Thrombin cleaves and activates the protease-activated receptor 2 dependent on thrombomodulin co-receptor availability

Area of Science:

• Biochemistry
• Cell Biology
• Immunology

Background:

• Protease-activated receptors (PARs) respond to proteolytic activity.
• Thrombin typically activates PAR1, PAR3, and PAR4, but not PAR2.
• The role of co-receptors like thrombomodulin (TM) in PAR2 activation by thrombin was unexplored.

Purpose of the Study:

• To investigate if TM facilitates thrombin-mediated cleavage and activation of PAR2.
• To determine the biological consequences of TM-dependent PAR2 activation.

Main Methods:

• Utilized 293T cells overexpressing PAR2 and TM.
• Engineered mutant constructs of TM and PAR2 to map interaction sites.
• Assessed NF-κB activation and cytokine release as indicators of PAR2 activity.

Main Results:

• Thrombin cleaved PAR2 in a TM-dependent manner, with efficiency comparable to trypsin.
• TM enhanced sustained PAR2 cleavage by thrombin, distinct from PAR1 kinetics.
• TM's EGF-like domain 5 and specific CS proteoglycan sites were crucial for PAR2 cleavage at Arginine 36.

Conclusions:

• TM acts as a co-receptor, enabling thrombin to cleave and activate PAR2.
• This activation triggers NF-κB signaling and the release of pro-inflammatory interleukin-8.
• TM's novel pro-inflammatory role in PAR2 activation suggests potential therapeutic targets for inflammatory and malignant conditions.