Development Of Small-molecule Fluorescent Probes For HERG Potassium Channel

hERG (human ether-a-go-go-related gene) encodes for the delayed rectifier K+ current (Ikr) potassium channel, which plays a critical role in cardiac action potential repolarization. Long QT intervals (LQTS) can be caused both by mutation in the hERG gene and by drug interactions. Because various drugs have been found to be related to LQTS, the interaction of drug with hERG have become an important safety concern in both drug discovery and clinical practice. Therefore, in the screening of drugs for cardiac toxicity, hERG channels have been considered as a major target. Additionally, preliminary studies suggest that hERG channel expression have been up-regulated in some cancer cells, whereas expression is low or absent in the corresponding normal cells. It was also found that hERG channel can influence cell proliferation, survival and apoptosis in cancer cells. Therefore, it is likely that hERG potassium channels can become a new target and biomarker for cancer research. As a result, the study of physiological and pathological for hERG channel will have an important scientific significance on cancer reseach and clinical value for cardiatoxicity evaluation in drug preclinical study.In recent years, fluorescence technique has been widely used in various research fields. Small-molecule fluorescent probe is rapid, sensitive, convenient, and automatic advantages, and has been widely used in biology and pharmacological evaluation of proteins, nucleic acids and other important biological molecules to explore the mechanism of disease, clinical diagnosis and drug screening. A small-molecule fluorescent probe is generally composed of two parts:the recognition group and the fluoroprore moiety. The recognition group is combined with the target biological molecule with high affinity, and the fluorophore moiety can emit the light upon the excitation to mark the protein.In this study, we choose the main binding sites of astemizole and E-4031, which are the inhibitors of hERG channel, as the pharmacophore group. The fluorophores coumarin, naphthalimide,4-chloro-7-nitrobenzoxadiazole (NBD-C1), SBD-C1 and Cy5, with good fluorescent properties, were then conjugated to the recognition moiety using an aliphatic spacer. Thenceforward, several small-molecule fluorescent probes for the hERG channel were well designed and synthesized. Subsequently, the optical properties, affinity for hERG potassium channel, cell fluorescence imaging and cytotoxicity of the synthesized probes were well evaulated. The experimental results disclosed that the synthesized fluorescent probes for hERG potassium channel had suitable optical properties, high affinity for hERG channel, excellent fluorescence imaging and accepted cytotoxicity.In summary, the research of fluorescence probes for hERG channel in this thesis will provide some assistance for the study of physiology and pathology for hERG potassium channel. Moreover, these fluorescent probes can be used for screening hERG potassium channel inhibitors with great significance for cardiac toxicity safety evaluation in drug preclinical study. In addition, it will provide a new avenue to studying cancer mechanism and developing anti-cancer drugs thereof.