Book of Abstracts - New Frontiers 2022

Abstracts of poster presentations

MiRP2 RESCUES LONG QT SYNDROME TYPE 5

S. Déri 1 , T. Hartai 1 , L. Virág 1 , N. Jost 1 , A. J. Labro 2,3 , A. Varró 1 , I. Baczkó 1 , S. Nattel 4 , B. Ördög 1 1 University of Szeged, Department of Pharmacology and Pharmacotherapy, Szeged, Hungary; 2 University of Antwerp, Department of Biomedical Sciences, Antwerp, Belgium; 3 University of Ghent, Department of Basic Medical Sciences, Ghent, Belgium; 4 Université de Montréal, Montreal Heart Institute, Department of Medicine, Montréal, Canada Long QT Syndrome (LQT) is a disorder characterized by delayed cardiac repolarization resulting in the prolongation of the QT interval. LQT5 is caused by loss of function mutations in the KCNE1 gene encoding minK, a regulatory subunit of a voltage-gated ion channel which is conducting the slow component of the cardiac delayed rectifier potassium current (IKs). The minK-related peptides (MiRPs), also encoded by members of the KCNE gene family, are expressed in cardiomyocytes and can also modulate the function of IKs channels in vitro. In this study, we aimed to investigate the possible effect of MiRP2, encoded by the KCNE3 gene, on the development of the LQT5 phenotype. Plasmid constructs carrying cDNAs of KvLQT1 the pore forming subunit of IKs, WT-minK, LQT5-minK variant (G52R-minK) and MiRP2 were generated by standard molecular cloning techniques. These plasmid constructs were co-expressed in different combinations in CHO cells. Whole cell currents were characterized by patch clamp technique. The NanoBiT protein:protein interaction assay was applied to explore whether MiRP2 and minK are represented in a distinct ion channel population or they co-assemble in the same ion channel complex. Mean current densities were similar in group 1 (KvLQT1+WT-minK) [74.9 pA/pF, 95% CI (54.7-95.2), n=22] and group 2 (KvLQT1+WT-minK+MiRP2) [62.33 pA/pF, 95% CI (48.2-76.5), n=22], while average current density was significantly lower in group 3 (KvLQT1+WT-minK+G52R-minK) [31.7 pA/pF, 95% CI (23.8-39.5), n=29] compared to the group 1 and 2. However, the mean current density in the presence of MiRP2 was significantly increased in group 4 (KvLQT1+WT-minK+G52R-minK+MiRP2) [54.3 pA/pF, 95% CI (38.2-70.5), n=27] compared to the group 3. Varying amount of MiRP2 was co-expressed with KvLQT1 and minK for the NanoBiT experiments. Average relative luminescence (RLU) was 194 in group 1 (KvLQT1:minK:MiRP2, cDNA ratio 1:2:0) which was similar to group 2 (1:2:1) (129.3 RLU). However, mean RLU was significantly lower in group 3 (1:2:2) (96.7 RLU, p=0.0085) compared to the group 1. We conclude that MiRP2 has a rescue effect on the LQT5-minK variant which suppresses the IKs channel in vitro. Furthermore, MiRP2 is probably able to replace minK within the macromolecular complex of the IKs ion channel, therefore, MiRP2 possibly modulate the development of the LQT5 phenotype in patients.

Keywords: long QT syndrome type 5, slow component of the cardiac delayed rectifier potassium channel, minK- related peptide 2, NanoLuc® Binary Technology

Funding: Supported by the National Research, Development and Innovation Office (NKFIH -K 128851).

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