Dataset Information

Molecular mechanisms of antithrombin-heparin regulation of blood clotting proteinases. A paradigm for understanding proteinase regulation by serpin family protein proteinase inhibitors.

ABSTRACT: Serpin family protein proteinase inhibitors regulate the activity of serine and cysteine proteinases by a novel conformational trapping mechanism that may itself be regulated by cofactors to provide a finely-tuned time and location-dependent control of proteinase activity. The serpin, antithrombin, together with its cofactors, heparin and heparan sulfate, perform a critical anticoagulant function by preventing the activation of blood clotting proteinases except when needed at the site of a vascular injury. Here, we review the detailed molecular understanding of this regulatory mechanism that has emerged from numerous X-ray crystal structures of antithrombin and its complexes with heparin and target proteinases together with mutagenesis and functional studies of heparin-antithrombin-proteinase interactions in solution. Like other serpins, antithrombin achieves specificity for its target blood clotting proteinases by presenting recognition determinants in an exposed reactive center loop as well as in exosites outside the loop. Antithrombin reactivity is repressed in the absence of its activator because of unfavorable interactions that diminish the favorable RCL and exosite interactions with proteinases. Binding of a specific heparin or heparan sulfate pentasaccharide to antithrombin induces allosteric activating changes that mitigate the unfavorable interactions and promote template bridging of the serpin and proteinase. Antithrombin has thus evolved a sophisticated means of regulating the activity of blood clotting proteinases in a time and location-dependent manner that exploits the multiple conformational states of the serpin and their differential stabilization by glycosaminoglycan cofactors.

SUBMITTER: Olson ST

PROVIDER: S-EPMC2974786 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Molecular mechanisms of antithrombin-heparin regulation of blood clotting proteinases. A paradigm for understanding proteinase regulation by serpin family protein proteinase inhibitors.

Olson Steven T ST Richard Benjamin B Izaguirre Gonzalo G Schedin-Weiss Sophia S Gettins Peter G W PG

Biochimie 20100602 11

Serpin family protein proteinase inhibitors regulate the activity of serine and cysteine proteinases by a novel conformational trapping mechanism that may itself be regulated by cofactors to provide a finely-tuned time and location-dependent control of proteinase activity. The serpin, antithrombin, together with its cofactors, heparin and heparan sulfate, perform a critical anticoagulant function by preventing the activation of blood clotting proteinases except when needed at the site of a vascu ...[more]

PMID: 20685328

Similar Datasets

Project description:One of the key difficulties in glioma treatment is our limited ability to consistently assess cancer response or progression either by neuroimaging or specific blood biomarkers. An ideal biomarker could be measured through non-invasive methods such as blood-based biomarkers, aiding both early diagnosis and monitoring disease evolution. This is a single-center, case-control, 10-year retrospective, longitudinal study. We evaluated routine coagulation factors in 138 glioma patients (45 Females/93 Males; median [range] age, 56.4 [27-82] years; 64 non-recurrent/74 recurrent) and, for comparison, in 56 relapsing-remitting MS patients (41 Females/15 Males; 40.8 [25-62] years, 35 stable/21 active) and 23 controls (16 Females/7 Males; 41.7 [24-62] years) as well as Neutrophil-to-lymphocyte ratio (NLR) in subgroups of 127 glioma patients, 33 MS patients and 23 healthy controls. Secondly, we assessed whether these indicators could be predictive of overall (OS) and progression-free survival (PFS) in glioma patients. NLR, d-dimer, Antithrombin III and Factor VIII were significantly higher in glioma patients compared to both MS patients and controls (p<0.0001 for all). ROC curves confirmed that either NLR, Antithrombin III or Factor VIII were moderately accurate biomarkers (0.7<AUC<0.9) for glioma patients compared to other two groups whereas d-dimer was a moderately accurate marker for glioma only when compared to controls. In multivariable analysis, NLR ≥ 4.3 (median) (HR 1.53 [95 % CI 1.04-2.26], p=0.03) together with the Karnofsky Performance Status (KPS) ≥ 80 (median) (0.46 [0.31-0.69], p<0.0001) and use of steroids (1.75 [1.19-2.57], p=0.004) resulted independent predictors of OS while only KPS was independently associated with PFS. Our study showed increased levels of either NLR, Antithrombin III, Factor VIII, or d-dimer in glioma patients compared to MS patients and controls, where the first three represented moderately accurate biomarkers for this cancer. Among these markers, only NLR was found to be predictive for OS along with severe disability and steroid therapy.

Project description:The present study deals with the conformation in solution of two heparin octasaccharides containing the pentasaccharide sequence GlcN(NAc,6S)-GlcA-GlcN(NS,3,6S)-IdoA(2S)-GlcN(NS,6S) [AGA*IA; where GlcN(NAc,6S) is N-acetylated, 6-O-sulfated alpha-D-glucosamine, GlcN(NS,3,6S) is N,3,6-O-trisulfated alpha-D-glucosamine and IdoA(2S) is 2-O-sulfated IdoA (alpha-L-iduronic acid)] located at different positions in the heparin chain and focuses on establishing geometries of IdoA residues (IdoA(2S) and IdoA) both inside and outside the AGA*IA sequence. AGA*IA constitutes the active site for AT (antithrombin) and is essential for the expression of high anticoagulant and antithrombotic activities. Analysis of NMR parameters [NOEs (nuclear Overhauser effects), transferred NOEs and coupling constants] for the two octasaccharides indicated that between the 1C4 and 2S0 conformations present in dynamic equilibrium in the free state for the IdoA(2S) residue within AGA*IA, AT selects the 2S0 form, as previously shown [Hricovini, Guerrini, Bisio, Torri, Petitou and Casu (2001) Biochem. J. 359, 265-272]. Notably, the 2S0 conformation is also adopted by the non-sulfated IdoA residue preceding AGA*IA that, in the absence of AT, adopts predominantly the 1C4 form. These results further support the concept that heparin-binding proteins influence the conformational equilibrium of iduronic acid residues that are directly or indirectly involved in binding and select one of their equi-energetic conformations for best fitting in the complex. The complete reversal of an iduronic acid conformation preferred in the free state is also demonstrated for the first time. Preliminary docking studies provided information on the octasaccharide binding location agreeing most closely with the experimental data. These results suggest a possible biological role for the non-sulfated IdoA residue preceding AGA*IA, previously thought not to influence the AT-binding properties of the pentasaccharide. Thus, for each AT binding sequence longer than AGA*IA, the interactions with the protein could differ and give to each heparin fragment a specific biological response.

Dataset Information

Molecular mechanisms of antithrombin-heparin regulation of blood clotting proteinases. A paradigm for understanding proteinase regulation by serpin family protein proteinase inhibitors.

Publications

Molecular mechanisms of antithrombin-heparin regulation of blood clotting proteinases. A paradigm for understanding proteinase regulation by serpin family protein proteinase inhibitors.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets