Abstract
Protein aggregation critically affects cell viability in neurodegenerative diseases, but whether this also occurs in ischemic brain injury remains elusive. Prior studies report the post-ischemic aggregation of ubiquitin, small ubiquitin-related modifier (SUMO) and ribosomes, however whether other proteins are also affected is unknown. Here we employed a proteomic approach to identify the insoluble, aggregated proteome after cerebral ischemia. Mice underwent transient middle cerebral artery occlusion or sham-surgery. After 1-hour reperfusion, prior to apparent brain injury, mice were sacrificed and detergent-insoluble proteins were obtained and identified by nanoLC-MS/MS. Naturally existing insoluble proteins were determined in sham controls and aggregated proteins after cerebral ischemia/reperfusion were identified. Selected aggregated proteins found by proteomics were biochemically verified and aggregation propensities were studied during ischemia with or without reperfusion. We found that ischemia/reperfusion induces the aggregation of RNA-binding and heat-shock proteins, ubiquitin, SUMO and other proteins involved in cell signalling. RNA-binding proteins constitute the largest group of aggregating proteins in ischemia. These include TDP43, FUS, hnRNPA1, PSF/SFPQ and p54/NONO, all of which have been linked to neurodegeneration associated with amyotrophic lateral sclerosis and frontotemporal dementia. The aggregation of neurodegeneration-related disease proteins in cerebral ischemia unveils a previously unappreciated molecular overlap between neurodegenerative diseases and ischemic stroke.