The Dynamics of TAR DNA-Binding Protein 43 in Stress Granules and its Role in Amyotrophic Lateral Sclerosis
Ashley Bo Zhang1,2, Shangxi Xiao1, Philip McGoldrick1, Janice Robertson1,2*, 1Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, Canada; 2Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Toronto, Canada *Corresponding Author
Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of upper and lower motor neurons, and is pathologically typified by cytoplasmic inclusions containing TAR DNA-binding protein 43 (TDP-43) in degenerating neurons. TDP-43 is a DNA/RNA binding protein that is recruited to stress granules. Stress granules triage translationally stalled pre-initiation complexes, promoting expression of mRNAs necessary for cell survival. TDP-43 is abnormally phosphorylated in ALS, and the role of this abnormal phosphorylation in stress granule dynamics has not been widely explored. We hypothesize that TDP-43 phosphorylation is important for stress granule dynamics and that this event is dependent on cell type and stressor. HEK293, SH-SY5Y, and HeLa cells were stressed with sodium arsenite, hydrogen peroxide, and sorbitol and allowed to recover before assessing stress granule formation and TDP-43 localization. Sodium arsenite induced stress granule formation after one hour, detected using an antibody to G3BP1. However, the dynamics of TDP-43 recruitment to stress granules were much slower, occurring only in HeLa cells after 24h recovery from sodium arsenite. Importantly, TDP-43 recruitment to stress granules correlated with phosphorylated TDP-43. Our results demonstrate that recruitment of TDP-43 to stress granules is context-specific, depending on both cell type and nature of the stressor. Further investigation into the effects of TDP-43 phosphorylation in stress granule dynamics may provide new insight into the interplay between TDP-43 and stress granules in ALS pathogenesis.
Funding Acknowledgements: CRND Graduate Student Aid Endowment, Canadian Institutes of Health Research and ALS Canada