Engineering subtype selective inhibitors of voltage-sensitive sodium channels

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During efforts to find new inhibitors of voltage sensitive sodium channels (VSSCs), we have discovered two new families of mu-conotoxins from Australian Conus tulipa and C. striatus that inhibit neuronal and muscle forms of the tetrodotoxin-sensitive (TTX-S) sodium channel. From these and related analogues we have identified a number of selective and highly potent inhibitors of VSSCs, opening the possibility of producing the first subtype selective TTX-S inhibitors useful in diseases such as epilepsy and stroke. These analogues also showed high selectivity for TTX-S sodium channels over a TTX-resistant (TTX-R) subtype hPN3, a key channel involved in the transmission of neuropathic pain that we recently cloned from human dorsal root ganglia. Given that TTX-S and TTX-R sodium channels have the same overall structure but differ at a relatively small number of key positions likely to affect mu-conotoxin binding, we believe it is possible to reverse engineer mu-conotoxin pharmacology in favour of the TTX-R form. This project will engineer subtype specific inhibitors of sodium channels in nerves through an understanding of how and wheremu-conotoxin bind to the sodium channel. Our long-term goal is to produce sodium channel drug candidates using m-conotoxins as templates for the development of subtype selective inhibitors of TTX-S and TTX-R sodium channels. The results of this study are designed to maximise the potential of this class of peptides as leads to the development of a new classes of therapeutics for pain, epilepsy and stroke.