Crystal structure and molecular imaging of the Nav channel β3 subunit indicates a trimeric assembly.
J Biol Chem
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Namadurai, S., Balasuriya, D., Rajappa, R., Wiemhöfer, M., Stott, K., Klingauf, J., Edwardson, M., et al. (2014). Crystal structure and molecular imaging of the Nav channel β3 subunit indicates a trimeric assembly.. J Biol Chem, 289 (15), 10797-10811. https://doi.org/10.1074/jbc.M113.527994
The vertebrate sodium (Nav) channel is composed of an ion-conducting α subunit and associated β subunits. Here, we report the crystal structure of the human β3 subunit immunoglobulin (Ig) domain, a functionally important component of Nav channels in neurons and cardiomyocytes. Surprisingly, we found that the β3 subunit Ig domain assembles as a trimer in the crystal asymmetric unit. Analytical ultracentrifugation confirmed the presence of Ig domain monomers, dimers, and trimers in free solution, and atomic force microscopy imaging also detected full-length β3 subunit monomers, dimers, and trimers. Mutation of a cysteine residue critical for maintaining the trimer interface destabilized both dimers and trimers. Using fluorescence photoactivated localization microscopy, we detected full-length β3 subunit trimers on the plasma membrane of transfected HEK293 cells. We further show that β3 subunits can bind to more than one site on the Nav 1.5 α subunit and induce the formation of α subunit oligomers, including trimers. Our results suggest a new and unexpected role for the β3 subunits in Nav channel cross-linking and provide new structural insights into some pathological Nav channel mutations.
Humans, Immunoglobulins, Microscopy, Atomic Force, Ultracentrifugation, Crystallization, Crystallography, X-Ray, Cloning, Molecular, Binding Sites, Amino Acid Sequence, Protein Conformation, Dimerization, Molecular Sequence Data, HEK293 Cells, NAV1.5 Voltage-Gated Sodium Channel, Voltage-Gated Sodium Channel beta-3 Subunit
Wellcome Trust (089125/Z/09/Z)
External DOI: https://doi.org/10.1074/jbc.M113.527994
This record's URL: https://www.repository.cam.ac.uk/handle/1810/280466