Enteric NeuroScience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota.
Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic , Rochester, Minnesota.
Am J Physiol Gastrointest Liver Physiol. 2018 Apr 1;314(4):G494-G503. doi: 10.1152/ajpgi.00016.2017. Epub 2017 Nov 22.
The SCN5A-encoded voltage-gated mechanosensitive Na channel Na1.5 is expressed in human gastrointestinal smooth muscle cells and interstitial cells of Cajal. Na1.5 contributes to smooth muscle electrical slow waves and mechanical sensitivity. In predominantly Caucasian irritable bowel syndrome (IBS) patient cohorts, 2-3% of patients have SCN5A missense mutations that alter Na1.5 function and may contribute to IBS pathophysiology. In this study we examined a racially and ethnically diverse cohort of IBS patients for SCN5A missense mutations, compared them with IBS-negative controls, and determined the resulting Na1.5 voltage-dependent and mechanosensitive properties. All SCN5A exons were sequenced from somatic DNA of 252 Rome III IBS patients with diverse ethnic and racial backgrounds. Missense mutations were introduced into wild-type SCN5A by site-directed mutagenesis and cotransfected with green fluorescent protein into HEK-293 cells. Na1.5 voltage-dependent and mechanosensitive functions were studied by whole cell electrophysiology with and without shear force. Five of 252 (2.0%) IBS patients had six rare SCN5A mutations that were absent in 377 IBS-negative controls. Six of six (100%) IBS-associated Na1.5 mutations had voltage-dependent gating abnormalities [current density reduction (R225W, R433C, R986Q, and F1293S) and altered voltage dependence (R225W, R433C, R986Q, G1037V, and F1293S)], and at least one kinetic parameter was altered in all mutations. Four of six (67%) IBS-associated SCN5A mutations (R225W, R433C, R986Q, and F1293S) resulted in altered Na1.5 mechanosensitivity. In this racially and ethnically diverse cohort of IBS patients, we show that 2% of IBS patients harbor SCN5A mutations that are absent in IBS-negative controls and result in Na1.5 channels with abnormal voltage-dependent and mechanosensitive function. NEW & NOTEWORTHY The voltage-gated Na channel Na1.5 contributes to smooth muscle physiology and electrical slow waves. In a racially and ethnically mixed irritable bowel syndrome cohort, 2% had mutations in the Na1.5 gene SCN5A. These mutations were absent in irritable bowel syndrome-negative controls. Most mutant Na1.5 channels were loss of function in voltage dependence or mechanosensitivity.
SCN5A 编码的电压门控机械敏感钠通道 Na1.5 在人类胃肠道平滑肌细胞和 Cajal 间质细胞中表达。Na1.5 有助于平滑肌的电慢波和机械敏感性。在以白种人为主的肠易激综合征 (IBS) 患者队列中，2-3%的患者存在改变 Na1.5 功能的 SCN5A 错义突变，可能导致 IBS 病理生理学改变。在这项研究中，我们检查了一个具有多种种族和民族背景的 IBS 患者的 SCN5A 错义突变，将其与 IBS 阴性对照进行比较，并确定了由此产生的 Na1.5 电压依赖性和机械敏感性特性。从 252 名具有不同种族和民族背景的罗马 III IBS 患者的体细胞 DNA 中对所有 SCN5A 外显子进行测序。通过定点诱变将错义突变引入野生型 SCN5A 中，并与绿色荧光蛋白共转染至 HEK-293 细胞中。通过全细胞膜片钳技术在有和没有切应力的情况下研究 Na1.5 的电压依赖性和机械敏感性功能。在 252 名 IBS 患者中，有 5 名（2.0%）患者有 6 种罕见的 SCN5A 突变，而在 377 名 IBS 阴性对照中不存在。所有 6 种（100%）与 IBS 相关的 Na1.5 突变均存在电压依赖性门控异常[电流密度降低（R225W、R433C、R986Q 和 F1293S）和电压依赖性改变（R225W、R433C、R986Q、G1037V 和 F1293S）]，并且所有突变至少有一个动力学参数发生改变。与 IBS 相关的 SCN5A 突变中的 4 种（67%）（R225W、R433C、R986Q 和 F1293S）导致 Na1.5 机械敏感性改变。在这个种族和民族多样化的 IBS 患者队列中，我们表明 2%的 IBS 患者存在 SCN5A 突变，这些突变在 IBS 阴性对照中不存在，导致 Na1.5 通道具有异常的电压依赖性和机械敏感性功能。在一个种族和民族多样化的肠易激综合征队列中，2%的患者的 Na1.5 基因 SCN5A 发生突变。这些突变在肠易激综合征阴性对照中不存在。大多数突变型 Na1.5 通道在电压依赖性或机械敏感性方面表现为功能丧失。
