TDP-43 Phosphorylation: Pathological Modification or Protective Factor Antagonizing TDP-43 Aggregation in Neurodegenerative Diseases?

Abstract

TDP-43 is a ubiquitously expressed RNA-binding protein that aggregates in the brains of patients suffering from neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and Alzheimer's disease. Aggregated TDP-43 in these diseases is hyperphosphorylated in its C-terminal intrinsically disordered region, while physiological TDP-43 is normally unphosphorylated. Whether TDP-43 phosphorylation is a pathological driver, or rather a protective antagonist of TDP-43 aggregation and consequently neurodegeneration, is still debated and a matter of ongoing research. Here, we review current knowledge about TDP-43 phosphorylation in disease and the kinases and phosphatases that regulate this post-translational modification. We discuss how TDP-43 phosphorylation is thought to shape TDP-43's phase separation, aggregation and toxicity in neurodegenerative diseases. We highlight recent research that provides evidence that hyperphosphorylation antagonizes TDP-43 phase separation and aggregation, and speculate about a potential role of condensates in TDP-43 phosphorylation.