REGULATION OF ER-STRESS ACTIVATED UPR KINASE PERK IN NEURODEGENERATIVE DISEASES
Several clinically unrelated neurodegenerative disorders, termed conformational diseases, are character-ized by a common pathophysiology that involves aggregation and accumulation of misfolded proteins. All ofthese diseases activate cell stress signaling pathways, mainly the endoplasmic reticulum (ER) stress-inducedunfolded protein response (UPR) pathway. In particular, the proximal UPR kinase, PERK, is abnormally activein Alzheimer's disease (AD), Progressive Supranuclear Palsy (PSP) and Frontal Temporal Dementia (FTD)-affected brain regions. Encouragingly, pharmacological inhibition of PERK activity appears to restore neuro-logical deficits associated with these disorders in preclinical mouse models, including loss of cognition andmemory. However, current PERK inhibitors are toxic, necessitating the need to define the precise mecha-nisms that regulate PERK activity in these degenerative processes. We find that in addition to luminal regula-tion, PERK activity is enhanced by an increase in cytosolic Ca2+. Surprisingly, our super resolution microscopymeasurements indicate the majority of PERK molecules may require only transient dimerization for activation.Our central hypothesis is that dysregulation of PERK activity can lead to neurodegeneration. In Aim 1, we willtest the hypothesis that PERK is activated by the transient formation of dimers, while PSP-associated PERKcoding variants suppress PERK inactivation. In Aim 2, we will test the hypothesis that leakage of ER Ca2+leading to PERK-calcineurin binding enhances PERK autophosphorylation by stabilizing dimer formation.Successful completion of Aims 1 and 2 will precisely determine luminal and cytosolic regulation of PERK undernormal and pathologic conditions. In Aim 3, we will test the hypothesis that PERK dimerization in human braincells and tissue from AD patients is increased by ER stress, soluble mutant tau oligomers and/or increases incytosolic Ca2+. We will also measure PERK activation in a neurodegenerative mouse model. Successful com-pletion of Aim 3 will validate our in vitro data in neurodegenerative pathophysiology in vivo. Super resolutionmicroscopy, molecular, biochemical and mouse genetic approaches will be used to fulfil these aims. Datagenerated from this proposal will potentially impact all conformational diseases and identify targets for rapidand integrated therapy.