ABC  Vol.3 No.1 , February 2013
The cellular microenvironment modulates the role of PAI-1 and vitronectin in mediating cell-matrix interactions

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.

Cite this paper: Goswami, S. , Thompson, L. , Wickman, L. and Peterson, C. (2013) The cellular microenvironment modulates the role of PAI-1 and vitronectin in mediating cell-matrix interactions. Advances in Biological Chemistry, 3, 114-132. doi: 10.4236/abc.2013.31015.

[1]   Minor, K.H. and Peterson, C.B. (2002) Plasminogen activator inhibitor type 1 promotes the self-association of vitronectin into complexes exhibiting altered incorporation into the extracellular matrix. Journal of Biological Chemistry, 277, 10337-10345. doi:10.1074/jbc.M109564200

[2]   Schvartz, I., Seger, D. and Shaltiel, S. (1999) Vitronectin. International Journal of Biochemistry & Cell Biology, 31, 539-544. doi:10.1016/S1357-2725(99)00005-9

[3]   Seiffert, D. (1997) Constitutive and regulated expression of vitronectin. Histology and Histopathology, 12, 787 797.

[4]   Volker, W., Hess, S., Vischer, P. and Preissner, K.T. (1993) Binding and processing of multimeric vitronectin by vascular endothelial cells. Journal of Histochemistry & Cytochemistry, 41, 1823-1832. doi:10.1177/41.12.7504009

[5]   Tomasini, B.R. and Mosher, D.F. (1988) Conformational states of vitronectin: Preferential expression of an antigenic epitope when vitronectin is covalently and noncovalently complexed with thrombin-antithrombin III or treated with urea. Blood, 72, 903-912.

[6]   De Boer, H.C., de Groot, P.G., Bouma, B.N. and Preissner, K.T. (1993) Ternary vitronectin-thrombin-antithro mbin III complexes in human plasma. Detection and mode of association. Journal of Biological Chemistry, 268, 1279-1283.

[7]   Barnes, D.W., Reing, J.E. and Amos, B. (1985) Heparin-binding properties of human serum spreading factor. Journal of Biological Chemistry, 260, 9117-9122.

[8]   Lane, D.A., Flynn, A.M., Pejler, G., Lindahl, U., Choay, J. and Preissner, K. (1987) Structural requirements for the neutralization of heparin-like saccharides by complement S protein/vitronectin. Journal of Biological Chemistry, 262, 16343-16348.

[9]   Hayashi, M., Akama, T., Kono, I. and Kashiwagi, H. (1985) Activation of vitronectin (serum spreading factor) binding of heparin by denaturing agents. Journal of Biochemistry, 98, 1135-1138.

[10]   Owensby, D.A., Morton, P.A., Wun, T.C. and Schwartz, A.L. (1991) Binding of plasminogen activator inhibitor type-1 to extracellular matrix of Hep G2 cells. Evidence that the binding protein is vitronectin. Journal of Biological Chemistry, 266, 4334-4340.

[11]   Lawrence, D.A., Palaniappan, S., Stefansson, S., Olson, S.T., Francis-Chmura, A.M., Shore, J.D. and Ginsburg, D. (1997) Characterization of the binding of different con formational forms of plasminogen activator inhibitor-1 to vitronectin. Implications for the regulation of pericellular proteolysis. Journal of Biological Chemistry, 272, 7676 7680. doi:10.1074/jbc.272.12.7676

[12]   Arroyo De Prada, N., Schroeck, F., Sinner, E.K., Mueh lenweg, B., Twellmeyer, J., Sperl, S., Wilhelm, O.G., Schmitt, M. and Magdolen, V. (2002) Interaction of plasminogen activator inhibitor type-1 (PAI-1) with vi tronectin. European Journal of Biochemistry, 269, 184 192. doi:10.1046/j.0014-2956.2002.02639.x

[13]   Tschopp, J., Masson, D., Schafer, S., Peitsch, M. and Preissner, K.T. (1988) The heparin binding domain of S-protein/vitronectin binds to complement components C7, C8, and C9 and perforin from cytolytic T-cells and inhibits their lytic activities. Biochemistry, 27, 4103 4109. doi:10.1021/bi00411a029

[14]   Kanse, S.M., Kost, C., Wilhelm, O.G., Andreasen, P.A. and Preissner, K.T. (1996) The urokinase receptor is a major vitronectin-binding protein on endothelial cells. Experimental Cell Research, 224, 344-353. doi:10.1006/excr.1996.0144

[15]   Huang, X., Wu, J., Spong, S. and Sheppard, D. (1998) The integrin alphavbeta6 is critical for keratinocyte migration on both its known ligand, fibronectin, and on vitronectin. Journal of Cell Science, 111, 2189-2195.

[16]   Dahm, L.M. and Bowers, C.W. (1998) Vitronectin regulates smooth muscle contractility via alphav and beta1 integrin. Journal of Cell Science, 111, 1175-1183.

[17]   Memmo, L.M. and McKeown-Longo, P. (1998) The al phavbeta5 integrin functions as an endocytic receptor for vitronectin. Journal of Cell Science, 111, 425-433.

[18]   Schnapp, L.M., Hatch, N., Ramos, D.M., Klimanskaya, I.V., Sheppard, D. and Pytela, R. (1995) The human in tegrin alpha 8 beta 1 functions as a receptor for tenascin, fibronectin, and vitronectin. Journal of Biological Chemistry, 270, 23196-23202. doi:10.1074/jbc.270.39.23196

[19]   Nishimura, S.L., Sheppard, D. and Pytela, R. (1994) Integrin alpha v beta 8. Interaction with vitronectin and functional divergence of the beta 8 cytoplasmic domain. Journal of Biological Chemistry, 269, 28708-28715.

[20]   Boettiger, D., Lynch, L., Blystone, S. and Huber, F. (2001) Distinct ligand-binding modes for integrin al pha(v)beta(3)-mediated adhesion to fibronectin versus vi tronectin. Journal of Biological Chemistry, 276, 31684 31690. doi:10.1074/jbc.M103997200

[21]   Podor, T.J., Campbell, S., Chindemi, P., Foulon, D.M., Farrell, D.H., Walton, P.D., Weitz, J.I. and Peterson, C.B. (2002) Incorporation of vitronectin into fibrin clots. Evidence for a binding interaction between vitronectin and gamma A/gamma’ fibrinogen. Journal of Biological Che mistry, 277, 7520-7528. doi:10.1074/jbc.M109677200

[22]   Eitzman, D.T., Westrick, R.J., Nabel, E.G. and Ginsburg, D. (2000) Plasminogen activator inhibitor-1 and vitronectin promote vascular thrombosis in mice. Blood, 95, 577-580.

[23]   Jang, Y.C., Tsou, R., Gibran, N.S. and Isik, F.F. (2000) Vitronectin deficiency is associated with increased wound fibrinolysis and decreased microvascular angiogenesis in mice. Surgery, 127, 696-704. doi:10.1067/msy.2000.105858

[24]   Kanse, S.M., Matz, R.L., Preissner, K.T. and Peter, K. (2004) Promotion of leukocyte adhesion by a novel in teraction between vitronectin and the beta2 integrin Mac-1 (alphaMbeta2, CD11b/CD18). Arteriosclerosis, Thrombosis, and Vascular Biology, 24, 2251-2256. doi:10.1161/01.ATV.0000146529.68729.8b

[25]   Hess, S., Kanse, S.M., Kost, C. and Preissner, K.T. (1995) The versatility of adhesion receptor ligands in haemosta sis: Morpho-regulatory functions of vitronectin. Throm bosis and Haemostasis, 74, 258-265.

[26]   Barczyk, M., Carracedo, S. and Gullberg, D. (2010) In tegrins. Cell and Tissue Research, 339, 269-280. doi:10.1007/s00441-009-0834-6

[27]   Felding-Habermann, B. and Cheresh, D.A. (1993) Vitronectin and its receptors. Current Opinion in Cell Biology, 5, 864-868. doi:10.1016/0955-0674(93)90036-P

[28]   Lawrence, D., Strandberg, L., Grundstrom, T. and Ny, T. (1989) Purification of active human plasminogen activator inhibitor 1 from Escherichia coli. Comparison with natural and recombinant forms purified from eucaryotic cells. European Journal of Biochemistry, 186, 523-533. doi:10.1111/j.1432-1033.1989.tb15238.x

[29]   Estreicher, A., Muhlhauser, J., Carpentier, J.L., Orci, L. and Vassalli, J.D. (1990) The receptor for urokinase type plasminogen activator polarizes expression of the prote ase to the leading edge of migrating monocytes and pro motes degradation of enzyme inhibitor complexes. Journal of Cell Biology, 111, 783-792. doi:10.1083/jcb.111.2.783

[30]   Vassalli, J.D., Sappino, A.P. and Belin, D. (1991) The plasminogen activator/plasmin system. Journal of Clinical Investigation, 88, 1067-1072. doi:10.1172/JCI115405

[31]   Waltz, D.A., Natkin, L.R., Fujita, R.M., Wei, Y. and Chapman, H.A. (1997) Plasmin and plasminogen activator inhibitor type 1 promote cellular motility by regulating the interaction between the urokinase receptor and vitronectin. Journal of Clinical Investigation, 100, 58-67. doi:10.1172/JCI119521

[32]   Stahl, A. and Mueller, B.M. (1997) Melanoma cell migration on vitronectin: Regulation by components of the plasminogen activation system. International Journal of Cancer, 71, 116-122. doi:10.1002/(SICI)1097-0215(19970328)71:1<116::AID-IJC19>3.0.CO;2-G

[33]   Stefansson, S. and Lawrence, D.A. (1996) The serpin PAI-1 inhibits cell migration by blocking integrin alpha V beta 3 binding to vitronectin. Nature, 383, 441-443. doi:10.1038/383441a0

[34]   Bajou, K., Noel, A., Gerard, R.D., Masson, V., Brunner, N., Holst-Hansen, C., Skobe, M., Fusenig, N.E., Carme liet, P., Collen, D. and Foidart, J.M. (1998) Absence of host plasminogen activator inhibitor 1 prevents cancer invasion and vascularization. Nature Medicine, 4, 923 928. doi:10.1038/nm0898-923

[35]   Gutierrez, L.S., Schulman, A., Brito-Robinson, T., Noria, F., Ploplis, V.A. and Castellino, F.J. (2000) Tumor de velopment is retarded in mice lacking the gene for urokinase-type plasminogen activator or its inhibitor, plasminogen activator inhibitor-1. Cancer Research, 60, 5839-5847.

[36]   Stefansson, S., Petitclerc, E., Wong, M.K., McMahon, G.A., Brooks, P.C. and Lawrence, D.A. (2001) Inhibition of angiogenesis in vivo by plasminogen activator inhibi tor-1. Journal of Biological Chemistry, 276, 8135-8141. doi:10.1074/jbc.M007609200

[37]   McMahon, G.A., Petitclerc, E., Stefansson, S., Smith, E., Wong, M.K., Westrick, R.J., Ginsburg, D., Brooks, P.C. and Lawrence, D.A. (2001) Plasminogen activator inhibitor-1 regulates tumor growth and angiogenesis. Journal of Biological Chemistry, 276, 33964-33968. doi:10.1074/jbc.M105980200

[38]   Devy, L., Blacher, S., Grignet-Debrus, C., Bajou, K., Masson, V., Gerard, R.D., Gils, A., Carmeliet, G., Carmeliet, P., Declerck, P.J., Noel, A., and Foidart, J.M. (2002) The pro or antiangiogenic effect of plasminogen activator inhibitor 1 is dose dependent. FASEB Journal, 16, 147-154. doi:10.1096/fj.01-0552com

[39]   Stockmann, A., Hess, S., Declerck, P., Timpl, R. and Preissner, K.T. (1993) Multimeric vitronectin. Identification and characterization of conformation-dependent self association of the adhesive protein. Journal of Biological Chemistry, 268, 22874-22882.

[40]   Seiffert, D. and Schleef, R.R. (1996) Two functionally distinct pools of vitronectin (Vn) in the blood circulation: identification of a heparin-binding competent population of Vn within platelet alpha-granules. Blood, 88, 552-560.

[41]   Hogasen, K., Mollnes, T.E. and Harboe, M. (1992) Hepa rin-binding properties of vitronectin are linked to complex formation as illustrated by in vitro polymerization and binding to the terminal complement complex. Journal of Biological Chemistry, 267, 23076-23082.

[42]   Seiffert, D. and Loskutoff, D.J. (1996) Type 1 plasmino gen activator inhibitor induces multimerization of plasma vitronectin. A suggested mechanism for the generation of the tissue form of vitronectin in vivo. Journal of Biological Chemistry, 271, 29644-29651. doi:10.1074/jbc.271.47.29644

[43]   Podor, T.J., Shaughnessy, S.G., Blackburn, M.N. and Peterson, C.B. (2000) New insights into the size and stoichiometry of the plasminogen activator inhibitor type 1. vitronectin complex. Journal of Biological Chemistry, 275, 25402-25410. doi:10.1074/jbc.M000362200

[44]   Minor, K.H., Schar, C.R., Blouse, G.E., Shore, J.D., Lawrence, D.A., Schuck, P. and Peterson, C.B. (2005) A mechanism for assembly of complexes of vitronectin and plasminogen activator inhibitor-1 from sedimentation velocity analysis. Journal of Biological Chemistry, 280, 28711-28720. doi:10.1074/jbc.M500478200

[45]   Balbo, A., Minor, K.H., Velikovsky, C.A., Mariuzza, R. A., Peterson, C.B. and Schuck, P. (2005) Studying multi protein complexes by multisignal sedimentation velocity analytical ultracentrifugation. Proceedings of the National Academy of Sciences of the USA, 102, 81-86. doi:10.1073/pnas.0408399102

[46]   Nakamura, T., Tanaka, N., Higuma, N., Kazama, T., Kobayashi, I. and Yokota, S. (1996) The localization of plasminogen activator inhibitor-1 in glomerular subepi thelial deposits in membranous nephropathy. Journal of the American Society of Nephrology, 7, 2434-2444.

[47]   Inuzuka, S., Ueno, T., Torimura, T., Tamaki, S., Sugawara, H., Sakata, R., Kusaba, N., Sata, M., and Tanikawa, K. (1997) The significance of colocalization of plasmi nogen activator inhibitor-1 and vitronectin in hepatic fibrosis. Scandinavian Journal of Gastroenterology, 32, 1052-1060. doi:10.3109/00365529709011224

[48]   Stoop, A.A., Lupu, F. and Pannekoek, H. (2000) Colo calization of thrombin, PAI-1, and vitronectin in the atherosclerotic vessel wall: A potential regulatory me chanism of thrombin activity by PAI-1/vitronectin com plexes. Arteriosclerosis, Thrombosis, and Vascular Biol ogy, 20, 1143-1149. doi:10.1161/01.ATV.20.4.1143

[49]   Thompson, L.C., Goswami, S., Ginsberg, D.S., Day, D.E., Verhamme, I.M. and Peterson, C.B. (2011) Metals affect the structure and activity of human plasminogen activator inhibitor-1. Protein Science, 20, PMC3048421.

[50]   Thompson, L.C., Goswami, S., Ginsberg, D.S., Day, D.E., Verhamme, I.M. and Peterson, C.B. (2011) Metals affect the structure and activity of human plasminogen activator inhibitor-1. I. Modulation of stability and protease inhibition. Protein Science, 20, 353-365. doi:10.1002/pro.568

[51]   Dahlback, B. and Podack, E.R. (1985) Characterization of human S protein, an inhibitor of the membrane attack complex of complement. Demonstration of a free reactive thiol group. Biochemistry, 24, 2368-2374. doi:10.1021/bi00330a036

[52]   Zhuang, P., Blackburn, M.N. and Peterson, C.B. (1996) Characterization of the denaturation and renaturation of human plasma vitronectin. I. Biophysical characterization of protein unfolding and multimerization. Journal of Biological Chemistry, 271, 14323-14332. doi:10.1074/jbc.271.24.14323

[53]   Lynn, G.W., Heller, W.T., Mayasundari, A., Minor, K.H. and Peterson, C.B. (2005) A model for the three-dimen sional structure of human plasma vitronectin from small angle scattering measurements. Biochemistry, 44, 565 574. doi:10.1021/bi048347s

[54]   Preissner, K.T., Wassmuth, R. and Muller-Berghaus, G. (1985) Physicochemical characterization of human S protein and its function in the blood coagulation system. Biochemical Journal, 231, 349-355.

[55]   Shaffer, M.C., Foley, T.P. and Barnes, D.W. (1984) Quantitation of spreading factor in human biologic fluids. Journal of Laboratory and Clinical Medicine, 103, 783 791.

[56]   Barnes, D.W., Silnutzer, J., See, C. and Shaffer, M. (1983) Characterization of human serum spreading factor with monoclonal antibody. Proceedings of the National Academy of Sciences of the USA, 80, 1362-1366.

[57]   Edgell, C.J., McDonald, C.C. and Graham, J.B. (1983) Permanent cell line expressing human factor VIII-related antigen established by hybridization. Proceedings of the National Academy of Sciences of the USA, 80, 3734 3737. doi:10.1073/pnas.80.12.3734

[58]   Emeis, J.J. and Edgell, C.J. (1988) Fibrinolytic properties of a human endothelial hybrid cell line (Ea.hy926). Blood, 71, 1669-1675.

[59]   Podor, T.J., Peterson, C.B., Lawrence, D.A., Stefansson, S., Shaughnessy, S.G., Foulon, D.M., Butcher, M. and Weitz, J.I. (2000) Type 1 plasminogen activator inhibitor binds to fibrin via vitronectin. Journal of Biological Chemistry, 275, 19788-19794. doi:10.1074/jbc.M908079199

[60]   Huang, Y., Haraguchi, M., Lawrence, D.A., Border, W.A., Yu, L. and Noble, N.A. (2003) A mutant, nonin hibitory plasminogen activator inhibitor type 1 decreases matrix accumulation in experimental glomerulonephritis, Journal of Clinical Investigation, 112, 379-388.

[61]   Kadler, K.E., Baldock, C., Bella, J. and Boot-Handford, R.P. (2007) Collagens at a glance. Journal of Cell Science, 120, 1955-1958. doi:10.1242/jcs.03453

[62]   Than, M.E., Henrich, S., Huber, R., Ries, A., Mann, K., Kuhn, K., Timpl, R., Bourenkov, G.P., Bartunik, H.D. and Bode, W. (2002) The 1.9-A crystal structure of the noncollagenous (NC1) domain of human placenta colla gen IV shows stabilization via a novel type of covalent Met-Lys cross-link. Proceedings of the National Academy of Sciences of the USA, 99, 6607-6612. doi:10.1073/pnas.062183499

[63]   Gebb, C., Hayman, E.G., Engvall, E. and Ruoslahti, E. (1986) Interaction of vitronectin with collagen. Journal of Biological Chemistry, 261, 16698-16703.

[64]   Heremans, A., van der Schueren, B., de Cock, B., Paulsson, M., Cassiman, J.J., van den Berghe, H. and David, G. (1989) Matrix-associated heparan sulfate proteoglycan: Core protein-specific monoclonal antibodies decorate the pericellular matrix of connective tissue cells and the stromal side of basement membranes. Journal of Cell Biology, 109, 3199-3211. doi:10.1083/jcb.109.6.3199

[65]   Hassell, J.R., Robey, P.G. Barrach, H.J., Wilczek, J. Rennard, S.I. and Martin, G.R. (1980) Isolation of a heparan sulfate-containing proteoglycan from basement membrane. Proceedings of the National Academy of Sciences of the USA, 77, 4494-4498.

[66]   Fujiwara, S., Wiedemann, H., Timpl, R., Lustig, A. and Engel, J. (1984) Structure and interactions of heparan sulfate proteoglycans from a mouse tumor basement membrane. European Journal of Biochemistry, 143, 145 157. doi:10.1111/j.1432-1033.1984.tb08353.x

[67]   Gallagher, J.T., Lyon, M. and Steward, W.P. (1986) Structure and function of heparan sulphate proteoglycans. Biochemical Journal, 236, 313-325.

[68]   Preissner, K.T. and Muller-Berghaus, G. (1987) Neutralization and binding of heparin by S protein/vitronectin in the inhibition of factor Xa by antithrombin III. Involvement of an inducible heparin-binding domain of S protein/vitronectin. Journal of Biological Chemistry, 262, 12247-12253.

[69]   Zhuang, P., Chen, A.I. and Peterson, C.B. (1997) Native and multimeric vitronectin exhibit similar affinity for heparin. Differences in heparin binding properties in duced upon denaturation are due to self-association into a multivalent form. Journal of Biological Chemistry, 272, 6858-6867. doi:10.1074/jbc.272.11.6858

[70]   Ehrlich, H.J., Keijer, J., Preissner, K.T., Gebbink, R.K. and Pannekoek, H. (1991) Functional interaction of plasminogen activator inhibitor type 1 (PAI-1) and heparin. Biochemistry, 30, 1021-1028. doi:10.1021/bi00218a020

[71]   Zhou, A., Huntington, J.A., Pannu, N.S., Carrell, R.W. and Read, R.J. (2003) How vitronectin binds PAI-1 to modulate fibrinolysis and cell migration. Nature Structural & Molecular Biology, 10, 541-544. doi:10.1038/nsb943

[72]   Blouse, G.E., Dupont, D.M., Schar, C.R., Jensen, J.K., Minor, K.H., Anagli, J.Y., Gardsvoll, H., Ploug, M., Peterson, C.B. and Andreasen, P.A. (2009) Interactions of plasminogen activator inhibitor-1 with vitronectin involve an extensive binding surface and induce mutual confor mational rearrangements (dagger). Biochemistry, 48, 1723 1735. doi:10.1021/bi8017015

[73]   Lawrence, D.A., Berkenpas, M.B., Palaniappan, S. and Ginsburg, D. (1994) Localization of vitronectin binding domain in plasminogen activator inhibitor-1. Journal of Biological Chemistry, 269, 15223-15228.

[74]   Deng, G., Curriden, S. A., Wang, S., Rosenberg, S., and Loskutoff, D. J. (1996) Is plasminogen activator inhibitor-1 the molecular switch that governs urokinase receptor-mediated cell adhesion and release? Journal of Cell Biology, 134, 1563-1571. doi:10.1083/jcb.134.6.1563

[75]   Seiffert, D. and Smith, J.W. (1997) The cell adhesion domain in plasma vitronectin is cryptic. Journal of Biological Chemistry, 272, 13705-13710. doi:10.1074/jbc.272.21.13705

[76]   Okumura, Y., Kamikubo, Y., Curriden, S.A., Wang, J., Kiwada, T., Futaki, S., Kitagawa, K. and Loskutoff, D.J. (2002) Kinetic analysis of the interaction between vitronectin and the urokinase receptor. Journal of Biological Chemistry, 277, 9395-9404. doi:10.1074/jbc.M111225200

[77]   Humphries, J.D., Byron, A. and Humphries, M.J. (2006) Integrin ligands at a glance. Journal of Cell Science, 119, 3901-3903. doi:10.1242/jcs.03098

[78]   Aota, S., Nomizu, M. and Yamada, K.M. (1994) The short amino acid sequence Pro-His-Ser-Arg-Asn in human fibronectin enhances cell-adhesive function. Journal of Biological Chemistry, 269, 24756-24761.

[79]   Kim, S., Bell, K., Mousa, S.A. and Varner, J.A. (2000) Regulation of angiogenesis in vivo by ligation of integrin alpha5beta1 with the central cell-binding domain of fi bronectin. American Journal of Pathology, 156, 1345 1362. doi:10.1016/S0002-9440(10)65005-5

[80]   Nip, J., Rabbani, S.A., Shibata, H.R. and Brodt, P. (1995) Coordinated expression of the vitronectin receptor and the urokinase-type plasminogen activator receptor in me tastatic melanoma cells. Journal of Clinical Investigation, 95, 2096-2103. doi:10.1172/JCI117897

[81]   Kjoller, L., Kanse, S.M., Kirkegaard, T., Rodenburg, K.W., Ronne, E., Goodman, S.L., Preissner, K.T., Ossowski, L. and Andreasen, P.A. (1997) Plasminogen activator inhibitor-1 represses integrin and vitronectin mediated cell migration independently of its function as an inhibitor of plasminogen activation. Experimental Cell Research, 232, 420-429. doi:10.1006/excr.1997.3540

[82]   Kumar, C.C. (2003) Integrin alpha v beta 3 as a therapeu tic target for blocking tumor-induced angiogenesis. Cur rent Drug Targets, 4, 123-131. doi:10.2174/1389450033346830

[83]   Weidner, N., Semple, J.P., Welch, W.R. and Folkman, J. (1991) Tumor angiogenesis and metastasis—Correlation in invasive breast carcinoma. New England Journal of Medicine, 324, 1-8. doi:10.1056/NEJM199101033240101

[84]   Reardon, D.A., Nabors, L.B., Stupp, R. and Mikkelsen, T. (2008) Cilengitide: An integrin-targeting arginine-gly cine-aspartic acid peptide with promising activity for glioblastoma multiforme. Expert Opinion on Investigational Drugs, 17, 1225-1235. doi:10.1517/13543784.17.8.1225

[85]   Wu, H., Beuerlein, G., Nie, Y., Smith, H., Lee, B.A., Hensler, M., Huse, W.D. and Watkins, J.D. (1998) Step wise in vitro affinity maturation of Vitaxin, an alphav beta3-specific humanized mAb. Proceedings of the National Academy of Sciences of the USA, 95, 6037-6042. doi:10.1073/pnas.95.11.6037

[86]   Trikha, M., Zhou, Z., Nemeth, J.A., Chen, Q., Sharp, C., Emmell, E., Giles-Komar, J. and Nakada, M.T. (2004) CNTO 95, a fully human monoclonal antibody that inhib its alphav integrins, has antitumor and antiangiogenic ac tivity in vivo. International Journal of Cancer, 110, 326 335. doi:10.1002/ijc.20116

[87]   Sepp, N.T., Li, L.J., Lee, K.H., Brown, E.J., Caughman, S.W., Lawley, T.J. and Swerlick, R.A. (1994) Basic fi broblast growth factor increases expression of the alpha v beta 3 integrin complex on human microvascular endo thelial cells. Journal of Investigative Dermatology, 103, 295-299. doi:10.1111/1523-1747.ep12394617

[88]   Swerlick, R.A., Brown, E.J., Xu, Y., Lee, K.H., Manos, S. and Lawley, T.J. (1992) Expression and modulation of the vitronectin receptor on human dermal microvascular endothelial cells. Journal of Investigative Dermatology, 99, 715-722. doi:10.1111/1523-1747.ep12614207

[89]   Brooks, P.C., Clark, R.A. and Cheresh, D.A. (1994) Re quirement of vascular integrin alpha v beta 3 for angiogenesis. Science, 264, 569-571. doi:10.1126/science.7512751

[90]   Friedlander, M., Brooks, P.C., Shaffer, R.W., Kincaid, C.M., Varner, J.A. and Cheresh, D.A. (1995) Definition of two angiogenic pathways by distinct alpha v integrins. Science, 270, 1500-1502. doi:10.1126/science.270.5241.1500

[91]   Choi, S., Vilaire, G., Marcinkiewicz, C., Winkler, J.D., Bennett, J.S. and DeGrado, W.F. (2007) Small molecule inhibitors of integrin alpha2beta1. Journal of Medicinal Chemistry, 50, 5457-5462. doi:10.1021/jm070252b

[92]   McCall-Culbreath, K.D. and Zutter, M.M. (2008) Colla gen receptor integrins: Rising to the challenge. Current Drug Targets, 9, 139-149. doi:10.2174/138945008783502494

[93]   Huai, Q., Zhou, A., Lin, L., Mazar, A.P., Parry, G.C., Callahan, J., Shaw, D.E., Furie, B., Furie, B.C. and Huang, M. (2008) Crystal structures of two human vi tronectin, urokinase and urokinase receptor complexes. Nature Structural & Molecular Biology, 15, 422-423. doi:10.1038/nsmb.1404

[94]   Stefansson, S., Muhammad, S., Cheng, X.F., Battey, F.D., Strickland, D.K. and Lawrence, D.A. (1998) Plasminogen activator inhibitor-1 contains a cryptic high affinity bind ing site for the low density lipoprotein receptor-related protein. Journal of Biological Chemistry, 273, 6358 6366. doi:10.1074/jbc.273.11.6358

[95]   Brown, S.L., Lundgren, C.H., Nordt, T. and Fujii, S. (1994) Stimulation of migration of human aortic smooth muscle cells by vitronectin: implications for atherosclero sis. Cardiovascular Research, 28, 1815-1820. doi:10.1093/cvr/28.12.1815

[96]   Kim, J.P., Zhang, K., Chen, J.D., Kramer, R.H. and Woodley, D.T. (1994) Vitronectin-driven human kerati nocyte locomotion is mediated by the alpha v beta 5 integrin receptor. Journal of Biological Chemistry, 269, 26926-26932.

[97]   Roca-Cusachs, P., Gauthier, N.C., Del Rio, A. and Sheetz, M.P. (2009) Clustering of alpha(5)beta(1) integrins determines adhesion strength whereas alpha(v)beta(3) and talin enable mechanotransduction. Proceedings of the National Academy of Sciences of the USA, 106, 16245 16250.