alphav integrin processing interferes with the cross-talk between alphavbeta5/beta6 and alpha2beta1 integrins.

摘要

BACKGROUND INFORMATION: Previous studies have reported that cross-talk between integrins may be an important regulator of integrin-ligand binding and subsequent signalling events that control a variety of cell functions in many tissues. We previously demonstrated that alphavbeta5/beta6 integrin represses alpha2beta1-dependent cell migration. The alphav subunits undergo an endoproteolytic cleavage by protein convertases, whose role in tumoral invasion has remained controversial. RESULTS: Inhibition of convertases by the convertase inhibitor alpha1-PDX (alpha1-antitrypsin Portland variant), leading to the cell-surface expression of an uncleaved form of the alphav integrin, stimulated cell migration toward type I collagen. Under convertase inhibition, alpha2beta1 engagement led to enhanced phosphorylation of both FAK (focal adhesion kinase) and MAPK (mitogen-activated protein kinase). This outside-in signalling stimulation was associated with increased levels of activated beta1 integrin located in larger than usual focal-adhesion structures and a cell migration that was independent of the PI3K (phosphoinositide 3-kinase)/Akt (also called protein kinase B) pathway. CONCLUSIONS: The increase in cell migration observed upon convertases inhibition appears to be due to the up-regulation of beta1 integrins and to their location in larger focal-adhesion structures. The endoproteolytic cleavage of alphav subunits is necessary for alphavbeta5/beta6 integrin to control alpha2beta1 function and could thus play an essential role in colon cancer cell migration.