Recombinant blood-coagulation proteases

Details Recombinant blood-coagulation proteases Recombinant blood-coagulation proteases

1999-04-12

2001-08-21

Prouty, Rebecca E. (Department: 1652)

Chemistry: molecular biology and microbiology

Enzyme , proenzyme; compositions thereof; process for...

Hydrolase

C435S004000, C435S023000, C435S024000, C435S183000, C435S218000, C435S219000, C435S252300, C435S320100, C435S226000, C530S380000, C530S381000, C530S383000, C530S384000

Reexamination Certificate

active

06277618

ABSTRACT:

The invention concerns truncated post-translationally non-modif ied blood plasma protease variants of the factor IX gene family (FVII, FIX, FX and protein C) composed of an EFG2 domain, activation peptide (AP) and catalytic domain (CD) as well as the process for their production by expression in a host cell, preferably in a microorganism, renaturation in vitro and subsequent activation with a suitable protease.
The blood plasma protease variants according to the invention are suitable for finding (screening) inhibitors, for the production of co-crystals composed of a protease variant and inhibitor for the purpose of X-ray structure analysis and drug modelling and as diagnostic test: components in activator tests.
Blood plasma proteases play a role in blood coagulation, wound closure by fibrin formation as well as in fibrinolysis i.e. clot dissolution in wound healing. After an injury the injury signal is amplified by the sequential activation (specific proteolysis) of inactive proenzymes to form active enzymes which initiates blood coagulation and ensures a rapid wound closure. Blood coagulation can be initiated by two paths, the intrinsic path in which all protein components are present in the blood and the extrinsic path in which a membrane protein, the so-called tissue factor plays a critical role.
The molecular mechanism of blood homeostasis (blood coagulation, fibrinolysis and the regulation of this equilibrium) and the components that are involved in this are comprehensively described in several review articles (Furie, B. and Furie, B. C., Cell 53 (1988) 505-518; Davie, E. W. et al., Biochem. 30 (1991) 10363-10379; Bergmeyer, H. U. (ed.): Methods of Enzymatic Analysis, Vol. V, chapter 3, 3rd ed., Academic Press, New York (1983)).
The proteases of the blood coagulation cascade are very complex proteins. As a rule they can only be isolated in a complicated manner from the natural raw material source, the blood plasma, in a limited amount, with varying quality, homogeneity and purity (Van Dam-Mieras, M. C. E. et al., In: Bergmeyer, H. U. (ed.), Methods of Enzymatic Analysis, Vol. V, 3rd ed., page 365-394, Academic Press, New York (1983)). They play an important role in the regulation of blood homeostasis which is the equilibrium between blood coagulation, clot formation and dissolution. This well-regulated system can become unbalanced by genetic defects such as haemophilia A (defective factor VIII) and haemophilia B (defective factor IX), as well as by acute disorders such as e.g. in cardiac infarction, embolism and stroke.
There is therefore a need for substances which can influence the system of blood coagulation and fibrinolysis according to the medical requirements. For example recombinantly produced factor VIII or factor IX or recently also factor VII are used to treat haemophilia A and B. tPA (tissue type plasminogen activator) and streptokinase (bacterial protease) are used for example for clot lysis e.g. after cardiac infarction. In addition to complex proteins, substances such as hirudin (peptide composed of 65 amino acids, specific thrombin inhibitor), heparin (heteroglycan, thrombin inhibition/cofactor) and vitamin K antagonists (inhibitors of &ggr;-carboxylation; Glu residues of the Gla domain) are also used to inhibit blood coagulation. However, the available substances are often still very expensive (protein factors) and not ideal with regard to their medical application (side effects) so that there is a need for medicaments which can be used to specifically modulate blood coagulation and clot lysis.
The search for new modulators (activators, inhibitors) of blood coagulation, fibrinolysis and homeostasis can for example be carried out by screening substance libraries and subsequently improving an identified lead structure by drug modelling. For this it is necessary that the key protein(s) [target(s)] are available in an adequate amount and quality for screening and for crystallization investigations (e.g. improvement of the lead structure by the specific prediction of changes based on the 3D structure of the protein component and lead structure).
The activated serine proteases thrombin, FVIIa, FIXa, FXa, FXIa, FXIIa, kallikrein (blood coagulation), tPA, urokinase, plasmin (fibrinolysis) and activated protein C (regulatory anticoagulant) and inactive precursors (zymogens) thereof are for example attractive targets within homeostasis.
The isolation of inactive serine proteases (zymogens) from blood plasma and the subsequent activation by proteolysis is difficult, time-consuming, expensive and often does not yield the amount and quality that is for example desired for crystallization experiments. For example the plasma concentration of the inactive protease zymogens FX, FIX and FVII is only 10, 5 and 0.5 mg/l respectively (Furie, B. and Furie B. C., Cell 53 (1988) 505-518). Moreover the protease preparations isolated from the plasma and activated in vitro are often very heterogeneous and unstable. Furthermore non-uniform post-translational modifications (e.g. carbohydrate groups) impede the crystallization experiments.
Blood plasma proteases are complex glycoproteins that belong to the serine protease family. They are synthesized in the liver as inactive proenzymes (zymogens), secreted into the blood and are activated when required by specific proteolysis i.e. by cleavage of one or two peptide bonds. They are structurally very similar with regard to the arrangement of their protein domains and their composition (Furie, B. and Furie, B. C., Cell 53 (1988) 505-518).
According to Furie B. and Furie, B. C. the proteases of the factor IX family (factor VII, IX, X and protein C) are composed of
a propeptide,
a GLA domain,
an aromatic amino acid stack domain,
two EGF domains (EGF1 and EGF2),
a zymogen activation domain (activation peptide, AP) and
a catalytic protease domain (CD).
Furthermore the blood plasma proteases are post-translationally modified during secretion:
11-12 disulfide bridges
N- and/or O-glycosylation (GLA domain and activation peptide)
Bharadwaj, D. et al., J. Biol. Chem. 270 (1995) 6537-6542
Medved, L. V. et al., J. Biol. Chem. 270 (1995) 13652-13659
cleavage of the propeptide
&ggr;-carboxylation of Glu residues (GLA domain)
&bgr;-hydroxylation of an Asp residue (EGF domains)
cleavage of the zymogen region (partially)
After activation of the zymogens (zymogenic form of the protein) by specific cleavage of one or two peptide bonds (activation peptide), the enzymatically active proteases are composed of two chains which, in accordance with their molecular weight, are referred to as the heavy and light chain. In the factor IX protease family the two chains are held together by an intermolecular disulfide bridge between the EGF2 domain and the protease domain. The zymogen-enzyme transformation (activation) leads to conformation changes within the protease domain. This enables an essential salt bridge necessary for the protease activity to form between the N-terminal amino acid of the prc)tease domain and an Asp residue within the protease domain. The N-terminal region is very critical for this subgroup of serine proteases and should not be modified. Only then is it possible for the typical active site of the serine proteases to form with the catalytic triad composed of Ser, Asp and His (Blow, D. M.: Acc. Chem. Res. 9 (1976) 145-152; Polgar, L.: In: Mechanisms of protease action. Boca Raton, Fla., CRC Press, chapter 3 (1989).
Blood plasma proteases can be produced in a classical manner by isolating the inactive zymogens from the blood and subsequently activating them or they can be produced recombinantly by expressing the corresponding cDNA in a suitable mammalian cell line or in yeast.
Production of Blood Plasma Proteases by Expression/secretion of the Zymogens or Active Proteases by Means of Eukaryotic Host/vector Systems
FVII: Hagen, F. S. et al., EPS 0200421; Pedersen, A. H. et al., Biochem. 28 (1989) 9391-9336; FIX: Lin, S.-W. et al., J. Biol. Chem. 265 (1990) 144-150; FX: Wolf, D. L. et al., J. Biol. Chem. 266 (1991) 13726-13730; Protein

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