SUDEP and Sids-associated KCNH2 Variants Have Opposing Effects on herg1np Function
Abstract number :
1.087
Submission category :
1. Basic Mechanisms / 1F. Other
Year :
2024
Submission ID :
775
Source :
www.aesnet.org
Presentation date :
12/7/2024 12:00:00 AM
Published date :
Authors :
Francisco Sanchez-Conde, BS – University of Michigan
Olivia Stack, BS – University of Michigan
Hannah Harmes, S – University of Michigan
Pamela Ruzycki, S – University of Michigan
Abhilasha Jain, MSc – University of Michigan
Eric Jimenez-Vazquez, PhD – University of Michigan
Presenting Author: David Jones, PhD – University of Michigan
Rationale: hERG1NP, encoded by KCNH2, is a polypeptide expressed in the nuclei of developing cardiomyocytes and neurons. KCNH2 variants that map to hERG1NP are linked with both sudden infant death syndrome (SIDS) and sudden unexplained death in epilepsy (SUDEP), but the mechanism(s) by which hERG1NP variants promote sudden death and epilepsy are unknown. We previously demonstrated that hERG1NP nuclear targeting modulates gene expression, leading to reduced potassium current at the cell surface membrane. Here, we measured the impact of two hERG1NP variants associated with sudden death on hERG1NP function, R1047L and Q1068R. R1047L was identified in four distinct cases of SUDEP, whereas Q1068R was identified in a case of SIDS. Both R1047L and Q1068R map to the hERG1NP coiled-coil domain, the only confirmed secondary structure in the hERG1NP polypeptide.
Methods: To determine the basic effects of R1047L and Q1068R on hERG1NP activity we expressed either GFP, hERG1NP-wildtype, hERG1NP-R1047L, or hERG1NP-Q1068R in HEK293 cells. We quantified intracellular trafficking using confocal microscopy and measured surface membrane potassium currents by patch clamp.
Results: Consistent with our previous work, wildtype hERG1NP was targeted almost exclusively to the cell nuclei and it reduced potassium current magnitude at the surface membrane by roughly half, compared to GFP-transfected controls. R1047L abolished both hERG1NP nuclear trafficking as well as modulation of membrane potassium currents. In contrast, Q1068R did not affect nuclear targeting but displayed enhanced the inhibition of potassium current magnitude, compared to wildtype hERG1NP. A third KCNH2 variant, G965A, which does not map to the hERG1NP coiled-coil domain and is not associated with sudden death, did not alter hERG1NP activity.
Conclusions: This work demonstrates that biochemistry of the hERG1NP coiled-coil domain is critically important for normal hERG1NP function. Collectively, these data demonstrate that R1047L and Q1068R have opposing effects on hERG1NP activity. Thus, this work suggests two distinct mechanisms by which hERG1NP variants could alter neuronal function. Follow up work in a more clinically translational experimental paradigm is needed to further outline these potential disease mechanisms.
Funding: American SIDS Institute
University of Michigan Frankel Cardiovascular Center McKay Grant
Basic Mechanisms