Project Details
Projekt
Chaperone-mediated regulation of liquid to solid phase transition of Huntingtin (HTT)
Subject Area
Biochemistry
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 545039200
Huntingtin (HTT) contains a polyglutamine stretch that is encoded by the first exon of the huntingtin gene and renders the HTT protein aggregation prone. HTT can form reversible liquid-like assemblies that can convert into solid-like assemblies with fibrillar structure. The phase transition is regulated by the pathogenic polyQ stretch as well as by the polyQ-flanking poly-proline (polyP) domain. We have recently demonstrated that the trimeric chaperone complex Hsc70, DNAJB1 and Apg2 can suppress HTT aggregation and can also disaggregate amyloid HTT fibrils. The same chaperone complex can co-condense with HTT and suppress the solidification of HTT that may precede amyloid fibril formation. DNAJB1 initiates binding to HTT, and using crosslinking mass spectrometry, we have mapped the interface of DNAJB1 and HTT. DNAJB1 binds with a distinct motif within its C-terminal domain to the second proline stretch of the proline rich domain (PRD) of HTT. The PRD represents not only a new binding site for chaperones, but also a domain that regulates the condensation and aggregation propensity of HTT. In this project, the Kirstein and Liu groups will explore how DNAJB1 together with Hsc70 and Apg2 regulates the folding landscape of HTT from soluble monomer to condensates and fibrils and in reverse in the disaggregation process. We will further compare the mechanism of DNAJB1 to related J-domain proteins that work in a Hsc70-dependent and -independent manner and have also been implicated in the regulation of aberrant folding of HTT. Janine Kirstein is an expert in the biochemical analysis of molecular chaperones and HTT and can study the aberrant folding of HTT and its regulation by molecular chaperones in vitro as well as in the animal model C. elegans. Fan Liu contributes her expertise in cross-linking mass spectrometry and proteomic analyses to map the transient interactions between chaperones and HTT in its soluble, condensed and aggregated state. Together, they can resolve how chaperones and chaperone complexes can bind to and remodel different conformational entities of the amyloid protein HTT. Knowledge of these interactions could help to develop therapeutic strategies for Huntington’s disease (HD) to suppress the accumulation of distinct HTT conformations.
DFG Programme
Research Units
