Reduced O-GlcNAcylation diminishes cardiomyocyte Ca2+ dependent facilitation and frequency dependent acceleration of relaxation
Reduced O-GlcNAcylation diminishes cardiomyocyte Ca2+ dependent facilitation and frequency dependent acceleration of relaxation
复制标题
减少的 O-GlcNAc 化会减少心肌细胞 Ca2 依赖性促进和频率依赖性松弛加速
DOI：
10.1016/j.yjmcc.2023.04.007
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发表时间：
2023
影响因子：
5
通讯作者：
Bennett, Eric S.
中科院分区：
文献类型：
--
作者：
Ednie, Andrew R.;Paul-Onyia, Chiagozie D.;Bennett, Eric S.
当去极化频率增加时，Ca2+依赖性促进（CDF）和频率依赖性弛豫加速（FDAR）是增强心肌细胞Ca2+通道功能和增加Ca2+释放事件后Ca2+隔离率的调节机制。CDF和FDAR可能进化为在心率增加时维持EC耦合。Ca2+/钙调素依赖性激酶II （CaMKII）对两者都是必不可少的；然而，其机制仍有待完全阐明。CaMKII活性可以通过翻译后修饰调节，但这些修饰是否以及如何影响CDF和FDAR尚不清楚。细胞内o -连接糖基化（o - glcnac酰化）是一种翻译后修饰，作为信号分子和代谢传感器。在高血糖状态下，CaMKII被证明是o - glcn酰化导致病理活性。在这里，我们试图研究o- glcn酰化是否通过在伪生理环境下调节CaMKII活性来影响CDF和FDAR。使用电压钳和Ca2+光度法，我们发现心肌细胞CDF和FDAR在o - glcn酰化减少的条件下显着减少。免疫印迹显示，当o - glcnac酰化被抑制时，CaMKIIδ和钙调素的表达增加，但CaMKIIδ和肌肉细胞特异性CaMKIIβ亚型的自磷酸化减少了75%或更多。我们还表明，负责o - glcn酰化（OGT）的酶可能定位于双间隙和/或心脏肌浆网，并以Ca2+依赖的方式被钙调蛋白沉淀。这些发现将对我们理解CaMKII和OGT如何在正常生理环境下以及在CaMKII和OGT可能异常调节的疾病状态下相互作用影响心肌细胞EC偶联具有重要意义。
Ca2+dependent facilitation (CDF) and frequency dependent acceleration of relaxation (FDAR) are regulatory mechanisms that potentiate cardiomyocyte Ca2+channel function and increase the rate of Ca2+sequestration following a Ca2+-release event, respectively, when depolarization frequency increases. CDF and FDAR likely evolved to maintain EC coupling at increased heart rates. Ca2+/calmodulin-dependent kinase II (CaMKII) was shown to be indispensable to both; however, the mechanisms remain to be completely elucidated. CaMKII activity can be modulated by post-translational modifications but if and how these modifications impact CDF and FDAR is unknown. Intracellular O-linked glycosylation (O-GlcNAcylation) is a post-translational modification that acts as a signaling molecule and metabolic sensor. In hyperglycemic conditions, CaMKII was shown to be O-GlcNAcylated resulting in pathologic activity. Here we sought to investigate whether O-GlcNAcylation impacts CDF and FDAR through modulation of CaMKII activity in a pseudo-physiologic setting. Using voltage-clamp and Ca2+photometry we show that cardiomyocyte CDF and FDAR are significantly diminished in conditions of reduced O-GlcNAcylation. Immunoblot showed that CaMKIIδ and calmodulin expression are increased but the autophosphorylation of CaMKIIδ and the muscle cell-specific CaMKIIβ isoform are reduced by 75% or more when O-GlcNAcylation is inhibited. We also show that the enzyme responsible for O-GlcNAcylation (OGT) can likely be localized in the dyad space and/or at the cardiac sarcoplasmic reticulum and is precipitated by calmodulin in a Ca2+dependent manner. These findings will have important implications for our understanding of how CaMKII and OGT interact to impact cardiomyocyte EC coupling in normal physiologic settings as well as in disease states where CaMKII and OGT may be aberrantly regulated.