Proteomic analysis of cell surface proteins.

(A) Coomassie brilliant blue (CBB) staining of purified surface proteins separated using SDS-PAGE. (B) Molecular functions of identified cell surface proteins by the Ingenuity Pathway Analysis (IPA) tool. (C) Schematic illustration of mass spectrometric data of 93 membrane proteins whose abundance significantly altered in UBR4-/- MEFs as compared with +/+ MEFs. (D) Immunostaining analyses of VTI1A, SLC7A1 and VAT1 (scale bar = 10 μm). (E) Quantification of D, representing the relative fluorescence intensities for VTI1A, SLC7A1, and VAT1. *p = 0.0325 vs VTI1A of +/+ (n = 13–14 in each group), ***p .0001 vs SLC7A1 of +/+ (n = 13–23 in each group), and **p = 0.0070 vs VAT1 of +/+ (n = 16–22 in each group). Data are presented as mean percentage ± SEM of +/+. Statistical significance was determined using unpaired t-test.