Differential phosphorylation of the docking protein Gab1 by c-Src and the hepatocyte growth factor receptor regulates different aspects of cell functions

Abstract

The docking protein Grb2-associated binder1 (Gab1) has a central role in the integration of the growth-factor signaling. In this study, we aimed to examine the significance of Src-mediated Gab1 phosphorylation in the hepatocyte growth factor (HGF) signaling. Using both mutagenesis and mass spectrometry approaches, Y242, Y259, Y317, Y373 and Y627 of Gab1 were identified to be phosphorylated by c-Src. It is interesting to note that the binding of the tyrosine phosphatase SHP2 to the Y627 antagonized the effect of c-Src on the phosphorylation of the other four tyrosine residues. Moreover, the tyrosine residues predominantly phosphorylated by c-Src were different from those predominantly phosphorylated by the HGF receptor. Gab1 overexpression potentiated both mitogenic and motogenic activities of HGF. However, a Gab1 mutant with substitutions of the Src phosphorylation sites (Y242, Y259, Y317 and Y373) failed to promote HGF-induced DNA synthesis, but retained its ability to facilitate HGF-induced chemotaxis. Taken together, our results not only suggest that the phosphorylation of Gab1 by c-Src is important for HGF-induced DNA synthesis, but also provide an example to illustrate how a docking protein (for example, Gab1) is differentially phosphorylated by c-Src and a receptor tyrosine kinase to emanate full spectrum of signals to the downstream.

PECAM1 regulates flow-mediated Gab1 tyrosine phosphorylation and signaling

“…In particular, we have previously shown that flow activates the PI3K/Akt/eNOS pathway via Src kinase-dependent transactivation of VEGFR2 [6]. It has also been demonstrated that Gab1 Y627 is phosphorylated by Src in vitro [30]. Hereby, we investigated the role of Src kinase in flow- and HGF-induced Gab1 tyrosine phosphorylation.…”

“…It has been reported that Src kinase is involved in flow [6, 19, 29] and HGF [18, 30, 31] signaling in ECs. In particular, we have previously shown that flow activates the PI3K/Akt/eNOS pathway via Src kinase-dependent transactivation of VEGFR2 [6].…”

Deep Coverage of Global Protein Expression and Phosphorylation in Breast Tumor Cell Lines Using TMT 10-plex Isobaric Labeling

“…The phosphorylation of Tyr-187 on MARK1 (downstream of EGFR/Her2 signaling pathway) is required for its activation 34 . The phosphorylation of Tyr-627 of GAB1 confers binding and activation of the tyrosine phosphatase SHP2 35 . Tyr-453 in GAREM is critical for binding of SHP2 to GAREM in MARK1 activation upon EGF stimulation 36 .…”

Docking proteins

“…Gab proteins are tyrosine phosphorylated following activation of diverse receptor types, including specific RTKs, B‐ and T‐cell antigen receptors and β1‐integrin, and depending on the cellular context, this may be mediated by the RTK itself, and/or kinases of the Src, Syk/ZAP‐70 or JAK families [7]. Interestingly, a recent study reported that c‐Src and c‐Met exhibit contrasting selectivity towards particular Gab1 phosphorylation sites, and that phosphorylation of four tyrosine residues by c‐Src contributes to hepatocyte growth factor‐induced DNA synthesis [12]. Gab/DOS tyrosine phosphorylation leads to binding of specific SH2 domain‐containing effectors, the best‐characterized of which is the SH2 domain‐containing protein tyrosine phosphatase Shp2.…”