Binary architecture of the Nav1.2-β2 signaling complex.

Samir Das,Filip Van Petegem,Frank Bosmans,John Gilchrist

doi:10.7554/elife.10960

Samir Das, Filip Van Petegem + Show 2 more

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https://doi.org/10.7554/elife.10960

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Abstract

To investigate the mechanisms by which β-subunits influence Nav channel function, we solved the crystal structure of the β2 extracellular domain at 1.35Å. We combined these data with known bacterial Nav channel structural insights and novel functional studies to determine the interactions of specific residues in β2 with Nav1.2. We identified a flexible loop formed by (72)Cys and (75)Cys, a unique feature among the four β-subunit isoforms. Moreover, we found that (55)Cys helps to determine the influence of β2 on Nav1.2 toxin susceptibility. Further mutagenesis combined with the use of spider toxins reveals that (55)Cys forms a disulfide bond with (910)Cys in the Nav1.2 domain II pore loop, thereby suggesting a 1:1 stoichiometry. Our results also provide clues as to which disulfide bonds are formed between adjacent Nav1.2 (912/918)Cys residues. The concepts emerging from this work will help to form a model reflecting the β-subunit location in a Nav channel complex.

Highlights

Voltage-gated sodium (Nav) channels are part of membrane-embedded signaling complexes that initiate the rising phase of action potentials, a crucial event in generating and propagating electrical signals throughout the human body (Hille, 2001; Catterall, 2012)
The goal of this study was to explore the interaction of b2 with Nav1.2 and identify anchoring residues in both partners which will help orient functional motifs within their extracellular domains
We identified a flexible loop formed by 72Cys and 75Cys that is a unique feature among b-subunits but with a function that has yet to be elucidated (Figure 1c, Figure 2, and Figure 3)

Summary

Introduction

Voltage-gated sodium (Nav) channels are part of membrane-embedded signaling complexes that initiate the rising phase of action potentials, a crucial event in generating and propagating electrical signals throughout the human body (Hille, 2001; Catterall, 2012). All b-subunits belong to the Ig family, recent atomic resolution information for the b3 and b4 extracellular domain revealed substantial differences in their 3D structure (Gilchrist et al, 2013; Namadurai et al, 2014). Given their distinct features and functional roles, it has become clear that each b-subunit structure should be obtained and assessed separately. Non-covalent interactions underlie b1 and b3 association with Nav channels as well as other members of the voltage-gated ion channel family

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