Thick-Filament-Based Regulation and the Determinants of Force Generation.

IF 3.9 3区 工程技术 Q2 BIOCHEMISTRY & MOLECULAR BIOLOGY
Vivek P Jani, Weikang Ma
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引用次数: 0

Abstract

Background/Objectives: Thick-filament-based regulation in muscle is generally conceived as processes that modulate the number of myosin heads capable of force generation. It has been generally assumed that biochemical and structural assays of myosin active and inactive states provide equivalent measures of myosin recruitment, but recent studies indicate that this may not always be the case. Here, we studied the steady-state and dynamic mechanical changes in skinned porcine myocardium before and after treatment with omecamtiv mecarbil (OM) or piperine to help decipher how the biochemical and structural states of myosin separately affect contractile force. Methods: Force-Ca2+ relationships were obtained from skinned cardiomyocytes isolated from porcine myocardium before and after exposure to 1 μM OM and 7 μM piperine. Crossbridge kinetics were acquired using a step response stretch activation protocol allowing myosin attachment and detachment rates to be calculated. Results: OM augmented calcium-activated force at submaximal calcium levels that can be attributed to increased thick filament recruitment, increases in calcium sensitivity, an increased duty ratio, and from decelerated crossbridge detachment resulting in slowed crossbridge cycling kinetics. Piperine, in contrast, was able to increase activated force at submaximal calcium levels without appreciably affecting crossbridge cycling kinetics. Conclusions: Our study supports the notion that thick filament activation is primarily a process of myosin recruitment that is not necessarily coupled with the chemo-cycling of crossbridges. These new insights into thick filament activation mechanisms will need to be considered in the design of sarcomere-based therapies for treatment of myopathies.

背景/目的:肌肉中基于粗丝的调节通常被认为是调节能够产生力量的肌球蛋白头数量的过程。一般认为,对肌球蛋白活性和非活性状态的生化和结构测定可提供等效的肌球蛋白招募测量,但最近的研究表明,情况并非总是如此。在此,我们研究了用奥美卡替氨嘧啶(OM)或哌啶处理前后带皮猪心肌的稳态和动态机械变化,以帮助破译肌球蛋白的生化和结构状态如何分别影响收缩力。方法:在暴露于 1 μM OM 和 7 μM 哌啶前后,从猪心肌中分离的带皮心肌细胞获得了肌力-Ca2+关系。使用阶跃响应拉伸激活方案获取交桥动力学,从而计算肌球蛋白的附着和脱落率。结果在亚极限钙水平下,OM 增加了钙激活力,这可归因于粗丝招募增加、钙敏感性增加、占空比增加,以及交桥分离减速导致交桥循环动力学减慢。相比之下,胡椒碱能够增加亚极限钙水平下的活化力,而不会明显影响交桥循环动力学。结论:我们的研究支持这样一种观点,即粗丝活化主要是肌球蛋白的招募过程,并不一定与交叉桥的化学循环相关联。在设计用于治疗肌病的基于肌节的疗法时,需要考虑对粗丝激活机制的这些新认识。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Biomedicines
Biomedicines Biochemistry, Genetics and Molecular Biology-General Biochemistry,Genetics and Molecular Biology
CiteScore
5.20
自引率
8.50%
发文量
2823
审稿时长
8 weeks
期刊介绍: Biomedicines (ISSN 2227-9059; CODEN: BIOMID) is an international, scientific, open access journal on biomedicines published quarterly online by MDPI.
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