Assays

Cells were incubated with 500 µM Biotin-Phenol during the last 30 min of LLOMe or GPN treatment and subsequently pulsed by addition of H2O2 for 1 min at room temperature. To stop the biotinylation reaction, they were washed 3x with quencher solution (10 mM sodium azide, 10 mM sodium ascorbate, 5 mM Trolox in DPBS) and 3x with PBS. All further steps were performed at 4°C unless indicated otherwise. After cell harvest with 0.25% Trypsin/EDTA (ThermoFisher Scientific), cells were counted and heavy- ...

APEX2-mediated biotinylation of cells was carried out as described before (Hung et al., 2016). In brief, cells were supplemented with 500 µM biotin-phenol (IrisBiotech) for 30 min at 37°C before addition of 1 mM H2O2 at room temperature. Cells were then first washed with quencher solution (1 mM sodium azide, 10 mM sodium ascorbate and 5 mM Trolox in DPBS), then with DPBS, scraped and harvested. All steps were carried out at 4°C unless stated otherwise. Cells were washed and suspended in homogenization ...

Samples were essentially prepared as described in Zellner et al. Mol Cell 2021 (DOI: 10.1016/j.molcel.2021.01.009)

Sample preparation for LC-MS/MS Eight million of Cy3/5-positive autophagosomes (roughly 10ug of proteins) were denatured with 2% sodium deoxycholate, 50 mM Tris-HCl pH 8.5, 2.5 mM TCEP, 10 mM chloroacetamide at 95°C for 10 min. Lysates were prepared with in-StageTip (iST) processing method for LC-MS/MS as previously described by Kulak et al. 2014. Briefly, Proteins were digested overnight at 37°C with 1 volume of 50mM Tris-HCl pH 8.5 containing LysC (Wako Chemicals) at 1:100 (w/w) ratio and Trypsin ...

For diGly proteomics: HeLa cells were cultured in lysine- and arginine-free DMEM supplemented with dialyzed FBS, 2 mM L-glutamine, 1 mM sodium pyruvate, penicillin/streptomycin and light (K0) lysine (38 μg/mL) and arginine (66 μg/ml). Medium and heavy media were the same except the light lysine was replaced with K4 and K8-lysine, respectively. Medium and heavy labeled cells were treated for 1 h with 250 µM LLOMe while light labeled were treated for 1 h with vehicle alone (EtOH). Light and heavy ...

HeLa cells stably expressing CNN2-APEX2 were grown at 37°C in DMEM supplemented with FBS, L-Glutamine, Sodium pyruvate. Cells were differentially treated with 5 µM NMS-873 for 15 min followed by 1 h 1 mM LLOMe (Sigma) and 2 h washout wihout any drugs. Proximity labeling was performed essentially as described before (Korver et al., 2019). Briefly, cells were incubated with 500 µM Biotin-Phenol during the last 30 min and subsequently pulsed by addition of H2O2 for 1 min at room temperature. To stop ...

Immunoprecipitation: Cells grown in 2-4x15 cm cell culture plates per sample were harvested by scraping on ice and stored at -80. Lysis was performed for 30 min at 4°C with MCLB buffer (50 mM Tris HCl pH 7.5, 150 mM NaCl, 0.5% NP40, 1x PhosStop,1x protease inhibitor) or Glycerol buffer (20 mM Tris pH 7.5, 150 mM NaCl, 10% glycerol, 5 mM EDTA, 0.5% TritonX, 1x PhosStop, inhibitor, 1x protease inhibitor). Samples were cleared from debris by centrifugation (20.000 g for 10 min at 4°C) and Ultrafree®-CL ...