Journal: bioRxiv

Article Title: β-Amyloid impairs Proteasome structure and function. Proteasome activation mitigates amyloid induced toxicity and cognitive deficits

doi: 10.1101/2024.10.23.619877

Figure Lengend Snippet: The impairment can be mitigated by proteasome activators. (A) 20S Proteasome chymotrypsin-like peptidase activity is inhibited by oligomeric Aβ42, but not by Aβ42 monomers or fibrils. N = 4. Asterisks denote statistically significant differences (p<0.05). Right: atomic force microscopy (AFM) images of Aβ particles (tapping mode in air). The occasional larger particles in the “monomer” preparation are likely spontaneously forming oligomers. ( B ) Morphometric analysis of the 20S proteasome particles imaged by AFM (tapping mode in liquid) reveals shifts in the particles’ dimensions upon incubation with oligomeric Aβ42. 827 control 20S particles (incubated with a vehicle) and 1181 particles incubated with 2 µM oligomeric Aβ42 were analysed. Solid lines are fittings for the frequencies of control (black) and oligo-treated (red) particles. Since almost all particles are in to-view position, the “length” parameter generated during the particle analysis corresponds to the diameter of the 20S α face. The diameters are raw numbers without correction for tip broadening. When the correction of 2 pixels for SNL probe is applied, the diameter for peak 1 (raw: 14 - 15 nm) falls into 10 – 11 nm range, in excellent agreement with the crystal structure of the human 20S proteasome . See Results for putative assignment of proteasome forms to the numbered peaks. (C) Incubation with oligomeric Aβ42 shifts the conformational equilibrium of 20S core particles imaged by AFM (tapping mode in liquid) toward less open-gate and closed-gate forms, but more intermediate forms. (D) Oligomeric Aβ42 does not significantly affect degradation of oxidized hemoglobin. Degradation of hemoglobin is enhanced by a range of oligomeric Aβ42 concentrations. N=4 samples. ( E, F ) Treatment of the 20S proteasome with activators TAT1-DEN or TAT1-TOD partially protects from inhibition inflicted by the oligomeric Aβ42. ( G ) Incubation with the proteasome activator TAT1-DEN induces a dramatic shift toward open-gate forms, even in the presence of 2 µM of oligomeric Aβ42. The numbers in columns indicate percent of conformers. The number of particles analyzed: 733 (vehicle control), 843 (with oligo Aβ42), 270 (with 1 µM TAT1-DEN) and 171 (with oligo Aβ42and TAT1-DEN). Average ± SD, n= 5 to 9 fields.

Article Snippet: Purified 20S Proteasome (R&D Systems, Cat# E-360), purified 26S Proteasome (R&D Systems, Cat# E-365).

Techniques: Activity Assay, Microscopy, Incubation, Control, Generated, Particle Size Analysis, Inhibition

Journal: bioRxiv

Article Title: β-Amyloid impairs Proteasome structure and function. Proteasome activation mitigates amyloid induced toxicity and cognitive deficits

doi: 10.1101/2024.10.23.619877

Figure Lengend Snippet: (A) Native page immunoblot depicting purified 20S and 26S proteasome under incubation with oligomeric Aβ42. Immunoblot performed against proteasome β5 subunit and accompanying total protein silver stain. Arrows depict 26S and 20S proteasome assemblages. (B) Native page immunoblot depicting purified 26S proteasome under incubation with varying concentrations of oligomeric Aβ42. Top image shows a representative set, histogram represents N=3 per condition. (C) Model for impact of Aβ on proteasome processes. *p < 0 . 05, Student’s t test was used unless otherwise stated. N represents the number of animals or samples per group .

Article Snippet: Purified 20S Proteasome (R&D Systems, Cat# E-360), purified 26S Proteasome (R&D Systems, Cat# E-365).

Techniques: Clear Native PAGE, Western Blot, Purification, Incubation, Silver Staining