The β-site amyloid precursor protein (APP)-cleaving enzyme 1 (β-secretase BACE1) initiates
The β-site amyloid precursor protein (APP)-cleaving enzyme 1 (β-secretase BACE1) initiates amyloidogenic processing of APP to generate amyloid β (Aβ) which is a hallmark of Alzheimer disease (AD) pathology. whereas the RNAi knockdown of endogenous Rheb promotes BACE1 accumulation and this effect by Rheb is independent of its mTOR signaling. Moreover GTP-bound Rheb interacts with BACE1 and degrades it through proteasomal and lysosomal pathways. Finally we demonstrate that Rheb levels are down-regulated in the AD brain which is consistent with an increased BACE1 expression. Altogether our study defines Rheb as a novel physiological regulator of BACE1 levels and Aβ generation and the Rheb-BACE1 circuitry may have a role in brain biology and disease. binding experiments were carried out essentially as described previously (31 32 34 Briefly at the indicated time points after transfection CAY10505 cells were pelleted and lysed in IP buffer (50 mm Tris pH 7.6 150 mm NaCl 1 Nonidet P-40 and 10% glycerol with protease and phosphatase inhibitor). Protein concentration was measured with a BCA protein assay reagent (Pierce) or the cells were directly lysed in 2× SDS loading buffer (NuPAGE LDS loading buffer). Equal amounts of protein or CAY10505 equal volume of cell lysates were loaded and separated by 4-12% Bis-Tris gel (Invitrogen). The blots were probed for β-actin to estimate the total protein loaded. All the primary antibodies were used in the range of 1 1:3000 dilutions whereas the secondary antibodies were used at 1:10 0 GST-tagged Rheb was drawn down with glutathione beads as referred to before (31 32 as well as the binding of endogenous BACE1 was recognized by Traditional western blotting. BACE1 was immunoprecipitated after a preclearance stage from P25 mouse mind homogenate utilizing a BACE1 antibody accompanied by Proteins G Plus/Proteins A-Agarose beads (Calbiochem) cleaned 3 x with IP buffer and incubated with 1 μg of recombinant Rheb (～250 nm) in 200 μl of IP buffer for 4 h. The beads had been cleaned in IP buffer as well as the destined Rheb was recognized using Traditional western blotting. Major antibodies had been diluted in 2% seafood gelatin in TBS-T (Sigma-G7765). We discovered that seafood gelatin which can be less costly than BSA functions as efficiently as CAY10505 BSA for major antibody dilutions. Dimension of APP Control by BACE1 Major cortical neurons were infected with Ad-Rheb and Ad-control. The moderate was collected and centrifuged and the cell pellet was resuspended in lysis buffer and loaded onto the gel to measure APP-FL and APP-C-terminal fragment (CTF). The sAPPβ levels in the medium were decided using an antibody against sAPPβ and were quantified after normalizing to APP-FL. Similarly Aβ (x-40 and x-42) levels in the medium were estimated using a commercially available ELISA kit (Wako) according to the manufacturer’s protocol. Immunostaining Staining for Rheb and BACE1 was performed essentially as described CAY10505 before (31). Briefly ～75 0 HEK293 cells were seeded on 35-mm glass-bottom dishes. After 24 h the cells were transfected with the indicated vectors. After 48 h the cells were fixed with 4% paraformaldehyde (20 min) and membrane-permeabilized with 0.2% Triton X-100 (5 CAY10505 min). For Rheb/BACE1 co-staining the transfected HA-Rheb and Myc-BACE1 were stained with antibodies against HA (1:200 rabbit polyclonal) and Myc (1:150 mouse monoclonal) and each was incubated for 12 h at 4 °C. Appropriate secondary antibodies conjugated to Alexa Fluor 488 and 568 (Molecular Probes) were incubated together with the nuclear DAPI stain for 1 h at room temperature. Glass dishes were covered with antifade Fluoromount G (Southern Biotech). The images were obtained by a Leica TCS SP8 confocal microscope. RT-PCR for Rabbit polyclonal to CapG. BACE1 mRNA The RNA transcripts for BACE1 mRNA were estimated using the forward primer GCCTTCCCAGTTGGAGCCGTTGAT and the reverse primer CGCAGCGGCCTGGGGGGCGCCCC and the RNA transcripts for GAPDH mRNA as internal control were estimated using the forward primer GAGTCAACGGATTTGGTCGT and the reverse primer TTGATTTTGGAGGGATCTCG as indicated previously (35 36 Rheb Knockdown Experiments Cultured cortical neurons on days 14 were infected with lentiviral particle produced using Addgene protocol expressing control shRNA (scrambled) or Rheb shRNA1 specific to human and mouse (TRCN0000010424 Sigma) at multiplicity of contamination 1-3. After.