Protein samples were immunoprecipitated using anti-HA beads. Eluates were separated by SDS-PAGE and Coomassie-stained, and target bands were excised for in-gel tryptic digestion after destaining, reduction, and alkylation. The resulting peptides were lyophilized and analyzed by LC-MS/MS on a Q Exactive mass spectrometer (ThermoFisher) coupled to an Easy nLC 1200 system. Peptides were separated on a C18 column using a 120-minute gradient. MS data were acquired in data-dependent acquisition mode with two replicates per condition.