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Selectin
From Wikipedia, the free encyclopedia
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].
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There are three subsets of selectins:
- E-selectin (in endothelial cells)
- L-selectin (in leukocytes)
- P-selectin (in platelets and endothelial cells)
The name selectin comes from the words "selected" and "lectins" which are a type of carbohydrate recognizing proteins.
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[1].
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. [2] 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. [3]
- ^ a b Cotran; Kumar, Collins. Robbins Pathologic Basis of Disease. Philadelphia: W.B Saunders Company. 0-7216-7335-X.
- ^ Bochner BS, Sterbinsky SA, Bickel CA, Werfel S, Wein M, Newman W. (Jan 15, 1994). "Differences between human eosinophils and neutrophils in the function and expression of sialic acid-containing counterligands for E-selectin". J Immunol. 152 (2): 774-82. PMID 7506734.
- ^ Wein, M (1995). "Comparison of human eosinophil and neutrophil ligands for P-selectin: ligands for P-selectin differ from those for E-selectin.". Am J Respir Cell Mol Biol. 12 (3): 315-9.
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| animal | Calnexin - Calreticulin - CD22 - CD33 - Galectin - Myelin-associated glycoprotein - N-Acetylglucosamine receptor - Selectin - Sialoadhesin |
| animal, calcium-dependent | Aggrecan - Asialoglycoprotein receptor - CD94 - Collectin (Mannan-binding lectin) - Mannose receptor - Versican |
| plant | Abrin - Ricin - Mitogens (Concanavalin A, Phytohaemagglutinin, Pokeweed mitogen) |
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| IgSF | N-CAM (Myelin protein zero) - ICAM (1, 4) - VCAM-1 - PE-CAM - L1-CAM |
| Cadherins | Desmoglein - T-cadherin |
| Selectins | E-selectin - L-selectin - P-selectin |
| Integrins | LFA-1 - Integrin alphaXbeta2 - Macrophage-1 antigen - VLA-4 - Glycoprotein IIb/IIIa (Note: integrins not always classified as CAMs) |
| Other | Carcinoembryonic antigen - CD22 - CD24 - CD44 - CD146 - CD164 |