Abstract
We have obtained evidence that selective inhibition of high affinity thrombin-binding sites located in the amino-terminal domain of the membrane glycoprotein (GP) Ibα results in impaired platelet activation, as shown by abrogation or reduction of the following responses induced in normal platelets by exposure to 2+](i)), (ii) release of dense granule content, (iii) binding of fibrinogen, (iv) aggregation. An anti-GP Ib monoclonal antibody, LJ-Ib10, which does not inhibit von Willebrand factor binding to platelets, obliterated the high affinity α-thrombin-binding sites on normal platelets. Isotherms of α-thrombin binding to normal platelets treated with saturating amounts of the antibody were virtually identical to those obtained with platelets from a patient with classical Bernard-Soulier syndrome. In parallel with decreased binding of the agonist, this antibody caused 50% inhibition of the maximal extent of platelet aggregation and 90% inhibition of ATP release induced by 0.3 nM α-thrombin. By inhibiting α-thrombin binding to GP Ib, the antibody prevented the activation of platelets exposed to low concentrations of the agonist, as demonstrated by abrogation of the increase in intraplatelet ionized calcium concentration induced in control platelets by 0.18 nM α-thrombin; under these conditions, fibrinogen binding was inhibited by 84%. Therefore, there is a correlation between occupancy of the high affinity sites for α-thrombin on GP Ibα and platelet activation, secretion, and aggregation, suggesting that GP Ibα is part of an α-thrombin receptor relevant for platelet function.
| Original language | English |
|---|---|
| Pages (from-to) | 23776-23783 |
| Number of pages | 8 |
| Journal | Journal of Biological Chemistry |
| Volume | 266 |
| Issue number | 35 |
| Publication status | Published - 1991 |
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ASJC Scopus subject areas
- Biochemistry
Cite this
Function of glycoprotein Ibα in platelet activation induced by α-thrombin. / De Marco, L.; Mazzucato, M.; Masotti, A.; Fenton, J. W.; Ruggeri, Z. M.
In: Journal of Biological Chemistry, Vol. 266, No. 35, 1991, p. 23776-23783.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Function of glycoprotein Ibα in platelet activation induced by α-thrombin
AU - De Marco, L.
AU - Mazzucato, M.
AU - Masotti, A.
AU - Fenton, J. W.
AU - Ruggeri, Z. M.
PY - 1991
Y1 - 1991
N2 - We have obtained evidence that selective inhibition of high affinity thrombin-binding sites located in the amino-terminal domain of the membrane glycoprotein (GP) Ibα results in impaired platelet activation, as shown by abrogation or reduction of the following responses induced in normal platelets by exposure to 2+](i)), (ii) release of dense granule content, (iii) binding of fibrinogen, (iv) aggregation. An anti-GP Ib monoclonal antibody, LJ-Ib10, which does not inhibit von Willebrand factor binding to platelets, obliterated the high affinity α-thrombin-binding sites on normal platelets. Isotherms of α-thrombin binding to normal platelets treated with saturating amounts of the antibody were virtually identical to those obtained with platelets from a patient with classical Bernard-Soulier syndrome. In parallel with decreased binding of the agonist, this antibody caused 50% inhibition of the maximal extent of platelet aggregation and 90% inhibition of ATP release induced by 0.3 nM α-thrombin. By inhibiting α-thrombin binding to GP Ib, the antibody prevented the activation of platelets exposed to low concentrations of the agonist, as demonstrated by abrogation of the increase in intraplatelet ionized calcium concentration induced in control platelets by 0.18 nM α-thrombin; under these conditions, fibrinogen binding was inhibited by 84%. Therefore, there is a correlation between occupancy of the high affinity sites for α-thrombin on GP Ibα and platelet activation, secretion, and aggregation, suggesting that GP Ibα is part of an α-thrombin receptor relevant for platelet function.
AB - We have obtained evidence that selective inhibition of high affinity thrombin-binding sites located in the amino-terminal domain of the membrane glycoprotein (GP) Ibα results in impaired platelet activation, as shown by abrogation or reduction of the following responses induced in normal platelets by exposure to 2+](i)), (ii) release of dense granule content, (iii) binding of fibrinogen, (iv) aggregation. An anti-GP Ib monoclonal antibody, LJ-Ib10, which does not inhibit von Willebrand factor binding to platelets, obliterated the high affinity α-thrombin-binding sites on normal platelets. Isotherms of α-thrombin binding to normal platelets treated with saturating amounts of the antibody were virtually identical to those obtained with platelets from a patient with classical Bernard-Soulier syndrome. In parallel with decreased binding of the agonist, this antibody caused 50% inhibition of the maximal extent of platelet aggregation and 90% inhibition of ATP release induced by 0.3 nM α-thrombin. By inhibiting α-thrombin binding to GP Ib, the antibody prevented the activation of platelets exposed to low concentrations of the agonist, as demonstrated by abrogation of the increase in intraplatelet ionized calcium concentration induced in control platelets by 0.18 nM α-thrombin; under these conditions, fibrinogen binding was inhibited by 84%. Therefore, there is a correlation between occupancy of the high affinity sites for α-thrombin on GP Ibα and platelet activation, secretion, and aggregation, suggesting that GP Ibα is part of an α-thrombin receptor relevant for platelet function.
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M3 - Article
VL - 266
SP - 23776
EP - 23783
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 35
ER -