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
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