TY  - JOUR
A1  - Dütting, Sebastian
A1  - Gaits-Iacovoni, Frederique
A1  - Stegner, David
A1  - Popp, Michael
A1  - Antkowiak, Adrien
A1  - van Eeuwijk, Judith M.M.
A1  - Nurden, Paquita
A1  - Stritt, Simon
A1  - Heib, Tobias
A1  - Aurbach, Katja
A1  - Angay, Oguzhan
A1  - Cherpokova, Deya
A1  - Heinz, Niels
A1  - Baig, Ayesha A.
A1  - Gorelashvili, Maximilian G.
A1  - Gerner, Frank
A1  - Heinze, Katrin G.
A1  - Ware, Jerry
A1  - Krohne, Georg
A1  - Ruggeri, Zaverio M.
A1  - Nurden, Alan T.
A1  - Schulze, Harald
A1  - Modlich, Ute
A1  - Pleines, Irina
A1  - Brakebusch, Cord
A1  - Nieswandt, Bernhard
T1  - A Cdc42/RhoA regulatory circuit downstream of glycoprotein Ib guides transendothelial platelet biogenesis
JF  - Nature Communications
N2  - Blood platelets are produced by large bone marrow (BM) precursor cells, megakaryocytes (MKs), which extend cytoplasmic protrusions (proplatelets) into BM sinusoids. The molecular cues that control MK polarization towards sinusoids and limit transendothelial crossing to proplatelets remain unknown. Here, we show that the small GTPases Cdc42 and RhoA act as a regulatory circuit downstream of the MK-specific mechanoreceptor GPIb to coordinate polarized transendothelial platelet biogenesis. Functional deficiency of either GPIb or Cdc42 impairs transendothelial proplatelet formation. In the absence of RhoA, increased Cdc42 activity and MK hyperpolarization triggers GPIb-dependent transmigration of entire MKs into BM sinusoids. These findings position Cdc42 (go-signal) and RhoA (stop-signal) at the centre of a molecular checkpoint downstream of GPIb that controls transendothelial platelet biogenesis. Our results may open new avenues for the treatment of platelet production disorders and help to explain the thrombocytopenia in patients with Bernard–Soulier syndrome, a bleeding disorder caused by defects in GPIb-IX-V.
KW  - megakaryocytes
KW  - blood platelets
KW  - regulatory circuit downstream
KW  - glycoprotein Ib
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170797
VL  - 8
IS  - 15838
ER  - 
TY  - JOUR
A1  - Popp, Michael
A1  - Thielman, Ina
A1  - Nieswandt, Bernhard
A1  - Stegner, David
T1  - Normal Platelet Integrin Function in Mice Lacking Hydrogen Peroxide-Induced Clone-5 (Hic-5)
JF  - PLoS One
N2  - Integrin αIIbβ3 plays a central role in the adhesion and aggregation of platelets and thus is essential for hemostasis and thrombosis. Integrin activation requires the transmission of a signal from the small cytoplasmic tails of the α or β subunit to the large extracellular domains resulting in conformational changes of the extracellular domains to enable ligand binding. Hydrogen peroxide-inducible clone-5 (Hic-5), a member of the paxillin family, serves as a focal adhesion adaptor protein associated with αIIbβ3 at its cytoplasmic tails. Previous studies suggested Hic-5 as a novel regulator of integrin αIIbβ3 activation and platelet aggregation in mice. To assess this in more detail, we generated Hic-5-null mice and analyzed activation and aggregation of their platelets in vitro and in vivo. Surprisingly, lack of Hic-5 had no detectable effect on platelet integrin activation and function in vitro and in vivo under all tested conditions. These results indicate that Hic-5 is dispensable for integrin αIIbβ3 activation and consequently for arterial thrombosis and hemostasis in mice.
KW  - platelet activation
KW  - fibrinogen
KW  - integrins
KW  - platelets
KW  - thrombin
KW  - flow cytometry
KW  - platelet aggregation
KW  - blood
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125724
VL  - 10
IS  - 7
ER  -