ORCID Profile
0000-0002-5802-4748
Current Organisations
INSERM U1255
,
Université de Strasbourg
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Publisher: American Society of Hematology
Date: 06-2006
DOI: 10.1182/BLOOD-2005-10-4244
Abstract: Fibrillar collagens are among the most potent activators of platelets and play an important role in the initiation of thrombosis. The glycoprotein VI (GPVI)/FcRγ-chain complex is a central collagen receptor and inhibitors of GPVI produce a major defect in arterial thrombogenesis. In this study we have examined arterial thrombus formation in mice lacking the GPVI/FcRγ-chain complex (FcRγ–/–). Using 3 distinct arterial thrombosis models involving deep vascular injury, we demonstrate that deficiency of GPVI/FcRγ is not associated with a major defect in arterial thrombus formation. In contrast, with milder vascular injury deficiency of GPVI/FcRγ was associated with a 30% reduction in thrombus growth. Analysis of FcRγ–/– platelets in vitro, using thrombin-dependent and -independent thrombosis models, demonstrated a major role for thrombin in overcoming the thrombosis defect associated with GPVI/FcRγ deficiency. Inhibition of thrombin in vivo produced a much greater defect in thrombus formation in mice lacking GPVI/FcRγ compared with normal controls. Similarly, thrombin inhibition produced a marked prolongation in bleeding time in FcRγ–/– mice relative to wild-type mice. Our studies define an important role for thrombin in overcoming the hemostatic and thrombotic defect associated with GPVI/FcRγ deficiency. Moreover, they raise the interesting possibility that the full antithrombotic potential of GPVI receptor antagonists may only be realized through the concurrent administration of anticoagulant agents.
Publisher: American Society of Hematology
Date: 15-07-2004
DOI: 10.1182/BLOOD-2003-08-2881
Abstract: The glycoprotein Ib-V-IX (GPIb-V-IX) complex interacts with subendothelial von Willebrand factor (VWF) to ensure recruitment of platelets at sites of vascular injury, a process that culminates in integrin αIIbβ3-dependent stable adhesion and spreading. Interaction of the 14-3-3ζ adaptor protein with the C-terminal 606-610 phosphoserine motif of the GPIbα subunit has been implicated in the control of αIIbβ3 activation and cell spreading. In this study, we have examined potentially novel 14-3-3ζ binding sites by expressing mutant forms of GPIbα in Chinese-hamster-ovary (CHO) cells. Analysis of a series of neighboring 11-12 residue deletions identified a critical role for the 580-LVAGRRPSALS-590 sequence in promoting GPIbα-14-3-3ζ interaction. Development of a phosphospecific antibody demonstrated high levels of phosphorylation of the Ser587 and Ser590 residues in resting platelets (which became dephosphorylated during platelet spreading on VWF), and peptides containing these phosphorylated residues effectively displaced 14-3-3ζ from GPIbα. Analysis of single and double alanine substitutions of Ser587 and Ser590 demonstrated a major role for these residues in promoting GPIbα-14-3-3ζ binding. Moreover, these cell lines exhibited a defect in cell spreading on immobilized VWF. These studies demonstrate the existence of a second major 14-3-3ζ binding site within the cytoplasmic tail of GPIbα that has an important functional role in regulating integrin-dependent cell spreading. (Blood. 2004 :420-427)
Publisher: Elsevier BV
Date: 12-1999
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2020
DOI: 10.1161/ATVBAHA.120.314301
Abstract: Atherothrombosis occurs upon rupture of an atherosclerotic plaque and leads to the formation of a mural thrombus. Computational fluid dynamics and numerical models indicated that the mechanical stress applied to a thrombus increases dramatically as a thrombus grows, and that strong inter-platelet interactions are essential to maintain its stability. We investigated whether GPVI (glycoprotein VI)-mediated platelet activation helps to maintain thrombus stability by using real-time video-microscopy. We showed that GPVI blockade with 2 distinct Fab fragments promoted efficient disaggregation of human thrombi preformed on collagen or on human atherosclerotic plaque material in the absence of thrombin. ACT017-induced disaggregation was achieved under arterial blood flow conditions, and its effect increased with wall shear rate. GPVI regulated platelet activation within a growing thrombus as evidenced by the loss in thrombus contraction when GPVI was blocked, and the absence of the disaggregating effect of an anti-GPVI agent when the thrombi were fully activated with soluble agonists. The GPVI-dependent thrombus stabilizing effect was further supported by the fact that inhibition of any of the 4 key immunoreceptor tyrosine-based motif signalling molecules, src-kinases, Syk, PI3Kβ, or phospholipase C, resulted in kinetics of thrombus disaggregation similar to ACT017. The absence of ACT017-induced disaggregation of thrombi from 2 afibrinogenemic patients suggests that the role of GPVI requires interaction with fibrinogen. Finally, platelet disaggregation of fibrin-rich thrombi was also promoted by ACT017 in combination with r-tPA (recombinant tissue plasminogen activator). This work identifies an unrecognized role for GPVI in maintaining thrombus stability and suggests that targeting GPVI could dissolve platelet aggregates with a poor fibrin content.
Publisher: Elsevier BV
Date: 2002
Publisher: Elsevier BV
Date: 08-2003
Publisher: American Society for Clinical Investigation
Date: 15-03-2000
DOI: 10.1172/JCI7569
Publisher: Life Science Alliance, LLC
Date: 02-2019
Abstract: During platelet biogenesis, microtubules (MTs) are arranged into submembranous structures (the marginal band) that encircle the cell in a single plane. This unique MT array has no equivalent in any other mammalian cell, and the mechanisms responsible for this particular mode of assembly are not fully understood. One possibility is that platelet MTs are composed of a particular set of tubulin isotypes that carry specific posttranslational modifications. Although β1-tubulin is known to be essential, no equivalent roles of α-tubulin isotypes in platelet formation or function have so far been reported. Here, we identify α4A-tubulin as a predominant α-tubulin isotype in platelets. Similar to β1-tubulin, α4A-tubulin expression is up-regulated during the late stages of megakaryocyte differentiation. Missense mutations in the α4A-tubulin gene cause macrothrombocytopenia in mice and humans. Defects in α4A-tubulin lead to changes in tubulin tyrosination status of the platelet tubulin pool. Ultrastructural defects include reduced numbers and misarranged MT coils in the platelet marginal band. We further observed defects in megakaryocyte maturation and proplatelet formation in Tuba4a -mutant mice. We have, thus, discovered an α-tubulin isotype with specific and essential roles in platelet biogenesis.
Publisher: Elsevier BV
Date: 03-1999
Publisher: Life Science Alliance, LLC
Date: 21-06-2021
Publisher: Hindawi Limited
Date: 15-07-2014
DOI: 10.1002/HUMU.22607
Abstract: Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder characterized by defects of the GPIb-IX-V complex, a platelet receptor for von Willebrand factor (VWF). Most of the mutations identified in the genes encoding for the GP1BA (GPIbα), GP1BB (GPIbβ), and GP9 (GPIX) subunits prevent expression of the complex at the platelet membrane or more rarely its interaction with VWF. As a consequence, platelets are unable to adhere to the vascular subendothelium and agglutinate in response to ristocetin. In order to collect information on BSS patients, we established an International Consortium for the study of BSS, allowing us to enrol and genotype 132 families (56 previously unreported). With 79 additional families for which molecular data were gleaned from the literature, the 211 families characterized so far have mutations in the GP1BA (28%), GP1BB (28%), or GP9 (44%) genes. There is a wide spectrum of mutations with 112 different variants, including 22 novel alterations. Consistent with the rarity of the disease, 85% of the probands carry homozygous mutations with evidence of founder effects in some geographical areas. This overview provides the first global picture of the molecular basis of BSS and will lead to improve patient diagnosis and management.
Publisher: American Society of Hematology
Date: 16-10-2014
DOI: 10.1182/BLOOD-2014-01-551820
Abstract: We identify a new type of autosomal recessive macrothrombocytopenia associated with a mutation in PRKACG, coding the PKA catalytic subunit. The homozygous PRKACG mutation leads to a deep defect in proplatelet formation that was restored by the overexpression of wild-type PRKACG.
Publisher: American Society of Hematology
Date: 05-2003
DOI: 10.1182/BLOOD-2002-06-1847
Abstract: Glycoprotein (GP) Ib/V/IX complex–dependent platelet adhesion to von Willebrand factor (VWF) is supported by the 45-kd N-terminal extracellular domain of the GPIbα subunit. Recent results with an adhesion blocking antibody (RAM.1) against GPIbβ, which is disulfide linked to GPIbα, have suggested a novel function of this subunit in regulating VWF-mediated platelet adhesion, possibly involving its intracellular face. A putative cooperation between the GPIbα and GPIbβ cytoplasmic domains was investigated by measuring the adhesion under flow to immobilized VWF of K562 and Chinese hamster ovary (CHO) cells transfected with GPIb/(V)/IX containing mutations in this region. Adhesion of cells carrying a glycine substitution of the GPIbβ Ser166 phosphorylation site was 50% lower than normal and became insensitive to inhibition by RAM.1. In contrast, forskolin or PGE1 treatment increased both the phosphorylation of GPIbβ and adhesion of control cells, both effects being reversed by RAM.1, but had no influence on cells expressing the Ser166Gly mutation. A role of the GPIbα intracellular domain was also apparent as the VWF-dependent adhesion of cells containing deletions of the entire (Δ518-610) or portions (Δ535-568, Δ569-610) of the GPIbα cytoplasmic tail was insensitive to RAM.1 inhibition. Cells carrying progressive 11 amino acid deletions spanning the GPIbα 535-590 region were equally unresponsive to RAM.1, with the exception of those containing GPIbα Δ569-579, which behaved like control cells. These findings support a role of the GPIbβ intracellular domain in controlling the adhesive properties of the GPIb/V/IX complex through phosphorylation of GPIbβ Ser166 and point to the existence of cross-talk between the GPIbβ and GPIbα intracellular domains.
No related grants have been discovered for François Lanza.