Sustained eIF5A hypusination at the core of brain metabolic dysfunction in TDP-43 proteinopathies

点击翻译按钮获取中文摘要

PROJECT SUMMARY/ ABSTRACT TAR DNA-binding protein 43 (TDP-43) pathology is associated with clinical dementia and occurs in more than half of clinically diagnosed Alzheimer’s disease (AD) patients (1, 2). The discovery of limbic-predominant TDP-43 encephalopathy (LATE) emphasized the importance of age-related TDP-43 proteinopathy, with or without co-morbid AD pathological hallmarks. The lack of disease-modifying agents against TDP-43 pathology creates an urgent need to identify novel therapeutic pathways against TDP-43 proteinopathy. Interestingly, regional disruption of glucose uptake and utilization is linked to the progression of AD neuropathology (3-5), and yet, there is no consensus on the effect of TDP-43 on glucose and energy homeostasis in the diseased brain (6). This proposal will address this significant gap in knowledge by studying the impact of the eIF5A hypusination pathway on the brain’s metabolic state in TDP-43 pathology. eIF5A is an initiation/elongation factor and the only protein undergoing hypusination (eIF5AHyp). Deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase (DOHH) activity convert a single lysine to a hypusine moiety. Our feasibility data finds that TDP-43 pathology in AD brain and TDP-43 mouse models induces DHS expression and hypusine levels. Additionally, we show that enhanced hypusination exacerbates TDP-43 pathology, dysregulates brain glucose homeostasis and exerts mitochondrial bioenergetic defects. Our central hypothesis states that DHS-targeted strategies reducing hypusine levels will ameliorate TDP-43 neuropathogenesis by restoring brain glucose metabolism and mitochondrial bioenergetics, upstream of cognitive decline and neurodegeneration. In Aim 1, we will establish how conditional deletion of the DHS (DHSko) in the adult forebrain of the TDP-43 transgenic mouse model will affect the brain metabolic transcriptomic profile via NanoString analysis and determine biological signatures that define the eIF5AHyp - TDP-43 phenotype. We will also utilize the CNS-Met Metabolomics Core to measure brain metabolite levels, while biochemically determining metabolic proteins, enzymes, and TDP-43 pathology. We will further elucidate how DHSko can rescue LTP, cognitive performance, and neurodegeneration associated with TDP-43 phenotype of a novel TDP-43 animal model. In Aim 2, we will define the role of eIF5AHyp on the mitochondrial bioenergetics of neurons and astrocytic-responsive neurons. We will establish how DHS inhibition rescues mitochondrial bioenergetics and restores metabolite balance in primary cells. We will also determine the cellular and mitochondrial TDP-43 accumulation and mitochondrial structure integrity. Overall, the proposed studies will provide evidence that the eIF5AHyp pathway in the TDP-43 phenotype is upstream of irreversible stages of dementia. It also offers the first detailed mechanisms of how reducing hypusine restores glucose dysregulation and mitochondrial dysfunction, maintaining neuro-astrocytic support and healthy neuronal activity, while rescuing the pathological phenotype in animal models of TDP-43 proteinopathy.