research understandable by non-scientists; and (b) perform a composition that they have written that was inspired by their scientific research.In striated muscle, large amounts of ATP are required for muscle contraction and this ATP is mostly supplied by mitochondria. The mitochondria form a complex 3D network closely apposed to the myofibril/SR/T-tubules. The mechanisms, however, underlying the structural coordination of the mitochondrial network with the contractile machinery, and mechanisms that integrate the energetic demands of contraction to the energy production machinery are unknown. The investigator’s data on the C. elegans giant sarcomeric protein UNC-89 (obscurin in humans), provide novel insight. unc-89 mutant worms show reduced whole worm locomotion and have disorganized sarcomeres and sarcoplasmic reticulum (SR). UNC-89 proteins localize to sarcomeric M-lines, and are multidomain proteins having two protein kinase domains (PK1 and PK2). CRISPR/Cas9 was used to create nematodes that express normal levels of UNC-89 with an inactive PK2 kinase domain. Unlike all other unc-89 mutants, UNC-89 PK2 kinase dead mutants have normal sarcomere structure, normal SR organization, and normal whole-body locomotion and force production. Surprisingly, UNC-89 PK2 kinase dead mutant muscle have fragmented mitochondria, produce more ATP, and their mitochondria respire at higher than wild type levels. These results suggest: (1) the kinase activity from sarcomeric protein UNC-89 modulates mitochondrial morphology and energetics, and (2) unlike mitochondrial fragmentation and dysfunction observed in disease or aging, this fragmentation improves mitochondrial function. It is hypothesized that UNC-89 serves as a signaling platform to coordinate muscle structure and activity with mitochondrial morphology and energy output, and that UNC-89 PK2 phosphorylates a key protein in this signaling. To test these hypotheses, the research will: (1) Determine the mechanism(s) by which mitochondria are fragmented and are functionally enhanced in UNC-89 kinase dead mutants, and (2) Determine the UNC-89 protein kinase sarcomere-to-mitochondria signaling network.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.