PT - JOURNAL ARTICLE AU - Shannon McMahon AU - Steven Bergink AU - Harm H. Kampinga AU - Heath Ecroyd TI - DNAJB chaperones inhibit aggregation of destabilised proteins via a C-terminal region distinct from that used to prevent amyloid formation AID - 10.1101/2020.10.08.326280 DP - 2020 Jan 01 TA - bioRxiv PG - 2020.10.08.326280 4099 - http://biorxiv.org/content/early/2020/10/08/2020.10.08.326280.short 4100 - http://biorxiv.org/content/early/2020/10/08/2020.10.08.326280.full AB - Disturbances to protein homeostasis (proteostasis) can lead to protein aggregation and inclusion formation, processes associated with a variety of neurodegenerative disorders. DNAJBs are molecular chaperones previously identified as potent suppressors of disease-related protein aggregation. In this work, we over-expressed a destabilised isoform of firefly luciferase (R188Q/R261Q Fluc; FlucDM) in cells to assess the capacity of DNAJBs to inhibit inclusion formation. Co-expression of all DNAJBs tested significantly inhibited the intracellular aggregation of FlucDM. Moreover, we show that DNAJBs suppress aggregation by supporting the Hsp70-dependent degradation of FlucDM via the proteasome. The serine-rich stretch in DNAJB6 and DNAJB8, essential for preventing fibrillar aggregation, is not involved in the suppression of FlucDM inclusion formation. Conversely, deletion of the C-terminal TTK-LKS region in DNAJB8, a region not required to suppress polyQ aggregation, abolished its ability to inhibit inclusion formation by FlucDM. Thus, our data suggest that DNAJB6 and DNAJB8 possess two distinct domains involved in the inhibition of protein aggregation, one responsible for binding to β-hairpins that form during amyloid formation and another that mediates the degradation of destabilised client proteins via the proteasome.Summary statement Specialised DNAJB molecular chaperones are potent suppressors of protein aggregation and interact with different types of client proteins via distinct C-terminal regionsCompeting Interest StatementThe authors have declared no competing interest.ALSAmyotrophic lateral sclerosisANOVAAnalysis of varianceEGFPEnhanced green fluorescent proteinFCSFoetal calf serumFloITFlow cytometric analysis of inclusions and traffickingFlucFirefly luciferaseFlucDMFirefly luciferase double mutantFlucWTFirefly luciferase wild-typeHspHeat shock proteinHspmRFPMonomeric red fluorescent proteinHspPBSPhosphate buffered salineHspPolyQPolyglutamineHspPQCProtein quality controlHspProteostasisProtein homeostasisHspSOD1Superoxide dismutase 1HspTDP-43TAR DNA-binding protein 43