Journal: bioRxiv
Article Title: A non-canonical AKT1-TERT pathway coordinates autophagy and ERphagy
doi: 10.1101/2025.11.24.690135
Figure Lengend Snippet: a) Co-immunoprecipitation (Co-IP) with anti-TERT antibody shows increased interaction between TERT and c-MYC following AKT2 inhibition; no interaction with FOXO3a was detected. A schematic illustrates TERT’s interaction with c-MYC and the lack of interaction with FOXO3a. b) Co-immunoprecipitation with anti-FOXO3A antibody demonstrates an enhanced interaction between FOXO3a and c-MYC after AKT2 inhibition; no interaction between FOXO3a and TERT was observed. A schematic depicts the interaction of FOXO3a with c-MYC, highlighting the absence of interaction with TERT. c) Western blot showing UPR arm of PERK through eIF2α and ATF4 and ER chaperone BiP in the cytoplasmic fraction upon AKT2 inhibition. PERK-eIF2α increases ATF4 expression upon AKT2 inhibition. A total of 25 µg of protein was loaded in each well. Vinculin was utilized as a control for the cytoplasmic fraction, while H3 served as a nuclear loading control. d) Co-IP of TERT showing interaction with ATF4 and not PERK upon AKT2 inhibition. e) Co-IP of FOXO3a showing exclusive interaction with PERK and ATF4 upon AKT2 inhibition. f) Western blot analysis indicates elevated expression at both 6 hours and 24 hours of phospho-AMPKα and AMPK-regulated phospho-ULK1 Ser555 following AKT2 inhibition at both 6 and 24 hours, while mTORC1-regulated phospho-ULK1 Ser757 was reduced at 6 hours. g) Western blot results show increased expression of autophagy induction genes, including ATG3, ATG4B, ATG7, and ATG13, after AKT2 inhibition at both 6 and 24 hours. h) Immunofluorescence analysis using a tandem adenoviral GFP-RFP-LC3 construct demonstrates autophagy flux in hFRPE cells infected with the tandem construct overnight, labeling autophagosomes (yellow) and autolysosomes (red). Post DMSO or AKT2i treatment for 24 hours, a significant increase in red puncta (autolysosomes) was observed in AKT2 inhibition condition compared to DMSO controls, indicating enhanced autophagy flux. This was further amplified upon autophagy blockade with bafilomycin (100nM) for 4 hours. Scale bar = 10 µm i) Quantification of autophagosome (yellow puncta) and autolysosomes (red puncta) in DMSO or AKT2i treatment with or without bafilomycin A (100nM for 4 hours). j) LC3 flux ratio analysis in iPSC RPE CFH Y402H cells treated with DMSO or AKT2i for 24 hours, followed by treatment with or without bafilomycin (100 nM for 4 hours). The ratio of LC3-II to LC3-I illustrates autophagic flux, with AKT2i treatment resulting in a significant increase in the LC3-II/LC3-I ratio, indicating enhanced autophagy. In the presence of bafilomycin, the LC3-II/LC3-I ratio further increases due to the accumulation of LC3-II, while p62 levels also rise, suggesting an inhibition of autophagic degradation and highlighting impaired flux despite increased autophagosome formation. k) Quantification of LC3 flux ratio. l) Quantification of percent accumulation of p62 with bafilomycin A treatment (100nM for 4 hours). Values represent mean ± s.d. (n = 4). Statistical analysis was performed using Student’s t -test or one-way ANOVA followed by Tukey’s post hoc test for multiple comparisons. * P < 0.05, ** P < 0.01, **** P < 0.001.
Article Snippet: The primary antibodies Akt1 (2938S), Akt2 (3063S), mTOR (2983S), RPTOR (2280S), RICTOR (2114S), PERK (5683T), p-PERK (3179S), eIF2α (9722S), p-eIF2α (9721S), ATF4 (11815S), BiP (3177T), CHOP (2895T), FOXO3a (12829S), p-FOXO3a (9464S), β-actin (4970S), Vinculin (13901S) and c-MYC (5605T) were purchased from Cell Signaling Technology, Inc. TERT (NB100-317) was purchased from Novus Biologicals.
Techniques: Immunoprecipitation, Co-Immunoprecipitation Assay, Inhibition, Western Blot, Expressing, Control, Immunofluorescence, Construct, Infection, Labeling, Amplification