Free N-terminal fibronectin 30-kD-domain mediates binding of soluble fibrin to gelfiltered unstimulated thrombocytes.
Gelfiltered unstimulated human platelets neither bound 125-I-fibrinogen nor 125-I-fibrin. Fibrin-binding was, however, stimulated by N-terminal fibronectin 30 kD-and 70 kD-fragments while fibronectin was ineffective. The 30 kD-fragment also stimulated some platelet preparations to bind fibrinogen which, however, was suppressed by minute amounts of the thrombin inhibitor PPACK. PPACK hardly influenced fibrin-binding. Fragment-promoted fibrinogen-binding was also inhibited by a monoclonal antibody recognizing the membrane glycoprotein IIb/IIIa complex known to act as fibrinogen receptor. This antibody failed to influence fragment-stimulated fibrin-binding giving evidence that fibrinogen and fibrin were retained by different receptors. In contrast to 125-I-fibrin its plasmin-derived and 125-I-labelled fragment X was not recognized by the platelets in presence of the fibronectin 30 kD-fragment. Fragment-stimulated binding of 125-I-fibrin showed a lag phase and was completely inhibited by 0.25 mM putrescine as well as by 1 mM EDTA or 0.1 mM N-ethylmaleinimide. Evidently, a cell-attached transamidase was involved in fibrin-binding possibly by forming a ternary complex with fibrin and the fibronectin fragment.
Hörmann
H
H
Max-Planck-Institut für Biochemie, Martinsried bei München German Federal Republic.
Richter
H
H
Jelinić
V
V
D001792:Blood Platelets / Q000378:metabolism*; D002850:Chromatography, Gel; D005337:Fibrin / Q000378:metabolism*; D005353:Fibronectins / Q000502:physiology*; D006801:Humans; D008970:Molecular Weight; D011485:Protein Binding; D011700:Putrescine / Q000494:pharmacology
D005353:Fibronectins; D005337:Fibrin; D011700:Putrescine