Figure 6.

Proteotoxic stress caused by amyloidogenic aggregates is associated with proteasome impairment. (A,B) Chymotrypsin-like proteasome activity of control, nAβ_1–42 and mAβ_3–42 day 4 animals. Depicted are relative activities (B). Error bars represent the standard deviation of three independent experiments. (C,D) 20S α-subunit levels of control, nAβ_1–42 and mAβ_3–42 day 4 animals. Depicted are relative 20S levels (D). Error bars represent the SD of three independent experiments. (E) Representative scheme of the UbG76V::Dendra2 and Aβ_3–42 crossed animals. Degradation of UbG76V::Dendra2 in the muscle cells was determined in the presence of Aβ aggregates in muscle and neurons (left) and the degradation rates of UbG76V::Dendra2 in the neuronal cells were measured in the presence of Aβ aggregates in muscle and neurons (right). Aggregates are indicated as red stared shapes. (F,G) UbG76V::Dendra2 degradation rates in the indicated disease models. Converted UbG76V::Dendra2 protein was imaged immediately and 3 (G) or 24 (F) h later as in Figures 3B,C. Error bars represent the SD of a minimum of 11 animals. (H,I) Chymotrypsin-like proteasome activity of control and mQ₄₀::YFP day 4 animals. Depicted are normalized activities (I). Error bars represent the SD of three independent experiments. (J,K) 20S α-subunit levels of control and mQ₄₀::YFP day 4 animals. Depicted are normalized 20S levels (K). Error bars represent the SD of three independent experiments. (L,M) Model: depletion of HSP70/110/J disaggregating chaperones leads to an increase of misfolded proteins, which is associated with an induction of autophagy and an impairment of proteasome function in young animals and HEK293 cells (L). With the progression of aging in C. elegans, autophagy is not activated and UPS activity is no longer reduced in response to chaperone loss. Autophagy and proteasome pathways are perturbed in the presence of amyloid-like protein aggregates in the muscle and neurons of C. elegans (M).