Mig6 is a sensor of EGF receptor inactivation that directly activates c-Abl to induce apoptosis during epithelial...

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Epithelial homeostasis relies on growth factors for cell survival, but the mechanisms are not fully understood.
• Receptor tyrosine kinase (RTK) signaling is crucial for cell fate decisions.
• The role of Mig6 in regulating RTK signaling and apoptosis requires further elucidation.

Purpose of the Study:

• To investigate the role of Mig6 in mediating apoptosis upon growth factor withdrawal.
• To elucidate the signaling pathway linking ErbB receptor inactivation to programmed cell death.
• To challenge the conventional understanding of growth factor deprivation-induced apoptosis.

Main Methods:

• Utilized mammary epithelial cell models.
• Investigated protein-protein interactions between Mig6, ErbB receptors, and c-Abl.
• Employed gene deletion (Errfi1 knockout), kinase inhibition, and RNA interference (RNAi) for c-Abl.
• Analyzed apoptosis induction and mammary duct morphology.

Main Results:

• Ligand deprivation causes Mig6 to dissociate from ErbB receptors and activate c-Abl tyrosine kinase.
• Activated c-Abl triggers p73-dependent apoptosis in mammary epithelial cells.
• Loss or inhibition of Mig6 or c-Abl impairs apoptosis, leading to mammary duct filling.
• Src family kinase-mediated phosphorylation of c-Abl at Tyr488 by EGF prevents Mig6 binding and activation.

Conclusions:

• Mig6 acts as a sensor for epidermal growth factor (EGF) deprivation, directly activating proapoptotic c-Abl.
• This study reveals an 'inverse' RTK signaling mode where receptor inactivation actively induces apoptosis.
• The findings challenge the passive model of growth factor deprivation-induced apoptosis, highlighting an active signaling switch.