DNAJB6 is a peptide-binding chaperone which can suppress amyloid fibrillation of polyglutamine peptides at substoichiometric molar ratios

Abstract

Expanded polyglutamine (polyQ) stretches lead to protein aggregation and severe neurodegenerative diseases. A highly efficient suppressor of polyQ aggregation was identified, the DNAJB6, when molecular chaperones from the HSPH, HSPA, and DNAJ families were screened for huntingtin exon 1 aggregation in cells (Hageman et al. in Mol Cell 37(3):355–369, 2010). Furthermore, also aggregation of polyQ peptides expressed in cells was recently found to be efficiently suppressed by co-expression of DNAJB6 (Gillis et al. in J Biol Chem 288:17225–17237, 2013). These suppression effects can be due to an indirect effect of DNAJB6 on other cellular components or to a direct interaction between DNAJB6 and polyQ peptides that may depend on other cellular components. Here, we have purified the DNAJB6 protein to investigate the suppression mechanism. The purified DNAJB6 protein formed large heterogeneous oligomers, in contrast to the more canonical family member DNAJB1 which is dimeric. Purified DNAJB6 protein, at substoichiometric molar ratios, efficiently suppressed fibrillation of polyQ peptides with 45°Q in a thioflavin T fibrillation. No suppression was obtained with DNAJB1, but with the closest homologue to DNAJB6, DNAJB8. The suppression effect was independent of HSPA1 and ATP. These data, based on purified proteins and controlled fibrillation in vitro, strongly suggest that the fibrillation suppression is due to a direct protein–protein interaction between the polyQ peptides and DNAJB6 and that the DNAJB6 has unique fibrillation suppression properties lacking in DNAJB1. Together, the data obtained in cells and in vitro support the view that DNAJB6 is a peptide-binding chaperone that can interact with polyQ peptides that are incompletely degraded by and released from the proteasome.Electronic supplementary materialThe online version of this article (doi:10.1007/s12192-013-0448-5) contains supplementary material, which is available to authorized users.

Pseudocatalytic Antiaggregation Activity of Antibodies: Immunoglobulins can Influence α-Synuclein Aggregation at Substoichiometric Concentrations

“…Similar results have been previously shown for chaperones [34][35][36], some non-chaperone proteins such as pyruvate kinase and seeds. Particles with all dimensions smaller than 30 nm were defined as oligomers while particles with any dimension over 30 nm were defined as fibrils catalase [37] and some small molecules [28].…”

“…Particles with all dimensions smaller than 30 nm were defined as oligomers while particles with any dimension over 30 nm were defined as fibrils catalase [37] and some small molecules [28]. Both chaperone and non-chaperone proteins that inhibited protein aggregation were shown to bind to target proteins [34,35,37,36].…”

Molecular Interaction between the Chaperone Hsc70 and the N-terminal Flank of Huntingtin Exon 1 Modulates Aggregation

“…In this respect, it is noteworthy that Hsc70 binds ␣-synuclein (29) and HttEx1Qn (this work) through the same residues within the substratebinding domain. Other chaperones, such as DNAJB6, directly bind the polyQ tract because this chaperone has been shown to prevent the aggregation of polyQ much more efficiently than HttEx1Qn of the same polyQ length (64).…”

Hsp40 Co-chaperones as Drug Targets: Towards the Development of Specific Inhibitors

“…Both DNAJB6 and DNAJB8 can suppress the intracellular aggregation of polyglutamine-containing proteins. The formation of proteasome-resistant intracellular aggregates is the first stage of numerous neurodegenerative diseases, suggesting that activation of DNAJB8 and DNAJB6 may be one approach to prevention or treatment of these types of disorders [12]. DNAJB6 was also able to suppress the aggregation of amyloid in vitro, a protein involved in Alzheimer's disease, in a mechanism that was independent of Hsp70 and could not be recapitulated by expression of another type II Hsp40, DNAJB1, demonstrating that this activity is not a general feature of all Hsp40s, but rather was specific to DNAJB6 [57].…”