1
|
Gruzdys V, Wang L, Wang D, Huang R, Sun XL. Investigation of cofactor activities of endothelial microparticle-thrombomodulin with liposomal surrogate. Biochem Biophys Res Commun 2023; 651:79-84. [PMID: 36801612 PMCID: PMC9992332 DOI: 10.1016/j.bbrc.2023.02.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 02/09/2023] [Indexed: 02/12/2023]
Abstract
Thrombomodulin (TM) is a type I transmembrane glycoprotein mainly expressed on the endothelial cells, where it binds thrombin to form the thrombin-TM complex that can activate protein C and thrombin-activable fibrinolysis inhibitor (TAFI) and induce anticoagulant and anti-fibrinolytic reactions, respectively. Cell activation and injury often sheds microparticles that contain membrane TM, which circulate in biofluids like blood. However, the biological function of circulating microparticle-TM is still unknown even though it has been recognized as a biomarker of endothelial cell injury and damage. In comparison with cell membrane, different phospholipids are exposed on the microparticle surface due to cell membrane ''flip-flop'' upon cell activation and injury. Liposomes can be used as a microparticle mimetics. In this report, we prepared TM-containing liposomes with different phospholipids as surrogates of endothelial microparticle-TM and investigated their cofactor activities. We found that liposomal TM with phosphatidylethanolamine (PtEtn) showed increased protein C activation but decreased TAFI activation in comparison to liposomal TM with phosphatidylcholine (PtCho). In addition, we investigated whether protein C and TAFI compete for the thrombin/TM complex on the liposomes. We found that protein C and TAFI did not compete for the thrombin/TM complex on the liposomes with PtCho alone and with low concentration (5%) of PtEtn and phosphatidylserine (PtSer), but competed each other on the liposomes with higher concentration (10%) of PtEtn and PtSer. These results indicate that membrane lipids affect protein C and TAFI activation and microparticle-TM may have different cofactor activities in comparison to cell membrane TM.
Collapse
Affiliation(s)
- Valentinas Gruzdys
- Department of Chemistry, Chemical and Biomedical Engineering, Center for Gene Regulation in Health and Disease (GRHD), Cleveland State University, Cleveland, OH, 44115, USA
| | - Lin Wang
- Department of Chemistry, Chemical and Biomedical Engineering, Center for Gene Regulation in Health and Disease (GRHD), Cleveland State University, Cleveland, OH, 44115, USA
| | - Dan Wang
- Department of Chemistry, Chemical and Biomedical Engineering, Center for Gene Regulation in Health and Disease (GRHD), Cleveland State University, Cleveland, OH, 44115, USA
| | - Rachel Huang
- Department of Chemistry, Chemical and Biomedical Engineering, Center for Gene Regulation in Health and Disease (GRHD), Cleveland State University, Cleveland, OH, 44115, USA
| | - Xue-Long Sun
- Department of Chemistry, Chemical and Biomedical Engineering, Center for Gene Regulation in Health and Disease (GRHD), Cleveland State University, Cleveland, OH, 44115, USA.
| |
Collapse
|
2
|
Serine protease dynamics revealed by NMR analysis of the thrombin-thrombomodulin complex. Sci Rep 2021; 11:9354. [PMID: 33931701 PMCID: PMC8087772 DOI: 10.1038/s41598-021-88432-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/07/2021] [Indexed: 01/04/2023] Open
Abstract
Serine proteases catalyze a multi-step covalent catalytic mechanism of peptide bond cleavage. It has long been assumed that serine proteases including thrombin carry-out catalysis without significant conformational rearrangement of their stable two-β-barrel structure. We present nuclear magnetic resonance (NMR) and hydrogen deuterium exchange mass spectrometry (HDX-MS) experiments on the thrombin-thrombomodulin (TM) complex. Thrombin promotes procoagulative fibrinogen cleavage when fibrinogen engages both the anion binding exosite 1 (ABE1) and the active site. It is thought that TM promotes cleavage of protein C by engaging ABE1 in a similar manner as fibrinogen. Thus, the thrombin-TM complex may represent the catalytically active, ABE1-engaged thrombin. Compared to apo- and active site inhibited-thrombin, we show that thrombin-TM has reduced μs-ms dynamics in the substrate binding (S1) pocket consistent with its known acceleration of protein C binding. Thrombin-TM has increased μs-ms dynamics in a β-strand connecting the TM binding site to the catalytic aspartate. Finally, thrombin-TM had doublet peaks indicative of dynamics that are slow on the NMR timescale in residues along the interface between the two β-barrels. Such dynamics may be responsible for facilitating the N-terminal product release and water molecule entry that are required for hydrolysis of the acyl-enzyme intermediate.
Collapse
|
3
|
Medina P, Bonet E, Navarro S, Martos L, Estellés A, Ferrando F, Vicente V, Bertina RM, España F. Effects of oral anticoagulant therapy and haplotype 1 of the endothelial protein C receptor gene on activated protein C levels. Thromb Haemost 2017; 107:448-57. [DOI: 10.1160/th11-07-0510] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 12/05/2011] [Indexed: 11/05/2022]
Abstract
SummaryOral anticoagulants (OACs) reduce activated protein C (APC) plasma levels less than those of protein C (PC) in lupus erythematosus and cardiac patients. Carriers of the H1 haplotype of the endothelial PC receptor gene (PROCR) have higher APC levels than non-carriers. We aimed to confirm these results in a large group of patients treated with OACs because of venous thromboembolism (VTE) and to assess whether the effect is influenced by the PROCR H1 haplotype. We evaluated APC, PC, and factor (F)II levels in 502 VTE patients (158 with and 344 without OACs) and in 322 healthy individuals. Mean APC, PC and FII levels were significantly lower in OAC patients than in patients not taking OACs. During anticoagulant therapy, the FII/PC ratios were independent of the PC values, whereas APC/FII and APC/PC ratios significantly increased when FII and PC levels decreased. Of the 22 OAC patients carrying the H1H1genotype, 11 (50%) showed APC/PCag ≥2.0 and 10 (45%) APC/ FIIag ratios ≥2.0, whereas for the 49 OAC patients non-carrying the H1 haplotype these figures were 6 (12%) and 4 (8%), respectively (p<0.001). Barium citrate adsorption of plasma from OAC patients showed that most of the circulating free and complexed APC, but only part of PCag, is fully carboxylated. In conclusion, during anticoagulant therapy VT patients have APC levels disproportionately higher than the corresponding PC levels, mainly due to the presence of the PROCR H1 haplotype. Furthermore, a sufficiently carboxylated PC Gla-domain seems to be essential for PC activation in vivo.
Collapse
|
4
|
Zhang H, Weingart J, Gruzdys V, Sun XL. Synthesis of an End-to-End Protein-Glycopolymer Conjugate via Bio-Orthogonal Chemistry. ACS Macro Lett 2016; 5:73-77. [PMID: 35668582 DOI: 10.1021/acsmacrolett.5b00805] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
We report the synthesis of an end-to-end protein-glycopolymer conjugate, namely, site-specific modification of recombinant thrombomodulin at the C-terminus with a chain-end-functionalized glycopolymer. Thrombomodulin (TM) is an endothelial membrane glycoprotein that acts as a major cofactor in the protein C anticoagulant pathway. To closely mimic the glycoprotein structural feature of native TM, we proposed a site-specific glyco-engineering of recombinant TM with a glycopolymer. Briefly, recombinant TM containing the epidermal growth factor (EGF)-like domains 4, 5, and 6 (rTM456) and a C-terminal azidohomoalanine was modified with a dibenzylcyclooctyne (DBCO) chain-end-functionalized glycopolymer via copper-free click chemistry to afford the end-to-end TM-glycopolymer conjugate. The TM glycoconjugation was confirmed with SDS-PAGE, Western blot, and protein C activation assay, respectively. The reported site-specific end-to-end protein glycopolymer conjugation approach facilitates uniform glycoconjugate formation via biocompatible chemistry and in high efficiency providing a rational strategy for generating an rTM-based anticoagulant agent.
Collapse
Affiliation(s)
- Hailong Zhang
- Department of Chemistry,
Chemical and Biomedical Engineering and Center for Gene Regulation
in Health and Disease, Cleveland State University, Cleveland, Ohio 44115, United States
| | - Jacob Weingart
- Department of Chemistry,
Chemical and Biomedical Engineering and Center for Gene Regulation
in Health and Disease, Cleveland State University, Cleveland, Ohio 44115, United States
| | - Valentinas Gruzdys
- Department of Chemistry,
Chemical and Biomedical Engineering and Center for Gene Regulation
in Health and Disease, Cleveland State University, Cleveland, Ohio 44115, United States
| | - Xue-Long Sun
- Department of Chemistry,
Chemical and Biomedical Engineering and Center for Gene Regulation
in Health and Disease, Cleveland State University, Cleveland, Ohio 44115, United States
| |
Collapse
|
5
|
Arlaud GJ, Colomb MG, Gagnon J. A functional model of the human C1 complex Emergence of a functional model. ACTA ACUST UNITED AC 2014; 8:106-11. [PMID: 25289811 DOI: 10.1016/0167-5699(87)90860-7] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Precise structural data on C1s-C1r-C1r-C1s, the catalytic subunit of C1 (the first component of the classical pathway of human complement), led to the emergence of a structural and functional model of this complex protease. Now with new structural information on the amino acid sequence of the protease responsible for C1 activation (C1r), Gérard Arlaud and his colleagues propose a refinement of their original C1 model, and an overall scheme of the intramolecular events associated with the activation and control of C1.
Collapse
Affiliation(s)
- G J Arlaud
- Département de Recherches Fondamentales (Unité INSERM 238), Laboratoire d'Immunochimie, Centre d'Etudes Nucléaires de Grenoble, 85X, 38041 Grenoble Cedex, France
| | - M G Colomb
- Département de Recherches Fondamentales (Unité INSERM 238), Laboratoire d'Immunochimie, Centre d'Etudes Nucléaires de Grenoble, 85X, 38041 Grenoble Cedex, France
| | - J Gagnon
- Conseil National de Recherches du Canada, Institut de Recherches en Biotechnologie, Montréal, Québec, Canada H4P 2RJ
| |
Collapse
|
6
|
Zhang H, Weingart J, Jiang R, Peng J, Wu Q, Sun XL. Bio-inspired liposomal thrombomodulin conjugate through bio-orthogonal chemistry. Bioconjug Chem 2013; 24:550-9. [PMID: 23458546 DOI: 10.1021/bc300399f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We report the synthesis of bioinspired liposomal thrombomodulin (TM) conjugates by chemoselective and site-specific liposomal conjugation of recombinant TM at C-terminus. TM is an endothelial cell membrane protein that acts as a major cofactor in the protein C anticoagulant pathway. To closely mimic membrane protein structural features of TM, we proposed membrane-mimetic re-expression of recombinant TM onto liposome. A recombinant TM containing the EGF-like 456 domains and an azidohomoalanine at C-terminus was expressed in E. coli. Conjugation of the recombinant TM onto liposome via Staudinger ligation and copper-free click chemistry were investigated as an optimal platform for exploring membrane protein TM's activity, respectively. The bioinspired liposomal TM conjugates were confirmed with Western blotting and protein C activation activity. The recombinant TM-liposome conjugates showed a 2-fold higher k(cat)/K(m) value for protein C activation than that of the recombinant TM alone, which indicated that the lipid membrane has a beneficiary effect on the recombinant TM's activity. The reported liposomal protein conjugate approach provides a rational design strategy for both studying membrane protein TM's functions and generating a membrane protein TM-based anticoagulant agent.
Collapse
Affiliation(s)
- Hailong Zhang
- Department of Chemistry, Cleveland State University, Cleveland, OH 44115, USA
| | | | | | | | | | | |
Collapse
|
7
|
Ma Y, Jiang R, Zhang H, Gruzdys V, Sun XL. Chemoselectively surface funtionalizable tethered bilayer lipid membrane for versatile membrane mimetic systems fabrication. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm15858b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
8
|
Della Valle P, Pavani G, D'Angelo A. The protein C pathway and sepsis. Thromb Res 2011; 129:296-300. [PMID: 22154246 DOI: 10.1016/j.thromres.2011.11.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Revised: 11/07/2011] [Accepted: 11/08/2011] [Indexed: 10/14/2022]
Abstract
After the discovery of the key components of the protein C (PC) pathway a beneficial effect on survival of the infusion of activated protein C (APC) in animal models of sepsis was demonstrated, leading to the development of recombinant human activated protein C (rh-APC) as a therapeutic agent. It soon became clear that rather than the anticoagulant and profibrinolytic activities of APC, its anti-inflammatory and cytoprotective properties played a major role in the treatment of patients with severe sepsis. Such properties affect the response to inflammation of endothelial cells and leukocytes and are exerted through binding of APC to at least five receptors with intracellular signaling. The main APC protective mechanism involves binding of the Gla-domain to the endothelial protein C receptor (EPCR) and cleavage of protease activated receptor 1 (PAR-1), eliciting suppression of proinflammatory cytokines synthesis and of intracellular proapoptotic pathways and activation of endothelial barrier properties. However, thrombin cleaves PAR-1 with much higher catalytic efficiency, followed by pro-inflammatory, pro-apoptotic and barrier disruptive intracellular signaling, and it is unclear how APC can exert a protective activity through the cleavage of PAR-1 when thrombin is also present in the same environment. Interestingly, in endothelial cell cultures, PAR-1 cleavage by thrombin results in anti-inflammatory and barrier protective signaling provided occupation of EPCR by the PC gla-domain, raising the possibility that the beneficial effects of rh-APC might be recapitulated in vivo by administration of h-PC zymogen to patients with severe sepsis. Recent reports of h-PC infusion in animal models of sepsis support this hypothesis.
Collapse
Affiliation(s)
- Patrizia Della Valle
- Coagulation Service & Thrombosis Research Unit, Scientific Institute San Raffaele, Milano, Italy
| | | | | |
Collapse
|
9
|
Kador K, Mamedov T, Schneider M, Subramanian A. Sequential co-immobilization of thrombomodulin and endothelial protein C receptor on polyurethane: activation of protein C. Acta Biomater 2011; 7:2508-17. [PMID: 21414427 DOI: 10.1016/j.actbio.2011.03.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 03/03/2011] [Accepted: 03/11/2011] [Indexed: 10/18/2022]
Abstract
In an effort to control the surface-mediated activation of thrombin and clot formation, proteins and molecules which mimic the anticoagulant properties of the vascular endothelial lining were immobilized on material surfaces. When immobilized on biomaterial surfaces, thrombomodulin (TM), an endothelial glycoprotein that binds thrombin and activates protein C (PC), was shown to generate activated PC (APC) and delay clot formation. However, TM-mediated activation of PC on biomaterial surfaces was shown to be limited by the transport of PC to the surface, with maximum activation obtained at a surface density of ∼40 fmole TM cm(-2). This work investigates surface immobilized with TM and endothelial protein C receptor (EPCR), a natural cofactor to TM which increases the rate of activation of PC on the native endothelium. A sequential and ordered immobilization of TM and EPCR on polyurethane at an enzymatically relevant distance (<10 nm) resulted in higher amounts of APC compared with surfaces with immobilized TM or with TM and EPCR immobilized randomly and at TM surface densities (1400 fmole cm(-2)) which were previously shown to be transport limited. Ordered TM and EPCR samples also showed increased time to clot formation in experiments with platelet-poor plasma, as measured by thromboelastography. Surfaces immobilized with TM and its natural cofactor EPCR at an enzymatically relevant distance are able to overcome transport limitations, increasing anticoagulant activation and time to clot formation.
Collapse
|
10
|
Cao C, Gao Y, Li Y, Antalis TM, Castellino FJ, Zhang L. The efficacy of activated protein C in murine endotoxemia is dependent on integrin CD11b. J Clin Invest 2010; 120:1971-80. [PMID: 20458145 PMCID: PMC2877939 DOI: 10.1172/jci40380] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Accepted: 03/17/2010] [Indexed: 12/16/2022] Open
Abstract
Activated protein C (APC), the only FDA-approved biotherapeutic drug for sepsis, possesses anticoagulant, antiinflammatory, and barrier-protective activities. However, the mechanisms underlying its anti-inflammatory functions are not well defined. Here, we report that the antiinflammatory activity of APC on macrophages is dependent on integrin CD11b/CD18, but not on endothelial protein C receptor (EPCR). We showed that CD11b/CD18 bound APC within specialized membrane microdomains/lipid rafts and facilitated APC cleavage and activation of protease-activated receptor-1 (PAR1), leading to enhanced production of sphingosine-1-phosphate (S1P) and suppression of the proinflammatory response of activated macrophages. Deletion of the gamma-carboxyglutamic acid domain of APC, a region critical for its anticoagulant activity and EPCR-dependent barrier protection, had no effect on its antiinflammatory function. Genetic inactivation of CD11b, PAR1, or sphingosine kinase-1, but not EPCR, abolished the ability of APC to suppress the macrophage inflammatory response in vitro. Using an LPS-induced mouse model of lethal endotoxemia, we showed that APC administration reduced the mortality of wild-type mice, but not CD11b-deficient mice. These data establish what we believe to be a novel mechanism underlying the antiinflammatory activity of APC in the setting of endotoxemia and provide clear evidence that the antiinflammatory function of APC is distinct from its barrier-protective function and anticoagulant activities.
Collapse
Affiliation(s)
- Chunzhang Cao
- Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Yamei Gao
- Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Yang Li
- Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Toni M. Antalis
- Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Francis J. Castellino
- Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Li Zhang
- Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| |
Collapse
|
11
|
Sen P, Sahoo S, Pendurthi UR, Rao LVM. Zinc modulates the interaction of protein C and activated protein C with endothelial cell protein C receptor. J Biol Chem 2010; 285:20410-20. [PMID: 20413590 DOI: 10.1074/jbc.m110.111575] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Zinc is an essential trace element for human nutrition and is critical to the structure, stability, and function of many proteins. Zinc ions were shown to enhance activation of the intrinsic pathway of coagulation but down-regulate the extrinsic pathway of coagulation. The protein C pathway plays a key role in blood coagulation and inflammation. At present there is no information on whether zinc modulates the protein C pathway. In the present study we found that Zn(2+) enhanced the binding of protein C/activated protein C (APC) to endothelial cell protein C receptor (EPCR) on endothelial cells. Binding kinetics revealed that Zn(2+) increased the binding affinities of protein C/APC to EPCR. Equilibrium dialysis with (65)Zn(2+) revealed that Zn(2+) bound to the Gla domain as well as sites outside of the Gla domain of protein C/APC. Intrinsic fluorescence measurements suggested that Zn(2+) binding induces conformational changes in protein C/APC. Zn(2+) binding to APC inhibited the amidolytic activity of APC, but the inhibition was reversed by Ca(2+). Zn(2+) increased the rate of APC generation on endothelial cells in the presence of physiological concentrations of Ca(2+) but did not further enhance increased APC generation obtained in the presence of physiological concentrations of Mg(2+) with Ca(2+). Zn(2+) had no effect on the anticoagulant activity of APC. Zn(2+) enhanced APC-mediated activation of protease activated receptor 1 and p44/42 MAPK. Overall, our data show that Zn(2+) binds to protein C/APC, which results in conformational changes in protein C/APC that favor their binding to EPCR.
Collapse
Affiliation(s)
- Prosenjit Sen
- Center for Biomedical Research, The University of Texas Health Science Center at Tyler, Tyler, Texas 75708, USA
| | | | | | | |
Collapse
|
12
|
The protein C pathway in tissue inflammation and injury: pathogenic role and therapeutic implications. Blood 2009; 115:1121-30. [PMID: 20018912 DOI: 10.1182/blood-2009-09-201616] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Inflammation and coagulation are closely linked interdependent processes. Under physiologic conditions, the tissue microcirculation functions in anticoagulant and anti-inflammatory fashions. However, when inflammation occurs, coagulation is also set in motion and actively participates in enhancing inflammation. Recently, novel and unexpected roles of hemostasis in the humoral and cellular components of innate immunity have been described. In particular, the protein C system, besides its well-recognized role in anticoagulation, plays a crucial role in inflammation. Indeed, the protein C system is now emerging as a novel participant in the pathogenesis of acute and chronic inflammatory diseases, such as sepsis, asthma, inflammatory bowel disease, atherosclerosis, and lung and heart inflammation, and may emerge as unexpected therapeutic targets for intervention.
Collapse
|
13
|
|
14
|
Rezaie AR, Yang L. Mutagenesis studies toward understanding the mechanism of the cofactor function of thrombomodulin. Biophys Chem 2008; 117:255-61. [PMID: 15970373 DOI: 10.1016/j.bpc.2005.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 06/07/2005] [Accepted: 06/08/2005] [Indexed: 11/23/2022]
Abstract
Thrombomodulin (TM) is as essential cofactor in protein C activation by thrombin. To investigate the cofactor effect of TM on the P3-P3' binding specificity of thrombin, we prepared a Gla-domainless protein C (GDPC) and an antithrombin (AT) mutant in which the P3-P3' residues of both molecules were replaced with the corresponding residues of the factor Xa cleavage site in prethrombin-2. TM is known to interact with GDPC, but not AT in the complex. Thrombin did not react with either mutant in the absence of a cofactor. While the thrombin-TM complex also did not react with the AT mutant, it activated the GDPC mutant with a normal k(cat), but an approximately 4-fold impaired K(m) value. Further studies revealed that the active-site directed inhibitor p-aminobenzamidine acts as a competitive inhibitor of both wild-type and GDPC mutant in reaction with the thrombin-TM complex. These results suggest that the interaction of the P3-P3' residues of GDPC with the active-site pocket of the thrombin-TM complex makes a dominant contribution to the binding specificity of the reaction. Moreover, the observation that the GDPC mutant, but not the AT mutant, functions as an effective substrate for the thrombin-TM complex suggests that GDPC interaction with the thrombin-TM complex may be associated with the alteration of the conformation of the P3-P3' residues of the substrate.
Collapse
Affiliation(s)
- Alireza R Rezaie
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1402 S. Grand Blvd. Saint Louis, MO 63104, USA.
| | | |
Collapse
|
15
|
Structural identification of the pathway of long-range communication in an allosteric enzyme. Proc Natl Acad Sci U S A 2008; 105:1832-7. [PMID: 18250335 DOI: 10.1073/pnas.0710894105] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Allostery is a common mechanism of regulation of enzyme activity and specificity, and its signatures are readily identified from functional studies. For many allosteric systems, structural evidence exists of long-range communication among protein domains, but rarely has this communication been traced to a detailed pathway. The thrombin mutant D102N is stabilized in a self-inhibited conformation where access to the active site is occluded by a collapse of the entire 215-219 beta-strand. Binding of a fragment of the protease activated receptor PAR1 to exosite I, 30-A away from the active site region, causes a large conformational change that corrects the position of the 215-219 beta-strand and restores access to the active site. The crystal structure of the thrombin-PAR1 complex, solved at 2.2-A resolution, reveals the details of this long-range allosteric communication in terms of a network of polar interactions.
Collapse
|
16
|
Abstract
Thrombin is a Na+-activated, allosteric serine protease that plays opposing functional roles in blood coagulation. Binding of Na+ is the major driving force behind the procoagulant, prothrombotic and signaling functions of the enzyme, but is dispensable for cleavage of the anticoagulant protein C. The anticoagulant function of thrombin is under the allosteric control of the cofactor thrombomodulin. Much has been learned on the mechanism of Na+ binding and recognition of natural substrates by thrombin. Recent structural advances have shed light on the remarkable molecular plasticity of this enzyme and the molecular underpinnings of thrombin allostery mediated by binding to exosite I and the Na+ site. This review summarizes our current understanding of the molecular basis of thrombin function and allosteric regulation. The basic information emerging from recent structural, mutagenesis and kinetic investigation of this important enzyme is that thrombin exists in three forms, E*, E and E:Na+, that interconvert under the influence of ligand binding to distinct domains. The transition between the Na+ -free slow from E and the Na+ -bound fast form E:Na+ involves the structure of the enzyme as a whole, and so does the interconversion between the two Na+ -free forms E* and E. E* is most likely an inactive form of thrombin, unable to interact with Na + and substrate. The complexity of thrombin function and regulation has gained this enzyme pre-eminence as the prototypic allosteric serine protease. Thrombin is now looked upon as a model system for the quantitative analysis of biologically important enzymes.
Collapse
Affiliation(s)
- Enrico Di Cera
- Department of Biochemistry and Molecular Biophysics, Washington University Medical School, St. Louis, MO 63110, United States.
| |
Collapse
|
17
|
Kastrup CJ, Shen F, Runyon MK, Ismagilov RF. Characterization of the threshold response of initiation of blood clotting to stimulus patch size. Biophys J 2007; 93:2969-77. [PMID: 17586576 PMCID: PMC1989713 DOI: 10.1529/biophysj.107.109009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
This article demonstrates that the threshold response of initiation of blood clotting to the size of a patch of stimulus is a robust phenomenon under a wide range of conditions and follows a simple scaling relationship based on the Damköhler number. Human blood and plasma were exposed to surfaces patterned with patches presenting clotting stimuli using microfluidics. Perturbations of the complex network of hemostasis, including temperature, variations in the concentration of stimulus (tissue factor), and the absence or inhibition of individual components of the network (factor IIa, factor V, factor VIII, and thrombomodulin), did not affect the existence of this response. A scaling relationship between the threshold patch size and the timescale of reaction for clotting was supported in numerical simulations, a simple chemical model system, and experiments with human blood plasma. These results may be useful for understanding the spatiotemporal dynamics of other autocatalytic systems and emphasize the relevance of clustering of proteins and lipids in the regulation of signaling processes.
Collapse
Affiliation(s)
- Christian J Kastrup
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois, USA
| | | | | | | |
Collapse
|
18
|
Ermakova EA, Panteleev MA, Shnol EE. Blood coagulation and propagation of autowaves in flow. PATHOPHYSIOLOGY OF HAEMOSTASIS AND THROMBOSIS 2006; 34:135-42. [PMID: 16432314 DOI: 10.1159/000089933] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This study analyses the effect of flow and boundary reactions on spatial propagation of waves of blood coagulation. A simple model of coagulation in plasma consisting of three differential reaction-diffusion equations was used for numerical simulations. The vessel was simulated as a two-dimensional channel of constant width, and the anticoagulant influence of thrombomodulin present on the undamaged vessel wall was taken into account. The results of the simulations showed that this inhibition could stop the coagulation process in the absence of flow in narrow channels. For the used mathematical model of coagulation this was the case if the width was below 0.2 mm. In wider vessels, the process could be stopped by the rapid blood flow. The required flow rate increased with the increase of the damage region size. For example, in a 0.5-mm wide channel with 1-mm long damage region, the propagation of coagulation may be terminated at the flow rate of more than 20 mm/min.
Collapse
Affiliation(s)
- Elena A Ermakova
- Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow
| | | | | |
Collapse
|
19
|
Yang L, Manithody C, Rezaie AR. Activation of protein C by the thrombin-thrombomodulin complex: cooperative roles of Arg-35 of thrombin and Arg-67 of protein C. Proc Natl Acad Sci U S A 2006; 103:879-84. [PMID: 16418283 PMCID: PMC1347983 DOI: 10.1073/pnas.0507700103] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The binding of Ca(2+) to the 70-80 loop of protein C inhibits protein C activation by thrombin in the absence of thrombomodulin (TM), but the metal ion is required for activation in the presence of TM. Structural data suggests that the 70-80 loop is located between two antiparallel beta strands comprised of residues 64-69 and 81-91 on the protease domain of protein C. To test the hypothesis that a salt-bridge/hydrogen bond interaction between Arg-67 of the former strand and Asp-82 of the latter strand modulates the unique Ca(2+)-binding properties of protein C, we engineered a disulfide bond between the two strands by substituting both Arg-67 and Asp-82 with Cys residues. The activation of this mutant was enhanced 40- to 50-fold independent of TM and Ca(2+). Furthermore, the Arg-67 to Ala mutant of protein C was activated in the absence of TM by the Arg-35 to Glu mutant of thrombin with the same efficiency as wild-type protein C by wild-type thrombin-TM complex. These results suggest that TM functions by alleviating the Ca(2+)-dependent inhibitory interactions of Arg-67 of protein C and Arg-35 of thrombin.
Collapse
Affiliation(s)
- Likui Yang
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | | | | |
Collapse
|
20
|
Xu H, Bush LA, Pineda AO, Caccia S, Di Cera E. Thrombomodulin changes the molecular surface of interaction and the rate of complex formation between thrombin and protein C. J Biol Chem 2004; 280:7956-61. [PMID: 15582990 DOI: 10.1074/jbc.m412869200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interaction of thrombin with protein C triggers a key down-regulatory process of the coagulation cascade. Using a panel of 77 Ala mutants, we have mapped the epitope of thrombin recognizing protein C in the absence or presence of the cofactor thrombomodulin. Residues around the Na(+) site (Thr-172, Lys-224, Tyr-225, and Gly-226), the aryl binding site (Tyr-60a), the primary specificity pocket (Asp-189), and the oxyanion hole (Gly-193) hold most of the favorable contributions to protein C recognition by thrombin, whereas a patch of residues in the 30-loop (Arg-35 and Pro-37) and 60-loop (Phe-60h) regions produces unfavorable contributions to binding. The shape of the epitope changes drastically in the presence of thrombomodulin. The unfavorable contributions to binding disappear and the number of residues promoting the thrombin-protein C interaction is reduced to Tyr-60a and Asp-189. Kinetic studies of protein C activation as a function of temperature reveal that thrombomodulin increases >1,000-fold the rate of diffusion of protein C into the thrombin active site and lowers the activation barrier for this process by 4 kcal/mol. We propose that the mechanism of thrombomodulin action is to kinetically facilitate the productive encounter of thrombin and protein C and to allosterically change the conformation of the activation peptide of protein C for optimal presentation to the thrombin active site.
Collapse
Affiliation(s)
- Hong Xu
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | |
Collapse
|
21
|
Yang L, Prasad S, Di Cera E, Rezaie AR. The conformation of the activation peptide of protein C is influenced by Ca2+ and Na+ binding. J Biol Chem 2004; 279:38519-24. [PMID: 15254039 DOI: 10.1074/jbc.m407304200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have suggested that the conformation of the activation peptide of protein C is influenced by the binding of Ca(2+). To provide direct evidence for the linkage between Ca(2+) binding and the conformation of the activation peptide, we have constructed a protein C mutant in the gamma-carboxyglutamic acid-domainless form in which the P1 Arg(169) of the activation peptide is replaced with the fluorescence reporter Trp. Upon binding of Ca(2+), the intrinsic fluorescence of the mutant decreases approximately 30%, as opposed to only 5% for the wild-type, indicating that Trp(169) is directly influenced by the divalent cation. The K(d) of Ca(2+) binding for the mutant protein C was impaired approximately 4-fold compared with wild-type. Interestingly, the conformation of the activation peptide was also found to be sensitive to the binding of Na(+), and the affinity for Na(+) binding increased approximately 5-fold in the presence of Ca(2+). These findings suggest that Ca(2+) changes the conformation of the activation peptide of protein C and that protein C is also capable of binding Na(+), although with a weaker affinity compared with the mature protease. The mutant protein C can no longer be activated by thrombin but remarkably it can be activated efficiently by chymotrypsin and by the thrombin mutant D189S. Activation of the mutant protein C by chymotrypsin proceeds at a rate comparable to the activation of wild-type protein C by the thrombin-thrombomodulin complex.
Collapse
Affiliation(s)
- Likui Yang
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104, USA
| | | | | | | |
Collapse
|
22
|
Rezaie AR, Yang L. Thrombomodulin allosterically modulates the activity of the anticoagulant thrombin. Proc Natl Acad Sci U S A 2003; 100:12051-6. [PMID: 14523228 PMCID: PMC218711 DOI: 10.1073/pnas.2135346100] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Exosite 1 of thrombin consists of a cluster of basic residues (Arg-35, Lys-36, Arg-67, Lys-70, Arg-73, Arg-75, and Arg-77 in chymotrypsinogen numbering) that play key roles in the function of thrombin. Structural data suggest that the side chain of Arg-35 projects toward the active site pocket of thrombin, but all other residues are poised to interact with thrombomodulin (TM). To study the role of these residues in TM-mediated protein C (PC) activation by thrombin, a charge reversal mutagenesis approach was used to replace these residues with a Glu in separate constructs. The catalytic properties of the mutants toward PC were analyzed in both the absence and presence of TM and Ca2+. It was discovered that, with the exception of the Arg-67 and Lys-70 mutants, all other mutants activated PC with similar maximum rate constants in the presence of a saturating concentration of TM and Ca2+, although their affinity for interaction with TM was markedly impaired. The catalytic properties of the Arg-35 mutant were changed so that PC activation by the mutant no longer required Ca2+ in the presence of TM, but, instead, it was accelerated by EDTA. Moreover, the activity of this mutant toward PC was improved approximately 25-fold independent of TM. These results suggest that Arg-35 is responsible for the Ca2+ dependence of PC activation by the thrombin-TM complex and that a function for TM in the activation complex is the allosteric alleviation of the inhibitory interaction of Arg-35 with the substrate.
Collapse
Affiliation(s)
- Alireza R Rezaie
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, MO 63104, USA.
| | | |
Collapse
|
23
|
Yang L, Rezaie AR. The fourth epidermal growth factor-like domain of thrombomodulin interacts with the basic exosite of protein C. J Biol Chem 2003; 278:10484-90. [PMID: 12529320 DOI: 10.1074/jbc.m211797200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thrombomodulin (TM) functions as a cofactor to enhance the rate of protein C activation by thrombin approximately 1000-fold. The molecular mechanism by which TM improves the catalytic efficiency of thrombin toward protein C is not known. Molecular modeling of the protein C activation based on the crystal structure of thrombin in complex with the epidermal growth factor-like domains 4, 5, and 6 of TM (TM456) predicts that the binding of TM56 to exosite 1 of thrombin positions TM4 so that a negatively charged region on this domain juxtaposes a positively charged region of protein C. It has been hypothesized that electrostatic interactions between these oppositely charged residues of TM4 and protein C facilitate a proper docking of the substrate into the catalytic pocket of thrombin. To test this hypothesis, we have constructed several mutants of TM456 and protein C in which charges of the putative interacting residues on both TM4 (Asp/Glu) and protein C (Lys/Arg) have been reversed. Results of TM-dependent protein C activation studies by such a compensatory mutagenesis approach support the molecular model that TM4 interacts with the basic exosite of protein C.
Collapse
Affiliation(s)
- Likui Yang
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, Missouri 63104, USA
| | | |
Collapse
|
24
|
Schmidt AE, Padmanabhan K, Underwood MC, Bode W, Mather T, Bajaj SP. Thermodynamic linkage between the S1 site, the Na+ site, and the Ca2+ site in the protease domain of human activated protein C (APC). Sodium ion in the APC crystal structure is coordinated to four carbonyl groups from two separate loops. J Biol Chem 2002; 277:28987-95. [PMID: 12029084 DOI: 10.1074/jbc.m201892200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The serine protease domain of activated protein C (APC) contains a Na+ and a Ca2+ site. However, the number and identity of the APC residues that coordinate to Na+ is not precisely known. Further, the functional link between the Na+ and the Ca2+ site is insufficiently defined, and their linkage to the substrate S1 site has not been studied. Here, we systematically investigate the functional significance of these two cation sites and their thermodynamic links to the S1 site. Kinetic data reveal that Na+ binds to the substrate-occupied APC with K(d) values of approximately 24 mm in the absence and approximately 6 mm in the presence of Ca2+. Sodium-occupied APC has approximately 100-fold increased catalytic efficiency ( approximately 4-fold decrease in K(m) and approximately 25-fold increase in k(cat)) in hydrolyzing S-2288 (H-d-Ile-Pro-Arg-p-nitroanilide) and Ca2+ further increases this k(cat) slightly ( approximately 1.2-fold). Ca2+ binds to the protease domain of APC with K(d) values of approximately 438 microm in the absence and approximately 105 microm in the presence of Na+. Ca2+ binding to the protease domain of APC does not affect K(m) but increases the k(cat) approximately 10-fold, and Na+ further increases this k(cat) approximately 3-fold and decreases the K(m) value approximately 3.7-fold. In agreement with the K(m) data, sodium-occupied APC has approximately 4-fold increased affinity in binding to p-aminobenzamidine (S1 probe). Crystallographically, the Ca2+ site in APC is similar to that in trypsin, and the Na+ site is similar to that in factor Xa but not thrombin. Collectively, the Na+ site is thermodynamically linked to the S1 site as well as to the protease domain Ca2+ site, whereas the Ca2+ site is only linked to the Na+ site. The significance of these findings is that under physiologic conditions, most of the APC will exist in Na2+-APC-Ca2+ form, which has 110-fold increased proteolytic activity.
Collapse
Affiliation(s)
- Amy E Schmidt
- Department of Pharmacological & Physiological Sciences, Saint Louis University Health Sciences Center, St. Louis, Missouri 63110, USA
| | | | | | | | | | | |
Collapse
|
25
|
Hassouna H, Quinn C. Proteolysis of protein C in pooled normal plasma and purified protein C by activated protein C (APC). Biophys Chem 2002; 95:109-24. [PMID: 11897150 DOI: 10.1016/s0301-4622(01)00267-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Protein C is a vitamin-K dependent zymogen of the anti-coagulant serine protease activated protein C (APC). In this paper, we report four lines of evidence that APC can activate protein C in pooled normal plasma, and purified protein C. First, the addition of APC to protein C-deficient plasma supplemented with protein C produces a prolongation of the clotting time of plasma that is proportional to the amount of protein C. This behavior was observed with APC from the Chromogenix APC resistance kit (Dia Pharm, Franklin, OH, USA) and from APC derived from the thrombin activation of human protein C (Enzyme Research Laboratories, South Bend, IN, USA). Secondly, using immunoblotting after gel electrophoresis, the disappearance of epitopes for monoclonal antibodies that recognize protein C but not APC indicates a time course for the activation by APC of protein C in pooled normal plasma and protein C purified from plasma. Thirdly, the same time course for the disappearance of protein C specific epitope can be followed using ELISA. Finally, protein C can be activated by APC as indicated by the increase in APC specific synthetic substrate Tryp-Arg-Arg-p nitroaniline hydrolysis. Kinetic data indicate a value of 4.7+/-0.4 mM(-1) s(-1) for the activation of protein C by APC under physiological conditions and in the presence of calcium. These observations document that APC must function not only in the inactivation of activated factors V and VIII, but also in the activation of protein C. This additional action of APC may be important to consider more broadly because of APC in the treatment of sepsis.
Collapse
Affiliation(s)
- Houria Hassouna
- Department of Medicine, Michigan State University, B-239 Clinical Center, East Lansing, MI 48824-1313, USA.
| | | |
Collapse
|
26
|
Abstract
The protein C anticoagulant pathway converts the coagulation signal generated by thrombin into an anticoagulant response through the activation of protein C by the thrombin-thrombomodulin (TM) complex. The activated protein C (APC) thus formed interacts with protein S to inactivate two critical coagulation cofactors, factors Va and VIIIa, thereby dampening further thrombin generation. The proposed mechanisms by which TM switches the specificity of thrombin include conformational changes in thrombin, blocking access of normal substrates to thrombin and providing a binding site for protein C. The function of protein S appears to be to alter the cleavage site preferences of APC in factor Va, probably by changing the distance of the active site of APC relative to the membrane surface. The clinical relevance of this pathway is now established through the identification of deficient individuals with severe thrombotic complications and through the analysis of families with partial deficiencies in these components and an increased thrombotic tendency. One possible reason that even partial deficiencies are a thrombotic risk is that the function of the pathway can be down-regulated by inflammatory mediators. For instance, clinical studies have shown that the extent to which protein C levels decrease in patients with septic shock is predictive of a negative outcome. Initial clinical studies suggest that supplementation with protein C may be useful in the treatment of acute inflammatory diseases such as sepsis.
Collapse
Affiliation(s)
- C T Esmon
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
| |
Collapse
|
27
|
Xu J, Esmon NL, Esmon CT. Reconstitution of the human endothelial cell protein C receptor with thrombomodulin in phosphatidylcholine vesicles enhances protein C activation. J Biol Chem 1999; 274:6704-10. [PMID: 10037768 DOI: 10.1074/jbc.274.10.6704] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Blocking protein C binding to the endothelial cell protein C receptor (EPCR) on the endothelium is known to reduce protein C activation rates. Now we isolate human EPCR and thrombomodulin (TM) and reconstitute them into phosphatidylcholine vesicles. The EPCR increases protein C activation rates in a concentration-dependent fashion that does not saturate at 14 EPCR molecules/TM. Without EPCR, the protein C concentration dependence fits a single class of sites (Km = 2.17 +/- 0.13 microM). With EPCR, two classes of sites are apparent (Km = 20 +/- 15 nM and Km = 3.2 +/- 1.7 microM). Increasing the EPCR concentration at a constant TM concentration increases the percentage of high affinity sites. Holding the TM:EPCR ratio constant while decreasing the density of these proteins results in a decrease in the EPCR enhancement of protein C activation, suggesting that there is little affinity of the EPCR for TM. Negatively charged phospholipids also enhance protein C activation. EPCR acceleration of protein C activation is blocked by anti-EPCR antibodies, but not by annexin V, whereas the reverse is true with negatively charged phospholipids. Human umbilical cord endothelium expresses approximately 7 times more EPCR than TM. Anti-EPCR antibody reduces protein C activation rates 7-fold over these cells, whereas annexin V is ineffective, indicating that EPCR rather than negatively charged phospholipid provide the surface for protein C activation. EPCR expression varies dramatically among vascular beds. The present results indicate that the EPCR concentration will determine the effectiveness of the protein C activation complex.
Collapse
Affiliation(s)
- J Xu
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | | | | |
Collapse
|
28
|
Ehrlich HJ, Bang NU. Protein C: Physiologie, Biochemie und Molekularbiologie. Hamostaseologie 1999. [DOI: 10.1007/978-3-662-07673-6_39] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
|
29
|
Vincenot A, Pittet JL, Aiach M, Gaussem P. A monoclonal antibody recognizing the activation domain of protein C in its calcium-free conformation. FEBS Lett 1998; 432:94-7. [PMID: 9710258 DOI: 10.1016/s0014-5793(98)00802-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A monoclonal antibody (mAb) binding to protein C (PC) heavy chain but not to activated PC was found to inhibit PC activation by free thrombin, suggesting that epitope involved the activation site. Using a set of overlapping synthetic peptides, we confirmed that this mAb recognizes the sequence encompassing the thrombin cleavage site (165QVDPRLI(171)). Surprisingly, epitope was only accessible in the absence of calcium, half-maximal inhibition of mAb binding occurring at 100 microM Ca2+. Thus, our antibody provides direct evidence that conformation and/or accessibility of the activation site differ between the apo and Ca2+-stabilized conformers of PC.
Collapse
Affiliation(s)
- A Vincenot
- INSERM U 428, Faculté de Pharmacie, Paris, France
| | | | | | | |
Collapse
|
30
|
Abstract
AbstractA recent study indicated that negatively charged substances such as heparin and dextran sulfate accelerate thrombin activation of coagulation factor XI by a template mechanism. Because the serine proteinase of the natural anticoagulant pathway, activated protein C, can bind heparin, it was reasonable to think that these compounds may also bind protein C (PC) and accelerate its activation by thrombin or other heparin binding plasma serine proteinases by a similar mechanism. To test this, PC activation by thrombin and factor Xa (fXa) was studied in the presence of these polysaccharides. With thrombin in the absence of thrombomodulin (TM), these polysaccharides markedly reduced the Km for PC and Gla-domainless PC (GDPC) activation in the presence of Ca2+. With TM containing chondroitin sulfate, heparin did not influence PC activation by thrombin, but with TM lacking chondroitin sulfate, the characteristic high-affinity PC interaction at low Ca2+ (∼50 to 100 μmol/L) was largely eliminated by heparin. In EDTA, heparin enhanced thrombin activation of GDPC by reducing the Km, but it inhibited PC activation by increasing the Km. PC activation in EDTA was insensitive to the presence of heparin if the exosite 2 mutant, R93,97,101A thrombin, was used for activation. These results suggest that, when the Gla-domain of PC is not fully stabilized by Ca2+, it interacts with the anion binding exosite 2 of thrombin and that heparin binding to this site prevents this interaction. Additional studies indicated that, in the presence of phospholipid vesicles, heparin and dextran sulfate dramatically accelerate PC activation by fXa by also reducing the Km. Interestingly, on phospholipids containing 40% phosphatidylethanolamine, the activation rate of near physiological PC concentrations (∼80 nmol/L) by fXa in the presence of dextran sulfate was nearly comparable to that observed by the thrombin-TM complex. The biochemical and potential therapeutical ramifications of these findings are discussed.
Collapse
|
31
|
Abstract
A recent study indicated that negatively charged substances such as heparin and dextran sulfate accelerate thrombin activation of coagulation factor XI by a template mechanism. Because the serine proteinase of the natural anticoagulant pathway, activated protein C, can bind heparin, it was reasonable to think that these compounds may also bind protein C (PC) and accelerate its activation by thrombin or other heparin binding plasma serine proteinases by a similar mechanism. To test this, PC activation by thrombin and factor Xa (fXa) was studied in the presence of these polysaccharides. With thrombin in the absence of thrombomodulin (TM), these polysaccharides markedly reduced the Km for PC and Gla-domainless PC (GDPC) activation in the presence of Ca2+. With TM containing chondroitin sulfate, heparin did not influence PC activation by thrombin, but with TM lacking chondroitin sulfate, the characteristic high-affinity PC interaction at low Ca2+ (∼50 to 100 μmol/L) was largely eliminated by heparin. In EDTA, heparin enhanced thrombin activation of GDPC by reducing the Km, but it inhibited PC activation by increasing the Km. PC activation in EDTA was insensitive to the presence of heparin if the exosite 2 mutant, R93,97,101A thrombin, was used for activation. These results suggest that, when the Gla-domain of PC is not fully stabilized by Ca2+, it interacts with the anion binding exosite 2 of thrombin and that heparin binding to this site prevents this interaction. Additional studies indicated that, in the presence of phospholipid vesicles, heparin and dextran sulfate dramatically accelerate PC activation by fXa by also reducing the Km. Interestingly, on phospholipids containing 40% phosphatidylethanolamine, the activation rate of near physiological PC concentrations (∼80 nmol/L) by fXa in the presence of dextran sulfate was nearly comparable to that observed by the thrombin-TM complex. The biochemical and potential therapeutical ramifications of these findings are discussed.
Collapse
|
32
|
Nishioka J, Ning M, Hayashi T, Suzuki K. Protein C inhibitor secreted from activated platelets efficiently inhibits activated protein C on phosphatidylethanolamine of platelet membrane and microvesicles. J Biol Chem 1998; 273:11281-7. [PMID: 9556620 DOI: 10.1074/jbc.273.18.11281] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein C inhibitor (PCI) was detected in human platelets (2.9 ng/10(9) cells) and megakaryocytic cells (1.5 ng/10(6) cells). PCI mRNA was also detected in both platelets and megakaryocytic cells using nested polymerase chain reaction. PCI was found to be located in the alpha-granules of resting platelets. Approximately 30% of the total amount of PCI in platelets was released after stimulation with ADP, collagen, adrenalin, thrombin, or thrombin receptor-activating peptide. Secreted PCI was detected on the surface of activated platelets and phospholipid microvesicles. PCI secreted from thrombin receptor-activating peptide-stimulated platelets inhibited activated protein C (APC) efficiently. PCI significantly inhibited APC in the presence of phospholipid vesicles prepared using rabbit brain cephalin (RBC) or a mixture of 40% phosphatidylethanolamine (PE), 20% phosphatidylserine (PS), and 40% phosphatidylcholine (PC) with a second order rate constant of 1.0 x 10(6) M-1.min-1. Of these phospholipids, PE was critical for this inhibition. The dissociation constants of the binding of APC or PCI to solid phase phospholipids showed that APC binds more preferably to PE than to RBC or PS, and PCI to PE or RBC than to PS or PC. PCI binding to solid phase phospholipids depended on the presence of PE. RBC- or PE-bound PCI inhibited APC significantly but only weakly the gamma-carboxyglutamic acid domainless APC. The gamma-carboxyglutamic acid fragment of protein C suppressed the PCI-mediated inhibition of APC on solid phase RBC or PE. Most of the APC.PCI complex formed on solid phase RBC or PE was released into the soluble phase. These findings suggest that PCI secreted from activated platelets binds preferably to PE of platelet membrane and microvesicles and that it inhibits phospholipid-bound APC efficiently.
Collapse
Affiliation(s)
- J Nishioka
- Department of Molecular Pathobiology, Mie University School of Medicine, Tsu-city, Mie 514, Japan
| | | | | | | |
Collapse
|
33
|
Abstract
Thrombin undergoes allosteric modulation by thrombomodulin (TM) that results in a shift in macromolecular specificity, blocking fibrinogen clotting while enhancing protein C activation. The TM enhancement of protein C activation involves both an 8-fold decrease in Km and a 200-fold increase in kcat. Although TM-mediated conformational changes in thrombin have been detected by many techniques, the nature of these changes remains obscure. Access to the active center of thrombin is relatively restricted due to the presence of a large insertion loop at residue 60 (chymotrypsin numbering) that has been implicated in modeling studies as being responsible for poor inhibition by BPTI. Thrombin and the E192Q mutant, which binds BPTI much more tightly than thrombin, are both inhibited very slowly by BPTI. TM increases the rate of thrombin or thrombin E192Q inhibition by BPTI approximately 10-fold. When analyzed as slow tight binding inhibition, the TM effect on thrombin E192Q inhibition by BPTI is primarily on the first, reversible step in the reaction. Structural studies of the thrombin E192Q-BPTI complex have previously shown that the 60 loop lies over the BPTI, a position which requires 8 A movement at the apex of the 60 loop, and that BPTI is found in the same canonical orientation as in the trypsin complex. It follows that TM enhancement of the initial interaction of thrombin results in a conformation that favors interactions with BPTI, probably involving motion of the 60 loop.
Collapse
Affiliation(s)
- A R Rezaie
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Department of Pathology, University of Oklahoma Health Sciences Center, and Howard Hughes Medical Institute, Oklahoma City, Oklahoma 73104, USA
| | | | | |
Collapse
|
34
|
|
35
|
Mac Hale JL, Nathan N, D'Ambra M. Intrinsic Anticoagulation: Protein C, Protein S, and Thrombomodulin. Semin Cardiothorac Vasc Anesth 1997. [DOI: 10.1177/108925329700100405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The protein C anticoagulant system provides important control over the blood coagulation cascade. Any alteration in this pathway, either hereditary, iatrogenic, or otherwise, may interfere with normal coagulation. In this review, current concepts and understanding of surface-dependent hemostatis are reviewed, effects of deficiencies in the intrinsic anticoagulant system are described, and potentially useful therapeutic strategies are proposed. The importance of protein C, protein S, and thrombomodulin in patients undergoing cardiac surgery is specifically addressed. Further work is required before complex interactions of individual components of the intrinsic anticoagulation pathway are fully understood.
Collapse
Affiliation(s)
- John L. Mac Hale
- Department of Cardiac Anaesthesia, Massachusetts General Hospital, Boston, MA
| | - Nadia Nathan
- Department of Cardiac Anaesthesia, Massachusetts General Hospital, Boston, MA
| | - Michael D'Ambra
- Department of Cardiac Anaesthesia, Massachusetts General Hospital, Boston, MA
| |
Collapse
|
36
|
Regan LM, Mollica JS, Rezaie AR, Esmon CT. The interaction between the endothelial cell protein C receptor and protein C is dictated by the gamma-carboxyglutamic acid domain of protein C. J Biol Chem 1997; 272:26279-84. [PMID: 9334197 DOI: 10.1074/jbc.272.42.26279] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The endothelial cell protein C receptor (EPCR) binds to both protein C and activated protein C (APC) with similar affinity. Removal of the Gla domain of protein C results in the loss of most of the binding affinity. This observation is compatible with at least two models: 1) the Gla domain of protein C interacts with phospholipid on cell surfaces to stabilize interaction with EPCR or 2) the Gla domain of protein C makes specific protein-protein interactions with EPCR. The latter model predicts that chimeric proteins containing the protein C Gla domain should interact with EPCR. To test this, we constructed a prothrombin chimera in which the Gla domain and aromatic stack of prothrombin were replaced with the corresponding region of protein C. The 125I-labeled chimera (Kd = 176 nM) and 125I-APC (Kd = 65 nM) both bound specifically to 293 cells stably transfected with EPCR, but both bound poorly to sham-transfected cells. The chimera also blocked APC binding to EPCR-transfected cells in a dose-dependent fashion (Ki approximately 139 nM) similarly to protein C (Ki approximately 75 nM). Chimera binding to EPCR-transfected cells was blocked by soluble EPCR, demonstrating direct protein-protein interaction between the chimera and EPCR. Consistent with this conclusion, the isolated Gla domain of protein C blocked APC binding to EPCR-transfected cells (IC50 = 2 microM). No inhibition was observed with the isolated prothrombin Gla domain. A protein C chimera with the prothrombin Gla domain and aromatic stack failed to bind to EPCR detectably. These data suggest that the Gla domain of protein C is responsible for much of the binding energy and specificity of the protein C-EPCR interaction.
Collapse
Affiliation(s)
- L M Regan
- Howard Hughes Medical Institute, Oklahoma City, Oklahoma 73104, USA
| | | | | | | |
Collapse
|
37
|
Regan LM, Stearns-Kurosawa DJ, Kurosawa S, Mollica J, Fukudome K, Esmon CT. The endothelial cell protein C receptor. Inhibition of activated protein C anticoagulant function without modulation of reaction with proteinase inhibitors. J Biol Chem 1996; 271:17499-503. [PMID: 8663474 DOI: 10.1074/jbc.271.29.17499] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A soluble form of the endothelial cell protein C receptor (EPCR) was analyzed for the ability to modulate the functional properties of protein C and activated protein C (APC). In a plasma clotting system initiated with factor Xa, EPCR blocked the anticoagulant activity of APC in a dose-dependent fashion. EPCR had no influence on clotting in the absence of APC. Consistent with the plasma results, EPCR slowed the proteolytic inactivation of factor Va by slowing both of the key proteolytic cleavages in the heavy chain of factor Va. EPCR did not prevent protein C activation by the soluble thrombin-thrombomodulin complex, did not alter the inactivation of APC by alpha1-antitrypsin or protein C inhibitor, and did not influence the kinetics of peptide paranitroanilide substrate cleavage significantly. We conclude that EPCR binds to an exosite on APC that selectively modulates the enzyme specificity in a manner reminiscent of the influence of thrombomodulin on thrombin.
Collapse
Affiliation(s)
- L M Regan
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, 73104, USA
| | | | | | | | | | | |
Collapse
|
38
|
Callas DD, Fareed J. Comparative studies on the antithrombin potency of various thrombin inhibitors, as determined by using an amidolytic method. Thromb Res 1996; 83:97-102. [PMID: 8837308 DOI: 10.1016/0049-3848(96)00107-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- D D Callas
- Department of Pharmacology, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153, USA
| | | |
Collapse
|
39
|
Rezaie AR, Esmon CT. Tryptophans 231 and 234 in protein C report the Ca(2+)-dependent conformational change required for activation by the thrombin-thrombomodulin complex. Biochemistry 1995; 34:12221-6. [PMID: 7547963 DOI: 10.1021/bi00038a016] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Human protein C circulates as both single- and two-chain zymogens. Activation by the physiological activation complex, thrombin-thrombomodulin, generates the anticoagulant enzyme, activated protein C. Ca2+ binding to the protease domain of protein C is accompanied by 5.5 +/- 0.2% quenching of intrinsic fluorescence that correlates with the conformational change required for the rapid activation by the thrombin-thrombomodulin complex. To map which Trp residues report this Ca2+ binding, candidate Trp residues at positions 84, 115, 145, 205, 231, and 234 were changed individually to Phe within a protein C deletion mutant lacking the Gla domain (GDPC). Of these, the Trp to Phe mutation at position 231 (W231F) eliminated the Ca(2+)-induced fluorescence quenching, and the Trp 234 to Phe mutation (W234F) increased the maximum quenching in protein C to 9.4 +/- 0.4%. Upon Ca2+ binding, the fluorescence emission intensity of the W231F mutant was increased 3.4% +/- 0.6%. The Kd for this site (84 +/- 20 microM) was similar to that of GDPC (Kd = 39 +/- 4 microM). To compare the properties of single- and two-chain protein C, we replaced the Lys156-Arg157 dipeptide cleavage site in protein C with Thr and Gln to form GDPCKR/TQ. GDPCKR/TQ and the two-chain form of protein C were activated at the same rate with the thrombin-thrombomodulin complex, they exhibited similar Ca2+ dependence for both activation and fluorescence quenching, and these enzymes had the same chromogenic activity. In contrast to the zymogen form, activated human Gla-domainless protein C did not undergo a Ca(2+)-induced fluorescence change. These results indicate that the environment of Trp 231 and 234 within the Ca2+ binding loop of the protein C zymogen are perturbed by Ca2+ binding to the zymogen.
Collapse
Affiliation(s)
- A R Rezaie
- Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | | |
Collapse
|
40
|
Medved LV, Orthner CL, Lubon H, Lee TK, Drohan WN, Ingham KC. Thermal stability and domain-domain interactions in natural and recombinant protein C. J Biol Chem 1995; 270:13652-9. [PMID: 7775416 DOI: 10.1074/jbc.270.23.13652] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Scanning microcalorimetry and spectrofluorimetry were applied to a study of the thermal stability and interaction of the modules within natural human protein C (PC) and recombinant protein C (rPC), a potential therapeutic anticoagulant expressed in transgenic pigs. Upon heating in the presence of 2 mM EDTA, pH 8.5, each protein exhibited a similar heat absorption peak with a Tm of approximately 62 degrees C corresponding to the melting of the serine protease (SP) module. Deconvolution of this peak indicated that the SP module consists of two domains that unfold independently. At pH below 3.8, a second peak appeared at extremely high temperature corresponding to the unfolding of the two interacting epidermal growth factor-like (EGF) domains. This second peak occurred at a temperature about 20 degrees C lower in rPC than in PC indicating that the EGF domains in the recombinant protein are less stable. The isolated 6-kDa gamma-carboxyglutamic acid-rich (Gla) fragment as well as a 25-kDa Gla-(EGF)2 fragment both exhibited a sigmoidal fluorescence-detected denaturation transition in the same temperature region as the SP domains, but only in the presence of Ca2+. In 2 mM Ca2+, the first heat absorption peak in both intact proteins became biphasic, indicating Ca(2+)-induced structural changes. By contrast, Ca2+ had very little effect on the melting of Gla-domain-less protein C. This indicates that not Ca2+ itself but the Ca(2+)-loaded Gla domain is responsible for conformational changes in the SP domain of the parent protein. Detailed analysis of the shape of the endotherms obtained in Ca2+ and EDTA suggests that Ca2+ induces compact structure in the Gla domain which appears to interact strongly with the SP domain(s) of protein C.
Collapse
Affiliation(s)
- L V Medved
- J. Holland Laboratory, American Red Cross, Rockville, Maryland 20855, USA
| | | | | | | | | | | |
Collapse
|
41
|
Lu D, Bovill EG, Long GL. Molecular mechanism for familial protein C deficiency and thrombosis in protein CVermont (Glu20–>Ala and Val34–>Met). J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)62009-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
42
|
Platelet factor 4 stimulates thrombomodulin protein C-activating cofactor activity. A structure-function analysis. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47284-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
43
|
Christiansen WT, Castellino FJ. Properties of recombinant chimeric human protein C and activated protein C containing the gamma-carboxyglutamic acid and trailing helical stack domains of protein C replaced by those of human coagulation factor IX. Biochemistry 1994; 33:5901-11. [PMID: 8180219 DOI: 10.1021/bi00185a030] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The properties of a recombinant (r) chimeric human protein C (PC) containing replacement of its gamma-carboxyglutamic acid (Gla) and helical stack (HS) domains by those of human coagulation factor IX (fIX) have been examined. Titration with Ca2+ of the divalent cation-induced intrinsic fluorescence quenching of this chimera (r-GDIX/PC) allowed determination of the [Ca2+], of 1.8 mM, required to produce this alteration in 50% of the protein molecules. These values were 0.41 and 0.61 mM for wtr-PC and fIX, respectively. The chimera did not react with a Ca(2+)-dependent, Gla domain-directed conformational monoclonal antibody (MAb) to r-PC but did interact with a similar MAb (H5B7) to fIX. The [Ca2+] required to induced H5B7 binding to 50% of the r-GDIX/PC molecules was 6.6 mM, while this same value for fIX was a nearly identical 7.2 mM. The [Ca2+] needed for binding of 50% of r-GDIX/PC to acidic phospholipid (PL) vesicles was 0.58 mM, while that for wtr-PC and fIX were 1.2 and 0.55 mM, respectively. The [protein] required for 50% binding of r-GDIX/PC to PL at 20 mM Ca2+ was 0.29 microM. These same values for r-PC and fIX were 0.38 and 1.8 microM, respectively. The Ca(2+)-mediated inhibition of the thrombin-catalyzed activation of r-GDIX/PC was characterized by a Ki of 118 microM, a value similar to that of 125 microM obtained for this same inhibition of wtr-PC activation. The thrombin-catalyzed activation of both r-GDIX/PC and wtr-PC was stimulated by soluble r-thrombomodulin. Similar to the case of wtr-PC, Ca2+ initially enhanced and, at higher concentrations, inhibited the activation of r-GDIX/PC. The Km and kcat values for this latter activation at optimal [Ca2+] (100 microM) were 4.1 microM and 2.5 s-1, respectively. These same kinetic constants for activation of wtr-PC were 4.3 microM and 2.9 s-1, respectively. These results show that many of the features needed for functional integrity of the Ca2+-bound Gla/HS domains of PC are also present in those same modules of fIX, a finding that points to a generalized functional role for the Ca2+-induced conformation of the structural unit consisting of the Gla and HS domains. The data also suggest that the Ca2+-bound form of the Gla/HS region is an independently folded unit in PC and perhaps in fIX.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- W T Christiansen
- Department of Chemistry and Biochemistry, University of Notre Dame, Indiana 46556
| | | |
Collapse
|
44
|
Fisher CL, Greengard JS, Griffin JH. Models of the serine protease domain of the human antithrombotic plasma factor activated protein C and its zymogen. Protein Sci 1994; 3:588-99. [PMID: 8003977 PMCID: PMC2142866 DOI: 10.1002/pro.5560030407] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Three-dimensional structural analysis of physiologically important serine proteases is useful in identifying functional features relevant to the expression of their activities and specificities. The human serine protease anticoagulant protein C is currently the object of many genetic site-directed mutagenesis studies. Analyzing relationships between its structure and function and between naturally occurring mutations and their corresponding clinical phenotypes would be greatly assisted by a 3-dimensional structure of the enzyme. To this end, molecular models of the protease domain of protein C have been produced using computational techniques based on known crystal structures of homologous enzymes and on protein C functional information. The resultant models corresponding to different stages along the processing pathway of protein C were analyzed for structural and electrostatic differences arising during the process of protein C maturation and activation. The most satisfactory models included a calcium ion bound to residues homologous to those that ligate calcium in the trypsin structure. Inspection of the surface features of the models allowed identification of residues putatively involved in specific functional interactions. In particular, analysis of the electrostatic potential surface of the model delineated a positively charged region likely to represent a novel substrate recognition exosite. To assist with future mutational studies, binding of an octapeptide representing a protein C cleavage site of its substrate factor Va to the enzyme's active site region was modeled and analyzed.
Collapse
Affiliation(s)
- C L Fisher
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037
| | | | | |
Collapse
|
45
|
Neuenschwander P, Morrissey J. Roles of the membrane-interactive regions of factor VIIa and tissue factor. The factor VIIa Gla domain is dispensable for binding to tissue factor but important for activation of factor X. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37152-1] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
46
|
Rezaie A, Mather T, Sussman F, Esmon C. Mutation of Glu-80–>Lys results in a protein C mutant that no longer requires Ca2+ for rapid activation by the thrombin-thrombomodulin complex. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41841-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
47
|
Yu S, Zhang L, Jhingan A, Christiansen WT, Castellino FJ. Construction, expression, and properties of a recombinant chimeric human protein C with replacement of its growth factor-like domains by those of human coagulation factor IX. Biochemistry 1994; 33:823-31. [PMID: 8292611 DOI: 10.1021/bi00169a025] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The cDNA encoding a chimeric human protein C (PC), in which its epidermal growth factor-(EGF) like regions have been replaced with equivalent structures from human factor IX (fIX), was constructed and the gene product was expressed in human 293 cells. A molecular subpopulation of the recombinant chimeric protein (r-[PC/delta EGF-1,2/delta fIXEGF-1,2]) was purified that contained the full complement (9 residues/mol) of gamma-carboxyglutamic acid (Gla). After conversion by thrombin to its activated form (r-[APC/delta EGF-1,2/delta fIXEGF-1,2]), this latter enzyme was found to possess approximately 10% of the activity of wild-type recombinant APC (wtr-APC) in an APTT assay. In assay systems employing purified components, the activity of the mutant enzyme toward prothrombinase cofactor Va (fVa) and tenase cofactor VIII (fVIII) was approximately 30% and < 10%, respectively, of that of wtr-APC. The chimeric protein displayed full reactivity with a Ca(2+)-dependent monoclonal antibody to the Gla domain of PC, yielding a C50 for Ca2+ that was very similar to that obtained with wtr-PC (ca. 3.7 mM). Titrations of the dependency on Ca2+ of the intrinsic fluorescence of r-[PC/delta EGF-1,2/delta fIXEGF-1,2] allowed calculation of a C50 value of 0.34 mM, again very similar to that of wtr-PC. As with wtr-PC, Ca2+ inhibited the thrombin-catalyzed activation of r-[PC/delta EGF-1,2/delta fIXEGF-1,2] with aKi of 148 microM, as compared to a Ki of 125 microM for wtr-PC. At a saturating level of Ca2+, activation of r-[PC/delta EGF-1,2/delta fIXEGF-1,2/] by the thrombin/thrombomodulin (thrombin/TM) complex occurred at approximately 70% of the rate of that of wtr-PC.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- S Yu
- Department of Chemistry and Biochemistry, University of Notre Dame, Indiana 46556
| | | | | | | | | |
Collapse
|
48
|
Le Bonniec B, Guinto E, MacGillivray R, Stone S, Esmon C. The role of thrombin's Tyr-Pro-Pro-Trp motif in the interaction with fibrinogen, thrombomodulin, protein C, antithrombin III, and the Kunitz inhibitors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(17)46734-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
49
|
Mesters RM, Heeb MJ, Griffin JH. Interactions and inhibition of blood coagulation factor Va involving residues 311-325 of activated protein C. Protein Sci 1993; 2:1482-9. [PMID: 8401232 PMCID: PMC2142455 DOI: 10.1002/pro.5560020912] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Activated protein C (APC) exerts its physiologic anticoagulant role by proteolytic inactivation of the blood coagulation cofactors Va and VIIIa. The synthetic peptide-(311-325) (KRNRTFVLNFIKIPV), derived from the heavy chain sequence of APC, potently inhibited APC anticoagulant activity in activated partial thromboplastin time (APTT) and Xa-1-stage coagulation assays in normal and in protein S-depleted plasma with 50% inhibition at 13 microM peptide. In a system using purified clotting factors, peptide-(311-325) inhibited APC-catalyzed inactivation of factor Va in the presence or absence of phospholipids with 50% inhibition at 6 microM peptide. However, peptide-(311-325) had no effect on APC amidolytic activity or on the reaction of APC with the serpin, recombinant [Arg358]alpha 1-antitrypsin. Peptide-(311-325) surprisingly inhibited factor Xa clotting activity in normal plasma, and in a purified system it inhibited prothrombinase activity in the presence but not in the absence of factor Va with 50% inhibition at 8 microM peptide. The peptide had no significant effect on factor Xa or thrombin amidolytic activity and no effect on the clotting of purified fibrinogen by thrombin, suggesting it does not directly inhibit these enzymes. Factor Va bound in a dose-dependent manner to immobilized peptide-(311-325). Peptide-(311-315) inhibited the binding of factor Va to immobilized APC or factor Xa.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- R M Mesters
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037
| | | | | |
Collapse
|
50
|
Takahashi M, Kimura M, Kurosawa-Ohsawa K, Iwaki A, Tanaka S, Matsuishi T. Epitope mapping and characterization of monoclonal antibodies to human protein C. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1161:113-23. [PMID: 7679287 DOI: 10.1016/0167-4838(93)90204-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Six monoclonal antibodies specific to human protein C were characterized. Epitopes of these antibodies were determined on isolated proteolytic peptides of protein C by immunological methods. Three antibodies bound light chain of protein C: PC01 bound the gamma-carboxyglutamic acid domain calcium-dependently, while PC02 and PC08 bound the first epidermal growth factor-like domain in calcium-dependent and independent manners, respectively. The other three antibodies bound the heavy chain of protein C: PC13 bound activation peptide, PC04 recognized the activation site and PC09 bound the region close to a disulfide bond connecting light and heavy chains. Activation of protein C with thrombin-thrombomodulin complex was inhibited strongly by PC04 and moderately by PC08, PC09 and PC13. PC04 and PC13 may directly block the activation site. On the other hand, epitopes of PC08 and PC09 may be involved in interaction between protein C and thrombin-thrombomodulin complex, or locate close to activation site on the tertiary structure of protein C. Anticlotting activity of protein C was inhibited strongly by PC01 and moderately by PC02, PC08 and PC09, while amidolytic activity was inhibited only by PC09. The epitopes described here may constitute part of protein-C-specific sites, which are important for the function of protein C.
Collapse
Affiliation(s)
- M Takahashi
- Pharma Research Laboratories, Hoechst Japan Ltd., Saitama
| | | | | | | | | | | |
Collapse
|