Interdomain interactions of the transactive response DNA binding protein 43 kDa (TDP-43)

Transactive response DNA binding protein, 43 kDa (TDP-43) is 416-residue RNA processing and transport protein, observed in insoluble cytoplasmic aggregates within affected neurons in neurodegenerative diseases. TDP-43 has three domains: the N-terminal (N), RNA-binding (R) and unstructured C-terminal domains (G). Unstructured domains often form intramolecular interactions regulating other domains; our goal was to determine if such an interaction occurs in TDP-43. In Far Western blots, tagged NR was observed to bind to G. A 10 residue C-terminal truncation of G virtually abolished binding and introduction of phosphomimetics at Ser409/Ser410 also reduced binding. Sedimentation velocity ultracentrifugation with tagged NR and G also revealed interaction, observed by a shift in sedimentation coefficients when compared to those of the individual polypeptides. In vivo colocalization studies confirmed a cellular interaction between fluorescently labeled NR and G. This interaction has potential implications for the regulation of TDP-43 and the mechanism of generation of aggregative forms