P-selectin
Encyclopedia
P-selectin is a cell adhesion molecule
(CAM
) on the surfaces of activated endothelial cells, which line the inner surface of blood vessels, and activated platelets. In unactivated endothelial cells, it is stored in granules called Weibel-Palade bodies, and α-granules in unactivated platelets.
Other names for P-selectin include CD62P, Granule Membrane Protein 140 (GMP-140), and Platelet Activation-Dependent Granule to External Membrane Protein (PADGEM). It was first shown to be found in endothelial cells in 1989.
. When endothelial cells are activated by molecules such as histamine or thrombin during inflammation, P-selectin moves from an internal cell location to the endothelial cell surface.
Thrombin
is one trigger which can stimulate endothelial-cell release of P-selectin and recent studies suggest an additional Ca2+-independent pathway involved in release of P-selectin.
Ligands for P-selectin on eosinophils and neutrophils are similar sialylated, protease-sensitive, endo-beta-galactosidase-resistant structures, clearly different than those reported for E-selectin, and suggest disparate roles for P-selectin and E-selectin during recruitment during inflammatory responses.
P-selectin is also very important in the recruitment and aggregation of platelets at areas of vascular injury. In quiescent platelet, P-selectin is located on the inner wall of α-granules. Platelet activation (through agonists such as thrombin, Type II collagen and ADP) results in "membrane flipping" where the platelet releases α- and dense granules and the inner walls of the granules are exposed on the outside of the cell. The P-selectin then promotes platelet aggregation through platelet-fibrin and platelet-platelet binding.
P-selectin attaches to the actin
cytoskeleton through anchor proteins that are still poorly characterized.
Cell adhesion molecule
Cell Adhesion Molecules are proteins located on the cell surface involved with the binding with other cells or with the extracellular matrix in the process called cell adhesion....
(CAM
Cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
) on the surfaces of activated endothelial cells, which line the inner surface of blood vessels, and activated platelets. In unactivated endothelial cells, it is stored in granules called Weibel-Palade bodies, and α-granules in unactivated platelets.
Other names for P-selectin include CD62P, Granule Membrane Protein 140 (GMP-140), and Platelet Activation-Dependent Granule to External Membrane Protein (PADGEM). It was first shown to be found in endothelial cells in 1989.
Function
P-selectin plays an essential role in the initial recruitment of leukocytes (white blood cells) to the site of injury during inflammationInflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
. When endothelial cells are activated by molecules such as histamine or thrombin during inflammation, P-selectin moves from an internal cell location to the endothelial cell surface.
Thrombin
Thrombin
Thrombin is a "trypsin-like" serine protease protein that in humans is encoded by the F2 gene. Prothrombin is proteolytically cleaved to form thrombin in the first step of the coagulation cascade, which ultimately results in the stemming of blood loss...
is one trigger which can stimulate endothelial-cell release of P-selectin and recent studies suggest an additional Ca2+-independent pathway involved in release of P-selectin.
Ligands for P-selectin on eosinophils and neutrophils are similar sialylated, protease-sensitive, endo-beta-galactosidase-resistant structures, clearly different than those reported for E-selectin, and suggest disparate roles for P-selectin and E-selectin during recruitment during inflammatory responses.
P-selectin is also very important in the recruitment and aggregation of platelets at areas of vascular injury. In quiescent platelet, P-selectin is located on the inner wall of α-granules. Platelet activation (through agonists such as thrombin, Type II collagen and ADP) results in "membrane flipping" where the platelet releases α- and dense granules and the inner walls of the granules are exposed on the outside of the cell. The P-selectin then promotes platelet aggregation through platelet-fibrin and platelet-platelet binding.
P-selectin attaches to the actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
cytoskeleton through anchor proteins that are still poorly characterized.