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Requirement for the adapter protein GRB2 in EGF receptor endocytosis
Abstract:
Activated epidermal growth factor (EGF) receptors induce the formation of various complexes of intracellular signaling proteins that are mediated by SRC homology 2 (SH2) and SH3 domains. The activated receptors are also rapidly internalized into the endocytotic compartment and degraded in lysosomes. EGF stimulation of canine epithelial cells induced a rapid and transient association of the SH3-SH2-SH3 protein GRB2 with dynamin, a guanosine triphosphatase that regulates endocytosis. Disruption of GRB2 interactions by microinjection of a peptide corresponding to the GRB2 SH2 domain or its phosphopeptide ligand blocked EGF receptor endocytosis; other SH2 domains that bind EGF receptors or antibodies that neutralize RAS did not. Both activation and termination of EGF signaling appear to be regulated by the diverse interactions of GRB2.
Insights
GRB2 protein interactions with dynamin regulate epidermal growth factor (EGF) receptor endocytosis. Disrupting these interactions blocks EGF receptor internalization, suggesting GRB2 controls EGF signaling termination.
Area of Science:
- Cell biology
- Molecular signaling
- Endocytosis
Background:
- Epidermal growth factor (EGF) receptors initiate intracellular signaling cascades via SRC homology 2 (SH2) and SH3 domains.
- Activated EGF receptors are internalized and degraded in lysosomes, a process critical for signal termination.
- GRB2 is an adaptor protein containing SH2 and SH3 domains, implicated in various signaling pathways.
Purpose of the Study:
- To investigate the role of GRB2 in EGF receptor endocytosis.
- To identify specific protein interactions regulating EGF receptor internalization.
- To understand how GRB2 mediates the termination of EGF signaling.
Main Methods:
- Stimulation of canine epithelial cells with EGF.
- Co-immunoprecipitation to assess protein complex formation.
- Microinjection of peptides (GRB2 SH2 domain, phosphopeptide ligand) to disrupt protein interactions.
- Assessment of EGF receptor endocytosis.
Main Results:
- EGF stimulation induced a transient association between GRB2 and dynamin, a key regulator of endocytosis.
- Microinjection of a GRB2 SH2 domain peptide or its phosphopeptide ligand inhibited EGF receptor endocytosis.
- Disruption of other SH2 domain interactions or RAS neutralization did not affect EGF receptor endocytosis.
Conclusions:
- GRB2 plays a crucial role in mediating EGF receptor endocytosis.
- The interaction between GRB2 and dynamin is essential for EGF receptor internalization.
- Diverse interactions of GRB2 are critical for both the activation and termination of EGF signaling.