This project aims to identify potential E3 ubiquitin ligases regulating MCT1 (monocarboxylate transporter 1) in human cells. We performed immunoprecipitation of MCT1 followed by LC-MS/MS analysis using a Q-Exactive HF X mass spectrometer. Samples included control (con) and MCT1-pulldown (MCT1) groups, each with 7 biological replicates. Proteins were identified via Mascot search against the human SwissProt database (20,324 sequences) with FDR <1% at PSM level. A total of 398–1,201 proteins were identified per sample. The results will be used to screen for candidate E3 ligases interacting with MCT1.