CLIC1 and CLIC4 mediate endothelial S1P receptor signaling to facilitate Rac1 and RhoA activity and function

Area of Science:

• Endothelial cell biology
• Molecular signaling
• Vascular development

Background:

• Chloride intracellular channels 1 (CLIC1) and 4 (CLIC4) are present in endothelial cells and influence angiogenic processes.
• CLIC4 expression is vital for proper vascular development and function in mice.
• G protein-coupled receptor (GPCR) pathways are critical in vascular development and disease.

Purpose of the Study:

• To investigate the role of CLIC1 and CLIC4 in endothelial cells concerning GPCR signaling pathways.
• To determine how CLIC1 and CLIC4 mediate responses to sphingosine 1-phosphate (S1P) and its receptors (S1PRs).
• To elucidate the involvement of CLICs in regulating endothelial barrier function.

Main Methods:

• Utilized cultured endothelial cells to study CLIC1 and CLIC4 translocation and function.
• Investigated S1P-induced activation of small GTPases Rac1, RhoA, and other signaling outputs.
• Performed rescue experiments to assess the functional interchangeability of CLIC1 and CLIC4.
• Assessed the impact of CLICs on endothelial cell monolayer barrier function.

Main Results:

• CLIC1 and CLIC4 translocated to the plasma membrane in response to S1P.
• Both CLIC1 and CLIC4 were essential for S1P-induced Rac1 activation via S1PR1.
• CLIC1, but not CLIC4, was essential for S1P-induced RhoA activation via S1PR2 and S1PR3.
• CLIC1 and CLIC4 demonstrated distinct, non-interchangeable functions in GPCR signaling.
• CLIC-mediated mechanisms were critical for S1P-stimulated endothelial barrier function.

Conclusions:

• CLIC1 and CLIC4 are key regulators of GPCR signaling pathways in endothelial cells.
• CLICs play distinct roles in transducing signals from S1P receptors to small GTPases.
• These findings identify CLICs as novel mediators linking GPCRs to GTPases and vascular endothelial function.