Objective: The hallmark of Parkinson’s Disease is motor dysfunction from the decline in dopaminergic cells in the substantia nigra (SN), leading to the development of L-DOPA as a standard therapeutic. Given the importance of dopamine to PD, we aim to profile the dopaminylation landscape utilizing both mouse models and postmortem human brain.

Background: Dopamine is historically believed to function exclusively via membrane bound receptors and play critical roles in neuronal networks that regulate cognition, reward, and motor learning, among other processes. More recently, dopamine has been shown by our lab to serve a chemical donor for a novel class of post-translational modification, termed dopaminylation – i.e. the covalent modification of proteins by dopamine. More specifically, our lab has identified the role of dopaminylation of histone 3 (H3Q5dop) as a novel histone modification regulating permissive transcription.

Method: Here, I utilized a novel chemical tagging approach, which covalently modifies dopaminylated proteins, coupled with western blotting to interrogate the alterations to H3Q5dop in postmortem human brain in PD compared to control. Additionally, I utilize an AAV viral approach to mimic the loss of H3Q5dop in the SN in mice and subsequently determine if the loss of H3Q5dop is sufficient to cause behavioral deficits via rotarod and wire hang.

Results: From postmortem human PD brain samples and aging mouse brain, we have identified a loss of H3Q5dop as well as the associated combinatorial mark H3K4me3Q5dop in the SN, without global reductions in H3K4me3 within the substantia nigra of subjects with PD (Fig 1a). Furthermore, in our dominant negative AAV mouse model, we have shown that the loss of H3Q5dop is sufficient to cause motor dysfunction (Fig 1b).

Conclusion: Interestingly, enhancing H3K4me3 transcription is known to have neuroprotective effects in PD rodent models, and the deposition of H3Q5dop stabilizes and potentiates H3K4me3 to increase permissive transcription. Given that we only observe a loss in the dual marker H3K4me3Q5dop and not total H3K4me3, we suspect the genes that the dopaminyl modification regulates are specific to PD pathophysiology. Thus, ongoing experiments aim to identify and compare molecular signatures for the mouse model and human PD postmortem brain. In conclusion, this is the first study to provide insights into a novel epigenetic marker of PD, highlighting new molecular mechanisms of disease.

Fig 1a

Fig 1b

References: Lepack AE, Werner CT, Stewart AF, Fulton SL, Zhong P, Farrelly LA, Smith ACW, Ramakrishnan A, Lyu Y, Bastle RM, Martin JA, Mitra S, O’Connor RM, Wang ZJ, Molina H, Turecki G, Shen L, Yan Z, Calipari ES, Dietz DM, Kenny PJ, Maze I. Dopaminylation of histone H3 in ventral tegmental area regulates cocaine seeking. Science. 2020 Apr 10;368(6487):197-201. doi: 10.1126/science.aaw8806. PMID: 32273471; PMCID: PMC7228137.

Fulton, S.L., Mitra, S., Lepack, A.E. et al. Histone H3 dopaminylation in ventral tegmental area underlies heroin-induced transcriptional and behavioral plasticity in male rats. Neuropsychopharmacol. 47, 1776–1783 (2022). https://doi.org/10.1038/s41386-022-01279-4

Stewart AF, Lepack AE, Fulton SL, Safovich P, Maze I. Histone H3 dopaminylation in nucleus accumbens, but not medial prefrontal cortex, contributes to cocaine-seeking following prolonged abstinence. Mol Cell Neurosci. 2023 Jun;125:103824. doi: 10.1016/j.mcn.2023.103824. Epub 2023 Feb 24. PMID: 36842545; PMCID: PMC10247417.

Stewart AF, Fulton SL, Durand-de Cuttoli R., et al. Hippocampal γCaMKII dopaminylation promotes synaptic-to-nuclear signaling and memory formation bioRxiv 2024.09.19.613951; doi: https://doi.org/10.1101/2024.09.19.613951

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MDS Abstracts - https://www.mdsabstracts.org/abstract/profiling-neural-protein-dopaminylation-in-parkinsons-disease/