Emerging Concepts in Ion Channel Biophysics

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Emerging Concepts in Ion Channel Biophysics Poster Abstracts
59
61-POS Board 61
A Role for the Sodium Channel Β3 Subunit in Promoting Nav1.5 Oligomerisation.
Samantha C. Salvage1, Mekdes H. Mariam Debela1, Jennifer R. Irons1, Richard Butler 4,
Andrew J. Thompson3, Simone Weyand1, Christopher L. H Huang2,1, Antony P. Jackson1 .
1Biochemistry, University of Cambridge, Cambridge, United Kingdom, 2Physiological
laboratory, University of Cambridge, Cambridge, United Kingdom, 3Pharmacology, University
of Cambridge, Cambridge, United Kingdom, 4Gurdon Institute, University of Cambridge,
Cambridge, United Kingdom.
The cardiac voltage gated sodium channel (Nav1.5) is responsible for the rapid depolarising
phase of the cardiac action potential. Nav1.5 is comprised of a pore-forming sodium ion-
selective α subunit together with β subunits. The β3 subunit regulates multiple aspects of Nav1.5
channel gating and trafficking behaviour, and mutations in the β3 subunit are implicated in
cardiac pathologies such as Brugada syndrome. We have determined the atomic-resolution
structure of the extracellular β3 immunoglobulin domain and shown that it forms trimers. Here
we extend this finding to study its interaction with the Nav1.5 alpha subunit.
We transiently transfected HEK293 cells with β3 constructs tagged with either GFP or myc and
performed chemical cross-linking, gel-filtration and proximity ligation assays (PLA). This
indicated the presence of β3 oligomers – in particular, dimers and trimers in vivo. Furthermore,
using PLA and affinity-chromatography, we show that β3 also enhances the cross-linking of
Nav1.5 alpha subunits. Interestingly, the PLA data shows that the β3-induced clustering of
Nav1.5 alpha subunits occurs particularly at the plasma membrane. Using whole-cell patch-
clamp electrophysiology, we assess the functional implications of these multi-subunit Nav1.5
oligomers.