Plasminogen activator inhibitor-1 (PAI-1), a member of the serine protease inhibitor (serpin) superfamily of proteins, circulates in a complex with vitronectin. Furthermore, these two proteins are co-localized in the ...Plasminogen activator inhibitor-1 (PAI-1), a member of the serine protease inhibitor (serpin) superfamily of proteins, circulates in a complex with vitronectin. Furthermore, these two proteins are co-localized in the extracellular matrix (ECM) in many different pathophysiological conditions. Though PAI-1 is a well-characterized inhibitor of serine proteases, recent emphasis has also focused on its protease-independent functions. Vitronectin, a multi-domain protein that binds a wide variety of ligands and proteins, exists in the circulation in a preferred monomeric state, while in the extracellular matrix it exists as a multimer resulting from an altered conformation. Though the mechanism for the conformational alterations and compartmentalization in tissues is unknown, there are a number of biomolecules including PAI-1 that appear to cause such changes. Experimental analysis has established that PAI-1 induces association of vitronectin to higher-order species in a concentration-dependent fashion [1]. This report extends our investigations into the mechanism of the interaction between vitronectin and PAI-1 to explore the physiological relevance of these higher-order complexes for cellular adhesion and migration. In this study, we evaluate the effects of the pericellular microenvironment on the functions of the multimeric complexes in a variety of relevant biological settings. Our findings underscore the importance of the variability of components within this microenvironment, including different receptors and ECM components, in governing the way in which the vitronectin/PAI-1 complex mediates cell-matrix interactions.展开更多
文摘Plasminogen activator inhibitor-1 (PAI-1), a member of the serine protease inhibitor (serpin) superfamily of proteins, circulates in a complex with vitronectin. Furthermore, these two proteins are co-localized in the extracellular matrix (ECM) in many different pathophysiological conditions. Though PAI-1 is a well-characterized inhibitor of serine proteases, recent emphasis has also focused on its protease-independent functions. Vitronectin, a multi-domain protein that binds a wide variety of ligands and proteins, exists in the circulation in a preferred monomeric state, while in the extracellular matrix it exists as a multimer resulting from an altered conformation. Though the mechanism for the conformational alterations and compartmentalization in tissues is unknown, there are a number of biomolecules including PAI-1 that appear to cause such changes. Experimental analysis has established that PAI-1 induces association of vitronectin to higher-order species in a concentration-dependent fashion [1]. This report extends our investigations into the mechanism of the interaction between vitronectin and PAI-1 to explore the physiological relevance of these higher-order complexes for cellular adhesion and migration. In this study, we evaluate the effects of the pericellular microenvironment on the functions of the multimeric complexes in a variety of relevant biological settings. Our findings underscore the importance of the variability of components within this microenvironment, including different receptors and ECM components, in governing the way in which the vitronectin/PAI-1 complex mediates cell-matrix interactions.
