Expanding the Pathogenic Mechanisms of Calmodulinopathies

钙调素(CaM)是一种普遍存在的钙感受器，对免疫系统、心脏和大脑功能至关重要。突变 在CaM内，会导致一系列被称为钙调蛋白病的疾病。携带这些CaM突变的患者 患有危及生命的心律失常，通常伴有神经发育迟缓或 其他神经功能障碍。虽然CAM有许多潜在的目标，但这些目标可能会在 钙调素疾病、电压门控钙通道(VGCC)是可能的致病因素。为 CaV1-2通道，已知CaM与通道的羧基-尾巴预关联。在结合钙离子时，这是 常驻CaM启动两种重要的反馈调节形式之一；依赖于钙/CaM的失活 (CDI)或钙/钙调素依赖性促进(CDF)。这些形式的通道调节中的每一种都可以独立地 由CaM的单叶驱动，CaV1.2、CaV1.3和CaV2.1分别受到钙离子与钙离子结合的强烈调制 凸轮的C叶。由于到目前为止，大多数钙调蛋白病变突变都影响了CaM C叶，因此 叶特异性调节暗示钙调蛋白病变突变对这三个因子的调节有很大影响。 频道。事实上，我们之前已经证明，钙调蛋白病变突变能够破坏 CaV1.2通道的CDI，导致患者6，7出现长QT表型。然而，CaM的作用 除了CaV1.2之外，VGCC上的突变还没有被阐明，也没有潜在的机制 探讨了钙调蛋白病患者的神经学表型。由于CaV1-2通道在 神经元兴奋性、兴奋-转录偶联和神经传递，我们认为它们很可能是 钙调素疾病的神经发病机制的贡献。因此，我们将进行一项生物物理研究 钙调素病突变对CaV1-2通道家族的影响以及评估这些影响 神经功能的突变。特别是，我们假设了改变钙结合的CaM突变 蛋白的C叶减少CaV1.2和CaV1.3的CDI，扰乱CaV2.1的CDF。要评估 这些突变对功能的影响，我们将从钙调蛋白病患者中产生诱导多能干细胞来源的神经元(IPSC-神经元)，并阐明与神经学相关的细胞表型。 钙调素病患者的缺陷。因此，我们将进行首批研究之一，旨在了解 心脏外钙调素病基因突变的影响，扩大了我们对致病机理的认识 这种疾病背后的机制。

Calmodulin (CaM) is a ubiquitous calcium sensor, vital to immune system, heart and brain function. Mutations within CaM result in a set of disorders known as calmodulinopathies. Patients harboring these CaM mutations suffer from life-threatening cardiac arrhythmias, which are often accompanied by neurodevelopmental delay or other neurological dysfunction. While CaM has numerous potential targets which may be altered in calmodulinopathies, voltage gated calcium channels (VGCCs) stand out as likely pathogenic elements. For CaV1-2 channels, CaM is known to preassociate with the carboxy-tail of the channel. Upon binding Ca2+, this resident CaM initiates either of two important forms of feedback regulation; Ca2+/CaM dependent inactivation (CDI) or Ca2+/CaM dependent facilitation (CDF). Each of these forms of channel regulation can be independently driven by a single lobe of CaM, with CaV1.2, CaV1.3 and CaV2.1 each strongly modulated by Ca2+ binding to the C-lobe of CaM. As the majority of calmodulinopathy mutations have thus-far impacted the CaM C-lobe, this lobe-specific regulation implies a large impact of calmodulinopathy mutations on the regulation of these three channels. In fact, we have previously demonstrated that calmodulinopathy mutations are capable of disrupting the CDI of CaV1.2 channels, resulting in the long-QT phenotype seen in patients6,7. However, the effect of CaM mutations on VGCCs other than CaV1.2 has yet to be elucidated, nor have the mechanisms underlying the neurological phenotypes of calmodulinopathy patients been explored. As CaV1-2 channels play critical roles in neuronal excitability, excitation-transcription coupling, and neurotransmission, we propose that they are likely contributors to the neuropathogenesis of calmodulinopathies. We will therefore undertake a biophysical study of the impact of calmodulinopathy mutations across the CaV1-2 channel family and evaluate the impact of these mutations on neuronal function. In particular, we hypothesize that CaM mutations which alter the Ca2+ binding to the C-lobe of the protein will decrease CDI in CaV1.2 and CaV1.3, and disrupt CDF in CaV2.1. To evaluate the functional impact of these mutations, we will generate induced pluripotent stem cell derived neurons (iPSC-neurons) from calmodulinopathy patients, and elucidate a cellular phenotype correlating with the neurological deficits of calmodulinopathy patients. Thus, we will undertake one of the first studies aimed at understanding the impact of calmodulinopathy mutations outside the heart, expanding our understanding of the pathogenic mechanisms underlying this disorder.