Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA273

Poster Communications

Dimerization of sodium channel subtype Nav1.7

A. Rühlmann1, C. Rösseler1, A. Foerster1, K. LE CANN1, G. Schmalzing2, A. Lampert1

1. Institute of Physiology, Uniklinik RWTH Aachen, Aachen, Germany. 2. Institute of Pharmacology, Uniklinik RWTH Aachen, Aachen, Germany.

Sodium channels in the peripheral nervous system are known to play a major role in the initiation and transmission of action potentials which can lead to the perception of pain. Mutations in different channel subtypes can lead to either pain syndromes which are associated with increased pain or its total loss. Interestingly, most of the pain-linked mutations occur as a heterozygous mutation, which leads to the simultaneous presence of WT and mutated channels in the expressing cells. In 2017, Clatot et al showed evidence that Nav1.5 channels form dimers which support a coupled gating mechanism. In our study, we investigate dimerization of Nav1.7 with itself and other sodium channel subtypes, which could enhance or alleviated the effect of pain-linked mutations. In order to investigate if Nav1.7 might dimerize we used biochemical and electrophysiological approaches. To assess a potential functional coupling, the electrophysical behavior of the previously reported pain-associated Nav1.7-mutation A1632E (Estacion et al, 2008) was studied via the patch clamp technique in a heterologous expression system using human embryonic kidney cells (HEK cells). HEK cells were transfected with either Nav1.7 alone, Nav1.7 and A1632E combined and the A1632E mutation by itself. When assessing inactivation gating, we observed a shift for the A1632E mutation compared to WT, and this shift was smaller when WT and A1632E were combined (results of Boltzmann fits: V1/2 for WT = 81.56mV ± 0.94 n=20, for A1632E = 68.97mV ±1.00 n=33, for WT combined with A1632E = 74mV ±2.68 n=19). We observed a persistent current for the A1632E mutation (7% ±0.005 of the peak inward current, n=35) which was absent in our recordings of Nav1.7 WT(n=22). In cells which expressed Nav1.7 and A1632, small persistent currents (2%, ±0.004, n=25) could be measured. Our results suggest that Nav 1.7 forms dimers. Therefore, we plan to repeat these experiments in the presence of difopein, a 14-3-3 protein inhibitor which was shown to inhibit channel dimerization in Nav1.5 (Clatot et al, 2017; Masters and Fu, 2001) to confirm these findings.

Where applicable, experiments conform with Society ethical requirements