Electrophysiological Characteristics of a SCN5A Voltage Sensors Mutation R1629Q Associated With Brugada Syndrome

Abstract

Brugada syndrome (BrS) is an inherited arrhythmogenic syndrome leading to sudden cardiac death, partially associated with autosomal dominant mutations in SCN5A, which encodes the cardiac sodium channel alpha-subunit (Nav1.5). To date some SCN5A mutations related with BrS have been identified in voltage sensor of Nav1.5. Here, we describe a dominant missense mutation (R1629Q) localized in the fourth segment of domain IV region (DIV-S4) in a Chinese Han family. The mutation was identified by direct sequencing of SCN5A from the proband’s DNA. Co-expression of Wild-type (WT) or R1629Q Nav1.5 channel and hβ1 subunit were achieved in human embryonic kidney cells by transient transfection. Sodium currents were recorded using whole cell patch-clamp protocols. No significant changes between WT and R1629Q currents were observed in current density or steady-state activation. However, hyperpolarized shift of steady–state inactivation curve was identified in cells expressing R1629Q channel (WT: V1/2 = -81.1 ± 1.3 mV, n = 13; R1629Q: V1/2 = -101.7 ± 1.2 mV, n = 18). Moreover, R1629Q channel showed enhanced intermediate inactivation and prolonged recovery time from inactivation. In summary, this study reveals that R1629Q mutation causes a distinct loss-of-function of the channel due to alter its electrophysiological characteristics, and facilitates our understanding of biophysical mechanisms of BrS.

Post-transcriptional regulation of cardiac sodium channel gene SCN5A expression and function by miR-192-5p

“…We recorded sodium current at room temperature using a Multiclamp 700B amplifier (Axon Instruments, Sunnyvale, CA). The patch pipette (tip resistance was 2–3MΩ) was filled with following solutions as described previously [3,38,39]: 20 mM NaCl, 130 mM CsCl, 10 mM HEPES, and 10mMEGTA, pH 7.2 (adjusted with CsOH). The components of bath solution was 70 mM NaCl, 80 mM CsCl, 5.4 mM KCl, 2 mM CaCl 2 , 1mM MgCl 2 , 10 mM HEPES, and 10 mM glucose, pH 7.3 (adjusted with CsOH).…”

Enhanced fast-inactivated state stability of cardiac sodium channels by a novel voltage sensor SCN5A mutation, R1632C, as a cause of atypical Brugada syndrome

“…[20][21][22] In contrast, R1629Q, identified in patients with BrS, resulted in loss of function of I Na with a hyperpolarizing shift in the steady-state inactivation curve, an increased fast inactivation rate, and a delayed recovery from inactivation. 23 However, although Zeng et al 23 insisted that functional abnormality of R1629Q was an enhanced intermediate inactivation, whether fast inactivation is also enhanced should be examined. Intriguingly, R1626H, identified in a patient with AF, exhibited a positive shift in steady-state activation and a negative shift in steadystate inactivation, together with a decreased fast inactivation rate.…”

“…16 Thus, SCN5A mutations in each S4 segment and even those in the same S4 segment may cause diverse functional abnormalities and phenotypic manifestations. 6,8,[17][18][19][20][21][22][23] It has been reported that recovery from fast inactivation of I Na may be associated with immobilized gating charge caused by the slow movement of the S4 segments in domains III and IV, but not in domains I and II, 15 which suggested that recovery from fast inactivation of I Na would be impaired by R1632C mutation.…”

Deep Mutational Scan of a cardiac sodium channel voltage sensor

“…In the literature, 3 gain of function variants have been identified in R1623 or R1626 and 3 loss of function variants in R1629 and R1632 (Table 1). [20][21][22][23]37,38 The three previously-studied partial loss of function BrS1 variants all had low Deep Mutational Scan scores (62, 66, and 69). Two of three previously studied gain of function LQT3 variants had elevated Deep Mutational Scan scores (129 and 144), while a third mild gain of function variant had a near-wildtype score (95).…”

“…We measure the effect of 248 variants in the voltage sensor (S4) segment of transmembrane domain IV, a hotspot region known to harbor multiple disease-associated gain and loss of function variants. [20][21][22][23] We identify 40 putative gain of function and 33 putative loss of function variants, 8/9 of which were validated by patch clamp data.…”