Crystal structure and molecular imaging of the Nav channel ß3 subunit indicates a trimeric assembly.
J Biol Chem
; 289(15): 10797-10811, 2014 Apr 11.
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| MEDLINE
| ID: mdl-24567321
ABSTRACT
The vertebrate sodium (Nav) channel is composed of an ion-conducting α subunit and associated ß subunits. Here, we report the crystal structure of the human ß3 subunit immunoglobulin (Ig) domain, a functionally important component of Nav channels in neurons and cardiomyocytes. Surprisingly, we found that the ß3 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 ß3 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 ß3 subunit trimers on the plasma membrane of transfected HEK293 cells. We further show that ß3 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 ß3 subunits in Nav channel cross-linking and provide new structural insights into some pathological Nav channel mutations.
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MEDLINE
Asunto principal:
Subunidad beta-3 de Canal de Sodio Activado por Voltaje
Idioma:
En
Revista:
J Biol Chem
Año:
2014
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Article