Basolateral EGF receptor sorting regulated by functionally distinct mechanisms in renal epithelial cells

Area of Science:

• Cell Biology
• Molecular Biology
• Renal Physiology

Background:

• Epithelial tissue proliferation is regulated by polarized signaling receptors like the epidermal growth factor receptor (EGFR).
• In the kidney, EGFRs are targeted to basolateral membranes, separating them from apical ligands.
• The epithelial-specific clathrin adaptor AP1B mediates basolateral EGFR sorting in established epithelia.

Purpose of the Study:

• To investigate the role of protein kinase C (PKC)-dependent phosphorylation of Thr654 in regulating EGFR polarity during epithelial cell junction formation.
• To determine how AP1B and PKC-dependent pathways interact to control EGFR basolateral sorting in polarizing cells.
• To elucidate the distinct cellular functions of EGFR based on its basolateral sorting route.

Main Methods:

• Utilized protein kinase C (PKC)-dependent phosphorylation of Thr654 and AP1B adaptor protein in EGFR polarity studies.
• Employed a PKC-resistant T654A mutation to dissect EGFR sorting pathways.
• Investigated EGFR sorting mechanisms in three-dimensional organotypic cultures to observe distinct cellular phenotypes.

Main Results:

• PKC-dependent phosphorylation of Thr654 regulates EGFR polarity during the formation of new cell-cell junctions.
• The AP1B-dependent pathway does not override a PKC-resistant T654A mutation, indicating pathway specificity.
• EGFR mutations affecting these sorting pathways lead to distinct phenotypes in organotypic cultures, suggesting differential EGFR functions.

Conclusions:

• EGFR executes different functions depending on its specific basolateral sorting route.
• EGFR integrates polarity by switching between distinct basolateral sorting programs in developing epithelial cells.
• Understanding EGFR sorting mechanisms offers insights into renal disorder pathogenesis and potential drug discovery for polycystic kidney disease.