(A) Overexpression of BiP increased Aβ42 levels in fly brains. Heads of flies expressing Aβ42 alone or co-expressing Aβ42 and BiP were analyzed by western blotting with anti-Aβ antibody. Mean ± SEM, n = 4, *p < 0.05 by Student's t-test. (B) Overexpression of BiP in neurons worsened behavioral deficits in Aβ42 flies. Mean ± SD, n = 5, *p < 0.05 by Mann–Whitney U test. n.s.: not significant. (C) Overexpression of dHRD1 did not reduce Aβ42 levels in fly brains. Mean ± SEM, n = 4, n.s.: not significant (Student's t-test). (D) Overexpression of dHRD1 (dHRD1C9 and dHRD1E20) in neurons worsened behavioral deficits in Aβ42 flies. Mean ± SD, n = 5, *p < 0.05 by Mann–Whitney U test. n.s.: not significant. (E) Overexpression of Rpn11 did not reduce Aβ42 levels in fly brains. Mean ± SEM, n = 4, n.s.: not significant (Student's t-test). (F) Overexpression of Rpn11 in neurons worsened behavioral deficits in Aβ42 flies. Mean ± SD, n = 5, *p < 0.05 by Mann–Whitney U test. n.s.: not significant. See also Figure S5 and Table S5.