LYN facilitates CBL-PIK3R1 interaction and increased proliferation of CBL mutant cells. (A) Heatmap depicting relative protein abundance in V5 IP samples analyzed by MS. Top 10 proteins correlated with LYN by nearest-neighbors analysis are shown. Proteins highlighted in green also showed significantly increased tyrosine phosphorylation in 32D cells expressing CBL C384Y compared with CBL WT. (B-C) WB for V5, PIK3R1, and β-actin (ACTB) in anti-V5 IP samples and whole-cell lysates (WCL) from 32D-Cbl^KO cells expressing V5-tagged (B) CBL WT, Y371H, C384Y, and R420Q or (C) CBL WT, C384Y, C384Y/G306E, C384Y/ΔPRR, C384Y/3YF, or C384Y/Y731F. (D) WB for V5, PIK3R1, and VCL in anti-V5 IP samples and WCL from TF1-CBL^KO cells expressing V5-tagged CBL WT, C384Y, C384Y/3YF, or C384Y/Y731F. (E) WB for V5, PIK3R1, and β-actin in anti-V5 IP samples and WCL from 32D-Lyn^KO cells expressing V5-tagged CBL WT or C384Y. (F) Competition between CBL WT (dTomato) and C384Y (GFP)-expressing 32D cells on Lyn^WT and Lyn^KO genetic backgrounds. Mean and SD of triplicate values are depicted. Statistical significance for competitive proliferation assays was determined by 2-tailed Student t test comparing Lyn WT to each Lyn KO (*P < .05; ***P < .0001).