The key role of TDP-43 in amyotrophic lateral sclerosis propagation and the disease-modifying profile of CK-1 inhibitors

Abstract

Abstract Background Amyotrophic lateral sclerosis is a fatal neurodegenerative disease without any cure nor effective treatment to reverse its progression. The main hallmark of the disease is the nuclear protein TDP-43. It suffers different post-translational modifications leading to a lack of function in the nucleus and gain of toxicity in the cytoplasm. Previous reports indicated that pathogenic TDP-43 shows prion-like propagation in several different settings. With the aim of advancing therapeutics focused on the prevention of the propagation of TDP-43 pathology, we here study the potential role of pathogenic TDP-43 in immortalized lymphocytes from sporadic ALS patients Methods We used lymphoblastoid cell lines from sporadic ALS patients as source of pathogenic forms of TDP-43, and healthy cells (lymphoblasts, myoblasts or human neuroblastoma SH-SY5Y or osteosarcoma U2OS cell lines) as recipient cells to first investigate the seeding and spread of the TDP-43 proteinopathy. Furthermore, we have evaluated the potential of targeting TDP-43 phosphorylation by CK-1 inhibitors in preventing the propagation of the pathology. Results The results herein presented indicate that pathogenic TDP-43 forms are secreted to the extracellular medium of sporadic ALS lymphoblasts and could be transported by extracellular vesicles spreading TDP-43 pathology to healthy cells. Moreover, tunnelling nanotubes (TNTs) have been also discovered in sick cells transporting TDP-43 between the cells. Interestingly, targeting TDP-43 phosphorylation by an in-house designed benzothiazole-based CK-1 inhibitor, namely IGS2.7, was enough to stop cell-to-cell transmission in addition to its known effects on restoring phosphorylation levels, mislocalization and functionality of TDP-43 protein in patients-derived cells. Conclusions Our data show the key role of TDP-43 in cell-to-cell disease propagation in sporadic ALS lymphoblasts model and the relevant therapeutic role of CK-1 inhibitors, specifically the small heterocyclic molecule called IGS2.7, not only in restore the functional homeostasis of TDP-43 but also in avoiding the disease transmission. These outstanding data merits the translation of this small molecule to the clinical setting where all these results may be confirmed.