Partners In Crime: TDP-43 And Translational Machinery

Abstract

Amyotrophic Lateral Sclerosis (ALS) is a fatal disease that causes progressive neurodegeneration of motor neurons. Tar DNA Binding Protein (TDP-43) has been implicated in the progression of ALS, as well as at the level of pathology. TDP-43 is an RNA-binding protein that is known to regulate many steps of RNA processing, and in ALS it delocalizes to the cytoplasm and forms aggregates. These TDP-43 aggregates sequester protein and mRNA targets forming toxic complexes that disrupt various motor neuron functions. It is hypothesized that global translation is decreased in ALS, however, little is known of TDP-43’s translational targets and its precise role in the dysregulation of translation. We are exploring how levels of translation are altered in ALS through puromycin incorporation. In addition, several eukaryotic initiation factors (eIFs) have been identified in TDP-43-positive stress granules. Here we use a 4E-binding (4EBP) protein mutant, which disrupts the binding of eIF4E and eIF4G, impairing translation. 4EBP genetically interacts with TDP-43 to increase its neurotoxicity in a Drosophila model of ALS. There is currently no cure for ALS, so drug discovery is of high importance. Here we test a small molecule 776 that targets TDP-43, and in our fly model 776 showed to be neuroprotective in vivo. We also show a potential mechanism in which the small molecule rescues locomotor deficits. We are further testing the small molecule as well as exploring the interaction between TDP-43 and the translational machinery in patient-derived lymphoblastoid cells. As we identify specific translational mechanisms that are dysregulated by the presence of cytoplasmic TDP-43, new targets may emerge for the development of novel therapies for ALS.