OGA Inhibition Alters Energetics and Nutrient Sensing in Alzheimer’s Disease Cytoplasmic Hybrids

Article type: Research Article

Authors: Flax, Jarrod^a | Wilkins, Heather M.^{a; b} | Miller, Reegan^a | Griffith, Sarah^a | Cork, Gentry K.^a | Qiang, Amy^a | Thompson, Jeffrey^c | Swerdlow, Russell H.^b | Slawson, Chad^{a; *}

Affiliations: [a] Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, USA | [b] Department of Neurology, University of Kansas Medical Center, Kansas City, KS, USA | [c] Department of Biostatistics and Data Science, University of Kansas Medical Center, Kansas City, KS, USA

Correspondence: [*] Correspondence to: Chad Slawson, University of Kansas Medical Center, 3901 Rainbow Blvd. Kansas City, KS 66160, USA. Tel.: +1 913-945-6468; E-mail: cslawson@kumc.edu.

Abstract: Background:Alzheimer’s disease (AD) features reductions in key bioenergetic fluxes and perturbed mitochondrial function. Cytoplasmic hybrids (cybrids) generated through the transfer of AD subject mitochondria to mtDNA-depleted SH-SY5Y neuroblastoma cells recapitulate some of these features in an in vitro setting. Objective:For this study, we used the AD cybrid model to assess the impact of a nutrient-excess like-state via increasing O-GlcNAcylation on whole cell and mitochondrial homeostasis. Methods:We induced increased O-GlcNAc by treating AD and control cybrid cell lines with Thiamet G (TMG), an inhibitor of the O-GlcNAcase enzyme that mediates removal of the nutrient-dependent O-GlcNAc modification. Results:Relative to control cybrid cell lines, AD cybrid lines showed a blunted response to TMG-induced O-GlcNAcylation. At baseline, AD cybrid cell line mitochondria showed partial activation of several proteins that help maintain bioenergetic homeostasis such as AMP-Regulated Kinase suggesting that AD mitochondria initiate a state of nutrient stress promoting energetic compensation; however, this compensation reduces the capacity of cells to respond to additional nutrient-related stresses such as TMG treatment. Also, TMG caused disruptions in acetylation and Sirtuin 3 expression, while lowing total energetic output of the cell. Conclusion:Together, these findings suggest that modulation of O-GlcNAc is essential for proper energetic function of the mitochondria, and AD mitochondrial capacity to handle nutrient-excess is limited.

Keywords: Acetylation, cybrids, mitochondria, O-GlcNAc, O-GlcNAcase (OGA), O-GlcNAc transferase (OGT), oxidative phosphorylation, SIRT3

DOI: 10.3233/JAD-200996

Journal: Journal of Alzheimer's Disease, vol. 78, no. 4, pp. 1743-1753, 2020