Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

61-POS Board 61 A Role for the Sodium Channel Β3 Subunit in Promoting Nav1.5 Oligomerisation. Samantha C. Salvage 1 , Mekdes H. Mariam Debela 1 , Jennifer R. Irons 1 , Richard Butler 4 , Andrew J. Thompson 3 , Simone Weyand 1 , Christopher L. H Huang 2,1 , Antony P. Jackson 1 . 1 Biochemistry, University of Cambridge, Cambridge, United Kingdom, 2 Physiological laboratory, University of Cambridge, Cambridge, United Kingdom, 3 Pharmacology, University of Cambridge, Cambridge, United Kingdom, 4 Gurdon 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.

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