Investigation of the biochemical and cellular properties of an ALS-linked NEK1 variant

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that is associated with various genes, among which NIMA-related kinase 1 (NEK1) has attracted attention in recent studies. Current research aims to comprehend one of the most common mutants, which we named truncated NEK1 (tNEK1), and its molecular basis in the context of ALS progression. To be more precise, this study focuses on ALS-related tNEK1 and its link between the post-translational modification process SUMOylation and promyelocytic leukemia nuclear bodies (PML NBs). Building upon the insight gained from the preliminary findings of our lab, we illustrated that in addition to its tendency to aggregate, which is further verified in this study, the mutant tNEK1 recruits a wild-type form of NEK1 to the aggregates. This data highlights one of the potential reasons for NEK1 haploinsufficiency. Furthermore, the cytotoxicity of tNEK1 negatively influences cell viability, implying cell death induction in the presence of aggregation-prone tNEK1. Surprisingly, our observation of SUMO-positive tNEK1 aggregates directed us to discover NEK1 hyper-SUMOylation, an adverse response to degrade toxic protein by PML NBs-SUMO mediated proteasomal degradation. The finding is confirmed in detail by the combined results from previous data and our current results. Even though the possibility of using the PML-inducing drug IFN to treat tNEK1-driven ALS was previously demonstrated, its effectiveness was further examined within this thesis. To summarize, this thesis covers our investigation of the cellular basis of tNEK1 and its potential therapeutic intervention in cell-based systems.