TY  - JOUR
A1  - Navarro, Stefano
A1  - Stegner, David
A1  - Nieswandt, Bernhard
A1  - Heemskerk, Johan W. M.
A1  - Kuijpers, Marijke J. E.
T1  - Temporal roles of platelet and coagulation pathways in collagen- and tissue factor-induced thrombus formation
JF  - International Journal of Molecular Sciences
N2  - In hemostasis and thrombosis, the complex process of thrombus formation involves different molecular pathways of platelet and coagulation activation. These pathways are considered as operating together at the same time, but this has not been investigated. The objective of our study was to elucidate the time-dependency of key pathways of thrombus and clot formation, initiated by collagen and tissue factor surfaces, where coagulation is triggered via the extrinsic route. Therefore, we adapted a microfluidics whole-blood assay with the Maastricht flow chamber to acutely block molecular pathways by pharmacological intervention at desired time points. Application of the technique revealed crucial roles of glycoprotein VI (GPVI)-induced platelet signaling via Syk kinase as well as factor VIIa-induced thrombin generation, which were confined to the first minutes of thrombus buildup. A novel anti-GPVI Fab EMF-1 was used for this purpose. In addition, platelet activation with the protease-activating receptors 1/4 (PAR1/4) and integrin αIIbβ3 appeared to be prolongedly active and extended to later stages of thrombus and clot formation. This work thereby revealed a more persistent contribution of thrombin receptor-induced platelet activation than of collagen receptor-induced platelet activation to the thrombotic process.
KW  - coagulation
KW  - fibrin
KW  - glycoprotein VI
KW  - platelet receptors
KW  - spatiotemporal thrombus
KW  - thrombin
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284219
SN  - 1422-0067
VL  - 23
IS  - 1
ER  - 
TY  - JOUR
A1  - Nieswandt, Bernhard
A1  - Morowski, Martina
A1  - Brachs, Sebastian
A1  - Mielenz, Dirk
A1  - Dütting, Sebastian
T1  - The Adaptor Protein Swiprosin-1/EFhd2 Is Dispensable for Platelet Function in Mice
N2  - Background

Platelets are anuclear cell fragments derived from bone marrow megakaryocytes that safeguard vascular integrity, but may also cause pathological vessel occlusion. Reorganizations of the platelet cytoskeleton and agonist-induced intracellular Ca2+-mobilization are crucial for platelet hemostatic function. EF-hand domain containing 2 (EFhd2, Swiprosin-1) is a Ca2+-binding cytoskeletal adaptor protein involved in actin remodeling in different cell types, but its function in platelets is unknown.

Objective

Based on the described functions of EFhd2 in immune cells, we tested the hypothesis that EFhd2 is a crucial adaptor protein for platelet function acting as a regulator of Ca2+-mobilization and cytoskeletal rearrangements.

Methods and Results

We generated EFhd2-deficient mice and analyzed their platelets in vitro and in vivo. Efhd2-/- mice displayed normal platelet count and size, exhibited an unaltered in vivo life span and showed normal Ca2+-mobilization and activation/aggregation responses to classic agonists. Interestingly, upon stimulation of the immunoreceptor tyrosine-based activation motif-coupled receptor glycoprotein (GP) VI, Efhd2-/- platelets showed a slightly increased coagulant activity. Furthermore, absence of EFhd2 had no significant impact on integrin-mediated clot retraction, actomyosin rearrangements and spreading of activated platelets on fibrinogen. In vivo EFhd2-deficiency resulted in unaltered hemostatic function and unaffected arterial thrombus formation.

Conclusion

These results show that EFhd2 is not essential for platelet function in mice indicating that other cytoskeletal adaptors may functionally compensate its loss.
KW  - adaptor protein Swiprosin-1/EFhd2
KW  - platelets
KW  - platelet activation
KW  - platelet aggregation
KW  - cytoskeleton
KW  - thrombin
KW  - blood
KW  - actins
KW  - collagens
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-113316
ER  -