Role of the intracellular domains of GPIb in controlling the adhesive properties of the platelet GPIb/V/IX complex

Abstract

Glycoprotein (GP)Ib

The Antithrombotic Activity of EP224283, a Neutralizable Dual Factor Xa Inhibitor/Glycoprotein IIbIIIa Antagonist, Exceeds That of the Coadministered Parent Compounds

“…Whole blood (5 l) drawn from the mouse tail was diluted 1 to 10 in Tyrode's buffer (137 mM NaCl, 2 mM KCl, 12 mM NaHCO 3 , 0.3 mM NaH 2 PO 4 , 1 mM MgCl 2 , 2 mM CaCl 2 , 5.5 mM glucose, 5 mM HEPES, pH 7.3) containing 0.35% human serum albumin and hirudin (100 U/ml) and incubated with an Alexa-647-conjugated rat monoclonal antibody against mouse glycoprotein Ib␤ (2 g/ml) (Perrault et al, 2003) and Alexa-488-conjugated fibrinogen (20 g/ml) for 10 min at 37°C, in the presence of either PAR-4 peptide (1 mM) or vehicle (plain Tyrode's buffer). Samples were then fixed for 20 min in plain Tyrode's buffer containing 2% paraformaldehyde.…”

Targeting Platelet GPIbβ Reduces Platelet Adhesion, GPIb Signaling and Thrombin Generation and Prevents Arterial Thrombosis

“…30,31 Although the precise mechanisms of these effects remain unclear, RAM.1 does not seem to prevent VWF binding to GPIbα through a steric hindrance notably supported by the fact that a Fab fragment of this antibody had a similar effect. 30 It has recently been reported that RAM.1 did not modify VWF binding to GPIb-IX reconstituted in phospholipid bilayer nanodiscs, further suggesting that the effect of RAM.1 may not be attributable to direct interference with the VWF-GPIbα interaction.…”

Glycoprotein Ibα forms disulfide bonds with 2 glycoprotein Ibβ subunits in the resting platelet

“…[3][4][5][6][7] How this receptor complex mediates signaling in both directions is not clear, but recent work has suggested the likely interaction between the Ib␣ and Ib␤ subunits as a potential key element of the mechanism. [8][9][10] Thus, understanding the interaction between GP Ib␣ and GP Ib␤, and in general the organizing principle of the GP Ib-IX-V complex, will help to unveil the mechanism underlying transmembrane signaling mediated by the complex.It is widely accepted that the GP Ib-IX-V complex contains 7 subunits composed of 4 different polypeptides: Ib␣, Ib␤, IX, and V with a respective stoichiometry of 2:2:2:1. [11][12][13][14][15] Each subunit is a type I transmembrane protein.…”

“…[35][36][37][38][39] Both interactions are important to the function of the GP Ib-IX-V complex. [3][4][5]8,9,40 14-3-3 is a dimer, and disrupting 14-3-3 dimerization decreases its affinity for the GP Ib-IX complex but not the isolated peptide containing the Ib␣ cytoplasmic domain. 41 On the basis of the ␣␤ heterodimeric model for GP Ib, it was thought that 2 monomers in the 14-3-3 dimer interact with the Ib␣ and Ib␤ cytoplasmic domains, respectively, with the implicit assumption that one 14-3-3 dimer interacts with one GP Ib complex.…”