Activation of skeletal muscle is controlled by a dual-filament mechano-sensing mechanism.
Activation of skeletal muscle is controlled by a dual-filament mechano-sensing mechanism.
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DOI：
10.1073/pnas.2302837120
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发表时间：
2023-05-30
影响因子：
11.1
通讯作者：
Fusi, Luca
中科院分区：
文献类型：
--
作者：
Brunello, Elisabetta;Marcucci, Lorenzo;Irving, Malcolm;Fusi, Luca
骨骼肌的收缩是由钙与肌钙蛋白结合后细丝中的调节性结构变化触发的。粗肌丝的结构变化控制肌球蛋白马达与肌动蛋白相互作用的可用性以及收缩的强度和速度。在这里，我们阐明了薄和厚丝之间的耦合调节机制，从哺乳动物骨骼肌的脱膜纤维在近生理条件下，无论是在稳定状态下，并在毫秒级的时间尺度钙跳。我们表明，骨骼肌的生理激活取决于两个正反馈循环，涉及粗肌丝的机械传感和细肌丝的肌球蛋白传感。电刺激后骨骼肌的快速激活取决于两种细丝的协调激活。骨骼肌的收缩是由细胞内钙离子浓度的瞬时升高引发的，导致含肌动蛋白的细丝的结构变化，从而允许来自粗细丝的肌球蛋白马达结合。大多数肌球蛋白马达在静止的肌肉中不能与肌动蛋白结合，因为它们被折叠在粗的肌丝骨架上。折叠马达的释放是由粗丝应力触发的，这意味着粗丝中存在正反馈回路。然而，目前还不清楚细和粗丝激活机制是如何协调的，部分原因是大多数以前的研究细丝调节是在低温下进行的，其中粗丝机制被抑制。在这里，我们使用探针的肌钙蛋白在薄的细丝和肌球蛋白在厚的细丝，以监测在近生理条件下的激活状态的细丝。我们的特点，这些激活状态都在稳定状态下，使用传统的滴定与钙缓冲液，并在激活过程中的生理时间尺度上，使用钙跳跃产生的笼中钙的光解。结果揭示了三种激活状态的细丝在完整的肌细胞的丝晶格，类似于那些先前提出的研究分离的蛋白质。我们描述了这些状态之间与粗纤维机械传感相关的转变速率，并展示了基于细纤维和粗纤维的机制如何通过两个正反馈循环耦合，从而打开两条纤维以实现骨骼肌的快速协同激活。
Contraction of skeletal muscle is triggered by regulatory structural changes in the thin filaments following calcium binding to troponin. Structural changes in the thick filaments control the availability of myosin motors for actin interaction and the strength and speed of contraction. Here, we elucidate the coupling between thin and thick filament regulatory mechanisms in demembranated fibers from mammalian skeletal muscle in near-physiological conditions, both in the steady state and on the millisecond timescale following a calcium jump. We show that physiological activation of skeletal muscle depends on two positive feedback loops, involving mechano-sensing by the thick filament and myosin-sensing by the thin filament. The rapid activation of skeletal muscle following electrical stimulation depends on the coordinated activation of both filaments. Contraction of skeletal muscle is triggered by a transient rise in intracellular calcium concentration leading to a structural change in the actin-containing thin filaments that allows binding of myosin motors from the thick filaments. Most myosin motors are unavailable for actin binding in resting muscle because they are folded back against the thick filament backbone. Release of the folded motors is triggered by thick filament stress, implying a positive feedback loop in the thick filaments. However, it was unclear how thin and thick filament activation mechanisms are coordinated, partly because most previous studies of the thin filament regulation were conducted at low temperatures where the thick filament mechanisms are inhibited. Here, we use probes on both troponin in the thin filaments and myosin in the thick filaments to monitor the activation states of both filaments in near-physiological conditions. We characterize those activation states both in the steady state, using conventional titrations with calcium buffers, and during activation on the physiological timescale, using calcium jumps produced by photolysis of caged calcium. The results reveal three activation states of the thin filament in the intact filament lattice of a muscle cell that are analogous to those proposed previously from studies on isolated proteins. We characterize the rates of the transitions between these states in relation to thick filament mechano-sensing and show how thin- and thick-filament-based mechanisms are coupled by two positive feedback loops that switch on both filaments to achieve rapid cooperative activation of skeletal muscle.
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DOI：
10.1085/jgp.202012713
发表时间：
2021-03-01
期刊：
The Journal of general physiology
影响因子：
--
作者：
Caremani M;Fusi L;Linari M;Reconditi M;Piazzesi G;Irving TC;Narayanan T;Irving M;Lombardi V;Brunello E
通讯作者：
Brunello E
DOI：
10.1016/j.bbrc.2021.03.010
发表时间：
2021-04-30
影响因子：
3.1
作者：
Lehman W;Pavadai E;Rynkiewicz MJ
通讯作者：
Rynkiewicz MJ
影响因子：
16.6
作者：
Fusi, L.;Brunello, E.;Yan, Z.;Irving, M.
通讯作者：
Irving, M.
DOI：
10.1073/pnas.1018330108
发表时间：
2011-04-26
影响因子：
11.1
作者：
Reconditi, Massimo;Brunello, Elisabetta;Irving, Malcolm
通讯作者：
Irving, Malcolm
影响因子：
3.4
作者：
Fusi L;Huang Z;Irving M
通讯作者：
Irving M