TDP-43 Pathology and Prionic Behavior in Human Cellular Models of Alzheimer’s Disease Patients

Abstract

Alzheimer’s disease (AD) is a neurodegenerative disorder for which there is currently no effective treatment. Despite advances in the molecular pathology of the characteristic histopathological markers of the disease (tau protein and β-amyloid), their translation to the clinic has not provided the expected results. Increasing evidences have demonstrated the presence of aggregates of TDP-43 (TAR DNA binding protein 43) in the postmortem brains of patients diagnosed with AD. The present research is focused on of the study of the pathological role of TDP-43 in AD. For this purpose, immortalized lymphocytes samples from patients diagnosed with different severity of sporadic AD were used and the TDP-43 pathology was analyzed against controls, looking for differences in their fragmentation, phosphorylation and cellular location using Western blot and immunocytochemical techniques. The results revealed an increase in TDP-43 fragmentation, as well as increased phosphorylation and aberrant localization of TDP-43 in the cytosolic compartment of lymphocytes of patients diagnosed with severe AD. Moreover, a fragment of approximately 25 KD was found in the extracellular medium of cells derived from severe AD individuals that seem to have prion-like characteristics. We conclude that TDP-43 plays a key role in AD pathogenesis and its cell to cell propagation.

TTBK1 and CK1 inhibitors restore TDP-43 pathology and avoid disease propagation in lymphoblast from Alzheimer’s disease patients

“…In consonance with the fact that AD is not only a brain disorder but also presents several peripheral and systemic abnormalities ( Wojsiat et al, 2015 ; Esteras et al, 2016 ), we recently reported alterations in TDP-43 homeostasis, including increased TDP-43 phosphorylation, truncation and cytoplasmic accumulation in immortalised lymphocytes derived from AD patients. Moreover, we observed an enrichment of a 25 kDa TDP-43 fragment in the extracellular medium from AD cells, and found that conditioned medium from lymphoblasts of severe AD induced TDP-43 pathology in healthy cells ( Cuevas et al, 2022 ). Here, we report that targeting TDP-43 phosphorylation with different kinase inhibitors seems to stop disease propagation.…”

“…VNG1.47 and IGS2.7 have shown to be effective in the experimental treatment of lymphoblasts from ALS patients which are characterized by presenting TDP-43 hyperphosphorylated cytosolic aggregates, the main pathological hallmark of ALS ( Martinez-Gonzalez et al, 2020 ; Nozal et al, 2022 ). We have recently reported the presence of TDP-43 pathology in AD immortalized lymphocytes ( Cuevas et al, 2022 ). However, it was not explored whether small molecule protein kinases inhibitors would be able to modulate TDP-43 pathological hallmark in samples from AD patients.…”

“…We next investigated whether the reduction of this post-translational modification restores the nucleus-cytoplasmic functional balance of TDP-43 and reduces the aberrant F-actin cytoskeleton protrusions, reminiscent of tunnelling nanotubes or TNT-like structures that characterized these AD lymphoblasts ( Cuevas et al, 2022 ). With this aim, TDP-43 subcellular localisation and cytoskeleton morphology were analysed by immunofluorescence.…”

“…The prion-like properties of TDP-43 have been described in several TDP-43-linked diseases. We have recently documented the prionic behaviour of this protein in AD lymphoblasts throughout conditioned medium (CM) experiments which contains a 25 kDa TDP-43’s prionic fragment ( Cuevas et al, 2022 ). To further characterize the effect of these kinase inhibitors in preventing the TDP-43 cell-to-cell transmission, we performed different studies using CM from severe AD cases treated independently with the TTBK1 inhibitor VNG1.47 or CK1 inhibitor IGS2.7.…”

“…In previous studies, we have shown that human osteosarcoma U2OS cells treated with the conditioned medium from lymphoblasts from severe AD patients also showed increased phosphorylation and mislocalization of TDP-43 (Cuevas et al, 2022). Because of that, we selected this cellular model, with greater cytoplasm area than immortalized lymphocytes, to study a dynamic function of the receiving cells to explore whether this transmission of pathology altered other key cellular functions beyond TDP-43 homeostasis.…”