Journal: Autophagy
Article Title: A novel MTORC2-AKT-ROS axis triggers mitofission and mitophagy-associated execution of colorectal cancer cells upon drug-induced activation of mutant KRAS
doi: 10.1080/15548627.2024.2307224
Figure Lengend Snippet: MTORC2 mediates phosphorylation of AKT S473 that triggers intracellular ROS. (A) Schematic diagram of the crosstalk between MTORC1, MTORC2 and AKT phosphorylation. Image created with BioRender.com. (B) HCT116 cells were pre-treated for 2 h with rapamycin or torin 1 (both 250 nM) followed by incubation with C1 (50 μg/mL for 3 h and 6 h) and lysates were immunoblotted for AKT p-S473, total AKT, LC3B-II, SQSTM1 and OPA1 (L and S forms). GAPDH was used as the loading control. (C) HCT116 cells were transfected with si RPTOR or si RICTOR or non-targeting si RNA control (10 nM for 48 h) and exposed to 50 μg/mL of C1 for 3 h and 6 h. Lysates were immunoblotted for AKT p-S473, total AKT, LC3B-II, SQSTM1, OPA1 (L and S forms), RPTOR and RICTOR. GAPDH was used as the loading control. (D and E) Immunoblotting analysis of mitochondria and cytosolic fractions from HCT116 cells pre-treated with rapamycin (250 nM) or torin 1 (100 nM) (D) or transfected with si RPTOR , si RICTOR or non-targeting negative si RNA control (50 nM for 48 h) (E) and then treated with C1 (50 μg/mL) for 6 h. GAPDH, HSPA1A and HSP90AA1 were used as loading controls. SOD2 and SOD1 were used as mitochondria and cytosolic specific controls respectively. (F) HCT116 cells were preincubated with torin 1 (100 nM) for 2 h, then pre-stained with 1 µM Mtphagy Dye and treated with C1 (25 and 50 μg/mL) for 18 h. At least 10,000 cells were analyzed by flow cytometry as described in materials and methods. MFI = mean fluorescence intensity. (G) Mtphagy Dye fluorescence changes are plotted by prism graph using MFI of cells upon the indicated treatments compared to untreated cells (ratio). Data are representative of at least 4 independent experiments. Two-way ANOVA was employed for statistical analysis (* = p < 0.05). (H) HCT116 cells were pre-treated for 2 h with torin 1 (100 nM) followed by treatment with 50 μg/mL of C1 for 18 h. Lysates were immunoblotted for SQSTM1 and LC3B-II. GAPDH was used as the loading control. (I) HCT116 cells were transfected with si RICTOR non-targeting si RNA control (50 nM) for 48 h or pre-incubated with torin 1 (100 nM) for 2 h before exposure to 50 μg/mL of C1 for 6 h. Lysates were immunoblotted for DNM1L p-S616, DNM1L p-S637, DNM1L, AKT p-S473, total AKT, and rictor. GAPDH was used as the loading control. (J) Representative images of HCT116 cells transfected with si RICTOR , si AKT1 and si AKT2 or non-targeting si RNA control (50 nM) for 48 h and then treated with C1 (25 μg/mL for 12 h) before staining with MitoTracker™ green FM and viewed via confocal imaging under 100 X magnification. Scale bar: 10 µm. (K-M) for each sample, 20 cell images were analyzed and mitochondrial footprint, mean summed branch lengths and mean network size (branches) were assessed by MiNA, an ImageJ based analysis used for studying morphological changes in mitochondria. Data were plotted on GraphPad prism V 8.0. C1-treated group were compared against control group using paired t-test (** = p < 0.01, *** = p < 0.001 and **** = p < 0.0001).
Article Snippet: Primary Antibodies: LC3B (Cell Signaling Technology, 3868), GAPDH (Cell Signaling Technology, 2118), anti-phospho-AKT (S473; Cell Signaling Technology, 4060), anti-phospho-AKT (T450; Cell Signaling Technology, 9267), AKT (Cell Signaling Technology, 9272), anti-phospho-MAPKAP1/SIN1 (T86; Cell Signaling Technology 14716), MAPKAP1/SIN1 (Cell Signaling Technology 12860), anti-phospho-DNM1L/DRP1 (S616; Cell Signaling Technology, 4494), anti-phospho-DNM1L/DRP1 (S637; Cell Signaling Technology, 6319), DNM1L/DRP1 (Cell Signaling Technology, 5391), anti-phospho-MAPK/ERK (Y202/Y204; Cell Signaling Technology, 9101), MAPK/ERK (Cell Signaling Technology, 9102), SOD1 (Cell Signaling Technology, 2770), VDAC1 (Cell Signaling Technology, 4661), VDAC2 (Cell Signaling Technology, 9412), HSPA1A/HSP70–1 (Cell Signaling Technology, 4872), BAK1 (Cell Signaling Technology, 3814), TOMM20 (Cell Signaling Technology 13929), OMA1 (Cell Signaling Technology 95,473), human IGF1 (Cell Signaling Technology, 8917), TUBA1A/α-tubulin (Cell Signaling Technology, 2125), KRAS (Bio-Rad Laboratories, MCA-3223Z), anti-phospho-AKT (T308; BD Biosciences 558316), SOD2 (BD Biosciences 611580), OPA1 (Thermo Fisher Scientific, MA5–16149), SQSTM1/p62 (Santa Cruz Biotechnology, sc-28359), RICTOR (Santa Cruz Biotechnology, sc-270181), RPTOR/raptor (Santa Cruz Biotechnology, sc-81537), TIMM23 (Santa Cruz Biotechnology, sc-514463), HSP90AA1A/HSP90AA1B (Santa Cruz Biotechnology, sc-13110) and DNM1L/DRP1 (Santa Cruz Biotechnology, sc-271583).
Techniques: Phospho-proteomics, Incubation, Control, Transfection, Western Blot, Staining, Flow Cytometry, Fluorescence, Imaging