MPDZ promotes DLL4-induced Notch signaling during angiogenesis

Area of Science:

• Molecular Biology
• Developmental Biology
• Cancer Research

Background:

• Angiogenesis, the formation of new blood vessels, is tightly regulated by signaling pathways, including VEGF and Notch.
• Notch signaling, crucial for vascular development, involves interactions between Notch receptors and ligands like DLL4, which are localized at adherens junctions.
• The precise mechanisms controlling Notch ligand localization and subsequent signaling activity remain incompletely understood.

Purpose of the Study:

• To investigate the role of the multiple PDZ domain protein (MPDZ) in modulating Notch signaling.
• To determine how MPDZ influences the cellular localization of Notch ligands (DLL1 and DLL4).
• To assess the impact of MPDZ on angiogenesis in both developmental and tumor contexts.

Main Methods:

• Investigated the physical interaction between MPDZ and Notch ligands (DLL1/DLL4) and adherens junction protein Nectin-2.
• Utilized gene inactivation of MPDZ in cellular models and embryonic mouse hindbrain.
• Examined endothelial-specific MPDZ inactivation in a tumor angiogenesis model.

Main Results:

• MPDZ physically interacts with DLL1 and DLL4, facilitating their recruitment to Nectin-2 at adherens junctions, thereby enhancing Notch signaling.
• MPDZ inactivation resulted in impaired Notch signaling, increased blood vessel sprouting in vitro and in vivo.
• Endothelial-specific MPDZ inactivation promoted enhanced tumor angiogenesis, leading to excessively branched, poorly functional vessels and tumor hypoxia.

Conclusions:

• MPDZ is identified as a novel regulator of Notch signaling by controlling the localization of Notch ligands.
• MPDZ plays a critical role in maintaining proper vascular development and inhibiting aberrant angiogenesis.
• Targeting MPDZ could offer a therapeutic strategy for controlling pathological angiogenesis, such as in tumors.