Acute ligand-independent Src activation mimics low EGF-induced EGFR surface signalling and redistribution into...

Area of Science:

• Cellular signaling and receptor trafficking

Background:

• Src tyrosine kinase and epidermal growth factor receptor (EGFR) are frequently over-expressed and activated in human breast cancer.
• Mechanisms of Src and EGFR interaction and their impact on EGFR signaling and trafficking are not fully understood.

Purpose of the Study:

• To investigate the effects of acute Src activation on the signaling and trafficking of non-liganded EGFR in MDCK cells.
• To elucidate the role of Src in EGFR phosphorylation, endocytosis, and intracellular localization.

Main Methods:

• Utilized temperature-sensitive v-Src (ts/v-Src) for thermo-activation in MDCK cell monolayers.
• Assessed Src recruitment to the plasma membrane, association with EGFR, and EGFR phosphorylation.
• Quantified EGF surface binding, EGFR endocytosis via clathrin-coated vesicles, and intracellular EGFR distribution.

Main Results:

• Thermo-activated Src rapidly recruited to the plasma membrane and associated with EGFR, leading to EGFR phosphorylation at Y845 and Y1173.
• Activated Src decreased EGF surface binding and triggered EGFR endocytosis, mimicking effects of low EGF concentrations.
• EGFR was sequestered in perinuclear/recycling endosomes, avoiding lysosomal degradation, with synergistic phosphorylation observed upon combined Src activation and EGF stimulation.

Conclusions:

• Acute Src activation in MDCK cells mimics low EGF effects on EGFR activation and redistribution.
• Src-EGFR interactions are sufficient to trigger EGFR activation and signaling, potentially contributing to local signaling without external stimuli or receptor overexpression.