Target ALS is proud to have supported new research, published in January 2025, in Cell Reports. The study, titled “Opposing roles of p38α-mediated phosphorylation and PRMT1-mediated arginine methylation in driving TDP-43 proteinopathy”, provides significant new insights into the biology of TDP-43, a protein closely linked to ALS and other neurodegenerative diseases. By uncovering a novel methylation modification that interacts with TDP-43 phosphorylation, this study deepens our understanding of the mechanisms behind TDP-43 aggregation and post-translational modification. Given that TDP-43 phosphorylation and aggregation are hallmarks of ALS pathology, a better understanding of their regulation could improve our understanding of why motor neurons degenerate in ALS and may lead to new therapeutic strategies.
Advancing ALS Research: Target ALS Supports Breakthrough Study
The collaborative project, funded by Target ALS, sought to identify novel chemical compounds capable of reducing the toxicity associated with TDP-43, FUS, and C9orf72-related dipeptide repeats. One compound was found to modulate TDP-43 phosphorylation by inhibiting the p38α kinase. Using a combination of innovative chemical and genetic tools, the researchers explored the biology of p38α-dependent TDP-43 phosphorylation, focusing on both the established pathological sites, Serine 409/410, and a newly identified site at Serine 292. Moreover, they uncovered a novel mechanism of PRMT1-dependent methylation of TDP-43, which inhibits p38α phosphorylation. Although the authors note that TDP-43 is phosphorylated by multiple kinases, not just p38α, their findings shed further light on this biology and suggest that targeting p38α-driven phosphorylation or methylation of TDP43 could aid in future drug discovery efforts. Much of the academic work highlighted in the publication showing an interplay between TDP43 phosphorylation and methylation was conducted in models that are less directly representative of the disease. These models include immortalized SH-SY5Y cells, which are neuronal but not ALS patient-derived or closely representative of motor neurons. The next steps in this research involve testing more of these findings in disease-relevant systems, such as iPSC-derived motor neurons. “We predict that R293 methylation would be reduced in patients and in patient-derived neurons compared to controls, and it will be interesting to test this prediction,” said Jim Shorter. There may also be exciting opportunities to develop small molecules that can selectively increase methylation or further decrease phosphorylation of TDP-43—strategies that could further untangle the biology of TDP-43 or even have meaningful therapeutic implications for ALS. “Finding mechanisms to increase R293 methylation or reduce R293 demethylation are important future directions for this work. We anticipate that R293 methylation is likely to antagonize phosphorylation of S292 by other kinases beyond just p38ɑ,” Shorter said. Target ALS looks forward to further developments in this area, and we believe the exciting progress made so far is just the beginning.
This work is a testament to the success of the collaborative approach fostered by Target ALS. The research is the culmination of a consortium that bridged academia and industry, which Target ALS helped fund in 2016. These results highlight not only the potential of these chemical compounds but also the broader promise of collaboration in advancing ALS research. The use of the cutting-edge tools to evaluate cell death developed in Steve Finkbeiner’s lab, in combination with drug screening expertise from AstraZeneca, has uncovered novel, modifiable disease-relevant biology, further underscoring the value of cross-sector partnerships in pushing the boundaries of ALS science.
“Since publishing this work, I have been approached by several biotechnology companies, with whom I have existing relationships, because they have chemical matter targeting kinases closely related to p38ɑ. They are interested in applying these compounds to potentially treat ALS,” said Steve Finkbeiner, Professor at the Department of Neurology at the University of California San Francisco and Director of the Gladstone Center for Systems and Therapeutics, one of the paper’s co-authors and pioneer of the GEDI cell death assay used in this work. For Target ALS, this continuing collaboration between academia and industry is the goal, as such partnerships are able to both uncover novel biology and push candidate therapeutic approaches to the clinic.
As the article points out, TDP43 has many phosphorylation sites that could be drugged. Targeting one site or multiple sites are both avenues that are being tested.
“Next steps are to assess p38ɑ/CK1δ/CK1ε dual inhibitors as a broad-spectrum kinase inhibitor approach to this problem,” said Jim Shorter, Professor of Biochemistry and Biophysics at the Perelman School of Medicine at the University of Pennsylvania and Senior Author/Lead Contact on the paper.
CK1δ and CK1ε, members of the CK1 kinase family, also play a role in the pathological phosphorylation of TDP-43. Targeting both this kinase family and p38α could reduce TDP-43 phosphorylation beyond the levels achieved by targeting each kinase individually. Currently, Target ALS is funding research exploring CK1 inhibition as a potential ALS therapeutic strategy, led by Neumora’s Nick Brandon, who is also a co-author of this study. Understanding how motor neurons respond to inhibition of each of these kinases and to dual CK1/p38ɑ inhibition will further our understanding of how TDP-43 biology contributes to ALS and will indicate whether modulating TDP-43 phosphorylation status is clinically viable as an ALS treatment strategy.
Target ALS is proud to support research that revealed a deeper biological understanding of TDP43 regulation and accelerated development of many different therapeutics against this key protein, the pathological hallmark of ALS.
Below is a summary of the results, but the full study can be accessed here.
- p38α kinase directly phosphorylates TDP-43 at the pathological serine 409 and serine 410 sites
- Chemical and oligonucleotide-mediated inhibition (siRNA) of p38α reduces phospho-TDP-43 levels in several paradigms and increases cell survival in an optical cell death assay designed by Steve Finkbeiner (GEDI)
- p38α also phosphorylates TDP-43 at a distinct site, serine 292
- TDP-43 is also methylated by PRMT1 protein at arginine 293.
- Arginine 293 methylation reduces the amount of phosphorylation that occurs on multiple TDP-43 sites
- Arginine 293 methylation allows for physiological TDP-43 liquid-liquid phase separation, while Serine 292/409/410 phosphorylation promotes TDP-43 aggregation
