Platelet membrane glycoprotein

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Platelet membrane glycoproteins are surface

thrombocytes) which play a key role in hemostasis. When the blood vessel wall is damaged, platelet membrane glycoproteins interact with the extracellular matrix
.

Receptors involved in platelet adhesion to collagen

Membrane glycoproteins GPIa/IIa, GPVI and probably GPIV as well, function as collagen receptors, engaged in platelet adhesion to collagen. The leading role in the elimination of high-stress injury is taken by the glycoprotein Ib-IX-V complex.

Interactions of the platelet surface glycoproteins

The binding of von Willebrand factor (vWF) results in conformational changes within the GPIb-V-IX complex. In consequence, this complex activates GPIIb / IIIa membrane glycoproteins, allowing them to bind fibrinogen. Fibrinogen molecules then interconnect the platelets, serving as the basis for platelet aggregation. In the absence of fibrinogen, the platelets are joined by vWF due to its ability to bind the activated GPIIb / IIIa complex.

Membrane glycoproteins

Glycoprotein Ib-IX-V complex (GPIb-IX-V)

This transmembrane glycoprotein complex is composed of four subunits:

disulfide bridges, while the GPV and GPIX associate non-covalently with the complex. The GPIbα subunit bears the binding site for von Willebrand factor (vWF), α-thrombin, leukocyte integrin αMβ2 and P-selectin. The binding between GPIbα and vWF mediates the capture of platelets to the injured vascular wall. The deficiency in glycoprotein Ib-IX-V complex synthesis leads to Bernard–Soulier syndrome.[1]

Glycoprotein VI (GPVI)

Glycoprotein VI is one of the

LAT adaptor protein, all participating in phospholipase C activation.[2]

Glycoprotein Ia / IIa complex (
β1
)

This is a receptor for

Glycoprotein IIb / IIIa complex (
β3
)

This complex interacts with

disulfide bridges
. The β3 (GPIIIa) forms a single polypeptide chain. These subunits form Ca2+ - dependent complex on the surface of platelet membrane in a 1:1 ratio.

Fibrinogen sites recognized by glycoprotein IIb / IIIa complex:

  • dodecapeptide located in the C-terminal of the fibrinogen γ chain (the most important)
  • RGD sequence of the α chain → the
    Aspartate
    amino acid sequence

This complex also binds vWF,

inositol triphosphate. Consequently, there is a release of calcium ions that activate calpain. Calpain cleaves aggregin, and thus allows for joining of the two subunits. Deficiency in the IIb / IIIa complex is described as Glanzmann's thrombasthenia. Patients completely lack the ability to aggregate platelets.[4]

GPV / IIIa (
β1
)

This is a

platelets
. Its main function is in the adhesion of cells to the extracellular matrix components.

References

  1. .
  2. ^ ESTAVILLO, RITCHIE, DIACOVO a CRUZ. Functional Analysis of a Recombinant Glycoprotein Ia/IIa (Integrin α2β1) I Domain That Inhibits Platelet Adhesion to Collagen and Endothelial Matrix under Flow Conditions. The Journal of Biological Chemistry,. s. -. DOI: 10.1074/jbc.274.50.35921. Available online: http://www.jbc.org/content/274/50/35921.long

External links