Cynthia B. Peterson Professor, Department of Biochemistry, Cellular & Molecular Biology Director, School of Genome Science and Technology Ph.D. University of Tennessee M407 Walters Life Sciences 1414 W. Cumberland Ave. Knoxville, TN 37996 cbpeters@utk.edu

Keywords:
Blood coagulation, heparin, serine protease inhibitors (serpins), fibrinolysis, extracellular matrix

Research Area:
The study of regulatory proteins within the human circulatory system that control a variety of processes, including formation/lysis of blood clots and aspects of humoral immunity and wound healing.

Description of Research:
Within the circulation, sophisticated networks of interactions between proteins and other macromolecules are important for maintaining stasis. Humoral defense mechanisms such as coagulation, fibrinolysis and complement-dependent components of cellular immunity are achieved by interactions of circulatory components with cell surfaces and extracellular matrix or basement membrane regions. Vitronectin, a protein that is found both in the circulation and in the extracellular matrix, interacts with a wide array of ligands that are involved in control of diverse processes including coagulation, fibrinolysis, tumor metastasis, the humoral immune response and cellular migration. Vitronectin binds to other macromolecules and participates in regulatory circuits to control these processes. Some target macromolecules that interact with vitronectin are heparin, PAI-1, proteases such as thrombin and urokinase-type plasminogen activator (uPA), serine protease inhibitor-protease complexes, the uPA receptor, and a sub-class of integrin receptors on the surface of cells. From this extensive list of interactions, several roles for vitronectin are proposed. For example: 1. it provides an adhesive function for interactions of cells with the matrix; 2. it serves in a pro-coagulant role by binding to heparin-like molecules on the vasculature and neutralizing their anticoagulant function; and 3. it controls the process of fibrinolysis or matrix degradation by maintaining protease inhibitor molecules in an active conformation or modulating interactions of cells with integrins and other receptors. Clearly, vitronectin plays diverse roles in the body.

The factors that control the binding interactions and determine activities of vitronectin in the circulation as well as in the matrix are important unsolved issues. We set forth the following as our working hypotheses regarding vitronectin complexes and their activities: 1. Complexes of vitronectin with biological targets (plasminogen activator inhibitor type 1 (PAI-1) or the antithrombin-thrombin pair) associate into higher order structures to give a "clustering" of ligand-binding sites. 2. Vitronectin complexes associate with the matrix and are recognized by cell-surface receptors, with a preference for higher order complexes over free, monomeric vitronectin. 3. Vitronectin is a multi-domain protein with distributed binding sites to control the dynamic processes of coagulation vs. fibrinolysis and binding vs. release from the matrix. To test these hypotheses, a broad spectrum of experimental approaches from molecular biology to biophysics are used.

Selected Publications:

• Minor, K. H., Schar, C. R., Blouse, G. E., Shore, J. D., Lawrence, D. A., Schuck, P., and Peterson, C. B. (2005) J. Biol. Chem., 280, 28711-28720. "A Mechanism for Assembly of Complexes of Vitronectin and Plasminogen Activator Inhibitor-1 from Sedimentation Velocity Analysis."


• Lynn, G. W., Heller, W. T., Mayasundari, A., Minor, K. H., and Peterson, C. B. (2005) Biochemistry 44, 565-574. "A Model for the Three-Dimensional Structure of Human Plasma Vitronectin from Small Angle Scattering Measurements."


• Balbo, A., Minor, K. H., Velikovsky, C. A., Mariuzza, R. A., Peterson, C. B., and Schuck, P. (2005) Proc. Natl. Acad. Sci. USA 102, 81-86. "Studying Multi-Protein Complexes by Multi-Signal Sedimentation Velocity Analytical Ultracentrifugation."


• Horn, N. A., Hurst, G. B., Mayasundari, A., Whittemore, N. A., Serpersu, E. H., and Peterson, C. B. (2004) J. Biol. Chem. 279, 35867-35878. "Assignment of the Four Disulfides in the N-terminal Somatomedin B Domain of Native Vitronectin Isolated from Human Plasma."


• Mayasundari, A., Whittemore, N. A., Serpersu. E. H. and Peterson, C. B. (2004) J. Biol. Chem. 279, 29359-29366. "The Solution Structure of the N-terminal Domain of Human Plasma Vitronectin: Location of Binding Sites that Regulate Fibrinolysis and Cell Migration."


• Gupta, V., Peterson, C. B, Dice, L. T., Uchiki, T., Racca, J., Guo, J.-t, Xu, Y., Hettich, R., Zhao, X., Rothstein, R., and Dealwis, C. (2004) Biochemistry 43, 8568-8578. "Sml1p is a Dimer in Solution: Characterization of Denaturation and Renaturation of Recombinant Sml1p."


• Minor, K. H., and Peterson, C. B. (2002) J. Biol. Chem. 277,10337-10345. "PAI-1 Promotes the Self-Association of Vitronectin into Complexes Exhibiting Altered Incorporation into the Extracellular Matrix."


• Podor, T. J., Campbell, S., Chindemi, P., Foulon, D. M., Farrell, D. H., Walton, P.D., Weitz, J. I., and Peterson, C. B. (2002) J. Biol. Chem. 277, 7520-7528. "Incorporation of Vitronectin into Fibrin Clots: Evidence for a Binding Interaction between Vitronectin and gA/g' Fibrinogen,"


• Xu, D., Baburaj, K., Peterson, C. B., and Xu, Y. (2001) Proteins: Structure, Function and Genetics, 44, 312-320. "A Model for the Three-Dimensional Structure of Vitronectin: Predictions for the Multi-Domain Protein from Threading and Docking."


• Gibson, A. D., and Peterson, C. B. (2001) Biochim. Biophys. Acta, 1545, 389-403. "Full Length and Truncated Forms of Vitronectin Provide Insight into Effects of Proteolytic Processing on Function."


• Podor, T. J., Shaughnessy, S. G., Blackburn, M. N. and Peterson, C. B. (2000) J. Biol. Chem. 275, 25402-25410. "New Insights into the Size and Stoichiometry of the Vitronectin:PAI-1 Complex."


• Podor, T. J., Peterson, C. B., Lawrence, D. A., Stefansson, S., Stephen G. Shaughnessy, S. G., Foulon, D. M., Butcher, M., and Weitz, J. I. (2000) J. Biol. Chem. 275, 19788-19794. "Plasminogen Activator Inhibitor Binds to Fibrin via Vitronectin."


• Gibson, A. D., Lamerdin, J. A., Zhuang, P., Baburaj, K., Serpersu, E. H. and Peterson, C. B.(1999) J. Biol. Chem. 274, 6432-6442. "Orientation of Heparin-Binding Sites in Native Vitronectin: Analyses of Ligand Binding to the Primary Glycosaminoglycan-binding Site Indicate that Putative Secondary Sites are Not Functional."