"Exploiting Marine Biodiversity To Develop Drugs For Normalising Neural Communication In Disease: Therapeutics Targeting Neuronal Channel"
Research Measure: Marine Biodiscovery
Funding Type: NDP Marine Research Sub-Programme
Funding Year: 2007
Project Duration: 36 Months
Project Type: PhD Scholarship
Total Grant-Aid: €90,000
Lead Partner: Dublin City University
Overview of this proposed research:
There is an unmet need for therapeutic agents to normalise aberrant communication in the nervous system. The International Centre for Neurotherapeutics (ICNT) focuses on developing novel drugs to correct the transfer of neural signals in disease states. Electrical signalling in neurons is mediated by a super-family of genes encoding ion channel proteins. When this fundamental process becomes compromised by disease, tuning of ion channels provides a means to ameliorate the symptoms. Current therapies for epilepsy, arrhythmia, anxiety, insomnia, diabetes and neuropathic pain include pharmaceuticals that target ion channels.
Our focus is on voltage-activated K+ channels (Kvs), especially Kv1 which comprises the largest sub-family, due to their functional importance and because we possess unique experience having successfully identified, localised, purified and structural characterised these neuronal membrane proteins. Such channels are tetrameric combinations of α subunits (Kv1.1-1.6) encoded by 6 different genes; importantly, one of these subunits (Kv1.1) is involved in a variety of human diseases including genetic channelopathies (e.g. Episodic ataxia I), some forms of epilepsy and multiple sclerosis (Lehmann-Horn and Jurkat-Rott, 1999; Manganas et al., 2001). In experimental models of the letter, inhibition of Kv1 channels in axons with 4-aminopyridine corrects the inefficient conduction of nerve impulses (Smith et al., 2000); whilst this highlights the prospect for therapeutic intervention, its potency is too low for clinical application. Thus, to find better inhibitors of Kv1 channels, the biodiversity of marine natural products is to be exploited.
Outline of Ph.D. project:
Compounds capable of inhibiting recombinantly-recreated Kv1 channels, exclusively available at ICNT, will be assessed via automated screening methodologies found to be most effective in the Marine Biodiscovery Programme Proof-of-Concept phase. These involve a combination of determining inhibition of rubdium (Rb+) efflux from cells expressing the authentic oligomeric subtypes of K+ channels, and quantifying changes induced on membrane potential (Sokolov et. al.. 2007). Also, influence of bio-active marine compounds on electrical excitability of living neurons, via other channels, will be surveyed. By these means, extracts from two species of Irish algae (Bonnemasonia hamifera and Heterosiphonia japonica) have been identified which inhibit brain K+ channels. Further characterisation of these activities requires chemical separations of active compounds from the extracts and elucidation of their structures, facets to be carried out by Prof. P. Guiry (UCD). Specificities of the resultant K+ channel inhibitors will be confirmed by patch-clamp recordings in cultured neurons, and their mechanism of action elucidated. As a family of potent and selective Kv1 channel inhibitors occur in species of Irish sea anemones (Anemonia sulcata and Actinia equina), these should provide another good source of additional compounds with therapeutic properties (Honma and Shiomi, 2006). Emphasis is to be placed on finding molecules that selectively affect individual K+ channel concatamers as this would allow tuning of a particular subtype at a given location, thereby, achieving the desired therapeutic benefit and avoiding unwanted side-effects. The best candidate drugs will be further improved by combining their structural information, obtained by the chemistry partners, with the atomic resolution structure available for Kv1 channels (Long et al., 2005) to model their interaction. Binding sites thus identified will be validated by mutagenesis of pertinent amino acids in the channel, followed by assay of the drug potencies. In the longer term, novel high-affinity compounds with desirable subtype specificity will be structurally modified to optimize their drug-like qualities. Drugs deemed to hold sufficient therapeutic potential will then be further developed with Pharmaceutical partners. The inter-disciplinary nature of this project will ensure that the graduate obtains first-rate training in a range of advanced cellular and molecular technologies relevant to the Biopharmaceutical Industry.