Nuclear Transport Inhibitors to Combat Disease

Nuclear transport inhibitors to combat diseases Two major health burdens world-wide are cancer and infectious diseases like viral illnesses and deadly parasite infections, each contributing to significant increased morbidity and mortality. Given the drastic increase in cases of drug resistance in various types of cancer and the lack of development of vaccines and therapeutic inhibitors in the case of viral infections, there is an urgent need for viable therapeutic approaches to combat these diseases. Selective targeting of nucleocytoplasmic transport machinery, downstream of cellular signalling is an emerging effective approach to combat these diseases. Nuclear transport machinery is highly regulated and important for various cellular functions like differentiation and development. Dysregulation of transport results in displacement of specific cargo proteins which can be an underlying cause for diseases such as cancer, inflammation and neurodegenerative conditions. In the case of viruses the host transport machinery is hijacked for its survival and this interaction often plays a critical role in the viral life cycle. Nuclear transport The nuclear import and export of proteins is classically carried out by transporters of the importin superfamily, of which there are importin (IMP α,β) and exportin (EXP) subtypes. The transporters recognize and interact with cargo proteins via nuclear localisation signals (NLSs) and nuclear export signals (NESs) and are released into nucleus or exported into the cytoplasm from nucleus with the support of the small GTPase Ran in its GTP bound state (RanGTP). [1,2,3] Nuclear transport inhibitors Although overlooked in the past, recently, research into the development of inhibitors against IMPs and EXPs is rapidly increasing. One of the most studied inhibitors, an inhibitor of exportin 1 (EXP-CRM1), Selinexor has been through >40 clinical trials and was recently approved for use by the FDA in one cancer indication [9]. Similarly, successful screening [4] performed by 1) Wagstaff et al., led to the development of antiviral agent-Budesonide for HIV1 which prevented the import of HIV1 integrase required for the viral lifecycle inside the nucleus [6,8] 2) Tay et al., and Fraser et al., led to the development of antiviral agent- Ivermectin and 4-HPR respectively. Ivermectin performs its action by targeting IMP α whereas 4-HPR is specific for NS5 protein, inhibits DENV NS5 recognition by IMP1 α/β1 heterodimer and thus attenuating the virus [5,7]. Recently Yang et al., developed GW5074, an inhibitor of the IMP1 α/β1-NS5, specifically binding to IMP α [10] and 3) DeBono et al., led to the development of antiviral agent-RU486 for alpha virus, VEEV reduced the viral activity by blocking the accumulation of viral capsid protein in the nucleus [11]. While these compounds show great promise, they are all targeted against either the Imp1 or the EXP-1 nuclear transport pathways. There are many other classes of nuclear transporter to be explored (>25 in humans) and the development of chemical probes against these will unravel the important biological role of these transporters, as well as potentially be of use in the development of therapeutics to combat specific diseases [12]. Proposed project We propose to use high throughput screening (HTS) to target specific nuclear transport pathways utilised by particular pathogens for which there are no viable treatments. One key target of interest will be importin beta1. In parallel we will perform HTS against nuclear transport targets in cancer. The compounds identified in the screens will be validated using an array of biochemical, cellular, infectious and cell growth assays. 1. Nature Struct Mol Biol 23, 624, 2016 2. Frontiers in Micro 8, 1171, 2017 3. IUBMB Life, 68, 268, 2016 4. J Biomol Screening 16, 192, 2011 5. J Infect Dis 210,1780, 2014 6. Biochem J 443, 851, 2012 7. Antiviral Res 99, 301, 2013 8. Cell Micro 21, e12953, 2019 9. J Clin Oncol 36, 859, 2018 10. Cells 8, 281, 2019 11. Sci Rep 9, 2634, 2019 12. Curr Opin Cell Biol 58, 50, 2019