Fig. 1
From: Voltage-gated sodium channels assemble and gate as dimers
Nav1.5 α-subunits form a dimer: a Crosslinking experiments performed with DSS in HEK293 cells expressing Nav1.5. Crosslinking was performed using DSS at different concentrations for 20 min. A band corresponding to a dimer of Nav1.5 α-subunit is observed in presence of the crosslinker at higher concentrations compared to the cells where no crosslinking was performed (left DMSO no DSS). Full blots are presented in Supplementary Fig. 12. b GFP photobleaching steps observed through SiMPull experiments for sodium channel GFP-Nav1.5, the chloride channel ClC-3-GFP known to form dimers, and the potassium channel Kv4.3-GFP known to form tetramers. The number of molecules analyzed (n) for each channel is indicated above each graph. Both the sodium and the chloride channels display a distribution of two photobleaching steps as would be expected for a dimeric protein whereas a distribution of four photobleaching steps was observed for the tetrameric potassium channel. c, Binomial analysis performed from transfected HEK293 cells using cDNA ratios 1:0, 10:1, 4:1 and 1:1 for either WT:L325R, S460A:L325R, or WT:L325R+ difopein. Current densities measured at −20 mV were normalized to the 1:0 WT or S460A currents for each ratios studied. Refer to Supplementary Table 1 for n. Refer to the Methods section for the equation used to obtain the theoretical curves for an expected monomer, dimer, or trimer. We can see that the current densities for the WT:L325R co-transfections decrease in a manner corresponding to an expected dimer. Importantly, when the DN mutant is co-expressed with S460A or in presence of difopein, the current density now decreases linearly as would be expected for a monomer. Data points are presented as mean ± SEM
