Voltage-gated sodium channels (NaVs) are the critical factors that contribute to excitability signals in pain-sensing dorsal root ganglion (DRG). The gympietides are a new class of peptides derived from the venom of the Australian Stinging Tree (Gilding et al., 2020). The gympietides alter the activity of voltage-gated sodium ion channels in sensory neurons by inhibiting the inactivation of the channels, leading to a prolonged sensation of pain. Subsequent studies identified TMEM233, a previously uncharacterised transmembrane protein, as a potential molecular target for gympietides in modulating NaV activities (Jami et al., 2023).
The objective of this study is to investigate the mechanism by which these pain-inducing gympietides modulate voltage-gated sodium ion channels through their interactions with TMEM233. To achieve this, the research will focus on studying the NMR studies of isotope labelled ExTxA (Dendrocnide Excelsa toxin) in a membrane-model, both alone and in the presence of TMEM233.
Previous investigations have examined the structure of ExTxA in an acetonitrile-water mixture (Gilding et al., 2020). Interestingly, in our study, we observed significant differences in the 15N-HSQC spectrum of ExTxA when it was in DPC micelles compared to the spectrum obtained in acetonitrile. This suggests that the peptide adopts a different conformation in the DPC micelles. Given that TMEM233 is predicted to have a short extracellular region (Jami et al., 2023), it is highly likely that the peptide interacts with TMEM233 via the membrane. Therefore, the membrane-bound form of the peptide is expected to represent a more accurate state in terms of its TMEM233 modulatory function.
Overall, these findings set the stage for further investigation into the interaction between gympietides, voltage-gated sodium channels, and TMEM233, aiming to provide insights into the mechanisms underlying pain modulation.