Related Experiment Video
Updated: Jun 14, 2026
08:30
Investigating von Willebrand Factor Pathophysiology Using a Flow Chamber Model of von Willebrand Factor-platelet String Formation
Published on: August 14, 2017
GPVI and CLEC-2 in hemostasis and vascular integrity
S P Watson1, J M J Herbert, A Y Pollitt
1Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. s.p.watson@bham.ac.uk
Journal of Thrombosis and Haemostasis : JTH
|March 30, 2010
Summary
Platelet activation by glycoprotein VI (GPVI) and CLEC-2 receptors involves distinct signaling pathways. GPVI uses an immunoreceptor tyrosine-based activation motif (ITAM), while CLEC-2 utilizes a hemITAM for platelet activation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Platelet activation is crucial for hemostasis and vascular integrity.
- Glycoprotein VI (GPVI) and CLEC-2 are key platelet receptors involved in activation.
- Both receptors signal through Src and Syk tyrosine kinases but employ different mechanisms.
Purpose of the Study:
- To compare the distinct signaling mechanisms of GPVI and CLEC-2 in platelet activation.
- To elucidate the roles of ITAM and hemITAM motifs in receptor signaling.
- To explore the functional significance of GPVI and CLEC-2 in hemostasis and vascular biology.
Main Methods:
- Comparative analysis of GPVI and CLEC-2 signaling pathways.
- Investigation of immunoreceptor tyrosine-based activation motif (ITAM) and hemITAM function.
- Examination of Src and Syk kinase involvement in platelet activation.
Main Results:
- GPVI initiates platelet activation via an ITAM-regulated pathway involving Syk kinase and phospholipase Cgamma2 (PLCgamma2).
- CLEC-2 mediates platelet activation through Src and Syk kinases via a novel hemITAM dimerization mechanism.
- Podoplanin binding to CLEC-2 triggers potent platelet activation.
Conclusions:
- GPVI and CLEC-2 represent distinct yet powerful pathways for platelet activation.
- Understanding these pathways is vital for comprehending hemostasis, vascular integrity, angiogenesis, and lymphogenesis.
- The differential regulation of Syk kinase by ITAM and hemITAM highlights unique receptor signaling strategies.
Related Concept Videos
01:20Extrinsic and Intrinsic Pathways of Hemostasis
Blood clotting or coagulation involves extrinsic and intrinsic pathways, which ultimately merge into the common pathway, forming a fibrin clot.
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which forms a...
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which forms a...
01:05Introduction to Hemostasis
Hemostasis is a complex physiological process that prevents excessive bleeding when a blood vessel is injured. It's crucial for maintaining the integrity of the circulatory system, as it ensures that our blood remains fluid while still within the vascular network and yet clots to prevent blood loss upon vessel injury.
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized, and...
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized, and...
01:22Formation of the Platelet Plug
The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
01:24Regulation of Angiogenesis and Blood Supply
Rapidly dividing tumors, embryos, and wounded tissues require more oxygen than usual, lowering the oxygen concentration in the blood. At low oxygen or hypoxic conditions, an oxygen-sensitive transcription factor called the hypoxia-inducible factor 1 or HIF1 is activated. HIF1 is a dimeric protein of alpha (ɑ) and beta (β) subunits. Under optimal oxygen conditions, HIF1β is present in the nucleus while HIF1ɑ remains in the cytosol. HIF1ɑ is hydroxylated by prolyl hydroxylase and factor...
01:16Clot Retraction and Fibrinolysis
After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.
01:16Vascular Spasm
The vascular phase, also known as vasospasm, is the initial stage of hemostasis, crucial for preventing excessive bleeding when a blood vessel is injured. After a vessel is cut, nerves in the damaged area trigger pain and other sensory impulses. Simultaneously, the smooth muscles in the vessel wall contract, resulting in a vascular spasm. This contraction reduces the vessel's diameter at the injury site, slowing or stopping blood loss through the vessel wall. Vascular spasms typically last for...