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This article has been peer reviewed. It is the authors' final version prior to publication in Arteriosclerosis, Thrombosis, and Vascular Biology

Volume 31, Issue 12, December 2011, Pages 2775-2776.

The published version is available at DOI: 10.1161/ATVBAHA.111.238865. Copyright © Elsevier Inc.


In this issue, Sevigny and colleagues demonstrate that a protease-activated receptor 1 (PAR1)-PAR2 heterodimer regulates vascular smooth muscle cell (VSMC) hyperplasia following vascular injury 1. PARs belong to a family of G-protein coupled receptors that are proteolytically activated by a variety of proteases 2, 3. Cleavage of PARs results in intracellular signaling mediated by activation of various G proteins including G12/13, Gq, and Gi 2, 4-6. The PAR family consists of 4 members, PAR1-PAR4, with PARs 1, 3, and 4 being primarily activated by thrombin, while PAR2 is activated by trypsin and tryptase 2, 3. PAR1, originally identified as a thrombin receptor on platelets, is widely expressed and has been shown to regulate a multitude of physiological processes including platelet activation 7, 8, regulation of the endothelial cell barrier function 9, and proliferation and de-differentiation of VSMCs 10, 11. In addition to PAR1, these cells express other PARs 6. Importantly members of PAR family can physically interact and signal as functional heterodimers in order to regulate cell growth, proliferation and activation 12-15. PAR1 for example, has been shown to trans-activate PAR2 in human endothelial and COS-7 cells 15, while on the platelet PAR1 may heterodimerize with PAR4

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