The Gab1 Docking Protein Links the B Cell Antigen Receptor to the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway and to the SHP2 Tyrosine Phosphatase

B cell antigen receptor (BCR) signaling causes tyrosine phosphorylation of the Gab1 docking protein. This allows phosphatidylinositol 3-kinase (PI3K) and the SHP2 tyrosine phosphatase to bind to Gab1. In this report, we tested the hypothesis that Gab1 acts as an amplifier of PI3K- and SHP2-dependent...

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Bibliographic Details
Published in:The Journal of biological chemistry 2001-04, Vol.276 (15), p.12257-12265
Main Authors: Ingham, Robert J., Santos, Lorna, Dang-Lawson, May, Holgado-Madruga, Marina, Dudek, Peter, Maroun, Christiane R., Wong, Albert J., Matsuuchi, Linda, Gold, Michael R.
Format: Article
Language:English
Subjects:
B-Lymphocytes - metabolism
Cell Line
Cell Membrane - metabolism
Gab1 protein
Intracellular Signaling Peptides and Proteins
Phosphatidylinositol 3-Kinases - metabolism
Phosphoproteins - metabolism
Phosphorylation
Protein Binding
Protein Transport
Protein Tyrosine Phosphatase, Non-Receptor Type 6
Protein Tyrosine Phosphatases - metabolism
Protein-Serine-Threonine Kinases
Proto-Oncogene Proteins - metabolism
Proto-Oncogene Proteins c-akt
Receptors, Antigen, B-Cell - metabolism
Signal Transduction
tyrosine
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Summary:B cell antigen receptor (BCR) signaling causes tyrosine phosphorylation of the Gab1 docking protein. This allows phosphatidylinositol 3-kinase (PI3K) and the SHP2 tyrosine phosphatase to bind to Gab1. In this report, we tested the hypothesis that Gab1 acts as an amplifier of PI3K- and SHP2-dependent signaling in B lymphocytes. By overexpressing Gab1 in the WEHI-231 B cell line, we found that Gab1 can potentiate BCR-induced phosphorylation of Akt, a PI3K-dependent response. Gab1 expression also increased BCR-induced tyrosine phosphorylation of SHP2 as well as the binding of Grb2 to SHP2. We show that the pleckstrin homology (PH) domain of Gab1 is required for BCR-induced phosphorylation of Gab1 and for Gab1 participation in BCR signaling. Moreover, using confocal microscopy, we show that BCR ligation can induce the translocation of Gab1 from the cytosol to the plasma membrane and that this requires the Gab1 PH domain as well as PI3K activity. These findings are consistent with a model in which the binding of the Gab1 PH domain to PI3K-derived lipids brings Gab1 to the plasma membrane, where it can be tyrosine-phosphorylated and then act as an amplifier of BCR signaling.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M010590200