Interaction between integrin α5 and PDE4D regulates endothelial inflammatory signalling

Abstract

Atherosclerosis is primarily a disease of lipid metabolism and inflammation; however, it is also closely associated with endothelial extracellular matrix (ECM) remodelling, with fibronectin accumulating in the laminin–collagen basement membrane. To investigate how fibronectin modulates inflammation in arteries, we replaced the cytoplasmic tail of the fibronectin receptor integrin α5 with that of the collagen/laminin receptor integrin α2. This chimaera suppressed inflammatory signalling in endothelial cells on fibronectin and in knock-in mice. Fibronectin promoted inflammation by suppressing anti-inflammatory cAMP. cAMP was activated through endothelial prostacyclin secretion; however, this was ECM-independent. Instead, cells on fibronectin suppressed cAMP via enhanced phosphodiesterase (PDE) activity, through direct binding of integrin α5 to phosphodiesterase-4D5 (PDE4D5), which induced PP2A-dependent dephosphorylation of PDE4D5 on the inhibitory site Ser651. In vivo knockdown of PDE4D5 inhibited inflammation at athero-prone sites. These data elucidate a molecular mechanism linking ECM remodelling and inflammation, thereby identifying a new class of therapeutic targets.