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

Area of Science:

• Molecular Biology
• Neuroscience
• Biochemistry

Background:

• TDP-43 is a nuclear factor essential for pre-mRNA splicing.
• Deletion of TDP-43's N-terminal domain (NTD) causes cytoplasmic mislocalization and inclusion formation, linked to proteinopathies.
• The precise role of the TDP-43 NTD in its function and disease pathogenesis is largely unknown.

Purpose of the Study:

• To investigate the structure and function of the TDP-43 NTD.
• To elucidate the NTD's role in TDP-43 inclusion formation and pre-mRNA splicing.
• To understand the mechanisms underlying TDP-43 proteinopathy.

Main Methods:

• Biochemical and biophysical approaches were employed.
• Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the NTD structure.
• Mutagenesis and size-exclusion chromatography were utilized to define the dimerization interface.
• Cell-based experiments assessed TDP-43 localization and splicing activity.

Main Results:

• TDP-43 NTD forms concentration-dependent homodimers in solution.
• Intermolecular disulfide bonds lead to tetramerization of the NTD.
• The dimerization interface involves Leu71 and Val72 within the β7-strand.
• N-terminal dimerization protects TDP-43 from cytoplasmic inclusion formation.
• Dimerization enhances TDP-43's pre-mRNA splicing activity in the nucleus.

Conclusions:

• The N-terminal dimerization of TDP-43 is critical for its nuclear localization and splicing function.
• TDP-43 NTD dimerization acts as a protective mechanism against cytoplasmic aggregation and associated proteinopathies.
• These findings offer mechanistic insights into TDP-43's physiological roles and the development of related diseases.