The role of beta-strand 5A of plasminogen activator inhibitor-1 in regulation of its latency transition and inhibitory activity by vitronectin.

Biochim Biophys Acta

Laboratory of Cellular Protein Science, Department of Molecular and Structural Biology, Aarhus University, Gustav Wieds vej 10C, DK-8000 Aarhus C, Denmark.

Published: June 2002

Plasminogen activator inhibitor-1 (PAI-1) is a potential target for anti-thrombotic and anti-cancer therapy. It circulates in plasma in a complex with vitronectin (VN). We have studied biochemical mechanisms for PAI-1 neutralisation and its modulation by VN, using site-directed mutagenesis and limited proteolysis. We demonstrate that VN, besides delaying conversion of PAI-1 to the inactive latent form, also protects PAI-1 against cold- and detergent-induced substrate behaviour and counteracts conversion of PAI-1 to inert forms by certain amphipathic organochemical compounds. VN protection against cold- and detergent-induced substrate behaviour is associated with inhibition of the proteolytic susceptibility of beta-strand 5A. Alanine substitution of a lysine residue placed centrally in beta-strand 5A implied a VN-induced acceleration of latency transition, instead of the normal delay. This substitution not only protects PAI-1 against neutralisation, but also counteracts VN-induced protection against neutralisation. We conclude that beta-strand 5A plays a crucial role in VN-regulation of PAI-1 activity.

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http://dx.doi.org/10.1016/s0167-4838(02)00312-6DOI Listing

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