p90RSK-MAGI1 Module Controls Endothelial Permeability by Post-translational Modifications of MAGI1 and Hippo Pathway

Area of Science:

• Endothelial cell biology
• Vascular permeability
• Signaling pathways

Background:

• Post-translational modifications (PTMs) of MAGI1, regulated by p90RSK, activate endothelial cells (ECs).
• The role of p90RSK and MAGI1-PTMs in EC permeability is not fully understood.
• MAGI1 is a known junctional molecule in endothelial cells.

Purpose of the Study:

• To investigate the roles of p90RSK and MAGI1-PTMs in regulating endothelial cell permeability.
• To explore the impact of p90RSK activation on tumor vessel leakiness.
• To elucidate the connection between MAGI1, the Hippo pathway, and EC permeability.

Main Methods:

• Electric cell-substrate impedance sensing (ECIS) to measure EC permeability.
• Overexpression of dominant-negative p90RSK and MAGI1 mutants (S741A, K931R).
• siRNA-mediated knockdown of MAGI1.
• Quantitative PCR and Western blotting for LATS1/2, YAP/TAZ.
• In vivo studies using a p90RSK inhibitor (FMK-MEA) in tumor models.

Main Results:

• Thrombin-induced EC permeability was decreased by dominant-negative p90RSK or MAGI1-S741A mutant.
• EC permeability was increased by p90RSK overexpression, MAGI1 knockdown, or MAGI1-K931R mutant.
• MAGI1 depletion upregulated LATS1/2, inhibiting YAP/TAZ and increasing EC permeability.
• FMK-MEA significantly inhibited tumor vessel leakiness in vivo at a non-toxic dose.

Conclusions:

• p90RSK-mediated MAGI1 PTMs are crucial regulators of EC permeability.
• The Hippo pathway (LATS1/2, YAP/TAZ) is involved in MAGI1-regulated EC permeability.
• p90RSK activation contributes to tumor vessel leakiness, suggesting a therapeutic target.