Calsequestrin 与 RyR2 簇共定位使心室肌细胞钙波得以传播
Calsequestrin localization at RyR2 clusters enables calcium wave propagation in ventricular myocytes
三维计算模型显示，calsequestrin2（CASQ2）与 RyR2 簇共定位是心室肌细胞钙波稳定传播的必要条件。研究团队构建了亚微米分辨率的小鼠心室肌细胞三维模型，在 CASQ2 按实验观察集中于释放位点的生理设定下，钙波以与实验范围相符的速度可靠传播；而在总 CASQ2 不变、仅将其均匀分布于肌浆网时，波前停滞。结果提示 CASQ2–RyR2 共定位是有效钙波传播的关键结构要求，解释了钙信号在 1–2 μm 的 Z 盘间距上如何克服胞质缓冲与扩散衰减以及释放位点肌浆网钙库耗竭的限制。
来源：PLOS Computational Biology · journals.plos.org
by David Conesa, Blas Echebarria, Leif Hove-Madsen, Yohannes Shiferaw, Enrique Alvarez-Lacalle
Intracellular calcium waves in cardiac myocytes propagate through a fire-diffuse-fire mechanism in which calcium released from one RyR2 cluster diffuses to neighboring clusters and triggers their activation. Yet propagation faces a fundamental physical difficulty: the calcium signal must cross distances of 1–2 μm between Z-planes while being attenuated by cytosolic buffering and diffusion, and at the same time the release site depletes its local sarcoplasmic reticulum calcium store. How waves propagate efficiently despite these constraints has remained unclear. We developed a three-dimensional computational model of mouse ventricular myocytes at submicrometer resolution to address this question. Our central finding is that co-localization of calsequestrin2 (CASQ2) with RyR2 clusters is required for robust wave propagation. In a physiological model, where CASQ2 is concentrated at release sites as observed experimentally, calcium waves propagate reliably across the cell with velocities that match the experimental range. In contrast, when CASQ2 is distributed uniformly throughout the sarcoplasmic reticulum, keeping total CASQ2 unchanged, the wavefront stalls. These results identify CASQ2–RyR2 co-localization as a key structural requirement for effective calcium wave propagation in ventricular myocytes.