Loss of prion protein control of glucose metabolism promotes neurodegeneration in model of prion diseases

Author summary Transmissible Spongiform Encephalopathies (TSEs), commonly named prion diseases, are caused by pathogenic prions PrPSc that trigger degeneration of neurons in the brain. Although PrPSc exerts its neurotoxicity by corrupting the function(s) of normal cellular prion protein (PrP(C)), our understanding of the mechanisms involved in prion diseases remains limited. There is still to date no medicine to fight against TSEs. The current study demonstrates that the deregulation of PrP(C) regulatory function towards glucose metabolism contributes to neurodegeneration in prion diseases. In the brain of prion-infected mice, PrPSc-induced overactivation of pyruvate dehydrogenase kinase 4 (PDK4) and downstream reduction in mitochondria pyruvate dehydrogenase (PDH) activity promote a metabolic shift from glucose oxidative degradation to pro-oxidant fatty acids beta-oxidation contributing to prion pathogenesis. The pharmacological inhibition of PDK4 extends the lifespan of prion-infected mice by rescuing normal glucose metabolism. This study opens up new avenues to design PDK4-based therapeutic strategies to combat TSEs. Corruption of cellular prion protein (PrP(C)) function(s) at the plasma membrane of neurons is at the root of prion diseases, such as Creutzfeldt-Jakob disease and its variant in humans, and Bovine Spongiform Encephalopathies, better known as mad cow disease, in cattle. The roles exerted by PrP(C), however, remain poorly elucidated. With the perspective to grasp the molecular pathways of neurodegeneration occurring in prion diseases, and to identify therapeutic targets, achieving a better understanding of PrP(C) roles is a priority. Based on global approaches that compare the proteome and metabolome of the PrP(C) expressing 1C11 neuronal stem cell line to those of PrPnull-1C11 cells stably repressed for PrP(C) expression, we here unravel that PrP(C) contributes to the regulation of the energetic metabolism by orienting cells towards mitochondrial oxidative degradation of glucose. Through its coupling to cAMP/protein kinase A signaling, PrP(C) tones down the expression of the pyruvate dehydrogenase kinase 4 (PDK4). Such an event favors the transfer of pyruvate into mitochondria and its conversion into acetyl-CoA by the pyruvate dehydrogenase complex and, thereby, limits fatty acids beta-oxidation and subsequent onset of oxidative stress conditions. The corruption of PrP(C) metabolic role by pathogenic prions PrPSc causes in the mouse hippocampus an imbalance between glucose oxidative degradation and fatty acid beta-oxidation in a PDK4-dependent manner. The inhibition of PDK4 extends the survival of prion-infected mice, supporting that PrPSc-induced deregulation of PDK4 activity and subsequent metabolic derangements contribute to prion diseases. Our study posits PDK4 as a potential therapeutic target to fight against prion diseases.