MKL1 fuels ROS-induced proliferation of vascular smooth muscle cells by modulating FOXM1 transcription

Area of Science:

• Cardiovascular Biology
• Molecular Mechanisms of Disease
• Cellular Signaling

Background:

• Reactive oxygen species (ROS) contribute to vascular injury and neointima formation by promoting vascular smooth muscle cell (VSMC) proliferation.
• The precise transcriptional mechanisms underlying ROS-mediated VSMC proliferation remain incompletely understood.

Purpose of the Study:

• To elucidate the transcriptional mechanism by which ROS stimulate VSMC proliferation.
• To investigate the role of MKL1 and its downstream targets in ROS-induced VSMC proliferation and neointima formation.

Main Methods:

• Utilized a mouse model of vascular injury with VSMC-specific MKL1 deletion.
• Employed pharmaceutical inhibition of MKL1 using CCG-1423.
• Performed gene expression analysis (PCR array) to identify MKL1 targets.
• Investigated protein-protein interactions (MKL1/E2F1) and phosphorylation events (ROS-induced MKL1 phosphorylation via MK2).
• Assessed VSMC proliferation in vitro and neointima formation in vivo.
• Correlated FOXM1 expression with VSMC proliferation in human restenosis specimens.

Main Results:

• VSMC-specific MKL1 deletion and MKL1 inhibition attenuated neointima formation in mice.
• Overexpression of MKL1 enhanced ROS-dependent VSMC proliferation, while MKL1 depletion inhibited it.
• FOXM1 was identified as a direct transcriptional target of MKL1, activated via interaction with E2F1.
• FOXM1 depletion abrogated MKL1-dependent VSMC proliferation.
• ROS-induced phosphorylation of MKL1 by MK2 was crucial for E2F1 interaction and FOXM1 transactivation.
• FOXM1 expression positively correlated with VSMC proliferation in human restenosis.

Conclusions:

• A redox-sensitive phosphorylation of MKL1 acts as a switch, activating FOXM1 transcription and mediating ROS-driven VSMC proliferation.
• The MK2/MKL1/FOXM1 signaling axis is a key mediator of ROS-fueled VSMC proliferation.
• Targeting the MK2/MKL1/FOXM1 pathway presents a potential therapeutic strategy for restenosis.