Biochemical assessment of α-α-subunit interactions of Na _v 1.5 in a heterologous expression system

Heterologous overexpression of any protein, and especially of the large transmembrane channel Na _v 1.5, could be associated with the insufficiency of endoplasmic reticulum folding machinery, hence leading to aspecific protein aggregation indistinguishable from the genuine α-α-subunit interactions. In this study, we show that the interactions between heterologous Na _v 1.5 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 Na _v 1.5 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 α-α-subunit interaction sites of Na _v 1.5, and this question needs to be further addressed in the native tissues.