Essers, M. | bioRxiv Science

bioRxiv2025

Biochemical assessment of α-α-subunit interactions of Nav1.5 in a heterologous expression system

Heterologous overexpression of any protein, and especially of the large transmembrane channel Nav1.5, could be associated with the insufficiency of endoplasmic reticulum folding machinery, hence leading to aspecific protein aggregation indistinguishable from the genuine --subunit interactions. In this study, we show that the interactions between heterologous Nav1.5 proteins depend on nascent N-linked glycosylation, are supported by non-native intermolecular disulfide bonds, and are likely predisposed to hydrophobic "stickiness". Particularly, we show strong interactions between the full-length Nav1.5 and its truncated peptides: N-terminal domain, all four transmembrane domains, as well as the intracellular linker between domains I and II. Taken together, we conclude that the heterologous expression system is not optimal for the identification of --subunit interaction sites of Nav1.5, and this question needs to be further addressed in the native tissues. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/679760v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@b29b7dorg.highwire.dtl.DTLVardef@1fe5909org.highwire.dtl.DTLVardef@1877990org.highwire.dtl.DTLVardef@13e04b3_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2022

Role of 14-3-3 proteins in human cardiac sodium channel Nav1.5 regulation

Background14-3-3 proteins are ubiquitous proteins that play a role in cardiac physiology (e.g., metabolism, development, and cell cycle). Furthermore, 14-3-3 proteins were proposed to regulate the electrical function of the heart by interacting with several cardiac ion channels, including the voltage-gated sodium channel Nav1.5. Given the many cardiac arrhythmias associated with Nav1.5 dysfunction, understanding its regulation by the protein partners is crucial. AimsIn this study, we aimed to investigate the role of 14-3-3 proteins in the regulation of the human cardiac sodium channel Nav1.5. Methods and ResultsAmongst the seven 14-3-3 isoforms, only 14-3-3{eta} (encoded by YWHAH gene) weakly co-immunoprecipitated with Nav1.5 when heterologously co-expressed in tsA201 cells. Total and cell surface expression of Nav1.5 was however not modified by 14-3-3{eta} overexpression or inhibition with difopein, and 14-3-3{eta} did not affect physical interaction between Nav1.5 - subunits. The current-voltage relationship and the amplitude of Nav1.5-mediated sodium peak current density were also not changed. ConclusionsOur findings illustrate that the direct implication of 14-3-3 proteins in regulating Nav1.5 is not evident in a transformed human kidney cell line tsA201. SummaryThis work shows that only 14-3-3{eta}, exhibits weak/transient interaction with Nav1.5, and does not modify its total protein expression, plasmalemmal trafficking, and basal biophysical properties of the whole-cell current. Furthermore, inhibition of endogenous 14-3-3/ligand interactions with difopein does not affect the dimerization of Nav1.5. Therefore, 14-3-3 proteins are suggested to be dispensable for the Nav1.5 regulation in a heterologous expression system.

biophysics↗