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Controlling epidermal growth factor (EGF)-stimulated Ras activation in intact cells by a cell-permeable peptide
1Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2363, USA. Liny@ctrvax.vanderbilt.edu
Abstract:
Epidermal growth factor (EGF)-stimulated Ras activation involves specific interactions between the EGF receptor (EGFR), the adaptor proteins Grb2 and Shc, and the nucleotide exchange factor Sos-1. Study and control of these protein-protein interactions in vivo can be greatly promoted by introducing intracellular reagents that mimic EGFR functions. Here, we showed that a synthetic phosphopeptide encompassing the autophosphorylation site 1068 of EGFR formed a complex with endogenous Grb2 after this peptide was delivered into intact cells by a cell-permeable peptide import technique. Consequently, this intracellular peptide inhibited EGF-induced EGFR/Grb2 associations but not EGFR/Shc or Shc/Grb2 associations. Peptide-mediated disruption of the EGF/Grb2/Sos-1 cascade led to reduced Ras activation and mitogen-activated protein kinase activation. These results indicate that the binding of Grb2 to the phosphorylated Tyr-1068 of EGFR is crucial to the EGF-induced Ras/mitogen-activated protein kinase signaling pathway. The application of cell-permeable peptides to this study demonstrates a useful biochemical tool to probe and control various intracellular processes involved in signal transduction and gene transcription.
Insights
A synthetic peptide targeting epidermal growth factor receptor (EGFR) binding to Grb2 protein disrupted signaling. This disruption reduced Ras and mitogen-activated protein kinase activation, highlighting a key step in cell growth pathways.
Area of Science:
- Cellular signaling
- Molecular biology
- Biochemistry
Background:
- Epidermal growth factor (EGF) signaling is critical for cell growth and involves interactions between EGF receptor (EGFR), Grb2, Shc, and Sos-1.
- Understanding these protein-protein interactions in vivo is essential for studying signal transduction pathways.
Purpose of the Study:
- To investigate the role of EGFR autophosphorylation site 1068 in Grb2 binding.
- To develop and utilize intracellular reagents to probe and control EGFR-mediated signaling.
- To assess the impact of disrupting specific EGFR-Grb2 interactions on downstream signaling pathways.
Main Methods:
- A synthetic phosphopeptide mimicking EGFR autophosphorylation site 1068 was designed.
- Cell-permeable peptide import technique was used to deliver the peptide into intact cells.
- Protein-protein interactions (EGFR/Grb2, EGFR/Shc, Shc/Grb2) were analyzed.
- Ras and mitogen-activated protein kinase (MAPK) activation levels were measured.
Main Results:
- The synthetic phosphopeptide successfully formed a complex with endogenous Grb2 within cells.
- Intracellular peptide delivery inhibited EGF-induced EGFR/Grb2 association but not EGFR/Shc or Shc/Grb2 associations.
- Disruption of the EGFR/Grb2 interaction led to reduced Ras and MAPK activation.
Conclusions:
- Binding of Grb2 to phosphorylated Tyr-1068 of EGFR is crucial for EGF-induced Ras/MAPK signaling.
- Cell-permeable peptides serve as effective biochemical tools for studying and manipulating intracellular signaling pathways.
- This approach offers a method to probe and control signal transduction and gene transcription processes.