The Inhibition of LSD1 Via Sequestration Contributes to Tau-Mediated Neurodegeneration
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The inhibition of LSD1 via sequestration contributes to tau-mediated neurodegeneration Amanda K. Engstroma, Alicia C. Walkera, Rohitha A. Moudgala, Dexter A. Myricka, Stephanie M. Kylea, Yu Baia, M. Jordan Rowleyb, and David J. Katza,1 aDepartment of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322; and bDepartment of Genetics, Cell Biology, and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198 Edited by Michele Pagano, HHMI and New York University School of Medicine, New York, NY, and accepted by Editorial Board Member Gail Mandel October 1, 2020 (received for review July 2, 2020) Tauopathies are a class of neurodegenerative diseases associated AD cases, but not other neurodegenerative diseases, such as with pathological tau. Despite many advances in our understand- Parkinson’s disease or amyotrophic lateral sclerosis (ALS) cases. ing of these diseases, the direct mechanism through which tau Consistent with this overlap, we observed LSD1 protein mis- contributes to neurodegeneration remains poorly understood. Pre- localized to cytoplasmic NFTs, but not associated with Aβ plaques viously, our laboratory implicated the histone demethylase LSD1 in in AD cases or Lewy bodies of α-synuclein in Parkinson’sdisease tau-induced neurodegeneration by showing that LSD1 localizes to cases (26). In control cases, LSD1 remains strictly confined to the pathological tau aggregates in Alzheimer’s disease cases, and that it nucleus (26), due to its well-defined nuclear localization signal is continuously required for the survival of hippocampal and cortical (27). These data highlight the requirement for LSD1 in neuro- neurons in mice. Here, we utilize the P301S tauopathy mouse model nal survival and suggest that the nuclear function of the histone to demonstrate that pathological tau can exclude LSD1 from the demethylase LSD1 could be disrupted by mislocalization to nucleus in neurons. In addition, we show that reducing LSD1 in pathological tau. these mice is sufficient to highly exacerbate tau-mediated neuro- To investigate how LSD1 may contribute to tau-mediated neu- degeneration and tau-induced gene expression changes. Finally, rodegeneration, we utilized the PS19 P301S tauopathy mouse we find that overexpressing LSD1 in the hippocampus of tauopathy model (hereafter referred to as PS19 Tau). PS19 Tau mice express mice, even after pathology has formed, is sufficient to significantly a P301S mutated form of the human tau protein, originally iden- delay neurodegeneration and counteract tau-induced expression tified in a frontotemporal dementia with parkinsonism (FTDP-17) NEUROSCIENCE changes. These results suggest that inhibiting LSD1 via sequestra- patient, driven by the prion promoter throughout the nervous tion contributes to tau-mediated neurodegeneration. Thus, LSD1 is system (28). When expressed in mice, the P301S tau protein is a promising therapeutic target for tauopathies such as Alzheimer’s prone to hyperphosphorylation and somatodendritic aggregation, disease. without the presence of Aβ plaques. PS19 Tau mice develop a heavy pathological tau burden and have been well characterized LSD1 | neurodegeneration | tauopathy | Alzheimer’s disease | epigenetics for the temporal progression of tau pathology and disease-related phenotypes (29, 30). However, the mechanism of neuronal cell auopathies such as corticobasal degeneration, progressive death caused by pathological tau is still unknown. Tsupranuclear palsy, and frontotemporal lobar degeneration Here, we provide functional data that the inhibition of LSD1 with tau inclusions are neurodegenerative diseases pathologically function contributes to tau-induced neurodegeneration. We dem- defined by different forms of tau-positive intraneuronal deposits onstrate in PS19 Tau mice that pathological tau sequesters LSD1 (1–5). In addition to these primary tauopathies, neuropathological in the cytoplasm of neurons throughout the brain. This results in observations of postmortem Alzheimer’s disease (AD) brains show depletion of LSD1 from the nucleus. Additionally, we provide the presence neurofibrillary tangles (NFTs) of hyperphosphorylated genetic and molecular evidence that pathological tau contributes to tau protein, as well as plaques containing β-amyloid (Aβ)peptide neurodegeneration by disrupting LSD1. Finally, we show that (6–9). AD is the leading cause of age-related dementia, resulting overexpressing LSD1 in hippocampal neurons is sufficient to from neuronal cell death in the frontal and temporal cortices, as well as the hippocampus (7). As dementia progresses, the spatial Significance pattern of tau pathology highly correlates with the level of cog- nitive impairment (10–13). In addition, Aβ oligomers and/or pla- We have made the discovery that pathological tau functions ques can enhance tau pathology in various mouse models (14, 15), through the histone demethylase LSD1 in the Alzheimer’s dis- and there is increasing evidence that accumulation of Aβ plaques ease pathway. Thus, we have identified a mechanism that links can contribute to tau pathology (3, 16, 17). The most well-defined tau to the downstream neuronal dysfunction pathways. This physiological role of tau is in stabilizing microtubules, particularly step can potentially be targeted therapeutically, after the on- in neuronal axons (2). However, in the pathological state, tau set of dementia symptoms, to block the progression of de- becomes aberrantly phosphorylated (2, 18, 19), truncated (1, 4), mentia in Alzheimer’s disease patients. and aggregates into oligomers and larger insoluble filaments (20, 21). This pathology is thought to trigger synaptic loss, dramatic Author contributions: A.K.E. and D.J.K. designed research; A.K.E., A.C.W., R.A.M., S.M.K., Y.B., and D.J.K. performed research; A.K.E., A.C.W., R.A.M., D.A.M., S.M.K., Y.B., M.J.R., genome-wide expression changes, increased inflammatory re- and D.J.K. analyzed data; and A.K.E. and D.J.K. wrote the paper. – sponse, and neuronal cell death (22 25). These data suggest that The authors declare no competing interest. pathological tau may be a downstream mediator of the neurotoxic This article is a PNAS Direct Submission. M.P. is a guest editor invited by the effects leading to neuronal degeneration in AD. Editorial Board. Previously, in the Katz lab, we demonstrated that deleting the This open access article is distributed under Creative Commons Attribution-NonCommercial- histone demethylase Lsd1 in adult mice leads to significant neu- NoDerivatives License 4.0 (CC BY-NC-ND). ronal cell death in the hippocampus and cortex with associated 1To whom correspondence may be addressed. Email: [email protected]. learning and memory defects (26). In this mouse model, loss of This article contains supporting information online at https://www.pnas.org/lookup/suppl/ Lsd1 induces genome-wide expression changes that significantly doi:10.1073/pnas.2013552117/-/DCSupplemental. overlap with those observed in the brains of postmortem human First published November 2, 2020. www.pnas.org/cgi/doi/10.1073/pnas.2013552117 PNAS | November 17, 2020 | vol. 117 | no. 46 | 29133–29143 Downloaded by guest on September 29, 2021 +/+ suppress neuronal cell death even after pathological tau has protein levels compared to Lsd1 littermates. It is possible that formed. We propose that pathological tau contributes to neuronal this is due to some type of compensation because LSD1 is being cell death by sequestering LSD1 in the cytoplasm, depleting the sequestered. Nevertheless, consistent with the reduction in LSD1 Δ/+ Δ/+ nuclear pool of LSD1 that is required for neuronal survival. that we observe in Lsd1 mice, PS19;Lsd1 mice have a similar 14% reduction in transcript levels (SI Appendix,Fig.S2B)anda Results 31% reduction in protein levels (SI Appendix, Fig. S2 C and D) Tau Pathology Depletes LSD1 from the Nucleus in the PS19 Tau Mouse compared to PS19 Tau littermates. This enables us to directly assess Model. Previously, we showed in human AD cases that LSD1 the effect of reducing LSD1 on tau-induced neurodegeneration. In protein inappropriately colocalizes with NFTs in the cell body of addition, all genotypes were born at normal Mendelian ratios with hippocampal and cortical neurons, while in unaffected controls equal male/female ratios. LSD1 was properly localized exclusively to the nucleus (26). To determine if reducing LSD1 protein levels accelerates tau- However, because neurons in AD cases with intracellular NFTs induced depletion of LSD1 from the nucleus, we analyzed lo- Δ/+ presumably die and are cleared, it was difficult to determine calization of LSD1 in PS19;Lsd1 mice versus PS19 Tau con- whether tau prevents LSD1 from localizing to the nucleus in a trols. When one copy of Lsd1 was removed from PS19 Tau mice, dying neuron. To address this possibility, we performed LSD1 there was a significant decrease in the nuclear localization of immunofluorescence on 12-mo-old PS19 Tau mice, which have LSD1 compared to PS19 Tau mice (Fig. 1 J–N), accompanied by significant tau pathology (28). Because PS19 Tau mice undergo an increase in the number of cells that have LSD1 in both the neurodegeneration over a shortened period, there are more nucleus and the cytoplasm (Fig. 1 J–N). This suggests that re- neurons undergoing neurodegeneration at any given time point. ducing LSD1 enables tau to accelerate the depletion of LSD1. Thus, we reasoned that it may be possible to observe LSD1 de- Since lowering LSD1 accelerates tau-induced depletion of LSD1 pletion from the nucleus. Similar to what we observe in humans, from the nucleus, we determined if this acceleration exacerbates LSD1 protein in 12-mo-old wild-type mice was strictly localized the progression of disease, by analyzing survival, paralysis, neuro- A–C to the nucleus of neurons in the cerebral cortex (Fig. 1 ) and degeneration, and genome-wide gene expression changes in SI Appendix A–C Δ/+ Δ/+ the hippocampus ( , Fig. S1 ). This was expected PS19;Lsd1 mice versus PS19 Tau controls. As expected, Lsd1 since LSD1 has a well-defined nuclear localization signal (27). mice had normal survival (Fig. 2A). In contrast, PS19 Tau mice had However, in 12-mo-old PS19 Tau mice, LSD1 protein was se- a reduced overall survival (Fig.