Tinatin I. Brelidze, Ph.D. - US grants

Ion channels in the KCNH family perform diverse and important physiological functions, including the regulation of cancer progression, neuronal excitability and cardiac contraction. KCNH channels contain a Per-Arnt-Sim (PAS) domain in their N-terminal and cyclic nucleotide-binding homology (CNBH) domain in their C-terminal regions. These intracellular domains are the key functional domains that are largely responsible for the distinct properties of KCNH channels that determine their physiological applications. The goal of this proposal is to identify small molecule ligands that directly bind to the PAS and CNBH domains and uncover the mechanisms of their action on KCNH channels. We will identify and functionally characterize KCNH channel ligands using a novel strategy based on the combination of surface plasmon resonance (SPR) and electrophysiology as the principal methods. We will first identify small molecule ligands by screening libraries of small molecules against the PAS and CNBH domains of KCNH channels with the high-throughput SPR method. We will then determine the functional effects of the identified small molecule ligands with medium-throughput two- electrode voltage-clamp method. Finally to uncover molecular mechanisms of action of the identified ligands we will use a combination of patch-clamp current recordings, mutagenesis, X-ray crystallography, SPR and structural modeling. These studies will advance our knowledge of KCNH channel regulation by intracellular ligands and PAS and CNBH domains, provide pharmacological tools to study physiological contributions of KCNH channels and will greatly facilitate the development of novel pharmaceutical agents for treatment of cardiac arrhythmias, cancer and epilepsy.

Ether-a-go-go (EAG) potassium selective channels are important regulators of neuronal excitability and cancer progression. Defects in EAG channel function are associated with neurological disorders and cancer. Despite the physiological importance of EAG channels, molecular mechanisms of EAG channel regulation by intracellular ligands and clinically relevant EAG channel regulators are not known. The goal of this proposal is to uncover molecular mechanisms of EAG channel regulation by intracellular ligands recently discovered by our laboratory and to determine a therapeutic potential of these ligands for treatment of diseases linked to EAG channels. In Specific Aim 1 we plan to solve X-ray structures of the intracellular Per-Arnt-Sim (PAS) and cyclic nucleotide- binding homology (CNBH) domains of EAG channels bound to the recently identified ligands and conduct computational simulations of the ligand binding to the PAS and CNBH domains to uncover the structural basis of EAG channel regulation by the intracellular ligands. The structural findings will be then used as a road map to guide functional experiments on the molecular mechanisms of EAG channel regulation by the ligands. In Specific Aim 2 we plan to use surface plasmon resonance method to identify novel EAG channel ligands that affect channel function through PAS and CNBH domain interface. We will then use electrophysiology to determine functional implications of strengthening or weakening of the PAS/CNBH domain interface by the identified regulators on the function of EAG channels. In Specific Aim 3 we plan to use tissue culture and zebrafish xenograft models to test therapeutic potential of the identified regulators for treatment of cancer. The results of these studies will be crucial for understanding fundamental regulatory mechanisms of EAG and related ERG and ELK channels, and for attaining therapeutic potential of EAG channel regulators.