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Platelet-activating factor-binding protein in human serum

M Matsumoto, M Miwa

    Advances in Prostaglandin, Thromboxane, and Leukotriene Research
    |January 1, 1985
    PubMed

    Insights

    Researchers discovered a novel protein in human serum, Platelet-Binding Protein (PBP), which binds strongly to Platelet-Activating Factor (PAF). This PBP facilitates PAF-induced platelet aggregation and release from neutrophils.

    Area of Science:

    • Biochemistry
    • Immunology
    • Hematology

    Background:

    • Platelet-Activating Factor (PAF) is a potent lipid mediator involved in inflammation and allergic reactions.
    • The binding and transport mechanisms of PAF in human serum are not fully understood.
    • Albumin is a major serum protein, but its role in PAF binding is less characterized compared to specific binding proteins.

    Purpose of the Study:

    • To identify and characterize proteins in human serum with high Platelet-Activating Factor (PAF)-binding capabilities.
    • To investigate the functional consequences of PAF binding to identified serum proteins.
    • To explore the role of these proteins in PAF release from stimulated immune cells.

    Main Methods:

    • Serum protein isolation and purification.
    • Platelet aggregation assays.
    • Biochemical characterization of protein-ligand interactions (molecular weight, subunit composition).
    • Analysis of PAF release from ionophore-stimulated neutrophils.

    Main Results:

    • A novel protein, Platelet-Binding Protein (PBP), was identified in human serum with significantly higher PAF-binding affinity than albumin.
    • PBP has an estimated molecular weight of 160-180 kDa and appears to be a pentamer of 32 kDa subunits.
    • PAF bound to PBP induced platelet aggregation and was resistant to acetylhydrolase degradation.
    • PBP mediated the release of newly synthesized PAF from neutrophils stimulated with A23187.

    Conclusions:

    • Human serum contains a specific protein (PBP) that avidly binds PAF.
    • PBP plays a role in PAF-mediated platelet activation and modulates PAF release from neutrophils.
    • These findings suggest PBP is a key component in regulating PAF's biological activities.

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