Fibronectin unfolded by adherent but not suspended platelets: An in vitro explanation for its dual role in haemostasis.
Fibronectin (FN), a dimeric adhesive glycoprotein, which is present both in plasma and the extracellular matrix can interact with platelets and thus contribute to platelet adhesion and aggregation. It has been shown that FN can decrease platelet aggregation but enhance platelet adhesion, suggesting a dual role of FN in haemostasis. The prevalent function(s) of FN may be determined by its fibril form. To explore the suggested dual role of this adhesive protein for haemostasis in further detail, we now tested for any differences of adherent and suspended platelets with regard to their effect to unfold and assemble FN upon interaction. Platelet aggregation and adhesion assays were performed using washed platelets in the presence of exogenous FN. Addition of plasma FN reduced platelet aggregation in response to collagen or PMA by 50% or 25% but enhanced platelet adhesion onto immobilized collagen, as compared to control experiments. Analyses by fluorescence resonance energy transfer (FRET) demonstrated that adherent platelets but not suspended platelets were capable of unfolding FN during 3h incubation. Fluorescence microscopy and deoxycholate (DOC) solubility assays demonstrated that FN fibrils formed only on the surfaces of adherent platelets. In addition, platelets adherent onto FN revealed a significantly higher activity of specific Src phosphorylation (pY418) than platelets in suspension. These data suggest (1) that the function of FN in haemostasis is prevalent to its assembly, unfolding and subsequent fibril formation on the surface of adherent platelets and (2) that outside-in signaling contributes to the interaction of platelets and FN.
Department of Experimental and Clinical Haemostasis, Haemotherapy, and Transfusion Medicine, Heinrich Heine University Medical Center, Dusseldorf, Germany; NRW Research School Biostruct, Heinrich Heine University, Dusseldorf, Germany; Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City, Vietnam. Electronic address: hckhon@hcmiu.edu.vn.
Khon
K
Huynh
Department of Experimental and Clinical Haemostasis, Haemotherapy, and Transfusion Medicine, Heinrich Heine University Medical Center, Dusseldorf, Germany; Biological Medical Research Center, Heinrich Heine University, Dusseldorf, Germany.
Marianna
M
Gyenes
Institute of Microbiology, Heinrich Heine University, Dusseldorf, Germany.
Cornelis P
CP
Hollenberg
Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City, Vietnam.
Thi-Hiep
TH
Nguyen
Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City, Vietnam.
Toi
T
Van Vo
Department of Experimental and Clinical Haemostasis, Haemotherapy, and Transfusion Medicine, Heinrich Heine University Medical Center, Dusseldorf, Germany; Biological Medical Research Center, Heinrich Heine University, Dusseldorf, Germany; NRW Research School Biostruct, Heinrich Heine University, Dusseldorf, Germany.
Volker R
VR
Stoldt
D001792:Blood Platelets / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D006487:Hemostasis; D006801:Humans; D010973:Platelet Adhesiveness / Q000502:physiology*; D010974:Platelet Aggregation / Q000502:physiology*
D005353:Fibronectins
Fibronectin; fibronectin assembly; fibronectin unfolding and fibril formation; platelet adhesion and aggregation