Remodeling the Interactions between TDP-43 and RNA for Development of Therapeutics for ALS

Abstract

Developing effective treatment strategies for amyotrophic lateral sclerosis (ALS) that affect upper and lower motor neuron requires an understanding of the underlying cellular pathway that leads to motor neuron death and muscle atrophy. RNA dysregulation is a hypothesized disease mechanism in ALS. Studies have shown that pathological transactive response (TAR) DNA Binding Protein (TDP-43) binds irreversibly to RNA in stress granules and forms membraneless prion-like TDP-43 aggregates in cytoplasmic motor neurons1. These membraneless compartments can form in cells through liquid-liquid phase separation (LLPS). A recent study showed that mRNA secondary structure promotes LLPS to build membraneless compartments in cells.2 Based on a remodeling hypothesis by Coyne et al.,3 we hypothesized that remodeling the interactions between TDP-43 and RNA using small molecules would decrease motor neuron toxicity. Using in silico docking, we screened 50,000 compounds on the RNA recognition motifs 1 and 2 of TDP43 (RRM1 and RRM2). We identified rTRD001 that was able to bind to TDP-43 in the RRM1 domain, disrupt TDP-43 interaction with RNA, reduce cytoplasmic aggregate and cytotoxicity in motor neuron cell line NSC-34, and mitigate TDP-43 dependent phenotypes in an ALS fly model based on the overexpression of mutant TDP-43. Further studies are necessary in order to assess the mechanism and mode of action for this neuroprotective effect for this compound.