L-selectin

L-selectin is a type of adhesion molecule that is important in the immune system. It is a type of selectin, which are proteins that bind to carbohydrates on the surfaces of cells. L-selectin is found on the surface of white blood cells and helps them to move to sites of inflammation or injury.

Structure

L-selectin is a single-chain glycoprotein that is approximately 74-95 kDa in size. It is composed of a large, extracellular domain, a single transmembrane domain, and a short cytoplasmic tail. The extracellular domain contains a C-type lectin domain, an EGF-like domain, and two complement control protein modules.

Function

The primary function of L-selectin is to mediate the adhesion of circulating leukocytes to endothelial cells in the blood vessels. This is a crucial step in the immune response, as it allows the leukocytes to exit the bloodstream and enter the tissues where they can fight infection or repair damage. L-selectin binds to specific carbohydrate structures on the endothelial cells, which triggers a process known as rolling adhesion. This is a type of weak, transient adhesion that allows the leukocytes to roll along the inner surface of the blood vessel until they reach the site of inflammation or injury.

Clinical significance

Alterations in L-selectin function or expression can have significant clinical implications. For example, elevated levels of soluble L-selectin have been associated with various inflammatory conditions, including rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease. In addition, L-selectin has been implicated in the pathogenesis of certain types of cancer, as it may facilitate the metastasis of cancer cells to distant sites in the body.

See also

• Selectin
• Adhesion molecule
• Leukocyte
• Endothelial cell