Biomedical subjects

M Hessing

Publications and source records attributed to M Hessing.

26 records · Page 2Linked to original sources

PubMed1990

Identification of different forms of human C4b-binding protein lacking beta-chain and protein S binding ability.

Human C4b-binding protein (C4BP) is a multimeric regulatory component of the complement system that circulates in plasma either as a free protein or in a noncovalent complex with the vitamin K-dependent protein S. The major form of C4BP is composed of seven identical alpha-chains (70 kDa) and one beta-chain (45 kDa). C4BP was purified from human plasma after barium citrate adsorption using anti-C4BP monoclonal antibody affinity chromatography. C4BP-high and low Mr forms were both obtained from the barium citrate precipitate and the supernatant. C4BP-high and low forms from the barium citrate precipitate were separated by sodium dodecylsulfate polyacrylamide slab gel electrophoresis and extracted with Triton X-100. Both forms contained the beta-chain as was demonstrated on sodium dodecylsulfate polyacrylamide slab gel electrophoresis under reduced conditions after silver-staining and with Western-blotting using monoclonal antibodies specific for the beta-chain. The C4BP-high and low forms demonstrated similar protein S binding affinity (KA: 3.18 x 10(8) and 3.21 x 10(8) M-1, respectively) in a C4BP-protein S binding assay and a protein S ligand blot using a peroxidase-conjugated monoclonal anti-protein S antibody. The barium citrate supernatant contained two forms of C4BP-high and one form of C4BP-low. One form of C4BP-high did contain the beta-chain and was capable of protein S binding (KA: 4.35 x 10(8) M-1). The two other forms of C4BP lacked the beta-chain and were unable to bind protein S.

Binding Sites↗

PubMed1990

Importance of the alpha 3-fragment of complement C4 for the binding with C4b-binding protein.

The human regulatory complement component C4b-binding protein (C4BP) is a multimeric plasma protein, which regulates the classical pathway of the complement system. C4BP functions as a cofactor to factor 1 in the degradation of C4b and accelerates the decay rate of the C4b2a complex. Previously, we have demonstrated that monoclonal antibodies (C4-2 and 9) directed against the alpha'-chain of C4b inhibit the binding of C4b to C4BP. In order to identify the structural domain of C4b that binds C4BP, proteolytic fragments of C4 were generated with trypsin and Staphylococcus aureus V8 protease. Sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblotting and amino acid sequence analysis of the proteolytic fragments reactive with the anti-C4 mAb's revealed that the residues Ala738-Arg826 of the alpha 3-fragment of C4b are important for the interaction with C4BP.

Amino Acid Sequence↗

PubMed1990

The binding site of human C4b-binding protein on complement C4 is localized in the alpha'-chain.

C4b-binding protein (C4BP) is a multimeric plasma protein, which regulates the classical pathway of the C system. C4BP functions as a cofactor to factor I in the degradation of C4b and accelerates the decay rate of the C4b2a complex. We now demonstrate that C4b contains a binding site for C4BP, which is localized on the alpha'-chain of C4b. SDS-PAGE of C C4 and C4b both under reducing and nonreducing conditions was followed by a radiolabeled C4BP ligand blotting procedure. It was demonstrated that the C4BP binding site on C4b is localized on the alpha'-chain. In addition, we found C4BP binding to the alpha-chain of C4, which suggests that the binding site for C4BP becomes available after reduction of the C4 molecule. Direct binding of C4BP to the alpha- and alpha'-chains of C4 and C4b was demonstrated in a radio-labeled C4BP binding assay with the reduced and alkylated isolated chains. mAb against the alpha'-chain of C4b were prepared, characterized, and evaluated for their ability to block the binding of 125I-C4BP to C4b. Two mAb specific for the alpha'-chain of C4b were found that completely abolished C4BP binding to intact C4b. Other mAb recognizing both the alpha- and alpha'-chain of C4 and C4b demonstrated only minor inhibitory effect on the binding of C4BP to C4b. In conclusion, we have localized the C4BP binding site on the alpha'-chain of C4b and have demonstrated that this binding can be inhibited by mAb specific for the alpha'-chain.

Antibodies, Monoclonal↗

PubMed1990

The localization of heparin-binding fragments on human C4b-binding protein.

C4b-binding protein (C4BP) is a multimeric plasma protein, which regulates the classical pathway of the C system. C4BP interacts with C C4b on a domain located in a 48-kDa chymotryptic fragment. We now demonstrate that C4BP contains heparin-binding fragments, which are located within the C4b binding domain. We have used an assay using heparin coupled to Sepharose CL-6B to show that 125I-C4BP binds to heparin in a time-dependent, saturable, and reversible manner. Binding could be inhibited by purified 48-kDa fragments and direct binding on the 48-kDa fragments to heparin-Sepharose was demonstrated by SDS-PAGE. mAb against native C4BP and the isolated 160-kDa central core fragment were evaluated for their ability to block the binding of 125I-C4BP to heparin and C4b. The relative efficacy of mAb against intact C4BP in blocking C4BP binding to heparin-Sepharose was similar to that for blocking 125I-C4BP binding to C4b. In addition, heparin blocked the binding of 125I-C4BP to C4b and vice versa. It is therefore likely that the heparin-binding fragments are localized on or close to the C4b-binding site of C4BP.

Antibodies, Monoclonal↗

PubMed1989

Protein S binding in relation to the subunit composition of human C4b-binding protein.

The human regulatory complement component C4b-binding protein (C4BP) circulates in plasma either as a free protein or in a bimolecular complex with the vitamin K-dependent protein S. The major form of C4BP is composed of 7 identical, disulfide-linked 70 kDa subunits (alpha-chains), the arrangement of which gives the C4BP molecule a spider-like appearance. Recently, we identified a unique 45 kDa subunit (beta-chain) in C4BP. We have now isolated a subpopulation of C4BP, which does not bind protein S. This C4BP species, which had a molecular weight slightly lower than that of the predominant form, was found to lack the beta-chain. Another lower molecular weight form of C4BP was also purified. It contained the beta-chain and was efficient in binding protein S. Its subunit composition was judged to comprise six alpha-chains and one beta-chain. These results indicate C4BP in plasma to be heterogeneous at a molecular level vis-a-vis subunit composition and/or protein S binding ability and provide support for the concept that the beta-chain of C4BP contains the single protein S binding site.

Blotting, Western↗

PubMed1989

Risk factors for thrombosis in lupus patients.

Lupus anticoagulant, concentrations of anticardiolipin antibodies, antithrombin III, plasminogen, (free) protein S, protein C, prothrombin, platelet counts, and bleeding times were determined in 74 lupus patients (58 with systemic lupus erythematosus; 16 with lupus-like disease) to establish the presence of risk factors for thrombosis in these patients. Of the variables evaluated, lupus anticoagulant had the strongest association with a history of thrombosis. Both positive anticardiolipin antibody concentrations and the presence of (mild) thrombocytopenia were significantly associated with a history of thrombosis and the presence of lupus anticoagulant. Reduced concentrations of antithrombin III, plasminogen, (free) protein S, and protein C were found in some patients but were not associated with either thrombosis or lupus anticoagulant. Mean concentrations of total protein S were significantly lower in patients with thrombosis than in those without and in patients with lupus anticoagulant than in those without. The antigenic concentration of prothrombin was reduced in 3/74 (4%) lupus patients. These three patients had lupus anticoagulant but no history of thrombosis, which suggests that a low prothrombin concentration protects patients with lupus anticoagulant from the development of thrombosis. A prolonged bleeding time was associated with the presence of lupus anticoagulant but not with a history of thrombosis. Analysis by stepwise logistic regression did not disclose additional risk factors for thrombosis in lupus patients with lupus anticoagulant. Increased antithrombin III concentrations and decreased free protein S concentrations are often found in lupus patients, unrelated to lupus anticoagulant or thrombosis.

Adolescent↗

PubMed1988

Inactivation of human plasma kallikrein and factor XIa by protein C inhibitor.

The inhibition of kallikrein and factor XIa by protein C inhibitor (PCI) was studied. The method of Suzuki et al. [Suzuki, K., Nishioka, J., & Hashimoto, S. (1983) J. Biol. Chem. 258, 163-168] for the purification of PCI was modified in order to avoid the generation of proteolytic activity and subsequent inactivation of PCI. With the use of soybean trypsin inhibitor, an efficient inhibitor of kallikrein and factor XIa, the generation of proteolytic activity was avoided. The kinetics for the inactivation of activated protein C (APC), kallikrein, and factor XIa by PCI were determined. In the absence of heparin, no inactivation of APC was observed, in contrast to kallikrein and factor XIa, which are inhibited with second-order rate constants of (11 +/- 4) X 10(4) and (0.94 +/- 0.07) X 10(4) M-1 s-1, respectively. Addition of heparin potentiated the inhibition of APC [(1.2 +/- 0.2) X 10(4) M-1 s-1] and factor XIa [(9.1 +/- 0.7) X 10(4) M-1 s-1] by PCI, whereas the inhibition of kallikrein by PCI was unchanged [(10 +/- 1) X 10(4) M-1 s-1]. The second-order rate constants for the inhibition of kallikrein or factor XIa by PCI were similar to the second-order rate constants for the inhibition of their isolated light chains by PCI, indicating a minor role for the heavy chains of both molecules in the inactivation reactions. With sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis and immunoblotting, complex formation of APC, kallikrein, and factor XIa with PCI could be demonstrated. APC and kallikrein formed 1:1 molar complexes with PCI.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗

PubMed1988

Identification of monoclonal antibodies that inhibit the function of protein C inhibitor. Evidence for heparin-independent inhibition of activated protein C in plasma.

Monoclonal antibodies specific for protein C inhibitor (PCI) partially blocked the inactivation of activated protein C (APC) in plasma, whereas in a purified system, the PCI activity could be completely blocked. The inactivation of APC in normal and in PCI-depleted plasma was similar in the absence of heparin. The addition of heparin did not change the rate of inactivation of APC in PCI-depleted plasma, whereas in normal plasma a rapid phase of inhibition of APC was followed by a slower phase of inhibition. The slower phase was identical to the rate of inhibition of APC in the absence of heparin. After incubation of normal plasma with a monoclonal antibody specific for PCI that blocked its activity, there was no difference in heparin-dependent or heparin-independent inhibition of APC. These results indicate that in the absence of heparin PCI is unable to inactivate APC in a plasma environment.

Animals↗