Phase separation of C9orf72 dipeptide repeats perturbs stress granule metabolism

ABSTRACT: Liquid-liquid phase separation (LLPS) of RNA binding proteins underlies the formation of multiple membraneless organelles involved in RNA metabolism, including stress granules. Defects in stress granule homeostasis constitute a corner stone of ALS/FTLD pathogenesis. Phase separation of ALS-linked stress granule proteins has been shown to rely on hydrophobic interactions. Here we identify an active role for arginine-rich domains in these phase separations. Moreover, arginine-rich dipeptide repeats (DPRs) derived from C9orf72 hexanucleotide repeat expansions similarly undergo LLPS, and induce phase separation of a large set of proteins involved in RNA and stress granule metabolism. In the present proteomics experiment, we wondered which cellular proteins could interact with synthetic PR30 peptide. We took soluble HeLa cell lysate, to which we added increasing concentrations of PR30. The PR30 peptide spontaneously demixed, and could be separated from the solution by gentle centrifugation. Unexpectedly, the resulting pellet was largely resistant to washing steps, suggesting that PR induced the precipitation of different cellular proteins to the insoluble fraction. To see whether weak interactions could still be involved in the process, we also performed mild crosslinking with paraformaldehyde. Mass-spectroscopy (MS) analysis on both crosslinked and uncrosslinked samples identified 874 proteins that were detected and quantified in both conditions.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Line Cell, Hela Cell

DISEASE(S): Amyotrophic Lateral Sclerosis

SUBMITTER: Impens Francis  

LAB HEAD: Ludo Van Den Bosch

PROVIDER: PXD005509 | Pride | 2017-04-26

REPOSITORIES: Pride