Annette Nicke’s research while affiliated with University of Queensland and other places

The voltage-gated sodium channel Nav1.8 mediates the tetrodotoxin-resistant (TTX-R) Na⁺ current in nociceptive primary sensory neurons, which has an important role in the transmission of painful stimuli. Here, we describe the functional modulation of the human Nav1.8 α-subunit in Xenopus oocytes by auxiliary β subunits. We found that the β3 subunit down-regulated the maximal Na⁺ current amplitude and decelerated recovery from inactivation of hNav1.8, whereas the β1 and β2 subunits had no such effects. The specific regulation of Nav1.8 by the β3 subunit constitutes a potential novel regulatory mechanism of the TTX-R Na⁺ current in primary sensory neurons with potential implications in chronic pain states. In particular, neuropathic pain states are characterized by a down-regulation of Nav1.8 accompanied by increased expression of the β3 subunit. Our results suggest that these two phenomena may be correlated, and that increased levels of the β3 subunit may directly contribute to the down-regulation of Nav1.8. To determine which domain of the β3 subunit is responsible for the specific regulation of hNav1.8, we created chimeras of the β1 and β3 subunits and co-expressed them with the hNav1.8 α-subunit in Xenopus oocytes. The intracellular domain of the β3 subunit was shown to be responsible for the down-regulation of maximal Nav1.8 current amplitudes. In contrast, the extracellular domain mediated the effect of the β3 subunit on hNav1.8 recovery kinetics.

Significance Predicting how conotoxins bind to nicotinic acetylcholine receptors (nAChRs) is hard. Not only are these venom-derived peptides large, but the structures of many nAChRs are unknown. In response, we developed an ensemble-docking algorithm named ToxDock. We used ToxDock to reliably dock the conotoxin α-GID to a homology model of the α4β2 nAChR, a main nAChR in the brain and target for nicotine addiction therapeutics. A virtual screen with ToxDock identified four α-GID analogs and, based on experimental evidence, correctly predicted their activity at the α4β2 nAChR in all cases. More screening showed that two of these analogs have substantially reduced antagonism at the human α7 nAChR, a key step in optimizing α-GID into a tool for studying brain nAChRs.