Biomedical subjects

Y I Wu

Publications and source records attributed to Y I Wu.

4 recordsLinked to original sources

PubMed2001

Type I collagen stabilization of matrix metalloproteinase-2.

The activity of matrix metalloproteinase-2 (MMP-2) is regulated stringently on the posttranslational level. MMP-2 efficiently undergoes autolysis into inactive polypeptides in vitro, prompting the hypothesis that MMP-2 autolysis may function as an alternative mechanism for posttranslational control of MMP-2 in vivo. Moreover, MMP-2 binds to intact type I collagen fibrils; however, the functional consequences of this interaction have not been fully elucidated. To test the hypothesis that MMP-2 binding to type I collagen functions as a positive regulator of MMP-2 proteolytic potential, the effect of type I collagen on MMP-2 activity, inhibition by tissue inhibitor of metalloproteinase-2 (TIMP-2), and enzyme stability was examined. Here, we report that purified MMP-2 binds but does not cleave intact type I collagen. The presence of type I collagen affects neither enzymatic activity against a quenched fluorescent peptide substrate nor the kinetics of inhibition by TIMP-2. However, MMP-2 is stabilized from autolysis in the presence of type I collagen, but not by elastin, fibrinogen, or laminin. These data provide biochemical evidence that MMP-2 exosite interactions with type I collagen may function in the posttranslational control of MMP-2 activity by reducing the rate of autolytic inactivation.

Autolysis↗

PubMed2001

Functional interplay between type I collagen and cell surface matrix metalloproteinase activity.

Type I collagen stimulation of pro-matrix metalloproteinase (pro-MMP)-2 activation by ovarian cancer cells involves beta(1) integrin receptor clustering; however, the specific cellular and biochemical events that accompany MMP processing are not well characterized. Collagenolysis is not required for stimulation of pro-MMP-2 activation, and denatured collagen does not elicit an MMP-2 activation response. Similarly, DOV13 cells bind to intact collagen utilizing both alpha(2)beta(1) and alpha(3)beta(1) integrins but interact poorly with collagenase-treated or thermally denatured collagen. Antibody-induced clustering of alpha(3)beta(1) strongly promotes activation of pro-MMP-2, whereas alpha(2)beta(1) integrin clustering has only marginal effects. Membrane-type 1 (MT1)-MMP is present on the DOV13 cell surface as both an active 55-kDa TIMP-2-binding species and a stable catalytically inactive 43-kDa form. Integrin clustering stimulates cell surface expression of MT1-MMP and co-localization of the proteinase to aggregated integrin complexes. Furthermore, cell surface proteolysis of the 55-kDa MT1-MMP species occurs in the absence of active MMP-2, suggesting MT1-MMP autolysis. Cellular invasion of type I collagen matrices requires collagenase activity, is blocked by tissue inhibitor of metalloproteinases-2 (TIMP-2) and collagenase-resistant collagen, is unaffected by TIMP-1, and is accompanied by pro-MMP-2 activation. Together, these data indicate that integrin stimulation of MT1-MMP activity is a rate-limiting step for type I collagen invasion and provide a mechanism by which this activity can be down-regulated following collagen clearance.

Cell Adhesion↗

PubMed1997

Perturbation of platelet adhesion to endothelial cells by plasminogen activation in vitro.

To investigate whether the endothelium-platelet interactions may be altered by plasminogen activation, cultured human umbilical vein endothelial cells (ECs) were treated with tissue-type plasminogen activator (t-PA) in the presence of plasminogen, and platelet adhesion to ECs was subsequently measured by using a tapered flow chamber. Our results demonstrated that platelets adhered more readily to t-PA treated EC monolayer than to the control monolayer at all shear stress levels tested. This phenomenon was treatment time-dependent and dose-dependent, and it could be blocked by adding plasmin inhibitors, such as epsilon-amino caproic acid and aprotinin. Adherent platelets on t-PA treated EC monolayer underwent more severe shape change than those on the control monolayer. While the extracellular matrix directly treated with t-PA attracted less platelets than the control matrix did, platelet adhesion to the matrix that was produced by t-PA-treated ECs was unaltered. These data suggest that t-PA treatment on ECs compromised antiplatelet-adhesion capability on their apical surface without altering the reactivity of their extracellular matrix towards platelets.

Blood Platelets↗

PubMed1994

Defining the heparin-binding domain of antithrombin.

Antithrombin is a serine protease inhibitor that participates in the inactivation and removal from the circulation of thrombin and a variety of other procoagulant serine proteases. Antithrombin is also the major plasma cofactor of heparin which exerts its therapeutic effect primarily through its ability to substantially increase the rate of inactivation by antithrombin of the procoagulant serine proteases. Binding of heparin to antithrombin is thus believed to be a prerequisite for this rate enhancement effect. Heparin binding to antithrombin is mediated by a well-defined unique heparin pentasaccharide sequence. Interaction between this pentasaccharide sequence and antithrombin induces a conformational change in antithrombin, an alteration that appears to be sufficient to explain the enhanced ability of antithrombin to inhibit factor Xa and related serine proteases, but not thrombin. Heparin species with longer polysaccharide chains appear to be required in order to enhance the inhibition of thrombin by antithrombin. This may be because the enhancement of this reaction requires that heparin interacts simultaneously with both the antithrombin and the thrombin molecules. This review describes the interactions between heparin and antithrombin, focusing on the antithrombin residues which are involved in the binding of heparin. The role of the heparin-induced conformational change in enhancing serine protease inhibition by antithrombin is also explored. Then, based on available data, an hypothesis is proposed to explain the mechanisms by which heparin accelerates the rate of inactivation by antithrombin of the various serine proteases.

Animals↗