Probing the Logic of DnaJB6 Oligomerization

Abstract

Protein misfolding and aggregation, a characteristic molecular phenotype of neurodegenerative disease, is mediated by a class of proteins called molecular chaperones. One such protein, DnaJB6, potently suppresses the aggregation of polypeptides such as amyloid-β and tau and has been observed to self-oligomerize, but the connection between these properties is unknown. Previous work to understand DnaJB6 has not elucidated this connection, in part because the dynamic nature of these oligomers makes them difficult to analyze by conventional techniques. I hypothesize that DnaJB6 oligomers serve as inactive reservoirs from which dimers, the active subunit, dissociate upon binding to misfolding client and engage Hsp70s to facilitate processing. To test this hypothesis, I have generated point variants of DnaJB6 to perturb oligomerization and tested their biophysical properties and biochemical activity. My analysis demonstrates that aromatic residues in the disordered region are critical for oligomerization and affirms my hypothesis that smaller assemblies of the chaperone are responsible for its anti-aggregation activity. This work enhances our foundational biophysical understanding of DnaJB6, which serves as a basis for the development of DnaJB6-inspired therapeutics to combat neurodegenerative disease.