Kim SH, Shanware NP, Bowler MJ, Tibbetts RS

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease that preferentially targets motor neurons. It was recently found that dominant mutations in two related RNA-binding proteins, TDP-43 (43-kDa TAR DNA-binding domain protein) and FUS/TLS (fused in sarcoma/translated in liposarcoma) cause a subset of ALS. The convergent ALS phenotypes associated with ...

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TDP-43 and FUS/TLS mutations are suggestive of a functional relationship; however, whether or not TDP-43 and FUS/TLS operate in common biochemical pathways is not known. Here we show that TDP-43 and FUS/TLS directly interact to form a complex at endogenous expression levels in mammalian cells. Binding was mediated by an unstructured TDP-43 C-terminal domain and occurred within the context of a 300-400-kDa complex that also contained C-terminal cleavage products of TDP-43 linked to neuropathology. TDP-43 C-terminal fragments were excluded from large molecular mass TDP-43 ribonucleoprotein complexes but retained FUS/TLS binding activity. The functional significance of TDP-43-FUS/TLS complexes was established by showing that RNAi silencing of either TDP-43 or FUS/TLS reduced the expression of histone deacetylase (HDAC) 6 mRNA. TDP-43 and FUS/TLS associated with HDAC6 mRNA in intact cells and in vitro, and competition experiments suggested that the proteins occupy overlapping binding sites. The combined findings demonstrate that TDP-43 and FUS/TLS form a functional complex in intact cells and suggest that convergent ALS phenotypes associated with TDP-43 and FUS/TLS mutations may reflect their participation in common biochemical processes.

Date: Oct. 29, 2010

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