Abstract
Gab1 is a scaffolding/docking protein that has been suggested to play a role in signal transduction downstream of certain plasma membrane receptors, including platelet-derived growth factor (PDGF) receptors. We found that PDGF induced a rapid Gab1 phosphorylation, which depended on the recruitment of Grb2, indicating that Grb2 acts as a bridge between Gab1 and the PDGF beta-receptor. PDGF also enhanced the binding of Gab1 to the phosphatase SHP-2, but not to p85. To further study the role of Gab1 in PDGF signaling, we transfected porcine aortic endothelial cells with a doxycycline-inducible Gab1 construct. Increased Gab1 expression enhanced the recruitment and activation of SHP-2, as well as the phosphorylation of the mitogen-activated protein kinases Erk and p38 by PDGF. Gab1 expression also enhanced the formation of lamellipodia and cellular protrusions. In Gab1-deficient mouse embryonic fibroblasts, the same phenotype was induced by restoring the expression of wild-type Gab1, but not a mutant Gab1 that was unable to associate with SHP-2. These effects of PDGF on the actin cytoskeleton were not altered by the inhibition of p38 or Erk, but could be blocked by a dominant-negative form of Rac (Asn(17)). Finally, Gab1-deficient fibroblasts showed a decreased chemotactic response toward gradients of PDGF as compared with wild-type cells. In conclusion, Gab1 plays a selective role in the regulation of the mitogen-activated protein kinases Erk and p38 downstream of the PDGF beta-receptor, and contributes to cytoskeletal reorganization and chemotaxis in response to PDGF.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing
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Animals
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Becaplermin
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Blotting, Western
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COS Cells
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Cells, Cultured
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Chemotaxis*
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Cytoskeleton / chemistry*
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Cytoskeleton / metabolism
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DNA-Binding Proteins / metabolism
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Dose-Response Relationship, Drug
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Enzyme Activation
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Fibroblasts / metabolism
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Gene Expression Regulation
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Genes, Dominant
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Glutathione Transferase / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins
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Mice
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Microscopy, Fluorescence
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Nitrophenols / chemistry
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Organophosphorus Compounds / chemistry
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Phosphoproteins / physiology*
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Phosphorylation
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Platelet-Derived Growth Factor / chemistry*
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Platelet-Derived Growth Factor / metabolism
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Precipitin Tests
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Protein Binding
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Protein Tyrosine Phosphatase, Non-Receptor Type 11
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Protein Tyrosine Phosphatases / metabolism
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Proto-Oncogene Proteins c-sis
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Receptor, Platelet-Derived Growth Factor beta / metabolism
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STAT3 Transcription Factor
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Signal Transduction
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Swine
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Time Factors
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Trans-Activators / metabolism
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Transfection
Substances
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Adaptor Proteins, Signal Transducing
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DNA-Binding Proteins
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GAB1 protein, human
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Gab1 protein, mouse
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Intracellular Signaling Peptides and Proteins
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Nitrophenols
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Organophosphorus Compounds
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Phosphoproteins
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Platelet-Derived Growth Factor
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Proto-Oncogene Proteins c-sis
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STAT3 Transcription Factor
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STAT3 protein, human
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Stat3 protein, mouse
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Trans-Activators
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Becaplermin
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nitrophenylphosphate
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Glutathione Transferase
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Receptor, Platelet-Derived Growth Factor beta
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PTPN11 protein, human
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Protein Tyrosine Phosphatase, Non-Receptor Type 11
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Protein Tyrosine Phosphatases
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Ptpn11 protein, mouse