Abstract
Voltage-gated Na+ (NaV) channels regulate homeostasis in bacteria and control membrane electrical excitability in mammals. Compared to their mammalian counterparts, bacterial NaV channels possess a simpler, fourfold symmetric structure and have facilitated studies of the structural basis of channel gating. However, the pharmacology of bacterial NaV remains largely unexplored. Here we systematically screened 39 NaV modulators on a bacterial channel (NaChBac) and characterized a selection of compounds on NaChBac and a mammalian channel (human NaV1.7). We found that while many compounds interact with both channels, they exhibit distinct functional effects. For example, the local anesthetics ambroxol and lidocaine block both NaV1.7 and NaChBac but affect activation and inactivation of the two channels to different extents. The voltage-sensing domain targeting toxin BDS-I increases NaV1.7 but decreases NaChBac peak currents. The pore binding toxins aconitine and veratridine block peak currents of NaV1.7 and shift activation (aconitine) and inactivation (veratridine) respectively. In NaChBac, they block the peak current by binding to the pore residue F224. Nonetheless, aconitine has no effect on activation or inactivation, while veratridine only modulates activation of NaChBac. The conservation and divergence in the pharmacology of bacterial and mammalian NaV channels provide insights into the molecular basis of channel gating and will facilitate organism-specific drug discovery.
Highlights
Voltage-gated Na+ (NaV) channels regulate homeostasis in bacteria and control membrane electrical excitability in mammals
A group of 16 small molecule compounds known to block mammalian Nav channels, including antiarrhythmics, anticonvulsants, muscle relaxants, and local anesthetics were selected for evaluation
Our results are consistent with a previous report that QX-314 has no effect on the NaChBac channel when applied e xtracellularly[21]
Summary
Voltage-gated Na+ (NaV) channels regulate homeostasis in bacteria and control membrane electrical excitability in mammals. Aconitine has no effect on activation or inactivation, while veratridine only modulates activation of NaChBac. The conservation and divergence in the pharmacology of bacterial and mammalian NaV channels provide insights into the molecular basis of channel gating and will facilitate organism-specific drug discovery. Current traces (left), current–voltage (I–V) (middle), conductance–voltage (G–V), and steady-state inactivation (SSI) relationships are shown for both NaV1.7 and NaChBac measured before and after application of 200 μM lidocaine. Lidocaine blocks both NaChBac and NaV1.7 channels. Ambroxol has similar effects as lidocaine on both NaV1.7 and NaChBac
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