Zhang Chenyang, Shao Dongxue, Zheng Xi, Hao Liying
Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China.
J Physiol Biochem. 2025 Feb;81(1):185-197. doi: 10.1007/s13105-024-01064-5. Epub 2024 Dec 19.
Mutations in the CALM1-3 genes, which encode calmodulin (CaM), have been reported in clinical cases of long QT syndrome (LQTS). Specifically, the CaM mutant E141G (CaM) in the variant CALM1 gene has been identified as a causative factor in LQTS. This mutation disrupts the normal Ca-dependent inactivation (CDI) function of Ca1.2 channels. However, it is still unclear how CaM interferes with the regulatory role of wild-type (WT) CaM on Ca1.2 channels and leads to abnormal CDI. A CaM molecule contains two lobes with similar structure, the N-lobe and the C-lobe. In this study, a CaM-truncated C-lobe mutant E141G (C-lobe) was engineered to exclude the impact of the unmutated N-lobe. Our findings revealed that at low Ca concentration ([Ca]), the binding of C-lobe to the preIQ, IQ and N-terminus (NT) of Ca1.2 channels has higher binding capacity (B: 0.17, 0.22, 0.13) compared with those of WT C-lobe (B: 0.04, 0.14, 0.11) in GST pull-down assay. With an increase in [Ca], the Ca-dependency for C-lobe binding to Ca1.2 channels was impaired. Moreover, C-lobe induced the relative channel activity to 240.58 ± 51.37% at resting [Ca], but it was unable to diminish the channel activity at high [Ca] even in the presence of WT N-lobe, which may be responsible for the abnormal CDI of Ca1.2 channels affected by the LQTS-related CaM mutation. Our research provides preliminary insights into the mechanism by which the CaM mutation interferes with Ca1.2 channels function through its C-lobe.
在长QT综合征（LQTS）的临床病例中，已报道了编码钙调蛋白（CaM）的CALM1 - 3基因发生突变。具体而言，变体CALM1基因中的CaM突变体E141G（CaM）已被确定为LQTS的一个致病因素。这种突变破坏了Ca1.2通道正常的钙依赖性失活（CDI）功能。然而，目前尚不清楚CaM如何干扰野生型（WT）CaM对Ca1.2通道的调节作用并导致异常的CDI。一个CaM分子包含两个结构相似的叶，即N叶和C叶。在本研究中，构建了一个CaM截短的C叶突变体E141G（C叶），以排除未突变的N叶的影响。我们的研究结果表明，在低钙浓度（[Ca]）下，与GST下拉实验中WT C叶（结合量：0.04、0.14、0.11）相比，C叶与Ca1.2通道的preIQ、IQ和N端（NT）的结合具有更高的结合能力（结合量：0.17、0.22、0.13）。随着[Ca]的增加，C叶与Ca1.2通道结合的钙依赖性受损。此外，在静息[Ca]时，C叶诱导相对通道活性达到240.58±51.37%，但即使在存在WT N叶的情况下，它在高[Ca]时也无法降低通道活性，这可能是受LQTS相关CaM突变影响的Ca1.2通道异常CDI的原因。我们的研究为CaM突变通过其C叶干扰Ca1.2通道功能的机制提供了初步见解。
