TDP-43 dimerizes in human cells in culture

Area of Science:

• Neuroscience
• Molecular Biology
• Protein Biochemistry

Background:

• TAR DNA-binding protein-43 (TDP-43) is crucial for gene expression regulation.
• Aberrant TDP-43 aggregates are hallmarks of frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis (ALS).
• The mechanism initiating TDP-43 aggregation remains unclear.

Purpose of the Study:

• To investigate the nature and function of an observed 86-kDa TDP-43 species.
• To determine if this 86-kDa TDP-43 form is related to disease pathology.

Main Methods:

• Western blot analysis using TDP-43 specific antibodies.
• Immunoprecipitation assays.
• siRNA knockdown of TDP-43.
• Overexpression of tagged TDP-43 constructs.
• Analysis of human brain tissue.

Main Results:

• An 86-kDa TDP-43 band was detected in cultured cells and human brain tissues, including ALS cases.
• This 86-kDa band was identified as a dimer of TDP-43, with the N-terminal half (residues 3-183) mediating intermolecular interaction.
• Overexpression of the TDP-43 dimer led to cytoplasmic sequestration and accumulation of high-molecular-mass TDP-43 species.
• The 86-kDa dimer was constitutively expressed under physiological conditions.

Conclusions:

• The 86-kDa band represents a constitutively expressed dimer of TDP-43.
• TDP-43 dimerization may be a fundamental cellular process.
• Understanding TDP-43 dimerization could offer insights into the pathogenesis of TDP-43 proteinopathies.