The N-terminal dimerization is required for TDP-43 splicing activity

Lei-Lei Jiang,Jian-Hua He,Jun-Ting Zhang,Hong-Yu Hu,Min-Jun Li,Jun-Ye Hong,Wei Xue,Shao-Ning Yu

doi:10.1038/s41598-017-06263-3

Abstract

TDP-43 is a nuclear factor that functions in promoting pre-mRNA splicing. Deletion of the N-terminal domain (NTD) and nuclear localization signal (NLS) (i.e., TDP-35) results in mislocalization to cytoplasm and formation of inclusions. However, how the NTD functions in TDP-43 activity and proteinopathy remains largely unknown. Here, we studied the structure and function of the NTD in inclusion formation and pre-mRNA splicing of TDP-43 by using biochemical and biophysical approaches. We found that TDP-43 NTD forms a homodimer in solution in a concentration-dependent manner, and formation of intermolecular disulfide results in further tetramerization. Based on the NMR structure of TDP-43 NTD, the dimerization interface centered on Leu71 and Val72 around the β7-strand was defined by mutagenesis and size-exclusion chromatography. Cell experiments revealed that the N-terminal dimerization plays roles in protecting TDP-43 against formation of cytoplasmic inclusions and enhancing pre-mRNA splicing activity of TDP-43 in nucleus. This study may provide mechanistic insights into the physiological function of TDP-43 and its related proteinopathies.

Highlights

TDP-43 (TAR DNA-binding protein of 43 kDa) is a DNA/RNA binding protein belonging to the heterogeneous nuclear ribonucleoprotein family
Several studies have suggested that TDP-43 mainly forms a functional homodimer under physiological conditions, but it may transform to oligomers or aggregates, which lead to loss of function in pathological diseases[39,40,41,42,43]
It was proposed that TDP-43 forms a dimeric structure under physiological conditions and its N-terminal domain (NTD) is capable of oligomerization and self-interaction[42,43,44,45,46,47,48]

Summary

Introduction

TDP-43 (TAR DNA-binding protein of 43 kDa) is a DNA/RNA binding protein belonging to the heterogeneous nuclear ribonucleoprotein (hnRNP) family. They are both canonical β-barrel structures constructed by seven β-strands and a short α-helix In this regard, mechanistic study based on structural analysis of the NTD will be beneficial to understanding the biological roles played by TDP-43 under physiological and pathological conditions. Mechanistic study based on structural analysis of the NTD will be beneficial to understanding the biological roles played by TDP-43 under physiological and pathological conditions In this communication, we further investigated the biochemical properties and physiological function of the NTD of TDP-43. This study may provide further insights into the biological function of the N-terminal dimerization in integration of TDP-43 conformation and its splicing activity, which is implicated in the pathological roles in neurodegenerative diseases

Methods

Results

Conclusion