Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
Biochem Biophys Res Commun. 2022 Nov 5;628:155-162. doi: 10.1016/j.bbrc.2022.08.069. Epub 2022 Aug 28.
Increased endoplasmic reticulum (ER) stress is strongly associated with the phenotypic switching of vascular smooth muscle cells (VSMCs) in atherosclerosis. Depletion of the ER Ca content is one of the leading causes of increased ER stress in VSMCs. The ryanodine receptor (RyR) is a major Ca release channel in the sarcoplasmic reticulum membrane. Calmodulin (CaM), which binds to RyR (CaM-RyR), stabilizes the closed state of RyR in the resting state in normal cells. Defective CaM-RyR interactions can cause abnormal Ca leakage through RyR, resulting in decreased Ca content, indicating that defective CaM-RyR interactions may be a cause of increased ER stress. Herein, we used a mouse VSMCs to assess whether CaM-RyR plays a pivotal role in VSMCs phenotypic switching, which is caused by ER stress, and whether dantrolene, which enhances the binding affinity of CaM to RyR, affects VSMCs phenotypic switching.
Tunicamycin was used to mimic ER stress in vitro. Tunicamycin-induced ER stress caused CaM to dissociate from the RyR and translocate to the nucleus, which stimulated phenotypic switching through the activation of MEF2 and KLF5. Dantrolene suppressed tunicamycin-induced apoptosis, ER stress (restoring ER Ca content), and phenotypic switching of VSMCs. Suramin, which directly unbinds CaM from RyR, promoted nuclear CaM accumulation with parallel VSMCs phenotypic switching, and dantrolene prevented these effects.
We observed that ER stress causes CaM translocation to the nucleus and drives the phenotypic switching of VSMCs. Thus, restoration of the binding affinity of CaM to RyR may be a therapeutic target for atherosclerosis.
内质网（ER）应激的增加与动脉粥样硬化中血管平滑肌细胞（VSMCs）的表型转换密切相关。ER 中 Ca 含量的耗竭是 VSMCs 中 ER 应激增加的主要原因之一。兰尼碱受体（RyR）是肌浆网膜上的主要 Ca 释放通道。钙调蛋白（CaM）与 RyR（CaM-RyR）结合，在正常细胞的静息状态下稳定 RyR 的关闭状态。CaM-RyR 相互作用的缺陷可导致 RyR 异常 Ca 渗漏，导致 Ca 含量减少，表明 CaM-RyR 相互作用的缺陷可能是 ER 应激增加的原因。在此，我们使用小鼠 VSMCs 来评估 CaM-RyR 是否在由 ER 应激引起的 VSMCs 表型转换中发挥关键作用，以及增强 CaM 与 RyR 结合亲和力的丹曲林是否会影响 VSMCs 表型转换。
使用衣霉素在体外模拟 ER 应激。衣霉素诱导的 ER 应激导致 CaM 与 RyR 解离并转位到细胞核，通过激活 MEF2 和 KLF5 刺激表型转换。丹曲林抑制衣霉素诱导的 VSMCs 凋亡、ER 应激（恢复 ER Ca 含量）和表型转换。直接将 CaM 从 RyR 上解偶联的苏拉明促进细胞核内 CaM 积累，同时平行诱导 VSMCs 表型转换，而丹曲林则阻止了这些作用。
我们观察到 ER 应激导致 CaM 转位到细胞核，并驱动 VSMCs 的表型转换。因此，恢复 CaM 与 RyR 的结合亲和力可能是动脉粥样硬化的治疗靶点。
