Cyclic AMP-Dependent Protein Kinase Phosphorylates TDP-43 and Modulates Its Function in Tau mRNA Processing

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Trans-active response DNA-binding protein of 43 kDa (TDP-43) is a nuclear protein involved in mRNA processing.
• TDP-43 regulates tau mRNA instability and exon 10 inclusion, processes implicated in neurodegenerative diseases.
• TDP-43 phosphorylation affects its function and aggregation, suggesting a regulatory role for kinases.

Purpose of the Study:

• To investigate the role of cyclic AMP-dependent protein kinase (PKA) in the phosphorylation and function of TDP-43.
• To determine the specific sites of TDP-43 phosphorylation by PKA.
• To assess the impact of PKA-mediated phosphorylation on TDP-43's role in tau mRNA processing.

Main Methods:

• Co-immunoprecipitation and co-localization assays to study TDP-43 and PKA interaction in the nucleus.
• In vitro and cell-based assays to identify and confirm phosphorylation sites on TDP-43 by PKA.
• Functional assays measuring tau mRNA instability and exon 10 inclusion in response to PKA overexpression.

Main Results:

• TDP-43 was found to co-immunoprecipitate with and co-localize to the nucleus with PKA.
• PKA directly phosphorylated TDP-43 at specific serine residues (Ser379, Ser403/404, Ser409/410).
• Phosphorylation by PKA enhanced further phosphorylation of TDP-43 at these sites.
• Overexpression of PKA reduced TDP-43's promotion of tau mRNA instability and exon 10 inclusion.

Conclusions:

• PKA directly phosphorylates TDP-43 at multiple sites, influencing its function.
• PKA-mediated phosphorylation of TDP-43 modulates its role in tau mRNA processing.
• These findings suggest that PKA signaling may be a therapeutic target for TDP-43-related pathologies, particularly in Alzheimer's disease (AD).