Figure 4.

PML Modulates Autophagy through the AMPK/mTOR/Ulk1 Pathway in a Ca²⁺-Dependent Manner

(A) Immunoblot detection of the phosphorylation status of AMPK, ACCα, p70^S6K, mTOR, and Ulk1 in Pml^+/+ and Pml^−/− MEFs.

(B) Detection of autophagy and AMPK-mTOR-Ulk1 phosphorylation levels in the liver and skeletal muscle of Pml^+/+ and Pml^−/− mice.

(C) Representative traces of increased mitochondrial Ca²⁺ levels in Pml^−/− MEFs after MCU overexpression. Pml^−/−: [Ca²⁺]_m peak 33.7 ± 2.55; Pml^−/− + MCU: [Ca²⁺]_m peak 59.2 ± 6.22) SEM. ^∗∗p < 0.01, n = 3.

(D–F) Quantification of autophagy in Pml^−/− MEFs following MCU overexpression via (D and E) analysis of GFP-LC3 puncta or (F) immunoblotting. Representative images are shown. Bars, SEM. ^∗∗p < 0.01, n = 3. Scale bar, 10 μm.

(G) Schematic model of autophagy regulation by PML. In the absence of Pml, the release of Ca²⁺ from the ER into the mitochondria and the production of ATP are reduced. This low-energy status induces AMPK activation, mTOR inhibition, and Ulk1 phosphorylation, leading to increased autophagy.