Poster Presentation The 47th Lorne Conference on Protein Structure and Function 2022

Developing novel small molecule ligands of TDP-43 (#177)

Hei Wun Alison Cheng 1 , Timothy B Callis 2 , Andrew P Montgomery 2 , Chi L Pham 1 , Jonathan J Danon 2 , Nicholas J Geraghty 3 , Mark Wilson 3 , Eryn L Werry 2 4 , Margaret Sunde 1 , Michael Kassiou 2
  1. School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Darlington, NSW, Australia
  2. School of Chemistry, University of Sydney, Camperdown, NSW, Australia
  3. School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, The University of Wollongong, Wollongong, NSW, Australia
  4. Central Clinical School, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia

The TAR DNA-binding protein 43 (TDP-43) is a DNA/RNA binding protein involved in RNA transcription and translation.1 Accumulation of intracellular TDP-43 inclusions is a pathological hallmark in some patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). To date, there are no disease-altering treatments for these diseases. The pathological overlap of TDP-43 in both diseases makes it an attractive target for therapeutic intervention and PET ligand development. Over the years, to assist in development of such ligands, several studies have attempted to purify full length TDP-43 to a reasonable yield, but limitations in reproducibility have been reported.2 A novel protocol was developed to express and purify full length TDP-43 with a hexa-histidine, ubiquitin fusion tag (His-Ubiq-TDP-43). Characterisation of TDP-43 using circular dichroism suggested large This purified His-Ubiq-TDP-43 was then used to perform an amplified luminescent proximity homogeneous assay (AlphaScreen®), which identifies compounds that interfere with RNA binding to the RNA-recognition motifs (RRMs) of TDP-43. From a hit-library of 8 compounds, two compounds bound to His-Ubiq-TDP-43. Fitting to a two-site model suggested compound 1 bound with affinities (pKi) of -7.10 ± 0.29 M  (high-affinity site) and -4.06 ± 0.45 M (low-affinity site). Compound 2 bound to a single site with pKi of -5.77 ± 0.23 M. Our findings have identified novel small molecules that target RNA-protein interactions of TDP-43 and can act as leads for further iterative drug discovery, with the ultimate aim of producing therapeutics and PET ligands for use in ALS and FTD.

 

 

 

  1. Neumann, M.; Sampathu, D. M.; Kwong, L. K.; Truax, A. C.et al., Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science 2006, 314 (5796), 130-133.
  2. Vega, M. V.; Nigro, A.; Luti, S.; Capitini, C.et al., Isolation and characterization of soluble human full‐length TDP‐43 associated with neurodegeneration. The FASEB Journal 2019, 33 (10), 10780-10793.