models of the macromolecular Na1.5-K2.1 complex.

In cardiac cells, the expression of the cardiac voltage-gated Na channel (Na1.5) is reciprocally regulated with the inward rectifying K channel (K2.1). These channels can form macromolecular complexes that pre-assemble early during forward trafficking (transport to the cell membrane). In this study, we present 3D models of Na1.5-K2.1, generated by rigid-body protein-protein docking programs and deep learning-based AlphaFold-Multimer software. Modeling revealed that the two channels could physically interact with each other along the entire transmembrane region. Structural mapping of disease-associated mutations revealed a hotspot at this interface with several trafficking-deficient variants in close proximity. Thus, examining the role of disease-causing variants is important not only in isolated channels but also in the context of macromolecular complexes. These findings may contribute to a better understanding of the life-threatening cardiovascular diseases underlying K2.1 and Na1.5 malfunctions.