A Shotgun Proteomics Approach Reveals a New Toxic Role for Alzheimer's Disease Abeta Peptide: Spliceosome Impairment

Proteomic changes have been described in many neuro-
degenerative diseases, including Alzheimer's disease (AD). However, the early
events in the onset of the pathology are yet to be fully elucidated. A cell model
system in which LAN5 neuroblastoma cells were incubated for a short time
with a recombinant form of A?42 was utilized. Proteins extracted from these
cells were subjected to shotgun proteomics analysis by LTQ-Orbitrap-MS
followed by label-free quantitation. By bioinformatics tools we found that the
most significant of those found to be up-regulated were related to cytoskeletal
dynamics (Rho related) and membrane-related processes. The most significant
of the down-regulated proteins were hnRNP-related. In particular, hnRNPs
involved in ribosomal biogenesis and in splicing were down-regulated. The
latter of these processes stood out as it was highlighted ubiquitously and with
the highest significance in the results of every analysis. Furthermore, our
findings revealed down-regulation at every stage of the splicing process
through down-regulation of every subunit of the spliceosome. Dysregulation of the spliceosome was also confirmed using a
Western blot. In conclusion, these data suggest dysregulation of the proteins and processes identified as early events in
pathogenesis of AD following A? accumulation.