TDP-43 aggregation mirrors TDP-43 knockdown, affecting the expression levels of a common set of proteins

Abstract

TDP-43 protein plays an important role in regulating transcriptional repression, RNA metabolism, and splicing. Typically it shuttles between the nucleus and the cytoplasm to perform its functions, while abnormal cytoplasmic aggregation of TDP-43 has been associated with neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). For the purpose of this study we selected a set of proteins that were misregulated following silencing of TDP-43 and analysed their expression in a TDP-43-aggregation model cell line HEK293 Flp-in Flag-TDP-43-12x-Q/N F4L. Following TDP-43 sequestration in insoluble aggregates, we observed higher nuclear levels of EIF4A3, and POLDIP3β, whereas nuclear levels of DNMT3A, HNRNPA3, PABPC1 and POLDIP3α dropped, and cytoplasmic levels of RANBP1 dropped. In addition, immunofluorescence signal intensity quantifications showed increased nuclear expression of HNRNPL and YARS, and downregulation of cytoplasmic DPCD. Furthermore, cytoplasmic levels of predominantly nuclear protein ALYREF increased. In conclusion, by identifying a common set of proteins that are differentially expressed in a similar manner in these two different conditions, we show that TDP-43 aggregation has a comparable effect to TDP-43 knockdown.