SELECTIN

'Selectins' are a family of cell adhesion molecules (or CAM's). All selectins are single-chain transmembrane glycoproteins which share similar properties to C-type lectins due to a related amino terminus and calcium-dependent binding^[1].

Contents

Types

Etymology

Function

External links

References

Types

There are three subsets of selectins:

★ E-selectin (in endothelial cells)

★ L-selectin (in leukocytes)

★ P-selectin (in platelets and endothelial cells)

Etymology

The name selectin comes from the words "selected" and "lectins" which are a type of carbohydrate recognizing proteins.

Function

During an inflammatory response stimuli such as histamine and thrombin cause endothelial cells to mobilize P-selectin from stores inside the cell to the cell surface. In addition, cytokines such as TNF-alpha stimulate the expression of E-selectin and additional P-selectin a few hours later.
As the leukocyte rolls along the blood vessel wall, the distal lectin-like domain of the selectin binds to certain carbohydrate groups presented on proteins (such as PSGL-1) on the leukocyte, which slows the cell and allows it to leave the blood vessel and enter the site of infection. The low-affinity nature of selectins is what allows the characteristic "rolling" action attributed to leukocytes during the leukocyte adhesion cascade^[2].
The best-characterized ligand for the three selectins is P-selectin glycoprotein ligand-1 (PSGL-1), which is a mucin-type glycoprotein expressed on all white blood cells.
Neutrophils and eosinophils bind to E-selectin. One of the reported ligands for E-selectin is the sialylated Lewis X Ag (sLe(x)). Eosinophils, like neutrophils, use sialylated, protease-resistant structures to bind to E-selectin, although the eosinophil expresses much lower levels of these structures on its surface. ^[3]
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.
^[4]

External links

★ Computer-generated movie of the mobilization of P-selectin inside a leukocyte at mcb.harvard.edu

References

1. Robbins Pathologic Basis of Disease, , , Cotran, W.B Saunders Company, , 0-7216-7335-X
2.
3. Differences between human eosinophils and neutrophils in the function and expression of sialic acid-containing counterligands for E-selectin, , , Bochner BS, Sterbinsky SA, Bickel CA, Werfel S, Wein M, Newman W., J Immunol.,
4.
Comparison of human eosinophil and neutrophil ligands for P-selectin: ligands for P-selectin differ from those for E-selectin., , M, Wein, Am J Respir Cell Mol Biol.,