DEAD Box Helicase 24 Is Increased in the Brain in Alzheimer's Disease and App^N-LF Mice and Influences Presymptomatic Pathology

At the time of diagnosis, Alzheimer's disease (AD) patients already suffer from significant neuronal loss. The identification of proteins that influence disease progression before the onset of symptoms is thus an essential part of the development of new effective drugs and biomarkers. Here, we used an unbiased O-18 labelling proteomics approach to identify proteins showing altered levels in the AD brain. We studied the relationship between the protein with the highest increase in hippocampus, DEAD box Helicase 24 (DDX24), and AD pathology. We visualised DDX24 in the human brain and in a mouse model for A beta 42-induced AD pathology-App(NL-F)-and studied the interaction between A beta and DDX24 in primary neurons. Immunohistochemistry in the AD brain confirmed the increased levels and indicated an altered subcellular distribution of DDX24. Immunohistochemical studies in App(NL-F) mice showed that the increase of DDX24 starts before amyloid pathology or memory impairment is observed. Immunocytochemistry in App(NL-F) primary hippocampal neurons showed increased DDX24 intensity in the soma, nucleus and nucleolus. Furthermore, siRNA targeting of DDX24 in neurons decreased APP and A beta 42 levels, and the addition of A beta 42 to the medium reduced DDX24. In conclusion, we have identified DDX24 as a protein with a potential role in A beta-induced AD pathology.