Tyrosine phosphorylation of the scaffold protein IQGAP1 in the MET pathway alters function

• Published in: The Journal of biological chemistry 2020-12, Vol.295 (52), p.18105-18121
• Main Authors: Hedman, Andrew C., McNulty, Dean E., Li, Zhigang, Gorisse, Laëtitia, Annan, Roland S., Sacks, David B.
• Format: Article
• Language: English
• Subjects: Animals; Cell Movement; Cells, Cultured; Fibroblasts - cytology; Fibroblasts - metabolism; Humans; IQGAP1; IQGAP2; mass spectrometry (MS); Mice; phosphorylation; phosphotyrosine; Phosphotyrosine - metabolism; phosphotyrosine signaling; protein phosphorylation; Protein Processing, Post-Translational; Proto-Oncogene Proteins c-met - genetics; Proto-Oncogene Proteins c-met - metabolism; ras GTPase-Activating Proteins - genetics; ras GTPase-Activating Proteins - metabolism; receptor tyrosine kinase; scaffold protein; Signal Transduction
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA120.015891

IQGAP1 is a key scaffold protein that regulates numerous cellular processes and signaling pathways. Analogous to many other cellular proteins, IQGAP1 undergoes post-translational modifications, including phosphorylation. Nevertheless, very little is known about the specific sites of phosphorylation or the effects on IQGAP1 function. Here, using several approaches, including MS, site-directed mutagenesis, siRNA-mediated gene silencing, and chemical inhibitors, we identified the specific tyrosine residues that are phosphorylated on IQGAP1 and evaluated the effect on function. Tyr-172, Tyr-654, Tyr-855, and Tyr-1510 were phosphorylated on IQGAP1 when phosphotyrosine phosphatase activity was inhibited in cells. IQGAP1 was phosphorylated exclusively on Tyr-1510 under conditions with enhanced MET or c-Src signaling, including in human lung cancer cell lines. This phosphorylation was significantly reduced by chemical inhibitors of MET or c-Src or by siRNA-mediated knockdown of MET. To investigate the biological sequelae of phosphorylation, we generated a nonphosphorylatable IQGAP1 construct by replacing Tyr-1510 with alanine. The ability of hepatocyte growth factor, the ligand for MET, to promote AKT activation and cell migration was significantly greater when IQGAP1-null cells were reconstituted with IQGAP1 Y1510A than when cells were reconstituted with WT IQGAP1. Collectively, our data suggest that phosphorylation of Tyr-1510 of IQGAP1 alters cell function. Because increased MET signaling is implicated in the development and progression of several types of carcinoma, IQGAP1 may be a potential therapeutic target in selected malignancies.