Vascular endothelial cadherin controls VEGFR-2 internalization and signaling from intracellular compartments

Area of Science:

• Cell Biology
• Molecular Biology
• Signaling Pathways

Background:

• Receptor endocytosis regulates cell signaling duration and magnitude.
• Confluent endothelial cells exhibit contact inhibition and low responsiveness to vascular endothelial growth factor (VEGF).
• Vascular endothelial cadherin (VEC) associates with VEGF receptor-2 (VEGFR-2) and contributes to density-dependent growth inhibition.

Purpose of the Study:

• To elucidate the mechanism by which VEC attenuates VEGFR-2 signaling.
• To investigate the role of VEC in regulating VEGFR-2 internalization and downstream signaling pathways.

Main Methods:

• Investigated VEGF-induced clathrin-dependent internalization of VEGFR-2.
• Assessed VEGFR-2 internalization rates in the presence and absence of VEC.
• Analyzed VEGFR-2 signaling, including phospholipase C-gamma activation and p44/42 mitogen-activated protein kinase phosphorylation.
• Utilized RNA interference to silence junction-associated density-enhanced phosphatase-1/CD148.

Main Results:

• VEGF induces clathrin-dependent internalization of VEGFR-2.
• Absence or disengagement of VEC accelerates VEGFR-2 internalization and prolongs its presence in endosomal compartments.
• Internalized VEGFR-2 remains active, leading to phospholipase C-gamma activation and p44/42 MAPK phosphorylation, promoting cell proliferation.
• Inhibiting VEGFR-2 internalization restored contact inhibition.
• Silencing CD148 phosphatase reactivated VEGFR-2 internalization and signaling.

Conclusions:

• VEC limits endothelial cell proliferation by retaining VEGFR-2 at the plasma membrane.
• VEC prevents VEGFR-2 internalization into signaling endosomes, thereby controlling VEGF-driven cell growth.
• This mechanism highlights VEC's crucial role in maintaining contact inhibition in endothelial cells.