The Study That Brichos Domain Of Prosurfactant Protein C Inhibited FUS-LC Amyloid Aggregation

Fused in Sarcoma（FUS）is a nuclear RNA binding protein that spontaneously forms phase separation in vitro and further condenses to form pathological fibers causing neurodegenerative diseases such as amyotrophic lateral sclerosis.Currently,there are few studies on amyloid fibril inhibitors such as FUS-LC.They regulate FUS-LC dynamic assembly through in vivo post-translational modifications that interfere with the stability in theβ-sheet structure.Prosurfactant Protein C（ProSP-C）of Brichos domain,a molecular chaperone protein inhibitor,exists in vivo to target theβ-sheet fold structure and chaperones of aromatic residues in Aβ40 and Aβ42 to prevent the formation of amyloid fibrils and inhibit their toxicity.It has shown that the N-terminal low-complexity domain（LC）of FUS can form amyloid fibrills.Residues 50-65 in the LC domain stabilize theβ-sheet structure in pathological fibers and regulate FUS-LC particle assembly and inclusions formation in vitro and in vivo.This study mainly investigated the binding effect of ProSP-C Brichos and FUS-LC.The inhibitory effect on fibers further explored the new inhibitory mechanism of FUS-LC amyloid fibrils.The article successfully constructed p ET-28a-Brichos-His recombinant plasmid and expressed purified recombinant ProSP-C Brichos with high purity.Through thioflavin T kinetic monitoring experiments,atomic force microscopy experiments and other methods,we found that FUS-LC and ProSP-C Brichos significantly co-localized in vitro and effectively maintained the amorphous aggregation of FUS-LC instead of the FUS-LC fibers.Additionally,ProSP-C Brichos prolonged the lag period of fibril formation in a concentration-dependent manner in long-term culture.Subsequently,our investigation revealed that ProSP-C Brichos inhibited the fibers formation of R₂in the core region and kept in an oligomeric state.In addition,we showed that ProSP-C Brichos bound to the aromatic residues（tyrosine）and phosphorylation site（serine）of FUS-LC through hydrogen bonding,disrupting the hydrogen bonding network andπ-πinteractions between tyrosine residues that remain stable in the FUS-LC fibril structure,thereby maintaining the oligomeric morphology of FUS-LC to prolong its fibril formation.ProSP-C Brichos inhibiting FUS-LC provides a possible inhibitory mechanism for reversible amyloid fibril and a new study idea for exogenous inhibitors of molecular chaperone type like.