Scott Brent, Greenberg Lina, Squarci Caterina, Campbell Kenneth S, Greenberg Michael J
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA.
Division of Cardiovascular Medicine, University of Kentucky, Lexington, KY, 40506, USA.
bioRxiv. 2024 Oct 31:2024.10.09.617269. doi: 10.1101/2024.10.09.617269.
Heart failure is a leading cause of death worldwide, and even with current treatments, the 5-year transplant-free survival rate is only ~50-70%. As such, there is a need to develop new treatments for patients that improve survival and quality of life. Recently, there have been efforts to develop small molecules for heart failure that directly target components of the sarcomere, including cardiac myosin. One such molecule, danicamtiv, recently entered phase II clinical trials; however, its mechanism of action and direct effects on myosin's mechanics and kinetics are not well understood. Using optical trapping techniques, stopped flow transient kinetics, and reconstitution assays, we found that danicamtiv reduces the size of cardiac myosin's working stroke, and in contrast to studies in muscle fibers, we found that it does not affect actomyosin detachment kinetics at the level of individual crossbridges. We demonstrate that danicamtiv accelerates actomyosin association kinetics, leading to increased recruitment of myosin crossbridges and subsequent thin filament activation at physiologically-relevant calcium concentrations. Finally, we computationally model how the observed changes in mechanics and kinetics at the level of single crossbridges contribute to increased cardiac contraction and improved diastolic function compared to the related myotrope, omecamtiv mecarbil. Taken together, our results have important implications for the design of new sarcomeric-targeting compounds for heart failure.
心力衰竭是全球主要的死亡原因之一，即使采用目前的治疗方法，无移植的5年生存率也仅约为50%-70%。因此，需要为患者开发新的治疗方法，以提高生存率和生活质量。最近，人们致力于开发针对心力衰竭的小分子药物，这些药物直接靶向肌节的组成部分，包括心肌肌球蛋白。其中一种名为达尼卡替夫的分子最近进入了II期临床试验；然而，其作用机制以及对肌球蛋白力学和动力学的直接影响尚不清楚。我们使用光镊技术、停流瞬态动力学和重组试验发现，达尼卡替夫可减小心肌肌球蛋白工作冲程的大小，并且与在肌纤维中的研究不同，我们发现它在单个横桥水平上不影响肌动球蛋白的解离动力学。我们证明，达尼卡替夫可加速肌动球蛋白的结合动力学，在生理相关的钙浓度下导致肌球蛋白横桥募集增加以及随后的细肌丝激活。最后，我们通过计算模拟了与相关的变力性药物奥美卡替麦卡比相比，在单个横桥水平上观察到的力学和动力学变化如何有助于增强心脏收缩和改善舒张功能。综上所述，我们的结果对设计用于心力衰竭的新型肌节靶向化合物具有重要意义。
