Perturbation of O-GlcNAcylation, a nutrient sensing pathway, has been demonstrated in human Alzheimer's disease (AD) brains, and inhibition of O-GlcNAcase (OGA) has been shown effective in inhibiting tau phosphorylation in animal models. This proposal focusses on the protein O-GlcNAcylation and its impact on neurological function and protein homeostasis. One of the key proteins we focus on is ?-synuclein accumulation which occurs prominently in Alzheimer's disease (AD), Dementia with Lewy Bodies (DLB) and Parkinson's disease (PD), however, whether O-GlcNAcylation is involved in ?-synuclein accumulation in vivo in mammalian models has not been investigated. This is important because targeting ?-synuclein is actively pursued as a therapeutic strategy in treating neurodegenerative disease. In our preliminary studies, we have found that inhibition of OGA increased autophagosomal and ?-synuclein accumulation and attenuated autophagic flux in primary neurons, cautioning a potential detrimental effect of inhibiting OGA, even though it was effective in decreasing tau phosphorylation. In vivo, we have shown that key proteins involved in protein trafficking are dynamically O-GlcNAcylated. In the proposed studies, we will test the hypothesis that sustained increase in O-GlcNAc causes neurological dysfunction, thereby contributing to the pathogenesis of AD and DLB. We have built a strong research team with expertise in O-GlcNAc biology, cutting-edge techniques of tag-mass spectrometry and stoichiometry of O-GlcNAc modification, autophagy, and mouse models of tissue specific OGA deficiencies. This study will: 1) Determine the impact of increased O-GlcNAc levels on neurological function in vivo. 2) Determine the mechanisms through which O-GlcNAc modification impacts neurodegeneration. The successful completion of these studies will establish a role for O-GlcNAcylation in regulating neurodegeneration, and provide new mechanistic understanding of O-GlcNAc regulation of endolysosomal function, which will guide strategies for neuroprotection. Completion of the proposed study will encourage future work introducing O- GlcNAcylation site mimetic peptide as competitive inhibitors to test the potential benefits of preventing detrimental O-GlcNAcylation while preserving beneficial O-GlcNAcylation. This proposal is directed at addressing the urgent and pressing need to understand basic mechanisms of proteotoxicity in neurons and is responsive to PAR-15-357 Understanding Alzheimer's Disease in the Context of the Aging Brain (R01).
Our work will focus on novel regulatory mechanisms of endolysosomal function by O- GlcNAcylation in novel transgenic mouse models. We anticipate that the successful completion of the proposed studies will open up new avenues for the development of novel therapeutics for the treatment of DLB, AD and PD.
