Gating control of the cardiac sodium channel Nav1.5 by its β3-subunit involves distinct roles for a transmembrane glutamic acid and the extracellular domain.
Authors
Habib, Zaki F
Hwang, Soyon S
Irons, Jennifer R
Silva, Jonathan R
Publication Date
2019-12Journal Title
The Journal of biological chemistry
ISSN
0021-9258
Volume
294
Issue
51
Pages
19752-19763
Language
eng
Type
Article
This Version
VoR
Physical Medium
Print-Electronic
Metadata
Show full item recordCitation
Salvage, S., Zhu, W., Habib, Z. F., Hwang, S. S., Irons, J. R., Huang, C., Silva, J. R., & et al. (2019). Gating control of the cardiac sodium channel Nav1.5 by its β3-subunit involves distinct roles for a transmembrane glutamic acid and the extracellular domain.. The Journal of biological chemistry, 294 (51), 19752-19763. https://doi.org/10.1074/jbc.ra119.010283
Abstract
The auxiliary β3-subunit is an important functional regulator of the cardiac sodium channel Nav1.5, and some β3 mutations predispose individuals to cardiac arrhythmias. The β3-subunit uses its transmembrane α-helix and extracellular domain to bind to Nav1.5. Here, we investigated the role of an unusually located and highly conserved glutamic acid (Glu-176) within the β3 transmembrane region and its potential for functionally synergizing with the β3 extracellular domain (ECD). We substituted Glu-176 with lysine (E176K) in the WT β3-subunit and in a β3-subunit lacking the ECD. Patch-clamp experiments indicated that the E176K substitution does not affect the previously observed β3-dependent depolarizing shift of V½ of steady-state inactivation but does attenuate the accelerated recovery from inactivation conferred by the WT β3-subunit. Removal of the β3-ECD abrogated both the depolarizing shift of steady-state inactivation and the accelerated recovery, irrespective of the presence or absence of the Glu-176 residue. We found that steady-state inactivation and recovery from inactivation involve movements of the S4 helices within the DIII and DIV voltage sensors in response to membrane potential changes. Voltage-clamp fluorometry revealed that the E176K substitution alters DIII voltage sensor dynamics without affecting DIV. In contrast, removal of the ECD significantly altered the dynamics of both DIII and DIV. These results imply distinct roles for the β3-Glu-176 residue and the β3-ECD in regulating the conformational changes of the voltage sensors that determine channel inactivation and recovery from inactivation.
Keywords
Oocytes, Animals, Xenopus, Humans, Glutamic Acid, Lysine, Patch-Clamp Techniques, Ion Channel Gating, Gene Expression Regulation, Mutagenesis, Protein Structure, Secondary, Membrane Potentials, Kinetics, Mutation, NAV1.5 Voltage-Gated Sodium Channel, Protein Domains
Sponsorship
British Heart Foundation (PG/14/79/31102)
MRC (MR/M001288/1)
WELLCOME TRUST (105727/Z/14/Z)
Embargo Lift Date
2100-01-01
Identifiers
External DOI: https://doi.org/10.1074/jbc.ra119.010283
This record's URL: https://www.repository.cam.ac.uk/handle/1810/298670