an extracellular CHO binding domain (the lectin domain), which mediates binding to adjacent cells or to the extracellular matrix The P, L, and E selectins can bind a tetrasaccharide containing Sia-Gal- GalNAc-Fuc (called sialyl-Lewisx) on selectin ligand proteins and glycolipids.As mentioned for the selectins, adhesion molecules contain The selectins are also part of a class of molecules called adhesion molecules. In animals, lectins facilitate cell-cell interactions by forming multiple, but weak interactions between the protein and many sugars on the ligand to which it binds. Lectins and CHO ligands Lectin Family/Lectin Proteins that bind carbohydrate motifs are called lectins. The extracellular CHO binding domain is found in proteins in all organisms. These selectins are transmembrane proteins with an extracellular CHO binding domain, an EGF-like (epidermal growth factor like) domain, varying numbers of C (complement regulatory) domains, and a transmembrane domain. E-selectins: found on activated endothelial cells only after the cells have been induced to form them by certain immune hormones called cytokines releases by immune cells during an inflammatory response.In addition, their expression can be induced.
Activation occurs during the inflammatory response which can lead to the quick movement of pre-formed selectins stored within the cytoplasm to the membrane. P-selectins: found on activated platelets (which can aggregate to form a type of blood clot) and activated endothelial cells.L-selectins: found on leukocytes ("white" blood cells that are circulating immune cells).Proteins called selectins our found on cells that can pass through vessels and on endothelial cells. (Cancer cells do this as well as they escape the boundaries of the organ in which they developed and pass through the blood vessels and into new tissues in the process of of forming metastases.) Immune cells must first bind to endothelial cells (a monolayer of cells that line the lumen of the blood vessels) before they can pass through the vessel walls. The cells must often pass through the walls of capillaries as they hone in on a site of infection. This is illustrated well by studying the properties of circulating immune cells. \( \newcommand\)Ĭell surface carbohydrates present information-rich binding sites for other molecules and act as "receptors" for biological agents as diverse as viruses, bacteria, toxins, and other cells.
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