Why Pressure is Bad for Your Brain? Hydrostatic Pressure Promotes Aggregation of Alpha-Synuclein in Cells

Abstract

Neurodegenerative diseases such as Alzheimer's and Parkinson's are characterized by the presence of Lewy bodies which are plaques of aggregated proteins found post-mortem in brains of patients. The neurodegenerative plagues associated with Parkinson's disease are largely composed of the protein α-synuclein. A-Synuclein is a small cytoplasmic protein found in central nervous system of vertebrates. Despite intensive studies, its precise role in cells is unknown. Changes in α-synuclein oligomerization are thought to give rise to nucleation of neurodegenerative plaques. We have proposed previously that loss of binding partners caused by environmental factors, such as oxidative stress induces α-synuclein oligomerization. Here, we investigated the effect of hydrostatic pressure on the aggregation of α-synuclein in cultured neuronal cells. We applied high hydrostatic pressure to cells in suspension for 1h and plated them in full growth medium for 24h to allow recovery and ensure that experiments are performed on live cells. Using western-blot and number and brightness analysis of fluorescence fluctuation intensities, we found that hydrostatic pressure promotes aggregation of α-synuclein in PC12 and SK-N-SH cells. We then tested whether aggregation is associated with the loss of binding partners, such as phospholipase Cβ1. Western blot analysis indicates that hydrostatic pressure reduces the amount of PLCβ1, but not α-synuclein in neuronal cells. Using Forster resonance energy transfer between GFP-PLCβ1 and mCherry-α-synuclein we found that increased pressure reduces the association between PLCβ1 and α-synuclein. These studies suggest that pressure induces cell damage that results in the loss of α-synuclein binding partners and can promote α-synuclein aggregation.This work was supported by PSC-CUNY 45 to UG and NIH GM116178 to SS.