Evidence for Two Distinct Epitopes within Collagen for Activation of Murine Platelets

Schulte, Valerie; Snell, Daniel C.; Bergmeier, Wolfgang; Zirngibl, Hubert; Watson, Steve P.; Nieswandt, Bernhard

doi:10.1074/jbc.m007536200

Cited by 38 publications

(60 citation statements)

References 21 publications

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“…However, this antibody was not completely effective in inhibiting aggregation using higher concentrations of fibrillar collagen, 34 leading the investigators to conclude the presence of a second collagen receptor or second collagen binding site on mouse GP VI important for aggregation. Our data do not support this conclusion as we observed a complete absence of aggregation at concentrations exceeding those used by investigators using inhibitory antibodies.…”

Section: Discussionmentioning

confidence: 99%

“…Our data do not support this conclusion as we observed a complete absence of aggregation at concentrations exceeding those used by investigators using inhibitory antibodies. 34 Moreover, in more recent work, 35 the attainment of an antibody-induced platelet GP VI deficiency produced a lack of platelet adhesion and aggregation on a damaged vessel wall. Our results do not support a direct participation of GP VI in the initial tethering of platelets to a surface presenting collagen type I fibrils (Figures 5-6; Videos 1-2), in agreement with the concept that essential for this process under high flow conditions is the interaction of GP Ib␣ with collagen-bound von Willebrand factor.…”

Section: Discussionmentioning

confidence: 99%

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The contribution of glycoprotein VI to stable platelet adhesion and thrombus formation illustrated by targeted gene deletion

Kato

Kanaji

Russell

et al. 2003

Blood

251

205

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Platelet interaction with exposed adhesive ligands at sites of vascular injury is required to initiate a normal hemostatic response and may become a pathogenic factor in arterial diseases leading to thrombosis. We report a targeted disruption in a key receptor for collageninduced platelet activation, glycoprotein (GP) VI. The breeding of mice with heterozygous GP VI alleles produced the expected frequency of wild-type, heterozygous, and homozygous genotypes, indicating that these animals had no reproductive problems and normal viability. GP VI null platelets failed to aggregate in response to type I fibrillar collagen or convulxin, a snake venom protein and known platelet agonist of GP VI. Nevertheless, tail bleeding time measurements revealed no severe bleeding tendency as a consequence of GP VI deficiency. Ex vivo platelet thrombus formation on type I collagen fibrils was abolished using blood from either GP VI null or FcR-␥ null animals. Reflection interference contrast microscopy revealed that the lack of thrombus formation by GP VI null platelets could be linked to a defective platelet activation following normal initial tethering to the surface, visualized as lack of spreading and less stable adhesion. These results illustrate the role of GP VI in postadhesion events leading to the development of platelet thrombi on collagen fibrils. IntroductionPlatelet membrane receptors interact with surface-bound adhesive ligands and, as such, become essential for hemostasis and thrombosis. 1 There are numerous unique receptors interacting with different adhesive ligands suggesting that a large opportunity exists for functional redundancy in platelet adhesion. However, an emerging theme of platelet biology is the relevance of different membrane receptors in different areas of the vasculature. 2,3 A specific example is the exclusive role for the platelet glycoprotein (GP) Ib-IX-V complex and von Willebrand factor in areas of the vascular system where flow rates and high shear occur, such as in small arteries and arterioles. 4 Thus, defining the physiologic relevance of an individual receptor and its ligand is an important aspect for understanding participation of the platelet in hemostasis and thrombosis.Among adhesive ligands of the extravascular matrix, collagen is a significant component with a number of known collagen receptors on the platelet surface. 5,6 One of the more recently characterized collagen receptors is GP VI. 7 The molecular cloning of GP VI revealed it to be a member of the immunoglobulin superfamily of type I transmembrane proteins. [8][9][10] The surface expression of GP VI requires the concomitant expression of the ␥-subunit of the FcR receptor (FcR-␥) and their association is functionally relevant as collagen binding to GP VI results in platelet signaling via the immunoreceptor tyrosine-based activation motif (ITAM) located in the FcR-␥ subunit. 8,[11][12][13][14] As with many of the platelet receptors, the in vivo relevance of GP VI was established prior to its description and recognition as a p...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The contribution of glycoprotein VI to stable platelet adhesion and thrombus formation illustrated by targeted gene deletion

Kato

Kanaji

Russell

et al. 2003

Blood

251

205

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“…Collagen-related peptide (CRP) concentrates these motifs by crosslinking peptides with a GKO-(GPO) 10 -GKOG motif and is a strong platelet activator by inducing signaling through GPVI and the Syk-LAT signalosome (Pasquet et al, 1999). As JAQ1 blocks the CRP-binding site of GPVI (Schulte et al, 2001), we tested the effect of CRP and its mixture with collagen I on PPF. Interestingly, CRP had no effect on PPF and, when mixed with collagen I, it acted as collagen IV in competing with binding sites without transducing any inhibitory signal (Fig.…”

Section: Megakaryocytes Derived From Gp6mentioning

confidence: 99%

Proplatelet formation is selectively inhibited by collagen type I through Syk-independent GPVI signaling

Semeniak

Kulawig

Stegner

et al. 2016

Journal of Cell Science

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Collagen receptors GPVI (also known as GP6) and integrin α2β1 are highly expressed on blood platelets and megakaryocytes, their immediate precursors. After vessel injury, subendothelial collagen becomes exposed and induces platelet activation to prevent blood loss. Collagen types I and IV are thought to have opposite effects on platelet biogenesis, directing proplatelet formation (PPF) towards the blood vessels to prevent premature release within the marrow cavity. We used megakaryocytes lacking collagen receptors or treated megakaryocytes with blocking antibodies, and could demonstrate that collagen-I-mediated inhibition of PPF is specifically controlled by GPVI. Other collagen types competed for binding and diminished the inhibitory signal, which was entirely dependent on receptor-proximal Src family kinases, whereas Syk and LAT were dispensable. Adhesion assays indicate that megakaryocyte binding to collagens is mediated by α2β1, and that collagen IV at the vascular niche might displace collagen I from megakaryocytes and thus contribute to prevention of premature platelet release into the marrow cavity and thereby directionally promote PPF at the vasculature.

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“…The evidence that GPVI is the other major, established receptor essential for signaling and platelet activation was based on studies on patients with mild bleeding problems, whose platelets had an impaired response to collagen but not to other agonists and were GPVI-deficient (7,8). This was substantiated by studies with GPVI-specific agonists including collagen-related peptide (9), convulxin, a snake C-type lectin (10,11), and a rat monoclonal antibody JAQ1 (12), all of which stimulate a tyrosine phosphorylation pattern resembling that induced by collagen in platelets. GPVI is a member of the Ig superfamily and has a sequence and structure very similar to Fc␣R and to some of the natural killer receptor family (13).…”

mentioning

confidence: 88%

“…Convulxin was the first snake C-type lectin shown to bind specifically to GPVI (11,12) and along with collagen-related peptides and antibodies to GPVI it became a very useful tool to study the structure and function of GPVI and, in particular, platelet activation mechanisms through GPVI. Many snake C-type lectins that activate platelets to various extents have been reported that either have different receptors or have different affinities for the same receptors, even though they share a high degree of sequence similarities.…”

Section: Discussionmentioning

confidence: 99%

Ophioluxin, a Convulxin-like C-type Lectin from Ophiophagus hannah (King Cobra) Is a Powerful Platelet Activator via Glycoprotein VI

Clemetson

Navdaev

et al. 2002

Journal of Biological Chemistry

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Ophioluxin, a potent platelet agonist, was purified from the venom of Ophiophagus hannah (King cobra). Under nonreducing conditions it has a mass of 85 kDa, similar to convulxin, and on reduction gives two subunits with masses of 16 and 17 kDa, slightly larger than those of convulxin. The N-terminal sequences of both subunits are very similar to those of convulxin and other C-type lectins. Ophioluxin induces a pattern of tyrosine-phosphorylated proteins in platelets like that caused by convulxin, when using appropriate concentrations based on aggregation response, because it is about 2-4 times more powerful as agonist than the latter. Ophioluxin and convulxin induce [Ca 2؉ ] i elevation both in platelets and in Dami megakaryocytic cells, and each of these C-type lectins desensitizes responses to the other. Convulxin agglutinates fixed platelets at 2 g/ml, whereas ophioluxin does not, even at 80 g/ml. Ophioluxin resembles convulxin more than echicetin or alboaggregin B because polyclonal anti-ophioluxin antibodies recognize both ophioluxin and convulxin, but not echicetin, and platelets adhere to and spread on ophioluxin-or convulxin-precoated surfaces in the same way that is clearly different from their behavior on an alboaggregin B surface. Immobilized ophioluxin was used to isolate the glycoprotein VI-Fc␥ complex from resting platelets, which also contained Fyn, Lyn, Syk, LAT, and SLP76. Ophioluxin is the first multiheterodimeric, convulxin-like snake C-type lectin, as well as the first platelet agonist, to be described from the Elapidae snake family.Collagens in the vascular subendothelium and vessel wall are important platelet activators that have a critical role in hemostasis. A large number of different receptors have been proposed for collagen on platelets, including CD36 (glycoprotein (GP) 1 IV, GPIIIb) (1), GPIb-V-IX complex as an indirect collagen receptor acting via von Willebrand factor (2), a 65-kDa collagen type I specific receptor (3), and a 68 -72-kDa doublet collagen type III-specific receptor (4), but the major ones have been identified as the integrin ␣ 2 ␤ 1 and Ig superfamily member GPVI. Integrin ␣ 2 ␤ 1 belongs to the class containing an I-domain, which has been well characterized and is considered to be responsible for platelet adhesion to collagen rather than platelet activation (5, 6) for which GPVI is largely responsible. The evidence that GPVI is the other major, established receptor essential for signaling and platelet activation was based on studies on patients with mild bleeding problems, whose platelets had an impaired response to collagen but not to other agonists and were 8). This was substantiated by studies with GPVI-specific agonists including collagen-related peptide (9

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Evidence for Two Distinct Epitopes within Collagen for Activation of Murine Platelets

Cited by 38 publications

References 21 publications

The contribution of glycoprotein VI to stable platelet adhesion and thrombus formation illustrated by targeted gene deletion

The contribution of glycoprotein VI to stable platelet adhesion and thrombus formation illustrated by targeted gene deletion

Proplatelet formation is selectively inhibited by collagen type I through Syk-independent GPVI signaling

Ophioluxin, a Convulxin-like C-type Lectin from Ophiophagus hannah (King Cobra) Is a Powerful Platelet Activator via Glycoprotein VI

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