The interaction of fibulin-1 with fibrinogen. A potential role in hemostasis and thrombosis

• Published in: The Journal of biological chemistry Vol. 270; no. 33; pp. 19458 - 19464
• Main Authors: Tran, H, Tanaka, A, Litvinovich, S V, Medved, L V, Haudenschild, C C, Argraves, W S
• Format: Journal Article
• Language: English
• Published: United States 18.08.1995
• Subjects: Binding Sites; Biopolymers; Calcium-Binding Proteins - blood; Calcium-Binding Proteins - isolation & purification; Calcium-Binding Proteins - physiology; Enzyme-Linked Immunosorbent Assay; Fibrinogen - isolation & purification; Fibrinogen - metabolism; Fibrinogen - physiology; Fluorescence Polarization; Hemostasis; Humans; Protein Binding; Thrombosis - blood
• ISSN: 0021-9258
• DOI: 10.1074/jbc.270.33.19458

The fibulins are an emerging family of extracellular matrix and blood proteins presently having two members designated fibulin-1 and -2. Fibulin-1 is the predominant fibulin in blood, present at a concentration of 30-40 micrograms/ml (approximately 1000-fold higher than fibulin-2). During the course of isolating fibulin-1 from plasma by immunoaffinity chromatography, a 340-kDa polypeptide was consistently found to co-purify. This protein was identified as fibrinogen (Fg) based on its electrophoretic behavior and reactivity with Fg monoclonal antibodies. Radioiodinated fibulin-1 was shown to bind to Fg transferred onto nitrocellulose filters after SDS-polyacrylamide gel electrophoresis. In enzyme-linked immunosorbent assay, fibulin-1 bound to Fg (and fibrin) adsorbed onto microtiter well plastic, and conversely, Fg bound to fibulin-1-coated wells. The binding of Fg to fibulin-1 was also observed in surface plasmon resonance assays, and a dissociation constant (Kd) of 2.9 +/- 1.6 microM was derived. In addition, fluorescence anisotropy experiments demonstrated that the interaction was also able to occur in fluid phase, which suggests that complexes of fibulin-1 and Fg could exist in the blood. To localize the portion of Fg that is responsible for interacting with fibulin-1, proteolytic fragments of Fg were evaluated for their ability to promote fibulin-1 binding. Fragments containing the carboxyl-terminal region of the Bbeta chain (residues 216-468) were able to bind to fibulin-1. In addition, it was found that fibulin-1 was able to incorporate into fibrin clots formed in vitro and was immunologically detected within newly formed fibrin-containing thrombi associated with human atherectomy specimens. The interaction between fibulin-1 and Fg highlights potential new roles for fibulin-1 in hemostasis as well as thrombosis.