Figure 4(A) Western Blot analysis of PKA R1α protein levels in NSC34 cells, treated with 250 nM Torin1 or deprived of amino-acids and serum for 16 hours. Lysosomal degradation was blocked in the last 4 hours using 67 nM of Bafilomycin A (BafA). (B) Starvation significantly reduced PKA R1α protein levels in NSC34 cells (vehicle set to 100%, starvation: 31.19± 5.085%, p<0.0001, one-tailed unpaired t-test). n=5. (C) Application of 67 nM BafA for 4 hours before harvesting was sufficient to stabilize the PKA R1α protein levels in starved NSC34 cells (starvation set to 100%, starvation+BafA: 155.5± 13.93%, p=0.002, one-tailed unpaired t-test).16 hours starvation significantly increased intracellular cAMP level measured as mean intensity in MAP2- positive cultured primary neurons (Vehicle: 212.4±5.619, Starvation: 255.1±5.715; p<0.0001, two-tailed paired t-test). nVehicle=314, nStarvation=306 neurons from n=3.16 hours starvation significantly increased intracellular cAMP level measured as mean intensity in MAP2- positive cultured primary neurons (Vehicle: 212.4±5.619, Starvation: 255.1±5.715; p<0.0001, two-tailed paired t-test). nVehicle=314, nStarvation=306 neurons from n=3.(F, G) Phosphorylation state of proteins containing PKA substrate RRXS/T motif was increased upon 16 hours of amino-acid and serum starvation in primary cortico-hippocampal neurons at DIV14 and was suppressed by 1 µM H89 supplementation in the media (Vehicle set to 100%, Starvation: 326.60±94.53%, H89: 214.80±56.87%, p=0.033, one-way ANOVA with Dunn's multiple comparison test). n=4. The pPKA substrate levels were normalized to the total protein amount stained with Ponceau S.Treatment of NSC34 cells with BafA (67nM) for 6 hours significantly increased PKA R1α protein levels compared to the DMSO-treated group set to 100% (BafA: 198.9± 28.44%, p=0.003, one-tailed unpaired t-test).Treatment of NSC34 cells with BafA (67nM) for 6 hours significantly increased PKA R1α protein levels compared to the DMSO-treated group set to 100% (BafA: 198.9± 28.44%, p=0.003, one-tailed unpaired t-test). n=6.(J) Western blot analysis of purified autophagosomes (AVs) (50μg AVs/lane) with and without Proteinase K (PK) treatment. TX-100 (1% final) was used as a positive control for the activity of PK. Synaptosome lysates (Syn, 30μg/lane) were used as a positive control for the signal of antibodies.(M, N) Representative fluorescent images and subsequent analysis of PKA R1- α/p62 colocalization (Pearson's correlation coefficient) in primary cortico-hippocampal neurons, which have undergone 16 hours amino-acids and serum starvation and were additionally treated with BafA (67nM) to visualize the lysosomes (control: 0.68± 0.019, starvation: 0.58± 0.015, starvation+BafA: 0.83± 0.014; pcontrol vs starvation<0.0001, pcontrol vs starvation+BafA<0.0001, pstarvation vs starvation+BafA<0.0001 Ordinary one-way ANOVA with Tukey's multiple comparison test). ncontrol=36, nstarvation=38, nstarvation+BafA=36 neurons from n=3.Co-immunoprecipitation of endogenous PKA R1-β with PKA-Cα from Atg5flox:CamKIIα-Cre WT/KO mouse brain lysates (WT set to 100%, KO: 170.3± 14.88%, p=0.005, one-tailed unpaired t-test, n=3). Input, 1.5% of the total lysate was added to the assay.Co-immunoprecipitation of endogenous PKA R1-β with PKA-Cα from Atg5flox:CamKIIα-Cre WT/KO mouse brain lysates (WT set to 100%, KO: 170.3± 14.88%, p=0.005, one-tailed unpaired t-test, n=3). Input, 1.5% of the total lysate was added to the assay.