The Role of SUMOylation and Ubiquitination in Brain Ischaemia: Critical Concepts and Clinical Implications

Brain ischaemia is a severe form of metabolic stress that activates a cascade of pathological events involving many signalling pathways.Modulation of these pathways is largely mediated by post-translational modifications (PTMs).Indeed, PTMs can rapidly modify pre-existing proteins by attaching chemical or polypeptide moieties to selected amino acid residues, altering their functions, stability, subcellular localizations, or interactions with other proteins.Subsequently, related signalling pathways can be substantially affected.Thus, PTMs are widely deployed by cells as an adaptive strategy at the front line to efficiently cope with internal and external stresses.Many types of PTMs have been identified, including phosphorylation, O-GlcNAcylation, small ubiquitin-like modifier (SUMO) modification (SUMOylation), and ubiquitination.All these PTMs have been studied in brain ischaemia to some extent.In particular, a large body of evidence has demonstrated that both global SUMOylation and ubiquitination are massively activated after brain ischaemia, and this activation may play a critical role in defining the fate and function of cells in the post-ischaemic brain.The goal of this review will be to summarize the current findings on SUMOylation and ubiquitination in brain ischaemia and discuss their clinical implications. SUMOylation in brain ischaemia/ strokeSUMOylation SUMOylation is a post-translational modification in which a member of the SUMO family of proteins is conjugated to lysine residues in target proteins.SUMOylation was first implicated in nuclear function pathways (Matunis et al., 1996;