Matricellular protein CCN1/CYR61: a new player in inflammation and leukocyte trafficking.

Cystein-rich protein 61 (CYR61/CCN1) is a component of the extracellular matrix, which is produced and secreted by several cell types including endothelial cells, fibroblasts and smooth muscle cells. CCN1 has been implicated in leukocyte migration and the inflammatory process, but it is also involved in cardiovascular development and carcinogenesis. It exerts its functions through binding to multiple integrins present in many different cell types. This multiplicity in function is now known to contribute to the diverse array of cellular processes it can regulate. The expression of CCN1 is tightly regulated by cytokines and growth factors. However, CCN1 can directly modulate cell adhesion and migratory processes whilst simultaneously regulating the production of other cytokines and chemokines through paracrine and autocrine feedback loops. This complex functionality of CCN1 has highlighted the pivotal role this molecule can play in regulating the immunosurveillance process. Furthermore, CCN1 has now emerged as an important partner when targeting components of the infectious or chronic inflammatory disease processes such as atherosclerosis or rheumatoid arthritis. This review will focus on CYR61/CCN1 and its ability to control the migration of leukocytes, the production of cytokines and cell proliferation or senescence at the site of inflammation.