Limits...
Pregnancy-specific glycoproteins bind integrin αIIbβ3 and inhibit the platelet-fibrinogen interaction.

Shanley DK, Kiely PA, Golla K, Allen S, Martin K, O'Riordan RT, Ball M, Aplin JD, Singer BB, Caplice N, Moran N, Moore T - PLoS ONE (2013)

Bottom Line: The presence of a KGD in barbourin, a platelet integrin αIIbβ3 antagonist found in snake venom, suggested that PSG1 may be a selective αIIbβ3 ligand.Here we show that human PSG1 binds αIIbβ3 and inhibits the platelet - fibrinogen interaction.Unexpectedly, however, the KGD is not critical as multiple PSG1 domains independently bind and inhibit αIIbβ3 function.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University College Cork, Cork, Ireland.

ABSTRACT
Pregnancy-specific glycoproteins (PSGs) are immunoglobulin superfamily members encoded by multigene families in rodents and primates. In human pregnancy, PSGs are secreted by the syncytiotrophoblast, a fetal tissue, and reach a concentration of up to 400 ug/ml in the maternal bloodstream at term. Human and mouse PSGs induce release of anti-inflammatory cytokines such as IL-10 and TGFβ1 from monocytes, macrophages, and other cell types, suggesting an immunoregulatory function. RGD tri-peptide motifs in the majority of human PSGs suggest that they may function like snake venom disintegrins, which bind integrins and inhibit interactions with ligands. We noted that human PSG1 has a KGD, rather than an RGD motif. The presence of a KGD in barbourin, a platelet integrin αIIbβ3 antagonist found in snake venom, suggested that PSG1 may be a selective αIIbβ3 ligand. Here we show that human PSG1 binds αIIbβ3 and inhibits the platelet - fibrinogen interaction. Unexpectedly, however, the KGD is not critical as multiple PSG1 domains independently bind and inhibit αIIbβ3 function. Human PSG9 and mouse Psg23 are also inhibitory suggesting conservation of this function across primate and rodent PSG families. Our results suggest that in species with haemochorial placentation, in which maternal blood is in direct contact with fetal trophoblast, the high expression level of PSGs reflects a requirement to antagonise abundant (3 mg/ml) fibrinogen in the maternal circulation, which may be necessary to prevent platelet aggregation and thrombosis in the prothrombotic maternal environment of pregnancy.

Show MeSH

Related in: MedlinePlus

PSG1 is anti-thrombotic under arterial flow.a & b, Representative images of adhesion of platelets under arterial flow following addition of 200 µg/ml PSG1 to 3 ml of circulating whole human blood. 200 µg/ml rabbit IgG was used as a negative control. Abciximab, an αIIbβ3 antagonist, was used as a positive control. b, Summary data of eight replicated independent arterial flow experiments expressed as means ± S.E.M. *, P<0.05; **, P<0.005; ***, P<0.0005 vs IgG, Mann Whitney test.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3585349&req=5

pone-0057491-g004: PSG1 is anti-thrombotic under arterial flow.a & b, Representative images of adhesion of platelets under arterial flow following addition of 200 µg/ml PSG1 to 3 ml of circulating whole human blood. 200 µg/ml rabbit IgG was used as a negative control. Abciximab, an αIIbβ3 antagonist, was used as a positive control. b, Summary data of eight replicated independent arterial flow experiments expressed as means ± S.E.M. *, P<0.05; **, P<0.005; ***, P<0.0005 vs IgG, Mann Whitney test.

Mentions: We next determined whether PSG1 exhibits anti-thrombotic activity in a model of vascular flow using an experimental system in which human whole blood flows through a type 1 collagen-coated channel. We used a force of 15 dyn/cm2 which mimics arterial shear [56]. In operator-blinded experiments, 200 µg/ml PSG1 or 200 µg/ml rabbit IgG was added to blood and the extent of platelet adhesion was estimated by fluorescence microscopy at 5, 15 and 30 minutes after commencement of flow (n = 8). The αIIbβ3 antagonist Abciximab at 20 µg/ml was used as a positive control and, as expected, completely inhibited platelet deposition (n = 5). PSG1 reduced thrombus coverage at all time points compared to the IgG control, with a maximum reduction of 50% at 5 minutes (Fig. 4).


Pregnancy-specific glycoproteins bind integrin αIIbβ3 and inhibit the platelet-fibrinogen interaction.

Shanley DK, Kiely PA, Golla K, Allen S, Martin K, O'Riordan RT, Ball M, Aplin JD, Singer BB, Caplice N, Moran N, Moore T - PLoS ONE (2013)

PSG1 is anti-thrombotic under arterial flow.a & b, Representative images of adhesion of platelets under arterial flow following addition of 200 µg/ml PSG1 to 3 ml of circulating whole human blood. 200 µg/ml rabbit IgG was used as a negative control. Abciximab, an αIIbβ3 antagonist, was used as a positive control. b, Summary data of eight replicated independent arterial flow experiments expressed as means ± S.E.M. *, P<0.05; **, P<0.005; ***, P<0.0005 vs IgG, Mann Whitney test.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585349&req=5

pone-0057491-g004: PSG1 is anti-thrombotic under arterial flow.a & b, Representative images of adhesion of platelets under arterial flow following addition of 200 µg/ml PSG1 to 3 ml of circulating whole human blood. 200 µg/ml rabbit IgG was used as a negative control. Abciximab, an αIIbβ3 antagonist, was used as a positive control. b, Summary data of eight replicated independent arterial flow experiments expressed as means ± S.E.M. *, P<0.05; **, P<0.005; ***, P<0.0005 vs IgG, Mann Whitney test.
Mentions: We next determined whether PSG1 exhibits anti-thrombotic activity in a model of vascular flow using an experimental system in which human whole blood flows through a type 1 collagen-coated channel. We used a force of 15 dyn/cm2 which mimics arterial shear [56]. In operator-blinded experiments, 200 µg/ml PSG1 or 200 µg/ml rabbit IgG was added to blood and the extent of platelet adhesion was estimated by fluorescence microscopy at 5, 15 and 30 minutes after commencement of flow (n = 8). The αIIbβ3 antagonist Abciximab at 20 µg/ml was used as a positive control and, as expected, completely inhibited platelet deposition (n = 5). PSG1 reduced thrombus coverage at all time points compared to the IgG control, with a maximum reduction of 50% at 5 minutes (Fig. 4).

Bottom Line: The presence of a KGD in barbourin, a platelet integrin αIIbβ3 antagonist found in snake venom, suggested that PSG1 may be a selective αIIbβ3 ligand.Here we show that human PSG1 binds αIIbβ3 and inhibits the platelet - fibrinogen interaction.Unexpectedly, however, the KGD is not critical as multiple PSG1 domains independently bind and inhibit αIIbβ3 function.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University College Cork, Cork, Ireland.

ABSTRACT
Pregnancy-specific glycoproteins (PSGs) are immunoglobulin superfamily members encoded by multigene families in rodents and primates. In human pregnancy, PSGs are secreted by the syncytiotrophoblast, a fetal tissue, and reach a concentration of up to 400 ug/ml in the maternal bloodstream at term. Human and mouse PSGs induce release of anti-inflammatory cytokines such as IL-10 and TGFβ1 from monocytes, macrophages, and other cell types, suggesting an immunoregulatory function. RGD tri-peptide motifs in the majority of human PSGs suggest that they may function like snake venom disintegrins, which bind integrins and inhibit interactions with ligands. We noted that human PSG1 has a KGD, rather than an RGD motif. The presence of a KGD in barbourin, a platelet integrin αIIbβ3 antagonist found in snake venom, suggested that PSG1 may be a selective αIIbβ3 ligand. Here we show that human PSG1 binds αIIbβ3 and inhibits the platelet - fibrinogen interaction. Unexpectedly, however, the KGD is not critical as multiple PSG1 domains independently bind and inhibit αIIbβ3 function. Human PSG9 and mouse Psg23 are also inhibitory suggesting conservation of this function across primate and rodent PSG families. Our results suggest that in species with haemochorial placentation, in which maternal blood is in direct contact with fetal trophoblast, the high expression level of PSGs reflects a requirement to antagonise abundant (3 mg/ml) fibrinogen in the maternal circulation, which may be necessary to prevent platelet aggregation and thrombosis in the prothrombotic maternal environment of pregnancy.

Show MeSH
Related in: MedlinePlus