DNAJB6, a Key Factor in Neuronal Sensitivity to Amyloidogenesis

CAG-repeat expansions in at least eight different genes cause neurodegeneration. The length of the extended polyglutamine stretches in the corresponding proteins is proportionally related to their aggregation propensity. Although these proteins are ubiquitously expressed, they predominantly cause toxicity to neurons. To understand this neuronal hypersensitivity, we generated induced pluripotent stem cell (iPSC) lines of spinocerebellar ataxia type 3 and Huntington’s disease patients. iPSC generation and neuronal differentiation are unaffected by polyglutamine proteins and show no spontaneous aggregate formation. However, upon glutamate treatment, aggregates form in neurons but not in patient-derived neural progenitors. During differentiation, the chaperone network is drastically rewired, including loss of expression of the anti-amyloidogenic chaperone DNAJB6. Upregulation of DNAJB6 in neurons antagonizes glutamate-induced aggregation, while knockdown of DNAJB6 in progenitors results in spontaneous polyglutamine aggregation. Loss of DNAJB6 expression upon differentiation is confirmed in vivo, explaining why stem cells are intrinsically protected against amyloidogenesis and protein aggregates are dominantly present in neurons. [Display omitted] •The chaperone network rewires during differentiation•Endogenous expanded ataxin-3 aggregates in patient-derived neurons but not progenitors•DNAJB6 is critical for polyglutamine protein aggregation in patient-derived cells Thiruvalluvan et al. show that, upon differentiation, the cellular chaperone network is rewired. This includes a downregulation of the Hsp70 co-chaperone DNAJB6. High levels of DNAJB6 keep patient-derived neuronal progenitors resistant to the formation of amyloids. The sole knockdown of DNAJB6 in progenitors induces spontaneous aggregation of endogenously expressed polyglutamine proteins. Inversely, low levels of DNAJB6 in neurons render them hypersensitive to amyloid formation, which can be restored by re-elevating DNAJB6 expression levels.