HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 280, Issue 40, 33819-33825, October 7, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/40/33819    most recent M506502200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Heeb, M. J. Articles by Ruan, L. Search for Related Content PubMed PubMed Citation Articles by Heeb, M. J. Articles by Ruan, L. Social Bookmarking                      What's this?

Down-regulation of Factor IXa in the Factor Xase Complex by Protein Z-dependent Protease Inhibitor^*

From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037

Protein Z-dependent protease inhibitor (ZPI) is a serpin inhibitor of coagulation factor (F) Xa dependent on protein Z, Ca²⁺, and phospholipids. In new studies, ZPI inhibited FIXa in the FXase complex. Since this observation could merely represent inhibition of the FXa product whose activity was measured, inhibition of FIXa was investigated five ways. 1) FXase incubation mixtures with/without ZPI/protein Z were diluted in EDTA; FXa activity was measured after reversal of its inhibition. 2) FXase incubation mixtures were immunoblotted for FXa product. 3) FX activation peptide region was ³H-labeled; release of ³H was used to measure FXase activity. 4) Activity was monitored in a FIXa-based clotting assay. 5) FIXa amidolytic activity was measured. In all cases, FIXa was inhibited by subphysiologic levels of ZPI. Unlike inhibition of FXa, inhibition of FIXa did not strictly require protein Z. Low concentrations of FVIIIa increased the efficiency of ZPI inhibition of FIXa; FVIIIa in molar excess was not protective of FIXa unless FIXa/FVIIIa interacted prior to ZPI exposure. Unusual time courses were observed for inhibition of both FIXa in the FXase complex and FXa in the prothrombinase complex. Activity loss stabilized in <100 s at a level dependent on ZPI concentration, suggesting equilibrium interactions rather than typical covalent serpin-protease interactions. Surface plasmon resonance binding experiments revealed binding and dissociation of ZPI/FIXa with of 9-12 nM, similar to the concentration of ZPI needed for 50% inhibition. ZPI may be an unusual physiologic regulator of both the intrinsic FXase and the prothrombinase complexes.

Received for publication, June 15, 2005 , and in revised form, July 28, 2005.

^* This work was supported by an Established Investigatorship from the American Heart Association (to M. J. H.), by National Institutes of Health Grants HL70002 (to M. J. H.) and M01 RR00833, and by the Stein Endowment Fund. Preliminary reports were presented at the American Society of Hematology meetings, December, 2002 and December, 2003. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Dept. of Molecular and Experimental Medicine, The Scripps Research Institute, MEM180, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, Tel.: 858-784-2185, Fax: 858-784-2113, E-mail: heeb{at}scripps.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				X. Huang, R. Swanson, G. J. Broze Jr., and S. T. Olson Kinetic Characterization of the Protein Z-dependent Protease Inhibitor Reaction with Blood Coagulation Factor Xa J. Biol. Chem., October 31, 2008; 283(44): 29770 - 29783. [Abstract] [Full Text] [PDF]

				A. R. Rezaie, J.-S. Bae, C. Manithody, S. H. Qureshi, and L. Yang Protein Z-dependent Protease Inhibitor Binds to the C-terminal Domain of Protein Z J. Biol. Chem., July 18, 2008; 283(29): 19922 - 19926. [Abstract] [Full Text] [PDF]

				J. Zhang, Y. Tu, L. Lu, N. Lasky, and G. J. Broze Jr Protein Z-dependent protease inhibitor deficiency produces a more severe murine phenotype than protein Z deficiency Blood, May 15, 2008; 111(10): 4973 - 4978. [Abstract] [Full Text] [PDF]

				E. L. Howard, K. C.D. Becker, C. P. Rusconi, and R. C. Becker Factor IXa Inhibitors as Novel Anticoagulants Arterioscler. Thromb. Vasc. Biol., April 1, 2007; 27(4): 722 - 727. [Abstract] [Full Text] [PDF]

				J. Corral, R. Gonzalez-Conejero, J. M. Soria, J. R. Gonzalez-Porras, E. Perez-Ceballos, R. Lecumberri, V. Roldan, J. C. Souto, A. Minano, D. Hernandez-Espinosa, et al. A nonsense polymorphism in the protein Z-dependent protease inhibitor increases the risk for venous thrombosis Blood, July 1, 2006; 108(1): 177 - 183. [Abstract] [Full Text] [PDF]